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Positron emission tomography (PET) imaging of the translocator 18 kDa protein (TSPO) with radioligands has become an effective means of research in peripheral inflammatory conditions that occur in many diseases and cancers. The peripheral sterile inflammatory diseases (PSIDs) are associated with a diverse group of disorders that comprises numerous enduring insults including the cardiovascular, respiratory, gastrointestinal, or musculoskeletal system. TSPO has recently been introduced as a potential biomarker for peripheral sterile inflammatory diseases (PSIDs). The major critical issue related to PSIDs is its timely characterization and localization of inflammatory foci for proper therapy of patients. As an alternative to metabolic imaging, protein imaging expressed on immune cells after activation is of great importance. The five transmembrane domain translocator protein-18 kDa (TSPO) is upregulated on the mitochondrial cell surface of macrophages during inflammation, serving as a potential ligand for PET tracers. Additionally, the overexpressed TSPO protein has been positively correlated with various tumor malignancies. In view of the association of escalated TSPO expression in both disease conditions, it is an immensely important biomarker for PET imaging in oncology and PSIDs. In this review, we summarize the most outstanding advances on TSPO-targeted PSIDs and cancer in the development of TSPO ligands as a potential diagnostic tool, specifically discussing the last five years.

Quinazoline is an organic heterocyclic molecule in which two six-membered aromatic rings are fused. Two nitrogen atoms are present in the quinazoline molecule at 1 and 3 positions that is why it is also known as 1,3-diazanaphthalene. The presence of these two nitrogen atoms in 1,3-diazanaphthalene increases the usefulness of this molecule in the field of pharmaceutical sciences. Many reactions have been reported to prepare 1,3- diazanaphthalene by aminobenzonitrile, o-aminobenzohydrazide, aminobenzamide, aminoacetophenone, and aminobenzoketone under different solvent conditions, but condensation of anthranilic acid with an aromatic aldehyde is the most common method. Later, metal-free and solvent-free conditions dominated over the old methods. This review describes the synthesis of 1,3-diazanaphthalene under different metal catalysts, reagents, solvent- free conditions and under microwave radiation through nucleophilic substitution reaction, condensation, and aromatization. In biological sciences, 1,3-diazanaphthalene derivatives have got an important place due to their ability to bind to different target sites and subsequent discovery of many drug structures.

The high expression of the translocator protein (TSPO) makes it an ideal target for imaging and therapy. The present study is aimed at optimizing acetamidobenzoxazolone-based TSPO ligands by structural modification to overcome the limitations of TSPO ligands of the first two generations such as nonspecificity and polymorphism. Three different TSPO proteins, 2MGY, 4RYQ, and 4UC1, in the native and mutated form were chosen. Acetamidobenzoxazolones modified with phenylalanine methyl ester (methyl 2-(2-(5-bromo/chloro-2-oxobenzooxazol-3(2H)-yl)acetamido)-3-phenylpropanoate, ABPO-Br, ABPO-Cl) through better or comparable docking scores than the known TSPO ligands such as MBMP, FEBMP, FPBMP, and PK11195 are identified as potential TSPO ligands. ABPO-Cl and ABPO-Br were synthesized using phenylalanine methyl ester as a moiety for incorporation of the desired pharmacophoric feature. All the intermediates and final compounds were purified using column chromatography and analytical HPLC (purity > 97%). The purified compounds were characterized by 1H, 13C NMR and mass spectroscopy. Drug likeliness and comparative bioactivity analysis were performed using QikProp through prediction of various properties. Both analogs follow all the five Lipinski rules and three Jogersen’s rules predicting their drug likeliness. The other important aspects related to TSPO ligands such as blood-brain barrier penetration and better contrast have been predicted through lipophilicity (QP log P = 2.76 and 2.74 for ABPO-Br and ABPO-Cl, respectively) and serum binding (QP log Khsa = −0.18 and −0.25 for ABPO-Br and ABPO-Cl, respectively). The selectivity and distribution of these TSPO ligands were confirmed by 99mTc-ABPO-Br dynamic image in New Zealand rabbit. These results have shown that the ABPO analogs have the potential to act as better ligands as compared to known acetamidobenzoxazolone derivatives and would be of interest as a promising starting point for designing compounds for TSPO targeting.

Human serum albumin (HSA) is one of the most abundant plasma proteins available in blood and responsible for transport of fatty acids, drugs and metabolites at its two primary binding sites (site 1 and site 2). The interaction of drug molecules with HSA is important and attention-grabbing in the field of science, chemistry and clinical medicine since it affects drug stability and toxicity during therapeutic processes. Hence, the detailed investigation of HSA–drug interactions is required to understand the pharmacodynamics and pharmacokinetics profile of a drug. A drug molecule with effective pharmacological properties can be designed by studying the HSA binding, which acts as a reservoir for a long duration of action and ultimately affects the ADMET (absorption, distribution, metabolism, excretion and toxicity) properties of the drug molecules. Here in the present work a computational investigation including a binding analysis and interaction study of polyamino-polycarboxylic ligands with HSA was conducted. The in silico analysis has been implemented at HSA drug binding sites, site 1 and site 2, via docking studies, prime-MM-GBSA analysis (molecular mechanics energies with generalized Born and surface area continuum solvation), and multiple linear regression analysis with ADMET descriptors and quantitative estimation of log KHSA for the respective molecules. These descriptors described the relevant pharmacokinetics and pharmacodynamics of these ligands for gadolinium-based MRI agents (GBCA). Finally, a complete picture and correlation tell about the primary aspect for the selection of vehicles for magnetic resonance and lanthanide ion-based optical imaging probes.

