doi:10.1038/nindia.2014.67 Published online 21 May 2014
Researchers have developed a sensor that can detect minute traces of Streptococus pyogenes, a bacterium that causes rheumatic heart disease1. This sensor could potentially be used for diagnosing this heart disease.
The bacterium S. pyogenes initially infects the throat and then migrates to the heart where bacterial proteins interact with heart proteins damaging the heart valves. This leads to the onset of rheumatic heart disease. Existing techniques for detecting S. pyogenes are time consuming and insensitive.
The researchers fabricated the sensor by modifying a gold electrode with mercaptopropionic acid and polyethylenimine. They then attached a virulent gene found in bacteria like S. pyogenes to the modified gold electrode. This virulent gene can bind to the DNA of S. pyogenes. They tested the efficacy of this sensor in detecting S. pyogenes by exposing it to solutions containing S. pyogenes DNA isolated from throat swabs of patients afflicted with rheumatic heart disease.
The researchers carried out electrochemical studies using the sensor. They found that the peak current of the sensor increased with increasing concentration and binding of S. pyogenes DNA. The sensor was able to detect S. pyogenes DNA at picogram concentrations in 30 minutes.
The sensor selectively detected S. pyogenes even in the presence of other pathogens that usually infect humans. In addition, the sensor demonstrated good stability over 6 months, with only a 10 per cent reduction in efficiency over this time. “This sensor is faster than conventional ones, facilitating early diagnosis of rheumatic heart disease. It could also be used for detecting other infectious diseases by modifying the probe molecules attached to the sensor,” says Ashok Kumar, a senior author of the study.
1. Singh, S. et al.Gold/mercaptopropionic acid/polyethylenimine composite based DNA sensor for early detection of rheumatic heart disease. Analyst (2014) doi: 10.1039/C4AN00324A