Graphene-based cholesterol sensor
doi:10.1038/nindia.2014.116 Published online 26 August 2014
Researchers have fabricated a sensitive sensor that can detect minute traces of cholesterol in human blood serum1. They made the sensor by modifying multilayered graphene sheets with a compound derived from sugar molecules. This sensor is potentially useful for measuring the levels of serum cholesterol. This is vital as higher levels of serum cholesterol increase the risk of cardiovascular diseases.
Existing cholesterol sensors employ expensive enzymes such as cholesterol oxidase. To develop a simple and cost-effective cholesterol sensor, the researchers fabricated a non-enzymatic sensor by modifying multilayered graphene sheets with beta-cyclodextrin, a large molecule made of sugar molecules. They then dipped this sensor in methylene blue solution, which caused methylene blue molecules to bind to cyclodextrin molecules attached to the surfaces of the graphene sheets.
To evaluate the cholesterol-sensing efficiency of the sensor, the researchers carried out electrochemical measurements while exposing the sensor to cholesterol solution. They found that cholesterol molecules replaced the methylene blue molecules, causing the methylene blue molecules to enter the solution, thereby increasing the current.
Increasing the cholesterol concentration caused more cholesterol molecules to replace methylene blue molecules, resulting in a higher increase in the current. The cholesterol molecules replaced the methylene blue molecules, because they had a higher affinity for cyclodextrin.
The researchers found that the sensor was able to detect cholesterol even in the presence of interfering biochemical that are usually present in human blood serum, such as salts, amino acids and lipids.
“The sensor could detect cholesterol at micromolar concentrations, retaining stability and sensitivity even after 100 cycles of electrochemical studies,” says Amitabha De, a senior author of the study.
1. Agnihotri, N. et al. Non-enzymatic electrochemical detection of cholesterol using β-cyclodextrin functionalized graphene. Biosens. Bioelectron. 63, 212–217 (2014)