No sweat: Biosensors for easier testing

A new flexible, wearable biosensor can detect very low levels of glucose in body fluids such as sweat, saliva and tears. The biosensor may remove the need for blood tests via painful finger-pricks.  

It can be embedded into wearable items, such as contact lenses and smart watches, to constantly monitor glucose levels in diabetics, as well as in healthy people. The sensor, which retains its sensitivity even when bent, was developed by Saudi and US researchers, led by KACST affiliated  Moh R. Amer.     

Wearable sensors could be very useful for people with diseases that require regular checks. Current versions are not sensitive enough to measure glucose in body fluids other than blood, and some stop working if they are bent.   

The biosensor was made using nanoribbons of indium oxide, metal electrodes, and a coat of ink containing chitosan, glucose oxidase enzyme and single-walled carbon nanotubes.  

The enzyme in the sensor interacts with glucose, setting off reactions that ultimately generate an electrical signal that reveals a specific glucose concentration. Experiments showed that the sensor is sensitive enough to measure a wide range of glucose concentrations, from 10nanomolars to 1 millimolar.  

The researchers attached a tiny well to the sensor to test its ability to detect glucose in a very small volume of body fluid.  The sensor was able to generate an electrical signal when the micro-well was filled with only 10 microlitres of solution.  

It also managed to detect glucose concentrations in artificial tears when it was attached to an artificial eyeball, and efficiently identified glucose levels in human sweat samples before and after a meal. Bending the sensor 100 times didn’t noticeably affect its performance.  

“Given the facile and highly scalable fabrication process, low driving voltage, and reliable sensing behaviour even when deformed, this sensing platform is promising for continuous personalized health monitoring, for the food industry, and for environmental monitoring,” report the researchers in their study, published in the journal ACS Nano. 

1. Liu, Q., Liu, Y., Wu, F., Cao, X., Li, Z. et al. Highly sensitive and wearable In₂O₃ nanoribbon transistor biosensors with integrated on-chip gate for glucose monitoring in body fluids. ACS Nano 12, 1170-1178 (2018).  | article