Molecular Biological Assay Applied to Cancer Diagnostics

Minute particles that measure micro ribonucleic acid (miRNA) levels have been utilized in tissue samples to provide a method to scan and diagnose cancer.

The technology uses an array of particles that attach themselves to a specific type of miRNA and when exposed to tissue, blood samples or purified RNA, these particles enable a miRNA profile to be created.

Chemical engineers at Massachusetts Institute of Technology (MIT; Cambridge, MA, USA) successfully used hydrogel particles, with a length of around 200 μm, to detect more easily and efficiently miRNA dysregulation patterns in samples taken from four individuals with cancer. Hydrogels are a type of polymer chain network that attract water causing the attachment of nucleic acids. The hydrogel particles are ornamented with millions of identical strands of DNA. The strands are complimentary to a specific miRNA target sequence. Consequently, miRNA in a blood sample will be attracted to and attach to the DNA on the hydrogel particle.

By mixing the hydrogel particles with a blood sample, any miRNA present binds to its respective DNA. The DNA strands on the hydrogel contain a short sequence that then binds to a fluorescent probe at the completion of the test. A custom designed microfluidic scanner is used to measure rapidly each particle's fluorescence, thus revealing how much miRNA is present. The scanner also reads a chemical barcode imprinted on each hydrogel particle, which identifies the type of miRNA being detected. The entire process is complete in less than three hours. By adding multiple DNA label sequences to each miRNA target, increases the sensitivity of the hydrogel miRNA-detection particles by as much as 100 times. This new approach is more accurate because different miRNA strands have different shapes, which affect how easily they bind to the DNA markers and using mixed DNA markers helps avoid this anomaly.

Patrick S. Doyle PhD, the lead author and a professor at MIT, and colleagues are now beginning work with medical researchers to study the use of miRNA detection for use in other diseases such as heart disease and HIV. Firefly Bioworks (Cambridge, MA, USA) will license the technology for the custom-made scanner that is needed to detect the fluorescence of the hydrogels, with an aim of providing a unit for commercial use. The study was published on August 3, 2011, in the journal Analytical Chemistry.

Related Links:
Massachusetts Institute of Technology
Firefly Bioworks