Fabrication and Evaluation of the Immobilization of Collagen onto the PLA Film Surface using Alkaline Hydrolysis

Aliphatic polyesters, such as polylactic acid（PLA）, are gaining popularity as biodegradable materials for biomedical applications. This study aimed to evaluate the efficacy of collagen immobilization on PLA films for the attachment and proliferation of osteoblast-like cells（OLCs）after alkali treatment with potassium and sodium hydroxide （KOH/NaOH）. The surfaces of the PLA films were chemically modified by hydrolysis with 0.5 M KOH/NaOH to introduce carboxylic acid（COOH）groups（PLA-KOH-COOH or PLA-NaOH-COOH）. Subsequently, collagen was surface-immobilized via a condensation reaction between the COOH groups on the hydrolyzed surface and the amino groups of collagen using water-soluble carbodiimide to form the Coll-PLA-KOH and -NaOH films. The contact angle of the PLA surface with respect to the double-distilled water decreased significantly after alkali treatment and collagen immobilization（CollPLA-KOH and Coll-PLA-NaOH）, indicating reduced hydrophobicity. X-ray photoelectron spectroscopy（XPS）analysis showed the presence of nitrogen on the surface of the Coll-PLA-KOH and Coll-PLA-NaOH films, indicating successful collagen immobilization. The number of mouse OLCs or MC3T3E-1 cells attached on the surface of the Coll-PLA-KOH and Coll-PLA-NaOH films increased significantly. Moreover, morphological differences were observed between cells cultured on Coll-PLA-KOH/NaOH and PLA films. The cells cultured on Coll-PLA-KOH/NaOH exhibited significantly enhanced mineralization than those on PLA after 21 days. These results confirmed that the alkali-treated collagen-immobilized PLA films successfully enabled cell attachment and proliferation. Treatment of the PLA surface with KOH enhances the biological activity of MC3T3-E1 cells, consistent with our previous study using NaOH. Therefore, the Coll-PLA-KOH film can potentially be used in dental medicine and bone regeneration applications.