Nanoantenna enhanced terahertz interaction of biomolecules.

Terahertz time-domain spectroscopy (THz-TDS) is a non-invasive, non-contact and label-free technique for biological and chemical sensing as THz-spectra are less energetic and lie in the characteristic vibration frequency regime of proteins and DNA molecules. However, THz-TDS is less sensitive for the detection of micro-organisms of size equal to or less than λ/100 (where, λ is the wavelength of the incident THz wave), and molecules in extremely low concentration solutions (like, a few femtomolar). After successful high-throughput fabrication of nanostructures, nanoantennas were found to be indispensable in enhancing the sensitivity of conventional THz-TDS. These nanostructures lead to strong THz field enhancement when in resonance with the absorption spectrum of absorptive molecules, causing significant changes in the magnitude of the transmission spectrum, therefore, enhancing the sensitivity and allowing the detection of molecules and biomaterials in extremely low concentration solutions. Herein, we review the recent developments in ultra-sensitive and selective nanogap biosensors. We have also provided an in-depth review of various high-throughput nanofabrication techniques. We also discussed the physics behind the field enhancements in the sub-skin depth as well as sub-nanometer sized nanogaps. We introduce finite-difference time-domain (FDTD) and molecular dynamics (MD) simulation tools to study THz biomolecular interactions. Finally, we provide a comprehensive account of nanoantenna enhanced sensing of viruses (like, H1N1) and biomolecules such as artificial sweeteners which are addictive and carcinogenic.

Deterministic coupling of quantum emitters in WSe2 monolayers to plasmonic nanocavities.

We discuss coupling of site-selectively induced quantum emitters in exfoliated monolayers of WSe2 to plasmonic nanostructures. Gold nanorods of 20 nm-240 nm size, which are arranged in pitches of a few micrometers on a dielectric surface, act as seeds for the formation of quantum emitters in the atomically thin materials. We observe characteristic narrow-band emission signals from the monolayers, which correspond well with the positions of the metallic nanopillars with and without thin dielectric coating. Single photon emission from the emitters is confirmed by autocorrelation measurements, yielding g2(τ = 0) values as low as 0.17. Moreover, we observe a strong co-polarization of our single photon emitters with the frequency matched plasmonic resonances, as a consequence of light-matter coupling. Our work represents a significant step towards the scalable implementation of coupled quantum emitter-resonator systems for highly integrated quantum photonic and plasmonic applications.

Quantum dots-nanogap metamaterials fabrication by self-assembly lithography and photoluminescence studies.

We present a new and versatile technique of self-assembly lithography to fabricate a large scale Cadmium selenide quantum dots-silver nanogap metamaterials. After optical and electron microscopic characterizations of the metamaterials, we performed spatially resolved photoluminescence transmission measurements. We obtained highly quenched photoluminescence spectra compared to those from bare quantum dots film. We then quantified the quenching in terms of an average photoluminescence enhancement factor. A finite difference time domain simulation was performed to understand the role of an electric field enhancement in the nanogap over this quenching. Finally, we interpreted the mechanism of the photoluminescence quenching and proposed fabrication method of new metamaterials using our technique.

Shape and Phase-Controlled One-Pot Synthesis of Air Stable Cationic AgCdS Nanocrystals, Optoelectronic and Electrochemical Hydrogen Evolution Studies.

