A massive step towards a method that will assist early detection of Genetic Mutation.

The changes in genetic sequence are responsible for the diversity among organisms. The name given to that phenomenon is Genetic Mutation and these changes can occur at various levels. Scientists are trying very hard to develop detection methods, for mutation, that could provide immediate results. The researchers from the University of California have created a chip that detects a particular type of mutation called Single Nucleotide Polymorphism (SNP). In addition to it, this biosensor has the ability to send the data in real-time to a computer, smartphone, or any other electronic device. According to the researching team, this chip is at least 1000 times more sensitive than the current technology which is being used to detect an SNP.

It is the most common type of genetic mutation which is harmless in majority of its forms. However, some of them makes the person more vulnerable to pathological diseases like neurodegenerative disorders, diabetes, inflammatory diseases, and cancers. The conventional methods for detecting the SNPs have a lot of limitations which offer plenty of room for improvement. Firstly, they need bulky instruments which cannot be operated without wires. Then, you need amplification to get multiple copies for detection. Last but not the least, you get relatively poor specificity and sensitivity after making all these efforts.

On the other hand, this newly-developed biosensor chip offers tremendous amount of portability as it is smaller than a fingernail. Similarly, it requires no wires and can detect SNPs in picomolar concentrations in solution. Ratnesh Lal, a Professor of Mechanical Engineering, Bioengineering, and Materials Science at the UC San Diego Jacobs School of Engineering, explained the features of this incredible invention in the following words:

“Miniaturized chip-based electrical detection of DNA could enable in-field and on-demand detection of specific DNA sequences and polymorphisms for timely diagnosis or prognosis of pending health crises, including viral and bacterial infection-based epidemics.”

All of this is made possible by a molecular process known as the DNA Strand Displacement. In this method, a double helix DNA exchanges one of its strands with a new one and scientists made full use of this attribute to develop this revolutionary chip. A Graphene Field Effect Transistor is assigned the task of detecting a change in the electrical signals. It is attached with the normal strand of the ‘DNA-tweezers’. This strand has a complementary sequence for a specific SNP. As soon as a protein with that SNP comes near this side of the tweezer, it sticks there which leads to the opening of the DNA-tweezers. Consequently, a change in the electric current is captured by the transistor.

The second strand of this tweezer is made weak so that it could be displaced easily when a strand containing the SNP binds with the normal one. Some of its nucleotides are replaced with a different molecule to weaken its bonds with the normal strand. The displacement of a strand leads to a net electric charge on the DNA-tweezers which is read by the Graphene transistor.

Prior to this discovery, this team of researchers built the first amplification-free electronic chip for SNP detection by collaborating with a lot of researchers from the UC San Diego including Gennadi Glinksy. He is a Research Scientists at the Institute of Engineering in Medicine at the University of California. That chip had a wire and was not as sensitive as the latest one. The team of Lal went for an improved version in order to enhance the portability capabilities and the sensitivity.

The design of the DNA-tweezers is the reason why this new chip is 1000 times more sensitive than its predecessor. When an SNP strand attaches with the DNA-tweezers, its geometry changes as they become almost parallel to the Graphene surface. Due to this, the net electric charge of the DNA comes much closer to the Graphene transistor and a larger signal is generated. Contrary to that, the structure of the previous chip didn’t allow that much flexibility so a weaker signal was generated upon the binding of an SNP strand.

Following this finding, the scientists aim to design array chips which will detect hundreds or thousands of SNPs in a single test. They hope to develop cheaper, portable, and faster biosensors that will detect SNPs from the blood and other fluids produced by the bodies of humans and animals.