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Optical tweezers have profound importance across fields ranging from manufacturing to biotechnology. However, the requirement of refractive index contrast and high laser power results in potential photon and thermal damage to the trapped objects, such as nanoparticles and biological cells. Optothermal tweezers have been developed to trap particles and biological cells via opto-thermophoresis with much lower laser powers. However, the intense laser heating and stringent requirement of the solution environment prevent their use for general biological applications. Here, we propose hypothermal opto-thermophoretic tweezers (HOTTs) to achieve low-power trapping of diverse colloids and biological cells in their native fluids. HOTTs exploit an environmental cooling strategy to simultaneously enhance the thermophoretic trapping force at sub-ambient temperatures and suppress the thermal damage to target objects. We further apply HOTTs to demonstrate the three-dimensional manipulation of functional plasmonic vesicles for controlled cargo delivery. With their noninvasiveness and versatile capabilities, HOTTs present a promising tool for fundamental studies and practical applications in materials science and biotechnology.

 

Point-of-care (POC) tests for the diagnosis of diseases are critical to the improvement of the standard of living, especially for resource-limited areas or countries. In recent years, nanobiosensors based on noble metal nanoparticles (NM NPs) have emerged as a class of effective and versatile POC testing technology. The unique features of NM NPs ensure great performance of associated POC nanobiosensors. In particular, NM NPs offer various signal transduction principles, such as plasmonics, catalysis, photothermal effect, and so on. Significantly, the detectable signal from NM NPs can be tuned and optimized by controlling the physicochemical parameters (e.g., size, shape, and elemental composition) of NPs. In this article, we introduce the inherent merits of NM NPs that make them attractive for POC testing, discuss recent advancement of NM NPs-based POC tests, highlight their social impacts, and provide perspectives on challenges and opportunities in the field. We hope the review and insights provided in this article can inspire new fundamental and applied research in this emerging field. 

Live imaging of the brain extracellular matrix (ECM) provides vital insights into changes that occur in neurological disorders. Current techniques such as second or third‐harmonic generation offer limited contrast for live imaging of the brain ECM. Here, a new method, pan‐ECM via chemical labeling of extracellular proteins, is introduced for live brain ECM imaging. pan‐ECM labels all major ECM components in live tissue including the interstitial matrix, basement membrane, and perineuronal nets. pan‐ECM enables in vivo observation of the ECM heterogeneity between the glioma core and margin, as well as the assessment of ECM deterioration under stroke condition, without ECM shrinkage from tissue fixation. These findings indicate that the pan‐ECM approach is a novel way to image the entire brain ECM in live brain tissue with optical resolution. pan‐ECM has the potential to advance the understanding of ECM in brain function and neurological diseases.