Chitosan-Silica Composites

Introduction

Chitosan, a renewable natural polysaccharide, is considered the most widely distributed and utilized biomaterial after cellulose.[1] Chitosan is structurally similar to cellulose but, in addition to hydroxyl groups, contains acetylamine or free amino groups. For this reason, it has very different properties from cellulose. [2] Chitosan exhibits antibacterial properties thanks to groups composed of glucosamine and N-acetylglucosamine. [3] One of the main advantages of chitosan, along with its biodegradable, biocompatible and non-toxic properties, is its ease of processing into different forms such as particles, gels, microparticles, nanoparticles, nanofibers and scaffolds.[4] Besides its biological properties, chitosan is a material that attracts considerable attention due to its widespread use in the medical field (tissue engineering, drug delivery and wound healing applications, etc.), food industry (edible films, etc.) and textile sector (antibacterial coatings, etc.). [4, 5] Silica (SiO2) is widely used as a filler material in polymer and rubber industries. Silica materials have excellent physical and chemical properties such as water and thermal stability (up to 1500°C), good mechanical strength and non-toxicity. [6] Furthermore, the presence of silanol groups (Si-OH) on the surfaces of silica materials provides important support for the immobilization of a wide range of inorganic and organic groups.[7] The general properties and main application areas of chitosan and silica are presented in Figure 1.

Figure 1. a) General properties and application areas of chitosan and b) silica (modified based on reference [4])

Due to rapid developments in the medical, food and textile sectors, conventional single-component polymer or ceramic materials may be insufficient to meet the special requirements needed in these fields,[8] and therefore the development of new materials is necessary. To meet this demand, there is growing interest in the production of composites based on chitosan modified with inorganic materials that have improved properties. Mesoporous silica has potential for use in the production of chitosan-based composites due to its biocompatibility, high surface area, high pore volume and modifiable surface properties.[9] Additionally, chitosan-based composite materials are being produced with different silicas such as layered silica[10] and nanosilica.[11] Applications of Chitosan-Silica Composites Chitosan-silica based composites are promising materials with potential for use in various applications such as antimicrobial agents, water barrier compounds, anti-ultraviolet compounds, drug carrier systems and antimicrobial food packaging. A portion of the studies in the literature regarding various applications of these composites is summarized in Table 1. As potential "next-generation" membrane materials, chitosan-silica membranes are an intensively studied topic due to important properties such as adjustable porosity, controllable hydrophobicity and mechanical stability. There is increasing interest in their use particularly in the development of chemical sensors.[14, 24, 25] Sol-gel hybridization of silica xerogels with chitosan is considered an appropriate method for the production of new bioactive guided bone regeneration membranes. The use of chitosan as an organic phase enables the production of a flexible membrane from a rigid silica xerogel. Moreover, because of the drug-carrying potential of silica xerogel in composite membranes and being one of the components that form bone, it enhances the wound healing and bone-forming ability of the chitosan polymer. In a study conducted by Lee and colleagues,[12] it was found that chitosan-silica hybrid membranes provided higher new bone regeneration compared to chitosan membranes alone. Chitosan composite materials with nano-silica addition are used in bioengineering applications. The addition of silica nanoparticles to biopolymer-based tissue scaffolds results in an increase in the material's hardness and biomineralization. The mineralization ability of composites is significantly enhanced due to the presence of silanol groups (Si-OH), which play a major role in the formation of apatite, which is a building block of bone. Additionally, with the addition of silica, chitosan-based materials gain osteogenic activity. [4] Thanks to these properties that promote bone formation, it is thought that chitosan-nanosilica based materials can be used effectively in bone tissue engineering applications. Silica-chitosan based materials are used in various applications in the food industry. Glucose isomerase (GI), also known as D-xylose isomerase, is a very important water-soluble enzyme widely used in beverages and various products in the food industry. Work is being conducted on the encapsulation of glucose isomerase enzyme with silica/chitosan-based microspheres to improve the effectiveness and stability of this enzyme against environmental changes such as temperature and pH. As a result of a study conducted by Zhao and colleagues,[17] immobilized GI showed better pH, temperature, storage and operational stability compared to free GI. [17] Additionally, chitosan-nano silica has been evaluated in antimicrobial food packaging for extending the shelf life of Loquat (Eriobotrya japonica Lindl.), a subtropical fruit. It was found that chitosan-nano silica coatings reduced internal browning and weight loss in the fruit, and also preserved high levels of total soluble solids, titratable acidity, glucose and fructose. [18] Another application area where chitosan-silica based composites can be effectively used is the adsorption of various pollutants such as heavy metals and dyes from water. [19-21] Studies have shown that the adsorption capacity of composite adsorbents is higher than that of chitosan or silica adsorbents alone.[19, 21] The development of nanocarriers for targeted and controlled release of agrochemicals is one of the important topics that has attracted attention in recent years. Chitosan-silica based materials are carrier systems that can be used in the controlled release of pesticides used in the agricultural sector to kill insects, weeds, fungi and other organisms.[23]

