[2,1,3]-Benzothiadiazole-Spaced Co-Porphyrin-Based Covalent Organic Frameworks for O2 Reduction.

Designing N-coordinated porous single-atom catalysts (SACs) for the oxygen reduction reaction (ORR) is a promising approach to achieve enhanced energy conversion due to maximized atom utilization and higher activity. Here, we report two Co(II)-porphyrin/ [2,1,3]-benzothiadiazole (BTD)-based covalent organic frameworks (COFs; Co@rhm-PorBTD and Co@sql-PorBTD), which are efficient SAC systems for O2 electrocatalysis (ORR). Experimental results demonstrate that these two COFs outperform the mass activity (at 0.85 V) of commercial Pt/C (20%) by 5.8 times (Co@rhm-PorBTD) and 1.3 times (Co@sql-PorBTD), respectively. The specific activities of Co@rhm-PorBTD and Co@sql-PorBTD were found to be 10 times and 2.5 times larger than that of Pt/C, respectively. These COFs also exhibit larger power density and recycling stability in Zn-air batteries compared with a Pt/C-based air cathode. A theoretical analysis demonstrates that the combination of Co-porphyrin with two different BTD ligands affords two crystalline porous electrocatalysts having different d-band center positions, which leads to reactivity differences toward alkaline ORR. The strategy, design, and electrochemical performance of these two COFs offer a pyrolysis-free bottom-up approach that avoids the creation of random atomic sites, significant metal aggregation, or unpredictable structural features.

Efficacious and sustained release of an anticancer drug mitoxantrone from new covalent organic frameworks using protein corona.

Solid porous and crystalline covalent organic frameworks (COFs) are characterized by their higher specific BET surface areas and functional pore walls, which allow the adsorption of various bioactive molecules inside the porous lattices. We have introduced a perylene-based COF, PER@PDA-COF-1, which acts as an effective porous volumetric reservoir for an anticancer drug, mitoxantrone (MXT). The drug-loaded COF (MXT-PER@PDA-COF-1) exhibited zero cellular release of MXT towards cancer cells, which can be attributed to the strong intercalation between the anthracene-dione motif of the drug and the perylene-based COF backbone. Here, we have introduced a strategy involving the serum-albumin-triggered intracellular release of mitoxantrone from MXT-PER@PDA-COF-1. The serum albumin acts as an exfoliating agent and as a colloidal stabilizer in PBS medium (pH = 7.4), rapidly forming a protein corona around the exfoliated COF crystallites and inducing the sustained release of MXT from the COF into tumorigenic cells.

Selective pathological and intracellular detection of human serum albumin by photophysical and electrochemical techniques using a FRET-based molecular probe.

A simple, easily synthesizable, low-cost, fluorescent turn-on probe is presented herein for the selective and quantitative detection of human serum albumin (HSA) in different biological fluids collected from patients with various clinical manifestations. The sensor can detect HSA level by both photophysical and electrochemical means. The developed probe is also efficient in rapid quantification of HSA level in single living cell, cell lysate and tissue extract with high sensitivity. Both higher (millimolar) and trace (micromolar) amount of serum albumin can be accurately quantified using this probe in vast array of biomedical samples. This chemical sensor is also used as a part of Förster Resonance Energy Transfer (FRET) based system adding further accuracy to the measurement technique. Intracellular concentrations of HSA can be measured as well as imaged using this newly synthesized probe. Electrochemical detection of HSA concentrations can also be achieved with this biosensor using a potentiostat. Thus, this probe offers a unique potential of diagnosing HSA levels directly in various biological samples, using its bimodal (i.e., photophysical and electrochemical) properties which is hitherto unknown till date.

Antibody-Conjugated Vitamin E-Derived Liposomes for Targeted Gene Transfer.

Construction of a vitamin E-based liposomal biomaterial and its ability to deliver therapeutic genes selectively across liver cancer cells are demonstrated herein. In humans, liver regulates the levels of α-tocopherol, i.e., vitamin E, and hepatic cells carry the machinery for its transport. To exploit the presence of tocopherol transport protein, we have selected an efficient gene transfecting α-tocopherol-based twin lipid bearing a hydroxyethylated headgroup and octamethylene spacer (TH8S) for liposome formation. Also, based on the abundancy of the low-density lipoprotein receptor (LDLr) on the cellular surface in the case of hepatocellular carcinoma, anti-LDLr monoclonal antibody is used to confer the targeting ability to liposomes. A facile thiol-maleimide click chemistry is used for antibody decoration on the liposomal surface. Selective delivery of reporter and therapeutic genes (GFP and p53) to cells of hepatic origin was observed using anti-LDLr-tagged TH8S liposomes. Cellular internalization by receptor-mediated endocytosis renders the bioconjugate highly specific as well as highly efficient. Compatibility of the designed material with human blood points to its safety of use in systemic circulation thereby highlighting its in vivo potential. Thus, we report here a versatile biomaterial derived from an essential vitamin that promises potential for targeted suicidal gene therapy.

Chelerythrine down regulates expression of VEGFA, BCL2 and KRAS by arresting G-Quadruplex structures at their promoter regions.

A putative anticancer plant alkaloid, Chelerythrine binds to G-quadruplexes at promoters of VEGFA, BCL2 and KRAS genes and down regulates their expression. The association of Chelerythrine to G-quadruplex at the promoters of these oncogenes were monitored using UV absorption spectroscopy, fluorescence anisotropy, circular dichroism spectroscopy, CD melting, isothermal titration calorimetry, molecular dynamics simulation and quantitative RT-PCR technique. The pronounced hypochromism accompanied by red shifts in UV absorption spectroscopy in conjunction with ethidium bromide displacement assay indicates end stacking mode of interaction of Chelerythrine with the corresponding G-quadruplex structures. An increase in fluorescence anisotropy and CD melting temperature of Chelerythrine-quadruplex complex revealed the formation of stable Chelerythrine-quadruplex complex. Isothermal titration calorimetry data confirmed that Chelerythrine-quadruplex complex formation is thermodynamically favourable. Results of quantative RT-PCR experiment in combination with luciferase assay showed that Chelerythrine treatment to MCF7 breast cancer cells effectively down regulated transcript level of all three genes, suggesting that Chelerythrine efficiently binds to in cellulo quadruplex motifs. MD simulation provides the molecular picture showing interaction between Chelerythrine and G-quadruplex. Binding of Chelerythrine with BCL2, VEGFA and KRAS genes involved in evasion, angiogenesis and self sufficiency of cancer cells provides a new insight for the development of future therapeutics against cancer.