Xanthine oxidase functionalized Ta2O5 nanostructures as a novel scaffold for highly sensitive SPR based fiber optic xanthine sensor

- Novel scheme for xanthine detection using xanthine oxidase (XO) entrapped Ta2O5 nanofibers is presented.
- The probe is prepared by coating a layer of XO entrapped Ta2O5 nanofibers over silver coated unclad core of the optical fiber.
- The performance of the probe is compared with probes prepared using various other XO entrapped Ta2O5 nanostructures.
- The limit of detection of the sensor outperforms previously reported ones.
- The sensor has been tested successfully for xanthine detection in green tea samples.

Fabrication and characterization of a surface plasmon resonance based fiber optic xanthine sensor using entrapment of xanthine oxidase (XO) enzyme in several nanostructures of tantalum (v) oxide (Ta2O5) have been reported. Chemical route was adopted for synthesizing Ta2O5 nanoparticles, nanorods, nanotubes and nanowires while Ta2O5 nanofibers were prepared by electrospinning technique. The synthesized Ta2O5 nanostructures were characterized by photoluminescence, scanning electron microscopy, UV-Visible spectra and X-ray diffraction pattern. The probes were fabricated by coating an unclad core of the fiber with silver layer followed by the deposition of XO entrapped Ta2O5 nanostructures. The crux of sensing mechanism relies on the modification of dielectric function of sensing layer upon exposure to xanthine solution of diverse concentrations, reflected in terms of shift in resonance wavelength. The sensing probe coated with XO entrapped Ta2O5 nanofibers has been turned out to possess maximum sensitivity amongst the synthesized nanostructures. The probe was optimized in terms of pH of the sample and the concentration of XO entrapped in Ta2O5 nanofibers. The optimized sensing probe possesses a remarkably good sensitivity of 26.2 nm/µM in addition to linear range from 0 to 3 µM with an invincible LOD value of 0.0127 µM together with a response time of 1 min. Furthermore, probe selectivity with real sample analysis ensure the usage of the sensor for practical scenario. The results reported open a novel perspective towards a sensitive, rapid, reliable and selective detection of xanthine.