Lab on a Chip Blog

Microfluidics can be used to trap a single DNA-enzyme complex in its native state for real-time analysis without having to immobilise the DNA or the enzyme, claim US researchers.

Enzymes called restriction enzymes are used to chop up DNA at specific points called recogition sites, making them useful tools in biochemistry. To anayse how they recognise and cleave DNA, the enzyme or DNA needs to be immobilised on a glass slide, but this can modify their properties, and make it difficult to analyse the products. To combat this, Susan Muller and Weilin Xu at the University of California, Berkeley, pre-bound a restriction enzyme to DNA, and fed it through a microfluidic system. This trapped the complex, and then stretched it out. Adding Mg2+ then activated the enzyme, cleaving the DNA, and permitting analysis of the products.

Ron Larson, a chemical engineering expert at the University of Michigan, Ann Arbor, US, says: ‘this work represents a novel and elegant use of fluidics to trap and stretch single DNA molecules without interference by surfaces.’ He adds that ‘the “look Ma, no hands” approach pursued by Xu and Muller has a number of advantages, not least of which is the ability to recover cleavage products for further study.’

Molecular configuration image showing the trapping, stretching and subsequent cleavage of DNA

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Link to journal article
Exploring both sequence detection and restriction endonuclease cleavage kinetics by recognition site via single-molecule microfluidic trapping
Weilin Xu and Susan J. Muller, Lab Chip, 2011
DOI: 10.1039/c0lc00176g

A stretchable radio frequency (RF) radiation sensor that combines a microfluidic antenna and rigid electronic circuits has been developed by scientists in Sweden. This could open the way to reliable and durable second skin sensors for monitoring health.

Flexible electronics are used in applications such as cameras, computer keyboards and photovoltaic cells. Some success has been found with stretchable antennas but the connection between the stretchable material and the rigid circuits still results in strain and loss of device sensitivity. To make wearable devices, electronics not only need to be flexible but they also need to be stretchable to truly conform to skin. Unfortunately, development from a flexible to a stretchable device has remained an elusive goal.

Now, Shi Cheng and Zhigang Wu from Uppsala University have developed a hybrid technology that combines conventional rigid circuitry with a substrate making a device that can bend, twist and stretch

IMAGE: Flexible microfluidic sensor responds to radio frequency signals

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Link to journal article
Microfluidic stretchable RF electronics
Shi Cheng and Zhigang Wu, Lab Chip, 2010
DOI: 10.1039/c005159d