“Ready-to-use” hollow nanofiber membrane-based glucose testing strips

A novel “ready-to-use” glucose test strip based on a polyurethane hollow nanofiber membrane was fabricated through facile co-axial electrospinning. By utilizing glucose oxidase and horseradish peroxidase in the core-phase solution, and a chromogenic agent either in the core solution (in which case 2,2’-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) was used) or in the shell-phase solution (in which case o-dianisidine was used) for co-axial electrospinning, in situ co-encapsulation of the two enzymes within the hollow nano-chamber and incorporation of chromogenic agents either inside the nano-chamber or in the shell of the hollow nanofibers was realized. Such unique “all-in-one” feature enabled the prepared hollow nanofiber membrane-based test strips to be applied either as colorimetric sensors in solution or as an optical biosensor operated in the “dip-and-read” mode. When used as a colorimetric biosensor in solution, the test strip with o-dianisidine as chromogenic agent shows an excellent linear response range between 0.01 mM to 20 mM and a high apparent lumped activity recovery of 62.1% as compared to the reaction rate of the free bi-enzyme system. While the activity recovery of the test strip with ABTS as chromogenic agent is only 18.0%, and the test strip is found to be unstable due to spontaneous-oxidation of the ABTS. The o-dianisidine test strip was also applied as an optical biosensor, visible rufous color was quickly developed on the surface of the membrane upon dropping 10 ¼L of glucose sample, and an excellent correlation between differential diffusive reflectance of the test strip at 440 nm and glucose concentration was obtained in the range of 0.5-50 mM. The test strips also exhibited excellent long-term storage stability with a half-life at 25 °C as long as four months.