We report an easy-to-use Lab-on-Chip (LoC) device able to detect soluble, circulating biomarkers in plasma that are relevant to Coronary Artery Disease (CAD). The LoC prototype is developed within the SMARTool European project and is intended to be used for Point-of-Care (PoC) testing of patients with CAD, facilitating more rapid and efficient monitoring and treatment decisions. It will be part of a broader decision support system for the diagnosis, prognosis and treatment of CAD patients.
A device that enables performing an Enzyme-Linked Immunosorbent Assay (ELISA) on chip was developed and an ELISA protocol for the detection of selected biomarkers was established (Figure 1). The detection chamber of the chip was functionalised with antibodies that are physically adsorbed on the surface of the plastic chip, to selectively capture specific biomarkers in the input sample. The biomarker targeted was human ICAM-1 protein, which is implicated in the role of recruiting inflammatory cells and in combination with lipids and lipoproteins is responsible for atherosclerosis. For the detection of this biomarker, an optical Complementary Metal–Oxide–Semiconductor (CMOS) sensor was integrated on the system that measured the chemiluminescent signal emitted when the ELISA was completed. The parameters and protocol of the assay were optimised and the detectable concentration range was determined.
The previously described system, is controlled using external pumping equipment. Aiming to the creation of a tool that can be used by operators with no specific training in microfluidics, it was important to work towards a system that is autonomous. An integrated flow control system based on capillary flow, was developed in order to be able to minimize the requirements in terms of ancillary apparatus and human-operation. A technology for capillary-action based flow control combined with an electrostatic actuation mechanism are reported here and they are both integrated in low-cost, thermoplastic microfluidic chips (Figure 2). The devices enable sequential flow of liquids, using no external pumping equipment. The integrated capillary burst valves rely on an abrupt increase in the cross-section of a microfluidic channel causing the capillary filling to stop at the transition. In order to burst the valve and actuate the flow, an electrostatic actuation mechanism is integrated. A voltage is applied between two electrodes that are placed before and after the valve, an electrostatic field is created and the meniscus is attracted towards the second electrode. Application of short duration pulses prevents electrochemical processes that occur at the electrodes once the liquid makes contact with the counter electrode.
We presented here a LoC prototype enabling chemiluminescent assays to be performed on chip targeting biomarkers relevant to CAD. In parallel, we reported a robust technology for electrostatically actuated, capillary burst valve for PoC applications, integrated in potentially disposable, thermoplastic devices. The devices were fabricated using easily scalable fabrication techniques and can be used to perform multistep assays on single-use microfluidic devices. They consume little power during operation, making them suitable for use in handheld instruments. This project has received funding from the EU H2020 research and innovation programme under grant agreement No 689068.