Microfluidic multiplex biochip based on a point-of-care electrochemical detection system for matrix metalloproteinases

• We propose a biosensor detecting MMP7 and MMP2 for cancer diagnosis.
• The multiplex biochip is a simple 2-electrode electrochemical POCT microdevice.
• Hydrolysis action with an unmodified peptide is adapted for MMP detection.
• Negative controls and a microfluidic mixer are used to enhance the performance.
• Concentrations of MMP2 and MMP7 are detected well concurrently.

Conventional cancer diagnostic techniques are not suitable for point-of-care testing because they are usually expensive, time consuming, labor intensive, and require large equipment. This paper presents a proof-of-concept biochip for point-of-care testing based on multiplex electrochemical detection. The microfluidic biochip is composed of inexpensive photoresist–polydimethylsiloxane layers over a glass substrate. The substrate has an Au working electrode and a Pt counter/reference electrode. A microchannel was fabricated in the photoresist layer and a micromixer was fabricated in the polydimethylsiloxane layer. Matrix metalloproteinases (MMPs) 2 and MMP7 are used as biomarkers for ovarian and colorectal cancer diagnosis. An unlabeled peptide specific to MMPs is immobilized on an Au electrode and then impedance was measured using electrochemical impedance spectroscopy with electrolytes. As the MMP sample is injected into the biochip, the peptide is cleaved by enzyme hydrolysis and the impedance changes. MMP2 and MMP7 are quantitatively detected concurrently by measuring the variations of impedance. Using model samples, the detection ranges of the biochip were 0.1–400 ng/mL and 0.001–100 ng/mL for MMP2 and MMP7, respectively, and the overall assay time was reduced to about 1 h. The results indicate that a similar MMP-based electrochemical multiplex biochip could be used for the point-of-care diagnosis of many forms of cancer.