Research Article Cite This: ACS Appl Mater Interfaces 2018, 10, 38506−38516 www.acsami.org Facile and Versatile Modification of Cotton Fibers for Persistent Antibacterial Activity and Enhanced Hygroscopicity Qiuquan Cai,† Shuliang Yang,‡ Chao Zhang,† Zimeng Li,‡ Xiaodong Li,*,‡ Zhiquan Shen,† and Weipu Zhu*,†,§ Downloaded via INST FOR SCIENTIFIC INFORMATION on February 19, 2021 at 12:49:11 (UTC) See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles † MOE Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and Engineering, Zhejiang University, Hangzhou 310027, People’s Republic of China ‡ Department of Oral and Maxillofacial Surgery, Affiliated Stomatology Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, China § Key Laboratory of Adsorption and Separation Materials & Technologies of Zhejiang Province, Hangzhou 310027, China S Supporting Information * ABSTRACT: Natural fibers with functionalities have attracted considerable attention However, developing facile and versatile strategies to modify natural fibers is still a challenge In this study, cotton fibers, the most widely used natural fibers, were partially oxidized by sodium periodate in aqueous solution, to give oxidized cotton fibers containing multiple aldehyde groups on their surface Then poly(hexamethylene guanidine) was chemically grafted onto the oxidized cotton fibers forming Schiff bases between the terminal amines of poly(hexamethylene guanidine) and the aldehyde groups of oxidized cotton fibers Finally, carbon−nitrogen double bonds were reduced by sodium cyanoborohydride, to bound poly(hexamethylene guanidine) covalently to the surface of cotton fibers These functionalized fibers show strong and persistent antibacterial activity: complete inhibition against Escherichia coli and Staphylococcus aureus was maintained even after 1000 consecutive washing in distilled water On the other hand, cotton fibers with only physically adsorbed poly(hexamethylene guanidine) lost their antibacterial activity entirely after a few washes According to Cell Counting Kit-8 assay and hemolytic analysis, toxicity did not significantly increase after chemical modification Attributing to the hydrophilicity of poly(hexamethylene guanidine) coatings, the modified cotton fibers were also more hygroscopic compared to untreated cotton fibers, which can improve the comfort of the fabrics made of modified cotton fibers This study provides a facile and versatile strategy to prepare modified polysaccharide natural fibers with durable antibacterial activity, biosecurity, and comfortable touch KEYWORDS: antibacterial, biocompatibility, cotton fiber, hygroscopicity, PHMG ■ after long-term use because of the limited loading content.24,25 Hence, long-lasting antibacterial CF may play an important role in improving antibacterial efficiency, preventing infections, and protecting human health Cationic polymers containing cationic groups and hydrophobic groups are another kind of important synthetic biocides.26−33 Cationic polymers can be adsorbed onto the anionic membrane of bacteria by charge interactions Then their hydrophobic groups insert into the membrane and disrupt it, which leads to the death of bacteria.34 CF with covalently bonded cationic polymers can kill bacteria through a contact mechanism,35 which is quite different from leachable biocides, resulting in CF with persistent antibacterial activity.36 Surface-initiated living/controlled radical polymerization of INTRODUCTION Cotton is one of the most important natural resources to produce fabrics for clothing and other textile materials The adhesion and growth of bacteria in cotton fabrics not only lead to the performance degradation of cotton fabrics, but also result in bacterial infection in human beings.1 Therefore, antibacterial finishing of cotton fibers (CF) has created great interest in laboratory research and industrial applications.2 Silver nanoparticles (Ag NPs) with high specific surface area, strong antibacterial activity, and low cost can easily be prepared from water-soluble silver salts, which can in situ deposit on the surface of CF, resulting in antibacterial CF.3−10 Moreover, many other metal NPs, such as copper,11−14 zinc,15−20 and titanium,21−23 have also been employed as antibacterial agents to modify CF These inorganic NPs serve as leachable biocides that can be released from CF to kill the surrounding bacteria However, CF coated with leachable biocides are usually lacking in durable antibacterial activity © 2018 American Chemical Society Received: August 30, 2018 Accepted: October 11, 2018 Published: October 11, 2018 38506 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces round-bottom flask CF (2 g) was then charged into the flask under continuous magnetic stirring and nitrogen gas flow The oxidation of CF was carried out at 35 °C in dark conditions for a preset oxidation time Finally, the resultant OCF was ultrasonically washed with ethanol and deionized water three times sequentially and dried at 40 °C under vacuum for 12 h The oxidation degree of OCF, referring to the percentage of cellulose units that have been oxidized, was further determined by titration.47 Typically, 100 mL hydroxylamine hydrochloride methanol solution (20 mg/mL) and g of OCF were charged into a 250 mL conical flask followed by adding a drop of thymol blue ethanol solution (0.1%) as an indicator The mixture was stirred for 10 until it turned pink It was then titrated with standard sodium hydroxide solution (0.03 mol/L) until the solution turned yellow and did not fade within 30 s The degree of oxidation (%) of OCF is calculated by cationic vinyl monomers from CF has been reported to prepare antibacterial CF with stable polycation coating.37 Nevertheless, the potential application of this method is hindered by the tedious reaction steps and critical polymerization conditions Therefore, chemically grafting ready-made cationic polymers onto CF seems to be an efficient strategy for preparing antibacterial CF, assuming the route can be simplified Poly(hexamethylene guanidine) (PHMG) is an environment-friendly cationic polymer with strong antibacterial activity and a low toxicity to human beings,38−42 which has been widely used for water treatment,43 wound disinfection,44,45 food packing,46 and so on However, commercially available linear PHMG with amine end groups cannot react with the glucose units of cotton directly In order to solve this problem, Guan et al synthesized a PHMG derivative with two terminal epoxy groups by the polycondensation of