Efficient in situ growth of enzyme-inorganic hybrids on paper strips for the visual detection of glucose

A visual colorimetric microfluidic paper-based analytical device (μPAD) was constructed following the direct synthesis of enzyme-inorganic hybrid nanomaterials on the paper matrix. An inorganic solution of MnSO₄ and KH₂PO₄ containing a diluted enzyme (glucose oxidase, GOx) was subsequently pipetted onto cellulose paper for the in situ growth of GOx@Mn₃(PO₄)₂ hybrid functional materials. The characterization of the morphology and chemical composition validated the presence of hybrid materials roots in the paper fiber, while the Mn₃(PO₄)₂ of the hybrid provided both a surface for enzyme anchoring and a higher peroxidase-like catalytic activity as compared to the Mn₃(PO₄)₂ crystal that was synthesized without enzyme modulation. This new approach for the in situ growth of an enzyme-inorganic hybrid on a paper matrix eliminates centrifugation and the dry process by casting the solution on paper. The sensing material loading was highly reproducible because of the accuracy and stability of pipetting, which eventually contributed to the reliability of the μPAD. The self-assembled natural and artificial enzyme hybrid on the μPADs specifically detected glucose from a group of interferences, which shows great specificity using this method. Moreover, the colorimetric signal exhibited detection limitation for glucose is 0.01mM, which lies in the physiological range of glucose in biological samples.