Near-Infrared in and out: Observation of Autophagy during Stroke via a Lysosome-Targeting Two-Photon Viscosity-Dependent Probe.

Fluorescence imaging using probes with two-photon excitation and near-infrared emission is currently the most popular in situ method for monitoring biological species or events, with a large imaging depth, low background fluorescence, low optical damage, and high spatial and temporal resolution. Nevertheless, current fluorescent dyes with near-infrared emission still have some disadvantages such as poor water solubility, low fluorescence quantum yield, and small two-photon absorption cross sections. These drawbacks are mainly caused by the structural characteristics of dyes with large conjugation surfaces but lacking strong and rigid structures. Herein, a lysosome-targeted and viscosity-sensitive probe (NCIC-VIS) is designed and synthesized. The protonation of morpholine not only helps anchor NCIC-VIS to the lysosome but also significantly enhances its water solubility. More importantly, its viscosity can increase the rigid structure of NCIC-VIS, which will improve the fluorescence quantum yield and the two-photon absorption cross section due to the imposed restrictions on molecular torsion. Based on the abovementioned characteristics, the real-time imaging of cellular autophagy (could increase the viscosity of lysosomes) was realized using NCIC-VIS. The results demonstrated that the level of autophagy was significantly enhanced in mice during stroke, while the inhibition of oxidative stress significantly reduced the degree of autophagy. The study corroborates that oxidative stress induced by stroke can lead to the development of autophagy.

Tracking Autophagy Process with a TBET and AIE-Based Ratiometric Two-Photon Viscosity Probe.

Autophagy is a cellular self-degrading process that plays a key role in cellular health and functioning. Since autophagy disorder is related to many diseases, it is highly important to detect autophagy. This study aimed to establish a dual-sensing mechanism-based ratiometric viscosity-sensitive lysosome-targeted two-photon fluorescent probe Vis-sun to track the autophagy process (the increase in lysosome viscosity during autophagy) by combining through bond energy transfer (TBET) and aggregation-induced emission (AIE). The introduction of TBET not only overcame the interference of background signals but also achieved the baseline separation of two emission peaks, thus reducing the crosstalk between emissions, as well as the noninvasive bio-sensing of biological targets and long-term real-time tracer imaging by introducing AIE. In vitro experiments showed that the fluorescence intensity at 485 nm decreased gradually on increasing the volume ratio of water to tetrahydrofuran (Vwater/VTHF), while the fluorescence intensity at 605 nm increased significantly. Also, the fluorescence signal was maximized when the water content reached 100%. At the same time, the probe exhibited a significant dependence on the ambient viscosity. Therefore, the dynamic monitoring of lysosome viscosity during autophagy and the in situ imaging of autophagy fluctuations during stroke-induced neuroinflammation were successfully achieved by implementing Vis-sun lysosome anchoring with morpholine.

A smart cysteine-activated and heavy-atom-free nano-photosensitizer for photodynamic therapy to treat cancers.

A smart and heavy-atom-free photoinactive nano-photosensitizer capable of being activated by cysteine at the tumor site to generate highly photoactive nano-photosensitizers that show strong NIR absorption and fluorescence with a good singlet oxygen quantum yield (16.8%) for photodynamic therapy is reported.

Dual-wavelength responsive CuS@COF nanosheets for high-performance photothermal/photodynamic combination treatments.

Photothermal therapy (PTT) makes it difficult to achieve good performance on tumor treatments due to insufficient photothermal conversion efficiency, etc. Combining PTT with photodynamic therapy (PDT) and other therapeutic tools can significantly enhance the tumor-killing ability and has been widely used in the development of therapeutic platforms. Copper sulfide nanoparticle (CuS NP) photothermal reagents have the advantages of low toxicity and simple synthesis; therefore, combining CuS NPs with PDT photosensitizers is an effective strategy to construct a PTT/PDT combination therapeutic platform. However, PDT photosensitizers and photothermal agents generally assembled through hydrophobic interaction, suffer from low coating efficiency or the risk of drug leakage, thus seriously restricting their applications. To address these challenges, CuS NPs with excellent photothermal conversion performance were selected as the core material to prepare CuS@COF nanosheets through a dual-ligand assistant strategy with 4,7-bis(4-aminophenyl)-2,1,3-benzothiadiazole (BTD) and 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (TP). As a PTT/PDT combination therapeutic platform, CuS@COF nanosheets possess a porous TP-BDT-based COF shell, and it can sufficiently contact oxygen to provide high singlet oxygen (1O2) yield under 505 nm laser irradiation. Upon illumination with a 1064 nm laser, CuS@COF nanosheets can effectively convert the photon energy into thermal energy with a photothermal conversion efficiency of 63.4%. The results of the CCK8 experiment showed that the phototoxicity of the PTT/PDT combination treatment reached 85.1%, which was much higher than the effect of a single treatment. It was also confirmed in vivo that the tumor inhibition effect of the PDT/PTT combination treatment group was much greater than that of the single treatment group.