Abstract
This work investigates the degradation of PLGA implants in an aqueous medium maintained at physiological pH ≈ 7.4. Two limiting systems are also investigated, which involve the degradation of PLGA microspheres in two different media characterized by: (i) a non-regulated pH, for emulating the autocatalyzed degradation in the implant core; and (ii) a regulated physiological pH, for emulating the uncatalyzed degradation at the implant surface. The degradation experiments were carried out along 40–50 days, and samples withdrawn during this period were characterized by gravimetry, electronic microscopy, and size exclusion chromatography. Experimental results suggest that PLGA implants are degraded according to a time-variant spatial pattern, which depends on the pH of the surrounding medium. Initially, the implants suffered a typically bulk erosion process, governed by the acidification of the implant core; and after breakage of the implant wall, the regulated physiological pH induces a surface erosion process. The two auxiliary microsphere-based experiments were useful to elucidate the degradation phenomena occurring in the PLGA implants. The evolution of the mass loss and the weight-average molecular weight along the degradation can be successfully predicted by simple mathematical models based on first-order kinetics.
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Acknowledgments
In memory of Dr. Ricardo J.A. Grau and Dra. María Inés Cabrera, who passed away while this paper was in preparation. The authors are grateful for the financial support received from the following Argentine institutions: Agencia Nacional de Promoción Científica y Tecnológica (ANPCYT), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), and Universidad Nacional del Litoral (UNL).
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Boimvaser, S., Mariano, R.N., Turino, L.N. et al. In vitro bulk/surface erosion pattern of PLGA implant in physiological conditions: a study based on auxiliary microsphere systems. Polym. Bull. 73, 209–227 (2016). https://doi.org/10.1007/s00289-015-1481-6
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DOI: https://doi.org/10.1007/s00289-015-1481-6