In this work, six new mixed ligand Schiff base metal complexes of [M2(L1)(X)2Cl4] type, (where, M = CoII, NiII, CuII, L1 = Schiff base ligand derived from 1‐pyrenecarboxaldehyde and 1,4‐bis[3‐aminopropyl]piperazine and X = pyrazine‐2‐carboxylic acid or 2,2′‐biimidazole) were synthesized and studied their biological activity and cytotoxicity. The synthesized Schiff base ligands, their metal complexes were characterized by Infrared, UV‐Visible spectroscopy, and elemental analysis. Density functional theory calculations were performed to examine the molecular geometry and frontier molecular orbital properties of complexes (1–6). The DNA binding ability of these complexes (1–6) was evaluated by in vitro spectroscopic (absorption and fluorescence) titrations, viscosity measurements, and in silica by molecular docking measurements. The results showed a good binding propensity with the binding constant from 2.65 × 104 to 3.38 × 105 M−1 in the order 6 > 5 > 4 > 3 > 2 > 1, respectively. All complexes exhibited a good binding affinity to BSA proteins with relatively higher binding constant values similar to the trend of DNA binding studies and where Cu (II) complexes have greater efficiency than Co (II) and Ni (II) complexes. The in vitro cytotoxic study of all the complexes was investigated in the cervical cancer (HeLa) cell line, which displayed IC50 values of 1.36–24.2 μM, signifying the potential of complexes for an operative anticancer drug. Metal complexes were also screened for antimicrobial properties, which showed virtuous inhibition than the free ligands.
Acetylcholinesterase (AChE) is a pivotal enzyme that is closely related with multiple neurological diseases, such as brain disorders or alterations in the neurotransmission and cancer. The development of convenient methods for imaging AChE activity in biological samples is very important to understand its mechanisms and functions in a living system. Herein, a fluorescent probe exhibiting emission in the near-infrared (NIR) region is developed to detect AChE and visualize biological AChE activities. This probe exhibits a quick response time, reasonable detection limit, and a large Stokes shift accompanied by the NIR emission. The probe has much better reactivity toward AChE than butyrylcholinesterase, which is one of the significant interfering substances. The outstanding specificity of the probe is proved by cellular imaging AChE activity and successful mapping in different regions of zebrafish. Such an effective probe can greatly contribute to ongoing efforts to design emission probes that have distinct properties to assay AChE in biological systems.
Formaldehyde (FA) is a colorless, flammable, foul-smelling chemical used in building materials and in the production of numerous household chemical goods. Herein, a fluorescent chemosensor for FA is designed and prepared using a selective organ-targeting probe containing naphthalimide as a fluorophore and hydrazine as a FA-binding site. The amine group of the hydrazine reacts with FA to form a double bond and this condensation reaction is accompanied by a shift in the absorption band of the probe from 438 nm to 443 nm upon the addition of FA. Further, the addition of FA is shown to enhance the emission band at 532 nm relative to the very weak fluorescent emission of the probe itself. Moreover, a high specificity is demonstrated towards FA over other competing analytes such as the calcium ion (Ca2+), magnesium ion (Mg2+), acetaldehyde, benzaldehyde, salicylaldehyde, glucose, glutathione, sodium sulfide (Na2S), sodium hydrosulfide (NaHS), hydrogen peroxide (H2O2), and the tert-butylhydroperoxide radical. A typical two-photon dye incorporated into the probe provides intense fluorescence upon excitation at 800 nm, thus demonstrating potential application as a two-photon fluorescent probe for FA sensing. Furthermore, the probe is shown to exhibit a fast response time for the sensing of FA at room temperature and to facilitate intense fluorescence imaging of breast cancer cells upon exposure to FA, thus demonstrating its potential application for the monitoring of FA in living cells. Moreover, the presence of the phenylsulfonamide group allows the probe to visualize dynamic changes in the targeted Golgi apparatus. Hence, the as-designed probe is expected to open up new possibilities for unique interactions with organ-specific biological molecules with potential application in early cancer cell diagnosis.
Bioinspired photosynthetic systems composed of photocatalysts and enzymes are a notable framework for converting CO2 to high-value chemicals. However, catalyst/enzyme deactivation and poor electron transfer kinetics in multistep photochemical processes severely limit their catalytic efficiencies. In this study, Janus-type DNA nanosheets (NSs) presenting two different DNA sequences on each face were utilized as a support for the selective immobilization of a Rh complex and formate dehydrogenase (FDH) for concerted catalytic reactions for CO2 reduction. Based on the face selectivity, DNA-conjugated Rh complex and FDH were immobilized on NSs into four different configurations: Rh complex on NS (NS1), FDH on NS (NS2), Rh complex and FDH on opposite faces of NS (NS3), FDH and Rh complex on the same face of NS (NS4). The catalytic system exhibited CO2 conversion efficiencies highly dependent on the spatial organization of Rh complex and FDH, showing the reactivity for the formate production in the order of NS1 coupled with free FDH > NS3 > NS2 coupled with free Rh complex > NS4 > free Rh complex and FDH. The NS1 coupled with free FDH showed turnover number (TON) of 1360 for the formate production based on NAD+, which is the highest value reported thus far for Rh-based photocatalyst/enzyme coupled systems. The results demonstrate that the compartmentalization of photocatalysts and biological enzymes is a viable approach for improving the efficiency of CO2 conversion and provide important design rules for building efficient artificial photosynthetic systems.
The synthesis of Pd@Pt core–shell nanocubes was achieved through a direct seed-mediated growth method. This process represents a simple and cost-effective way to produce core–shell nanocubes. The morphology of the Pd@Pt core–shell nanocubes varied from simple cubic to concave cubic, depending on the reducing agent and the Pt content. The selection of the reducing agent is important because the reduction rate is directly related to the shell growth. The catalytic activity and stability of the Pd@Pt core–shell nanocubes in the methanol oxidation reaction were different for the nanocubes with partial and full Pt shells.
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