Surface Modification of Gentamicin-loaded Polylactic Acid (PLA) Microsphere Using Double Emulsion and Solvent Evaporation: Effect on Protein Adsorption and Drug Release Behaviour

Polylactic acid (PLA) microsphere as a drug carrier has been extensively investigated for drug delivery systems. However, due to its limitation of surface hydrophobicity, surface modifications have been studied to improve its utilisation in tissue engineering applications. In the present study, PLA microsphere loaded with gentamicin (GENMS) was modified to enhance its hydrophilicity by surface treatment with additional of ethanol. Ethanol was applied as a co-treating medium in alkaline hydrolysis of NaOH to assist the hydroxide nucleophilic attack on the ester bond of PLA. Alkaline concentrations of NaOH and NaOH/ethanol was set at 0.15 M, 0.25 M and 0.35 M. After surface treatment, hydrophilicity of GENMS surface were improved significantly whereby contact angle was reduced for about 23.1% and 26.8% for modification using NaOH and NaOH/ethanol, respectively, compared with the neat GENMS. Obvious surface roughness presented by NaOH/ethanol modification improved hydrophilicity of GENMS. As a result, protein adsorption on the GENMS surface treated by NaOH/ethanol were reduced than NaOH modification. Moreover, the highest encapsulation efficiency by NaOH/ethanol modification provided an advantage of co-treating by ethanol and has a greater drug release compared with NaOH modification.