Single component photoresponsive fluorescent organic nanoparticles: a smart platform for improved biomedical and agrochemical applications.

In the last two decades, light responsive nano drug delivery systems (DDSs) have gained considerable importance, particularly in the area of biology and medicine. In general, light responsive nano DDSs are bicomponent and constructed using two ingredients, namely a nanocarrier and a phototrigger. The synthesis of these bicomponent nano DDSs requires multiple steps, which limits their applications. Hence, we have reported single component light responsive nano DDSs using fluorescent organic nanoparticles (FONPs) which acted both as a nanocarrier and a phototrigger. This feature article provides an overview of recently developed light responsive single component FONPs and their applications in the regulated release of anticancer drugs, gasotransmitters, antibacterial agents, and pesticides, and also as efficient PDT agents. We have summarised the synthesis, characterisation, and photophysical, photochemical, and in vitro behaviours of these light responsive FONPs. In addition, we also discussed the advantages of using FONPs as a nano DDS for cellular studies like: excellent biocompatibility, efficient cellular internalisation, real time monitoring of the drug release ability inside the cells, and enhanced cytotoxicity due to regulated release of bioactive molecules inside the cells.

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.

Efficient removal of Chromium(VI) from aqueous solution using chitosan grafted graphene oxide (CS-GO) nanocomposite.

The present study involves the adsorption of hexavalent Chromium(Cr(VI)) using chitosan grafted graphene oxide (CS-GO) nanocomposite in batch mode. The CS-GO nanocomposite material was prepared by ultrasonic irradiation technique. The CS-GO adsorbent was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and Tunnelling electron microscopy (TEM), followed by Cr(VI) adsorption studies. The adsorption capacity of 104.16 mg/g was achieved at pH 2.0, in the contact time of 420 min. The adsorption process was described by the pseudo second order kinetic and Langmuir isotherm model. The nano-microstructural investigation validates the successful adsorption of Cr(VI) on CS-GO nanocomposite. The CS-GO material is recyclable up to 10 cycles with the minimum loss in adsorption capacity.

Ultrasonic-assisted synthesis of graphene oxide - fungal hyphae: An efficient and reclaimable adsorbent for chromium(VI) removal from aqueous solution.

In this study, a hybrid film bio-nanocomposite material was developed based on the graphene oxide/fungal hyphae (GO-FH) interaction. The developed GO-FH bio-nanocomposite material was used for the removal of hexavalent chromium from aqueous solution. The GO-FH bio-nanocomposite material was prepared by ultrasonic irradiation technique. The synthesized GO-FH bio-nanocomposite material was characterized by XRD, FT-IR, SEM, TEM and TGA. The adsorption experiments were carried out in batch mode to optimize parameters such as pH, adsorbent dosage, initial Cr(VI) ion concentration, contact time and shaking speed. The results indicated that the adsorption of Cr(VI) onto GO-FH bio-nanocomposite material was pH dependant, with the maximum adsorption capacity of 212.76 mg/g occurred at pH 2.0. The adsorption studies followed, Langmuir isotherm and pseudo second order kinetic model. Findings demonstrates that GO-FH bio-nanocomposite material exhibited excellent regeneration performance.

Ultrasound-assisted synthesis of metal organic framework for the photocatalytic reduction of 4-nitrophenol under direct sunlight.

In this study, the metal organic framework MOF [Zn(BDC)(DMF)] crystal was synthesized via ultrasonic irradiation and solvothermal method. The synthesized MOF [Zn(BDC)(DMF)] crystal was characterized by PXRD, FTIR, FESEM-EDX, TGA, UV-DRS and BET. The catalytic activity of MOF [Zn(BDC)(DMF)] was investigated by 4-nitrophenol (4-NP) degradation under direct sunlight irradiation. The influence of various degradation parameters such as initial 4-NP concentration, dosage, pH and H2O2 concentration were investigated. The results indicated that the synthesized MOF [Zn(BDC)(DMF)] exhibited strong photocatalytic activity in the presence of NaBH4 under sunlight irradiation and the reduction of 4-NP to 4-aminophenol (4-AP) completed within 10 min. The study provides the synthesized MOF [Zn(BDC)(DMF)] crystal can be used as a high performance catalyst for the treatment of dyes in wastewater.

Preparation of graphene oxide/chitosan/ferrite nanocomposite for Chromium(VI) removal from aqueous solution.