The 18 kDa translocator protein (TSPO) is a viable target for imaging of inflammation in brain. In the recent past we have explored a pharmacophore skeleton acetamidobenzoxazolone for positron emission tomography (PET) imaging of TSPO expression in brain. Here we evaluated a new radioligand for visualization of TSPO, namely [11C]N-(2-methoxyoxyphenyl)-N-methyl-2-(5-nitro-2-oxobenzo[d]oxazol-3(2H)-yl)acetamide ([11C]N′-MPB). This PET ligand exhibited high binding affinity towards TSPO (Ki = 4.9 nM) and a suitable lipophilicity (log D) of 2.08 for brain imaging. A biodistribution study on mice showed high accumulation of radioactivity in TSPO-rich organs, such as the lungs, heart, kidneys, and adrenal glands. Metabolite analysis of rat brain homogenate showed 98% intact [11C]N′-MPB at 30 min after injection. To determine the specific binding of the radioligand with TSPO on neuroinflammation of the brain, in vitro autoradiography and PET studies were performed in an ischemic rat model. In vitro autoradiography indicated significantly increased binding on the ipsilateral side compared with that on the contralateral side of ischemic rat brains. This result was supported firmly by the contrast of radioactivity in PET images. Displacement experiments with PK11195 minimized the difference in radioactivity uptake between the two sides. In summary, [11C]N′-MPB is a potential PET imaging radioligand for TSPO and, consequently, for gaining more insight for up-regulation of microglia during neuroinflammation.

Vildagliptin (VDG)is a frontier drug for diabetes mellitus. It is prescribed both in the monotherapy as well as in an amalgamation with other antidiabetic drugs. Drug-serum protein binding is an essential parameter which influences ADME properties of the drug. In current study, binding of VDG with serum protein (bovine serum albumin: BSA) was investigated using multi-spectroscopic techniques. A computational approach was also employed to identify the binding affinity of VDG with BSA at both Sudlow I and II sites. An enzyme activity assay specific for esterase was also investigated to know the post-binding consequences of VDG with BSA. Fluorescence spectra of BSA samples treated with VDG shows static quenching with binding parameters for VDG-BSA complex show single class of equivalent binding stoichiometry(n = 1.331) and binding constant 1.1 x 104M−1 at 298.15 K. The binding constant indicates important role of non-polar interactions in the binding process. Fluorescence resonance energy transfer (FRET) analysis of VDG absorption spectra and emission spectrum of BSA confirmed no significant resonance in energy transfer. Synchronous fluorescence of BSA after binding with VDG show maximum changes in emission intensity at tryptophan (Trp) residues. Post binding with VDG, BSA conformation changes as suggested by circular dichorism (CD) spectra of BSA and this lead to enhanced protein stability as indicated by a thermal melting curve of BSA. Communicated by Ramaswamy H. Sarma

Efforts are underway to improve the diagnosis and treatment for neurological disorders like depression, anxiety, epilepsy, and schizophrenia. The G-protein-coupled receptors (GPCRs) 5-HT

This study aimed at assessing 2-methoxyphenyl piperazine derivative for its binding specificity and suitability in mapping metabotropic glutamate receptor subtype 1, which is implicated in several neuropsychiatric disorders. N-(2-(4-(2-Methoxyphenyl)piperazin-1-yl)ethyl)-N-methylpyridin-2-amine was synthesised and evaluated for brain imaging subsequent to radiolabelling with [11C] radioisotope via methylation process in 98.9% purity and 52 ± 6% yield (decay corrected). The specific activity was in the range of 72–93 GBq/µmol. The haemolysis of blood was 2–5% for initial 4 hr and remained The PET as well as biodistribution studies also showed high activity in the brain with a direct correlation between receptor abundance distribution pattern and tracer activity. The biodistribution analyses revealed initial high brain uptake (4.18 ± 0.48). The highest uptake was found in cerebellum (SUV 4.7 ± 0.2), followed by thalamus (SUV 3.5 ± 0.1), and striatum (SUV 3 ± 0.1). In contrast, pons had negligible tracer activity. The high uptake observed in all the regions with known mGluR1 activity indicates suitability of the ligand for mGluR1 imaging.

Among the various types of biomass, microalgae have a potential to become a significant energy source for the production of third generation biofuel. The hydrothermal liquefaction is the direct biomass-to-liquid conversion route carried out in the hot compressed water with or without the presence of a catalyst. In this study, the process pressure and temperature is reduced, but at a lower temperature, bio-oil yield is not high enough to make hydrothermal liquefaction an economical technique. Thus, Fe-MCM 41 catalyst was used to increase the bio-oil yield at low temperatures (250 ºC). This catalyst increased the total bio-oil yield from 42.7 to 61.28 % in hydrothermal liquefaction of Chlorella pyrenoidosa. The bio-oil yield (%) of oil 1, 2 & 3 were 24.72, 17.08 & 19.48, respectively obtained at 250 ºC by using catalyst. Moreover, use of catalyst also resulted in the decrease in oxygen and nitrogen contents of bio-oil and consequently increases in its heating value.

An elevated translocator protein (18 kDa, TSPO) density is observed during inflammation in the brain and peripheral organs making it a viable target for imaging. Recently, our group has explored a pharmacophore skeleton acetamidobenzoxazolone for positron emission tomography (PET) and single photon emission computed tomography (SPECT) applications to target TSPO. 2-(2-(5-Bromo/chloro benzoxazolone)acetamide)-3-(1H-indol-3-yl)propionate (MBIP-Br/Cl) were synthesized by using tryptophan methyl ester and compared with 2-[5-(4-methoxyphenyl)-2-oxo-1,3-benzoxazol-3(2H)-yl]-N-methyl-N-phenyl acetamide (MBMP) through tracer techniques. Computational docking showed similar results for MBIP-Br/Cl in comparison to MBMP. Their ex vivo and in vivo biodistributions were assessed in TSPO-rich organs as well as their release kinetics 0–120 min post injection. The ex vivo biodistribution showed a 7 fold higher uptake (5.16%ID per g vs. 0.72%ID per g) in the heart and a 2.5 fold higher uptake (12.91%ID per g vs. 4.69%ID per g) in the lungs for 99mTc-MBIP-Cl compared to that of 99mTc-MBIP-Br at 15 min. These findings demonstrated that 99mTc-MBIP-Cl has improved pharmacokinetic properties compared to 99mTc-MBIP-Br for SPECT application and is comparable to [11C]MBMP.

