Publications

Microfluidics

Laser Tweezers

Compared to current approaches that heavily replies on amplification steps such as PCR to generate detectable signals, our detection system exploits mechanical signals that provide little background interference and high specificity between wild type and SNP sequences which is varied either by G/C or A/T mutations. The microfluidic setting allows multiplex sensing and in situ recycling of the SNP probe. Although previous attempts to combine laser tweezers and lab-on-a-chip system exist, our method represents the first SNP sensing based on these two techniques. Using this setup, we have successfully detected a SNP associated with coronary heart diseases at 100 pM in 30 minutes. We anticipate this system can function as a highly sensitive generic biosensor after incorporation of a specific recognition element, such as an aptamer for example.

Deepak Koirala, Zhongbo Yu, Soma Dhakal, and Hanbin Mao,

J. Am. Chem. Soc., 2011, 133 (26), pp 9988–9991. A patent based on this finding has been filed.

Force Based Stochastic Sensing

This paper describes for the first time a new type of Force-Based Biosensing.  It employs a Single Molecule in a Laser Tweezers platform; it exploits a Stochastic sensing strategy; and it works on a Microfluidic chip.

Single Nucleotide Polymorphism (SNP) is the variation in the DNA sequence when a specific gene of individuals differs by a single nucleotide A, T, G or C.  It is the most common genetic variation in human genome with an average occurrence of ~1 per 1000 base pairs. SNP is associated with diseases, anthropometric characteristics, phenotypic variations, gene functions, and individual’s response to pathogens.  Therefore reliable detection of SNP is crucial for biological and clinical aspects. Recent development in the personalized medicine necessitates the recognition of genetic markers to track disease genes for biomedical diagnosis and therapy, which further amplifies the importance of SNP detection. In this work, we report a force based sensing of SNP at the single-molecule level, which presents superior sensitivity with an inherent capacity for stochastic sensing. The on-off stochastic signals of a single DNA template that recognizes SNP are recorded by laser tweezers in a microfluidic platform.