The pH dependence of monofilament sutures on hydrolytic degradation

Hydrolytic degradation of two nonabsorbable sutures, four absorbable sutures, and a new type of absorbable suture was studied in buffered media of various pHs at 37 degrees C. The pH levels fixed in this study were 1.0, 7.4, 8.5, and 10.5. Physical measurements were made on the retention of tensile strength and melting temperature of the sutures after hydrolysis for 12 weeks. Sutures containing glycolic acid as a comonomer exhibited enhanced degradation in alkaline media, similar to polyglycolide multifilament sutures. Poly-p-dioxanone (PDS II) suture lost strength to a significant extent at pH 1.0, suggesting that care should be taken when this suture is used for closing tissues in contact with acidic media, such as the stomach. In marked contrast, the degradation of lactide-epsilon-caprolactone copolymer [P(LA/CL)] suture was not sensitive to the pH of media. The surface morphology of hydrolyzed sutures varied, depending on the pH of media. Particularly, moon-crater-shaped impressions were observed on glycolide-epsilon-caprolactone copolymer (MONOCRYL) and glycolide-trimethylene carbonate-dioxanone copolymer (BIOSYN) sutures. Among the nonabsorbable sutures, nylon (ETHILON) exhibited the fastest loss of strength in acidic buffer solution, and polypropylene (PROLENE) suture retained most of its initial strength at all pHs studied.