Abstract
A new method is demonstrated for preparing antifouling and low nonspecific adsorption surfaces on poorly reactive hydrophobic substrates, without the need for energy-intensive or environmentally aggressive pretreatments. The surface-active protein hydrophobin was covalently modified with a controlled radical polymerization initiator and allowed to self-assemble as a monolayer on hydrophobic surfaces, followed by the preparation of antifouling surfaces by Cu(0)-mediated living radical polymerization of poly(ethylene glycol) methyl ether acrylate (PEGA) performed in situ. By taking advantage of hydrophobins to achieve at the same time the immobilization of protein A, this approach allowed to prepare surfaces for IgG1 binding featuring greatly reduced nonspecific adsorption. The success of the surface modification strategy was investigated by contact angle, XPS, and AFM characterization, while the antifouling performance and the reduction of nonspecific binding were confirmed by QCM-D measurements.
Highlights
Surfaces with antifouling properties find major application in the biomedical field, in particular where the reduction of nonspecific protein adsorption and cell adhesion is a necessary requirement, e.g., for prostheses and implantable devices to avoid effects such as inflammation and fibrosis.[1−5] The minimization of nonspecific binding is important, in biosensing applications since nonspecific adsorption may produce a false response, decreasing the detection specificity and sensitivity of a device.[6−8]the introduction of antifouling features through surface modification can be a significant challenge in the case of poorly reactive materials, like some of the most commonly used hydrophobic polymers (e.g., polyolefins, polystyrene, poly(dimethylsiloxane), or Teflon)
The ability of the modified hydrophobin Ini-HFBI to assemble at interfaces and reduce interfacial tension was investigated for protein aqueous solutions with different concentrations at the interface between water and decane, and the results were compared to those obtained with the wildtype protein HFBI (Figure 2, green curve)
After growth of poly(PEGA) the Water Contact Angle (WCA) changed to 66.5°, which is in reasonable accord with values previously reported for surfaces modified with poly(ethylene glycol) (PEG)-like acrylate polymers.[47]
Summary
The introduction of antifouling features through surface modification can be a significant challenge in the case of poorly reactive materials, like some of the most commonly used hydrophobic polymers (e.g., polyolefins, polystyrene, poly(dimethylsiloxane), or Teflon). Fast, and environmentally friendly means of achieving the modification of chemically inert surfaces is offered by hydrophobins, which are natural amphiphilic proteins produced by filamentous fungi.[9−11]. Thanks to their unique Janus-like structure, which features a hydrophobic patch composed by amino acids with hydrophobic side chains, these proteins can self-assemble spontaneously on hydrophobic surfaces from aqueous solutions and form robust monolayers which expose a reactive hydrophilic side.
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