Nonhomologous bioinjectable materials in urology: 'size matters'?

Objective To assess the factors that influence how particles might become f ixed in tissues or migrate from them, by measuring the size of the injectab le particles, their susceptibility to phagocytosis and their affinity for f ibroblast attachment in culture. Materials and methods The particle size of three types of particulate unphy siological bioinjectable material, i.e. Urocol (Genesis Medical, Ltd., Lond on), Macroplastique(TM) (Uroplasty Ltd., Reading, UK) and Urethrin (Mentor Medical Systems, Wantage, UK) was analysed using phase-contrast light micro scopy and confocal microscopy. Human monocytes from peripheral blood were i ncubated with the three materials in phagocytic studies, where ingestion wa s determined by confocal microscopy. A fibroblast cell line was used to asc ertain the ability of the particles to act as a substrate for cell attachme nt in culture. Results The mean (SEM) maximum particle diameters of Macroplastique, Urethr in and Urocol were 209 (5.10) mu m, 49 (1.52) mu m and 14 (0.39) mu m, resp ectively. Rat peritoneal macrophages and human peripheral blood monocytes c ommonly ingested Urocol particles; the phagocytosis of Urethrin was rare an d that of Macroplastique was not detected. Fibroblasts adhered to Urocol pa ste and Urethrin particles, but not to Macroplastique. Conclusion Published reports of particle size and phagocytosis are confusin g, but a relationship clearly exists. Macroplastique is the largest particl e and is least likely to be phagocytosed by human mononuclear phagocytes. U rocol paste is the slowest to dissipate in culture conditions; the fat surf aces of Urethrin, but not Macroplastique, can serve as a substrate for fibr oblast anchorage.