Improvement of hydrophilicity and formation of heparin/chitosan coating inhibits stone formation in ureteral stents

Ureteral stents play an important role in draining urine, supporting the ureter, and preventing hydronephrosis and renal failure. Stones on the surface of ureteral stents can lead to local injury, urinary tract obstruction and tumor induction in patients. They are categorized as normal metabolic stones and infected stones according to whether bacterial infection occurs. To inhibit the formation of ureteral stones, monomethoxy poly(ethylene glycol)-poly(trimethyl carbonate) (mPEG-PTMC) is synthesized to improve the surface hydrophilicity of PTMC/PLCL biodegradable elastomers, and heparin/chitosan coatings are formed by layer-by-layer electrostatic self-assembly. The mPEG-PTMC effectively improves surface hydrophilicity without compromising the compatibility of the components. The contact angle is 62.58° when 10 wt% of mPEG-PTMC37 is present. Extracorporeal immersion for 1, 5, and 10 weeks mimicks normal metabolic stones, SEM and ICP-OES show that the increase of hydrophilicity could reduce the adhesion of calcium oxalate stones. The HEP/CTS coating also significantly reduces the coverage of calcium oxalate on the surface of the sample, and the calcium concentration decreases by 68.5%. Equipped with an extracorporeal dynamic urinary circulatory system to simulate the production of infected stones after bacterial infection, after seven days, mPEG-PTMC37 halved the stone surface coverage. Compared to PTMC/PLCL elastomer, mPEG-PTMC37, mPEG-PTMC28 and HTP/CTS coatings inhibit 38.72%, 15.55%, 39.60% of Ca and 65.06%, 57.47%, 70.11% of Mg, respectively. In addition, the heparin/chitosan coatings reduce the surface adhesion of Staphylococcus by 69.9%. The cell experiments show the materials all have good biocompatibility. It makes a useful exploration for developing a new kind of ureteral stents.