- Sepsis is a blood infection caused by circulating pathogens and cell wall fragments that affects over 1 million patients per year in the United States. When bacterial cell membranes are lysed by antibiotics, cell wall fragments containing lipopolysaccharides (LPS) are released. As a result, the capture of LPS is critical to the treatment of sepsis, otherwise bodily immune responses may be triggered from higher toxin concentrations. Hemoperfusion devices are an alternative treatment for sepsis that remove toxins extracorporeally from blood. Our lab is currently working on a hemoperfusion device that exhibits non-fouling and bacterial capturing properties for the treatment of sepsis. We address the concerns of fouling, or non-specific adsorption, by using a dense polyethylene oxide (PEO) pendant brush layer. In this study, we look at different molecular weight polybutadiene-polyethylene oxide (PBD-PEO) diblocks and quantify the amount of fibrinogen repelled into solution by solution depletion and QCMD analysis. Results show that lower molecular weight diblocks have a higher repulsion, presumably due to higher surface coverage density. We also use QCMD and solution depletion to test the endotoxin capture of native bacterial tail spike protein GP34, which is known to bind to the O-antigen in LPS, and mutant azide-GP34 (modified with 4-azido-L-phenylalanine at N17, R58, and L81). By incorporating a “click” ready unnatural amino acid into GP34 by Genetic Code Expansion, we are able to immobilize the proteins in a highly efficient and specific orientation, allowing for increased LPS capture compared to GP34 WT. N17 modified GP34 had an increased LPS capture compared to the WT protein due to the controlled immobilization orientation of the mutant protein. However, the GP34 modified at R58 and L81 showed a decrease capture of LPS, which indicates that the site-specific incorporation may be affecting the LPS binding motif or the immobilization produces a suboptimal orientation for endotoxin binding.