A chemically modified laser-induced porous graphene based flexible and ultrasensitive electrochemical biosensor for sweat glucose detection

Porous laser-induced graphene (LIG) is an attractive and promising carbon material for electrochemical applications because it can immobilize various proteins, such as enzymes, antibodies, and receptors. However, poor inherent electrical properties caused by low surface conductivity is still a critical drawback for various applications. Here, we have proposed a surface modification method for the LIG electrode using acetic acid treatment via facile and practicable dipping technique. This simple acetic acid treatment dramatically increased the ratio of carbon-carbon bonds which effectively increased conductivity and decreased sheet resistance. In other words, acetic acid additionally reduced carbohydrate functional groups. Importantly, these unique properties also facilitated the stable and uniform dispersion of highly catalytic Pt nanoparticles (PtNPs) on LIG by avoiding the concentration of electric field on nanoparticles that can cause aggregation during electrodeposition. Finally, chitosan-glucose oxidase (GOx) composite was successfully immobilized onto the LIG/PtNPs electrode to fabricate a sweat glucose biosensor. The as-prepared LIG/PtNPs electrode exhibited a high sensitivity of 4.622 μA/mM as well as an ultra-low limit of detection (signal to noise ratio is 3) which was less than 300 nM and dynamic linear range up to 2.1 mM. Furthermore, we tested the variation of blood glucose level before and after meal using the amperometric response of the sensor which demonstrates the commercial potential of this unique sweat glucose biosensor.