Imidazoquinoline (IMDQ) based small molecule TLR7/8 agonists are the immunostimulating agents with potential to be used as vaccine adjuvants. However, these immune-activating molecules have limitations, including poor solubility and side effects due to systemic exposure. To address these inadequacies, efforts are being made to develop efficient delivery systems. In the present study, two niosome formulations of TLR7/8 agonists BBIQ and m-AMBBIQ were prepared: one using PF-68, Tween 80, and Span 60, and the other using PF-127, Tween 80, and Span 60, which were analyzed by dynamic light scattering. The optimized niosomal formulation comprising PF127, Tween 80, and Span 60 excipients was found to be stable with high drug entrapment efficiencies (>90 %). The shape and size of the niosomes were characterized using dynamic light scattering and high-resolution transmission electron microscopy. The interactions between TLR7/8 agonists and the niosome system was studied using Fourier transform infrared spectroscopy. In vitro release studies and kinetic modeling were performed to examine the drug release behavior from the niosomes. In vitro cytotoxicity and hemolytic studies confirmed that the prepared pluronic-based niosomes are safe, efficient, and biocompatible nanocarrier for delivering small molecule TLR7/8 agonists.

TLR-7/8 agonists are a well-known class of vaccine adjuvants, with a leading example now included in Covaxin, a licensed human COVID-19 vaccine. This thereby provides the opportunity to develop newer, more potent adjuvants based on structure-function studies of these classes of compounds. Imidazoquinoline-based TLR7/8 agonists are the most potent, but when used as a vaccine adjuvant side effects can arise due to diffusion from the injection site into a systemic circulation. In this work, we sought to address this issue through structural modifications in the agonists to enhance their adsorption capacity to the classic adjuvant alum. We selected a potent TLR7-selective agonist, BBIQ (EC50 = 0.85 mu M), and synthesized polyphenolic derivatives to assess their TLR7 agonistic activity and adjuvant potential alone or in combination with alum. Most of the phenolic derivatives were more active than BBIQ and, except for 12b, all were TLR7 specific. Although the synthesized compounds were less active than resiquimod, the immunization data on combination with alum, specifically the IgG1, IgG2b and IgG2c responses, were superior in comparison to BBIQ as well as the reference standard resiquimod. Compound 12b was 5-fold more potent (EC50 = 0.15 mu M in TLR7) than BBIQ and induced double the IgG response to SARS-CoV-2 and hepatitis antigens. Similarly, compound 12c (EC50 = 0.31 mu M in TLR7) was about 3-fold more potent than BBIQ and doubled the IgG levels. Even though compound 12d exhibited low TLR7 activity (EC50 = 5.13 mu M in TLR7), it demonstrated superior adjuvant results, which may be attributed to its enhanced alum adsorption capability as compared with BBIQ and resiquimod. Alum-adsorbed polyphenolic TLR7 agonists thereby represent promising combination adjuvants resulting in a balanced Th1/Th2 immune response.

Toll-like receptor (TLR)-7/8 agonists are promising candidates for the development of new-generation vaccine adjuvants. Adsorption of TLR7/8 agonists on aluminum salts (alum) may further enhance vaccine immunogenicity. Evaluation of the adjuvanticity of the most active dual TLR7/8 agonists, 1-(3-(aminomethyl)benzyl)-2-butyl-1H-imidazo[4,5-c]quinolin-4-amine (m-AM-BBIQ, 10) and its para derivative p-AM-BBIQ (11), along with their gallic acid and protocatechuic acid amides in a recombinant-protein-based COVID-19 vaccine platform confirmed the importance of vic-polyphenolic functionality in TLR7/8 agonists for the alum adsorption, thereby resulting in a balanced Th1/Th2 immune response. A novel 7,8-dihydroxy-IMDQ derivative (dh-p-AM-BBIQ, 21) was designed wherein the vic-diphenolic functionality was introduced in the quinoline ring of the imidazo[4,5-c]quinoline scaffold. Compound 21 not only retained the TLR7 agonistic activity (EC50 = 3.72 μM) but also showed high adsorption to alum and induced a potent antibody response to SARS-CoV-2 spike protein and hepatitis B surface antigen immunized mice. The combination adjuvant comprising compound 21 adsorbed to alum represents a promising candidate for further development as a human and veterinary vaccine adjuvant.

