Covalent Immobilization of β-Galactosidase onto a Gold-Coated Magnetoelastic Transducer via a Self-Assembled Monolayer: Toward a Magnetoelastic Biosensor

J. Christopher Ball, Libby G. Puckett, Leonidas G. Bachas

Research output: Contribution to journalArticle

13 Scopus citations


The enzyme β-galactosidase has been covalently immobilized onto a gold-coated magnetoelastic film via a self-assembled monolayer (SAM) of ω-carboxylic acid alkyl-thiol. Use of magnetoelastic transduction allows for the wireless monitoring of enzymatic activity through the associated change in the frequency and amplitude of magnetic fields. The formations of SAMs of 3-mercaptopropanoic acid and thioctic acid were monitored by magnetoelastic transduction. After coupling of β-galactosidase to the SAMs, the enzyme activity was monitored by using a substrate that forms an insoluble product upon action of the enzyme. Specifically, an indolyl galacto-pyranoside substrate was employed in conjunction with an azo dye as the precipitating system. The immobilized enzyme was evaluated and found to have an apparent Michaelis-Menten constant (KM) of 1.2 mM for the indolyl galactopyranoside. Calibration plots for both substrates and inhibitors were generated to establish the versatility of this sensing system. Kinetic parameters for nonprecipitating substrates were determined in conjunction with a precipitating enzymatic substrate by way of a competitive inhibition study using β-galactosidase attached to magnetoelastic strips. The methods developed within this work allow for the fabrication of wireless enzyme sensing systems, which can also be used as another means of screening for enzyme inhibitors.

Original languageEnglish (US)
Pages (from-to)6932-6937
Number of pages6
JournalAnalytical Chemistry
Issue number24
StatePublished - Dec 15 2003


ASJC Scopus subject areas

  • Analytical Chemistry

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