Stimuli responsive PEGylated nano assemblies for cancer targeted drug delivery

A dissertation for the degree of doctor of philosophy Stimuli responsive PEGylated nano-assemblies for cancertargeted drug delivery Department of Molecular Science and Technology The Graduate School of Ajou University Dai Hai Nguyen Acknowledgement I wish to express in this part my gratitude to the scientists, technicians and other people who were directly and indirectly involved in this work, without the help of whom the findings of this thesis surely could not have been done First and foremost, I would like to extend immeasurable gratitude to Professor Ki Dong Park, for giving me the opportunity to my PhD thesis under his supervision I greatly appreciated his supervision for teaching, advising and supporting me throughout my work I am very grateful for his extreme patience and encouragement during the most stressful time when my results were not good He is a respectable mentor who has kindly supported me in the name of family It was an honor to work under his supervisor I am grateful to my thesis committee members, Professor Sung-Hwa Yoon, Professor Won-Hee Suh at Ajou University, Professor Ji Hoon Jeong at Sungkyunkwan University, Dr In Kwon Jung at Genoss Company for their numerous suggestions and helpful advice This is a good opportunity to express my gratitude to Professors at Ajou University whose teaching and advice helped me to complete my PhD coursework I would especially like to thank Dr Yoon Ki Joung who has supported for me for about three years He kindly and friendly guided me from laboratory studies to routine life in Korea I also have deep gratitude towards Dr Jin Woo Bae for being a great mentor His scientific comments are always useful in doing experiments, preparing presentation, and writing a scientific paper I would like to thank my Vietnamese Professors Thi Phuong Thoa Nguyen, Thi Kieu Xuan Huynh, and Huu Khanh Hung Nguyen for giving this opportunity to me, who taught me fundamental knowledge of chemistry at University of Science-HCMC I especially appreciate all supports of my past and current members in Biomaterial and Tissue Engineering Laboratory: Dr Kyoung Soo Jee, Dr Jin Woo Bae, Dr Dong Hyun Go, Dr Jung Seok Lee, Dr Kyung Min Park, Dr Se Jin Son, Dr Ngoc Quyen Tran, Dr Eugene Lih, Jong Hoon Choi, Yeo Jin Jun, In Kyu Hwang, Bae Young Kim, Ji Ho Heo, Seung Soo You, Ki Seong Ko, Ji Hye Oh, Seung Mee Hyun, Dong Hwan Oh, Joo Young Son, Yun Ki Lee, Ji Ho Kim, Min Yong Eom, Thi Thai Thanh Hoang, Thi Phuong Le I hope all members in BT Lab will obtain the outstanding achievement in your dream and get the happiness in their life I appreciate all help of my Vietnamese best friends in Korea, Minh Dung Truong, Van Thinh Nguyen, Dinh Chuong Pham, Ngoc Hoi Nguyen, Thanh Quy Nguyen, Hung Cuong Dinh, Thi Hiep Nguyen, Chan Khon Huynh, who helped in several experiments such as XRD, AFM, DLS, Confocal, FACS, cell culture, and animal studies Without them this thesis surely would not have been so multifaceted and prolific I also would like to be thankful to Korean friends in School of Engineering, Medicine School for your help and support me during my stay here Good luck to all of them Korean life could be some times stressful and tough, with all the competitiveness and perfectionism Luckily, I have had extensive care, support, and help from my family and friends, who shared with me many wonderful and unforgettable moments throughout my time here I would like to devote this thesis to them with my sincere gratitude I would like to thank many of my best friends, Hoang Duy Nguyen, Minh Triet Thieu, Hoang Chuong Nguyen, Nhat Nguyen Nguyen, Xuan Huong Ho… With them I shared the first journey to Korea, as well as the sadness of leaving our lovely home and country All this would not be possible without my loving immediate family For good or for bad, they are the ones who always stand behind me, and let me know that I am not alone Finally, deeply from my heart, I would like to thank my parents who believe and support me at all time My best regards to all, Dai Hai Nguyen Stimuli responsive PEGylated nano-assemblies for