In the last decade the use of nanomaterials has been having a great impact in biosensing. In particular, the unique properties of noble metal nanoparticles have allowed for the development of new biosensing platforms with enhanced capabilities in the specific detection of bioanalytes. Noble metal nanoparticles show unique physicochemical properties (such as ease of functionalization via simple chemistry and high surface-to-volume ratios) that allied with their unique spectral and optical properties have prompted the development of a plethora of biosensing platforms. Additionally, they also provide an additional or enhanced layer of application for commonly used techniques, such as fluorescence, infrared and Raman spectroscopy. Herein we review the use of noble metal nanoparticles for biosensing strategies—from synthesis and functionalization to integration in molecular diagnostics platforms, with special focus on those that have made their way into the diagnostics laboratory.
Although repetitive patterns of antigens are crucial for certain immune responses, an understanding of how antibodies bind and dynamically interact with various spatial arrangements of molecules is lacking. Hence, we introduce a new method where molecularly precise nanoscale patterns of antigens are displayed using DNA origami and immobilized in a surface plasmon resonance (SPR) setup. Using antibodies with identical antigen binding domains, we find that all subclasses and isotypes studied, bind bivalently to two antigens separated at distances ranging from 3 to 17 nm. The binding affinities of these antibodies change with the antigen distances, with a distinct preference for antigens separated by approximately 16 nm, and considerable differences in spatial tolerance exist between IgM and IgG and between low and high affinity antibodies.
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