Phosphorylcholine-based hydrogel for immobilization of biomolecules. Application to fluorometric microarrays for use in hybridization assays and immunoassays, and nanophotonic biosensing.

An approach is presented for covalent immobilization of biomolecules on an acrylate phosphorylcholine hydrogel. The immobilization and the hydrogel formation take place simultaneously by a thiol-acrylate coupling reaction, induced by UV-light (254 nm). The hydrogel is prepared on two polymeric surfaces (the HardCoat protective layer of Blu-Ray discs, and SU-8) and applied to fluorescence microarray and label-free interferometric detection. For the first, Cy5 labeled analytes are used (λem 635 nm) and, for the second, a periodic array of high-aspect ratio nanopillars detects unlabeled analytes by interferometry. Bioavailability of the immobilized probes is demonstrated in labeled assays; for the case of oligonucleotides by discriminating single nucleotide polymorphisms, and, for the case of antibodies, by BSA immunorecognition. The raw hydrogel is employed to detect human C-reactive protein, in both labeled and non-labeled assay formats, with sensitivities of 30 ng·mL-1 and 2 pg·mL-1, respectively. Graphical abstract Schematic presentation of the phosphorylcholine (MPC) hydrogel preparation onto BluRay disc and SU-8 nanopillars to perform fluorescence and label-free interferometric detection, respectively. It selectively detects C-reactive protein (CRP), but it can covalently immobilize antibodies or nucleid acid probes to detect other analytes.

A Proof-of-Concept of Label-Free Biosensing System for Food Allergy Diagnostics in Biophotonic Sensing Cells: Performance Comparison with ImmunoCAP.

Food allergy is a common disease worldwide with over 6% of the population (200⁻250 million people) suffering from any food allergy nowadays. The most dramatic increase seems to be happening in children and young people. Therefore, improvements in the diagnosis efficiency of these diseases are needed. Immunoglobulin type E (IgE) biomarker determination in human serum is a typical in vitro test for allergy identification. In this work, we used a novel biosensor based on label-free photonic transducers called BICELLs (Biophotonic Sensing Cells) for IgE detection. These BICELLs have a thin film of nitrocellulose over the sensing surface, they can be vertical optically interrogated, and are suitable for being integrated on a chip. The BICELLs sensing surface sizes used were 100 and 800 µm in diameter. We obtained calibration curves with IgE standards by immobilizating anti-IgE antibodies and identified with standard IgE calibrators in minute sample amounts (3 µL). The results, in similar assay format, were compared with commercially available ImmunoCAP®. The versatility of the interferometric nitrocellulose-based sensing surface was demonstrated since the limit of detections for BICELLs and ImmunoCAP® were 0.7 and 0.35 kU/L, respectively.