General Evaluation

Although chitosan and silica are each used alone in many different applications, the combined use of these materials can yield composites with multifunctional properties. Due to their advanced properties, chitosan-silica composites have potential for use in many different fields, and research work related to these composites continues with growing interest. Chitosan-silica based composite materials show promise due to their superior properties. However, since the performance of different chitosan-silica materials in each specific application area varies depending on the material's properties and the application area, the properties of the resulting composite need to be optimized. In the literature studies conducted, it was found that in addition to composites consisting of chitosan and silica, a third component is being added (for example, silver, etc.) to develop new composites with different properties, and research aimed at using these composites in different application areas is rapidly continuing.

References

[1] M.A. Elgadir, M.S. Uddin, S. Ferdosh, A. Adam, A.J.K. Chowdhury, M.Z.I. Sarker, Impact of chitosan composites and chitosan nanoparticle composites on various drug delivery systems: A review, journal of food and drug analysis 23(4) (2015) 619-629.

[2] J.K. Hwang, H.H. Shin, Rheological properties of chitosan solutions, Korea-Australia Rheology Journal 12(3-4) (2000) 175-179.

[3] S. Hashemikia, N. Hemmatinejad, E. Ahmadi, M. Montazer, Antibacterial and anti-inflammatory drug delivery properties on cotton fabric using betamethasone-loaded mesoporous silica particles stabilized with chitosan and silicone softener, Drug delivery 23(8) (2016) 2946-2955.

[4] S. Deepthi, J. Venkatesan, S.-K. Kim, J.D. Bumgardner, R. Jayakumar, An overview of chitin or chitosan/nano ceramic composite scaffolds for bone tissue engineering, International journal of biological macromolecules 93 (2016) 1338-1353.

[5] Li Q, Dunn ET, Grandmaison EW. Applications and properties of chitosan. In: Goosen MFA, editor. Applications of chitin and chitosan. Lancaster: Technomic Publishing Co., 1997, 3-29.

[6] E. Vunain, A. Mishra, B. Mamba, Dendrimers, mesoporous silicas and chitosan-based nanosorbents for the removal of heavy-metal ions: A review, International journal of biological macromolecules 86 (2016) 570-586.

[7] A. Wight, M. Davis, Design and preparation of organic-inorganic hybrid catalysts, Chemical reviews 102(10) (2002) 3589-3614.

[8] M. Dziadek, E. Stodolak-Zych, K. Cholewa-Kowalska, Biodegradable ceramic-polymer composites for biomedical applications: A review, Materials Science and Engineering: C 71 (2017) 1175-1191.

[9] S. Khoee, R. Bafkary, F. Fayyazi, DOX delivery based on chitosan-capped graphene oxide-mesoporous silica nanohybride as pH-responsive nanocarriers, Journal of Sol-Gel Science and Technology 2(81) (2016) 493-504.

[10] X. Wang, Y. Du, J. Luo, B. Lin, J.F. Kennedy, Chitosan/organic rectorite nanocomposite films: Structure, characteristic and drug delivery behaviour, Carbohydrate Polymers 69(1) (2007) 41-49.

