Sensors to signal cell death
doi:10.1038/nindia.2013.34 Published online 11 March 2013
Researchers have designed new biosensors that can detect minute traces of cytochrome c (cyt-c), an iron-containing protein released inside cells during disease-induced cell death1. The biosensors will aid clinical diagnosis and therapy as cyt-c is released in various diseases such as acute myocardial infarction, fulminant hepatitis, brain injuries and brain damage induced by influenza.
Besides signaling cell death, cyt-c molecules transfer electrons from cytochrome-c reductase (CcR) to cytochrome-c oxidase during cellular respiration. In recent years, cyt-c has been found to be an excellent biomarker of cell death during disease. Existing techniques for detecting cyt-c are complex, time-consuming and expensive.
To develop a simpler technique, the researchers prepared two biosensors, separately laying CNT and amino-acid-coated gold nanoparticles (GNP) on polymer-modified platinum electrodes. On top of each biosensor, they smeared animal-derived CcR to which cyt-c can bind.
They then exposed both biosensors to solutions containing animal-derived cyt-c molecules at varying concentrations. At negative potentials, the CNT-based biosensor exhibited a nearly two-fold increase in current and a four-fold increase in sensitivity relative to the GNP-based biosensor.
Previous studies have shown that doxorubicin-treated cancer cells undergo controlled cell death and release cyt-c into the cytoplasm. When exposed to doxorubicin-treated lung cancer cells, the CNT-based biosensors successfully detected cyt-c in dying cancer cells. The biosensor selectively detected cyt-c even in the presence of interfering agents and were stable for at least four weeks.
"These hand-held biosensors are cost effective," says lead researcher Chandran Karunakaran.