Fig. 6 Glucose detection with enzyme-loaded microfibers. (a)
The effect of HRP/GOX weight ratio on the absorption of mixture of
glucose and TMB after catalysis with HRP and GOX-loaded microfibers. (b)
The effect of glucose concentration on the absorption of the aqueous
solution containing enzymes, glucose, and TMB. (c) Visual detection of
glucose (0, 0.25, 0.5, 1, 2 mM) with enzymes and TMB-loaded microfibers.
Prior to the glucose analysis with microfibers, the chromogenic reaction
in aqueous solution were investigated at selected concentrations of
glucose (Fig. 6b ). Data showed that the absorption (652 nm) of
the mixture increased with glucose concentration. But the relationship
between the absorption and the concentration was not linear in the
selected range of glucose concentration. The slope of the curve was
smaller when the glucose concentration was higher than 2 mM, indicating
that the color change was less sensitive to glucose with too high
concentrations. For visual detection of glucose, microfibers with
enzymes and TMB were fabricated under the optimal conditions and wrapped
on a glass slide (Fig. 6c ). The aligned fibers turned to blue
after dropwise adding with 20 μL of glucose solution. The blue color
remarkably became deeper with the increase of glucose concentration from
0 to 2 mM. The catalysis reaction was triggered by the addition of
glucose and the penetration into the pores of the hydrogel network
followed by the rapid generation of OxTMB, which causes the visible blue
color in the microfibers. The knittability and the modulability in the
composition and size enabled great potentials of the microfluidic
microfibers in the construction of portable devices for the simultaneous
detection of multiple markers.