An analog of γ1 laminin (RDIAEIIKDI) decapeptide has been used to augment neuronal survival and regeneration after injuries, during aging and other CNS disorder. As a prime synthetic peptide, KDI, is responsible for the neurite outgrowth of human embryonic neurons. In this study, we have designed, modified a KDI derivative and synthesized by replacing isoleucine (I) with Pro (P) amino acid at C-terminal to enhance its potency towards neurite growth. -Cys-Gly-Cys (-CGC) N

Homodimeric chalcone based 11C-PET radiotracer, 11C-(Chal)2DEA-Me, was synthesized, and binding affinity toward beta amyloid (Aβ) was evaluated. The computational studies revealed multiple binding of the tracer at the recognition sites of Aβ fibrils. The bivalent ligand 11C-(Chal)2DEA-Me displayed higher binding affinity compared to the corresponding monomer, 11C-Chal-Me, and classical Aβ agents. The radiolabeling yield with carbon-11 was 40–55% (decay corrected) with specific activity of 65–90 GBq/μmol. A significant (p 93% intact tracer at 30 min po...

Dihydrofolate reductase (DHFR) is an important enzyme for de novo synthesis of nucleotides in Plasmodium falciparum and it is essential for cell proliferation. DHFR is a well known antimalarial target for drugs like cycloguanil and pyrimethamine which target its inhibition for their pharmacological actions. However, the clinical efficacies of these antimalarial drugs have been compromising due to multiple mutations occurring in DHFR that lead to drug resistance. In this background, we have designed 22 s -triazine compounds using the best five parameters based 3D-QSAR model built by using genetic function approximation. In-silico designed compounds were further filtered to 6 compounds based upon their ADME properties, docking studies and predicted minimum inhibitory concentrations (MIC). Out of 6 compounds, 3 compounds were synthesized in good yield over 95% and characterized using IR, 1HNMR, 13CNMR and mass spectroscopic techniques. Parasitemia inhibition assay was used to evaluate the antimalarial activity of s -triazine compounds against 3D7 strain of P. falciparum. All the three compounds (7, 13 and 18) showed 30 times higher potency than cycloguanil (standard drug). It was observed that compound 18 was the most active while the compound 13 was the least active. On the closer inspection of physicochemical properties and SAR, it was observed that the presence of electron donating groups, number of hydrogen bond formation, lipophilicity of ligands and coulson charge of nitrogen atom present in the triazine ring enhances the DHFR inhibition significantly. This study will contribute to further endeavours of more potent DHFR inhibitors. Electronic supplementary material The online version of this article (10.1186/s13065-017-0362-5) contains supplementary material, which is available to authorized users.

Quantitative changes in expression level of 5HT1A are somewhere related to common neurological disorders such as anxiety, major depression and schizophrenia. We have designed EDTA conjugated SPECT imaging probe for localization of 5HT1A receptor in brain. For designing SPECT probe we have employed the concept of bivalent approach and a homodimeric system with desirable pharmacokinetics of 5HT1A imaging. 99mTc-EDHT was also evaluated for its stability through serum stability assay and glutathione challenge experiment. Biodistribution study showed the highest accumulation of radioactivity in kidney which depicted the renal mode of excretion from the body. However in brain the uptake of 1.21% ID per gram was observed in initial 5 min of drug administration. On blocking the receptor this percent get decreased to 0.97% ID per gram. The regional distribution in brain was also performed which showed the accumulation of drug in cerebellum, cortex and hippocampus part, which are already known for 5HT1A expression. Dynamic study in rabbit is also in support of results derived from biodistribution and blood kinetics experiment. These finding suggest that 99mTc-EDHT holds promising place for further optimization before nuclear medicine applications in different animal species.

With the rising incidences of cancer cases, the quest for new metal based anticancer drugs has led to extensive research in cancer biology. Zinc complexes of amino acid residue side chains are well recognized for hydrolysis of phosphodiester bond in DNA at faster rate. In the presented work, a Zn(II) complex of cyclen substituted with two l-tryptophan units, Zn(II)-Cyclen-(Trp)2 has been synthesized and evaluated for antiproliferative activity. Zn(II)-Cyclen-(Trp)2 was synthesized in ∼70% yield and its DNA binding potential was evaluated through QM/MM study which suggested good binding (G=-9.426) with B-DNA. The decrease in intensity of the positive and negative bands of CT-DNA at 278nm and 240nm, respectively demonstrated an effective unwinding of the DNA helix with loss of helicity. The complex was identified as an antiproliferative agent against U-87MG cells with 5 fold increase in apoptosis with respect to control (2h post incubation, IC50 25µM). Electrophoresis and comet assay studies exhibited an increase in DNA breakage after treatment with complex while caspase-3/β-actin cleavage established a caspase-3 dependent apoptosis pathway in U-87 MG cells after triggering DNA damage. In vivo tumor specificity of the developed ligand was validated after radiocomplexation with 99mTc (>98% radiochemical yield and specific activity of 2.56GBq/µmol). Avid tumor/muscle ratio of >6 was depicted in biodistribution and SPECT imaging studies in U-87 MG xenograft model nude mice.

Rational design of a new class of MR (magnetic resonance) contrast agent for enhance relaxivity has been described. The click chemistry was employed to incorporate two moieties of 1-(2-methoxyphenyl)piperazine and serinol as a linker to enhance the affinity at the recognition sites. The designed ligand was attached to DO3A to synthesize DO3A-serinol-bis-MPP (SBMPP) in 89 % yield. Gd-DO3A-SBMPP showed enhanced relaxivity r1 of 10.85±0.04 mM−1s−1 as compare to known gadolinium based contrast agents in clinics. The potentiometric titration of gadolinium loaded SBMPP exhibited strong selectivity for Gd3+ over physiological metal ions such as Zn2+ and Cu2+. Thus, the synthesis of bis-conjugate could be observed as novel, instructive and initial proof of concept for the synthesis of MR contrast agent with enhanced relaxivity. The preliminary findings show the good biocompatibility and potential functionalities of MPP analogue to target brain regions through MRI.

