Coordination networks for the recognition of oxo-anions.

Crystalline coordination networks with an infinite extended framework, also known as coordination polymers (CPs) or metal-organic frameworks (MOFs), have attracted significant attention owing to their tremendous performance in an extensive range of applications. The unique structural features and high stability of coordination networks are responsible for their utilization and potential in diverse fields especially in the area of sensing using luminescent CPs/MOFs. The recognition of toxic oxo-anions present in water is a crucial and first step towards environmental remediation, mainly in the case of water pollution. Accordingly, the utilization of luminescent coordination networks has received significant interest, particularly for the recognition of various toxic oxo-anions, which are considered a threat to aquatic life and the environment. In this frontier article, we summarize recent reports on luminescent CPs/MOFs, their utilization for the sensing of oxo-anions and the chemistry of the interaction of oxo-anions with CPs/MOFs, which is responsible for tuning their optical signals.

Long Range Emissive Water-Soluble Fluorogenic Molecular Platform for Imaging Carbon Monoxide in Live Cells.

Despite its murderous act, carbon monoxide (CO) is found to be a very crucial small gaseous messenger molecule in dictating prime biological and physiological processes. Determination of endogenous or exhaled CO levels can throw significant light on smoking status and can be used as a breath biomarker of inflammatory diseases. Therefore, fluorescence imaging of CO in biofluids will empower one with the minute details of various disease states that involve CO. Unfortunately, such efficient fluorescent probes are less in number and also associated with tedious protocols. This enticed our attention and inspired us to look upon developing perceptive imaging agents for CO in a living system. In this report, a resorufin-based "turn-on" orange emissive molecular probe has been successfully utilized to detect CO in an aqueous system. The mono protection of a resorufin unit with an allyl chloroformate furnished a weakly fluorescent small molecular probe P1. Further, the P1+Pd2+ ensemble has been successfully developed in situ using PdCl2 (as Pd2+) and utilized as a light-up signaling mechanism tool for the sensing of CO at the nanomolar level (62 nM) through deprotection mechanism. The probe selectively detects CO without any interference from other anions, gasotransmitters and fatty acids. The present integrated probe P1+Pd2+ system has been found to be highly sensitive to detect CO in cellular systems as well.

Delivery of siRNA in vitro and in vivo using PEI-capped porous silicon nanoparticles to silence MRP1 and inhibit proliferation in glioblastoma.

BACKGROUND: Multidrug resistance-associated protein 1 (MRP1) overexpression plays a major role in chemoresistance in glioblastoma multiforme (GBM) contributing to its notorious deadly nature. Although MRP1-siRNA transfection to GBM in vitro has been shown to sensitise the cells to drug, MRP1 silencing in vivo and the phenotypic influence on the tumour and normal tissues upon MRP1 down-regulation have not been established. Here, porous silicon nanoparticles (pSiNPs) that enable high-capacity loading and delivery of siRNA are applied in vitro and in vivo. RESULT: We established pSiNPs with polyethyleneimine (PEI) capping that enables high-capacity loading of siRNA (92 µg of siRNA/mg PEI-pSiNPs), and optimised release profile (70% released between 24 and 48 h). These pSiNPs are biocompatible, and demonstrate cellular uptake and effective knockdown of MRP1 expression in GBM by 30%. Also, siRNA delivery was found to significantly reduce GBM proliferation as an associated effect. This effect is likely mediated by the attenuation of MRP1 transmembrane transport, followed by cell cycle arrest. MRP1 silencing in GBM tumour using MRP1-siRNA loaded pSiNPs was demonstrated in mice (82% reduction at the protein level 48 h post-injection), and it also produced antiproliferative effect in GBM by reducing the population of proliferative cells. These results indicate that in vitro observations are translatable in vivo. No histopathological signs of acute damage were observed in other MRP1-expressing organs despite collateral downregulations. CONCLUSIONS: This study proposes the potential of efficient MRP1-siRNA delivery by using PEI-capped pSiNPs in achieving a dual therapeutic role of directly attenuating the growth of GBM while sensitising residual tumour cells to the effects of chemotherapy post-resection.

Novel Gd-Loaded Silicon Nanohybrid: A Potential Epidermal Growth Factor Receptor Expressing Cancer Cell Targeting Magnetic Resonance Imaging Contrast Agent.

Continuing our research efforts in developing mesoporous silicon nanoparticle-based biomaterials for cancer therapy, we employed here porous silicon nanoparticles as a nanocarrier to deliver contrast agents to diseased cells. Nanoconfinement of small molecule Gd-chelates (L1-Gd) enhanced the T1 contrast dramatically compared to distinct Gd-chelate (L1-Gd) by virtue of its slow tumbling rate, increased number of bound water molecules, and their occupancy time. The newly synthesized Gd-chelate (L1-Gd) was covalently grafted on silicon nanostructures and conjugated to an antibody specific for epidermal growth factor receptor (EGFR) via a hydrazone linkage. The salient feature of this nanosized contrast agent is the capability of EGFR targeted delivery to cancer cells. Mesoporous silicon nanoparticles were chosen as the nanocarrier because of their high porosity, high surface area, and excellent biodegradability. This type of nanosized contrast agent also performs well in high magnetic fields.

