Quantitative electrical detection of immobilized protein using gold nanoparticles and gold enhancement on a biochip

• Published in: Measurement science & technology 2011-10, Vol.22 (10), p.105802-1-7
• Main Author: Lei, Kin Fong
• Format: Article
• Language: English
• Subjects: Antibodies; Biochips; Electrodes; Gold; Immunoassay; Indium tin oxide; Nanoparticles; Proteins
• ISSN: 0957-0233; 1361-6501
• DOI: 10.1088/0957-0233/22/10/105802

Electrical detection of the concentration of protein immobilized on a biochip is demonstrated. The concentration of the direct immobilized protein can be determined by the resistance values measured by an ohm-meter directly. Indium tin oxide interdigitated electrodes were utilized as the detection sites on the biochip. Protein, i.e. antibody, of certain concentration was first immobilized on the detection site. Gold nanoparticles were then applied to indicate the immobilized protein. Since the gold nanoparticles were tiny, a detectable electrical signal could not be generated. Hence, a gold enhancement process was performed for signal amplification. Gold nanoparticles were enlarged physically, such that a conductive metal layer was formed on the detection site. The presence and concentration of protein can be determined by the resistance value across the electrode measured by an ohm-meter. An immobilized protein concentration ranging from 50 to 1000 ng ml super(-1) can be detected quantitatively by the resistance values from 4300 to 1700 Omega . The proposed technique is potentially extended for the detection of immunoassay on the biochip. Since the protocol of the electrical detection does not involve sophisticated equipment, it can therefore be used for the development of a portable immunoassay device.