Biodegradable Polymers in Medical Devices

Abstract

Biodegradable polymers have transformed the design of temporary medical devices by eliminating the need for secondary surgical removal, reducing long-term foreign body response, and enabling controlled release of therapeutic agents during degradation. However, the clinical translation of biodegradable implants is constrained by incomplete understanding of in vivo degradation kinetics, mechanical property evolution during resorption, and the inflammatory response to acidic degradation products. This study conducted a systematic comparative evaluation of five biodegradable polymer families -- poly(lactic acid) (PLA), poly(glycolic acid) (PGA), poly(lactic-co-glycolic acid) (PLGA 50:50 and 85:15), poly(caprolactone) (PCL), and poly(dioxanone) (PDO) -- across four medical device applications: orthopaedic fixation screws, coronary stent coatings, absorbable surgical sutures, and controlled-release drug delivery matrices. Specimens (n = 360) were evaluated over 52 weeks of accelerated and real-time degradation in phosphate-buffered saline (PBS, pH 7.4, 37 C) and in a validated subcutaneous rat implantation model (n = 120 Wistar rats). PGA exhibited the fastest mass loss (95.2 +- 2.8% at 12 weeks) but generated the highest local tissue acidity (pH 3.4 +- 0.3), provoking a moderate inflammatory response (histological grade 2.8/4). PCL retained mechanical integrity longest (82.4 +- 4.6% tensile strength at 26 weeks) with the mildest tissue response (grade 0.8/4) but degraded too slowly (only 18.6 +- 3.2% mass loss at 52 weeks) for applications requiring complete resorption within 12 months. PLGA 85:15 provided the optimal balance: 90.4 +- 3.1% mass loss at 26 weeks, moderate mechanical retention (68.2 +- 5.4% at 12 weeks), and mild inflammatory response (grade 1.2/4). These results establish an evidence-based polymer selection framework matching degradation profile, mechanical requirements, and biocompatibility to specific medical device applications.