Nano Lett. 14, 3587–3593 (2014)

Credit: © 2014 ACS

An international team of scientists in the UK, USA, Brazil and Australia has demonstrated a photonic nanosensor that is promising for point-of-care screening of diabetes and diagnosis of urinary tract infections. The nanosensor can be easily and rapidly fabricated by using a 6 ns laser pulse (wavelength, 532 nm) to produce a Bragg diffraction grating consisting of silver nanoparticles distributed within a hydrogel. The presence of glucose causes the hydrogel to swell, thereby modulating the spacing of the silver-nanoparticle distribution as well as the refractive-index contrast between the nanoparticles and the hydrogel. These changes systematically shift diffracted light to longer wavelengths as the glucose concentration rises; the nanosensor operates over the wavelength range 510–1,100 nm. Furthermore, the nanosensor can be reused at least 400 times without affecting its accuracy. Readouts can be obtained within 5 min, and the sensor can be reset in about 10 s. In terms of diagnosing glycosuria from urine samples, the authors claim that the nanosensor exhibited superior performance to commercial glucose test strips and equivalent performance to fully automated analysers.