During the first part of the project, the ER worked on the fabrication of a paper-based printed platform for electrochemical biosensors. Paper-based devices are emerging as an alternative for Point of Care (PoC) manufacturing as they are amenable to mass production at low cost using wax and screen printing. Several paper substrates and printing conditions were evaluated, according to their feasibility for electrochemical applications. Since D-xylose biosensor was to be employed primarily with blood samples, the effect of haematocrit on the electrochemical detection of analytes was assessed. The use of human blood was authorised by ethical approval from the corresponding regional ethical committee. While waiting for ethical approval, the ER was focused on the optimization of a D-xylose biosensor for urine samples. A flexible approach that may be applied to the analysis of other molecules of high interest in diagnosis and to other biological fluids was then developed. Due to the innovation and commercial possibilities of such strategy, a patent application was filed to protect the invention and to ensure further exploitation.
The new strategy was subsequently applied for the determination of D-xylose in plasma samples. The plastic-based D-xylose biosensor prototype was tried with spiked plasma samples, showing very promising results: 80% of the tested samples exhibited %recoveries within 85-115% range. This showed the high accuracy and reproducibility of the new system. Further adjustments to test whole blood samples were also tried. Regarding paper substrate, a fully operative D-xylose biosensor was achieved by combining previous advances in plastic-based biosensors and paper-based electrodes. Preliminary analytical data in buffer were shown to be very promising, although further optimization for biological sample testing was required. At the final stage of the project, the analytical and clinical correlation of Osaxyl device (system for D-xylose determination in urea) was performed. The ER participated in the planning and design of the validation protocols. Also, she collaborated in the procedure to achieve CE marking and ISO 13485 certification.