CdS-based materials are extensively studied for photocatalytic water splitting. By incorporating Ag+ into CdS nanomaterials, the catalyst's charge carrier dynamic can be tuned for photo-electrochemical devices. However, photo-corrosion and air-stability of the heterostructures limit the photocatalytic device's performance. Here, a one-pot, single molecular source synthesis of the air-stable AgCdS ternary semiconductor alloy nanostructures by heat-up method is reported. Monoclinic and hexagonal phases of the alloy are tuned by judicious choice of dodecane thiol (DDT), octadecyl amine (ODA), and oleyl amine (OLA) as capping agents. Transmission electron microscope (TEM) and powder X-ray diffraction characterization of the AgCdS alloy confirm the monoclinic and hexagonal phase (wurtzite) formation. The high-resolution TEM studies confirm the formation of AgCdS@DDT alloy nanorods and their shape transformation into nano-triangles. The nanoparticle coalescence is observed for ODA-capped alloys in the wurtzite phase. Moreover, OLA directs mixed crystal phases and anisotropic growth of alloy. Optical processes in AgCdS@DDT nano-triangles show mono-exponential decay (3.97 ± 0.01 ns). The monoclinic phase of the AgCdS@DDT nanorods exhibits higher electrochemical hydrogen evolution activity in neutral media as compared to the AgCdS@ODA/OLA alloy nanocrystals. DDT and OLA-capped alloys display current densities of 14.1 and 14.7 mA cm-2 , respectively, at 0.8 V (vs RHE).

Neuroprotective validation of pectin in T2DM-induced allodynia and hyperalgesia in diabetic peripheral neuropathic pain.

AIM: To validate neuroprotective effect of pectin against neuropathic pain in diabetic rodents. MATERIAL AND METHOD: Pectin was isolated and characterised from different sources to validate its neuroprotective effect against T2DM associated neuropathic pain. The antioxidant activity of pectins was done by the DPPH method. Type-2 diabetes mellitus (T2DM) was induced in Wistar albino rats by high-fat diet and high-fat emulsion feeding for 2 weeks followed by a single i.p. of Sterptozotocin in 3rd week. The animals were grouped as positive control and Citrus sinensis (L.) Osbeck peel pectin (CSL-OP) as test group and treated for the next 4 weeks. Body weight and blood glucose were measured up to 8 weeks; however, behavioural assessment was done at the end of 5th to 8th week. RESULT: CSL-OP restored the reduced body weight and elevated blood glucose with increased pain threshold and improved walking performance. CONCLUSION: CSL-OP prevented progression of early diabetic neuropathy with anti-oxidant activity.

Computational Study and Synthesis of a New Class of Anticonvulsants with 6 Hz Psychomotor Seizure Test Activity: 2-(1,3-benzodioxol-5-yloxy)- N'-[substituted]-acetohydrazides.

BACKGROUND: About 50 million epileptic cases worldwide and 12 million in India are reported. Currently, available drugs yield adequate control of seizure in 60-70% of patients and show many toxic effects. These actualities provoked the search for novel, more efficacious and safer anticonvulsants. OBJECTIVE: The concatenation of 2-(1,3-benzodioxol-5-yloxy)-N'-[substituted]-acetohydrazides SA 1- 10 was designed by molecular hybridization, optimized by computational study and synthesized with the objective of obtaining a prototype of potent anticonvulsant molecules especially active against partial seizures. METHODS: Computational study was performed to calculate the pharmacophoric design, projection of the pharmacokinetic parameters and docking scores of the titled compounds with molecular targets of epilepsy. The anticonvulsant activity was ascertained by 6 Hz psychomotor seizure test. Minimal motor impairment showing neurotoxicity was assessed using the Rotarod test. RESULTS: Titled compounds possessed the indispensable elements of pharmacophore and displayed good binding affinity with molecular targets of epilepsy, such as GABA (A) alpha-1 & delta receptor, glutamate receptor, Na+/H+ exchanger and GABA- aminotransferase in docking studies. The most potent compound of the concatenation was 2-(1,3-benzodioxol-5-yloxy)-N'-[4-(4- chlorophenoxy)benzylidene]-acetohydrazide SA 4, showing 100% protection at four different time points with ED50 value 146.8 mg/kg at a TPE of 1 h in mice. CONCLUSION: The protection shown in 6 Hz test is implicated as the compound's ability to control partial seizures. Thus, the titled compounds can be considered as potential prototype candidates for antiepileptic therapy against partial seizures.

