Protein immobilization at gold–thiol surfaces and potential for biosensing

Abstract

Self-assembled monolayers (SAMs) provide a convenient, flexible and simple system to tailor the interfacial properties of metals, metal oxides and semiconductors. Monomolecular films prepared by self-assembly are attractive for several exciting applications because of the unique possibility of making the selection of different types of terminal functional groups and as emerging tools for nanoscale observation of biological interactions. The tenability of SAMs as platforms for preparing biosurfaces is reviewed and critically discussed. The different immobilization approaches used for anchoring proteins to SAMs are considered as well as the nature of SAMs; particular emphasis is placed on the chemical specificity of protein attachment in view of preserving protein native structure necessary for its functionality. Regarding this aspect, particular attention is devoted to the relation between the immobilization process and the electrochemical response (i.e. electron transfer) of redox proteins, a field where SAMs have attracted remarkable attention as model systems for the design of electronic devices. Strategies for creating protein patterns on SAMs are also outlined, with an outlook on promising and challenging future directions for protein biochip research and applications.

The Effect of Particle Size on the Direct Electron Transfer Reactions of Metalloproteins Using Au Nanoparticle-Modified Electrodes

“…To study the DET reaction of cyt c, 11-MUA was used because cyt c is electrostatically immobilized on a SAM of carboxylic acid-terminated alkanethiols via lysine residues. 13 A pair of redox peaks for cyt c were observed for all of the electrodes. The surface coverage (! )…”

“…SAM-modified electrodes can be used to immobilize proteins with the appropriate orientation on the electrode surface. 13 In our previous studies, the surface coverage of redox-active cytochrome c (cyt c) on AuNPmodified electrodes was 167 times higher than the roughly estimated monolayer coverage of 15 pmol cm ¹2 . The current density for the oxidation of D-fructose using D-fructose dehydrogenase (FDH) immobilized on AuNP-modified electrodes reached 14.3 mA cm ¹2 in the presence of 200 mM D-fructose.…”

Optically excited nanoscale ultrasonic transducers

“…SAM layers are a versatile coating as there is a wide variety of terminating functional groups which can be used to interact with a large number of molecules. This allows the SAM to 31 or a smart surface having the initial surface properties of the formed film which changes in response to an external stimulus, e.g., chemical, optical, electric, or thermal. 32 …”

Nanostructured interfaces with site-specific bioreceptors for immunosensing

“…Using alkanethiol molecules, highly organized and stable platforms with reproducibility and easy preparation can be developed [2][3][4]. Moreover, alkanethiol molecules containing terminal functional groups, such as carboxylic acid moieties, are suit-able to covalently immobilize proteins [5][6][7][8]. However, this method requires the incorporation of an activation step, usually performed with N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), to attach the protein to the SAM [8][9][10].…”