Chapter 6 Retention and Viability of Staphylococcus epidermidis on Protein-Coated Self-Assembled Monolayers

摘要

Coatings for biomaterials, such as self-assembled monolayers (SAMs), are being developed to resist biofilm formation on catheters and other devices. Researchers need to have fast and simple laboratory assays for assessing the properties of the SAMs, and many use batch or dip tests, although a variety of experimental procedures can be found in the literature. We optimized the design of simple batch assays to test the performance of a variety of SAMs in preventing retention of or in deactivating a clinically isolated strain of Staphylococcus epidermidis, with the goal of rapid screening to allow for the development of new implant coatings to prevent implant- associated infections. Ten carbon chain SAMs terminating in 4-(16-bromo hexadecyloxy)pyridine (PDT), 5-(10- mercaptodecyloxy)isophthalic acid (IPA), and isophthalic acid complexed with silver (IAG) were constructed on gold-coated glass slides. The retention and viability of S. epidermidis to the varying substrates was quantified via fluorescence microscopy. Parallel experiments were designed in order to help mimic in vivo conditions, in which a model protein, fetal bovine serum (FBS), was deposited onto the SAMs to determine how protein presence affected bacterial retention and viability. The deposited protein layers were examined by atomic force microscopy (AFM) and quantified in terms of height and roughness. Optimal batch test conditions were 30 min incubation of substrates in bacterial solutions with concentrations of 2 x 107 cells/mL. All of the SAMs promoted decreased bacterial retention compared to the control surface, bare gold. For the protein deposition phase, incubating the slide in 10% FBS solution for 80 min yielded uniform and reproducible protein structures. Bacteria were less prone to retention on an FBS deposited substrate, with reductions of 79.3% on FBS + gold, 92.4% on FBS + IAG, and 95.5% on FBS + IPA, compared to the substrates without proteins.