Design, Synthesis, Anticonvulsant Activity, Preclinical Study and Pharmacokinetic Performance of N-{[3-(4-chlorophenyl)-4-oxo-3, 4-dihydroquinazolin- 2-yl] methyl}, 2-[(2-isopropyl-5-methyl) 1-cyclo Hexylidene] Hydrazinecarboxamide.

BACKGROUND: N-{[3-(4-chlorophenyl)-4-oxo-3, 4-dihydroquinazolin-2-yl] methyl}, 2-[(2- isopropyl-5-methyl) 1-cyclohexylidene] hydrazinecarboxamide QS11 was designed by computational study. It possessed essential pharmacophoric features for anticonvulsant activity and showed good docking with iGluRs (Kainate) glutamate receptor. METHODS: QSAR and ADMET screening results suggested that QS11 would possess good potency for anticonvulsant activity. QS11 was synthesised and evaluated for its anticonvulsant activity and neurotoxicity. QS11 showed protection in strychnine, thiosemicarbazide, 4-aminopyridine and scPTZ induced seizure models and MES seizure model. QS11 showed higher ED50, TD50 and PI values as compared to the standard drugs in both MES and scPTZ screen. A high safety profile (HD50/ED50 values) was noted and hypnosis, analgesia, and anaesthesia were only observed at higher doses. No considerable increase or decrease in the concentration of liver enzymes was observed. Optimized QS11 was subjected to preclinical (in-vivo) studies and the pharmacokinetic performance of the sample was investigated. The result revealed that the pharmacokinetic performance of QS11 achieved maximum plasma concentrations (Cmax) of 0.315 ± 0.011 µg/mL at Tmax of 2.0 ± 0.13 h, area under the curve (AUC0-∞) value 4.591 ± 0.163 µg/ml x h, elimination half-life (T1/2) 6.28 ± 0.71 h and elimination rate constant was found 0.110 ± 0.013 h-1 . RESULTS AND CONCLUSION: Above evidences indicate that QS11 could serve as a lead for development of new antiepileptic drugs.

Role of chelates in treatment of cancer.

Chelates are used in cancer as cytotoxic agent, as radioactive agent in imaging studies and in radioimmunotherapy. Various chelates based on ruthenium, copper, zinc organocobalt, gold, platinum, palladium, cobalt, nickel and iron are reported as cytotoxic agent. Monoclonal antibodies labeled with radioactive metals such as yttrium-90, indium-111 and iodine-131 are used in radioimmunotherapy. This review is an attempt to compile the use of chelates as cytotoxic drugs and in radioimmunotherapy.

Augmentation of GABAergic neurotransmission by novel N-(substituted)-2-[4-(substituted)benzylidene]hydrazinecarbothioamides-a potential anticonvulsant approach.

New N-(substituted)-2-[4-(substituted)benzylidene]hydrazinecarbothioamides were designed, synthesized and evaluated for anticonvulsant activity and neurotoxicity. The anticonvulsant activity was established in three seizure models i.e. MES, scMET and 6 Hz model. The most active compound was N-(4-methoxyphenyl)-2-[4-(4-methylphenoxy) benzylidene]hydrazinecarbothioamide PT 30 which showed 100% protection in both MES and 6 Hz test. Compound PT 30 showed protection at three different time points in 6 Hz test at a dose of 100 mg/kg. Compound 2-[4-(4-Chlorophenoxy)benzylidene]-N-cyclohexylhydrazine carbothioamide PT 4 was also found to be active in both MES and 6 Hz test. Titled compounds exhibited good binding properties with epilepsy molecular targets GABA (A) delta and GABA (A) alpha-1 receptors, in LGA based flexible docking studies. Compounds PT 30 and PT 4 were found to elevate γ-aminobutyric acid (GABA) levels in the midbrain and medulla oblongata regions of rat brain. A computational study was carried out for calculation of pharmacophore pattern and prediction of pharmacokinetic properties.

A new class of anticonvulsants possessing 6 Hz psychomotor seizure test activity: 2-(1H-benzotriazol-1-yl)-N'-[substituted] acetohydrazides.

