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Poly(lactic acid) (PLA) is a biodegradable polymer that has a variety of applications, one of which is as biomaterial in surgery or as functional layers on implants, due to its compatibility with living tissue. This paper reports the possibilities of quantification of poly(lactic acid) (PLA) in a polymer matrix such as poly(methyl methacrylate) (PMMA) by micro Raman spectroscopy (MRS). Blends of amorphous poly(DL‐lactic acid) with poly(methyl methacrylate) were prepared by the procedure of dissolution/precipitation. Thermal properties of the blends such as the glass transition temperature (Tg) were characterized by differential scanning calorimetry (DSC). The PLA/PMMA blends exhibited only a single glass transition region, indicating that this system is miscible. The PLA/PMMA system obeys the Gordon–Taylor equation (Tg versus PLA content). Various concentration ratios of PLA blends were prepared to use as a basis for quantitative analysis by MRS. Intensities of the characteristic bands at 813 cm−1 (νCOC of PMMA) and 873 cm−1 (νC―COO of PLA) were used for the calculation. The calibration graph showed a good linear correlation with an R2 value of 0.9985. On the basis of the calibration curve obtained, the determined content of several PLA/PMMA blends was in good agreement when compared with nominal contents. The limit of detection (LOD) and quantification (LOQ) were calculated by the calibration data set as signal‐to‐noise method. The relative standard deviation of this method was lower than 10% and the accuracy better than 4%. This study demonstrated that Raman spectroscopy provides an alternative non destructive method for quantitative analysis of PLA in a PMMA matrix. Copyright © 2015 John Wiley & Sons, Ltd.

Poly(lactic acid) (PLA) is a biodegradable polymer with a variety of applications, such as functional coatings on implants, due to its biodegradability, good biocompatibility and very low toxicity. In this study, the degradation behavior of high molecular weight poly(L-lactic acid) (L-PLA), which was used as polymer coating on permanent coronary metal stent, was investigated ex vivo. Poly(methyl methacrylate) (PMMA)-embedded histological specimens of stented porcine coronary arteries (left anterior descending artery, left circumflex artery and right coronary artery) were used to follow the degradation at various implantation times (6, 12, 24 and 36 months). Micro Raman spectroscopy was applied as an alternative technique for the determination of the residual content of the L-PLA coating. For this purpose, the PMMA-embedded cross sections of stented porcine coronary arteries were characterized through a previously developed Raman method for in situ quantitative analysis of PLA in a PMMA matrix. The residual content of L-PLA coating on the surface of the coronary metal stent was determined through the relative Raman band area ratio A PLA 873 = A PLA 873 þ A PMMA 813 À Á of the C-COO stretching band of PLA at 873 cm À1 and the C-O-C symmetric stretching band of PMMA at 813 cm À1 . This study demonstrated that Raman spectroscopy provides an alternative, non-destructive technique for quantification of L-PLA coating on permanent coronary metal stent in an animal model. The results suggest that the complete absorption of the L-PLA coating required more than 24 months for the layer thickness applied in this study and that the degradation of high molecular weight L-PLA in a porcine model is carried out by a hydrolytic degradation through the bulk erosion mode.Additional Supporting Information may be found online in the supporting information tab for this article.Degradation of PLA coating on permanent coronary metal stent

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