Photocatalysts have gained much attention because of the water pollution instigated by the rapid usage of organic dyes for industrial needs. The degradation of these dyes using photocatalysts under natural light is an economical and popular method for water treatment. There is a need to synthesize photocatalytic materials which can generate reactive oxygen species under natural light. Hence, keeping in mind the above point, rose flower-shaped CuS nanostructures have been synthesized first time by solvothermal technique by varying reaction duration. The self-assembled powder of CuS nanostructures is characterized using XRD, FE-SEM, TEM, DLS, EDS, XPS, Raman, FT-IR, and UV–visible spectroscopy. The XRD and TEM analyses confirmed the formation of a polycrystalline hexagonal structure with prominent diffraction peaks. FE-SEM study shows the formation of uniformly self-assembled rose flower-shaped nanostructures of size 2–3 μm composed of densely packed nanoparticles. XPS study shows the presence of Cu(II) and Cu(I) states of copper in the synthesized batch and stoichiometric composition Cu:S is found to be 60:40 at.

Indoleamine-2,3-dioxygenase 1 (IDO1) is an immunomodulatory enzyme known to catalyse the initial and rate limiting step of kynurenine pathway of l-tryptophan metabolism. IDO1 enzyme over expression plays a crucial role in progression of cancer, malaria, multiple sclerosis and other life-threatening diseases. Several efforts over the last two decades have been invested by the researchers for the discovery of different IDO1 inhibitors and the plasticity of the IDO1 enzyme ligand binding pocket provide ample opportunities to develop new heterocyclic scaffolds targeting this enzyme. In the present work, based on the X-ray crystal structure of human IDO1 coordinated with few ligands, we designed and synthesized new fused heterocyclic compounds and evaluated their potential human IDO1 inhibitory activity (compound 30 and 41 showed IC50 values of 23 and 13 µM, respectively). The identified HITs were observed to be non-toxic to HEK293 cells at 100 µM concentration. The observed activity of the synthesized compounds was correlated with the specific interactions of their structures at the enzyme pocket using docking studies. A detailed analysis of docking results of the synthesized analogues as well as selected known IDO1 inhibitors revealed that most of the inhibitors have some reasonable docking scores in at least two crystal structures and have similar orientation as that of co-crystal ligands.

Leishmania poses a substantial threat to the human population all over the globe because of its visceral and cutaneous spread engendered by all 20 species. Unfortunately, the available drugs against leishmania are already hobbled with toxicity, prolonged treatment, and increasing instances of acquirement of resistance. Under these grave circumstances, the development of new drugs has become imperative to keep these harmful microbes at bay. To this end, a Groebke-Blackburn-Bienaymé multicomponent reaction-based library of different imidazo-fused heterocycles has been synthesized and screened against Leishmania amazonensis promastigotes and amastigotes. Among the library compounds, the imidazo-pyrimidine 24 has been found to be the most effective (inhibitory concentration of 50% (IC50) < 10 μM), with selective antileishmanial activity on amastigote forms, a stage of the parasite related to human disease. The compound 24 has exhibited an IC50 value of 6.63 μM, being ∼two times more active than miltefosine, a reference drug. Furthermore, this compound is >10 times more destructive to the intracellular parasites than host cells. The observed in vitro antileishmanial activity along with suitable in silico physicochemical and absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties of compound 24 reinforce the imidazo-pyrimidine scaffold as a new antileishmanial pharmacophore and encourage further murine experimental leishmaniasis studies.

