Protein Adhesion on Atmospheric Plasma Deposited Quaternary Ammonium Salt Coatings

Abstract

This study investigates protein adhesion on nm thick helium atmospheric plasma deposited quaternary ammonium salt (QAS) coatings. The adhesion of the proteins BSA, IgG and Fg was evaluated on coated and uncoated silicon wafer substrates. This study was carried out in PBS solution, under flow conditions using ellipsometry. The QAS was found to exhibit a low level of solubility in PBS over time (approx. 2 nm / hour). On addition of both the IgG and Fg proteins, it was found that a protective protein layer of 7 and 2 nm respectively was formed, which prevented further dissolution of the QAS. In contrast the 1 nm thick BSA protein layer, which formed on the QAS, was insufficiently thick to prevent the slow dissolution of the salt. It was concluded that the charge and structure of the protein influences its adhesion on the QAS surface. IntroductionA key issue affecting the performance of medical devices in the body is protein adhesion. [1,2] This is because proteins dictate how the cell interacts with the device surface.[3] Although there is a degree of inconsistency within the literature as to the factors influencing protein adsorption on a surface, it is believed that chemical functionality and topography are important factors. [4] Amongst the techniques that have been investigated to alter the surfaces of polymers in order to modify protein adhesion have been micro patterning and monomer polymerisation by free radical solution, emulsion, grafting as well as plasma processes. [5][6][7][8][9] The focus of this study is to investigate how a plasma polymerised quaternary ammonium salt (QAS) coating deposited onto a silicon wafer substrate influences protein adhesion.Worldwide consumption of quaternary ammonium compounds is estimated to be approximately 700,000 tons per annum.[10] Applications of these salts vary from surfactants, corrosion inhibitors and pesticides to personal care products and fabric softeners. [10][11][12] QAS coatings were selected for this study as they have also been reported to exhibit anti-bacterial and anti-fungal properties. [13,14] QAS surfaces have been shown to exhibit a high positive charge density, which exerts a strong electrostatic interaction with negatively charged bacteria. [15] It is reported that after the microbial cell adsorbs onto the coating surface through electrostatic interactions, the alkyl chain of the QAS, if of sufficient length, penetrates the microbial cell wall. This can disrupt the cytoplasmic membrane and release toxins that lead to necrosis. It is suggested that positively charged surfaces can tightly bind the adsorbed microbial cells and prevent their subsequent growth and proliferation, including biofilm formation.[16]There have been relatively few reports on the interaction between QAS surfaces and proteins.There have also been some inconsistencies between the adhesion results obtained by different authors. [17][18][19] It has been shown that quaternary ammonium based polymer coatings provide effective resistance against the non-specific adsorption of proteins ...

Robust bio-inspired antibacterial surfaces based on the covalent binding of peptides on functional atmospheric plasma thin films

“…The same stabilising effect was reported in a recent article where a thin layer of protein (IgG and Fg) on the surface prevented the dissolution of the plasma polymerized layer. 48 Interestingly, in the case of a non-activated COOH functionalised layer with nisin immobilised on the surface, the lm behaviour was drastically different. Even if a small protecting effect was noticed, as it can be seen from the FT-IR spectra conrming the presence of both the layer and the peptide, the surface is not homogenous.…”