Ivan Maguire

ChromiSense: A colourimetric lab-on-a-disc sensor for chromium speciation in water

The development of a centrifugal device for quantitative analysis of both chromium (III) and (VI) species in water is reported. ChromiSense is a colourimetric sensor system that has been applied to the measurement of chromium in spiked river water samples. For analysis, the sample is loaded into a reservoir on the disposable microfluidic disc, along with reagents. A centrifugal force is created by spinning the disc to pump liquids through microchannels, causing them to mix and react to form a coloured product. The coloured product is then presented to a low-cost optical detection system, where absorbance measurements can be recorded. The optical detection system consists of a light emitting diode (LED) and photodiode (PD) couple. Chromium (III) was measured using 2,6-pyridine dicarboxylic acid as a ligand, forming a complex that was measured at 535nm and at 335nm. While measuring at 535nm allowed for the use of a low cost LED, the sensitivity was improved 2.5 times by measuring at 335nm. However, 335nm also yielded a diminished linear range with little improvement in limit of deteciton (LOD), and required a lengthier manufacturing process due to the need for a UV-transparent material. Chromium (VI) was detected using 1,5-diphenyl carbazide (DPC). This standard analysis method was simplified for automation on-disc, and optimised to achieve a low LOD. The LOD for trivalent and hexavalent chromium using this device were 21mgL-1 and 4μgL-1, respectively. The linear range for quantitative analysis was found to be 69-1000mgL-1 for Cr(III) and 14-1000μgL-1 for Cr (VI). While this range is high for Cr(III), incorporation of an off-disc pre-concentration method would make this technology suitable for environmental sample analysis. The device is simple to use, low in cost, and could provide rapid on-site measurements, with results comparable to those obtained using a benchtop spectrophotometer.

SIZE- and deformability-based particle sorting by strategic design of obstacle arrays in continuous centrifugal sedimentation mode

This paper describes a novel, smart-grid technique for isolating, sorting and capturing cancer cells based on size and deformability by lateral displacement. In stopped-flow, centrifugal sedimentation mode, the bioparticles are sizeselectively displaced along the dynamically spaced grid of the microstructures in a deterministic fashion. Following displacement, particles are captured in claw-like structures for onward processing. This displacement method was first demonstrated for sorting seven bead populations with diameters between 5 μm and 30 μm from a mixture. Then HeLa and melanoma cells spiked in buffer and whole blood were isolated and captured. Finally, we succeeded to sort normal and fixed HeLa cells according to their deformability.

Novel Microfluidic Analytical Sensing Platform for the Simultaneous Detection of Three Algal Toxins in Water

Globally, the need for “on-site” algal-toxin monitoring has become increasingly urgent due to the amplified demand for fresh-water and for safe, “toxin-free” shellfish and fish stocks. Herein, we describe the first reported, Lab-On-A-Disc (LOAD) based-platform developed to detect microcystin levels in situ, with initial detectability of saxitoxin and domoic acid also reported. Using recombinant antibody technology, the LOAD platform combines immunofluorescence with centrifugally driven microfluidic liquid handling to achieve a next-generation disposable device capable of multianalyte sampling. A low-complexity “LED-photodiode” based optical sensing system was tailor-made for the platform, which allows the fluorescence signal of the toxin-specific reaction to be quantified. This system can rapidly and accurately detect the presence of microcystin-LR, domoic acid, and saxitoxin in 30 min, with a minimum of less than 5 min end-user interaction for maximum reproducibility. This method provides a robust “point of need” diagnostic alternative to the current laborious and costly methods used for qualitative toxin monitoring.

A centrifugal microfluidic-based approach for multi-toxin detection for real-time marine water-quality monitoring

Globally, fresh and brackish water sources are constantly under treat of exposure to toxins. Two of the most prevalent toxins from fresh and brackish water blooms are the cyclic peptide toxins of the microcystin family, formed from cyanobacterial, and the kainic acid analog neurotoxin known as domoic acid. There is therefore a significant need for constant and cost-effective ‘on-site’ algal-toxin monitoring to respond to constantly increasing demand for safe and ‘toxin-free’ freshwater, shellfish and fish stocks. Herein, we describe a Lab-On-A-Disc (LOAD) platform which was developed to assess microcystin and domoic acid concentration levels in-situ. Using recombinant antibody technology, the LOAD platform combines immunofluorescence with centrifugally driven microfluidic liquid handling to achieve a next-generation disposable device for high throughput sampling.