A dual-analyte probe: hypoxia activated nitric oxide detection with phototriggered drug release ability.

A new strategy for the detection of hypoxia and NO succeeded by photocontrolled delivery of an anticancer agent has been demonstrated. The developed system is able to produce distinct responses (dual channel) upon interaction with hypoxia and NO. This probe can also release anticancer drugs upon photoirradiation acting potentially as both a dual-analyte imaging agent and a prodrug.

'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.

Environment Activatable Nanoprodrug: Two-Step Surveillance in the Anticancer Drug Release.

Remedial cancer therapy deals with a large number of theranostic applications. However, systems, so far known, are only capable of single surveillance for both diagnostic and therapeutic modes of action. A nanosystem, which can be localized to the cancer and deliver the chemotherapeutic agent on demand, will provide effective therapeutic activity. Herein, we designed a single component nanoprodrug ANPD-X (Activatable Nano Pro-Drug-X) which indentified the tumor sites by fluorescent color change (signal 1, blue to green fluorescence) using H2O2-mediated oxidation of boronate fluorophore. In the next step, precise spatiotemporal irradiation of light only on identified tumor sites resulted in the release of anticancer drug chlorambucil. The real time information on drug release was achieved by a second fluorescence color change (signal 2, green to blue fluorescence). Thus, nanoprodrug ANPD-X provided overall two-step surveillance in the anticancer drug delivery. Activation of the ANPD-X after addition of H2O2 and drug release upon photoirradiation was investigated in vitro by monitoring its fluorescence in the HeLa cell line.

A spiropyran-coumarin platform: an environment sensitive photoresponsive drug delivery system for efficient cancer therapy.

In spite of inventing several anticancer agents the clinical payoff still remains unsatisfactory because of their severe host toxicity due to their nonspecific biodistribution in the body. To achieve high efficiency in anti-cancer drug delivery, thus, we designed and developed a single component photoresponsive drug delivery system, a fusion of two platforms spiropyran and coumarin, which synchronizes two controlling factors: first, the lower pH of cancer tissue, which acts as an internal control and leads to the ring opening of spiropyran resulting in a distinct colour change and fluorescence activation of coumarin; and second, the release of the anti-tumor drug by the externally controlled light. Highly fluorescent nature and promising biocompatibility make the SP-Cou-Cbl system suitable for cell imaging and in vitro studies.

Correction: A spiropyran-coumarin platform: an environment sensitive photoresponsive drug delivery system for efficient cancer therapy.

Correction for 'A spiropyran-coumarin platform: an environment sensitive photoresponsive drug delivery system for efficient cancer therapy' by Shrabani Barman et al., J. Mater. Chem. B, 2017, DOI: 10.1039/c7tb00379j.

A p-Hydroxyphenacyl-Benzothiazole-Chlorambucil Conjugate as a Real-Time-Monitoring Drug-Delivery System Assisted by Excited-State Intramolecular Proton Transfer.

Among the well-known phototriggers, the p-hydroxyphenacyl (pHP) group has consistently enabled the very fast, efficient, and high-conversion release of active molecules. Despite this unique behavior, the pHP group has been ignored as a delivery agent, particularly in the area of theranostics, because of two major limitations: Its excitation wavelength is below 400 nm, and it is nonfluorescent. We have overcome these limitations by incorporating a 2-(2'-hydroxyphenyl)benzothiazole (HBT) appendage capable of rapid excited-state intramolecular proton transfer (ESIPT). The ESIPT effect also provided two unique advantages: It assisted the deprotonation of the pHP group for faster release, and it was accompanied by a distinct fluorescence color change upon photorelease. In vitro studies showed that the p-hydroxyphenacyl-benzothiazole-chlorambucil conjugate presents excellent properties, such as real-time monitoring, photoregulated drug delivery, and biocompatibility.

Fluorene-morpholine-based organic nanoparticles: lysosome-targeted pH-triggered two-photon photodynamic therapy with fluorescence switch on-off.