A magnetically modified graphene oxide/chitosan/ferrite (GCF) nanocomposite material was synthesized and exploited for removal of Chromium(VI) from aqueous solution. The GCF nanocomposite material was characterized by powder-X-ray diffraction (powder-XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope- energy dispersive X-ray (SEM-EDX) analysis, transmission electron microscopy (TEM) thermogravimetric analysis (TGA), UV-vis diffusive reflectance spectra and Brunauer-Emmett-Teller (BET) analysis. The effect of pH, adsorbent dose, contact time and initial Cr(VI) metal ion concentration were studied in batch process. The GCF nanocomposite material showed an adsorption capacity of 270.27 mg g-1 for Cr(VI) at pH 2.0. The adsorption mechanism of GCF adsorbent material was well described by Langmuir isotherm and pseudo second order kinetic model, with a high regression coefficient (<0.99). The results have shown that GCF nanocomposite material can be used as a suitable adsorbent for removal of Cr(VI) from wastewater.

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.

Adsorption of Pb(II) from aqueous solution using a magnetic chitosan/graphene oxide composite and its toxicity studies.

This study involves the adsorption of lead using magnetic chitosan/graphene oxide (MCGO) composite material in batch mode. The MCGO composite material was synthesized via modified Hummers method. The MCGO composite material was characterized by powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), Tunnelling electron microscopy (TEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) and UV-vis diffusive reflectance spectra. The adsorption mechanism of MCGO composite material was well described by Langmuir isotherm and pseudo second order kinetic model, with a high regression coefficient (<0.99). The MCGO composite material was applied for the removal of lead metal from aqueous solution. We have also evaluated toxicity of synthesized MCGO composite material by examining on A549 cells. The results have shown that MCGO material showed viable cell percentage of 53.7% at 50 µg and 44.8% at 100 µg.

NIR fluorescent organic nanoparticles for photoinduced nitric oxide delivery with self monitoring and real time reporting abilities.

Nitric oxide photodonor (NOD) conjugated perylene tetracarboxylate ester (TPT) based fluorescent organic TPT(NOD)4 nanoparticles (NPs) with aggregation induced NIR emission have shown photoinduced nitric oxide delivery along with a red to green emission transition. Time dependent imaging and dose dependent cytotoxicity studies of these NPs using U87MG cells demonstrate the self monitoring and real time reporting abilities and potential anticancer activity of the system, respectively.

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.

Synthesis, photochemistry, DNA cleavage/binding and cytotoxic properties of fluorescent quinoxaline and quinoline hydroperoxides.

Novel fluorescent quinoxaline and quinoline hydroperoxides were shown to perform dual role as both fluorophores for cell imaging and photoinduced DNA cleaving agents. Photophysical studies of newly synthesized quinoxaline and quinoline hydroperoxides showed that they all exhibited moderate to good fluorescence. Photolysis of quinoxaline and quinoline hydroperoxides in acetonitrile using UV light above 350nm resulted in the formation of corresponding ester compounds via γ-hydrogen abstraction by excited carbonyl chromophore. Single strand DNA cleavage was achieved on irradiation of newly synthesized hydroperoxides by UV light (⩾350nm). Both hydroxyl radicals and singlet oxygen were identified as reactive oxygen species (ROS) responsible for the DNA cleavage. Further, we showed quinoline hydroperoxide binds to ct-DNA via intercalative mode. In vitro biological studies revealed that quinoline hydroperoxide has good biocompatibility, cellular uptake property and cell imaging ability. Finally, we showed that quinoline hydroperoxide can permeate into cells efficiently and may cause cytotoxicity upon irradiation by UV light.

Photoresponsive quinoline tethered fluorescent carbon dots for regulated anticancer drug delivery.

A photoresponsive nano drug delivery system (DDS) was constructed using two new ingredients: fluorescent carbon dots and a quinoline based phototrigger. The strong fluorescent properties of carbon dots have been explored for in vitro cellular imaging application, and the phototrigger ability of quinoline was exploited for efficient anticancer drug release using both one-photon and two-photon excitation.

1,3,5-Trisubstituted benzenes as fluorescent photoaffinity probes for human carbonic anhydrase II capture.

The synthesis of small molecule based 1,3,5-trisubstituted benzenes for photo-mediated capture of human carbonic anhydrase II with visualisation by fluorescence is described.

