Abstract
Owing to the unique optophysical properties of nanomaterials and their self-calibration characteristics, nanomaterial-based (e.g., polymer dots (Pdots) quantum dots (QDs), silicon nanorods (SiNRs), and gold nanoparticle (AuNPs), etc.) ratiometric fluorescent sensors play an essential role in numerous biosensing and cell imaging applications. The dual-emission ratiometric fluorescence technique has the function of effective internal referencing, thereby avoiding the influence of various analyte-independent confounding factors. The sensitivity and precision of the detection can therefore be greatly improved. In this review, the recent progress in nanomaterial-based dual-emission ratiometric fluorescent biosensors is systematically summarized. First, we introduce two general design approaches for dual-emission ratiometric fluorescent sensors, involving ratiometric fluorescence with changes of one response signal and two reversible signals. Then, some recent typical examples of nanomaterial-based dual-emission ratiometric fluorescent biosensors are illustrated in detail. Finally, probable challenges and future outlooks for dual-emission ratiometric fluorescent nanosensors for biosensing and cell imaging are rationally discussed.
Highlights
It is reasonable to infer that the carbon dots (CDs), SiNDs, and PNPs have the greatest potential for widespread application in biosensing and cell imaging
Nanomaterial-based dual-emission fluorescent sensors provide a powerful platform for precise molecular detection and cell imaging, with a high spatiotemporal resolution
As the key components of low-background fluorescence quenchers or fluorescent reporters, nanomaterials play a vital role in ensuring the high sensitivity and imaging contrast of the nanosensors
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Due to unavoidable interferences from analyte-independent factors, such as environmental fluctuations, instrumental efficiency, local concentration variation of sensors, and the sample matrix, the detection signal arising from the change of intensity at one emission wavelength is usually problematic. To circumvent such a situation, another fluorescence signal is introduced in the design of ratiometric sensors. Compared with fluorescent proteins (FPs) or organic dyes, nanomaterialbased fluorescent sensors possess certain advantages for intracellular applications The dimensions of these nanomaterials are typically 1–200 nm, favoring entry into live cells by endocytosis, particle bombardment delivery, phagocytosis, pico-injection, or other pathways [8,9,10]. Specific examples of these three classes of nanosensor are presented in the subsequent sections
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