PHMG with poly(propylene glycol)diglycidyl ether , which then can be chemically coated onto CF through hydroxyl−epoxy reaction under alkaline conditions.1 In this study, we demonstrate a facile and versatile strategy to covalently graft commercially available PHMG to CF directly without any additional linker First, multiple aldehyde functionalities are introduced to the surface of CF by oxidization, which can react with the terminal amines of PHMG in a high yield In the next step, the unstable Schiff base bonds between CF and PHMG were reduced into carbon−nitrogen sigma bonds, greatly improving the stability of PHMG coatings We further investigated the biocompatibility, antibacterial activity, moisture absorption, and retention capacity of PHMG-coated CF ■ Oxidation degree (%) = M × (V2 − V1) × C × 10−3 × 100 m (1) where V2 and V1 (mL) are the volumes of the standard sodium hydroxide solution for the test groups and control groups, respectively C (mol/L) is the concentration of the standard sodium solution, m (g) is the weight of OCF, and M (g/mol) is the molecular weight of the cellulose unit (162 g/mol) The final value of oxidation degree is an average of three parallel tests Preparation of PHMG-Grafted CF (CF-g-PHMG) In a typical experiment, g of PHMG (1.43 mmol) was charged into a 100 mL round-bottom flask with 30 mL deionized water to form a 100 mg/ mL aqueous solution of PHMG under continuous magnetic stirring Thereafter, g of OCF was added into the solution Triethylamine (TEA; 0.1 mL) was added as the catalyst The aldehyde groups of OCF were reacted with the terminal amines of PHMG to give PHMG-grafted OCF (OCF-g-PHMG) through Schiff reaction under room temperature for h Afterward, 0.5 g of NaCNBH3 (7.96 mmol) was added to the mixture for another h of reaction to reduce the carbon−nitrogen double bonds into stable sigma bonds Finally, the sample was ultrasonically washed with ethanol and deionized water three times sequentially to remove the TEA, unreacted PHMG, and NaCNBH3 It was dried at 40 °C in a vacuum oven to give CF-gPHMG Conversion efficiency of aldehyde groups into Schiff base was determined by the hydroxylamine hydrochloride titration mentioned above The reaction efficiency of CHO (%) is calculated as follows EXPERIMENTAL SECTION Materials CF (145.8 dtex of single yarn × 19 strands) was purchased from Suzhou Shenchen Textiles Co Ltd., China PHMG hydrochloride (Mn = 2100 g/mol, 99%) was obtained from Hubei Xinyuan Shun Pharmaceutical Chemical Co Ltd., China Sodium periodate (NaIO4, 99%, Aladdin, China), hydroxylamine hydrochloride (NH OH·HCl, 99%, Aladdin, China), and sodium cyanoborohydride (NaCNBH3, 99%, Alfa Aesar, USA) were used as received Luria−Bertani (LB) broth, LB agar, and R2A agar were purchased from Huankai Microbial Sci & Tech Co Ltd., China Alpha-minimum essential medium (α-MEM) and fetal bovine serum (FBS) were purchased from Invitrogen Co., USA The Cell Counting Kit-8 was purchased from Sigma-Aldrich Chemicals, United States Other reagents and solvents were of analytical grade and used as received Characterization All samples used for surface characterizations were dried at 40 °C in vacuum prior to analysis The surface morphologies of CF, oxidized CF (OCF), CF-g-PHMG, and PHMG@CF were examined by scanning electron microscope (SEM, SU-8010, Japan) after coating with platinum X-ray photoelectron spectroscopy (XPS, VG ESCALAB MARK II, UK) and energy dispersive X-ray (EDX) in the SEM system were used to analyze the surface element composition of the samples Fourier transform infrared attenuated total reflectance (FT-IR ATR) spectrophotometer (Bruker Co TENSOR II, Germany) was used to record the surface information Fluorescence images were collected by a fluorescence microscopy (Nikon Eclipse 80i, Japan) Tensile tests were carried out by Instron-3343 tester with a stretching speed of 10 mm/min at room temperature The fiber samples (original gauge length: 50 mm) were tested to determine the breaking tenacity (N/ tex) and elongation at break (%) 1H NMR spectroscopy was carried out by using a Bruker Avance-400 NMR spectrometer (400 MHz) Preparation of OCF 0.2 g of NaIO4 (0.94 mmol) was dissolved in 100 mL deionized water and transferred into a 250 mL three-neck Reaction efficiency of CHO (%) = A1 − A × 100 A1 (2) where A1 and A2 (mol/g) are the aldehyde contents of CF after oxidation and grafting, respectively The grafting density is defined as the percentage of the grafted cellulose units with respect to the total cellulose units of CF, which can be calculated from the following expression Grafting density (%) = reaction efficiency of CHO × oxidation degree × 100 (3) Preparation of CF with Physical Adsorption of PHMG (PHMG@CF) As a comparison, g of CF was soaked in 100 mg/mL PHMG aqueous solution (30 mL) for h Then, the sample was sequentially washed with ethanol and deionized water in an ultrasonic bath three times for 30 and dried at 40 °C under vacuum to give PHMG@CF Antibacterial Assays The antibacterial activities of CF, OCF, CF-g-PHMG, and PHMG@CF were evaluated by measuring zones of inhibition, optical density at 600 nm [optical density (OD)600], as well as drop-plate methods The Escherichia coli and Staphylococcus aureus were used as model microorganisms The bacterial suspensions contained from 106 to 107 colony-forming units (CFU)/mL for all tests For the inhibition zone method, LB agar medium was prepared and autoclaved at 121 °C for sterilization before use Then, 10 mL LB agar medium (as a liquid when cooled to 45 °C) was mixed with an E 38507 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Scheme Preparation of CF-g-PHMG coli or S aureus broth to a concentration of 106 CFU/mL and cast on polystyrene Petri dishes Finally, each sterilized fiber sample with a coiled shape (0.5 g, mm in diameter) was placed on the dish These fiber samples were incubated at 37 °C for 24 h before observation The zones of inhibition were recorded by a digital camera The OD600 measurement and drop-plate counting method were both adopted to assess the antibacterial activities of these fibers in liquid media For the OD600 measurement, 0.5 g of CF-g-PHMG was soaked in a 6-well plate containing 10 mL of E coli or S aureus LB broth (106 CFU/mL) for each well and incubated at 37 °C At different intervals (0, 3, 6, 9, 12, 24 h), 100 μL of the cultured bacterial suspension was transferred into a 96-well plate to measure the OD600 by a microplate spectrophotometer (SpectraMax i3, USA) The inhibition ratio (%) for bacteria is