PC-1250

Infection is a serious medical complication associated with health care environments. Despite advances, the 5-10% incidence of infections for hospital patients is well documented. Sources of pathogenic organisms include medical devices such as catheters and endotracheal tubes. Offering guidance for curbing the spread of such infections, a model antimicrobial coating is described herein that kills bacteria on contact but is compatible with human cells. To achieve these characteristics, a novel blend of a conventional biomedical grade polyurethane (Tecoflex) with mixed soft block polyurethane is described. The functional polyurethane (UP-C12-50-T) has a copolyoxetane soft block P-C12-50 with quaternary ammonium (C12) and PEG-like side chains and a conventional poly(tetramethylene oxide) (PTMO, T) soft block. DSC and DMA data point to limited miscibility of UP-C12-50-T with Tecoflex. The blend of Tecoflex with 10 wt % UP-C12-50-T designated UP-C12-50-T-10 radically changed surface properties. Evidence for surface concentration of the P-C12-50 soft block was obtained by atomic force microscopy (AFM), dynamic contact angles (DCAs), zeta potentials (ζ), and X-ray photoelectron spectroscopy (XPS). The antimicrobial effectiveness of the blend coatings was established by the ASTM E2149 "shake flask" test for challenges of E. coli and a methicillin resistant strain of S. epidermidis. Cytocompatibility was demonstrated with an in vitro test designed for direct contact (ISO 10993-5). Growth of human mesenchymal stem cells (MSCs) beside and under UP-C12-50-T-10 indicated remarkable biocompatibility for a composition that is also strongly antimicrobial. Overall, the results point to a model coating with a level of P-C12-50 that combines high antimicrobial effectiveness and low toxicity to human cells.

Copper and cisplatin share copper transporter 1 (Ctr1) for cellular import. Copper depletion increases sensitivity of wild type yeast to cisplatin, whereas mitochondrial DNA-deficient rho0 cells are resistant to cisplatin. In the current study, we sought to determine whether copper deprivation modulates sensitivity of rho0 yeast to cisplatin. Yeast cultures grown in low copper medium and exposed to bathocuproine disulfonic acid resulted in significant reduction of intracellular copper. We report here that low copper medium rendered wild type hypersensitive to cisplatin, but failed to sensitize rho0 yeast to cisplatin. Wild type yeast grown in low copper medium exhibited ~2.0 fold enhanced cytotoxicity in survival and colony-forming ability compared to copper adequate wild type cells. The effect of copper restriction on cisplatin sensitivity was associated with upregulation of copper transporter 1 mRNA as well as protein, facilitating enhanced uptake and accumulation of cisplatin. Rho0 yeast also showed increased copper transporter 1 mRNA upon copper restriction, but failed to increase corresponding protein. Loss of synthesis of cytochrome coxidase 1 protein (Sco1) in rho0 cells deregulated copper transporter 1, impaired Pt uptake and lowered cytotoxicity, despite lowered glutathione levels. Sco1Δ mutants exhibited low copper transporter 1, reduced Pt accumulation suggesting that Sco1 mediated regulation of copper transporter 1 is responsible for altered sensitivity to cisplatin. Rho0 cells demonstrated loss of Sco1, resulting in copper deficiency by lowering copper transporter 1 abundance, via mechanism involving increased turnover due to ubiquitination. These findings reveal that a Sco1-dependent mitochondrial signal regulates cellular cisplatin import and cytotoxicity.