cancertargeted drug delivery Supervisor: Professor Ki Dong Park A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy June 2013 Department of Molecular Science and Technology The Graduate School of Ajou University Dai Hai Nguyen Abstract Cancer is one of the leading causes of death worldwide and chemotherapy is a major therapeutic approach for the treatment which may be used alone or combined with other forms of therapy However, conventional chemotherapy has the potential to harm healthy cells in addition to tumor cells Using targeted nanoparticles to deliver chemotherapeutic agents in cancer therapy offers many advantages to improve drug delivery and to overcome many problems associated with conventional chemotherapy This work covers the general areas of responsive nanocarriers and encompassed methods of fabricating nanocarrier-based drug delivery systems for controlled and targeted therapeutic application Chapter provides general information of cancer and cancer treatment strategies The recently cancer treatment based on nanocarrier were introduced In addition, the special features as well as requirements of nanoparticles for targeted drug delivery were presented This chapter describes overall objectives of this study with the current status of stimuli-responsive self-assembled nanocarriers for cancer chemotherapy In chapter 2, self-assembled nanogels based on reducible heparin-Pluronic copolymer was developed for intracellular protein delivery Heparin was conjugated with cystamine and the terminal hydroxyl groups of Pluronic were activated with the VS group, followed by coupling of VS groups of Pluronic with cystamine of heparin The chemical structure, heparin content and VS group content of the resulting product were determined by 1H i Chapter General introduction Overall conclusion Research activity aimed towards achieving specific and targeted delivery of anticancer agents has expanded tremendously in the last years or so with new avenues of directing drugs to tumors as well as new types of drugs In this dissertation, we presented how nanoparticles took advantage of these special features and how nanoparticles could act as a vehicle to specifically deliver cancer-fighting drugs to tumors We have developed three differ drug delivery systems using PEG and its block copolymer for targeted drug delivery The presence of PEG outer shell helps nanoscale carriers to bypass the RES clearance, thereby prolonging the circulation time in the blood stream Another advantage that could be taken from the stability of PEG-coated nanospheres is the possibility of attaching antibodies or a fragment of them to the surface of the particles, without destabilizing them, in order to achieve site-specific drug delivery, a major challenge for drug administration Ideally, these “magic missiles” would accumulate at the diseased tissue and locally liberate the necessary amount of drug The drugs can be released at the desired sites of actions by designing environment-sensitive linkers in side structure of nanoparticles where the linkers respond to the extra/intracellular microenvironment or external stimuli The design of these types of nanoparticles remains a very interesting research area Controlled release of drug at the site of action will enhance the efficacy and reduce the side effect of drug The combination of the use of stimuli-responsive material and targeting moieties will lead to nanoparticles which can be targeted to the side of action and which will deliver the drug These approach should provide the creative treatment methods have made it to the clinic and hopefully are well on their way to improving the length and quality of life for cancer patients However, it should be noted that extensive preclinical evaluations are required for these types of nanoparticles before they can be considered to use in patients Subjects which have to be evaluated are the pharmacokinetics of drug loaded/conjugated nanoparticles, effect of the surface-located targeting molecules on the opsonization process and blood circulation times as well as the efficacy and toxicity of the nanoparticles in particlular after repeated administration