Tri-color emission and colorimetric recognition of acetate using semicarbazide and thio-semicarbazide derivatives: Experimental and computational studies.

Two new fluorescence probes having semicarbazide (DSC) and thio-semicarbazide (DTSC) units have been derived upon reaction with 2-hydroxy-5-methylbenzene-1,3-dialdehyde. Both the probes show excellent selectivity for acetate ion in DMSO medium whereby DTSC generates tricolor emission. The association constants of DSC and DTSC for acetate are 6.6×10(4)M(-1) and 2×10(3)M(-1) respectively with corresponding detection limits, 1.06×10(-7)M and 2.5×10(-6)M. Density functional theoretical (DFT) studies nicely demonstrate the interaction between the DTSC and acetate ion.

Exploring 1,4-dihydroxyanthraquinone as long-range emissive ratiometric fluorescent probe for signaling Zn(2+)/PO4(3-): Ensemble utilization for live cell imaging.

Fluorescent 1,4-dihydroxyanthraquinone 1 was found to demonstrate its ratiometric signaling property upon interaction with divalent zinc (Zn(2+)). While the probe itself exhibited fluorescence emission in the yellow region (λem=544 nm and 567 nm), binding with Zn(2+) induced strong emission in the orange region (λem=600 nm) which was mainly due to a combination of CHEF and ICT mechanism. The probe was found to be highly sensitive toward the detection of zinc and the limit of detection (LOD) was calculated to be 9×10(-7) M. The possibility of using this probe for real-time analysis was strongly supported by the striking stability of fluorescence signal for more than five days with similar fluorescence intensity as observed during instant signaling. The present probe works within physiological pH range and is devoid of any interference caused by the same group elements such as Cd(2+)/Hg(2+). The probe possesses excellent excitation/emission wavelength profile and can penetrate cell membrane to image low concentration of zing inside living system. The in situ formed zinc-probe ensemble was further explored as ratiometric sensing platform for detecting another bio-relevant analyte phosphate anion through a zinc-displacement approach.

Highly photostable zinc selective molecular marker bearing flexible pivotal unit: opto-fluorescence enhancement effect and imaging applications in living systems.

Novel molecular probes for imaging zinc in biological systems are gaining interest as they help in understanding the role of zinc in regulating various bio-events. In this regard, a new C2-symmetric molecular system has been developed and successfully applied as light-up material for signaling divalent zinc with green emission. The fluorescence enhancement was highly zinc specific and this newly developed probe bears a submicromolar detection capability. While probe and the ensemble -Zn(2+) exhibited remarkably high photostability, light-triggered fluorescence enhancement was observed in the case of -Zn(2+). The nature of the -Zn(2+) complex and the associated spectral shift are further supported by theoretical calculations. As the present probe absorbs in the visible region and emits in the green, it was preferred as a potential material for imaging zinc in biological systems including animal and plant cells such as pollen grains and fish egg cells. Such fluorescence imaging of zinc revealed the efficacy of the probe in detection and localization of zinc in various biological systems.

Triazole-based Zn²âº-specific molecular marker for fluorescence bioimaging.

Fluorescence bioimaging potential, both in vitro and in vivo, of a yellow emissive triazole-based molecular marker has been investigated and demonstrated. Three different kinds of cells, viz Bacillus thuringiensis, Candida albicans, and Techoma stans pollen grains were used to investigate the intracellular zinc imaging potential of 1 (in vitro studies). Fluorescence imaging of translocation of zinc through the stem of small herb, Peperomia pellucida, having transparent stem proved in vivo bioimaging capability of 1. This approach will enable in screening cell permeability and biostability of a newly developed probe. Similarly, the current method for detection and localization of zinc in Gram seed sprouts could be an easy and potential alternative of the existing analytical methods to investigate the efficiency of various strategies applied for increasing zinc-content in cereal crops. The probe-zinc ensemble has efficiently been applied for detecting phosphate-based biomolecules.

Cysteamine-based cell-permeable Zn(2+)-specific molecular bioimaging materials: from animal to plant cells.

Structure-interaction/fluorescence relationship studies led to the development of a small chemical library of Zn(2+)-specific cysteamine-based molecular probes. The probe L5 with higher excitation/emission wavelengths, which absorbs in the visible region and emits in the green, was chosen as a model imaging material for biological studies. After successful imaging of intracellular zinc in four different kinds of cells including living organisms, plant, and animal cells, in vivo imaging potential of L5 was evaluated using plant systems. In vivo imaging of translocation of zinc through the stem of a small herb with a transparent stem, Peperomia pellucida, confirmed the stability of L5 inside biological systems and the suitability of L5 for real-time analysis. Similarly, fluorescence imaging of zinc in gram sprouts revealed the efficacy of the probe in the detection and localization of zinc in cereal crops. This imaging technique will help in knowing the efficiency of various techniques used for zinc enrichment of cereal crops. Computational analyses were carried out to better understand the structure, the formation of probe-Zn(2+) complexes, and the emission properties of these complexes.