Abstract
A straightforward solution-based method to modify the biofunctionality of stainless steel (SS) using heterobifunctional silane-polyethylene glycol (silane-PEG) overlayers is reported. Reduced nonspecific biofouling of both proteins and bacteria onto SS and further selective biofunctionalization of the modified surface were achieved. According to photoelectron spectroscopy analyses, the silane-PEGs formed less than 10 Å thick overlayers with close to 90% surface coverage and reproducible chemical compositions. Consequently, the surfaces also became more hydrophilic, and the observed non-specific biofouling of proteins was reduced by approximately 70%. In addition, the attachment of E. coli was reduced by more than 65%. Moreover, the potential of the overlayer to be further modified was demonstrated by successfully coupling biotinylated alkaline phosphatase (bAP) to a silane-PEG-biotin overlayer via avidin-biotin bridges. The activity of the immobilized enzyme was shown to be well preserved without compromising the achieved antifouling properties. Overall, the simple solution-based approach enables the tailoring of SS to enhance its activity for biomedical and biotechnological applications.
Highlights
IntroductionEnzymes, such as lysozyme and alkaline phosphatase have been used to introduce antibacterial properties or other specific biological functions to surfaces[11,12]
In addition to surface biofunctionality, special care was placed on the extensive characterization of the surface with high resolution photoelectron spectroscopy methods complemented with imaging techniques
Since we have shown in Vuori et al.[12] that EC treatment generates a high-quality, reproducible and largely contaminant-free passivated surface and we have solid experience with the technique, EC treatment was selected as the surface pretreatment method to be used here
Summary
Enzymes, such as lysozyme and alkaline phosphatase have been used to introduce antibacterial properties or other specific biological functions to surfaces[11,12]. We report a simple and straightforward solution based method to deposit an extensive silane-PEG overlayer on an SS substrate to alter its biofunctionality. SS was electrochemically (EC) hydroxylated to ensure the presence of an extensive oxide layer This surface pretreatment is essential for the proper silanization of SS and imposes additional challenges and reaction steps when compared to, for example, the modification of more reactive and responsive silica[16,17] and glass surfaces[18,19]. The extent of modifications was assessed with various surface sensitive techniques, the antifouling properties with protein adsorption and bacterial adhesion tests, and the achieved biofunctionality with spectroscopic enzyme activity assay[12]
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