Biocompatible enzymatic roller pens for direct writing of biocatalytic materials: "do-it-yourself" electrochemical biosensors.

The development of enzymatic-ink-based roller pens for direct drawing of biocatalytic sensors, in general, and for realizing renewable glucose sensor strips, in particular, is described. The resulting enzymatic-ink pen allows facile fabrication of high-quality inexpensive electrochemical biosensors of any design by the user on a wide variety of surfaces having complex textures with minimal user training. Unlike prefabricated sensors, this approach empowers the end user with the ability of "on-demand" and "on-site" designing and fabricating of biocatalytic sensors to suit their specific requirement. The resulting devices are thus referred to as "do-it-yourself" sensors. The bio-active pens produce highly reproducible biocatalytic traces with minimal edge roughness. The composition of the new enzymatic inks has been optimized for ensuring good biocatalytic activity, electrical conductivity, biocompati-bility, reproducible writing, and surface adherence. The resulting inks are characterized using spectroscopic, viscometric, electrochemical, thermal and microscopic techniques. Applicability to renewable blood glucose testing, epidermal glucose monitoring, and on-leaf phenol detection are demonstrated in connection to glucose oxidase and tyrosinase-based carbon inks. The "do-it-yourself" renewable glucose sensor strips offer a "fresh," reproducible, low-cost biocatalytic sensor surface for each blood test. The ability to directly draw biocatalytic conducting traces even on unconventional surfaces opens up new avenues in various sensing applications in low-resource settings and holds great promise for diverse healthcare, environmental, and defense domains.