Photoactivable AIEgen-based Lipid-Droplet-Specific Drug Delivery Model for Live Cell Imaging and Two-Photon Light-Triggered Anticancer Drug Delivery.

Lipid droplets (LDs) are dynamic complex organelles involved in various physiological processes, and their number and activity are linked to multiple diseases, including cancer. In this study, we have developed LD-specific near-infrared (NIR) light-responsive nano-drug delivery systems (DDSs) based on chalcone derivatives for cancer treatment. The reported nano-DDSs localized inside the cancer microenvironment of LDs, and upon exposure to light, they delivered the anticancer drug valproic acid in a spatiotemporally controlled manner. The developed systems, namely, 2'-hydroxyacetophenone-dimethylaminobenzaldehyde-valproic (HA-DAB-VPA) and 2'-hydroxyacetophenone-diphenylaminobenzaldehyde-valproic (HA-DPB-VPA) ester conjugates, required only two simple synthetic steps. Our reported DDSs exhibited interesting properties such as excited-state intramolecular proton transfer (ESIPT) and aggregation-induced emission (AIE) phenomena, which provided advantages such as AIE-initiated photorelease and ESIPT-enhanced rate of photorelease upon exposure to one- or two-photon light. Further, colocalization studies of the nano-DDSs by employing two cancerous cell lines (MCF-7 cell line and CT-26 cell line) and one normal cell line (HEK cell line) revealed LD concentration-dependent enhanced fluorescence intensity. Furthermore, systematic investigations of both the nano-DDSs in the presence and absence of oleic acid inside the cells revealed that nano-DDS HA-DPB-VPA accumulated more selectively in the LDs. This unique selectivity by the nano-DDS HA-DPB-VPA toward the LDs is due to the hydrophobic nature of the diphenylaminobenzaldehyde (mimicking the LD core), which significantly leads to the aggregation and ESIPT (at 90% volume of fw, ΦF = 20.4% and in oleic acid ΦF = 24.6%), respectively. Significantly, we used this as a light-triggered anticancer drug delivery model to take advantage of the high selectivity and accumulation of the nano-DDS HA-DPB-VPA inside the LDs. Hence, these findings give a prototype for designing drug delivery models for monitoring LD-related intracellular activities and significantly triggering the release of LD-specific drugs in the biological field.

BODIPY-Based Mitochondrial Targeted NIR-Responsive CO-Releasing Platform for the On-Demand Release of CO to Treat Cancer.

It is an established fact that cancer is one of the most serious public health issues after coronary artery disease. Thus, exploring more effective and efficient therapeutic protocols over the traditional chemotherapeutic strategy is imperative to improving cancer survivorship and patient quality of life. In this respect, recent reports on molecularly engineered meso-substituted BODIPY have shown remarkable effects as a photoresponsive CO-releasing platform for the on-demand release of CO to treat cancer. Herein, we designed and synthesized two meso-substituted BODIPY photoresponsive CO-releasing molecules (photoCORMs). These BODIPY derivatives were tethered to a phenoxymethylpyridine moiety and oligoethylene glycol to maintain a hydrophilic-hydrophobic balance and improved cell permeability. The cell imaging experiments demonstrated that oligoethylene glycol containing photoCORM-1 efficiently internalized and preferentially localized at the mitochondria. To understand the mechanistic aspect of preferential localization into the mitochondria, live cell imaging was also carried out. Photorelease of CO was directly monitored by the inline IR spectroscopic technique. Finally, in vitro cytotoxicity and apoptosis assays on MDA-MB-231 cell lines clearly showed that photoCORM-1 induced apoptosis-mediated cell killing on account of photoreleased CO, which otherwise showed insignificant toxicity even at a very high concentration of ∼50 µM.

Spatiotemporal photo-release of hydrogen sulphide from ß-carboline-derived nanoparticles for therapeutic applications.

Hydrogen sulfide (H2S) is an important gasotransmitter that plays a significant role in the regulation of various physiological activities. The therapeutic effect of H2S is highly concentration-dependent and has recently been recognized for wound healing applications. Until now, the reported H2S delivery systems for wound healing applications have been focused on polymer-coated cargo systems for the encapsulation of H2S donors that are based just on endogenous stimuli-responsive systems such as pH or glutathione. These delivery systems lack spatio-temporal control and can cause premature H2S release depending on the wound microenvironment. In this regard, polymer-coated light-activated gasotransmitter donors provide a promising and efficient means of delivering high spatial and temporal control along with localized delivery. Hence, for the first time, we developed a ß-carboline photocage-based H2S donor (BCS) and formulated it into two photo-controlled H2S delivery systems: (i) Pluronic-coated nanoparticles loaded with BCS (Plu@BCS nano); and (ii) a hydrogel platform impregnated with BCS (Plu@BCS hydrogel). We investigated the mechanism of photo-release and the photo-regulated H2S release profile from the BCS photocage. We found that the Plu@BCS nano and Plu@BCS hydrogel systems were stable and did not release H2S without light treatment. Interestingly, external light manipulation, such as changing the irradiation wavelength, time, and location, regulate the release of H2S precisely. Biological studies (in vitro) suggest that the Pluronic coating on the BCS photocage makes the donor highly biocompatible and desirable for biological applications.

NIR-Responsive Lysosomotropic Phototrigger: An "AIE + ESIPT" Active Naphthalene-Based Single-Component Photoresponsive Nanocarrier with Two-Photon Uncaging and Real-Time Monitoring Ability.