Mechanistic studies of the intracellular drug release from the nanoparticles are also required to further unravel the kinetics of intracellular nanoparticle destabilization and intracellular drug release Cancer and strategy treatment Cancer is one of the leading causes of death worldwide (13%) Each year 12.7 million people worldwide are diagnosed with cancer and there are 7.6 million deaths from the disease in 2008 (WHO).1 It is estimated that there are 24.6 million people alive who have received a diagnosis of cancer in the last five years By 2030, the number of new cancer cases is expected to rise to 21.4 million, with 13.15 million cancer deaths Cancer's total economic impact was estimated at $895 billion in 2008, or 1.5% of the world's gross domestic product This cost did not include direct medical costs, which could potentially double the total economic cost, according to Atlanta-based ACS.3 The cancer treatment during the twentieth century was based on surgery, radiation and chemotherapy Of these modalities, surgery is most effective at an early stage of disease progression However, most cancer operations carry a risk of: pain, infection, loss of organ function Surgery can also cause cancer cells to spread to different sites Radiation while destroying cancer cells also burns, scars, and damages healthy cells, tissues, and organs Initial treatment with chemotherapy and radiation will often reduce tumor size Radiation can cause cancer cells to mutate and become resistant and difficult to destroy.4 Chemotherapy is drug therapy that can kill these cells or stop them from multiplying However, it involves poisoning the rapidly growing cancer cells and also destroys rapidly growing healthy cells in the bone marrow, gastro-intestinal tract, etc., and can cause organ damage, like liver, kidney, heart and lungs, and so on Moreover, when the body has too much toxic burden from chemo the immune system is either 13 Petter RC, Salek JS, Sikorski CT, Kumaravel G, Lin FT 1990 J Am Chem Soc 112: 3860-8 14 GH J, J B, J M, RC D 1989 Vogel ’s text book of quantitative chemical analysis 15 Nguyen DH, Joung YK, Choi JH, Moon HT, Park KD 2011 Biomed Mater 6: 055004 16 Nguyen DH, Choi JH, Joung YK, Park KD 2011 Bioactive and Compatible Polymers 26: 17 Jagetia GC, Rao SK 2006 Evid Based Complement Alternat Med 3: 267-72 18 Lu Y, Zhao Y, Yu L, Dong L, Shi C, et al 2010 Adv Mater 22: 1407-11 19 Ma ZY, Guan YP, Liu XQ, Liu HZ 2005 Langmuir 21: 6987-94 20 Azagarsamy MA, Alge DL, Radhakrishnan SJ, Tibbitt MW, Anseth KS 2012 Biomacromolecules 13: 2219-24 118 NMR, FT-IR, toluidine blue assay and Ellman's method The HP conjugate showed a critical micelle concentration of approximately 129.35 mg L−1, a spherical shape and the mean diameter of 115.7 nm, which were measured by AFM and DLS The release test demonstrated that HP nanogels were rapidly degraded when treated with glutathione Cytotoxicity results showed a higher viability of drug-free HP nanogel than that of drugloaded one Cyclo(Arg–Gly–Asp–D-Phe–Cys) (cRGDfC) peptide was efficiently conjugated to VS groups of HP nanogels and exhibited higher cellular uptake than unmodified nanogels In chapter 3, stimuli–responsive Pluronic micelles is developed for targeting cancer chemotherapy In particularly, the role of crosslinking disulfide bond and hydrazone bond in arrangement of environmental stimuli including redox and pH were discussed Specifically, acrylic acid was grafted onto PPO blocks of Pluronic by dispersion/emulsion polymerization and used to introduce thiol groups as well as hydrazine groups DOX was conjugated to the hydrazone groups to achieve the pHtriggered release The micelles were crosslinked by the formation of disulfide bonds due to the presence of thiol groups on the polymer backbones The physico-chemical properties of the micelles were characterized In vitro release studies were performed to investigate pH-dependent release of DOX from the Pluronic micelles FA was conjugated to the Pluronic polymer for targeting cancer cell FA conjugated micelles were compared with the micelles without FA using confocal laser scanning microscopy (CLSM) and flow cytometry