Abstract:
Alarming numbers of blood stream related nosocomial infections are caused by biofilm formation on catheters by pathogens. This major concern strongly influences prognosis and management of biofilm associated infections, resulting in increased medical costs and death. Antimicrobial coatings over catheters have been effective in reducing microbial adhesion and subsequent biofilm formation. In this study, an attempt was made to coat central venous catheters with antimicrobial-loaded polymeric nanoparticles and evaluate the resulting antibiofilm potential. High Performance Liquid Chromatographic (HPLC) protocols were developed and validated for detection of the two selected antimicrobials targeted for coating the catheters, meropenem and fluconazole. Poly-ɛ-caprolactone polymeric nanoparticles loaded with these antimicrobials were prepared using a modified nanoprecipitation method. With light scattering analyses, meropenem and fluconazole nanoparticles were negatively charged and sized at around 250 nm. Transmission Electron Microscopy (TEM) showed almost spherical nanoparticles. Differential Scanning Calorimetry (DSC) and X-ray diffraction (XRD) analyses indicated drug loading into the polymer and crystalline nature of the nanoparticles. HPLC aided loading studies confirmed loading and identified the best four meropenem and three fluconazole loaded nanoparticles for drug release profiling. Release patterns varied between antimicrobial and among formulations. Inhibitory and cidal concentrations of meropenem against planktonic cells were lower than against biofilm cells and biofilms of Staphylococcus epidermidis and Klebsiella pneumoniae. However, high concentrations of fluconazole were ineffective against planktonic and sessile cells of Candida albicans. A dip-coating technique was then used to coat the catheters by suspending two selected meropenem nanoparticles in a coating solution consisting of ethyl cellulose dissolved in iso-propyl alcohol and triacetin. The coated catheters were then challenged with microbial culture for 72 hours at 37°C with rotary agitation. Biofilms formed over the catheters were quantified with crystal violet staining and microscopically evaluated. Paradoxically, coating with nanoparticles caused roughening of catheter surface and promoted biofilm formation (p<0.05). However, reduction in biofilm formation was observed for Staphylococcus epidermidis (p>0.05) and Klebsiella pneumoniae (p<0.05), when challenged with catheters coated with meropenem nanoparticles. Increasing drug load within the polymeric nanoparticles and further exploration of catheter coating methods are predicted to cumulatively strengthen the antibiofilm ability of antimicrobials-in-nanoparticles coated catheters.