calculated by ij ODsample − ODnegative yzz zz × 100 Inhibition ratio (%) = jjjj1 − j ODpositive − ODblank zz k { broth was added into a 96-well plate and cultured in a humidified atmosphere of 5% CO2 at 37 °C for 24 h The extract was charged into the plate and incubated for another 24 h After incubation, the medium was removed carefully and replaced by the CCK-8 reagent and cultured for another h Cell viability was determined by the OD at 450 nm, which was measured by a microplate spectrophotometer The expression for cell viability (%) is as follows Cell viability (%) = ODnegative − ODblank × 100 (6) where ODsample, ODnegative, and ODblank are the absorbances of extract with cells, extract only, and blank, respectively Data are presented as the average ± SD (n = 5) Hemolysis assay was conducted to evaluate the blood compatibility of CF, CF-g-PHMG, and PHMG@CF Human red blood cells (hRBCs) were obtained by venous puncture from healthy nonsmoking volunteers using standard blood-drawing procedures (normal blood flow and no pressure) The present study was approved by the Ethics Committee of Zhejiang University Additionally, an informed consent was obtained from each healthy donor prior to obtaining blood The fresh hRBCs were washed with phosphate buffer saline (PBS), centrifuged three times, and diluted to 4% in volume with PBS Diluted hRBC suspension (2 mL) was charged into a 24-well plate containing 0.2 g of sterilized fiber samples The hRBC suspension with 0.9% saline and 0.1% Triton X100 served as the negative and positive groups, respectively The plates were cultured at 37 °C for h At last, the hRBC suspension was centrifuged under 3000 rpm and °C for The suspension (100 μL) after centrifugation was transferred to a 96-well plate The OD values at 576 nm were detected by a microplate spectrophotometer The hemolysis (%) is calculated as follows (4) where ODsample, ODnegative, ODpositive, and ODblank are the absorbances of sample with bacteria, sample only, bacteria only, and blank, respectively Data are presented as the average ± SD (n = 5) For the drop-plate method, 0.5 g of CF-g-PHMG was soaked into a 6-well plate containing 10 mL E coli or S aureus LB broth (106 CFU/ mL) for each well and incubated at 37 °C At different intervals (0, 3, 6, 9, 12, 24 h), 100 μL of the cultured bacterial suspension was transferred from each well and diluted to 10-fold serial dilutions The optimal ranges of dilution times were 102 to 105 at h, 104 to 107 at h, and 105 to 108 after h (6, 9, 12, 24 h), respectively 100 μL of each serial dilution was pulled up and expelled 10 μL drops with each push of the pipette onto one quadrant of an R2A agar plate that had been divided into fourths and labeled for that particular dilution of the sample Five drops of 10 μL were placed on the plated for each dilution Then, the drops were let to soak into the media before turning the plates for incubation at 37 °C overnight The dilution containing 3−30 colonies per 10 μL was counted after the colonies had developed Viable bacteria counts are expressed as CFU/mL according to the following formula48,49 Viable bacteria count (CFU/mL) = ODsample − ODblank Hemolysis (%) = ODsample − ODnegative ODpositive − ODnegative × 100 (7) where ODsample, ODnegative, and ODpositive are the absorbances of the hRBCs suspension with fiber samples, 0.9% saline, and 0.1% Triton X100, respectively Data are presented as the average ± SD (n = 5) Moisture Absorption and Retention Measurements The fiber samples were fully dried under vacuum in the presence of P2O5 before use Then they were placed in two different desiccators, where the internal relative humidity (RH) was kept at 43 and 81% by saturated K2CO3 and (NH4)2SO4 aqueous solutions at room temperature, respectively.50 The mass variation was measured at regular intervals The moisture absorption (%) was calculated by the percentage of weight increase of dry sample average CFU × dilution Vp (5) where Vp is volume plated (0.01 mL) Data are presented as average ± SD (n = 5) Biocompatibility Evaluations Cytotoxicities of CF, OCF, and CF-g-PHMG in vitro were assessed by the Cell Counting Kit-8 (CCK-8) assay Three kinds of cells, mouse osteoblastic cells (MC3T3-E1), human breast adenocarcinoma cells (MCF-7), and human breast cancer cells (Bcap-37), were used as model cells First, an extract was obtained by impregnating 0.5 g of fiber sample into mL α-MEM, including 10% FBS at 37 °C for 24 h Then, the cell Moisture absorption (%) = W2 − W1 × 100 W1 (8) where W1 and W2 (g) are the sample weights before and after placing into the desiccator with a certain humidity The moisture retention 38508 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces capacity of the fibers was characterized by adding g of the fiber sample into a weighing bottle containing 0.1 g (10%) of deionized water After the sample was fully wetted in the weighing bottle, it was then placed into a desiccator filled with dry silica gels at room temperature.50 At regular intervals, the moisture retention (%) of the sample is calculated by the percentage of residual water of wet sample Moisture retention (%) = H2 × 100 H1 (9) where H1 and H2 (g) are the sample weights before and after placing into the desiccators The moisture absorption or retention over time (W(t)) can be described by a Fick’s equation,51 which for the case of one-dimensional diffusion, takes the following form: W (t ) = A + B eCt (10) where A, B, and C are constants relative to the fibers and determined from the nonlinear fitting of moisture absorption or retention data by mathematical tools Further expression of the change rate of moisture absorption or desorption is obtained from the derivative of moisture absorption or retention ■ dW = |BC eCt | dt (11) RESULTS AND DISCUSSION Preparation and Characterization of CF-g-PHMG The preparation routes of CF-g-PHMG are displayed in Scheme Sodium periodate was employed as a mild oxidant to partly convert the 2,3-vicinal hydroxyl groups of glucose units in the CF into dialdehyde groups.52 In order to determine the oxidation degree of hydroxyl groups, the amount of aldehyde groups generated was measured by hydroxylamine hydrochloride titration The oxidation degree of CF varied over the reaction process with oxidation time (Figure 1A) After h of oxidation, the oxidation degree quickly increased to the maximum (2.55%), indicating that the hydroxyl groups of CF were converted into aldehyde groups and reached a corresponding maximal aldehyde content (315 μmol/g) for OCF Interestingly, aldehyde