Immobilization of human tyrosine hydroxylase onto magnetic nanoparticles - A novel formulation of a therapeutic enzyme.

Human tyrosine hydroxylase (hTH) has key role in the production of catecholamine neurotransmitters. The structure, function and regulation of hTH has been extensively researched area and the possibility of enzyme replacement therapy (ERT) involving hTH through nanocarriers has been raised as well. However, our understanding on how hTH may interact with nanocarriers is still lacking. In this work, we attempted to investigate the immobilization of hTH on magnetic nanoparticles (MNPs) with various surface linkers in quantitative and mechanistic detail. Our results showed that the activity of hTH was retained after immobilization via secondary and covalent interactions as well. The colloidal stability of hTH could be also enhanced proved by Dynamic light scattering and Zeta potential analysis and a homogenous enzyme layer could be achieved, which was investigated by Raman mapping. The covalent attachment of hTH on MNPs via aldehyde or epoxy linkers provide irreversible immobilization and 38.1 % and 16.5 % recovery (ER). The hTH-MNPs catalyst had 25 % ER in average in simulated nasal electrolyte solution (SNES). This outcome highlights the relevance of immobilization applying MNPs as a potential formulation tool of sensitive therapeutic enzymes offering new opportunities for ERT related to neurodegenerative disorders.

A Comparative Pharmacokinetic Study for Cysteamine-Containing Eye Drops as an Orphan Topical Therapy in Cystinosis.

Cystinosis is a low-prevalence lysosomal storage disease. The pathomechanism involves abnormal functioning of the cystinosine lysosomal cystine transporter (CTNS), causing intraliposomal accumulation of the amino acid cysteine disulfide, which crystallizes and deposits in several parts of the body. The most common ophthalmic complication of cystinosis is the deposition of "gold dust" cystine crystals on the cornea, which already occurs in infancy and leads to severe photosensitivity and dry eyes as it gradually progresses with age. In the specific treatment of cystinosis, preparations containing cysteamine (CYA) are used. The availability of commercialized eyedrops for the targeted treatment is scarce, and only Cystadrops® are commercially available with strong limitations. Thus, magistral CYA-containing compounded eyedrops (CYA-CED) could have a key role in patient care; however, a rationally designed comprehensive study on the commercialized and magistral products is still missing. This work aims to build up a comprehensive study about commercialized and magistral CYA eye drops, involving pharmacokinetic and physicochemical characterization (applying mucoadhesivity, rheology test, investigation of drug release, and parallel artificial membrane permeability assays), as well as ex vivo tests, well supported by statistical analysis.

Lipid-Based Nanocarriers for Delivery of Neuroprotective Kynurenic Acid: Preparation, Characterization, and BBB Transport.

Encapsulation possibilities of an extensively investigated neuroprotective drug (kynurenic acid, KYNA) are studied via lipid-based nanocarriers to increase the blood-brain barrier (BBB) specific permeability. The outcomes of various preparation conditions such as stirring and sonication time, concentration of the lipid carriers and the drug, and the drug-to-lipid ratio are examined. Considering the experimentally determined encapsulation efficiency, hydrodynamic diameter, and ζ-potential values, the initial lipid and drug concentration as well as the stirring and sonication time of the preparation were optimized. The average hydrodynamic diameter of the prepared asolectin-(LIP) and water-soluble lipopolymer (WSLP)-based liposomes was found to be ca. 25 and 60 nm under physiological conditions. The physicochemical characterization of the colloidal carriers proves that the preparation of the drug-loaded liposomes was a successful process, and secondary interactions were indicated between the drug molecule and the polymer residues around the WSLP membrane. Dissolution profiles of the active molecule under physiological conditions were registered, and the release of the unformulated and encapsulated drug is very similar. In addition to this outcome, the in vitro polar brain lipid extract (porcine)-based permeability test proved the achievement of two- or fourfold higher BBB specific penetration and lipid membrane retention for KYNA in the liposomal carriers relative to the unformatted drug.