Acetamidobenzoxazolone (ABO) has been modified to ABO-AA, 2-(2-(5-bromo/chloro benzoxazolone)acetamide)-3-(1H-indol-3-yl)propionate to improve pharmacokinetics and lipophilicity (log p = 2.04). The final compound was synthesized in better yield and in fewer steps than previously reported MBIP-Br (70% vs. 62%). Computational docking confirmed binding of MBIP-Cl with translocator protein (TSPO) as well as with mutant TSPO (-8.99 for PDB: 4RYQ and -9.30 for PDB: 4UC1, respectively). Ex-vivo biodistribution and scintigraphy showed that 99m Tc-MBIP-Cl is better than 99m Tc-MBIP-Br in terms of uptake in TSPO-rich organs and release kinetics 0-120 min postinjection. At 15 min, uptake was 2.75-fold (12.91%ID/g vs. 4.69%ID/g) in lung and seven-fold (5.16%ID/g vs. 0.72%ID/g) in heart for 99m Tc-MBIP-Cl compared to that of 99m Tc-MBIP-Br which gives warrant to utilize this single photon emission computed tomography agent in higher animals.

An analog of γ1 laminin (RDIAEIIKDI) decapeptide has been used to augment neuronal survival and regeneration after injuries, during aging and other CNS disorder. As a prime synthetic peptide, KDI, is responsible for the neurite outgrowth of human embryonic neurons. In this study, we have designed, modified a KDI derivative and synthesized by replacing isoleucine (I) with Pro (P) amino acid at C-terminal to enhance its potency towards neurite growth. -Cys-Gly-Cys (-CGC) N2S2 motif was also incorporated in the present design for peptide radiolabeling. The modified peptide showed a better binding with the desired 3T1M receptor for neurite growth. The peptide was synthesized using solid phase peptide synthesis and Fmoc-strategy with more than 80% yield. The receptor binding studies of 99mTc-N2S2-KDP in Neuro2A cell lines showed Kd value in 31 nM range and the complex showed appreciable brain uptake in mice. The results on human SH-SY5Y indicate that the unlabeled N2S2-KDP may perhaps be useful for neurite growth in neurodegenerative disorder.

Bifunctional chelate EDTA-bis amide (N,N′-bis (tyramide)ethylenediamine-N,N′-diacetic acid) that has ability to mimic natural amino acids was synthesized and analyzed by various spectroscopic techniques. The physicochemical studies were performed to calculate the various thermodynamic and kinetic parameters for the synthesized poly-amino carboxylate ligand. The two protonation constant (pka's = 3.460 and 6.722) of the prepared ligand and stability constants (log KML's = 15.8, 18.1, 16.2, 18.4, 17.5, 18.9, 13.6 and 12.8) of the complexes formed with Ce3+, Sm3+, Eu3+, Gd3+, Tb3+, Lu3+, Zn2+ and Cu2+ were determined by potentiometric titration using 0.1 M Me4NOH as non-aqueous base. The formation kinetics of [EuEDTA-TA2]+ and [CeEDTA-TA2]+ was studied and the rate constants were found to be 2.95 × 10–5 s−1 and 4.414 × 10–5 s−1respectively including the exchange reaction of [EuEDTA-TA2]+ with Zn2+ and Cu2+ spectrophotometrically. The Eu(III) complex of EDTA(TA)2 gives three emission bands at 480 nm, 540 nm and 610 nm (λmax = 270 nm, excitation) which shows efficacy of the ligand as an optical imaging agent. Molecular docking studies with Human Serum Albumin (HSA: PDB 1E78 ) showed binding pattern with the residues Arg218, Arg222, Lys195 and Lys444 in sub domain II A of site I via hydrogen bond and identifies the ligand-HSA interaction and specific insight for transportation to the target sites. Subsequently, fluorescence spectroscopy was performed at λex = 350 nm binding constant for HSA was 5.847 × 104 M−1 which showed effective quenching effect.

2,2',2″-(11-(2-((4-mercapto-1-methoxy-1-oxobutan-2-yl)amino)-2-oxoethyl)-1,4,8,11-tetraaza cyclotetradecane-1,4,8-triyl)triacetic acid, Met-ac-TE3A and (E)-N-methyl-2-((E)-3-(2-(2-(5-((3aS,4S,6aR)-2-oxohexahydro-1H-thieno[3,4-d]imidazol-4-yl)pentanoyl)hydrazinecarbono-thioyl)hydrazonobutan-2-ylidene)hydrazinecarbothioamide, Bis(thiosemicarbazone)- Biotin were synthesized and evaluated for imaging application. The pharmacokinetics of these ligands were determined by tracer methods. In vitro human serum stability of (99m)Tc Met-ac-TE3A/(99m)Tc Bis(thiosemicarbazone)-Biotin after 24h was found to be 96.5% and 97.0% respectively. Blood kinetics of both ligands in normal rabbits showed biphasic clearance pattern. Ex vivo biodistribution study revealed significant initial tumor uptake and high tumor/muscles ratio which is a pre-requisite condition for a ligand to work as SPECT-radiopharmaceutical for tumor imaging.

The translator protein (TSPO, 18 kDa), a transmembrane mitochondrial protein, has been explored as an important biomarker by researchers because of its involvement in inflammation, immune modulation and cell proliferation. Recently, our group has explored a modified benzoxazolone derivative for diagnostic applications that has overcome few problems of first and second generation TSPO PET ligands. In this study, a new skeleton acetamidobenzoxazolone–indole, a conjugation of two TSPO pharmacophoric moieties benzoxazolone and indole, has been designed, synthesized and evaluated for TSPO targeting for SPECT. The methyl-2-(2-(5-bromo benzoxazolone)acetamido)-3-(1H-indol-3-yl)propanoate (MBIP) ligand was designed on the basis of pharmacophore modeling done on benzoxazolone based TSPO ligands which was then validated computationally for TSPO binding through docking studies (PDB ID: 4RYO, 4RYQ, and 4UC1) which showed a comparable Glide Gscore as compared to known ligands like PK11195, PBR28, and FGIN-127. MBIP was synthesized by amidation reaction of 2-(5-bromo-benzoxazolone)acetic acid with tryptophan methyl ester hydrochloride (yield 62%). The compound was synthesized and characterized using spectroscopic techniques like 1H-NMR, 13C-NMR, and mass spectroscopy. Purification was carried out by column chromatography and analytical HPLC (purity > 97%). The purified compound was labelled with 99mTc (radiochemical yield > 96%). The radiolabelled compound showed >94% stability in solution and >91% stability in serum after 24 h indicating the stable nature of the radio complex. A biodistribution study on BALB/c mice showed uptake of 99mTc-MBIP in TSPO rich organs and appropriate pharmacokinetics of excretion and release for a SPECT agent. Further evaluation of the 99mTc-MBIP may prove it as a potential candidate for TSPO targeting using SPECT.

