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Direct Determination of a Small-Molecule Drug, Valproic Acid, by an Electrically-Detected Microcantilever Biosensor for Personalized Diagnostics

Institute of Applied Mechanics, National Taiwan University, Taipei 10617, Taiwan
Department of Chemical Physics, Weizmann Institute of Science, 234 Herzl Street, Rehovot 7610001, Israel
Author to whom correspondence should be addressed.
Academic Editor: Andrew Shaw
Biosensors 2015, 5(1), 37-50;
Received: 14 November 2014 / Revised: 17 December 2014 / Accepted: 21 January 2015 / Published: 27 January 2015
(This article belongs to the Special Issue Label-Free Biosensors: Exploring the Field)
PDF [639 KB, uploaded 27 January 2015]


Direct, small-molecule determination of the antiepileptic drug, valproic acid, was investigated by a label-free, nanomechanical biosensor. Valproic acid has long been used as an antiepileptic medication, which is administered through therapeutic drug monitoring and has a narrow therapeutic dosage range of 50–100 μg·mL1 in blood or serum. Unlike labeled and clinically-used measurement techniques, the label-free, electrical detection microcantilever biosensor can be miniaturized and simplified for use in portable or hand-held point-of-care platforms or personal diagnostic tools. A micromachined microcantilever sensor was packaged into the micro-channel of a fluidic system. The measurement of the antiepileptic drug, valproic acid, in phosphate-buffered saline and serum used a single free-standing, piezoresistive microcantilever biosensor in a thermally-controlled system. The measured surface stresses showed a profile over a concentration range of 50–500 μg·mL1, which covered the clinically therapeutic range of 50–100 μg·mL1. The estimated limit of detection (LOD) was calculated to be 45 μg·mL−1, and the binding affinity between the drug and the antibody was measured at around 90 ± 21 μg·mL1. Lastly, the results of the proposed device showed a similar profile in valproic acid drug detection with those of the clinically-used fluorescence polarization immunoassay. View Full-Text
Keywords: valproic acid; microcantilever; serum; therapeutic drug monitoring valproic acid; microcantilever; serum; therapeutic drug monitoring

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Huang, L.-S.; Gunawan, C.; Yen, Y.-K.; Chang, K.-F. Direct Determination of a Small-Molecule Drug, Valproic Acid, by an Electrically-Detected Microcantilever Biosensor for Personalized Diagnostics. Biosensors 2015, 5, 37-50.

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