Effect of Chitosan Coating on BSA Adsorption on Bioactive Glasses

Objectives:  To evaluate the effects of chitosan coatings on the in-vitro protein adsorption and release kinetics from bioactive glasses with and without boron-doping (13-93B3 and 13-93B0).

Methods: 13-93B0 and 13-93B3 BG discs were fabricated and sintered at 650 °C (B0) and 540 °C (B3). For BSA release assay, 4-mg BSA was loaded onto sample discs (diameter=13-mm, thickness=1.9-mm) coated with 100-μL 80% or 94% deacetylated (DA) chitosan at concentrations 0.5% and 2%. Uncoated (UC) samples were used as controls. Discs were immersed in 2-mL PBS, which was collected and replenished at time points between 0.5 to 336 hours.  BSA release was evaluated using BCA Protein Assay. For the BSA characterization using FTIR, the spectra of BSA-adsorbed BG discs were subtracted from the spectra of the corresponding no BSA BG with or without chitosan coating. Secondary structures of amide I were resolved using Gaussian peak analysis.    

Results: 100% protein release occurred by 24-hours for all B3 groups. Chitosan coating delayed 100% release from B0 2-80 and B0 2-94 to 72-hours. 94% DA chitosan coating also prolongs the release time when compared to 80% DA coating. For the FTIR analysis, the α-helical contents of both B0-UC and B3-UC were found to be 15-20% while 2% chitosan coated groups achieved higher α-helical contents (30-40%), in the range of natural BSA in lyophilized form. 

Conclusion:  The faster BSA release in B3 groups of this study matches with the faster degradation properties of B3 when compared to B0.  Chitosan effectively prolonged the release time of BSA. FTIR analysis shows chitosan to prevent protein unfolding on bioactive glass surfaces. Overall, this study indicates that chitosan coating on bioactive glass can inhibit BSA denaturing and prolong BSA release from bioactive glass in vitro.