Shrabani Barman

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.

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.

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.

Targeted photoresponsive TiO2–coumarin nanoconjugate for efficient combination therapy in MDA-MB-231 breast cancer cells: synergic effect of photodynamic therapy (PDT) and anticancer drug chlorambucil

Coupling of photodynamic therapy (PDT) with chemotherapy is an emerging treatment modality because of its ability to improve the antitumor effect and reduce the toxicity of the anticancer agents. Metallic NPs, silica NPs and carbon nanotubes have become rising stars as drug carriers for both photosensitizers and chemotherapeutic agents. But to date there are only a few reports using the aforesaid NPs as a platform for PDT combined with chemotherapy. Hence, we have developed a targeted metallic single nanoparticle system for the amalgamation of PDT with chemotherapy. The NPs for combination therapy have been constructed using two main ingredients: folic acid decorated TiO2 NPs and coumarin chromophore. The newly synthesized coumarin chromophore performed three important roles: (i) being a fluorophore for cell imaging, (ii) photosensitizer for PDT and (iii) a phototrigger for regulated anticancer drug release. Furthermore, folic acid decorated TiO2 NPs help with internalization of the drug to inside the cancer cells. In vitro biological studies reveal that this targeted combination treatment results in an enhanced tumor accumulation of TiO2 nanoparticles, significant inhibition of tumor cell proliferation and increased induction of apoptosis. Such metallic photoresponsive NPs that are benign to the physiological system, permeate easily into cells and exhibit high therapeutic efficacy, will have significant prospects for use against drug-resistant tumors.

1-Acetylferroceneoxime-based photoacid generators: application towards sol–gel transformation and development of photoresponsive polymer for controlled wettability and patterned surfaces

A newsworthy class of carboxylate and sulfonate esters of 1-acetylferroceneoxime has been demonstrated as non-ionic photoacid generators (PAGs). PAGs based on 1-acetylferroceneoxime were synthesized in good yields by simple treatment of 1-acetylferroceneoxime with various carboxylic and sulfonyl chlorides. Newly developed PAGs of 1-acetylferroceneoxime showed good absorbance >350 nm. On irradiation using UV light (≥365 nm), carboxylates and sulfonates of 1-acetyl ferroceneoxime in aqueous acetonitrile solvent underwent efficient homolytic cleavage of N–O bond, resulting in the generation of carboxylic and sulphonic acids, respectively, with high chemical and good quantum yields. Further, we demonstrated the application of our newly developed 1-acetylferroceneoxime-based PAGs for gelation of biopolymer alginate on UV irradiation. More interestingly, we synthesized a ferroceneoxime bound photoresponsive polymer, 1-acetylferroceneoxime-polycaprolactone (AFO-PCL), and demonstrated its controlled surface wettability and generation of patterned surfaces.

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.