Xurography actuated valving for centrifugal flow control.

We introduce a novel instrument controlled valving scheme for centrifugal platforms which is based upon xurography. In a first approach, which is akin to previously presented event-triggered flow control, the valves are composed of a pneumatic chamber sealed by a dissolvable film (DF) and by a pierceable membrane. Liquid is initially prevented from wetting the DF by the counter pressure of a trapped gas. Via a channel, this pocket is pneumatically connected to a vent, sealed by the pierceable membrane, located on the top surface of the disc. By scouring the top surface of the disc, along a pre-defined track by a robotic knife-cutter, the trapped gas is released and so the liquid can wet and disintegrate the DF. In order to automate assay protocols without the need to integrate DFs, we extend this xurography-based flow control concept by selective venting of chambers subjected to pneumatic over-pressure or vacuum suction. Unlike most instrument controlled flow-control mechanisms, in this approach to valve actuation can occur during disc rotation. To demonstrate the potential of this flow control approach, we designed a disc architecture to automate the liquid handling as the backbone of a biplex liver assay panel. We demonstrate valve actuation during rotation, using the robotic arm, using this disc with visualisation via dyed water. We then demonstrate the biplex liver assay, using calibration reagent, by stopping the disc and manually piercing the membrane to actuate the same valves.

Label-free impedance detection of cancer cells from whole blood on an integrated centrifugal microfluidic platform.

An electrochemical Lab-on-a-Disc (eLoaD) platform for the automated quantification of ovarian cancer cells (SKOV3) from whole blood is reported. This centrifugal microfluidic system combines complex sample handling, i.e., blood separation and cancer cell extraction from plasma, with specific capture and sensitive detection using label-free electrochemical impedance. Flow control is facilitated using rotationally actuated valving strategies including siphoning, capillary and centrifugo-pneumatic dissolvable-film (DF) valves. For the detection systems, the thiol-containing amino acid, L-Cysteine, was self-assembled onto smooth gold electrodes and functionalized with anti-EpCAM. By adjusting the concentration of buffer electrolyte, the thickness of the electrical double layer was extended so the interfacial electric field interacts with the bound cells. Significant impedance changes were recorded at 117.2 Hz and 46.5 Hz upon cell capture. Applying AC amplitude of 50 mV at 117.2 Hz and open circuit potential, a minimum of 214 captured cells/mm(2) and 87% capture efficiency could be recorded. The eLoaD platform can perform five different assays in parallel with linear dynamic range between 16,400 and (2.6±0.0003)×10(6) cancer cells/mL of blood, i.e. covering nearly three orders of magnitude. Using the electrode area of 15.3 mm(2) and an SKOV3 cell radius of 5 µm, the lower detection limit is equivalent to a fractional surface coverage of approximately 2%, thus making eLoaD a highly sensitive and efficient prognostic tool that can be developed for clinical settings where ease of handling and minimal sample preparation are paramount.

A portable centrifugal analyser for liver function screening.

Mortality rates of up to 50% have been reported after liver failure due to drug-induced hepatotoxicity and certain viral infections (Gao et al., 2008). These adverse conditions frequently affect HIV and tuberculosis patients on regular medication in resource-poor settings. Here, we report full integration of sample preparation with the read-out of a 5-parameter liver assay panel (LAP) on a portable, easy-to-use, fast and cost-efficient centrifugal microfluidic analysis system (CMAS). Our unique, dissolvable-film based centrifugo-pneumatic valving was employed to provide sample-to-answer fashion automation for plasma extraction (from finger-prick of blood), metering and aliquoting into separate reaction chambers for parallelized colorimetric quantification during rotation. The entire LAP completes in less than 20 min while using only a tenth the reagent volumes when compared with standard hospital laboratory tests. Accuracy of in-situ liver function screening was validated by 96 separate tests with an average coefficient of variance (CV) of 7.9% compared to benchtop and hospital lab tests. Unpaired two sample statistical t-tests were used to compare the means of CMAS and benchtop reader, on one hand; and CMAS and hospital tests on the other. The results demonstrate no statistical difference between the respective means with 94% and 92% certainty of equivalence, respectively. The portable platform thus saves significant time, labour and costs compared to established technologies, and therefore complies with typical restrictions on lab infrastructure, maintenance, operator skill and costs prevalent in many field clinics of the developing world. It has been successfully deployed to a centralised lab in Nigeria.