Surface engineered biomaterials and ureteral stents inhibiting biofilm formation and encrustation

Abstract

Protection of ureteral stents against infections is a significant current challenge raised by increasing the number of stentings and infections, microbial resistance to conventional antibiotics and multi-drugs treatments, side effects for the patients like damage of surrounding tissue and high morbidity. Surface engineered biomaterials and ureteral stents, reducing biofilm formation and encrustation would contribute to mitigation of the problem.The aim of this review is to present the progress during the last 5 years in the development of surface engineered antimicrobial biomaterials and stents with expectation to raise some new fruitful ideas in this direction. Strategies aimed at preventing, disrupting, or removing adherent microbes and biofilms from biomaterials and ureteral stents are its main subject. Various antibacterial agents, modifications, and coatings as well as preparation, deposition and characterization techniques are among the topics covered. A brief market analysis is also included covering the significance of ureteral stents associated infections and a mode of development of a biofilm.The review of the progress during the last 5 years shows a continuing interest in surface modification and coating employing three principal anti-biofilm strategies: 1) mechanical detachment; 2) killing microbial cells and 3) creation of low-adhesive surfaces. The known surface engineering solutions report a reduced, to some extent, biofilm formation and encrustation of biomaterials and ureteral stents, but none of them is able to totally stop their development.Some new trends are observed, such as complementary antimicrobial protection by coating and flow dynamic; biodegradable coatings releasing antimicrobial agent; quasi irremovable surface coatings, delivering drug or antimicrobial agent as well as new carbon and biodegradable materials; bacteriophages and phage cocktails, etc. Almost all of them are under intense in vitro studies; only few of them were studied in vivo animal models and none in humans. Some of the liquid infused coatings, already tested in animal models, seem to be the closest to clinical application but so far no one has been applied to ureteral stents.This review outlines some future research directions and major challenges in the surface engineered biomaterials and ureteral stents. It gives ideas how, by surface engineering, to approach more closely the “clean” ureteral stent to not allow microbial adhesion and encrustation and thus sharply reduce the ureteral stents associated infections and stent dysfunction.The most important prerequisite of the non-toxic “clean” surface is to be low adhesive. Its anti-biofilm performance could be improved by including bio-surfactant and/or inhibitor of quorum sensing (QS) and/or inhibitor of the crosslinking of the exopolymeric substances (EPSs). The key to identifying a “universal” surface that would repel/release all microbial cells is maybe hidden in the in-depth understanding of the mechanism of the initial reversible adsorption of the EPSs secreted by microbial cells, since it initiates the whole biological cascade of biofilm development.