content then decreased gradually with oxidation time, which can be explained with the partly dissolved dialdehyde cellulose because of chain scission.53 The OCF samples with various oxidation times were further grafted with PHMG via Schiff reaction to give OCF-g-PHMG The reaction efficiency of aldehyde groups (CHO) and global grafting density of CF versus the oxidation time were also measured by titration through the reaction of remaining CHO with hydroxylamine hydrochloride, as shown in Figure 1B OCF with the highest oxidation degree showed a highest reaction efficiency of aldehydes (32.6%), resulting in a highest grafting density of 1.66% Finally, the carbon−nitrogen double bonds and residual aldehyde groups of OCF-g-PHMG were reduced to stable carbon−nitrogen sigma bonds and hydroxyl groups The resultant CF-g-PHMG with highest grafting density was used for further studies According to the photograph of CF, OCF, CF-g-PHMG, and PHMG@CF (Figure S1), macroscopic appearances of these fibers did not significantly change after oxidizing, grafting, and soaking SEM was further used to characterize the surface morphologies of CF, OCF, CF-g-PHMG, and PHMG@CF (Figure 2) The surface of CF before grafting was uniform and smooth, whereas that of OCF became coarse after oxidation For CF-g-PHMG, a lot of filaments appeared on the surface, which can be ascribed to the grafted PHMG segments However, PHMG@CF still showed smooth surfaces similar to Figure The oxidation degree (A), reaction efficiency of CHO, and grafting density (B) of CF vs oxidation time Figure SEM images and corresponding EDX mappings of CF, OCF, CF-g-PHMG, and PHMG@CF untreated CF because the physically adsorbed PHMG on the fiber surfaces cannot be maintained after washing several times Distribution of surface elements was imaged by the EDX mapping based on the C 1s, O 1s, and N 1s photoelectrons The overall contents of C, O, and N on the fiber surface can be 38509 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Figure XPS spectra of CF, OCF, CF-g-PHMG, and PHMG@CF CF-g-PHMG, and PHMG@CF were dyed with an aqueous solution of fluorescein disodium salt (20 mg/mL) and washed to remove the free salt In Figure S4, as expected, only CF-gPHMG showed green fluorescence under an excitation wavelength of 490 nm Overall, chemical bonding of PHMG onto the CF makes the coating more stable than that by soaking, and will not be eluted in water Effects of chemical grafting of PHMG on the mechanical properties of fibers were investigated by tensile tests Figure S5 shows the stress−strain curves of CF, OCF, and CF-g-PHMG The strength unit of fibers used is specific stress, expressed as N/tex, which is defined as the applied force (N) divided by its linear density (tex) of a yarn or fiber.57 It was found in the stress−strain curves that the breaking tenacity (breaking specific stress) of CF-g-PHMG (0.229 N/tex) were close to those of CF (0.238 N/tex) and OCF (0.232 N/tex) However, compared with the untreated CF, the elongation at break of OCF was slightly declined, which can be attributed to the slight chain scission of cellulose structure after oxidation Grafting of PHMG onto CF did not significantly affect the elongation at the break of CF-g-PHMG These results indicate that CF-g-PHMG basically preserves the mechanical properties of the untreated CF Antibacterial Activity of CF-g-PHMG The zones of inhibition were first conducted to verify the contacting antibacterial activities of modified CF.58 Surprisingly, CF-gPHMG showed significant inhibition zones larger than their contact areas for both E coli and S aureus (Figure 4A,B), which cannot be explained by the contact-kill mechanism In order to further investigate the antibacterial mechanism of CFg-PHMG, 10 g of CF-g-PHMG was immersed in L deionized water After ultrasonic washing for 12 h, the extract was lyophilized The resultant trace solid was dissolved in DMSOd6 for 1H NMR measurement As shown in Figure S6, the signals of trace cellulose and PHMG were both detected in the spectrum.59 We concluded that the very slow degradation of the cellulose backbone of CF-g-PHMG results in the diffusion of cellulose fragment with PHMG, which leads to the counted from the EDX mapping (see Figure S2) Because the content of O element in these four samples remains constant according to the grafting mechanism, it can be used as a standard to distinguish the difference in the content of N element before and after grafting The relative contents of elements on PHMG@CF surface (58.5% C, 41.5% O, and 0% N) were basically the same as those on CF and OCF surfaces (for CF: 56.9% C, 43.1% O, and 0% N; for OCF: 56.3% C, 43.7% O, and 0% N), indicating that no PHMG existed on their surfaces However, the overall compositions of the surface element of CF-g-PHMG were 64.5% C, 31.7% O, and 3.8% N It was found by calculation that around 65% C and 100% O derived from the CF raw materials, whereas 35% C and 100% N accounted for the grafted PHMG The above results were further confirmed by the detection of XPS As displayed in Figure 3, the peaks at the binding energy of 284, 397, and 531 eV can be assigned to the C 1s, N 1s, and O 1s photoelectrons, respectively.54 There were only two peaks of C and O from the cellulose structure for CF After oxidation, the elemental compositions on the surface of OCF did not significantly change compared to that of CF However, the new peak of N element was detected for the CF-g-PHMG, demonstrating that the PHMG was successfully grafted onto the surfaces of CF In contrast, no peak of N element could be monitored from the XPS spectrum of PHMG@CF, indicating that the physically adsorbed PHMG had been entirely removed by washing More evidence of chemically grafting PHMG onto CF is provided by FT-IR ATR spectroscopy and fluorescence microscopy Figure S3 shows the FT-IR ATR spectra of CF, OCF, CF-g-PHMG, and PHMG@CF In the FT-IR ATR spectrum of CF-g-PHMG, a new characteristic peak of guanidine groups appeared at 1630 cm−1, which proved that PHMG was covalently bonded to the CF surface.55,56 However, no distinct difference between the spectra of untreated CF and PHMG@CF was observed Because the PHMG is a cationic polymer, it can electrostatically adsorb negatively charged fluorescein disodium salt, which can identify the presence of PHMG on the surface.49 CF, OCF, 38510 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Figure Inhibition zones of CF, OCF, CF-g-PHMG, and PHMG@ CF with E coli (A) and S aureus (B); OD600 values of CF, OCF, CFg-PHMG, and