The Pluronic micelles functionalized with FA targeting ligand on the surface showed the enhanced cellular uptake In chapter 4, self-assembled magnetic nanoparticles ii (SAMNs) were fabricated from β-cyclodextrins functionalized superparamagnetic iron oxide (SPIO@CD), paclitaxel (PTX), adamantylamine-poly(ethylene glycol)-vinyl sulfone (ADA-PEG-VS), and c(RGDfC) peptide for integrated cancer cell-targeted drug delivery In this approach, PTX and ADA-PEG-VS enabled the host-guest inclusion with SPIO@CD to form PEG-ADA:SPIO@CD:PTX SAMNs Furthermore, cyclo(Arg-GlyAsp-d-Phe-Cys) (c(RGDfC)) peptide, a targeting ligand, could conjugate onto the VS groups of the PEG arms of SAMNs The architecture of SAMNs were characterized FTIR, TEM, and thermo gravimetric analysis (TGA), which confirmed that PEG, CD have been effectively functionalized on the surface of SPIO nanoparticles SAMNs were enabling to be controlled over the sizes, surface chemistry, payloads of supramolecular nanoparticle vector The sizes, drug entrapment efficiency (DEE), drug loading efficiency (DLE), and SIPO encapsulation of SAMNs could turn by changing its components In vitro PTX release profile from SAMNs was highly ADA response Cumulative releases of PTX from SAMNs were 44.1% and 9.6% with and without ADA treatment after 120 h Most importantly, the analyses of vibration sample magnetometer (VSM) verified that the magnetic property of SAMNs was increased under the external magnetic field c(RGDfC)-conjugated SPIO nanocarriers exhibited a higher level of cellular uptake than unmodified ones in vitro according to flow cytometry and confocal laser scanning microscopy (CLSM) iii Table of Contents Abstract i Table of Contents iv List of Figures viii List of Tables xv Chapter General introduction 1 Cancer and strategy treatment .2 Nanocarrier strategies in cancer chemotherapy Self-assembled nanocarrier for drug delivery .6 PEGylated nanocarriers for systemic deliver Targeted drug delivery systems for cancer therapy 13 5.1 Passive targeting strategies and recent developments 15 5.2 Active targeting strategies and stimuli-triggered ligand presentation 16 Stimuli-response for controlled drug delivery 18 6.1 Concepts for designing stimuli-responsive nanoparticles 18 6.2 Previous studies of stimuli-response for controlled drug delivery 26 Overall objectives .28 References 30 iv Chapter Self-assembled nanogels based on reducible heparin-Pluronic copolymer for targeted protein delivery .35 Introduction 36 Materials and methods 40 2.1 Materials 40 2.2 Synthesis of copolymers and preparation of drug loaded nanogels 40 2.3 Polymer characterizations 44 2.4 In vitro release test .47 2.5 Cytotoxicity assay 47 2.6 Intracellular uptake study 47 2.7 Statistical analysis .48 Results and Discussion .50 3.1 Characterization of polymers and nanogels .50 3.2 CMC and size distribution of nanogels 51 3.3 In vitro release profiles of RNase A and heparin .55 3.4 Cytotoxicity of RNase A-loaded nanogels 55 3.5 Cellular uptake of HP−RGD nanogels .58 Conclusions 61 References 62 Chapter pH- and redox-stimuli sensitive Pluronic micelle for targeted v doxorubicin delivery .65 Introduction .66 Materials and methods 70 2.1 Materials 70 2.2 Synthesis of copolymers and preparation of micelles 70 2.3 Micelle characterizations 73 2.4 In vitro DOX release 73 2.5 Cytotoxicity assay 74 2.6 In vitro intracellular uptake study 74 2.7 In vivo tumor growth inhibition study .75 Results and Discussion .77 3.1 Characterization of Pluronic conjugates 77 3.2 Analysis of intracellular uptake 80 3.3 In vitro cytotoxicity 84 3.4 In vivo tumor growth inhibition 88 Conclusions 90 References 91 Chapter Self-assembled magnetic nanoparticles based on host-guest inclusion for targeted paclitaxel delivery 95 Introduction 96 vi Materials and methods 98 2.1 Materials 98 2.2 Synthesis and preparation of SAMNs 99 2.3 Characterizations 103 2.4 In vitro PTX release test 106 2.5 In vitro intracellular uptake study 106 Results and Discussion .107 3.1 Characterization .107 3.2 In vitro release test 112 3.3 In vitro cellular uptake 113 Conclusions 116 References 117 vii List of Figures Figure 1.1 Overview of