Research Highlight

Sensor for kidney stone

doi:10.1038/nindia.2011.38 Published online 16 March 2011

New research has shown that a nanohybrid film made from multiwalled carbon nanotube and colloidal gold nanoparticles can detect the concentration of oxalic acid in biological samples. This could help make sensors to detect levels of oxalic acid in biological fluids during ailments such as urinary stone formation, renal impairment and some intestinal diseases.

Oxalic acid is of great importance in the food industry and in clinical analysis. But ingestion of large quantities of food rich in oxalic acid can cause loss of calcium in the blood as well as injury to the kidneys.

Existing sensors to measure the levels of oxalic acid have drawbacks such as lack of stability, high response time, and low reproducibility. To devise a better sensor, the researchers chose nanomaterials such as multiwalled carbon nanotube and colloidal gold nanoparticles.

They designed the sensor by smearing oxalate oxidase, an enzyme isolated from sorghum leaves, on gold nanoparticles and multiwalled carbon nanotubes attached to gold electrode. They tested its efficacy to detect levels of oxalic acid in human blood, urine and food stuff.

The sensor showed optimum response within seven seconds. This biosensor can be used 200 times over a period of 5 months. "It can also be used for evaluation of oxalic acid content in vegetables and fruits, which would guide urinary stone patients about their food consumption," says lead researcher C. S. Pundir from the Department of Biochemistry, M. D. University, Haryana, India.


  1. Pundir, S. C. et al. A novel amperometric biosensor for oxalate determination using multi-walled carbon nanotube-gold nanoparticle composite. Sensor. Actuator. B. Chem. doi: 10.1016/j.snb.2011.01.050 (2011)