[11] K. Kavya, R. Dixit, R. Jayakumar, S.V. Nair, K.P. Chennazhi, Synthesis and characterization of chitosan/chondroitin sulfate/nano-SiO2 composite scaffold for bone tissue engineering, Journal of biomedical nanotechnology 8(1) (2012) 149-160

[12] E.-J. Lee, D.-S. Shin, H.-E. Kim, H.-W. Kim, Y.-H. Koh, J.-H. Jang, Membrane of hybrid chitosan–silica xerogel for guided bone regeneration, Biomaterials 30(5) (2009) 743-750.

[13] E.-J. Lee, H.-E. Kim, Accelerated bony defect healing by chitosan/silica hybrid membrane with localized bone morphogenetic protein-2 delivery, Materials Science and Engineering: C 59 (2016) 339-345.

[14] W. Li, R. Yuan, Y. Chai, L. Zhou, S. Chen, N. L. Immobilization of horseradish peroxidase on chitosan/silica sol–gel hybrid membranes for the preparation of hydrogen peroxide biosensor, Journal of biochemical and biophysical methods 70(6) (2008) 830-837.

[15] K. Kavya, R. Jayakumar, S. Nair, K.P. Chennazhi, Fabrication and characterization of chitosan/gelatin/nSiO2 composite scaffold for bone tissue engineering, International journal of biological macromolecules 59 (2013) 255-263.

[16] J. Sowjanya, J. Singh, T. Mohita, S. Sarvanan, A. Moorthi, N. Srinivasan, N. Selvamurugan, Biocomposite scaffolds containing chitosan/alginate/nano-silica for bone tissue engineering, Colloids and Surfaces B: Biointerfaces 109 (2013) 294-300.

[17] H. Zhao, Q. Cui, V. Shah, J. Xu, T. Wang, Enhancement of glucose isomerase activity by immobilizing on silica/chitosan hybrid microspheres, Journal of Molecular Catalysis B: Enzymatic 126 (2016) 18-23.

[18] H. Song, W. Yuan, P. Jin, W. Wang, X. Wang, L. Yang, Y. Zhang, Effects of chitosan/nano-silica on postharvest quality and antioxidant capacity of loquat fruit during cold storage, Postharvest Biology and Technology 119 (2016) 41-48.

[19] Y. Vijaya, S.R. Popuri, V.M. Boddu, A. Krishnaiah, Modified chitosan and calcium alginate biopolymer sorbents for removal of nickel (II) through adsorption, Carbohydrate polymers 72(2) (2008) 261-271.

[20] R. Nithya, T. Gomathi, P. Sudha, J. Venkatesan, S. Anil, S.-K. Kim, Removal of Cr (VI) from aqueous solution using chitosan-g-poly (butyl acrylate)/silica gel nanocomposite, International journal of biological macromolecules 87 (2016) 545-554.

[21] R.D.C. Soltani, A. Khataee, M. Safari, S. Joo, Preparation of bio-silica/chitosan nanocomposite for adsorption of a textile dye in aqueous solutions, International Biodeterioration & Biodegradation 85 (2013) 383-391.

[22] S. Zhang, T. Lü, D. Qi, Z. Cao, D. Zhang, H. Zhao, Synthesis of quaternized chitosan-coated magnetic nanoparticles for oil-water separation, Materials Letters 191 (2017) 128-131.

[23] L. Cao, H. Zhang, C. Cao, J. Zhang, F. Li, Q. Huang, Quaternized chitosan-capped mesoporous silica nanoparticles as nanocarriers for controlled pesticide release, Nanomaterials 6(7) (2016) 126.

[24] J. Abdullah, M. Ahmad, L.Y. Heng, N. Karuppiah, H. Sidek, Stacked films immobilization of MBTH in nafion/sol-gel silicate and horseradish peroxidase in chitosan for the determination of phenolic compounds, Analytical and bioanalytical chemistry 386(5) (2006) 1285-1292.

[25] Y. Miao, S. Tan, Amperometric hydrogen peroxide biosensor with silica sol–gel/chitosan film as immobilization matrix, Analytica Chimica Acta 437(1) (2001) 87-93.