Magnetic resonance imaging (MRI) is a diagnostic and research technique widely used in clinical research. We describe here a novel and facile synthesis of a bisconjugated triazaspirodecanone moiety using ‘click chemistry’ as a key step in the synthesis of a triazole based macrocyclic MRI contrast agent. A bivalent approach has been applied to conjugate two triazole rings and triazaspirodecanone moieties across a four carbon spaced linker which is finally conjugated to DO3A to yield the desired MRI contrast agent, DO3A-bis(triazole-triazaspirodecanone), in an overall yield of 70%. All the intermediates and the final compounds have been characterized by NMR and mass spectrometry. In vitro experiments include cytotoxicity (MTT assay) and relaxivity studies. The potentiometric titration of a gadolinium loaded complex displayed strong selectivity for Gd3+ over physiological metal ions such as Zn2+ and Cu2+. IC50 values obtained from the MTT assay indicate the suitability of the synthesized conjugate as a safe diagnostic agent. The longitudinal relaxivity of DO3A-bis(triazole-triazaspirodecanone) was found to be 18.6 mM−1 s−1, which shows that the synthesized conjugate is a suitable MRI contrast agent.

Homodimeric chalcone based

Two novel amino acid (methionine and tryptophan) appended 1,4,8,11-tetraazacyclotetradecane triacetate (TE3A) compounds Met-ac-TE3A and Trp-ac-TE3A were synthesized and evaluated for imaging applications. The pharmacokinetics of these compounds was analyzed by 99mTc labeled tracer methods. In vitro human serum stability of 99mTc labeled Met-ac-TE3A/Trp-ac-TE3A was found to be 96.5% and 96.0% after 24 h respectively. Blood kinetics of both the labeled probes on normal rabbits showed biphasic clearance. The tumor (EAT cell line) grafted in balb/c mice were readily identifiable in the gamma images. Biodistribution revealed significant tumor uptake and good contrast in the EAT tumor bearing mice and also showed high tumor/muscles ratio which is a requisite condition to work as SPECT-radiopharmaceutical for tumor imaging. To look its future applicability for therapy using M+2 and M+3 metal ions, we performed thermodynamic stability constants of complexes derived from Met-ac-TE3A and Trp-ac-TE3A with CuII and LnIII metal ions.

Solid tumors contain regions of hypoxia in comparison to normal tissues. The nitroimidazoles have shown great promise for targeting different types of cancers. The present work involves the design, syntheses, and in vitro and in vivo investigations of hypoxia targeted nitroimidazole radioconjugates (2NIHC and 4NIHC). Flow cytometry analysis showed that the normoxic–hypoxic mean fluorescence of 2NIHC is 10 fold greater than that of 4NIHC and much higher than that of the well-known pimonidazole hypoxia marker. Furthermore, molecular modeling studies of these ligands with CK2α revealed that 2NIHC is a more potential CK2α inhibitor due to π–π interactions and H-bonding with Val116, Glu114, Asp175, Asn161 and His160 in the active pockets of the target. Radio labeling yields for both the complexes with 99mTc were >98%. Biodistribution in EAT tumor bearing mice demonstrated rapid clearance of 99mTc-2NIHC and high T/M ratio (3.57% ID/g) as compared to 99mTc-4NIHC (2.05% ID/g) at 4 h. IC50 values of both ligands were estimated by MTS in different cell lines in addition to tumor regression studies.

A computational approach has been attempted for the screening of 4-pyridoxinium (4P) ring based reactivators for paraoxon inhibited AChE. The oxime molecules were designed with the common 4P skeleton and varying the carbon linkers. Initially, the AChE binding capability was assessed by molecular docking with PDB:2WHP and 3ZLV, which showed important interactions with Ser298, Try124 and Trp286. These computational results were validated by an in vitro AChE binding assay, which showed binding affinities in the range of 10–90%. Finally, reactivation potency was calculated as % reactivation on paraoxon inhibited eelAChE in the concentration range of 10−5 to 10−7 M. It was observed that introduction of an aliphatic linker attached to 4-pyridoxime has a high binding affinity and hence, may act as a good reactivator as compared to the aromatic pyridoximes.

The five transmembrane translocator protein (18 kDa, TSPO) is abundantly expressed in the mitochondria of activated microglia (brain) and peripheral tissues, including those of the heart, lung and kidney. We recently developed the 18F-labelled molecule 2-[5-(4-[18F]fluoropropyloxyphenyl)-2-oxo-1,3-benzoxazol-3(2H)-yl]-N-methyl-N-phenylacetamide ([18F]FPBMP) as a novel positron emission tomography (PET) radioligand for imaging TSPO. In this study, we have evaluated the pharmacokinetics of this radioligand based on its biodistribution in mice, as well as the results of PET and metabolite studies in rats. The specificity of [18F]FPBMP towards TSPO was assessed by blocking experiments involving the intravenous injection of 1 mg kg−1 of unlabeled PK11195. A metabolite study was performed in the plasma and peripheral organs of rats by HPLC methods. The ex vivo biodistribution of [18F]FPBMP in mice showed a high uptake of radioactivity in TSPO enriched peripheral organs, especially in the lung, heart and kidney. The in vivo biodistribution of this compound was evaluated through PET summation images of rats 1–10, 10–20, 20–30 and 50–60 min after the injection of the radioligand. The TSPO-enriched organs, including the heart, kidney and lung, were clearly visualized. Pre-treatment with TSPO-specific PK11195 minimized the uptake of [18F]FPBMP in the TSPO-enriched tissues, thereby confirming its selectivity for TSPO. Metabolite analysis in rats confirmed the presence of [18F]FPBMP in the heart, lung and kidney up to 60 min. In summary, these data demonstrate that [18F]FPBMP is a suitable PET ligand for the imaging of TSPO in peripheral tissues.

