Laser-Induced Graphene Decorated with Platinum Nanoparticles for Electrochemical Analysis of Saliva

Abstract

Saliva-based sensors are becoming increasingly important in medical diagnostics and sports medicine due to the plethora of biomedically relevant analytes found endogenously within the fluid and to the inherently noninvasive nature of the sensing protocols. Salivary lactate and potassium have been shown to be key indicators for monitoring fatigue, hydration, and overall health, and frequent monitoring is crucial for preventative treatment strategies. Low-cost test strip sensors combined with saliva swab sampling could enable such frequent monitoring, and to this end, we developed amperometric lactate and coulometric potassium test strip sensors using laser-induced graphene (LIG), a low-cost scalable fabrication method for graphene sensor development. To increase the sensitivity of the sensors, platinum nanoparticles (nPt) were deposited on the LIG surface by using a facile electroless deposition method. Subsequently, a redox mediator with the enzyme lactate oxidase was used for lactate sensing, while a polymer-based ion-selective membrane was used for potassium sensing. The lactate biosensor displayed a sensitivity of 33.3 ± 0.9 μA mM–1 cm–2 and a limit of detection (LOD) of 0.10 ± 0.06 mM, while the potassium sensor exhibited a sensitivity of 168.2 μC dec–1 and a signal-to-noise ratio (S/N) of 193.3 ± 56.2. Both sensors were capable of selectively sensing within the physiologically relevant range with real pooled saliva samples. Such sensing results demonstrate the potential of nPt-LIG for point-of-care biosensors for personalized health and athletic performance monitoring.