As an emerging nanoprobe, surface enhanced Raman scattering (SERS) tags hold significant promise in sensing and bioimaging applications due to their attractive merits of anti-photobleaching ability, high sensitivity and specificity, multiplex, and low background capabilities. Recently, several reviews have proposed the application of SERS tags in different fields, however, the specific sensing strategies of SERS tags-based sensors for cellular molecules have not yet been systematically summarized. To provide beneficial and comprehensive insights into the advanced SERS tags technique at the cellular level, this review systematically elaborated on the latest advances in SERS tags-based sensors for cellular molecules detection and imaging. The general SERS tags-based sensing strategies for biomolecules and ions were first introduced according to molecular classes. Then, aiming at such molecules located in the extracellular, cellular membrane and intracellular regions, the tailored strategies by designing and manipulating SERS tags were summarized and explored through several key examples. Finally, the challenges and perspectives of developing high performance of advanced SERS tags were briefly discussed to provide effective guidance for further development and extended applications.

Implantable chemical sensors built with flexible and biodegradable materials exhibit immense potential for seamless integration with biological systems by matching the mechanical properties of soft tissues and eliminating device retraction procedures. Compared with conventional hospital-based blood tests, implantable chemical sensors have the capability to achieve real-time monitoring with high accuracy of important biomarkers such as metabolites, neurotransmitters, and proteins, offering valuable insights for clinical applications. These innovative sensors could provide essential information for preventive diagnosis and effective intervention. To date, despite extensive research on flexible and bioresorbable materials for implantable electronics, the development of chemical sensors has faced several challenges related to materials and device design, resulting in only a limited number of successful accomplishments. This review highlights recent advancements in implantable chemical sensors based on flexible and biodegradable materials, encompassing their sensing strategies, materials strategies, and geometric configurations. The following discussions focus on demonstrated detection of various objects including ions, small molecules, and a few examples of macromolecules using flexible and/or bioresorbable implantable chemical sensors. Finally, we will present current challenges and explore potential future directions.

Single molecule fluorescent probes have attracted considerable attention due to their ultimate sensitivity, fast response, low sample consumption, and high signal-to-noise ratio. Nanoparticles with outstanding optical properties make them perfect candidates for probes in the application of single molecule detection. In this review, we focus on various kinds of nanoparticles acting as single molecule fluorescent probes, including quantum dots, upconverting fluorescent nanoparticles, carbon dots, single-wall carbon nanotubes, fluorescent nanodiamonds, polymeric nanoparticles, nanoclusters, and metallic nanoparticles. Optical properties of various nanoparticles and their recent application in single molecule fluorescent probes are explored. How nanoparticles boost the sensitivity of detection is emphasized in combination with different sensing strategies. Future trends of nanoparticles in single molecule detection are also discussed. We hope that this review can provide practical guidance for researchers who work on nanoparticle-based single molecule fluorescent probes.

This review discusses recent advances and the reported strategies over the last ten years on the use of carbon-based quantum dots (QDs), including carbon dots (CDs), graphene quantum dots (GQDs), and polymer dots (PDs) in the design of fluorescence imaging and biosensing system for early diagnosis of cancers. Besides, this study comprehensively reports the latest developments in these years in the fluorescence imaging (FI) area with special attention to carbon-based QDs that take advantage of the excellent properties offered by these zero-dimensional (0D) nanomaterials as fluorescent tags. The most remarkable advantages of these carbon nanomaterials in the development of fluorescence sensing and imaging strategies compared to the conventional dyes arise from sharp emission spectra, long photostability, low-cost synthesis, reliability, reproducibility, high fluorescent intensity, and high surface functional groups such as carboxyl and amide, which impart better solubility in many solvents and aqueous media and facilitate their easy functionalization with biological species. The final section discusses the main challenges to be met to take full advantage of these properties in fluorescence bio-sensing and imaging as well as the possible future trends in this field based on the great advances that have occurred in recent years.

Due to their potential applications in industry and potent toxicity to the environment, sulfides and their detection have attracted the attention of researchers. To date, a large number of controlled-potential techniques for electrochemical sulfide sensors have been developed, thanks to their simplicity, reasonable limit of detection (LOD), and good selectivity. Different researchers have applied different strategies for developing selective and sensitive sulfide sensors. However, there has been no systematic review on controlled-potential techniques for sulfide sensing. In light of this absence, the main aim of this review article is to summarize various strategies for detecting sulfide in different media. The efficiencies of the developed sulfide sensors for detecting sulfide in its various forms are determined, and the essential parameters, including sensing strategies, working electrodes, detection media, pH, LOD, sensitivity, and linear detection range, are emphasized in particular. Future research in this area is also recommended. It is expected that this review will act as a basis for further research on the fabrication of sulfide sensors for practical applications.