RGD and its analogues are very important compounds and can be used as potential tumor-targeting agents. Bisthiosemicarbazone-conjugated RGD (BTSE-RGD) and DOTA-RGD were prepared using a chemical strategy based on peptide synthesis and chemoselective ligations. BTSE-RGD comprises two domains, the first a tumour selective domain and the other a chelating vehicle, for conjugation of radioisotopes. Both compounds were synthesized and labelled with 99mTc and radiochemically analysed by HPLC. The stability of the radioconjugate in the presence of human serum was checked at 37 °C up to 8 h. Labelling yield of 96.8 ± 0.32% was obtained, which corresponds to a specific activity in the range of 36–89 MBq μmol−1 for BTSE-RGD. The BTSE-RGD conjugate was examined in vitro for its ability to bind with the αvβ3 receptor. The functionalized BTSE-RGD displayed a binding affinity toward αvβ3 integrin (31.9 ± 6.8 nM) many-fold better than DOTA-RGD. 99mTc-BTSE-RGD showed a slower distribution half-life (T1/2α) and elimination half-life (T1/2β) of 65 ± 0.001 min and 21 h 15 min ± 0.001 min, respectively, in comparison to 99mTc-DOTA-RGD, with T1/2α of 18 ± 0.001 min and T1/2β of 9 h 10 min ± 0.005 min. Biodistribution study showed better tumor-to-muscle ratio for BTSE-RGD, which reaches maximum around 3.5 (% ID) in 2 h, while for DOTA-RGD the maximum was 13.60 at 24 h.

The 5-HT7 receptor is a recently cloned G-protein-coupled receptor (GPCR) that is important in regulating sleep, depression, and circadian rhythms. However, the potential pathophysiological roles of 5-HT7 have not been fully elucidated, and no 5-HT7 positron emission tomography (PET) radioligands are available, thus limiting imaging studies of this receptor in humans. Here, we present the radiosynthesis and biological evaluation of 5-(4-([11C]methoxyphenyl)-1-methyl-4-nitro-1H-imidazole ([11C]1) as a new PET ligand for 5-HT7. Three-dimensional pharmacophore evaluation and docking studies confirmed its high affinity for 5-HT7, and in vitro binding assays showed that the binding affinity was 16.8 ± 0.9 nM. The specific activity was found to be 48 ± 29 GBq μmol−1 for [11C]1 in a synthetic time of 26 ± 3 min (n = 8), having 38 ± 7% radiochemical yield (decay-corrected) based on [11C]CO2. Ligand interactions with human serum albumin were studied by fluorescence quenching to obtain a Stern–Volmer plot, which showed a binding constant of 1.15 × 104 M−1. Whole-body biodistribution patterns were evaluated in normal mice by 1 h dynamic PET imaging; this analysis showed rapid clearance of radioactivity from the main peripheral organs, with the exception of the liver. Preliminary PET studies in rat brains showed rapid accumulation of radioactivity in the brain. The regional radioactivity reached a maximum within 0–2 min after the radioligand injection and then decreased rapidly, resulting in minimal radiation burden in the brain during the scan. In summary, this specific biaryl system has shown potential as a 5-HT7 ligand and further optimization and longitudinal studies may yield the first small molecule-based PET ligand for 5-HT7 in clinical settings.

We evaluated the efficacy of 2-[5-(4-[(18)F]fluoroethoxy-2-oxo-1,3-benzoxazol-3(2H)-yl)-N-methyl-N-phenylacetamide] ([(18)F]FEBMP) for positron emission tomography (PET) imaging of translocator protein (18 kDa, TSPO). Dissection was used to determine the distribution of [(18)F]FEBMP in mice, while small-animal PET and metabolite analysis were used for a rat model of focal cerebral ischemia. [(18)F]FEBMP showed high radioactivity uptake in mouse peripheral organs enriched with TSPO, and relatively high initial brain uptake (2.67 ± 0.12% ID/g). PET imaging revealed an increased accumulation of radioactivity in the infarcted striatum, with a maximum ratio of 3.20 ± 0.12, compared to non-injured striatum. Displacement with specific TSPO ligands lowered the accumulation levels in infarcts to those on the contralateral side. This suggests that the increased accumulation reflected TPSO-specific binding of [(18)F]FEBMP in vivo. Using a simplified reference tissue model, the binding potential on the infarcted area was 2.72 ± 0.27. Metabolite analysis in brain tissues showed that 83.2 ± 7.4% and 76.4 ± 2.1% of radioactivity was from intact [(18)F]FEBMP at 30 and 60 min, respectively, and that this ratio was higher than in plasma (8.6 ± 1.9% and 3.9 ± 1.1%, respectively). In vitro autoradiography on postmortem human brains showed that TSPO rs6971 polymorphism did not affect binding sites for [(18)F]FEBMP. These findings suggest that [(18)F]FEBMP is a promising new tool for visualization of neuroinflammation.

