JOIN USNovel biosensors for easier diagnostics
In ancient times, doctors relied primarily on close observation of various symptoms in patients, in order to diagnose a disease. However, the rapid increase of population as well as the complexity of diseases in modern times has led to the invention and design of high-end technology for diagnostic tools that assist in accurate and timely diagnosis of diseases.
Biosensors constitute a class of devices which are capable of detecting and analysing biological samples, for example, enzymes, proteins, viruses, blood, glucose, etc., in order to gain an insight into their bio-composition, structure and function. This is achieved by converting a biological response into an electrical signal.
Biosensors can be broadly divided into six groups: optical, mass, electrochemical, magnetic, micromechanical and thermal. In 1962, Professor Leland C Clark developed the first and the most widely used commercial biosensor, ‘the blood glucose biosensor’. Since then, the field of biosensors has evolved tremendously with the global biosensor market predicted to be worth 22,490 million dollars by the year 2020.
Researchers have realised the importance of portable, accurate, low cost and user-friendly biosensors in the medical field. Developing a biosensor requires expertise in several disciplines ranging from physics, chemistry and biology to electronics and engineering.
Better results
A team of researchers at the Indian Institute of Science (IISc), Bengaluru, is developing biosensors that detect breathing problems. Here is the science behind it: An obstruction in the nasal pathway can lead to irregular breathing. An early detection of nasal blockage can save us the trouble of future complications. Professor Rajanna with his team at the department of Instrumentation and Applied Physics (IAP) has developed a biosensor known as the ‘breath sensor’ that addresses this issue. They have collaborated with Professor Roy Mohapatra & team from the Department of Aerospace Engineering and Dr Surya Prakash, an ENT surgeon at MS Ramaiah Medical College and Hospital, Bengaluru, for this work.
The air flow through both the nostrils in a healthy human being is expected to be identical. A deformation in the nasal cavity hinders normal breathing. Conventional tools for detecting such abnormalities are expensive, require skilled operators and are not portable. The sensor developed by this team addresses all these issues. It uses a polymer, suitable for the body, which produces an electrical output when breathed upon. The device was tested on 25 patients and compared with 25 healthy subjects, following which it showed a high level of accuracy.
A protein, called the ‘C-reactive protein (CRP),’ which is present in the blood, is produced in higher concentration in the presence of an infection. A concentration above 3 mg/ml is associated with cardiovascular disease. A sensor to detect the rise in concentration of CRP is of utmost importance in order to prevent heart attacks and other heart-related diseases.
A second research team at IISc has developed a light-based highly accurate and sensitive CRP sensor. The team, headed by professors S Asokan and Ajay Sood, has attached a CRP antibody (a biomolecule that binds with CRP) with graphene oxide, a material commonly found in a pencil lead. This is then coated on optical fibres, which are widely used in light-based communication. Depending on the amount of CRP that comes in contact with these optical fibres, the light output from the fibre varies, which in turn helps in measuring the concentration of CRP in the blood.
The device has such a high sensitivity that the group was able to successfully measure even a very low concentration of about 0.1 mg/ml. Compared with existing techniques, their results are reproducible and free of any interference from other biomolecules.
Analysing behaviour
According to the World Health Organisation (WHO), nearly 2.5 million people tested HIV positive and 3.5 million were suffering from Tuberculosis (TB) in the year 2011. AIDS and TB are two of the foremost causes of death worldwide. A research team, headed by Associate Professor Amit Singh at the Department of Molecular Biology is designing biosensors which will aid in the early detection of AIDS and TB.
AIDS is caused by the Human Immunodeficiency Virus (HIV), which can remain dormant in the human body for years until it is reactivated by a trigger. The biosensor developed detects the level of this triggering agent. This will shed light on the physiological change in the HIV infected cell and thus, assist in the prediction of drug action on such cells. This breakthrough could help in developing drugs for treatment of HIV.
“Importantly, we also discovered that Mycobacterium tuberculosis (Mtb), another major human pathogen that specifically disturbs glutathione balance to increase the replication of HIV. Since TB is the major cause of HIV-related deaths, our findings have major mechanistic and therapeutic potential for both TB and AIDS,” said Professor Amit.
Most HIV related deaths occur due to secondary infection by the Mtb bacteria. Like the HIV virus, Mtb bacteria can stay dormant for years. Moreover some strains of Mtb are drug resistant. Amit’s lab has developed a bio-marker, a kind of protein, which distinguishes between the drug resistant strain of Mtb and the strains which are susceptible to drugs.
“One of the major reasons as to why researchers have time and again failed to identify new anti-TB drugs is because they have been testing the drug in test tubes. But the macrophage’s environment is very complex, and therefore cannot be mirrored in a test tube,” explains Professor Amit. The bio-marker developed by his team tackles this problem.