Indoleamine-2,3-dioxygenase 1 (IDO1) is an immunomodulatory enzyme known to catalyse the initial and rate limiting step of kynurenine pathway of L-tryptophan metabolism. IDO1 enzyme overexpression play a crucial role in progression of cancer, malaria, multiple sclerosis and other life threating diseases. Several efforts over the last two decades have been invested by the researchers for the discovery of different IDO1 inhibitors and the plasticity of the IDO1 enzyme ligand binding pocket provide ample opportunities to develop new heterocyclic scaffolds targeting this enzyme. In the present work, based on the X-ray crystal structure of human IDO1 coordinated with few ligands, we designed and synthesized new fused heterocyclic compounds and evaluated their potential human IDO1 inhibitory activity (compound 30 and 41 showed IC50 values of 23 and 13 µM, respectively). The identified HITs were observed to be non-toxic to HEK293 cells at 100 µM concentration. The observed activity of the synthesized compounds was correlated with the specific interactions of their structures at the enzyme pocket using docking studies. A detailed analysis of docking results of the synthesized analogues as well as selected known IDO1 inhibitors revealed that most of the inhibitors have some reasonable docking scores in at least two crystal structures and have similar orientation as that of co-crystal ligands.

Imidazoquinolinone (IMDQ) derivatives are known TLR7/8 agonists and are approved by the FDA for antiviral and skin cancer treatment. Their use as innate immune system activating molecules has been limited by poor pharmacokinetic properties and toxicities associated with systemic administration. In the present study, an IMDQ derivative, 1-(3-(aminomethyl) benzyl)-2-butyl-1H-imidazo[4,5-c] quinolin-4-amine (meta-aminomethyl BBIQ, 4), was encapsulated in biopolymer lignin nanoparticles (LNPs) to develop slow-release delivery system and to enhance its immune activating properties. A co-precipitation method was used to synthesize LNPs of alkali lignin. Characterization studies demonstrated the formation of spherical shaped nanoparticles of similar to 150 nm size. The encapsulation efficiency and loading capacity for meta-aminomethyl BBIQ in LNPs was found to be 99% and 70%, respectively. In-vitro release studies showed 78% release over 24 h at pH 7.4 followed by sustained release. Kinetic modelling studies showed the release profile followed Weibull order kinetics with beta value <= 0.75 corresponding to Fickian diffusion. Moreover, blank as well as meta-aminomethyl BBIQ-loaded LNPs were nonhemolytic and did not show significant cytotoxicity in RAW 264.7 and MDA-MB-23 cells at all tested concentrations. This study confirms the potential to use LNPs as a drug delivery system for immune modulators or vaccine adjuvants.

A one‐pot methodology is developed for the direct conversion of N‐formylamine, 2‐amino pyridine, and aldehyde into 2,3‐substituted imidazo[1,2‐a]pyridine heterocycles using I2‐PPh3‐Et3N reagent system under microwave irradiation. During the reaction, I2‐PPh3‐Et3N converts N‐formylamine into isocyanide, which in the presence of in‐situ generated hydrogen iodide (HI) undergoes Groebke‐Balckburn‐Bienaymé (GBB) multicomponent reaction with aldehyde and 2‐aminopyridine. The in‐situ generated HI eliminates the need for an external catalyst for the GBB reaction. The developed process incorporates the use of readily accessible and cheap reagents and also avoid a separate step for the synthesis of isocyanides having disagreeable odor. Fourteen different GBB based heterocycles have been synthesized to demonstrate the feasibility of the optimized protocol. The preparation of N‐formylamines utilized in the synthesis is also elaborated and the overall process was optimized to be suitable for a typical undergraduate organic laboratory experiment. One of the final products was characterized using FT‐IR, 1H NMR, 13C NMR, DEPT, COSY, HSQC, HRMS, and single‐crystal X‐ray diffraction. Overall, the experiment will be useful in the organic chemistry curriculum to teach about multicomponent reactions, the importance of isocyanides in organic synthesis, formylation of amines, application of microwave irradiation in organic synthesis, and structural elucidation of small organic molecules.