Towards reliable optical label-free point-of-care (PoC) biosensing devices

Abstract In this work, we report a method to read-out optical biosensors that significantly enhance the Limit of Detection (LoD). In a previous work we introduced the concept of “Increased Relative Optical Power” (IROP), related to the interferometric optical signals of two interferometers as a biosensing method to measure biological species [1] (Holgado et al., 2014). We predicted that this theory might have important implications for developing compact Point of Care (PoC) devices with a significant improvement in the LoD. Moreover, this method can be used for reading-out most of the optical transducers reported in the literature. While in that first study we demonstrated theoretically and experimentally this novel concept by using a conventional high-resolution spectrometer, in this article we report the performance of a novel compact PoC device specifically developed on IROP principle to demonstrate these expected predictions. This improvement in the performance is shown: Firstly by measuring a set of chips simulating thin biofilm thicknesses and fabricated by atomic layer deposition (ALD), and secondly by carrying out a direct immunoassay based on the complex anti-IgG/IgG. Finally, both results are compared with standard high-resolution spectrometry. The main conclusion is that this novel compact PoC based on IROP concept considerably enhance the LoD and performance in a cost-effective manner.