[Biodegradable ureteral stents: in vitro assessment of synthetic polymer degradation rate]

To evaluate the suitability of a biodegradable synthetic material based on poly(L-lactide-co-ε-caprolactone) for the manufacture of ureteral stents in vitro.

An investigation of 10 identical samples of polymeric material was performed. Urine from one patient was used for each sample throughout the study. The material in the form of a 6 cm long rod was placed in a sterile plastic container with the patient's urine and incubated at a temperature of 38 °C until the material was physically destroyed. Urine was replaced in the container once every 48 hours. The appearance and strength maintenance of the material were evaluated on 3, 7, 10, 14, 21, 28, 35 and 42 days. The material fragment of about 5 mm in length was separated in order to change the molecular mass of the polymer during degradation. The weight-average molecular weight (Mw) was measured using gel permeation chromatography.

The samples retained their mechanical properties until the 35th day. A change in color of some samples was noted on the 10th day. The process of degradation started immediately after the initiation of incubation, and in the first 2 weeks a reduction of the molecular mass up to 50-60% from the baseline has been observed, after 35 days - up to 30% from the baseline. At the indicated time, the material was destroyed with minimal mechanical impact. At about 2 months the molecular mass decreased to 10% from the baseline, the samples disintegrated into fragments. There was no significant difference in the dynamics of material degradation in the urine of different patients.

Degradation of the investigated synthetic material occurs at a predictable rate, regardless of individual features of biochemical composition of the urine and its pH. The time of complete degradation of the material is 2-3 months. Lack of incrustation and acceptable degradation profile make the proposed material promising for creation of biodegradable ureteral stents.