PHMG@CF with E coli (C) and S aureus (D) inhibition zones Thus, the antibacterial mechanism can be attributed to the combination of the contact inhibition and diffusion inhibition On the one hand, the negative bacteria membranes will be electrostatically attracted by the positive surfaces of CF-g-PHMG Then the guanidine groups of PHMG will disrupt the bacteria membranes, causing leakage of cytoplasmic fluid and eventually killing the bacteria.35,60−62 On the other hand, the trace amount of degraded cellulose with PHMG segments can kill bacteria that are free around the fibers, resulting in extensive inhibitions zones Nevertheless, without a cationic PHMG coating, CF, OCF, and PHMG@CF did not exhibit any inhibition activities against the two kinds of bacteria Although PHMG@CF can physically adsorb PHMG, it loses its antibacterial activity after several washing cycles Inhibition effects of CF-g-PHMG against E coli and S aureus were quantified by the OD600 method, as shown in Figure 4C,D As expected, CF-g-PHMG showed effective antibacterial activities against both E coli and S aureus, resulting in quite low OD600 values As summarized in Figure S7, the inhibition ratios of CF-g-PHMG against E coli after 12 and 24 h of incubation were 92.9 and 95.6%, respectively Meanwhile, those against S aureus after 12 and 24 h of incubation were 91.6 and 94.8%, respectively In contrast, the inhibition ratios of other samples without a PHMG coating (CF, OCF, and PHMG@CF) were no more than 7%, indicating that those fibers did not affect the growth of bacteria Because the OD600 method cannot distinguish dead bacteria and living bacteria, the drop-plate method was further adopted to count the living bacteria during the cultivation process As shown in Figure 5A,B, no living bacteria were found in the plates for CF-g-PHMG even in the very beginning All bacteria were killed after adding to the medium containing CF-gPHMG for a few minutes By contrast, CF, OCF, and PHMG@CF exhibited the same trends of bacteria growth, suggesting that these fibers not have any antibacterial capabilities These results can be easily observed from the living-bacteria growth curves in Figure 5C,D Consistent with the measurements of OD600 method, the bacteria growth could Figure Drop-plate photographs of CF, OCF, CF-g-PHMG, and PHMG@CF with E coli (A) and S aureus (B); drop-plate counting of CF, OCF, CF-g-PHMG, and PHMG@CF with E coli (C) and S aureus (D) not be suppressed during the whole cultivation process for CF, OCF, and PHMG@CF It was notable that living bacteria were counted to be CFU/mL for CF-g-PHMG, indicating absolute inhibition of bacteria compared with the samples without PHMG coatings, with bacteria counts ranging from 108 to 1010 CFU/mL after 24 h of incubation The morphological changes in the bacteria grown on the surfaces of these fibers were observed by SEM (Figure 6) The normal morphologies of living E coli and S aureus are rod shaped and spherical, respectively Without PHMG coatings, the bacteria on CF or OCF were numerous and structurally intact; that is, there are no apparent antibacterial activities for these fibers Although PHMG@CF was immersed with PHMG, the result showed that the bacteria can also grow normally on the surfaces after several cycles of washing As a comparison, few bacteria could be observed on the surfaces of CF-g-PHMG In addition, the walls of E coli or S aureus contacted with their surfaces were disrupted and deformed, as indicated by the white arrows in the images This suggests that these bacteria were killed by the coated cationic PHMG 38511 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces PHMG is fairly low (2.5−5 ppm);63 thus, a trace amount of degraded cellulose segments boned with PHMG is enough to kill the bacteria In addition, the inhibition ratios against E coli and S aureus did not significantly compromise with an increase in washing cycles from 10 (E coli 95.5% and S aureus 94.3%) to 1000 (E coli 90.3% and S aureus 90.6%), as shown in Figure 7C These results were reconfirmed by the drop-plate method (Figure 7D) It can be clearly observed that no bacteria grew on all of the plates for CF-g-PHMG (0 CFU/mL in the range from 101 to 104 times of dilutions), indicating that 100% antibacterial activities against E coli or S aureus were achieved even after 1000 consecutive washing cycles The reason for the long-lasting antibacterial activity of CF-g-PHMG is that the covalently bonded PHMG chains are reasonably stable Although a trace amount of PHMG was lost because of the slow degradation of cellulose during washing, enough PHMG grafts remained on the surface of CF even after 1000 washing cycles, demonstrating a durable antibacterial capability of CFg-PHMG Biocompatibility of CF-g-PHMG In vitro cell viability assays of CF-g-PHMG with MC3T3-E1, MCF-7, and Bcap-37 cells were carried out to evaluate the biocompatibility of the modified fibers As displayed in Figure 8, the viabilities of the Figure SEM morphologies of E coli and S aureus on the surface of CF, OCF, CF-g-PHMG, and PHMG@CF The lower images are the enlargements of the rectangle area in the upper ones In order to study the durability of antibacterial effects, CF-gPHMG was ultrasonically washed with deionized water for different times (100, 200, 400, 600, 800, 1000) After drying, the samples were further assessed by the zones of inhibition, OD600 measurement, and drop-plate methods The bacterial suspensions employed for the tests contained 106 CFU/mL The sizes of inhibition zones of CF-g-PHMG against E coli and S aureus did not attenuate even after 1000 washing cycles (Figure 7A,B) The minimal inhibitory concentration of Figure Cell viability of CF, OCF, and CF-g-PHMG by CCK-8 assays three kinds of cells did not significantly decrease after oxidation and PHMG grafting, indicating the low toxicity of antibacterial CF to living mammalian cells Unlike bacteria with negative charged membranes, the mammalian cell membranes usually present a lower net negative charge and have weak interactions with cations.64 It thus results in a low cytotoxicity of CF-gPHMG toward the mammalian cells, which can be further confirmed by the following hemolytic analysis (Figure S8) The hemolysis activity of CF-g-PHMG to hRBCs was less than 2%, which is similar to those of other samples without a PHMG coating (CF and PHMG@CF) Both cell viability assays and hemolytic analysis demonstrated an excellent biocompatibility of CF-g-PHMG Moisture Absorption and Retention of CF-g-PHMG The moisture absorption