Indian Innovators (9 page)

Priyanka Sharma

Ultra Low-Cost Immuno-sensor Biochip for Detecting Environmental Pollutants

Born to an engineer father and a homemaker mother, Priyanka was brought up in the HMT Colony near Chandigarh. Being the only child, she was a pampered kid and being a girl, her parents always wanted her to take up an easy job. Therefore, after completing her MSc degree, she joined a government college in Chandigarh as a lecturer and worked there for three years.

Though she enjoyed teaching, she developed a greater passion for research and decided to make a career in that area. She enrolled for a PhD program at Panjab University, but the lack of funds for research pushed her to explore more opportunities. So, she applied to the University Grants Commission’s (UGC) Junior Research Fellowships.

Through a very competitive process, she was selected to work at the Council of Scientific and Industrial Research’s (CSIR) Institute of Microbial Technology.

“The environment at CSIR is great for research – well- equipped laboratories, well-defined goals, adequate funding, and above all, very supportive and experienced researchers.”

Priyanka’s educational background was environment sciences, and that was her area of interest in research too. In her travels to rural Punjab from Chandigarh, she had often seen farmers work with pesticides, bare hands and barefooted, using no protective covering. “These are extremely dangerous compounds. Even when we handle them in the laboratory, we wear protective gloves and robes,” she explains.

She delves into little-known aspects of pesticide usage in India. “In our country, there are norms regarding phasing out pesticides, but there are no government regulations on monitoring their use and impact.

Therefore, a pesticide would be legally available only for about 10 years after its first introduction (as pests become resistant to it during this period). The companies would then introduce a new pesticide. Nobody would bother about the negative impact of the last pesticide, its concentration in water, soil or living beings, or how it should be handled to avoid human or environmental disaster. Thus, those who profit from the pesticide trade have no liability toward its harmful effects.”

This prompted Priyanka to work on detecting pesticide levels in the soil. “I joined research under Dr C Raman Suri, who had several years of research experience in biosensors and diagnostics. I decided to work on biosensors that can detect pesticide levels in soil and water.”

As Priyanka’s BSc and MSc degrees were in Environmental Science, she did not know about the biological sciences. It was quite intimidating for her to work with some of the best researchers in the field without adequate knowledge. Therefore, she had to work much harder in the first year to bridge the knowledge gap.

“Thanks to my guide, I could learn much faster than I thought, and by the end of the year, there was already good progress on the project.”

A European Union directive sets the maximum permissible limit for any individual pesticide in groundwater at 0.1ng/ml. At this low concentration, detection is quite difficult. Currently, various analytical techniques like gas chromatography (GC), high-pressure liquid chromatography (HPLC), capillary electrophoresis (CE) and mass spectrometry (MS) are used for this purpose. All these methods are complex and time consuming and require costly, bulky instrumentation. Moreover, preparing samples for these techniques is tedious and requires skilled personnel. For all these reasons, these techniques are unsuitable for field studies and
in situ
monitoring of samples.

Despite the need for an inexpensive, portable device that enables quick determination of pesticide levels for human health and agricultural management programs, little had been done on this front, prior to Priyanka’s work.

Priyanka explains her research methodology. “We tagged the pesticide (a popular phenyl-urea herbicide called Diuron, used worldwide with cotton crops) with a protein molecule and injected it into rabbits and chicken, in order to generate antibodies against it. The animals were injected three more times, with a gap of 21 days between two doses (technically referred to as ‘three boosters after the first immunization’). The antibodies formed were then extracted from the rabbit’s blood and the chicken’s egg yolk.

The antibodies were then characterized using the ELISA (Enzyme Linked Immunosorbent Assay, used to detect the presence of a substance in a liquid sample) technique. Characterization refers to whether the antibodies actually respond to the antigen (the external molecule that the antibody is supposed to act against) and to see how specific they are (whether they bind only to the antigen selectively or to a wide range of compounds). Characterization helps to ascertain whether the antibody will be able to associate with the antigen, even when the concentration of the antigen is low, or when there are several other potential molecules (impurities in the water sample) that can potentially compete with the antigen to react with the antibody.

We used the pesticide and the pesticide-protein conjugate for characterization. The pesticide molecule is very small. Generally, when it enters the animal body, the response against it is invoked when it gets tagged with a much bigger protein molecule. Thus, the antibodies generated inside the animal body in response to the injected pesticide are actually produced for action against the pesticide—protein conjugate. Thus, measuring the response of the antibody to the pesticide molecule, in the presence of the pesticide—protein molecule, gave us an idea of how specific the reaction of the antibody would be toward this pesticide, when the pesticide is in small quantities and there are several other contaminants that may interfere with this reaction.

