Synthesis And Properties Of Chitosan/Silica Composite Microspheres

Chitosan?CS?is obtained by deacetylation of chitin.As a non-toxic natural polymer,chitosan has good biocompatibility and biodegradability,and has the characteristics of antibacterial,antitumor,bioadhesion,drug sustained release and so on.Silica?SiO₂?xerogel has excellent biocompatibility,strong thermal stability,good chemical stability,and bone repair properties.In order to obtain a biocomposite with both bone repair and drug-loading properties,we chose to combine bioactive silica with biocompatical and shapable chitosan in order to obtain a biocompsotie material with intergrated advantanges.In this paper,the prepared CS/SiO₂ mixed sol is added to the water-in-oil system by adding the emulsified cross-linking method and the sol-gel method,and glutaraldehyde is added to cross-link with chitosan.The CS molecule changes from a chain to a three-dimensional network structure,and the SiO₂ sol network in the droplet will also shrink and solidify.Add Na OH to adjust the p H to precipitate the microspheres and synthesize CS/SiO₂ composite microspheres with different parameters.The microspheres were characterized and tested to determine the best parameters for the preparation of microspheres.On the basis of this research,this thesis also added poly?vinyl alcohol?as the third component to synthesized the PVA/CS/SiO₂ tri-component composite microspheres under the same process.The main research results in this paper:?1?In a water-in-oil system with an oil-water ratio of 10/1,The CS/SiO₂composite microspheres with good dispersion,spherical regularity,and uniform particle size were successfully obtained through the emulsion cross-linking method,with an average particle size of 26.7?m.The best preparation parameters were listed in the following:the concentration of CS was 2%;the amount of Span 80 was 1 g;the amount of glutaraldehyde?25%?was 0.5 m L;the concentration of Na OH was 4 M,the theoretical SiO₂ content was 20%.The inorganic phase deposited in the obtained CS-20%SiO₂ composite microspheres is amorphous SiO₂,and its actual content is determined to be 15%by TG analysis.After immersion for 3 days in simulated body fluid?1.5SBF?,it was found that CS-20%SiO₂composite microspheres have better in vitro biological activity than pure CS microspheres,which were expected to be used as bone repair materials in the field of bone tissue engineering.?2?Vancomycin hydrochloride?VH?was selected as the model drug to evaluate the drug loading and drug release performance of CS/SiO₂.The test results show that although compared with the pure CS microspheres,the CS/SiO₂ composite microspheres due to the addition of SiO₂showed a reduced encapsulation efficiency and drug loading capacity but an improved drug sustained-release behavior.The cumulative amounts of VH released from the pure CS,CS-20%SiO₂ and CS-40%SiO₂composite microspheres after 288 h were determined as 87.2%,82.4%and 76.3%,respectively.?3?Based on the preparation conditions of the CS/SiO₂ composite microspheres,the PVA/CS/SiO₂ tri-component composite microspheres with small particle size and uniform spherical shape were also successfully obtained by adding PVA and adjusting the concentration of the organic phase.The study found that when the concentration of PVA is 4%,the concentration of CS is 0.75%,the content of glutaraldehyde?25%?is 0.6 m L,and the theoretical weigh ratio of SiO₂ was 20%,the obtained PVA/CS/SiO₂ composite microspheres exhibited the best morphology?good spherical shape and high dispersity?and an average particle size of 8.6?m.In addition,compared with the PVA/CS composite microspheres,PVA/CS-20%SiO₂ composite microspheres the cumulative release amount of VH reached 78.3%after 96 h,showed more sustained drug-release behavior.This article has 33 pictures,6 tables,and 122 references.