A novel Trp-Arg rich antimicrobial peptide was designed and the synthesized nonapeptide (hexapeptide analogue AMP) was screened for its antimicrobial and hemolytic activity. In silico studies were performed against a microbial target protein to validate the findings. In vivo studies were carried out for preclinical evaluation of the designed peptide sequence using 99mTc as the radioisotope. The results obtained from the in vitro studies revealed excellent antibacterial activity against E. coli with low hemolytic activity. The in silico studies with the crystal structure of E. coli Pencillin Binding Protein 1b (PBP1b) glycosyltransferase (PDB ID: 3VMA) show higher electrostatic and hydrophobic interactions than the co-crystallized ligand. The radio labeling yield of the 99mTc-labeled AMP was found to be >98%. The blood-kinetics in rabbits and the biodistribution studies in mice confirmed rapid renal excretion from systemic circulation. The scintigraphic analysis for the infection and inflammation animal models revealed that the radiolabel was able to discriminate between infection and inflammation in both mice and rats. Furthermore, blocking experiments in scintigraphy were also carried out using cold peptide to confirm the specificity towards the E. coli infection. Based on the above findings, we consider the designed AMP as a novel antimicrobial agent with the ability to image bacterial infection in vivo by using a gamma emitting radioisotope.

Polymer-based nanoparticles have proven to be viable carriers of therapeutic agents. In this study, we have developed nanoparticles (NPs) from polypeptide-polyethylene glycol based triblock and diblock copolymers. The synthesized block copolymers poly(ethylene glycol)-b-poly(glutamic acid)-b-poly(ethylene glycol) (GEG) and poly(ethylene glycol)-b-poly(glutamic acid) (EG) conjugated with folic acid for targeting specificity (EGFA) have been used to encapsulate methotrexate (MTX) to form M-GEG and M-EGFA NPs aimed at passive and active targeting of cervical carcinoma. In-vitro SRB cytotoxicity and hemolysis assays revealed that these NPs were cytocompatible to healthy human cells and hemocompatible to human RBCs. Cellular uptake by FACS demonstrated their prompt internalization by human cervical carcinoma (HeLa) cells and points toward an apoptotic mechanism of cell kill as confirmed by AO/EB staining as well as histological analysis of explanted HeLa tumors. Pharmacokinetics and biodistribution studies were performed in New Zealand albino rabbits and HeLa xenografted Athymic mice models, respectively, by radiolabeling these NPs with

Calcium concentration modulation both inside and outside cell is of considerable interest for nervous system function in normal and pathological conditions. MRI has potential for very high spatial resolution at molecular/cellular level. Design, synthesis and evaluation of Gd-DO3A-AME-NPHE, a calcium responsive MRI contrast agent is presented. The probe is comprised of a Gd(3+)-DO3A core coupled to iminoacetate coordinating groups for calcium induced relaxivity switching. In the absence of Ca(2+) ions, inner sphere water binding to the Gd-DO3A-AME-NPHE is restricted with longitudinal relaxivity, r1 = 4.37 mM(-1) s(-1) at 4.7 T. However, addition of Ca(2+) triggers a marked enhancement in r1 = 6.99 mM(-1) s(-1) at 4.7 T (60% increase). The construct is highly selective for Ca(2+) over competitive metal ions at extracellular concentration. The r1 is modulated by changes in the hydration number (0.2 to 1.05), which was confirmed by luminescence emission lifetimes of the analogous Eu(3+) complex. T1 phantom images establish the capability of complex of visualizing changes in [Ca(2+)] by MRI.

The mammalian tetrahydrobiopterin (BH4)-dependent phenylalanine hydroxylases (PAH), involved in important metabolic pathways of phenylalanine, belong to non-heme iron-containing aromatic acid hydroxylases' enzyme (AAH) family. AAHs utilize BH4 as protein co-factor and thus promote hydroxylation reactions of their substrates. Any alterations in BH4 -mediated AAH's pathway or mutations in these enzymes are responsible for various disorders, and thus highlights the importance of mutational analysis to assess the effect on their biosynthetic pathways. Our present studies are aimed at single-site mutations in PAH that lead to thermodynamic stability change upon folding and further validation of designed non-reduced BH2 designed co-factors. We have presented single-site mutational analysis of PAH where single-site mutations have been identified from known literature. Further, in silico studies with the PAH, in silico mutant PAH, and crystallized known mutant A313T forms, involved QM/MM and Molecular Dynamics (MD) simulations analysis. The modified co-factor A showed high affinity with PAH and all mutant PAH with high G-score of -14.851. The best pose high affinity co-factor A subjected to QM/MM optimization which leads to square-pyramidal coordination of non-heme active site. The structural and energetic information obtained from the production phase of 20 ns MD simulation of co-factor-metalloprotein complex results helped to understand the binding mode and involvement of three molecules throughout the reaction pathways' catalysis of PAH. The free energies of binding (dG) of A were found to be -68.181 kcal/mol and -72.249 for 1DMW and 1TDW for A313T mutant. Binding of Co-factor A do not perturb the coordination environment of iron at the active site which resides in 2-Histdine and 1-Glutamate triad, and may enhance the percentage response towards co-factor-mediated therapy.

We developed the novel positron emission tomography (PET) ligand 2-[5-(4-[11C]methoxyphenyl)-2-oxo-1,3-benzoxazol-3(2H)-yl]-N-methyl-N-phenylacetamide ([11C]MBMP) for translocator protein (18 kDa, TSPO) imaging and evaluated its efficacy in ischemic rat brains. [11C]MBMP was synthesized by reacting desmethyl precursor (1) with [11C]CH3I in radiochemical purity of ≥ 98% and specific activity of 85 ± 30 GBq/μmol (n = 18) at the end of synthesis. Biodistribution study on mice showed high accumulation of radioactivity in the TSPO-rich organs, e.g., the lungs, heart, kidneys, and adrenal glands. The metabolite analysis in mice brain homogenate showed 80.1 ± 2.7% intact [11C]MBMP at 60 min after injection. To determine the specific binding of [11C]MBMP with TSPO in the brain, in vitro autoradiography and PET studies were performed in an ischemic rat model. In vitro autoradiography indicated significantly increased binding on the ipsilateral side compared with that on the contralateral side of ischemic rat brains. This result was supported firmly by the contrast of radioactivity between the ipsilateral and contralateral sides in PET images. Displacement experiments with unlabelled MBMP or PK11195 minimized the difference in uptake between the two sides. In summary, [11C]MBMP is a potential PET imaging agent for TSPO and, consequently, for the up-regulation of microglia during neuroinflammation. We developed 2-[5-(4-[11C]methoxyphenyl)-2-oxo-1,3-benzoxazol-3(2H)-yl]-N-methyl-N-phenylacetamide ([11C]MBMP) as a novel positron emission tomography ligand for imaging of translocator protein (18 kDa, TSPO) in the brain. [11C]MBMP exhibited high in vitro and in vivo specific binding with TSPO in the ischemic rat brain.