DIY Virtual Chemical Libraries - Novel Starting Points for Drug Discovery.

The advancement of in silico technologies such as library enumeration and synthetic feasibility prediction has made drug discovery pipelines rely more and more on virtual libraries, which provide a significantly larger pool of compounds than in-stock supplier catalogs. Virtual libraries from external sources, however, may be associated with long delivery time and high cost. In this study, we present a Do-It-Yourself (DIY) combinatorial chemistry library containing over 14 million almost completely novel products built from 1000 low-cost building blocks based on robust reactions frequently applied at medicinal chemistry laboratories. The applicability of the DIY library for various drug discovery approaches is demonstrated by extensive physicochemical property, structural diversity profiling, and the generation of focused libraries. We found that internally built DIY chemical libraries present a viable alternative of external virtual catalogs by providing access to a large number of low-cost and quickly accessible potential chemical starting points for drug discovery.

Medicinal-Chemistry-Driven Approach to 2-Substituted Benzoxazole-Estradiol Chimeras: Synthesis, Anticancer Activity, and Early ADME Profile.

The efficient synthesis of novel estradiol-based A-ring-fused oxazole derivatives, which can be considered as benzoxazole-steroid domain-integrated hybrids containing a common benzene structural motif, is described. The target compounds were prepared from steroidal 2-aminophenol precursors by heterocycle formation or functional group interconversion (FGI) strategies. According to 2D projection-based t-distributed stochastic neighbor embedding (t-SNE), the novel molecules were proved to represent a new chemical space among steroid drugs. They were characterized based on critical physicochemical parameters using in silico and experimental data. The performance of the compounds to inhibit cell proliferation was tested on four human cancer cell lines and non-cancerous cells. Further examinations were performed to reveal IC50 and lipophilic ligand efficiency (LLE) values, cancer cell selectivity, and apoptosis-triggering features. Pharmacological tests and LLE metric revealed that some derivatives, especially the 2-(4-ethylpiperazin-1-yl)oxazole derivative exhibit strong anticancer activity and trigger the apoptosis of cancer cells with relatively low promiscuity risk similarly to the structurally most closely-related and intensively studied anticancer agent, 2-methoxy-estradiol.

Extending the limitations in the prediction of PAMPA permeability with machine learning algorithms.

Gastrointestinal absorption is a key factor amongst the ADME-related (absorption, distribution, metabolism and excretion) pharmacokinetic properties; therefore, it has a major role in drug discovery and drug safety determinations. The Parallel Artificial Membrane Permeability Assay (PAMPA) can be considered as the most popular and well-known screening assay for the measurement of gastrointestinal absorption. Our study provides quantitative structure-property relationship (QSPR) models based on experimental PAMPA permeability data for almost four hundred diverse molecules, which is a great extension of the applicability of the models in the chemical space. Two- and three-dimensional molecular descriptors were applied for the model building in every case. We have compared the performance of a classical partial least squares regression (PLS) model with two major machine learning algorithms: artificial neural networks (ANN) and support vector machine (SVM). Due to the applied gradient pH in the experiments, we have calculated the descriptors for the model building at pH values of 7.4 and 6.5, and compared the effect of pH on the performance of the models. After a complex validation protocol, the best model had an R2=0.91 for the training set, and R2= 0.84 for the external test set. The developed models are capable for the robust and fast prediction of new compounds with an excellent accuracy compared to the previous QSPR models.

Combined Nanofibrous Face Mask: Co-Formulation of Lipases and Antibiotic Agent by Electrospinning Technique.

