Human Serum Albumin Adsorption Study on 62-MHz Miniaturized Quartz Gravimetric Sensors

• Published in: Analytical chemistry (Washington) Vol. 80; no. 15; pp. 5930 - 5936
• Main Authors: Kao, Ping, Patwardhan, Ashish, Allara, David, Tadigadapa, Srinivas
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2008
• Subjects: Adsorption; Analytical chemistry; Aqueous solutions; Chemical and thermal methods; Chemistry; Electrodes; Exact sciences and technology; General, instrumentation; Humans; Methods; Miniaturization; Proteins; Quartz; Sensors; Serum Albumin - chemistry; Thermogravimetric analysis; Self-assembled layer; Performance evaluation; Human; Monolayer; Gravimetric analysis; Gold; Equilibrium constant; Adsorption isotherm; Serum albumin; Chemical sensor; Quartz; Buffer solution; Quartz resonator; Protein; Chemical enrichment; Sensitivity; Adsorption; Resonance frequency; Aqueous solution
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac8005395

We have designed and fabricated 25-μm-thick quartz resonators operating at a fundamental resonance frequency of ∼62 MHz. The results show a substantial increase in the mass sensitivity compared to single monolithic commercial resonators operating at lower frequencies in the ∼5−10-MHz range. The overall performance of the micromachined resonators is demonstrated for the example of human serum albumin protein adsorption from aqueous buffer solutions onto gold electrodes functionalized with self-assembled monolayers. The results show a saturation adsorption frequency change of 6.8 kHz as opposed to 40 Hz for a commercial ∼5-MHz sensor under identical loading conditions. From the analysis of the adsorption isotherm, the equilibrium adsorption constant of the adsorption of the protein layer was found to be K = 8.03 × 10^6 M^−1, which is in agreement with the values reported in the literature. The high sensitivity of the miniaturized QCM devices can be a significant advantage in both vapor and solution adsorption analyses.