Ion Exchange Nanoparticles for Ophthalmic Drug Delivery.

We report here on ion-exchange polymeric nanoparticles from a linear copolymer of maleic anhydride methyl vinyl ether esterified with 30% octadecanol. The side chains for the polymer structure were optimized through metadynamics simulations, which revealed the use of octadecanol esters generates ideal free energy surfaces for drug encapsulation and release. Nanoparticles were synthesized using a solvent evaporation-precipitation method by mixing the polymer solution in acetone into water; upon acetone evaporation, a nanodispersion with an average particle size of ∼150 nm was obtained. Gentamicin sulfate, possessing five amino groups, was spontaneously entrapped in the nanocarrier by ionic interactions. Encapsulation efficiency increases significantly with the increase in pH and ionic strength. In vivo results demonstrate high gentamicin (GM) content in the enteric chamber (AUC 8207 ± 1334 (µg min)/mL) compared to 3% GM solution (AUC 2024 ± 438 (µg min)/mL). The formulation was also able to significantly extend the release of gentamicin when applied to rabbit cornea. These anionic nanoparticles can be used for extended-release of other cationic drugs.

Biodegradable Poly(Acetonide Gluconic Acid) for Controlled Drug Delivery.

We report here on the synthesis, characterization, degradation, and drug release of acetal-protected gluconic acid-based poly(α-hydroxy ester). This polyester was synthesized by ring-opening polymerization of O-carboxyanhydride of acetal-protected gluconic acid. The polymer undergoes hydrolytic degradation under mild acidic media, whereas minimal degradation takes place under physiological pH. Under acidic conditions, the acetal-protecting groups are hydrolyzed, resulting in a water-soluble polyester with saccharide side chains that erodes from the surface, leaving the bulk of the polymer matrix intact. At pH 3.5, zero-order kinetics was maintained for 50 days accounting for ∼75% drug release. These biodegradable, pH-responsive, sustained zero-order release kinetics of the polymer have application as drug carriers for oral drug delivery or medical implants or also for nonmedical applications.

Tyrosine Residue in the TRPV1 Vanilloid Binding Pocket Regulates Deactivation Kinetics.

Vanilloids are pain evoking molecules that serve as ligands of the "heat and capsaicin receptor" TRPV1. Binding of either endogenous or exogenous vanilloids evokes channel and subsequent neuronal activation, leading to pain sensation. Despite its pivotal physiological role, the molecular basis of TRPV1 activation and deactivation is not fully understood. The highly conserved tyrosine in position 511 (Tyr(511)) of the rat TRPV1 (rTRPV1) was the first residue to be identified as a necessary participant in the vanilloid-mediated response. rTRPV1 cryo-EM structures implicated rotation of this residue in the vanilloids bound state. Therefore, we hypothesize that the rTRPV1 Tyr(511) residue entraps vanilloids in their binding site, prolonging channel activity. To test our hypothesis, we generated an array of rTRPV1 mutants, containing the whole spectrum of Tyr(511) substitutions, and tested their response to both exo- and endovanilloids. Our data show that only substitutions of Tyr(511) to aromatic amino acids were able to mimic, albeit partially, the vanilloid-evoked activation pattern of the wt receptor. Although these substitutions reduced the channel sensitivity to vanilloids, a maximal open-channel lifetime could be achieved. Moreover, whereas their current activation rate remains intact, receptors with Tyr(511) substitutions exhibited a faster current deactivation. Our findings therefore suggest that the duration of channel activity evoked by vanilloids is regulated by the interaction between Tyr(511) and the agonist. To conclude, we suggest that Tyr(511)-mediated anchoring of vanilloids in their binding pocket is pivotal for TRPV1 activation and subsequent pain sensation.

Alternating Poly(ester-anhydride) by Insertion Polycondensation.

We report on a synthetic method where polyanhydride is used as starting material and the ester monomers are inserted through complete esterification, leading to an alternating ester-anhydride copolymer. The molar ratio of ricinoleic acid (RA) and sebacic acid (SA) was optimized until polysebacic acid is completely converted to carboxylic acid-terminated RA-SA and RA-SA-RA ester-dicarboxylic acids. These dimers and trimers were activated with acetic anhydride, polymerized under heat and vacuum to yield alternating RA-SA copolymer. The resulting alternating poly(ester-anhydride) have the RA at regular intervals. The regular occurrences of RA side chains prevent anhydride interchange, enhancing hydrolytic stability, which allows storage of the polymer at room temperature.

