doi:10.1038/nindia.2011.115 Published online 10 August 2011
Researchers have designed a novel cholesterol sensor by modifying gold nanoparticles (GNPs) with a plant-derived chemical. The sensor could be useful in measuring blood cholesterol.
Given the role of cholesterol in the initiation and progression of heart diseases, researchers are always on the lookout for an effective cholesterol sensor. Enzyme-based sensors are capable of detecting cholesterol in blood and food. However, there is no sensor that employs naturally occurring molecules.
To devise such a sensor, the researchers chose to use digitonin, an organic compound found in plants. They modified GNPs with mercaptohexadecanoic acid (MHDA) and attached digitonin to them creating digitonin GNPs (DGNPs). The efficacy of DGNPs in detecting cholesterol was tested using varying concentrations of cholesterol.
Adding cholesterol to the DGNPs caused the absorption spectrum to shift towards blue wavelengths — a manifestation of the decrease in the particle size upon cholesterol binding. This happens as hydrophobic cholesterol expels water molecules from the surface of DGNPs.
The size of the DGNPs reduced from 28 nm to 20 nm when various cholesterol concentrations were added. The researchers also tested the selective binding of the DGNPs to cholesterol in the presence of other steroids such as testosterone, corticosterone and hydrocortisone. The data suggested that the DGNPs had more affinity towards cholesterol than other steroids. The sensor showed a cholesterol detection limit of 100 ng/ml.
"The method may be used for the detection of cholesterol present in free form," says lead researcher K. Sreenivasan. Compared with enzyme-based cholesterol sensors, this method is relatively simple, sensitive and easy to use, he adds.
The authors of this work are from: Sree Chitra Tirunal Institute for Medical Sciences and Technology, Trivandrum, India, and Nanosciences and Institut des Sciences Moleculaires, University of Bordeaux, France.