A contact lens with an integrated lactate sensor

The tear film is a valuable diagnostic fluid for a continuous, minimally invasive surveillance of health conditions in a patient. We developed an electronic enzymatic l-lactate sensor on a polymer substrate molded into contact lens shape for potential in situ monitoring of l-lactate levels in tear fluid. The platinum sensing structures were functionalized by cross-linkage of lactate oxidase with glutaraldehyde and bovine serum albumin, and coated with medical grade polyurethane. Different approaches for the suppression of interfering species present in the tear film were evaluated. The sensors show a quick response time of 35 s, an average sensitivity of ∼53 μA mM−1 cm−2 within their linear range, and sufficient resolution within the physiological range of lactate concentrations. A dual sensor design was found appropriate for the suppression of interfering signals. The sensors are functional at temperatures comparable to those at the surface of the eye, and their response is stable for up to 24 h.