the clinically most relevant drug targeting strategies (A) Conventional chemotherapy (free drug) (B) passively targeted drug delivery system by virtue of the enhanced permeability and retention (EPR) effect (C) Active drug targeting to internalization-prone cell surface receptors (over)expressed by cancer cells generally intends to improve the cellular uptake of the nanomedicine systems (D) Active drug targeting to receptors (over)expressed by angiogenic endothelial cells aims to reduce blood supply to tumours (E) Stimuli-sensitive nanomedicines (F) Local drug delivery Figure 1.2 Example of self-assembled nanocarriers for targeted drug delivery: a Micelles, an aggregate of surfactant molecules dispersed in a liquid colloid where drugs are physically encapsulated in the inner core b Liposomes, a spherically arranged bilayer structure with drug loaded either in the inner aqueous phase or between the lipid bilayers c Oil/water emulsion, a mixture of liquids that are normally immiscible with drug loaded in the inner oil phase d Nanocapsules, a polymeric membrane which encapsulates an inner liquid core e Nanogels, a nanoparticle composed of a hydrogel f Core-shell particles, the location of nanocrystals at the core with the polymers on the outer layer viii Figure 1.3 (a) Nanocarriers (a1) are coated with opsonin proteins (a2) and associate with macrophages (a3) for transit to the liver (a4) Macrophages stationary in the liver, known as Kupffer cells, also participate in nanoparticle scavenging (b) Nanocarriers coated with PEG coating (b1) prevents this opsonization (b2), resulting in decreased liver accumulation (b3) and increased availability of the NP for imaging or therapy Figure 1.4 Conceptual representation of nanoparticle tumor-targeting modalities Passive targeting: Unlike that found in normal tissue, tumor vasculature is leaky owing to fenestrations and gaps between endothelial cells that result from abnormal angiogenesis NPs in circulation can passively extravasate through these gaps and enter the tumor interstitium Poor lymphatic drainage found in some tissues helps to retain particles in the tumor space Active targeting: Ligands (e.g antibodies, peptides, small molecules, etc.) targeted toward moieties overexpressed or uniquely present on the plasma membrane of tumor cells can be used to actively enhance NP accumulation at the tumor site and can also help to internalize particles into cells via endocytosis Figure 1.5 Dual and multi-stimuli responsive polymeric nanocarriers as emerging controlled drug release systems There are two kinds of stimuli, broadly defined, that can be engineered into delivery systems: internal stimuli ix (i.e., enzymatic reactions, changes in pH, redox, and temperature) and external stimuli (i.e., heat, light, magnetic and electrical fields) Figure 1.6 Schematic illustration of block copolymer assemblies which can respond to a range of stimuli characteristic of tumor tissues and intracellular microenvironments, promoting targeted delivery and controlled release of therapeutic drugs and imaging agents Figure 2.1 Schematic illustration showing the formation and redox-sensitive intracellular delivery of a protein-loaded HP nanogel Figure 2.2 Synthetic route of heparin−SS−Pluronic−VS conjugate Figure 2.3 H NMR (D2O) spectra of Pluronic−DVS (A), heparin−Cya (B), and heparin−Cya−Pluronic−VS (C) Figure 2.4 FT-IR spectra of cystamine dihydrochloride (a), heparin (b), Pluronic (c), heparin−Cya (d), Pluronic−DVS (e), heparin−Cya−Pluronic−VS (f) Figure 2.5 The determination of the CMC from the function of fluorescence intensity ratios of I441.5 to I337.5 versus the log concentration of heparinCya-Pluronic-VS (pH 7.4) Figure 2.6 The size distributions (DLS) of nanogels of heparin−Cya−Pluronic−VS (a) and RNase A-loaded heparin−Cya−Pluronic−VS (b) and the AFM x image of heparin−Cya−Pluronic−VS (c) Figure 2.7 Release profiles of heparin from heparin−Cya−Pluronic−VS nanogel (A) and RNase A from RNase A-loaded heparin−Cya−Pluronic−VS nanogel (B) Release studies were performed primarily in PBS media ((pH 7.4) and then treated with GSH at final concentration of mM at 37oC Experiments