Azido carbonyl compounds as DNA cleaving agents.

Irradiation of azido carbonyl compounds using UV light (≥310 nm) produced triplet alkyl nitrenes and aroyl radicals, which resulted in efficient cleavage of single strand DNA at pH 7.0. DNA cleaving ability of azido carbonyl compounds was found to be dependent on its concentration and substituents on its aromatic ring. Further, newly synthesized naphthalene based azido carbonyl compounds showed DNA cleavage ability at longer wavelength of UV light (≥350 nm) and also binding studies revealed that they bind to ct-DNA by weak intercalation mode.

Photoinduced DNA cleavage by anthracene based hydroxamic acids.

Two different series of naphthalene and anthracene based hydroxamic acids having amino acid derivatives were synthesized. Single strand DNA cleavage was achieved on irradiation of newly synthesized hydroxamic acids by UV light (≥350nm). Both reactive oxygen species (ROS) and generated radicals from hydroxamic acids were shown to be responsible for the DNA cleavage. Further, DNA cleaving ability of hydroxamic acids was found to be dependent on its concentration and on its structure.

Application of photoremovable protecting group for controlled release of plant growth regulators by sunlight.

We report a novel technique for controlled release of plant growth regulators (PGRs) by sunlight using photoremovable protecting group (PRPG) as a delivery device. In the present work, carboxyl-containing PGRs of the auxin group [indoleacetic acid (IAA) and naphthoxyacetic acid (NOAA)] were chemically caged using PRPGs of coumarin derivatives. Photophysical studies showed that caged PGRs exhibited good fluorescence properties. Irradiation of caged PGRs by sunlight in both aqueous ethanol and soil media resulted in controlled release of PGRs. The results of the bioactivity experiments indicated that caged PGRs showed better enhancement in the root and shoot length growth of Cicer arietinum compared to PGRs after 10days of sunlight exposure. Our results indicated that use of PRPG as a delivery device for controlled release of PGRs by sunlight in soil holds great interest for field application since it can overcome the rapid loss of PGRs in environmental conditions.

Supported bilayer lipid membrane arrays on photopatterned self-assembled monolayers.

This work demonstrates the use of photocleavable cholesterol derivatives to create supported bilayer lipid membrane arrays on silica. The photocleavable cholesteryl tether is attached to the surface by using the reaction of an amine-functionalized self-assembled monolayer (SAM) and the N-hydroxysuccinimide-based reagent 9. The resultant SAM contains an ortho-nitrobenzyl residue that can be cleaved by photolysis by using soft (365 nm) UV light regenerating the original amine surface, and which can be patterned using a mask. The photoreaction yield was approximately 75 % which was significantly higher than previously found for related ortho-nitrobenzyl photochemistry on gold substrates. The SAMs were characterized by means of contact angle measurements, ellipsometry and X-ray photoelectron spectroscopy. Patterned surfaces were characterized with SEM and AFM. After immersing the patterned surface into a solution containing small unilamellar vesicles of egg phosphatidylcholine (PC), supported lipid membranes were formed comprised of lipid bilayer over the amine functionalized "hydrophilic" regions and lipid monolayer over the cholesteryl "hydrophobic" regions. This was confirmed by fluorescence microscopy and AFM. FRAP studies yielded a lateral diffusion coefficient for the probe molecule of 0.14+/-0.05 microm(2) s(-1) in the bilayer regions and approximately 0.01 microm(2) s(-1) in the monolayer regions. This order of magnitude difference in diffusion coefficients effectively serves to isolate the bilayer regions from one another, thus creating a bilayer array.

A novel method to fabricate patterned bilayer lipid membranes.

We introduce a new method for forming tethered bilayer lipid membranes on surfaces patterned using a photocleavable self-assembled monolayer (SAM). A SAM terminated with a hydrophobic fluorocarbon residue was bound to a gold surface through a link containing a photocleavable ortho-nitrobenzyl moiety. Hydrophilic regions were produced by irradiation with soft UV (365 nm) through a photomask. The patterned surface was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Tethered bilayer lipid membranes with well-defined bilayer and monolayer regions were then formed by exposure to egg PC vesicles. The membranes had resistance and capacitance values of 0.52 MOmega.cm2 and 0.83 microF.cm-2, respectively.