and retention capacities are critical to controlling the thermophysiological comfort of human body.65 Moisture absorption refers to the ability of fiber materials to absorb moisture from the humidified atmosphere The moisture absorption capacities of the fibers were determined at two different RH (43 and 81%) under room temperature, as shown in Figure 9A,C CF-g-PHMG exhibited enhanced moisture absorption than untreated CF, which can improve the comfort of cotton fabrics.65−69 Furthermore, the oxidation Figure Inhibition zones of CF-g-PHMG against E coli (A) and S aureus (B), as well as the inhibition ratios (C) and drop-plate photographs (D) of CF-g-PHMG after various washing frequencies 38512 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Figure Moisture absorption [(A,B) 43% RH; (C,D) 81% RH] and moisture retention (E,F) of CF, OCF, CF-g-PHMG, and PHMG@CF of CF and soaking treatment of CF with PHMG solutions did not significantly contribute to the increase in moisture absorption capacity The introduction of hydrophilic guanidine groups can account for the enhanced moisture absorption of CF-g-PHMG Furthermore, the rates of moisture absorption of the fibers were plotted from the derivatives of the fitting curves of moisture absorption (Figure 9B,D), which represents the change rates of moisture absorption per unit time Interestingly, although the equilibrium moisture absorption of CF-gPHMG was higher under high RH (81%) than that under low RH (43%), the initial rates of moisture absorption were close under both RH At high RH, it took a long time for the rates of moisture absorption of the fibers to reach their equilibrium As opposed to moisture absorption, the moisture retention capability is defined as the ability of fibers to retain their water contents in dry conditions Moisture retention of samples is presented in Figure 9E The CF-g-PHMG showed the highest level of moisture retention among these samples The balanced rate of moisture retention of CF-g-PHMG was kept at 2.6%, which can be ascribed to the hydration of the cationic PHMG The rate of moisture desorption was also obtained from the derivative of the fitting curve of moisture retention (Figure 9F) Compared with CF, OCF, and PHMG@CF, the initial rate of moisture desorption of CF-g-PHMG decreased by around 40%, suggesting that CF-g-PHMG has good moisture retention ability because of an enhanced interaction between water and fiber surfaces Enhanced moisture retention of CF-gPHMG also contributes to the improvement of resistance to bacteria adhesion and moisture permeability of clothes.69,70 Overall, improve bacteria bacterial ■ the enhanced hygroscopicity of CF-g-PHMG can the clothing comfort and promote resistance to adhesion with the combination of inherent antiactivities CONCLUSIONS We report a facile and versatile strategy to chemically graft PHMG onto CF directly via C−N sigma bonds The modified CF shows strong and long-lasting antibacterial activity against both Gram-positive and Gram-negative bacteria even after 1000 cycles of washing The antibacterial mechanism mainly comes from the inhibition of covalent PHMG coating upon contact Moreover, the very slow degradation of cellulose bonded with PHMG leads to additional diffusion inhibition The CF-g-PHMG also exhibited excellent biocompatibility based on CCK-8 and hemolytic assays Owing to the hydrophilicity of the PHMG coating, CF-g-PHMG possess enhanced moisture absorption and retention capacities compared with untreated CF, which can improve the comfort of cotton fabrics This strategy can also be used to chemically modify other natural fibers with glucose units Functionalized natural fibers, which are easy to prepare, have persistent antibacterial activity, excellent biocompatibility, and comfortable feel and have many potential applications in clothing and as medical gauze 38513 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces ■ (11) Yang, J.; Xu, H.; Zhang, L.; Zhong, Y.; Sui, X.; Mao, Z Lasting Superhydrophobicity and Antibacterial Activity of Cu Nanoparticles Immobilized on the Surface of Dopamine Modified Cotton Fabrics Surf Coat Technol 2017, 309, 149−154 (12) Suryaprabha, T.; Sethuraman, M G Fabrication of CopperBased Superhydrophobic Self-Cleaning Antibacterial Coating over Cotton Fabric Cellulose 2017, 24, 395−407 (13) Shankar, S.; Rhim, J.-W Facile Approach for Large-Scale Production of Metal and Metal Oxide Nanoparticles and Preparation of Antibacterial Cotton Pads Carbohydr Polym 2017, 163, 137−145 (14) Bajpai, S K.; Bajpai, M.; Sharma, L Copper Nanoparticles Loaded Alginate-Impregnated Cotton Fabric with Antibacterial Properties J Appl Polym Sci 2012, 126, E319−E326 (15) Borda d’ Á gua, R.; Branquinho, R.; Duarte, M P.; Maurício, E.; Fernando, A L.; Martins, R.; Fortunato, E Efficient Coverage of ZnO Nanoparticles on Cotton Fibres for Antibacterial Finishing Using a Rapid and Low Cost in Situ Synthesis New J Chem 2018, 42, 1052− 1060 (16) Sivakumar, P M.; Balaji, S.; Prabhawathi, V.; Neelakandan, R.; Manoharan, P T.; Doble, M Effective Antibacterial Adhesive Coating on Cotton Fabric Using ZnO Nanorods and Chalcone Carbohydr Polym 2010, 79, 717−723 (17) Perelshtein, I.; Ruderman, Y.; Perkas, N.; Traeger, K.; Tzanov, T.; Beddow, J.; Joyce, E.; Mason, T J.; Blanes, M.; Mollá, K.; Gedanken, A Enzymatic Pre-Treatment as a Means of Enhancing the Antibacterial Activity and Stability of ZnO Nanoparticles Sonochemically Coated on Cotton Fabrics J Mater Chem 2012, 22, 10736 (18) Dhandapani, P.; Siddarth, A S.; Kamalasekaran, S.; Maruthamuthu, S.; Rajagopal, G Bio-Approach: Ureolytic Bacteria Mediated Synthesis of ZnO Nanocrystals on Cotton Fabric and Evaluation of Their Antibacterial Properties Carbohydr Polym 2014, 103, 448−455 (19) Wang, C.; Lv, J.; Ren, Y.; Zhou, Q.; Chen, J.; Zhi, T.; Lu, Z.; Gao, D.; Ma, Z.; Jin, L Cotton Fabric with Plasma Pretreatment and ZnO/Carboxymethyl Chitosan Composite Finishing for Durable UV Resistance and Antibacterial Property Carbohydr Polym 2016, 138, 106−113 (20) Pandimurugan, R.; Thambidurai, S UV Protection and Antibacterial Properties of Seaweed Capped ZnO Nanoparticles Coated Cotton Fabrics Int J Biol Macromol 2017, 105, 788−795 (21) Karimi, L.; Yazdanshenas, M E.; Khajavi, R.; Rashidi, A.; Mirjalili, M Using Graphene/TiO2 Nanocomposite as a New Route for Preparation of Electroconductive, Self-Cleaning, Antibacterial and Antifungal Cotton Fabric without Toxicity Cellulose 2014, 21, 3813− 3827 (22) El-Naggar, M E.; Shaheen, T I.; Zaghloul, S.; El-Rafie, M H.; Hebeish, A Antibacterial Activities and UV Protection of the in Situ Synthesized Titanium Oxide Nanoparticles on Cotton Fabrics Ind Eng Chem Res 2016, 55, 2661−2668 (23) Mishra, A.; Butola, B S Deposition of Ag Doped TiO2 on Cotton Fabric for Wash Durable UV Protective and Antibacterial Properties at very Low Silver Concentration Cellulose 2017, 24, 3555−3571 (24) Opitakorn, A.; Rauytanapanit, M.; Waditee-Sirisattha, R.; Praneenararat, T Non-Leaching Antibacterial Cotton Fabrics Based on Lipidated Peptides RSC Adv 2017, 7, 34267−34275 (25) Saif, M J.; Zia, K M.; Rehman, F.