Ceragenin mediated selectivity of antimicrobial silver nanoparticles.

The understanding that common broad-spectrum antimicrobials disrupt natural microbial flora important in acquiring nutrients and preventing infection has resulted in a paradigm shift favoring more selective antimicrobials. This work explores silver nanoparticles conjugated with ceragenin, or cationic antimicrobials (CSA-SNPs), as a potential Gram-positive selective antimicrobial. Herein, CSA-SNPs are characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, and high-performance liquid chromatography-electrospray time-of-flight mass spectrometry (HPLC-ESI-TOF-MS). The antimicrobial properties are determined through minimum inhibitory concentration/minimum bactericidal concentration (MIC/MBC) and time-kill studies. Spatial selectivity of the conjugate nanoparticle was evaluated using confocal imaging, MATLAB statistical analysis, and video monitored interactions between bacteria and CSA-SNPs via laser trapping techniques. Cytotoxicity was also determined by live/dead staining and flow cytometry. Average particle size, as determined through TEM analysis, and hydrodynamic diameter, as determined via DLS, are 63.5 ± 38.8 and 102.23 ± 2.3 nm, respectively. The zeta potential of the SNP before and after CSA attachment is -18.23 and -8.34 mV, respectively. MIC/MBC data suggest that CSA-SNPs are 8 times more effective against Staphylococcus aureus than SNPs alone. Furthermore, MATLAB analysis of confocal imaging found that 70% of CSA-SNPs are within 2 µm of S. aureus, whereas this percentage falls to below 40% with respect to Escherichia coli. These results are bolstered further by laser trapping experiments demonstrating selective adherence of CSA-SNPs conjugates with bacterial strains. Cytotoxicity studies of CSA-SNPs against 3T3 fibroblasts indicate 50% cell viability at 50 ppm.

Maghemite, silver, ceragenin conjugate particles for selective binding and contrast of bacteria.

New synthesis techniques are providing increasing control over many inorganic nanoparticle characteristics, facilitating the creation of new multifunctional theranostics. This report proposes the synthesis and testing of a combination nanoparticle comprised of a maghemite core for enhanced T2 MRI contrast diagnostics, a colloidal silver shell acting as an antimicrobial and therapeutic vehicle, and a ceragenin (CSA-124) surfactant providing microbial adhesion. A polyacrylic acid functionalized maghemite nanoparticle is synthesized by a high temperature organic phase reduction followed by thiol functionalization and gold cluster seeding. A silver shell is formed through AgNO3 reduction, and an oriented monolayer of the thiolated ceragenin, is bound through a self-assembly process. The process and products are characterized throughout synthesis through TEM, DLS, FT-IR, UV-Vis, ICP-OES, HPLC-ESI-TOF-MS, DC magnetization and susceptibility, X-ray diffraction, and in vitro MRI. Synthesized Diagnostic Antimicrobial Nanoparticles (DANs) were found to have a spherical morphology with a diameter of 32.47±1.83 nm, hydrodynamic diameter of 53.05±1.20 nm, maximum magnetic moment of 12 emu/g NP (54 emu/g Fe) with little variation due to temperature, and are predominantly paramagnetic. In vitro MRI studies show that DANs contrast well at concentrations as low as 9 ppm, and successfully adhere to Staphylococcus aureus. DAN MIC was determined to be approximately 12 ppm and 24 ppm against S. aureus and Escherichia coli respectively.