The application of enzyme-based therapies has received significant attention in modern drug development. Lipases are one of the most versatile enzymes that can be used as therapeutic agents in basic skin care and medical treatment related to excessive sebum production, acne, and inflammation. The traditional formulations available for skin treatment, such as creams, ointments or gels, are widely applied; however, their use is not always accompanied by good drug penetration properties, stability, or patient adherence. Nanoformulated drugs offer the possibility of combining enzymatic and small molecule formulations, making them a new and exciting alternative in this field. In this study polymeric nanofibrous matrices made of polyvinylpyrrolidone and polylactic acid were developed, entrapping lipases from Candida rugosa and Rizomucor miehei and antibiotic compound nadifloxacin. The effect of the type of polymers and lipases were investigated, and the nanofiber formation process was optimized to provide a promising alternative in topical treatment. Our experiments have shown that entrapment by electrospinning induced two orders of magnitude increase in the specific enzyme activity of lipases. Permeability investigations indicated that all lipase-loaded nanofibrous masks were capable of delivering nadifloxacin to the human epidermis, confirming the viability of electrospinning as a formulation method for topical skin medications.

Effect of liposomal formulation of ascorbic acid on corneal permeability.

Ascorbic acid (AA) has a pivotal role in corneal wound healing via stimulating the biosynthesis of highly organized extracellular matrix components, but its rapid degradation and low corneal permeability limits its therapeutic effects. In this paper, we present the pharmacokinetic properties of a liposomal-based formulation of AA in terms of corneal permeation. Chemical stability, shelf-life, and drug release rate of lyophilized liposome (AA-LLipo) formulation was determined in comparison to free-form of AA solution using high-performance liquid chromatography (HPLC) and rapid equilibrium dialysis. In vitro transcorneal permeability was studied using a parallel artificial membrane permeability assay (PAMPA). Ex vivo permeation was examined on AA-LLipo-treated porcine cornea by determining the AA content on the ocular surface, in the cornea as well as in the aqueous humor using HPLC, and by Raman-mapping visualizing the AA-distribution. Our results showed that the liposomal formulation improved the chemical stability of AA, while drug release was observed with the same kinetic efficiency as from the free-form of AA solution. Both corneal-PAMPA and porcine corneal permeability studies showed that AA-LLipo markedly improved the corneal absorption kinetics of AA, thus, increasing the AA content in the cornea and aqueous humor. AA-LLipo formulation could potentially increase the bioavailability of AA in corneal tissues.

Preparation and Evaluation of 6-Gingerol Derivatives as Novel Antioxidants and Antiplatelet Agents.

Ginger (Zingiber officinale) is widely used as a spice and a traditional medicine. Many bioactivities have been reported for its extracts and the isolated compounds, including cardiovascular protective effects. Different pathways were suggested to contribute to these effects, like the inhibition of platelet aggregation. In this study, we synthesised fourteen 6-gingerol derivatives, including eight new compounds, and studied their antiplatelet, COX-1 inhibitor, and antioxidant activities. In silico docking of selected compounds to h-COX-1 enzyme revealed favourable interactions. The investigated 6-gingerol derivatives were also characterised by in silico and experimental physicochemical and blood-brain barrier-related parameters for lead and preclinical candidate selection. 6-Shogaol (2) was identified as the best overall antiplatelet lead, along with compounds 3 and 11 and the new compound 17, which require formulation to optimize their water solubility. Compound 5 was identified as the most potent antioxidant that is also promising for use in the central nervous system (CNS).

Natural Lipid Extracts as an Artificial Membrane for Drug Permeability Assay: In Vitro and In Silico Characterization.

In vitro non-cellular permeability models such as the parallel artificial membrane permeability assay (PAMPA) are widely applied tools for early-phase drug candidate screening. In addition to the commonly used porcine brain polar lipid extract for modeling the blood-brain barrier's permeability, the total and polar fractions of bovine heart and liver lipid extracts were investigated in the PAMPA model by measuring the permeability of 32 diverse drugs. The zeta potential of the lipid extracts and the net charge of their glycerophospholipid components were also determined. Physicochemical parameters of the 32 compounds were calculated using three independent forms of software (Marvin Sketch, RDKit, and ACD/Percepta). The relationship between the lipid-specific permeabilities and the physicochemical descriptors of the compounds was investigated using linear correlation, Spearman correlation, and PCA analysis. While the results showed only subtle differences between total and polar lipids, permeability through liver lipids highly differed from that of the heart or brain lipid-based models. Correlations between the in silico descriptors (e.g., number of amide bonds, heteroatoms, and aromatic heterocycles, accessible surface area, and H-bond acceptor-donor balance) of drug molecules and permeability values were also found, which provides support for understanding tissue-specific permeability.

