Surface plasmonic sensors have been widely used in biology, chemistry, and environment monitoring. These sensors exhibit extraordinary sensitivity based on surface plasmon resonance (SPR) or localized surface plasmon resonance (LSPR) effects, and they have found commercial applications. In this review, we present recent progress in the field of surface plasmonic sensors, mainly in the configurations of planar metastructures and optical-fiber waveguides. In the metastructure platform, the optical sensors based on LSPR, hyperbolic dispersion, Fano resonance, and two-dimensional (2D) materials integration are introduced. The optical-fiber sensors integrated with LSPR/SPR structures and 2D materials are summarized. We also introduce the recent advances in quantum plasmonic sensing beyond the classical shot noise limit. The challenges and opportunities in this field are discussed.

Plasmonic metasurfaces have been widely used in biosensing to improve the interaction between light and biomolecules through the effects of near-field confinement. When paired with biofunctionalization, plasmonic metasurface sensing is considered as a viable strategy for improving biomarker detection technologies. In this review, we enumerate the fundamental mechanism of plasmonic metasurfaces sensing and present their detection in human tumors and COVID-19. The advantages of rapid sampling, streamlined processes, high sensitivity, and easy accessibility are highlighted compared with traditional detection techniques. This review is looking forward to assisting scientists in advancing research and developing a new generation of multifunctional biosensors.

Background: Bladder cancer is considered a malignant tumour characterised by great heterogeneity. Engrailed-2 may be a gene implicated in bladder cancer. Bioinformatics analysis found base pair complementation between microRNA-27b and engrailed-2. The present study aimed to investigate the reciprocal association between microRNA-27b and engrailed-2 in bladder cancer. Methods: The microRNA-27b and the protein of engrailed-2 in the tissues and cells of the bladder were detected. The processes of apoptosis, proliferation, invasion, and migration of tumour cells were evaluated. The co-action between microRNA-27b and engrailed-2 was detected by a luciferase reporter system. Finally, the interaction between microRNA-27b and engrailed-2 was further verified in vivo. Results: The study found that the expression level of microRNA-27b is lower in bladder cancer tissues and cells than that in neighbouring ordinary tissues, whereas the opposite outcome was observed regarding the expression level of engrailed-2. Furthermore, microRNA-27b expression level is not significantly linked to the age of patients with bladder cancer; however, it is significantly associated with the clinicopathological grade of bladder cancer. Notably, engrailed-2 is negatively regulated by microRNA-27b. Transfection with microRNA-27b was associated with a significant reduction in the activity of bladder cancer cells and promoted apoptosis, while engrailed-2 restoration effectively reversed the above effects of microRNA-27b on bladder cancer in vitro and in vivo. Conclusions: In conclusion, engrailed-2 is engaged in the development and process of bladder cancer through the negative mediation of microRNA-27b; additionally, microRNA-27b/engrailed-2 could form a signalling pathway with a significant effect on the process of bladder cancer.