Discovering Novel and Diverse Iron-Chelators in Silico.

Specific iron chelation is a validated strategy in anticancer drug discovery. However, only a few chemical classes (4-5 categories) have been reported to date. We discovered in silico five new structurally diverse iron-chelators by screening through models based on previously known chelators. To encompass a larger chemical space and propose newer scaffolds, we used our iterative stochastic elimination (ISE) algorithm for model building and subsequent virtual screening (VS). The ISE models were developed by training a data set of 130 reported iron-chelators. The developed models are statistically significant with area under the receiver operating curve greater than 0.9. The models were used to screen the Enamine chemical database of ∼1.8 million molecules. The top ranked 650 molecules were reduced to 50 diverse structures, and a few others were eliminated due to the presence of reactive groups. Finally, 34 molecules were purchased and tested in vitro. Five compounds were identified with significant iron-chelation activity in Cal-G assay. Intracellular iron-chelation study revealed one compound as equivalent in potency to the iron chelating "gold standards" deferoxamine and deferiprone. The amount of discovered positives (5 out of 34) is expected by the realistic enrichment factor of the model.

Computational Discovery and Experimental Confirmation of TLR9 Receptor Antagonist Leads.

Toll-like receptors (TLR) are receptors of innate immunity that recognize pathogen associated molecular patterns. They play a critical role in many pathological states, in acute and chronic inflammatory processes. TLR9 is a promising target for drug discovery, since it has been implicated in several pathologies, including defense against viral infections and psoriasis. Immune-modulators are promising molecules for therapeutic intervention in these indications. TLR9 is located in the endosome and activated by dsDNA with CpG motives encountered in microbial DNA. Here we report on a combined approach to discover new TLR9 antagonists by computational chemistry and cell based assays. We used our in-house iterative stochastic elimination (ISE) algorithm to create models that distinguish between TLR9 antagonists ("actives") and other molecules ("inactives"), based on molecular physicochemical properties. Subsequent screening and scoring of a data set of 1.8 million commercially available molecules led to the purchasing of top scored molecules, which were tested in a new cell based system based on human pattern recognition receptors (PRRs) stably expressed in NIH3T3 fibroblasts. As described previously, this cell line shows a very low endogenous PRR-activity and contains a reporter gene which is selectively activated by the integrated human PRR enabling rapid screening of potential ligands. IC50 values of each of these top scored molecules were determined. Out of 60 molecules tested, 56 showed antagonistic activity. We discovered 21 new highly potential antagonists with IC50 values lower than 10 µM, with 5 of them having IC50 values under 1 µM.

PEG-Biscyanoacrylate Crosslinker for Octyl Cyanoacrylate Bioadhesive.

PEG400 (polyethylene glycol, MW 400) biscyanoacrylate is synthesized and copolymerized with 2-octyl cyanoacrylate for potential use as bioadhesive. PEG400 biscyanoacrylate is synthesized from the esterification of anthracenyl cyanoacrylic acid where the anthracene unit serves as vinyl-protecting group. Copolymerization increases the plasticity, mechanical strength, and resilience of the resulted polymer as determined by dynamic mechanical analysis. Peeling test confirms its superior bioadhesive properties. Surface morphology is characterized by SEM imaging. The formulations are cytocompatible and safe. This cyanoacrylate composition may provide improved bioadhesive cyanoacrylates.

Polysaccharide-Based Conjugates for Biomedical Applications.

Polysaccharides contain different functional groups (such as hydroxyl, amino, carboxylic acid, aldehydes) that make them ideal for conjugation. They are biodegradable, biocompatible, and hydrophilic. Polysaccharide conjugates have been used in drug, gene, and macromolecule delivery, tissue engineering, and other biomedical applications. Polysaccharide conjugates have also been used primarily for solubilization and controlled release of hydrophobic moieties. The advent of nanotechnology, gene therapy, and tissue engineering influenced the way these conjugates are now used. Modern day conjugates are modulated to be thermoresponsive, pH-responsive, photoresponsive, or target-specific (receptor mediated targeting). This Review briefly introduces different polysaccharides followed by different synthetic strategies used for conjugation; finally, recent applications were compiled.

Castor Oil-Based Biodegradable Polyesters.

This Review compiles the synthesis, physical properties, and biomedical applications for the polyesters based on castor oil and ricinoleic acid. Castor oil has been known for its medicinal value since ancient times. It contains ∼90% ricinoleic acid, which enables direct chemical transformation into polyesters without interference of other fatty acids. The presence of ricinoleic acid (hydroxyl containing fatty acid) enables synthesis of various polyester/anhydrides. In addition, castor oil contains a cis-double bond that can be hydrogenated, oxidized, halogenated, and polymerized. Castor oil is obtained pure in large quantities from natural sources; it is safe and biocompatible.

