SYNOPSIS
In the present study, the author prepared surface hydrolyzed poly(lactic acid) (PLA) films (PLA-COOH), i.e., carboxylic acid introduction, by NaOH hydrolysis and investigated apatite formation on PLA-COOH films after immersion in Hanks' balanced salt solution (HBSS, pH 7.4) without organic species. In addition, the degradation behavior was monitored in buffered solution with or without surface carboxylic acid groups. HBSS was used as simulated body fluid for evaluating in vitro biocompatibility
PLA-COOH was easily prepared by NaOH hydrolysis for 3h. PLA-COOH showed a greater degree of degradation after immersion in phosphate buffered saline solution (pH 7.4) compared with native PLA.The weight loss of PLA and PLA-COOH films was approximately 3.2% and 4.9% after 115 days immersion, respectively.
Scanning electron microscopy observation revealed that PLA-COOH film showed a quicker and greater amount of precipitation on the film compared with original unmodified PLA after immersion in HBSS. Analysis of the precipitates by X-ray diffraction and Fourier-transformed infrared spectroscopy confirmed that their main-component was carbonate-containing apatite.
In conclusion, it is expected that PLA-COOH is a good candidate for a scaffold material to enhance bone formation in vivo and will have a potential for dental clinical use.

Key words: PLA film, biomaterials, hydroxyapatite, simulated body fluid, carboxylic acid groups