Fabrication of bioactive glass/phosphorylated chitosan composite scaffold and its effects on MC3T3-E1 cells

This study aimed to synthesize bioactive glass (BG) and phosphorylated chitosan (PCS), and fabricate a BG/PCS composite scaffold. The physical properties (mechanical strength, swelling degree, and degradation rate) of the BG/PCS scaffold were tested. Thein vitromineralization properties of composite scaffolds in simulated body fluid were investigated. MC3T3-E1 cell responses with the BG/PCS scaffold were investigated using live/dead cell staining, actin staining, alkaline phosphatase (ALP) activity, and Alizarin red staining. Our results showed that the scaffold had an inner porous structure, good swelling properties, and good degradation rate. After immersion in SBF, the scaffolds demonstrated high properties in inducing mineralization. Leaching solutions of the composite scaffolds exhibited good cytocompatibility. MC3T3-E1 cells adhered, spread, and proliferated on the scaffold. The BG/PCS composite scaffold showed osteo-inductive activity by increasing ALP activity and calcium deposition. Our results indicated that the BG/PCS scaffold had potential applications as a bone-defect repair biomaterial.

Biomimetic Hydroxyapatite Crystals Growth on Phosphorylated Chitosan Films by In Vitro Mineralization Used as Dental Substitute Materials

Chitosan (CS) films exhibit great potential as a substrate for the in vitro mineralization process. In this study, to mimic the formation of nanohydroxyapatite (HAP) as natural tissue, CS films coated with a porous calcium phosphate were investigated using scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FTIR), X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Calcium phosphate coating deposited on phosphorylated derivatives of CS was obtained by a process based on phosphorylation, Ca(OH)₂ treatment and artificial saliva solution (ASS) immersion. The phosphorylated CS films (PCS) were obtained by partial hydrolysis of the PO₄ functionalities. It was demonstrated that this precursor phase could induce the growth and the nucleation of the porous calcium phosphate coating when immersed in ASS. Moreover, oriented crystals and qualitative control of calcium phosphate phases on CS matrices are obtained in a biomimetic mode. Furthermore, in vitro antimicrobial activity of PCS was evaluated against three species of oral bacteria and fungi. It revealed an increase in antimicrobial activity with minimum inhibition concentration (MIC) values of 0.10% (Candida albicans), 0.05% (Staphylococcus aureus) and 0.025% (Escherichia coli) which proves their possible use as dental substitute materials.

Selective monophosphorylation of chitosan via phosphorus oxychloride

Chitosan was selectively monophosphorylated via reaction with phosphorus oxychloride (POCl₃) to enhance water solubility while avoiding polyphosphate formation. The use of POCl₃ resulted in negligible product degradation (i.e., breakdown of O-glycosidic bonds) even after a 3 d reaction period (<5% weight loss). X-ray photoelectron spectroscopy (XPS) characterization of the POCl₃-phosphorylated chitosan (P-chitosan) revealed a phosphorus to nitrogen (P/N) atomic ratio of 0.30. Phosphorus-31 nuclear magnetic resonance (³¹P NMR) spectroscopy verified the monophosphorylation of chitosan's primary and secondary alcohols, and primary amines. The calcium chelation efficiency for the phosphorylated product approached 0.05 mg Ca²⁺ per mg of P-chitosan as measured by inductively coupled plasma-optical emission spectrometry (ICP-OES), indicating improved chelation over native chitosan. This selective monophosphorylation approach proved useful for modifying other biopolymers, including cellulose and alginate.