Nanocarrier-mediated photodynamic therapy (PDT) is an effective tool for anti-tumour treatment due to the targeted and image-guided delivery of photosensitizers (PSs) to diseased tissues. These nanocarriers range from inorganic, ceramic, polymeric to biological nanoparticles (NPs). Such PS-grafted bicomponent nanocarriers have limitations like (i) difficulty in surface modification, (ii) lower loading percentages of the therapeutic agent, (iii) unstable physical encapsulation, etc. By any means, if we can prepare PSs directly as NPs then we can surpass the above drawbacks. Hence, we synthesised new two-photon fluorene-functionalised morpholine (Fluo-Mor)-based organic NPs that showed strong fluorescence and profound photodynamic therapy (PDT) activity only in acidic medium. Such a pH-responsive appearance of fluorescence enables Fluo-Mor NPs for the real time monitoring of photodynamic therapeutic activity selectively in low-pH organelles viz. lysosome. Cytotoxicity of Fluo-Mor NPs was monitored using time-dependent and dose-dependent cancer cell viability assay and confocal imaging.

Coumarin-benzothiazole-chlorambucil (Cou-Benz-Cbl) conjugate: an ESIPT based pH sensitive photoresponsive drug delivery system.

We have developed an ESIPT based drug delivery system (DDS), Cou-Benz-Cbl conjugate, by incorporating a benzothiazole group at the 8th position of the 7-hydroxy-coumarin moiety for pH sensitive fluorescence properties and photocontrolled release of the anticancer drug chlorambucil. The Cou-Benz-Cbl conjugate exhibited unique photophysical properties like good absorbance at around 350 nm, a large Stokes shift (∼151 nm) and pH sensitive fluorescence properties. The pH sensitive fluorescence properties of the Cou-Benz-Cbl conjugate can be ascribed to an ESIPT turn "on and off" mechanism. At physiological pH, the ESIPT gets turned "off" and a blue fluorescence of the coumarin moiety was observed, but at acidic pH, the ESIPT gets turned "on" and a green fluorescence was noted. Photolysis of the Cou-Benz-Cbl conjugate using UV light of wavelength ≥365 nm resulted in the efficient release of the anticancer drug chlorambucil. Cellular uptake studies revealed that the Cou-Benz-Cbl conjugate was easily internalized inside the cancer cells. Further, an MTT assay showed that the Cou-Benz-Cbl conjugate has a good biocompatibility and low cytotoxicity towards the MDA-MB-231 cell line, whereas upon exposure to UV light, the Cou-Benz-Cbl conjugate exhibited enhanced cytotoxicity compared to the free drug due to the effective release of the anticancer drug chlorambucil inside the cancer cell.

1-Acetylpyrene-salicylic acid: photoresponsive fluorescent organic nanoparticles for the regulated release of a natural antimicrobial compound, salicylic acid.

Photoresponsive 1-acetylpyrene-salicylic acid (AcPy-SA) nanoparticles (NPs) were developed for the regulated release of a natural antimicrobial compound, salicylic acid. The strong fluorescent properties of AcPy-SA NPs have been extensively used for potential in vitro cell imaging. The phototrigger capability of our newly prepared AcPy-SA NPs was utilized for the efficient release of an antimicrobial compound, salicylic acid. The photoregulated drug release of AcPy-SA NPs has been shown by the subsequent switching off and on of a visible-light source. In vitro biological studies reveal that AcPy-SA NPs of ∼68 nm size deliver the antimicrobial drug salicylic acid into the bacteria cells (Pseudomonas aeruginosa) and efficiently kill the cells upon exposure to visible light (≥410 nm). Such photoresponsive fluorescent organic NPs will be highly beneficial for targeted and regulated antimicrobial drug release because of their biocompatible nature, efficient cellular uptake, and light-induced drug release ability.

Benzo[a]acridinylmethyl esters as pH sensitive fluorescent photoactive precursors: synthesis, photophysical, photochemical and biological applications.

A newsworthy class of carboxylate esters based on the (benzo[a]acridin-12-yl)methyl (BAM) chromophore has been shown to perform dual functions as a "pH sensitive fluorescent probe" and a "phototrigger" for acids. The photophysical properties of all the BAM ester conjugates were investigated and found to be highly sensitive to solvent polarity, H-bonding capability and pH of the environment. On irradiation using UV light (≥410 nm), BAM ester conjugates underwent heterolytic cleavage of C-O bonds resulting in efficient release of carboxylic and amino acids. Interestingly, the newly synthesized BAM chromophore was also explored for the construction of a drug delivery system (DDS). In the current DDS, the BAM chromophore plays two important roles: (i) a "fluorophore" for cell imaging and (ii) a "phototrigger" for the drug release. In vitro biological studies revealed that the newly developed BAM based DDS has a good biocompatibility, cellular uptake properties and efficient photoregulated anticancer drug release ability.