Observations of intracellular second-harmonic generation imaging in black phosphorus nanosheets

Functionalized black phosphorus(BP)nanosheets have been considered as promising nanoagents in cancer therapy due to their excellent photothermal conversion efficiency.However,it is still difficult to visually monitor the dynamic localization of BP nanoagents in cancer cells.In this paper,we systematically studied the second-harmonic generation(SHG)signals originating from exfoliated BP nanosheets.Interestingly,under the excitation of a high frequency pulsed laser at 950 nm,the SHG signals of BP nanosheets in vitro are almost undetectable because of their poor stability.However,the intracellular SHG signals from BP nanosheets could be measured by in vivo optical imaging due to the efficient enrichment of living HeLa cells.Moreover,the SHG signal intensity from BP nanosheets increases with the prolonged incubation time.It can be expected that the BP nanosheets could be a promising intracellular SHG nanoprobe employed for visually in vivo biomedical imaging in practical cancer photothermal therapy(PIT).

Luminescent probes for luminescence lifetime sensing and imaging in live cells:a narrative review

Luminescence(mostly fluorescence and phosphorescence)probes are a powerful tool widely used in the life sciences research.They can be used,for example,in the quantitative analysis of physiological parameters,visualization of different cell organelles,and measurement of drug transportation.The luminescence intensity and lifetime of these probes are among the main signals recorded and evaluated in these applications.Other reviews have discussed optical probes from the perspective of their luminescence intensity.However,the luminescence lifetime,which depends on the molecular microenvironment but not the probe concentration,is another promising metric for biological sensing and imaging applications.In this review,we aim to introduce the basic strategies of FLIM probe design.We also present applications of these probes,including sensing of intracellular pH,cation/anion concentrations,oxygen levels,biomolecule contents,and physiological parameters,as well as live-cell imaging based on luminescence lifetime.Studies based on FLIM imaging of cells or tissues with endogenous organic molecules are not included in this mini review.With the rapid development of microscopy technology for fluorescence lifetime imaging,fluorescence lifetime-based probes have shown great potential in a variety of biological applications.