Carbamates are well known for AChE as well as MAO inhibition. In this study, atom-based 3D-QSAR model generation, virtual screening, and molecular docking studies were performed for a known series of 31 carbamate derivatives. The best hypothesis yielded four different pharmacophoric features with statistically significant 3D-QSAR model (correlation coefficient of R2 = 0.994 for training set molecules and very good predictive powers with Q2 and Pearson-R were 0.60 and 0.91, respectively). By virtual screening done against Schrodinger database, we identified 11 distinct drug-like molecules binding to both targets AChE and MAO-B efficiently. This generated 3D-QSAR hybrid model for dual enzymes provides basis for new structural scaffold would serve as building blocks in designing drug-like molecules for Alzheimer’s disease.

Catecholamine mimetic EDTA-bis(tyramide) was synthesized and characterized by various spectroscopic techniques (NMR, mass spectroscopy) and λem 310 nm for the excitation at 270 nm. Molecular docking studies were performed with human serum albumin (PDB 1E78), showing binding pattern with amino acid residues Arg218, Arg222, and Lys444, identifies the ligand-human serum albumin interaction for the transportation affinity of the ligand at the specific site of the target. Subsequently, binding study with human serum albumin at λex = 350 nm found to be 5.847 × 10(4) m(-1) shows effective quenching effect. Additionally, to go more insight, acetylcholinesterase binding affinity was investigated, which shows 90% binding affinity for the 10 mm concentration. IC50 value was found 18.60 μm for MAO-B inhibition. Finally, EDTA-bis(tyramide) labeled with (99m) Tc to investigate its in vivo radiopharmaceutical efficiency having 97% binding affinity with 98% radiochemical purity. In vivo studies were carried out for (99m) Tc-EDTA-bis(tyramide) included blood kinetics showed a quick wash out from the circulation via renal route, and biodistribution revealed that maximum %ID/g was found in kidney at 1 h, and its scintigraphy image shows 3.96% brain uptake with respect to whole body.

MRI has emerged as a powerful tool in the identification and study of diseases. We report an attempt to recognize the structural and physicochemical requirements for better contrast properties of MRI contrast agents. In the present study, an attempt has been made to correlate the relaxivity data of different compounds of DO3A [1,4,7,10-tetraazacyclododecane-1,4,7-tris (methylenecarboxylic acid)] series, in terms of quantitative structure activity relationships (QSAR) to understand the chemical-biological interactions. QSAR results have shown that the relaxivity of DO3A based compounds depend largely on their hydrophobicity. The 2D QSAR model for AlogP using MLR method resulted in Eq. $$AlogP = - 22.444 + 0.709917{\text{MR}} - 0.389389{\text{MW}} - 17.629{\text{HBD}} + 2.28677{\text{PSA}}\quad R^{ 2} = 0. 9 1, \, Q^{ 2} = 0. 8 6, \, s = 0. 1 8, \, F = 9 8. 10 2.$$

A newly synthesized anthraquinone derivative 'N-(2-methylanthraquinone)-4-(2-aminoethyl) phenol' (Tyan) were characterized as a fluorophore from photophysical analysis by measuring the UV-Vis absorptive (λ(ex) = 325 nm) and fluorescence emitive (λ(em) = 660 nm) values. Density functional theory additionally supported the spectroscopic data by modulation of highest occupied molecular orbital rather than lowest unoccupied molecular orbital due to the affect of tyramine moiety present in Tyan. The pharmacological importance of Tyan was evaluated by molecular docking with human serum albumin. The molecular docking of the Tyan was performed with the crystal structure of human serum albumin (PDB entry 1E78), which shows binding in all the three domains of human serum albumin corresponding to -7.74 as the GScore. Moreover, the interactions of human serum albumin with Tyan were assessed employing fluorescence spectroscopy under simulative physiological conditions, and the binding constant for the interaction at 25 °C was found to be 0.6 × 10(3)/M.

We have synthesized six new congeners of acetamidobenzoxazolone for Translocator Protein [18 kDa, TSPO] imaging. The best in vitro binding affinity (10.8 ± 1.2 nm) for TSPO was found for N-methyl-2-(5-(naphthalen-1-yl)-2-oxobenzo[d]oxazol-3(2H)-yl)-N-phenylacetamide, (NBMP). NBMP was synthesised by Suzuki coupling reaction between 2-(5-bromo-2-oxo-1,3-benzoxazol-3(2H)-yl)-N-phenylacetamide and napthalene-1-boronic acid. Computational docking and simulation studies showed not much impact of intersubject variability on binding which is one of the major drawbacks of several TSPO ligands. These findings suggested that NBMP may become a promising marker for visualization of neuroinflammation via TSPO targeting.

Malaria, a life-threatening blood disease, has been a major concern in the field of healthcare. One of the severe forms of malaria is caused by the parasite Plasmodium falciparum which is initiated through protein interactions of pathogen with the host proteins. It is essential to analyse the protein-protein interactions among the host and pathogen for better understanding of the process and characterizing specific molecular mechanisms involved in pathogen persistence and survival. In this study, a complete protein-protein interaction network of human host and Plasmodium falciparum has been generated by integration of the experimental data and computationally predicting interactions using the interolog method. The interacting proteins were filtered according to their biological significance and functional roles. α-tubulin was identified as a potential protein target and inhibitors were designed against it by modification of amiprophos methyl. Docking and binding affinity analysis showed two modified inhibitors exhibiting better docking scores of −10.5 kcal/mol and −10.43 kcal/mol and an improved binding affinity of −83.80 kJ/mol and −98.16 kJ/mol with the target. These inhibitors can further be tested and validated in vivo for their properties as an antimalarial drug.