Researchers at the Lee Bionanosciences Laboratory at UCD in Dublin have demonstrated the detection and measurement of biological analytes down to femtomolar concentration levels using an off the shelf qNano instrument.
This ultra low level biodetection capability has implications for biomedical research and clinical development as trace amounts of a biological substance in a sample can now be detected and quantified using standard commercially available equipment.
The findings by Dr. Mark Platt (Loughborough University and formerly University College Dublin), Professor Gil Lee, (University College Dublin) and Dr. Geoff Willmott (MacDiarmid Institute, New Zealand) have been published in Small, the peer-reviewed journal on micro- and nanoscales science.
Platt and colleagues’ method for femtomolar-level detection uses magnetic particle systems and can be applied to any biological particle or protein for which specific antibodies or aptamers exist.
Resistive pulse sensing, the underlying technology of the qNano, was used to monitor individual and aggregated rod-shaped nanoparticles as they move through tunable pores in elastomeric membranes.
The authors say, “The strength of using the qNano is its simplicity and the ability to interrogate individual particles through a nanopore. This allowed us to establish a very sensitive measurement of concentration because we could detect the interactions occurring down to individual particle level.”
The unique and technically innovative approach of the authors was to detect a molecule’s presence by a process that results in end on end or side by side aggregation of rod shaped nickel-gold particles.
The rods were designed so that any specific aptamer could be attached to one end only.
“By comparing particles of similar dimensions we demonstrated that the resistive pulse signal is fundamentally different for rod and sphere-shaped particles, and for rod shaped particles of different lengths. We could exploit these differences in a new agglutination assay to achieve these low detection levels,” says Dr. Platt.
In the agglutination assay particles with a particular aspect ratio can be distinguished by two measurements: the measured drop in current as particles traverse the pore ( ∆ip ), which reveals the particle’s size, and the full width at half maximum (FWHM) duration of the resistive pulse, which relates to the particle’s speed and length.
Limits of detection down to femtomolar levels were thus able to be demonstrated.
The article “Resistive Pulse Sensing of Analyte-Induced Multicomponent Rod Aggregation Using Tunable Pores” Platt, M., Willmott, G. R. and Lee, G. U. (2012), Small. doi: 10.1002/smll.201200058 is online for subscribers at http://onlinelibrary.wiley.com/doi/10.1002/smll.201200058/abstract.
“This is a real milestone for Izon’s technology as being able to measure biomolecules down to these extremely low levels opens up new bio-analysis options for researchers. 10 femtomolar was achieved, which is the equivalent dilution to 1 gram in 3.3 billion litres, or 1 gram in 1300 Olympic sized swimming pools,” says Hans van der Voorn, Executive Chairman of Izon Science.
Izon Science will continue to work with Dr. Platt at Loughborough, and with University College Dublin and various customers to develop a series of diagnostic kits that can be used with the qNano to identify and measure biomolecules, viruses, and microvesicles.
“We’re now developing standardized diagnostics kits for researchers which will allow them to optimize protocols for their particular targets of interest. The interest is in accurate quantification as much as the core detection,” says van der Voorn.
Izon Science is the developer of the portable qNano and qViro-X instruments with unique size-tunable nanopores.
The multi-parameter instruments offer significant accuracy and reliability improvements over light based techniques and are advancing research in a number of fields including nanomedicine, hematology, gene therapy and vaccine development.