Abstract

The biosensor interface is the heart of biosensing devices and point-of-need platforms. Analyte detection relies on biosensor surface modifications with different molecules (specific binding molecules, blocking molecules, etc.), accomplished following multi-step functionalization and assay procedures, but discrimination of these molecules is not provided by biosensor response. Mass fabrication of biosensors integrated on a chip is facilitated by spatially-selective functionalization through printing of probe molecules, but the resulting multi-molecular distributions are not readily available. Assay efficiency is determined by the orientation and conformation of probe molecules on biosensor surface, but they are rarely determined during assay development. Above challenges in biosensor functionalization and assay can be solved by microanalysis and chemical imaging provided by Time-of-Flight Secondary Ion Mass Spectrometry. This perspective article shows that biosensor surface modifications can be compared with ToF-SIMS not only to determine but also to optimize multi-molecular composition, bioprinting-based immobilization and molecular orientation. These features are controlled through relevant surface phenomena of adsorption and desorption or droplet evaporation as revealed by ToF-SIMS data. The paper highlights the advantages of molecular discrimination with ToF-SIMS, such as accurate characterization of molecular composition that cannot be deduced only by biosensor response, verification of applied biofunctionalization protocol efficiency, and assay optimization with respect to probe immobilization conditions. Finally, application of ToF-SIMS imaging to biomolecules printed into microarrays, biosensors’ arrays or separate biosensor’s components on a chip are presented, with the printed domains comparable, wider or narrower than the nominal diameter of the printing pin. We hope that the reviewed experimental developments could be an inspiration for future research as to how TOF-SIMS analysis methods could assist in our understanding of complex phenomena taking place onto a surface.

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