Characterization, antibiofilm and biocompatibility properties of chitosan hydrogels loaded with silver nanoparticles and ampicillin: an alternative protection to central venous catheters.

The purpose of this study was to generate novel chitosan hydrogels (CHs) loaded with silver nanoparticles (AgNPs) and ampicillin (AMP) to prevent early formation of biofilms. AgNPs and CHs were characterized by UV-Vis, DLS, TEM, rheology, FT-IR, Raman, and SEM. The antibiofilm effect of the formulations was investigated against four multidrug-resistant and extensively drug-resistant pathogens using a colony biofilm, a high cell density and gradients model. Also, their hemostatic properties and cytotoxic effect were evaluated. Rheology results showed that CHs with AgNPs and AMP are typical non-Newtonian pseudoplastic fluids. The CH with 25 ppm of AgNPs and 50 ppm AMP inhibited the formation of biofilms of Acinetobacter baumannii, Enterococcus faecium and Staphylococcus epidermidis, while a ten-fold increase of the antimicrobial's concentration was needed to inhibit the biofilm of the ß-lactamase positive Enterobacter cloacae. Further, CH with 250 ppm of AgNPs and 500 ppm AMP showed anticoagulant effect, and it was shown that all formulations were biocompatible. Besides to previous reports that described the bioadhesion properties of chitosan, these results suggest that AgNPs and AMP CHs loaded could be used as prophylactic treatment in patients with central venous catheter (CVC), inhibiting the formation of biofilms in their early stages, in addition to their anticoagulant effect and biocompatibility, those properties could keep the functionality of CVC helping to prevent complications such as sepsis and thrombosis.

In Vitro Synergism of Silver Nanoparticles with Antibiotics as an Alternative Treatment in Multiresistant Uropathogens.

The increase in the prevalence of bacterial resistance to antibiotics has become one of the main health problems worldwide, thus threatening the era of antibiotics most frequently used in the treatment of infections. The need to develop new therapeutic strategies against multidrug resistant microorganisms, such as the combination of selected antimicrobials, can be considered as a suitable alternative. The in vitro activities of two groups of conventional antimicrobial agents alone and in combination with silver nanoparticles (AgNPs) were investigated against a set of ten multidrug resistant clinical isolate and two references strains by MIC assays and checkerboard testing, as well as their cytotoxicity, which was evaluated on human fibroblasts by MTT assay at the same concentration of the antimicrobial agents alone and in combination. Interesting results were achieved when the AgNPs and their combinations were characterized by Dynamic Light Scattering (DLS), Zeta Potential, Transmission Electron Microscopy (TEM), UV⁻visible spectroscopy and Fourier Transforms Infrared (FTIR) spectroscopy. The in vitro activities of ampicillin, in combination with AgNPs, against the 12 microorganisms showed one Synergy, seven Partial Synergy and four Additive effects, while the results with amikacin and AgNPs showed three Synergy, eight Partial Synergy and one Additive effects. The cytotoxic effect at these concentrations presented a statistically significant decrease of their cytotoxicity (p < 0.05). These results indicate that infections caused by multidrug resistant microorganisms could be treated using a synergistic combination of antimicrobial drugs and AgNPs. Further studies are necessary to evaluate the specific mechanisms of action, which could help predict undesirable off-target interactions, suggest ways of regulating a drug’s activity, and identify novel therapeutic agents in this health problem.