were performed three times and the data indicate mean ± standard deviation Figure 2.8 Cell viability of NIH3T3 cells incubated with heparin−Cya−Pluronic −cRGDfC (♦) and RNase A-loaded heparin−Cya−Pluronic−cRGDfC (■) nanogels for 48 h at 37 oC The cell viability was determined by MTT assay and plotted against the polymer concentration in DMEM at 37 oC Experiments were performed four times and significant differences between the treatment means and control values at respective times are indicated by * P < 0.05 Figure 2.9 Intracellular uptake of HP nanogels Confocal microscopic images of HeLa cells incubated with FITC-labeled heparin−Cya−Pluronic−VS and FITC-labeled heparin−Cya−Pluronic−cRGDfC nanogels, which were shown as blue (upper-left), green (upper-right) and merged (lower) fluorescence xi Figure 3.1 pH- and redox potential-responsive Pluronic micelles for cancer-targeted chemotherapy Figure 3.2 A synthetic route to FA-Pluronic-C/H-DOX (i) PNC, TEA, EDA, THF, (ii) AA, AIBN, APS, (iii) TEMPO, MeOH (iv) FA, EDC, NHS, MES buffer, (v) hydrazine, cystamine dihydrochloride, EDC, NHS, MES buffer, vi) DTT, borate buffer, (vii) DOX, TEA, DMSO Figure 3.3 Figure 3.4 Intensity ratio of pyrene as a function of FA-Pluronic-C/H concentration Figure 3.5 Time course changes in average diameter and size distribution of FA- H NMR spectra of AA-Pluronic-NH2 (i) and FA-Pluronic-C/H (ii) Pluronic-C/H-DOX micelles after DTT treatment (n = 4) Figure 3.6 In vitro release behaviors of DOX from micelles at different pH values DOX conjugated micelles (FA-Pluronic-C/H-DOX) at pH 7.4 (●) and pH 5.2 (■), DOX encapsulated micelles (FA-Pluronic-C/H/DOX) at pH 7.4 (○), or at pH 5.2 (□) (n = 4) Figure 3.7 Confocal microscopic images (a-f) of HeLa cells treated with various DOX formulations at a concentration equivalent to μg/mL of DOX Pluronic-C/H-DOX (a, b), FA-Pluronic-C/H-DOX (c, d), and free DOX (e, f) were incubated with HeLa cells for h (a, c, e) and h (b, d, f) xii Flow cytometry histrogram (g) and fluorescence intensity (h) of various DOX formulations internalized into HeLa cells for 4h Figure 3.8 Dose-dependent cytotoxicity of (a) FA-Pluronic-C/H micelles and (b) FA-Pluronic-C/H-DOX against HeLa cells after 48 h incubation (n = 4) Free DOX (×), Pluronic-C/H-DOX (○), and FA-Pluronic-C/H-DOX (●) were incubated with cells for 48 h Figure 3.9 Tumor growth inhibition test and body weight change of s.c breast MCF7/ARD xenograft in female BALB/c mice (Mean ± standard error of the mean, n = 5) Mice were dosed i.v with saline (●), FA-Pluronic(SS) (■), free DOX(▲), FA/DOX-Pluronic(SS) (×) (DOX 4.0 mg/kg) by tail vein injection on days 0, 4, The corresponding nanoparticle dose was 27.9 mg micelles/kg (a) Tumor volume changes, (b) body weight changes, and (c) Photos were taken on day 21 of our in vivo study Figure 4.1 Schematic illustration for the fabrication of self-assembled magnetic nanoparticles (SAMNs) with targeted drug delivery and magnetic resonance imaging (MRI) contrast enhancement functions from βcyclodextrins functionalized superparamagnetic iron oxide (SPIO@CD), paclitaxel (PTX), adamantylamine-poly(ethylene glycol)-vinyl sulfone (ADA-PEG-VS), and cyclo(Arg-Gly-Asp-d-Phe-Cys) xiii (c(RGDfC)) peptide moieties Figure 4.2 Synthetic routes employed for the preparation of ADA-PEG-VS and DOPA-CD moieties Figure 4.3 Figure 4.4 FT-IR spectra of (a) bare Fe3O4 NPs; (b) DOPA-CD; (c) ADA-PEGVS, (d) SPIO@CD, (e) VS-PEG-ADA:SPIO@CD:PTX SAMNS Figure 4.5 The particles size distribution of SPIO, SPIO@CD, and VS-PEGADA:SPIO@CD:PTX by DLS (a, b, and c) and by TEM (d, e, and f) Figure 4.6 In vitro characterization: (A) Magnetization curve of SIPO (white) and SAMNs (black) at 298 oK measured by SQUID exhibiting magnetic saturation, (B) Photograph of magnetic separation of SAMNs by a magnet Figure 4.7 In vitro PTX release profiles in PBS (pH 7.4) with (●) and without (■) ADA from SAMNs Figure 4.8 Confocal microscopic images (A) and fluorescence intensity (B) of HeLa cells and c(RGDfC) pretreated HeLa celles incubated with c(RGDfC)PEG-ADA:SPIO@βCD:PTX SAMNs at 37 oC for h H NMR spectra of DOPA-CD (A) and ADA-PEG-VS (B) xiv List of Table Table 1.1 Selected examples of ligands used in active drug targeting xv [...]