Abstract
This work reports a biosensor for monitoring xanthine for potential wound healing assessment. Active substrate of the biosensor has xanthine oxidase (XO) and horseradish peroxidase (HRP) physisorbed on a nanocomposite of multiwalled carbon nanotubes (MWCNT) decorated with gold nanoparticles (AuNP). The presence of HRP provided a two-fold increase in response to xanthine, and a three-fold increase in response to the nanocomposite. With a sensitivity of 155.71 nA μM−1 cm−2 the biosensor offers a detection limit of 1.3 μM, with linear response between 22 μM and 0.4 mM. Clinical sample analyses showed the feasibility of xanthine detection from biofluids in a lesion site due to diffusion of the analyte into surrounding biofluids. Higher concentrations by three-fold were observed from wound proximity, than away from injury, with an average recovery of 110%. Results show the feasibility of monitoring wound severity through longitudinal measurements of xanthine from injured vicinity.
Highlights
XO is an oxidoreductase enzyme with a cofactor, flavin adenine dinucleotide (FAD), that facilitates its oxidation to a terminal purine product, uric acid (UA)
XO has 2 molecules of FAD bridged by a pair of ferric mercaptide groups.[20]
The presence of a molybdenum cofactor in XO allows for the transfer of electrons in the oxidation pathway to convert to by-product H2O2
Summary
To cite this article: Sohini RoyChoudhury et al 2019 J. Biofluid sample studies from in and around the wound provided insights into the physiological concentrations of xanthine in and around an injury Such detection provides a potential noninvasive method for the quantification of lesion severity. Standard electrochemical characterizations were carried out in a classical three-electrode system consisting of SPCE, an external Ag/AgCl as reference electrode, and a Pt counter electrode This three-electrode system was tested in an electrochemical cell setup with a 3 mL electrolyte solution to assess the performance of the nanomaterial-enzyme functionalized electrode in different concentrations of xanthine at a pH of 7.8. The wound dressings were carefully cut to 5 cm × 5 cm, as shown, to extract the biofluid that diffused through the dressing Each of these samples were immersed in a NaOH solution prepared in DI water (pH 12) and incubated at 37°C for forty-five minutes. Assays for correlating concentrations of xanthine in the different samples were conducted using standard colorimetric assay protocol at 570 nm
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