A homocysteine biosensor with eggshell membrane as an enzyme immobilization platform

A low-cost and simple biosensing method for screening homocysteine in human plasma has been developed. The biosensor was fabricated from a d-amino acid oxidase immobilized eggshell membrane and an oxygen electrode. The effects of enzyme loading, glutaraldehyde concentration, pH, ionic strength, and temperature on the response of the biosensor have been investigated in detail. The sensing method is based on monitoring the decrease in the dissolved oxygen level of the sample solution. The linear working range was 0.05–1.5 mM and the limit of detection was 30 μM. The proposed biosensor shows fast response time (<1 min), good repeatability (n = 6, relative standard deviation = 2.38%), and long-term stability (85% of its initial sensitivity after 2 months of storage).