Percutaneous Intratumoral Immunoadjuvant Gel Increases the Abscopal Effect of Cryoablation for Checkpoint Inhibitor Resistant Cancer.

Percutaneous cryoablation is a common clinical therapy for metastatic and primary cancer. There are rare clinical reports of cryoablation inducing regression of distant metastases, known as the "abscopal" effect. Intratumoral immunoadjuvants may be able to augment the abscopal rate of cryoablation, but existing intratumoral therapies suffer from the need for frequent injections and inability to confirm target delivery, leading to poor clinical trial outcomes. To address these shortcomings, an injectable thermoresponsive gel-based controlled release formulation is developed for the FDA-approved Toll-like-receptor 7 (TLR7) agonist imiquimod ("Imigel") that forms a tumor-resident depot upon injection and contains a contrast agent for visualization under computed tomography (CT). The poly-lactic-co-glycolic acid-polyethylene glycol-poly-lactic-co-glycolic acid (PLGA-PEG-PLGA)-based amphiphilic copolymer gel's underlying micellar nature enables high drug concentration and a logarithmic release profile that is additive with the neo-antigen release from cryoablation, requiring only a single injection. Rheological testing demonstrated the thermoresponsive increase in viscosity at body temperature and radio-opacity via microCT. Its ability to significantly augment the abscopal rate of cryoablation is demonstrated in otherwise immunotherapy resistant metastatic tumors in two aggressive colorectal and breast cancer dual tumor models with an all or nothing response, responders generally demonstrating complete regression of bilateral tumors in 90-day survival studies.

Effect of substitution at N″-position of N'-hydroxy-N-amino guanidines on tumor cell growth.

Structural modification of one of our earlier reported lead molecule (ABNM13) has been carried out to study the effect of different substituents at the N″-position of N-hydroxy-N'-amino guanidines (HAGs) on their anticancer activity. Compounds with electron donating substituents were found to be less active. In contrast, those with electron withdrawing groups were found favorable for anticancer activity. The obtained results provide significant SAR information that may be useful for further drug designing with HAGs.

Understanding the molecular interactions of different radical scavengers with ribonucleotide reductase M2 (hRRM2) domain: opening the gates and gaining access.

We employed a combination of molecular docking and dynamics to understand the interaction of three different radical scavengers (SB-HSC21, ABNM13 and trimidox) with ribonucleotide reductase M2 (hRRM2) domain. On the basis of the observed results, we can propose how these ligands interact with the enzyme, and cease the radical transfer step from the di-iron center to TYR176. All the ligands alter the electron density over TYR176, -OH group by forming an extremely stable H-bond with either -NHOH group, or with phenolic hydroxyl group of the ligands. This change in electronic density disrupts the water bridge between TYR176, -OH and the di-iron center, which stops the single electron transfer process from TYR176, -OH to iron. As a consequence the enzyme is inhibited. Another interesting observation that we are reporting is the two stage gate keeping mechanism of the RR active site tunnel. We describe these as the outer Gate-1 controlled by ARG330, and the inner Gate-2 controlled by SER263, PHE240, and PHE236. We also observed a dynamic conformational shift in these residues, the incoming ligands can go through, and interact with the underlying TYR176, -OH group. From the study we found the active-site of hRRM2 is extremely flexible and shows a significant induced fit.

N-hydroxy-N'-aminoguanidines as anti-cancer lead molecule: QSAR, synthesis and biological evaluation.

The intrinsic pharmacophore model (r(pred)(2) and r(m)(2) of 0.858 and 0.725) has been developed and used as a query to screen in-house built library based on N-hydroxy-N'-aminoguanidine (HAG) analogs. The pharmacophoric modeled based HITs were synthesized and evaluated for anticancer activity and cytotoxicity. One of the compounds (15) appeared as promising lead candidate with an IC(50) value of 11 µM yielded in HL-60 promyelocytic leukemia cells. Compound 15 reveals significantly lower cytotoxicity against HeLa and Vero cell with CC(50) values of more than 100 µM.

Pyrazoline based MAO inhibitors: synthesis, biological evaluation and SAR studies.