Once the antibodies that had an affinity for the pesticide molecule were identified, the next thing was to fabricate a sensor that was sensitive enough to measure this reaction, portable enough to be carried to the site and cheap enough to ensure that testing the environment for pesticides would be affordable. That’s where we innovated.

In order to measure the extent of the reaction between the antigen and the antibody, we decided to convert the chemical reaction output into an electrical signal that could be measured. However, measuring such a small current requires very sensitive electrodes. This required us to use gold for the electrode material, as it has a very high electrochemical sensitivity Yet, our goal was to make the biosensor as cheap as possible.

We took scrap plastic (rather than a more expensive material), cut it into small pieces and sputtered it with bulk gold. We then used laser ablation (laser-assisted cutting) to demarcate the electrode areas. However, when we did the experiments, we realized that coating bulk gold did not give us the high sensitivity that was required.

So, we experimented with nano-gold instead. The sensor surface was modified by using electro-deposition of a film of Prussian blue embedded gold nanoparticles (PB- GNP). It was quite challenging, but it enhanced electron transfer in the vicinity of the gold electrode, increasing the sensitivity of the assay

While the sensitivity increased manifold, the cost was also reduced. In addition, the bio-compatibility increased. The antibodies could now sit on the surface of the gold with much more stability.”

Priyanka claims that their biosensor is much more cost-effective than existing biosensors. “You will be surprised to know that while existing biosensors cost $100-$600, our biosensor can be made for only
5.”

The biosensor is also very effective for its purpose. “We ran tests with water samples collected from nearby water-bodies, using the fabricated bio-chip and isolated antibodies. Even trace amounts of the pesticide were detected.”

The disposable plastic biochip is highly versatile and can be used for any immuno-sensor application, where high sensitivity and low cost are prime concerns. Thus, it can be used for clinical diagnosis, in addition to detecting a variety of environmental pollutants. Low-cost diagnosis is very important in developing countries like India and there is huge market potential for such biosensors.

“My first research paper was published in 2009, in
Biosensors and Bioelectronics,
an Elsevier journal. My parents were overjoyed. My father even took a print of it and tried to understand it.

In the later half of the same year, two more research papers were published and I became a star in my research group within a short period of time. Today, I have 13 publications, in nearly all the reputed journals, including
Nature.

We applied for the Indian patent in January 2010, and it has already been published. CSIR is now scrutinizing proposals to commercialize the technology.”

In 2011, Priyanka bagged the India Innovation Initiative (i3) Award by Agilent Technologies, in association with Confederation of Indian Industries (CII) and DST.

At the age of 28, she was the only woman on MIT Technology Review’s list of top Indian Innovators for the year 2012. She also received the DST Lockheed Martin Gold Medal for 2012.

She shares an interesting anecdote related to this medal. The
1 lakh cash prize that comes with the medal was given in the form of a large check. “I was returning from the event on Shatabadi Express and was holding the fake check. Everybody thought I was a sportsperson. People kept asking me about it. When I told them that I was a scientist, they could not believe it. I guess they were a little disappointed.

My parents received me at the station with a big
band–baaja
group. There were so many onlookers; it was hilarious.

Soon after, the MIT Technology Review’s list of top 35 innovators was declared and people from the media flocked to my house. There were interviews, photography sessions and what not. I had never received that kind of attention before. They made me feel like a celebrity.”

In 2012, INKTalks, a global organization that hosts some of the greatest thinkers to speak about their experiences, invited Priyanka to Pune to talk about her work and its future applications.

“Apart from the recognition, my research work has brought me a lot of satisfaction and an opportunity to travel the world.

In 2010, I went to Northwestern University in the US as a visiting research scholar. It was an amazing experience. Research work abroad is very different from that in India – it is much more application-oriented and interdisciplinary. Researchers there tend to think much more creatively and are more networked. The experience in the US completely transformed my approach to my work. The skills I learned there made me more effective in research.”

Priyanka plans to join a post-doctoral program in India that focuses on interdisciplinary research and allows collaboration with laboratories abroad.

“I plan to further improve the biochip by enabling it to be coupled with micro-fluidic systems to enable automatic preparation of samples to be used with the biochip. This would help in situations where a large number of samples need to be tested, or those being tested have very low pesticide concentration. This would enable screening of several disease markers and environmental pollutants with a very small volume of the sample, which is otherwise difficult.”