Silver nanoparticles exert concentration-dependent influences on biofilm development and architecture.

OBJECTIVES: To investigate the impact of silver nanoparticles (AgNPs) on the biofilm growth and architecture. MATERIALS AND METHODS: Silver nitrate was reduced by d-maltose to prepare AgNPs in the presence of ammonia and sodium hydroxide. The physicochemical properties of AgNPs were characterized by transmission electron microscopy, ultraviolet-visible spectroscopy and inductively coupled plasma mass spectrometry. The development of biofilm with and without AgNPs was explored by crystal violet stain. The structures of mature biofilm were visually studied by confocal laser scanning microscopy and scanning electron microscopy. Bacterial cell, polysaccharide and protein within biofilm were assessed quantitatively by colony-counting method, phenol-sulphuric acid method and Bradford assay, respectively. RESULTS: The spherical AgNPs (about 30 nm) were successfully synthesized. The effect of AgNPs on Pseudomonas aeruginosa biofilm development was concentration-dependent. Biofilm was more resistant to AgNPs than planktonic cells. Low doses of AgNPs exposure remarkably delayed the growth cycle of biofilm, whereas high concentration (18 µg/mL) of AgNPs fully prevented biofilm development. The analysis of biofilm architecture at the mature stage demonstrated that AgNPs exposure at all concentration led to significant decrease of cell viability within treated biofilms. However, sublethal doses of AgNPs increased the production of both polysaccharide and protein compared to control, which significantly changed the biofilm structure. CONCLUSIONS: AgNPs exert concentration-dependent influences on biofilm development and structure, which provides new insight into the role of concentration played in the interaction between antibacterial nanoparticles and biofilm, especially, an ignored sublethal concentration associated with potential unintended consequences.

[Transurethral resection of the prostate for urinary retention after seed implantation for prostate cancer: report of 2 cases].

OBJECTIVE: To investigate the effect of transurethral resection of the prostate (TURP) in the treatment of urinary retention following seed implantation for prostate cancer. METHODS: We treated 2 cases of urinary retention following seed implantation for prostate cancer by TURP, and analyzed their clinical data. RESULTS: The operations were successful in both of the cases, with mean operation time of 60 min. Postoperative nocturnal urination of the patients averaged 2 times per night as compared with 5 - 6 times per night preoperatively, and their scores on IPSS and quality of life were significantly improved after surgery. CONCLUSION: TURP affords satisfactory results in the treatment of urinary retention following seed implantation for prostate cancer patients.