In recent times, organelle-targeted drug delivery systems have gained tremendous attention due to the site-specific delivery of active drug molecules, resulting in enhanced bioefficacy. In this context, a phototriggered drug delivery system (DDS) for releasing an active molecule is superior, as it provides spatial and temporal control over the release. So far, a near-infrared (NIR) light-responsive organelle-targeted DDS has not yet been developed. Hence, we introduced a two-photon NIR light-responsive lysosome-targeted "AIE + ESIPT" active single-component DDS based on the naphthalene chromophore. The two-photon absorption cross section of our DDS is 142 GM at 850 nm. The DDS was converted into pure organic nanoparticles for biological applications. Our nano-DDS is capable of selective targeting, AIE luminogenic imaging, and drug release within the lysosome. In vitro studies using cancerous cell lines showed that our single-component photoresponsive nanocarrier exhibited enhanced cytotoxicity and real-time monitoring ability of drug release.

One- and Two-Photon Uncaging of Carbon Monoxide (CO) with Real-Time Monitoring: On-Demand Carbazole-Based Dual CO-Releasing Platform to Test over Single and Combinatorial Approaches for the Efficient Regression of Orthotopic Murine Melanoma In Vivo.

Herein, we report three new metal-free, photochemically active single, dual, and combinatorial CORMs (photoCORMs) based on a carbazole-fused 1,3-dioxol-2-one moiety which released one equivalent of CO, two equivalent of CO, and a combination of one equivalent of each CO and anticancer drug upon one- and two-photon excitation, respectively. The photoCORMs exhibited good cellular uptake and real-time monitoring ability of CO uncaging by a color change approach in cancerous B16F10 cells. Interestingly, the cytotoxicity assay on B16F10 cells indicated that the dual photoCORM has increased anticancer activity over the single and combinatorial photoCORMs upon irradiation. Our results also showed that CO could accelerate the effectiveness of the well-known anticancer drug (chlorambucil). Finally, the in vivo evaluation of the dual photoCORM on an established murine melanoma tumor (C57BL/6J mouse model) manifested a significant regression of tumor volume and led to significant improvement (>50%) in the overall survivability.

Mitochondria-localized in situ generation of rhodamine photocage with fluorescence turn-on enabling cancer cell-specific drug delivery triggered by green light.

In this work, we have developed a rhodamine dye based water-soluble, mitochondria-indicating photocage, which gets activated in the mitochondria producing a fluorescent signal and on-demand releases the caged anticancer drug, chlorambucil, in the cancer cells selectively upon irradiation of green light.

An improved tumor-specific therapeutic strategy by the spatio-temporally controlled in situ formation of a Cu(ii) complex, leading to prompt cell apoptosis via photoactivation of a prodrug.

The anti-tumor activity of Cu complexes is well established in cancer research. We developed a biotin-tagged Cu-chelating prodrug that is activated by one-photon and two-photon irradiation for the target-specific and spatio-temporally controlled in situ generation of a Cu complex. In this way, we transform copper from a "cancer-promoting" agent to an anticancer agent.

A lysosome-specific near-infrared fluorescent probe for in vitro cancer cell detection and non-invasive in vivo imaging.

Near-infrared (NIR) fluorescent probes have been developed as potential bio-materials having profound applications in diagnosis and clinical practice. Herein, we wish to disclose a highly photostable ultra-bright NIR probe for the specific detection of lysosomes in numerous cell lines. Furthermore, the applicability of the developed NIR probe was evaluated for in vivo imaging.

'AIE + ESIPT' assisted photorelease: fluorescent organic nanoparticles for dual anticancer drug delivery with real-time monitoring ability.

'Aggregation Induced Emission + Excited State Intramolecular Proton Transfer (AIE + ESIPT)'-assisted photorelease of an anticancer drug by a p-hydroxyphenacyl (pHP) phototrigger with real-time monitoring has been demonstrated.

ESIPT-induced fluorescent o-hydroxycinnamate: a self-monitoring phototrigger for prompt image-guided uncaging of alcohols.

o-Hydroxycinnamate derivatives are well-known phototriggers for fast and direct release of alcohols and amines without proceeding through the cleavage of carbonate or carbamate linkages. Despite these unique features, o-hydroxycinnamates lack extensive applications in biological systems mainly because of their non-fluorescent nature. To overcome this limitation, we have attached a 2-(2'-hydroxyphenyl) benzothiazole (HBT) moiety, capable of rapid excited-state intramolecular proton transfer (ESIPT) to the o-hydroxycinnamate group. The ESIPT effect induced two major advantages to the o-hydroxycinnamate group: (i) large Stokes' shifted fluorescence (orange colour) properties and (ii) distinct fluorescence colour change upon photorelease. In vitro studies exhibited an image guided, photoregulated release of bioactive molecules by the o-hydroxycinnamate-benzothiazole-methyl salicylate conjugate and real-time monitoring of the release action.

Redox-responsive xanthene-coumarin-chlorambucil-based FRET-guided theranostics for "activatable" combination therapy with real-time monitoring.

A FRET donor-acceptor xanthene-coumarin conjugate has been designed for redox-regulated synergic treatment of photodynamic therapy and chemotherapy with real-time monitoring. The "locked" FRET pair was selectively "unlocked" by biological reducing thiols via rupture of a sacrificial disulfide linker. A distinct change in fluorescence color and selective cancer cell toxicity were observed in vitro.