A series of 2-(1H-Benzotriazol-1-yl)-N'-[substituted]acetohydrazides were designed & synthesized keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant activity and neurotoxicity. The new compounds were characterized using FT-IR, 1H NMR, mass spectral data and elemental analysis. The anticonvulsant activity of the titled compounds was assessed using the 6 Hz psychomotor seizure test. The neurotoxicity was assessed using the rotorod method. The most active compound of the series was N'-[4-(1,3-Benzodioxol-5-yloxy)benzylidene]-2-(1H-benzotriazol-1-yl)acetohydrazide (BTA 9), which showed good activity with 75 % protection (3/4, 0.5 h) at a dose of 100 mg/kg in mice. All the compounds exhibited no neurotoxicity. A computational study was carried out for calculation of pharmacophore pattern and prediction of pharmacokinetic properties. Titled compounds have also exhibited good binding properties with epilepsy molecular targets such as glutamate, GABA (A) delta, GABA (A) alpha-1 receptors and Na/H exchanger, in Lamarckian genetic algorithm based flexible docking studies.

Design, synthesis and anticonvulsant evaluation of novel N-(4-substituted phenyl)-2-[4-(substituted) benzylidene]-hydrazinecarbothio amides.

Thirty six new N-(4-substituted phenyl)-2-[4-(substituted) benzylidene]-hydrazinecarbothioamides were synthesized and evaluated for anticonvulsant activity and neurotoxicity. The anticonvulsant activity was established in three seizure models i.e. MES, scMET and 6 Hz model. The most active compound was 2-[4-(4-chlorophenoxy)benzylidene]-N-(4-fluorophenyl)hydrazinecarbothioamide PC 31 which showed 100% protection at 0.5 h in the 6 Hz test. Compound 2-[4-(4-bromophenoxy) benzylidene]-N-(4-bromophenyl) hydrazinecarbothioamide PC 23 was found to be active in both the MES and 6 Hz test. A computational study was carried out from calculation of a pharmacophore pattern and the prediction of pharmacokinetic properties. Titled compounds have also exhibited good binding properties with epilepsy molecular targets such as glutamate, GABA (A) delta and GABA (A) alpha-1 receptors, in the Lamarckian genetic algorithm based on flexible docking studies.

Design & synthesis of N'-[substituted] pyridine-4-carbohydrazides as potential anticonvulsant agents.

A series of N'-[substituted] pyridine-4-carbohydrazides were designed and synthesized keeping in view the structural requirement of pharmacophore and evaluated for anticonvulsant activity and neurotoxicity. The anticonvulsant activity of the titled compounds was established after intraperitoneal administration in three seizure models, which include MES, scMET and 6 Hz model. The most active compound of the series was N'-[4-(4-fluorophenoxy)benzylidene]pyridine-4-carbohydrazide PCH 6, which showed a MES ED50 value of 128.3 mg/kg and 6 Hz ED50 value of 53.3 mg/kg in mice. The median toxic dose (TD50) was 343.6 mg/kg, providing compound PCH 6 with a protection index of 2.67 in the MES test and 6.44 in 6 Hz test. A computational study was also carried out, including calculation of pharmacophore pattern, prediction of pharmacokinetic properties and docking studies.

Role of chelates in magnetic resonance imaging studies.

Imaging studies are tests performed with a variety of techniques that produce pictures of the inside of a patient's body. Magnetic resonance imaging (MRI) is an imaging technique based on the principles of nuclear magnetic resonance. MRI uses a powerful magnetic field, radio waves, and a computer to produce detailed pictures of organs, soft tissues, bone, and virtually all other internal body structures. Chelates have a wide application in such imaging techniques. Chelates in imaging studies are used alone as radioactive agents or conjugated to monoclonal antibodies or to DNA as radioactive agents. Technetium chelates and gadolinium chelates are being widely used as magnetic resonance contrast media.