Paper BI-TuA4
Tethered Antimicrobial Peptide WLBU2 for Capture of Circulating Bacteria and Endotoxin in Sepsis

Tuesday, October 20, 2015, 3:20 pm, Room 211D

Severe sepsis is a blood infection that affects over 750,000 people each year in the US alone, killing 28-50% (more than prostate cancer, breast cancer and AIDS combined). Symptoms result from a highly dysregulated immune response, which, if untreated, can lead to multiple organ failure and death. Currently, treatment uses wide-spectrum antibiotics, but this is hindered by the rise of antibiotic-resistant ‘superbugs’. One potential novel treatment is a high-throughput microfluidic hemoperfusion device, which specifically removes circulating bacteria and cell wall fragments (“endotoxin”) from blood. A device with a biocompatible and bioactive surface coating could selectively bind circulating bacteria and endotoxins from blood, enabling rapid, safe treatment of bacterial sepsis. WLBU2 is an α-helical, cationic amphiphilic peptide (CAP) with 13 positively-charged arginine and 11 hydrophobic tryptophan/valine residues oriented on opposite faces of the helix. WLBU2 has high anti-microbial potency against a variety of pathogens, and integrates into bacterial cell membranes (Deslouches, et al. J. Antimicrob. Chemother. 2007; 60: 669-672). Biocompatible, non-fouling surfaces can be made by covalently tethering a dense brush of polyethylene oxide (PEO) polymer chains at the surface. Longer PEO tethers terminated with WLBU2 should enable increased mobility and solvent accessibility to tethered WLBU2, allowing it to bind bacterial cells, without compromising the biocompatibility of the coated surface. Poly-L-arginine and poly-L-Lysine served as controls for charge effects, and Cys-WLBU2 served as a tether-free control. The surface chemistry is consistent with peptide immobilization at the surface using X-ray Photoelectron Spectroscopy (XPS). Atomic Force Microscopy (AFM) images demonstrated the uniform coverage of gold surfaces with PEO and peptides. Scanning Electron Microscopy (SEM) and Quartz Crystal Microbalance with Dissipation (QCMD) were used to demonstrate capture of bacteria at the coated surfaces. Tethered WLBU2 may more effectively bind P. aeruginosa than surface-bound WLBU2. Future work will focus on optimization of the coating to enable high loading of tethered bioactive molecules, without compromising surface biocompatibility. We are also developing a novel surface coating platform, using self-assembly and immobilization of PEO-based surfactants. This method shows promise in providing biocompatibility and biological function to a variety of polymers used in medical devices, without requiring expensive and toxic crosslinking reagents.