-u.; Ahmad, M N.; Kiran, S.; Gulzar, T An Eco-Friendly, Permanent, and Non-Leaching Antimicrobial Coating on Cotton Fabrics J Text Inst 2015, 106, 907−911 (26) Yang, C.; Ding, X.; Ono, R J.; Lee, H.; Hsu, L Y.; Tong, Y W.; Hedrick, J.; Yang, Y Y Brush-Like Polycarbonates Containing Dopamine, Cations, and PEG Providing a Broad-Spectrum, Antibacterial, and Antifouling Surface via One-Step Coating Adv Mater 2014, 26, 7346−7351 (27) Carmona-Ribeiro, A.; de Melo Carrasco, L Cationic Antimicrobial Polymers and Their Assemblies Int J Mol Sci 2013, 14, 9906−9946 ASSOCIATED CONTENT S Supporting Information * The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.8b14986 ■ Photograph and detailed characterizations of CF, OCF, CF-g-PHMG, and PHMG@CF (PDF) AUTHOR INFORMATION Corresponding Authors *E-mail: cisarli@zju.edu.cn (X.L.) *E-mail: zhuwp@zju.edu.cn (W.Z.) ORCID Weipu Zhu: 0000-0002-6662-5543 Author Contributions Q.C and S.Y contributed equally to this work The article was written through contributions of all authors All authors have given approval to the final version of the manuscript Notes The authors declare no competing financial interest ■ ACKNOWLEDGMENTS W.Z acknowledges supports from National Natural Science Foundation of China (21674094 and 21875209), Zhejiang Provincial Natural Science Foundation of China (LR18B040001), and Fundamental Research Funds for the Central Universities (2017QNA4038) ■ REFERENCES (1) Li, Z.; Chen, J.; Cao, W.; Wei, D.; Zheng, A.; Guan, Y Permanent Antimicrobial Cotton Fabrics Obtained by Surface Treatment with Modified Guanidine Carbohydr Polym 2018, 180, 192−199 (2) Gao, Y.; Cranston, R Recent Advances in Antimicrobial Treatments of Textiles Text Res J 2008, 78, 60−72 (3) Xu, Q.; Xie, L.; Diao, H.; Li, F.; Zhang, Y.; Fu, F.; Liu, X Antibacterial Cotton Fabric with Enhanced Durability Prepared Using Silver Nanoparticles and Carboxymethyl Chitosan Carbohydr Polym 2017, 177, 187−193 (4) Kwak, W.-G.; Oh, M H.; Gong, M.-S Preparation of SilverCoated Cotton Fabrics Using Silver Carbamate via Thermal Reduction and Their Properties Carbohydr Polym 2015, 115, 317−324 (5) Emam, H E.; Saleh, N H.; Nagy, K S.; Zahran, M K Functionalization of Medical Cotton by Direct Incorporation of Silver Nanoparticles Int J Biol Macromol 2015, 78, 249−256 (6) Wu, M.; Ma, B.; Pan, T.; Chen, S.; Sun, J Silver-NanoparticleColored Cotton Fabrics with Tunable Colors and Durable Antibacterial and Self-Healing Superhydrophobic Properties Adv Funct Mater 2016, 26, 569−576 (7) Montazer, M.; Keshvari, A.; Kahali, P Tragacanth gum /nano silver hydrogel on cotton fabric: In-situ synthesis and antibacterial properties Carbohydr Polym 2016, 154, 257−266 (8) Emam, H E.; Zahran, M K Ag0 Nanoparticles Containing Cotton Fabric: Synthesis, Characterization, Color Data and Antibacterial Action Int J Biol Macromol 2015, 75, 106−114 (9) Zahran, M K.; Ahmed, H B.; El-Rafie, M H Surface modification of cotton fabrics for antibacterial application by coating with AgNPs-alginate composite Carbohydr Polym 2014, 108, 145− 152 (10) Li, J.-h.; Zhang, D.-b.; Ni, X.-x.; Zheng, H.; Zhang, Q.-q Excellent Hydrophilic and Anti-Bacterial Fouling PVDF Membrane Based on Ag Nanoparticle Self-Assembled PCBMA Polymer Brush Chin J Polym Sci 2017, 35, 809−822 38514 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Hydroxylamine Hydrochloride Method Pharm Res 1991, 08, 400− 402 (48) Herigstad, B.; Hamilton, M.; Heersink, J How to Optimize the Drop Plate Method for Enumerating Bacteria J Microbiol Methods 2001, 44, 121−129 (49) Zelver, N.; Hamilton, M.; Pitts, B.; Goeres, D.; Walker, D.; Sturman, P.; Heersink, J Measuring antimicrobial effects on biofilm bacteria: From laboratory to field Methods Enzymol 1999, 310, 608− 628 (50) Sun, L.; Du, Y.; Yang, J.; Shi, X.; Li, J.; Wang, X.; Kennedy, J F Conversion of Crystal Structure of the Chitin to Facilitate Preparation of a 6-Carboxychitin with Moisture Absorption-Retention Abilities Carbohydr Polym 2006, 66, 168−175 (51) Glaskova, T.; Aniskevich, A Moisture Absorption by Epoxy/ Montmorillonite Nanocomposite Compos Sci Technol 2009, 69, 2711−2715 (52) Bansal, M.; Chauhan, G S.; Kaushik, A.; Sharma, A Extraction and Functionalization of Bagasse Cellulose Nanofibres to Schiff-Base Based Antimicrobial Membranes Int J Biol Macromol 2016, 91, 887−894 (53) Kim, U.-J.; Wada, M.; Kuga, S Solubilization of Dialdehyde Cellulose by Hot Water Carbohydr Polym 2004, 56, 7−10 (54) Rojas, O J.; Ernstsson, M.; Neuman, R D.; Claesson, P M Xray Photoelectron Spectroscopy in the Study of Polyelectrolyte Adsorption on Mica and Cellulose J Phys Chem B 2000, 104, 10032−10042 (55) Zhang, Y W.; Chen, Y.; Zhao, J X Facile Fabrication of Antibacterial Core-Shell Nanoparticles Based on PHMG Oligomers and PAA Networks via Template Polymerization Aust J Chem 2014, 67, 142−150 (56) Chung, C.; Lee, M.; Choe, E Characterization of Cotton Fabric Scouring by FT-IR ATR Spectroscopy Carbohydr Polym 2004, 58, 417−420 (57) Koziol, K.; Vilatela, J.; Moisala, A.; Motta, M.; Cunniff, P.; Sennett, M.; Windle, A High-Performance Carbon Nanotube Fiber Science 2007, 318, 1892−1895 (58) Ruparelia, J P.; Chatterjee, A K.; Duttagupta, S P.; Mukherji, S Strain Specificity in Antimicrobial Activity of Silver and Copper Nanoparticles Acta Biomater 2008, 4, 707−716 (59) Kukharenko, O.; Bardeau, J.-F.; Zaets, I.; Ovcharenko, L.; Tarasyuk, O.; Porhyn, S.; Mischenko, I.; Vovk, A.; Rogalsky, S.; Kozyrovska, N Promising Low Cost Antimicrobial Composite Material Based on Bacterial Cellulose and Polyhexamethylene Guanidine Hydrochloride Eur Polym J 2014, 60, 247−254 (60) Xu, X.; Wang, Y.; Liao, S.; Wen, Z T.; Fan, Y Synthesis and Characterization of Antibacterial Dental Monomers and Composites J Biomed Mater Res., Part B 2012, 100, 1151−1162 (61) He, J.; Söderling, E.; Ö sterblad, M.; Vallittu, P K.; Lassila, L V J Synthesis of Methacrylate Monomers with Antibacterial Effects against S Mutans Molecules 2011, 16, 9755−9763 (62) Lu, G.; Wu, D.; Fu, R Studies on the Synthesis and Antibacterial Activities of Polymeric Quaternary Ammonium Salts from Dimethylaminoethyl Methacrylate React Funct Polym 2007, 67, 355−366 (63) Su, Y.; Zhi, Z.; Gao, Q.; Xie, M.; Yu, M.; Lei, B.; Li, P.; Ma, P X Autoclaving-Derived Surface Coating with in Vitro and in Vivo Antimicrobial and Antibiofilm Efficacies Adv Healthcare Mater 2017, 6, 1601173 (64) Yeaman, M R.; Yount, N Y Mechanisms of Antimicrobial Peptide Action and Resistance Pharmacol Rev 2003, 55, 27−55 (65) Tang, K.