Realization and Characterization of Porous Gold for Increased Protein Coverage on Acoustic Sensors

• Published in: Analytical chemistry (Washington) Vol. 76; no. 15; pp. 4299 - 4306
• Main Authors: Bonroy, Kristien, Friedt, Jean-Michel, Frederix, Filip, Laureyn, Wim, Langerock, Steven, Campitelli, Andrew, Sára, Margit, Borghs, Gustaaf, Goddeeris, Bruno, Declerck, Paul
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2004
• Subjects: Acoustics; Adsorption; Analytical chemistry; Bacillus; Bacterial Proteins; Biological and medical sciences; Biosensors; Biotechnology; Chemistry; Electrochemical methods; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Gold; Indicators and Reagents; Methods. Procedures. Technologies; Monosaccharide Transport Proteins; Porosity; Protein Binding; Proteins; Quartz; Surface Properties; Various methods and equipments; Cyclic voltammetry; Scanning electron microscopy; Gold; Adsorption; Biosensor; Electrochemical coating; Alkanethiol; Acoustic sensor; Porous material; Immunosensor; Protein; Quartz microbalance
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac049893u

Immunosensors show great potential for the direct detection of biological molecules. The sensitivity of these affinity-based biosensors is dictated by the amount of receptor molecules immobilized on the sensor surface. An enlargement of the sensor area would allow for an increase of the binding capacity, hence a larger amount of immobilized receptor molecules. To this end, we use electrochemically deposited “gold black” as a porous sensor surface for the immobilization of proteins. In this paper, we have analyzed the different parameters that define the electrochemical growth of porous gold, starting from flat gold surfaces, using different characterization techniques. Applied potentials of −0.5 V versus a reference electrode were found to constitute the most adequate conditions to grow porous gold surfaces. Using cyclic voltammetry, a 16 times increase of the surface area was observed under these electrochemical deposition conditions. In addition, we have assessed the immobilization degree of alkanethiols and of proteins on these different porous surfaces. The optimized deposition conditions for realizing porous gold substrates lead to a 11.4-fold increase of thiol adsorption and a 3.3-fold increase of protein adsorption, using the quartz crystal microbalance (QCM-D) as a biological transducer system. Hence, it follows that the high specific area of the porous gold can amplify the final sensitivity of the original flat surface device.