Chitosan is a biopolymer that is natural, biodegradable, and relatively low price. Chitosan has been attracting interest as a matrix of nanocomposites due to new properties for various applications. This study presents a comprehensive overview of common and recent advances using chitosan as a nanocomposite matrix
Carbohydrate Polymers 272 (2021) 118472 Contents lists available at ScienceDirect Carbohydrate Polymers journal homepage: www.elsevier.com/locate/carbpol Review Chitosan as a matrix of nanocomposites: A review on nanostructures, processes, properties, and applications Angelo Oliveira Silva, Ricardo Sousa Cunha, Dachamir Hotza, Ricardo Antonio Francisco Machado * Department of Chemical and Food Engineering (EQA), Federal University of Santa Catarina (UFSC), 88040-900 Florian´ opolis, SC, Brazil A R T I C L E I N F O A B S T R A C T Chemical compounds studied in this article: Chitosan (PubChem CID: 71853) Chitin (PubChem CID: 6857375) Polylactic acid (PubChem CID: 612) Poly (vinyl alcohol) (PubChem CID:11199) Poly (ethylene oxide) (PubChem CID: 174) Poly (ethylene glycol) (PubChem CID: 174) Iron Oxide (PubChem CID: 6432052) Silicon dioxide (PubChem CID: 24261) Halloysite (PubChem CID: 56841936) Zinc oxide (PubChem CID: 14806) Chitosan is a biopolymer that is natural, biodegradable, and relatively low price Chitosan has been attracting interest as a matrix of nanocomposites due to new properties for various applications This study presents a comprehensive overview of common and recent advances using chitosan as a nanocomposite matrix The focus is to present alternative processes to produce embedded or coated nanoparticles, and the shaping techniques that have been employed (3D printing, electrospinning), as well as the nanocomposites emerging applications in medicine, tissue engineering, wastewater treatment, corrosion inhibition, among others There are several re views about single chitosan material and derivatives for diverse applications However, there is not a study that focuses on chitosan as a nanocomposite matrix, explaining the possibility of nanomaterial additions, the inter action of the attached species, and the applications possibility following the techniques to combine chitosan with nanostructures Finally, future directions are presented for expanding the applications of chitosan nanocomposites Keywords: Chitosan nanocomposites Nanotechnology 3D printing Scaffolds Electrospinning Introduction Polysaccharides (starch, cellulose, chitin, hyaluronate…) are natural polymeric biomaterials commonly employed in many biotechnological fields The use of biopolymers in life science is increasing due to their advantages, such as high availability, biocompatibility, and biodegrad ability There is also the added advantage of being converted to a variety of chemically or enzymatically modified derivatives for specific end uses (Bakshi et al., 2020) One of the most versatile biomaterials is chitosan, which finds potential application in food and nutrition, pharmaceuti cals, biotechnology, material science, agriculture, and environmental protection (Harish Prashanth & Tharanathan, 2007) Due to its biocompatible nature, chitosan and its derivatives are used extensively in water and waste treatment, medicine, electrochemical fields (Riaz Rajoka et al., 2019) The versatile chitosan applications are related to the 3B properties: biocompatibility, biodegradability, and biomimetics (Bakhshayesh et al., 2019; Rizeq et al., 2019) Fig shows the increased interest in chitosan materials and nanocomposites in the last years With the advance of nanotechnological fields, organic and inorganic nanofillers have been tested to produce chitosan nanocomposites pre senting improved mechanical, chemical, thermal, and barrier properties (Jafari et al., 2016; Rodrigues et al., 2020) Despite all that effort, there is not a work in literature that systematically reviews the nanostructure possibilities, and the related shaping processes required for the desired application Therefore, this work intends to fill this gap and present the coming trends and challenges regarding chitosan as a matrix of nanocomposites This paper is organized into three main sections: chemical structure and synthesis of the chitosan matrix and specific nanofillers, the most common shaping routes that have been employed, and the chemical and biotechnological properties related to applications of chitosan nanocomposites * Corresponding author E-mail address: ricardo.machado@ufsc.br (R.A.F Machado) https://doi.org/10.1016/j.carbpol.2021.118472 Received May 2021; Received in revised form 19 July 2021; Accepted 19 July 2021 Available online 22 July 2021 0144-8617/© 2021 Elsevier Ltd This article is made available under the Elsevier license (http://www.elsevier.com/open-access/userlicense/1.0/) A.O Silva et al 60k Carbohydrate Polymers 272 (2021) 118472 Chitosan 50k Crustacean Shell + Nanocomposites Magnification of the publications from 1934 to 1990 800 40k Chitosan 20k 500 400 300 Deproteinaze 200 100 NaOH 10k • Wash • Crush HCl 600 30k Demineralize 700 Publications Publications Chitosan + Matrix 0 -197 -198 -199 1934 1981 1971 Year Deacetylation 0 0 0 -202 -201 -199 -200 -198 -197 1991 1981 2001 2011 1971 1934 Chitin Year Chitosan Fig Number of publications with search entries: “chitosan” (green), “chi tosan” and “matrix” (yellow), “chitosan” and “matrix” and “nanocomposites” (red) Total number of publications: 62563 Search date: March 15, 2021 (Scopus) Fig Schematic overview of the main stages of production of chitin and chitosan source of biomass for the industrial production of chitin and chitosan The chemical structure of the crustacean shell is composed of protein, inorganic salts, chitin, and lipids The synthesis process of chitosan comes from a deacetylation reaction from chitin from the biomass source The chemical deacetylation reaction and the overview produc tion of chitosan are presented in Fig Typically, the manufacturing process follows these unit operations (Bakshi et al., 2020; Nasrollahza deh et al., 2021; Riaz Rajoka et al., 2019): (A) • The raw material shells are washed, crushed, and ground to smaller sizes with demineralization of some components, such as calcium carbonate, by chemical extraction with dilute hydrochloric acid with stirring at room temperature • After demineralization, deproteinization is performed by applying dilute aqueous sodium hydroxide solution Proteins can be recovered by lowering the pH to 4.0 and then drying the precipitates • An additional decolorization step may be incorporated to remove color In this step, chitin is extracted as the main input material for the production of chitosan • Chitosan is obtained by deacetylation from the chitin obtained, again in sodium hydroxide but in an environment without oxygen and sometimes by an enzymatic route The three key reaction parameters are alkali concentration, time, and temperature Those factors define the degree of deacetylation of the final material (B) Fig Chemical structures of (A) chitin (R1 = H) and its derivatives; (B) chi tosan (R1 = H, R2 = H, R3 = H) and their derivatives Adapted from Muanprasat and Chatsudthipong (2017) Chitosan nanocomposites: structure and microstructure Chitosan derivatives nanocomposites have earned high interest especially due to their distinctive physical and chemical properties (Fig 4) Amine (NH2) and hydroxyl (OH) surface groups promote the formation of several inter and intramolecular hydrogen bonds, which allows the embedding of nanoparticles used as a filler Chitosan has been increasingly investigated as an eco-friendly, low-cost, sustainable, and renewable nanocomposite 2.1 Chitin and chitosan: chemical structure and synthesis Chitin is a semi-crystalline homopolymer of β-(1 → 4)-linked Nacetyl-D-glucosamine It is the second most abundant natural biopolymer after cellulose (Bakshi et al., 2020) Chitosan, a partially deacetylated product of chitin, is a copolymer consisting of β-(1 → 4)-2acetamido-D-glucose and β-(1 → 4)-2-amino-D-glucose units, where the structures of both substances are presented in Fig (Muanprasat & Chatsudthipong, 2017) In Fig 2, radicals R1, R2, and R3 correspond to hydrogen in plain chitin and chitosan molecule Those surface groups led to the amino (NH2) and hydroxyl groups (OH), responsible for chitosan organic modifications with several possibilities producing polymeric derivatives of these compounds (Tharanathan & Kittur, 2003) Crab and shrimp shell exoskeleton wastes are the raw material 2.2 Chitosan as a nanocomposite matrix Besides the use of chitosan as a pure matrix biomaterial, with the advance of nanotechnology, chitosan can be coupled with several kinds of nanostructures, either embedded into the bulk material or deposited on the surface Biopolymers, such as chitosan, as pure single materials may exhibit A.O Silva et al Carbohydrate Polymers 272 (2021) 118472 Hydrophilic and Bioadhesive High cristalinity Insoluble in water and organic solvents Soluble in diluted acetic acid CHITOSAN NANOCOMPOSITES PROPERTIES Biocompatibility and Biodegradability Antimicrobial Chelating and Complexing Ionic conductivity Fig Typical physical and chemical properties of chitosan-based nanocomposites either as a filler dispersed inside the whole matrix, and/or as a coating at the material surface (Kankala et al., 2020) to outcome most of those structure drawbacks Several nanostructures of inorganic, organic, metallic, or semiconducting nature can be applied and dispersed as additives in chitosan, such as nanoparticles, nanosheets, nanorods, nanocapsules, nanowires, and nanofibers, as shown in Table This chapter focuses on the addition of single nanostructures to chitosan before shaping, and shows the materials that are commonly employed, as well as the chemical modifications or reactions required Other recent engineering processes for insertions of nanostructures within chitosan will be discussed further Table Some nanomaterials applied as additives (fillers, coatings) in chitosan nanocomposites Nanoadditive Nanostructure Filler/ coating Dimensions (particle size/length) in nm References Ag Nanoparticles/ nanowires Filler/ coating 20–100 Cellulose Nanocrystals Filler 100 Chitin Nanofibers Filler 50–500 Fe3O4 Nanoparticles Filler/ coating 9.5–124 Nanoclay Nanoparticles Filler 100 58.3–91.2 0.2 0.5–2.5 Not informed >50 Freeze-drying 50–150