-p M.; Kan, C.-w.; Fan, J.-t.; Tso, S.-l Effect of Softener and Wetting Agent on Improving the Flammability, Comfort, and Mechanical Properties of Flame-Retardant Finished Cotton Fabric Cellulose 2017, 24, 2619−2634 (66) Su, C.-I.; Fang, J.-X.; Chen, X.-H.; Wu, W.-Y Moisture Absorption and Release of Profiled Polyester and Cotton Composite Knitted Fabrics Text Res J 2007, 77, 764−769 (67) Chen, S.; Yuan, L.; Li, Q.; Li, J.; Zhu, X.; Jiang, Y.; Sha, O.; Yang, X.; Xin, J H.; Wang, J.; Stadler, F J.; Huang, P Durable (28) Zhu, W.; Wang, Y.; Sun, S.; Zhang, Q.; Li, X.; Shen, Z Facile Synthesis and Characterization of Biodegradable Antimicrobial Poly(ester-carbonate) J Mater Chem 2012, 22, 11785 (29) Zhu, W.; Du, H.; Huang, Y.; Sun, S.; Xu, N.; Ni, H.; Cai, X.; Li, X.; Shen, Z Cationic Poly(ester-phosphoester)s: Facile Synthesis and Antibacterial Properties J Polym Sci., Part A: Polym Chem 2013, 51, 3667−3673 (30) Du, H.; Zha, G.; Gao, L.; Wang, H.; Li, X.; Shen, Z.; Zhu, W Fully biodegradable antibacterial hydrogels via thiol-ene ″click″ chemistry Polym Chem 2014, 5, 4002−4008 (31) Zheng, Z.; Xu, Q.; Guo, J.; Qin, J.; Mao, H.; Wang, B.; Yan, F Structure-Antibacterial Activity Relationships of Imidazolium-Type Ionic Liquid Monomers, Poly(ionic liquids) and Poly(ionic liquid) Membranes: Effect of Alkyl Chain Length and Cations ACS Appl Mater Interfaces 2016, 8, 12684−12692 (32) Thoma, L M.; Boles, B R.; Kuroda, K Cationic Methacrylate Polymers as Topical Antimicrobial Agents against Staphylococcus Aureus Nasal Colonization Biomacromolecules 2014, 15, 2933−2943 (33) Liu, S Q.; Yang, C.; Huang, Y.; Ding, X.; Li, Y.; Fan, W M.; Hedrick, J L.; Yang, Y.-Y Antimicrobial and Antifouling Hydrogels Formed in Situ from Polycarbonate and Poly(ethylene glycol) via Michael Addition Adv Mater 2012, 24, 6484−6489 (34) Yang, Y.; Cai, Z.; Huang, Z.; Tang, X.; Zhang, X Antimicrobial Cationic Polymers: from Structural Design to Functional Control Polym J 2018, 50, 33−44 (35) Kaur, R.; Liu, S Antibacterial surface design - Contact kill Prog Surf Sci 2016, 91, 136−153 (36) Lin, J.; Chen, X.; Chen, C.; Hu, J.; Zhou, C.; Cai, X.; Wang, W.; Zheng, C.; Zhang, P.; Cheng, J.; Guo, Z.; Liu, H Durably Antibacterial and Bacterially Antiadhesive Cotton Fabrics Coated by Cationic Fluorinated Polymers ACS Appl Mater Interfaces 2018, 10, 6124−6136 (37) Xing, T.; Liu, J.; Li, S Surface-Initiated Atom Transfer Radical Polymerization on Cotton Fabric in Water Aqueous Text Res J 2013, 83, 363−370 (38) Zhou, Z.; Wei, D.; Guan, Y.; Zheng, A.; Zhong, J.-J Extensive in Vitro Activity of Guanidine Hydrochloride Polymer Analogs against Antibiotics-Resistant Clinically Isolated Strains Mater Sci Eng., C 2011, 31, 1836−1843 (39) Wang, H.; Synatschke, C V.; Raup, A.; Jérôme, V.; Freitag, R.; Agarwal, S Oligomeric Dual Functional Antibacterial Polycaprolactone Polym Chem 2014, 5, 2453−2460 (40) Du, H.; Wang, Y.; Yao, X.; Luo, Q.; Zhu, W.; Li, X.; Shen, Z Injectable cationic hydrogels with high antibacterial activity and low toxicity Polym Chem 2016, 7, 5620−5624 (41) Li, S.; Wei, D.; Guan, Y.; Zheng, A Preparation and Characterization of a Permanently Antimicrobial Polymeric Material by Covalent Bonding Eur Polym J 2014, 51, 120−129 (42) Wei, D.; Ma, Q.; Guan, Y.; Hu, F.; Zheng, A.; Zhang, X.; Teng, Z.; Jiang, H Structural Characterization and Antibacterial Activity of Oligoguanidine (Polyhexamethylene Guanidine Hydrochloride) Mater Sci Eng., C 2009, 29, 1776−1780 (43) Sus, M.; Mitchenko, T Sorbents with Biocidal Properties for Disinfection of Water for Various Purposes Water Sci Technol.: Water Supply 2014, 14, 376−382 (44) Brill, F H H.; Gabriel, H Is Polyhexamethylene-Guanidine Hydrochloride (PHMGH) Sporicidal? A Critical Review J Med Microbiol 2015, 64, 307−308 (45) Zhang, C.; Ying, Z.; Luo, Q.; Du, H.; Wang, Y.; Zhang, K.; Yan, S.; Li, X.; Shen, Z.; Zhu, W Poly(hexamethylene guanidine)-Based Hydrogels with Long Lasting Antimicrobial Activity and Low Toxicity J Polym Sci., Part A: Polym Chem 2017, 55, 2027−2035 (46) Lerma, L L.; Benomar, N.; Muñoz, M d C C.; Gálvez, A.; Abriouel, H Correlation between Antibiotic and Biocide Resistance in Mesophilic and Psychrotrophic Pseudomonas Spp Isolated from Slaughterhouse Surfaces throughout Meat Chain Production Food Microbiol 2015, 51, 33−44 (47) Zhao, H.; Heindel, N D Determination of Degree of Substitution of Formyl Groups in Polyaldehyde Dextran by the 38515 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 Research Article ACS Applied Materials & Interfaces Antibacterial and Nonfouling Cotton Textiles with Enhanced Comfort via Zwitterionic Sulfopropylbetaine Coating Small 2016, 12, 3516−3521 (68) Deng, Y.-M.; Wang, S.-F.; Wang, S.-J Study on Antibacterial and Comfort Performances of Cotton Fabric Finished by ChitosanSilver for Intimate Apparel Fibers Polym 2016, 17, 1384−1390 (69) Wang, J.; Chen, Y.; An, J.; Xu, K.; Chen, T.; MüllerBuschbaum, P.; Zhong, Q Intelligent Textiles with Comfort Regulation and Inhibition of Bacterial Adhesion Realized by CrossLinking Poly(n-isopropylacrylamide-co-ethylene glycol methacrylate) to Cotton Fabrics ACS Appl Mater Interfaces 2017, 9, 13647−13656 (70) Okubayashi, S.; Griesser, U J.; Bechtold, T Moisture Sorption/ Desorption Behavior of Various Manmade Cellulosic Fibers J Appl Polym Sci 2005, 97, 1621−1625 38516 DOI: 10.1021/acsami.8b14986 ACS Appl Mater Interfaces 2018, 10, 38506−38516 ... m (1) where V2 and V1 (mL) are the volumes of the standard sodium hydroxide solution for the test groups and control groups, respectively C (mol/L) is the concentration of the standard sodium... ethanol and deionized water in an ultrasonic bath three times for 30 and dried at 40 °C under vacuum to give PHMG@CF Antibacterial Assays The antibacterial activities of CF, OCF, CF-g-PHMG, and PHMG@CF... of the pipette onto one quadrant of an R2A agar plate that had been divided into fourths and labeled for that particular dilution of the sample Five drops of 10 μL were placed on the plated for