Here at BioStrata, we get excited about the latest biochemical research that is advancing life science technology. From biomarker assays and biosensors through to imaging and nanofluidics, we’re interested in the cutting-edge biotechnology enabling the development of new diagnostic techniques. Here, we highlight three recent diagnostic innovations that are getting experts talking.
‘Spit aptamer’ detects cocaine in saliva
A new super-sensitive assay that detects cocaine traces in saliva is the most sensitive to date, thanks to a split aptamer with an ultra-high affinity for cocaine developed by US researchers.
By incorporating two target-binding domains into a single split aptamer for the first time, the team produced a co-operatively binding aptamer whereby binding at one domain greatly enhanced that of the second, resulting in a much higher affinity for cocaine compared to the single-domain parent.
Aptamers – pairs of single-stranded oligonucleotides that bind to specific molecular targets – offer great potential in the realm of sensing, with applications ranging from medical diagnostics to environmental monitoring. In the absence of a target, the two fragments remain separate, but assemble when matched with the right molecule.
By incorporating a fluorophore–quencher pair in one of the fragments, ultra-sensitive fluorescence detection of cocaine at concentrations as low as 50 nM in 10% saliva could be obtained without signal amplification.
No-frills microfluidic device sorts parasites from blood
An inexpensive portable microfluidic device capable of enriching parasites in human blood to detectable levels has been developed by researchers at Lund University, which may be used in developing countries to assist in the early identification of deadly diseases like sleeping sickness.
Around 4000 cases of human African trypanosomiasis, or sleeping sickness, were reported in 2014, affecting much of sub-Saharan Africa. The disease, caused by Trypanosoma parasites, is passed between humans by tsetse flies. While treatable if caught early, diagnosis requires relatively high parasite numbers (around 10,000 per millilitre) for microscopic detection. With Trypanosoma levels in the blood often as much as 100-fold lower, successful detection requires enrichment. Separation techniques such as acoustophoresis, margination and inertial focusing can be used to concentrate pathogens to detectable levels in a well-equipped lab. However, when out in the field, limited access to equipment and even electricity can make this crucial step impossible.
Using a simple silicone microfluidic device that requires just a disposable syringe to apply pressure, the research team in Lund increased Trypanosoma levels in human blood 30-fold. The technique, based on deterministic lateral displacement, involves flowing particles through a forest of microscopic posts that slow down larger particles, allowing smaller particles to flow more freely through the device.
Though a diagnostic device isn’t yet field-ready, it’s believed the separation technology may be combined with impedance spectroscopy-based electronic cell counting to enable portable detection.
Metallacarboranes sense cystic fibrosis mutations
Spanish scientists have probed the interactions between two metallacarborane redox indicators and DNA, fuelling hopes that the anionic species may be used as biosensors for the detection of mutations associated with genetic disorders.
Ferrabisdicarbollide and its hexachlorinated analogue are water-soluble metal sandwich compounds with a strong reversible Fe3+/Fe2+ electroactive couple. Local structural changes will modify their electrochemical behaviour, meaning differential pulse voltammetry can be used to detect structural changes upon binding with DNA base pairs.
The group used the probes to sense the presence of two point mutations associated with cystic fibrosis in DNA amplicons extracted from blood cells. Differences in the voltammetric transduction of the hybridisation reaction of an immobilised DNA strand with a wild type or mutant strand gave characteristically different electrochemical responses that could be used as a reliable signal.
It’s hoped the low-cost biosensors could become a simpler alternative to conventional gene assays when it comes to the early detection of cancer or hereditary diseases.
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