... a wide opportunity for functionalization and versatility which impact the physico-chemical properties of self-assembled systems Examples of self-assembled nanocarriers for targeted drug delivery are showed in Figure 1.2 7 a Micelles d Nanocapsules b Liposomes e Nanogels c Oil/water emulsion f Core-shell particles Figure 1.2 Example of self-assembled nanocarriers for targeted drug delivery: a Micelles,... the innovations of nanomedicine Cancer nanomedicines have the ability to improve the therapeutic index of drugs by preferential localization at target sites, lower distribution in healthy tissues, delivery of hydrophobic drugs and extended release rate Progress in the development of nanomedicines for targeted drug delivery has been reviewed by Moghimi and colleagues.14 Targeted delivery can be achieved... molecule-1, VCAM-1 17 6 Stimuli- response for controlled drug delivery 6.1 Concepts for designing stimuli- responsive nanocarriers Despite the fact that stability of encapsulation in a delivery carrier is necessary during circulation, drug delivery will only be effective if the drug is released once it reaches its intended target Releasing specific sites in the body simplifies drug administration procedures,... allows the uniform distribution of micelles and drug throughout the tumor tissue.41 6.2 Previous studies of stimuli- response for controlled drug delivery These stimuli- responsive polymeric nanocarriers have demonstrated improved drug release behavior and anti-tumor activity to varying degrees, depending on type of stimulus, rate of response, and exact spot of triggering drug release In an effort to further... relative to others The goal of a targeted drug delivery system is to prolong, localize, target and have a protected drug interaction with the diseased tissue The conventional drug delivery system is the absorption of the drug across a biological membrane, whereas the targeted release system is when the drug is released in a dosage form The clinically most relevant drug targeting strategies were summarized... of the carboxylic groups and release of the drug 7 Overall objectives A wide range of contents extending from carcinogenesis to current methodologies for targeted drug delivery are described in brief These all categories provide a promising way toward the design of nanocarriers for targeted drug delivery Recently, research on programmable self-assembly of nanosystems promises to bring a new paradigm... Active drug targeting to internalization-prone cell surface receptors (over)expressed by cancer cells generally intends to improve the cellular uptake of the nanomedicine systems (D) Active drug targeting to receptors (over)expressed by angiogenic endothelial cells aims to reduce blood supply to tumours (E) Stimuli- sensitive nanomedicines (F) Local drug delivery 4 2 Nanocarrier strategies in cancer. .. strategies in cancer chemotherapy The use of nanotechnology in medicine and more specifically drug delivery is set to spread rapidly Currently many substances are under investigation for drug delivery and more specifically for cancer therapy are used in the clinic Interestingly pharmaceutical sciences are using nanocarriers to reduce toxicity and side effects of drugs and up to recently did not realize... external stimuli (i.e., heat, light, magnetic and electrical fields) When drug delivery systems maintain a response interaction they necessarily require a stimuli- response to cleave the interaction The release of drug is triggered by the stimulus (Figure 1.5) 18 Figure 1.5 Dual and multi -stimuli responsive polymeric nanocarriers as emerging controlled drug release systems There are two kinds of stimuli, ... advantages to the targeted release system is the reduction in the frequency of the dosages taken by the patient, having a more uniform effect of the drug, reduction of drug side effects, and reduced fluctuation in circulating drug levels 3 Figure 1.1 Overview of the clinically most relevant drug targeting strategies (A) Conventional chemotherapy (free drug) (B) passively targeted drug delivery system