A myriad of assay formats are available for nanobiosensing applications. The key to select a particular one is based on the requirement of target detection. When sensitivity is of primary concern, the fluorescence and DLS methods usually offer lower detection limits than the colorimetric and refractive index sensing. SERS can even detect at single molecule level. In terms of simplicity and reliance on equipment, the colorimetric method outperforms DLS and SERS since it can be viewed by even the naked eyes. It might be noteworthy to highlight that metal NCs which represent a new class of fluorophore has the potential to outperform the conventional organic dyes in fluorescence-based nanobiosensors development.

Chapter Contents:

• 26.1 Introduction
• 26.2 Sensing principles
• 26.2.1 Sensing based on absorption of metal NPs
• 26.2.1.1 Interparticle-distance dependent color change
• 26.2.1.2 Refractive index change
• 26.2.2 Sensing based on light scattering of metal NPs
• 26.2.2.1 Scattered light intensity or wavelength change
• 26.2.2.2 NP-enabled dynamic light scattering (DLS)
• 26.2.3 Sensing based on interaction between metal NPs and fluorophore/ reporter
• 26.2.3.1 Metal-induced fluorescence quenching
• 26.2.3.2 Metal-enhanced fluorescence
• 26.2.3.3 Surface-enhanced Raman scattering
• 26.2.4 Sensing based on intrinsic luminescent properties of metal NCs
• 26.2.4.1 NC luminescence turn-off
• 26.2.4.2 NC luminescence turn-on
• 26.2.4.3 Formation process of luminescent metal NCs
• 26.2.5 Summary/ outlook
• 26.3 Development of paper-based POC diagnostic devices
• 26.3.1 Dipstick assays
• 26.3.2 Lateral flow assays
• 26.3.3 Microfluidic paper analytical devices
• 26.3.4 Summary/ outlook
• 26.4 Future perspectives
• 26.4.1 Commercialization potentials
• 26.4.2 Future challenges
• References

Inspec keywords: nanosensors; surface enhanced Raman scattering; nanomedicine; optical sensors; refractive index; fluorescence; biosensors; molecular biophysics; dyes; patient diagnosis

Other keywords: target detection; fluorescence; refractive index sensing; biological analysis; fluorophore; medical diagnostics; DLS; metallic nanobiosensors; colorimetric method; fluorescence-based nanobiosensors; single molecule level; low detection limits; colorimetric index sensing; conventional organic dyes; naked eyes

Subjects: Biosensors; Patient diagnostic methods and instrumentation; Optical instruments and techniques; Nanotechnology applications in biomedicine; Biomedical measurement and imaging; Molecular biophysics; Biosensors; Microsensors and nanosensors