Pb(II) can cause serious damaging effects to human health, and thus, the study of Pb²⁺ detection methods to sensitively and selectively monitor Pb(II) pollution has significant importance. In this work, we have developed a label-free fluorescence sensing strategy based on a Pb(II) DNAzyme cleavage and the ThT/G-quadruplex complex. In the presence of Pb(II), a G-rich tail was cut and released from the substrate strand, which then would form a G-quadruplex structure by combination with ThT dye. The fluorescence signal increase was then measured for sensitive Pb(II) quantification with a limit of detection of 0.06 nM. Our sensor also demonstrated high selectivity against six different metal ions, which is very important for the analysis of complex samples.

The discrimination and recognition of biological targets, such as proteins, cells, and bacteria, are of utmost importance in various fields of biological research and production. These include areas like biological medicine, clinical diagnosis, and microbiology analysis. In order to efficiently and cost-effectively identify a specific target from a wide range of possibilities, researchers have developed a technique called differential sensing. Unlike traditional “lock-and-key” sensors that rely on specific interactions between receptors and analytes, differential sensing makes use of cross-reactive receptors. These sensors offer less specificity but can cross-react with a wide range of analytes to produce a large amount of data. Many pattern recognition strategies have been developed and have shown promising results in identifying complex analytes. To create advanced sensor arrays for higher analysis efficiency and larger recognizing range, various nanomaterials have been utilized as sensing probes. These nanomaterials possess distinct molecular affinities, optical/electrical properties, and biological compatibility, and are conveniently functionalized. In this review, our focus is on recently reported optical sensor arrays that utilize nanomaterials to discriminate bioanalytes, including proteins, cells, and bacteria.

Single-walled carbon nanotubes (SWCNTs) feature extraordinary electrical, optical and mechanical properties governed by their unique chiral structures, yet as-synthesized SWCNTs exist as heterogeneous mixtures with severe bundling, which severely restricts their high-performance applications. Over recent decades, tremendous progress has been achieved in the dispersion, chiral sorting and optical sensing of SWCNTs. In this review, we first comprehensively summarize the mainstream dispersion strategies of SWCNTs, including physical dispersion relying on external mechanical forces and non-destructive chemical dispersion such as polymer wrapping, DNA wrapping, surfactant adsorption and aromatic small molecule π–π stacking. Subsequently, we systematically introduce several representative chiral sorting techniques, namely aqueous two-phase extraction (ATPE), density gradient ultracentrifugation (DGU), gel column chromatography (GCC), and polymer-based wrapping approach. Furthermore, we highlight the research advances of SWCNT-based near-infrared (NIR) fluorescent sensors for the detection of metal ions, neurotransmitters, nucleic acids, proteins and viruses, as well as their applications in in vivo biological detection of plants and animals. Finally, we discuss the existing challenges in the scalable preparation of chirality-pure SWCNTs, sensor stability and in vivo applications, and prospect the future development directions toward practical translation. This review aims to provide a systematic reference for promoting the development and application of SWCNTs in advanced optical biosensing.