Matching the modular cartridge design, the read-out system is constructed in a multifunctional fashion. Through a basic station in which the cartridge is inserted the control and processing of the assay is automatically conducted. All relevant parameters such as pumping rates or incubation times are controlled to ensure the highest accuracy in the assay performance. Furthermore, the heating and cooling of fluids is integrated. Due to small sample volumes, the lab-on-chip device offers a faster processing of assays compared to normal lab work. After an assay has been performed, the read-out unit automatically processes the data. Through a user-optimized software interface, different parameters are displayed and the result is presented. The system is highly integrated, compact and being produced at low cost. It can be easily placed in small laboratories of physicians or of food or pharmaceutical producers.
The Fraunhofer ivD-platform showed the performance of the assay with two different analytical read-out systems. Total internal reflection fluorescence (TIRF) and electrochemistry were used as state-of-the-art sensing methods in diagnostic products.
Optical Detection (TIRF)
For the TIRF read-out a thin polymer film is used which is able to act as a waveguide and as a biochip. Optical elements for coupling light (in and out) are integrated into the foil which is injection-moulded and therefore very cheap and appropriate as a disposable. Using the TIRF principle, only the fluorescent molecules on the chip surface are excited whereby some washing steps become redundant. On-chip real-time monitoring of reactions is possible because the read-out can be done in presence of the sample.
An uncooled CCD camera detects fluorescence light spatially resolved. The limit of detection is comparable to a commercial laser scanner. With this technique, more than 500 measurement spots can be analysed in parallel.
Since electrochemistry is one of the most employed sensing methods in modern point-of-care devices a chip was developed for the detection of up to 16 different analytes. The principle is “single electrode-redox-cycling” meaning that spatially resolved enzymatic conversion of an electrochemical active substrate can take place. The detected current is therefore proportional to the analyte concentration.