A point-of-care testing platform for non-enzymatic lactate determination

Lactate, a crucial metabolic indicator, plays a vital role in diagnostics and treatment monitoring. Current lactate analysis often relies on enzymatic methods, employed in both clinical analyzers and point-of-care testing (POCT) devices. While these enzymatic assays offer selectivity and sensitivity, they suffer from limitations including higher costs, shorter lifetime, and reduced stability, particularly impacting POCT applications. This work introduces a novel POCT platform for lactate determination, utilizing a non-enzymatic approach. This analytical system is based on the photoreduction of iron(III)-lactate complexes, followed by detection of the resulting iron(II) with Ferrozine. Miniaturization of the system was achieved through two key innovations. First, the entire analytical procedure is conducted on 6 mm diameter reaction disks fabricated from cellulose and glass microfiber filters, facilitating easy storage and disposal while minimizing reagent and sample consumption (a few microliters). Second, an optoelectronic photometric system, incorporating an RGB LED emitter and a photodiode detector, enables both photoreduction (using blue light) and detection of the Fe(II)-Ferrozine complex (using green light). This POCT platform allows for rapid lactate determination in cerebrospinal fluid within 50 s, with analytical parameters supporting sample dilution up to even 100-fold.