Twenty-two pyrazoline derivatives were synthesized and tested for their human MAO (hMAO) inhibitory activity. Twelve molecules with unsubstituted ring A and substituted ring C (5-16) were found to be potent inhibitors of hMAO-A isoform with SI(MAO-A) in the order 10(3) and 10(4). Ten molecules with unsubstituted ring A and without ring C (21-30), in which eight molecules (21, 23-26, and 28-30) were selective for hMAO-A, one for hMAO-B (22) and the other one non-selective (27). Presence of ring C increases potency as well as SI towards hMAO-A; however its absence decreases both potency and SI towards hMAO-A and hMAO-B.

Chemical scaffolds with structural similarities to siderophores of nonribosomal peptide-polyketide origin as novel antimicrobials against Mycobacterium tuberculosis and Yersinia pestis.

Mycobacterium tuberculosis (Mtb) and Yersinia pestis (Yp) produce siderophores with scaffolds of nonribosomal peptide-polyketide origin. Compounds with structural similarities to these siderophores were synthesized and evaluated as antimicrobials against Mtb and Yp under iron-limiting conditions mimicking the iron scarcity these pathogens encounter in the host and under standard iron-rich conditions. Several new antimicrobials were identified, including some with increased potency in the iron-limiting condition. Our study illustrates the possibility of screening compound libraries in both iron-rich and iron-limiting conditions to identify antimicrobials that may selectively target iron scarcity-adapted bacteria and highlights the usefulness of building combinatorial libraries of compounds having scaffolds with structural similarities to siderophores to feed into antimicrobial screening programs.

Synthesis, antimicrobial and anticancer activity of new thiosemicarbazone derivatives.

Thiosemicarbazones of p-aminobenzoic acid (PABA) were synthesized and tested for their antimicrobial and anticancer activity. Hydroxamate derivatives 4a-4l were found to have better antimicrobial and anticancer activity than their acid counterpart. Compound 4d was found to have good antimicrobial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Vibrio cholerae, and Bacillus subtilis with IC(50) value of about 1 µM. Compound 4f showed potent antifungal activity against Candida albicans (IC(50) = 1.29 µM) and compound 4h showed potent anticancer activity (IC(50) = 0.07 µM).

Engineered insulin-polycation complexes for glucose-responsive delivery with high insulin loading.

Glucose-responsive insulin delivery systems have the potential to improve quality of life for individuals with diabetes by improving blood sugar control and limiting the risk of hypoglycemia. However, systems with desirable insulin release kinetics and high loading capacities have proven difficult to achieve. Here, we report the development of electrostatic complexes (ECs) comprised of insulin, a polycation, and glucose oxidase (GOx). Under normoglycemic physiological conditions, insulin carries a slight negative charge and forms a stable EC with the polycation. In hyperglycemia, the encapsulated glucose-sensing enzyme GOx converts glucose to gluconic acid and lowers the pH of the microenvironment, causing insulin to adopt a positive charge. Thus, the electrostatic interactions are disrupted, and insulin is released. Using a model polycation, we conducted molecular dynamics simulations to model these interactions, synthesized ECs with > 50% insulin loading capacity, and determined in vitro release kinetics. We further showed that a single dose of ECs can provide a glycemic profile in streptozotocin-induced diabetic mice that mimics healthy mice over a 9 h period with 2 glucose tolerance tests.

Towards development of selective and reversible pyrazoline based MAO-inhibitors: Synthesis, biological evaluation and docking studies.

Ten novel 3,5-diaryl pyrazolines were synthesized and investigated for their monoamine oxidase (MAO) inhibitory property. All the molecules were found to be reversible and selective inhibitor for either one of the isoform (MAO-A or MAO-B). Further insights in the theoretical evaluation of the possible interactions between the compounds and monoamine oxidases (MAO-A or MAO-B) have been developed through docking studies. The theoretical values are in congruence with their experimental values.

Design, synthesis and anticancer activity of piperazine hydroxamates and their histone deacetylase (HDAC) inhibitory activity.

Six compounds were synthesized with piperazine in linker region and hydroxamate as Zinc Binding Group (ZBG). They were screened against three cancer cell-lines (NCIH460; HCT116; U251). Compounds 5c and 5f with GI(50) value of 9.33+/-1.3 microM and 12.03+/-4 microM, respectively, were tested for their inhibitory potential on hHDAC8. Compound 5c had IC(50) of 33.67 microM. Compounds were also screened for their anticancer activity against HL60 human promyelocytic leukemia cell line due to the presence of pharmacophoric features of RR inhibitors in them. Compound 5c had IC(50) of 0.6 microM at 48h.