Cyclodextrin-enabled nepafenac eye drops with improved absorption open a new therapeutic window.

Nepafenac is a highly effective NSAID used for treating postoperative ocular inflammation and pain after cataract surgery and its advantage over conventional topical NSAIDs has been proved many times. However, Nevanac® is a suspension eye drop, which clearly lacks patient compliance causing irritation, blurred vision, foreign body sensation along with problematic dosage due to its sticky, inhomogeneous consistence. In this study, nepafenac containing eye drops were prepared using hydroxypropyl-ß-cyclodextrin to ensure complete dissolution of nepafenac, sodium hyaluronate to provide mucoadhesion and adequate viscosity and a preservative-free officinal formula, Oculogutta Carbomerae containing carbomer (just like Nevanac®), therefore providing a similar base for the new formulations. According to an experimental design, 11 formulations were tested in vitro including two reference formulations by measuring their viscosity, mucoadhesion, drug release and corneal permeability. Finally, two formulations were found promising and investigated further on porcine eyes ex vivo and corneal distribution of nepafenac was determined by RAMAN mapping. The results showed that one formulation possessed better bioavailability ex vivo than Nevanac® 0.1 % suspension, while the other formulation containing only 60 % of the original dose were ex vivo equivalent with Nevanac® opening the way to nepafenac-containing eye drops with better patient compliance in the future.

Stereoselective Synthesis and Antiproliferative Activities of Tetrafunctional Diterpene Steviol Derivatives.

A new family of diterpene-type aminotriol derivatives has been synthesised from stevioside in a stereoselective manner. The key intermediate spiro-epoxide was prepared through the methyl ester of the allilyc diol derived from steviol. The oxirane ring was opened with primary and secondary amines, providing a versatile library of aminotriols. The corresponding primary aminotriol was formed by palladium-catalysed hydrogenation, and an N,O-heterocyclic compound was synthesised in a regioselective reaction. All new compounds were characterised by 1D- and 2D-NMR techniques and HRMS measurements. In our in vitro investigations, we found that the aromatic N-substituted derivatives exhibited high inhibition of cell growth on human cancer cell lines (HeLa, SiHa, A2780, MCF-7 and MDA-MB-231). The antiproliferative activities were assayed by the MTT method. Furthermore, the introduction of an additional hydroxy group slightly increased the biological activity. The drug-likeness of the compounds was assessed by in silico and experimental physicochemical characterisations, completed by kinetic aqueous solubility and in vitro intestinal-specific parallel artificial membrane permeability assay (PAMPA-GI) measurements.

Novel Approach for the Isolation and Immobilization of a Recombinant Transaminase: Applying an Advanced Nanocomposite System.

The increasing application of recombinant enzymes demands not only effective and sustainable fermentation, but also highly efficient downstream processing and further stabilization of the enzymes by immobilization. In this study, a novel approach for the isolation and immobilization of His-tagged transaminase from Chromobacterium violaceum (CvTA) has been developed. A recombinant of CvTA was simultaneously isolated and immobilized by binding on silica nanoparticles (SNPs) with metal affinity linkers and additionally within poly(lactic acid) (PLA) nanofibers. The linker length and the nature of the metal ion significantly affected the enzyme binding efficiency and biocatalytic activity of CvTA-SNPs. The formation of PLA nanofibers by electrospinning enabled rapid embedding of CvTA-SNPs biocatalysts and ensured enhanced stability and activity. The developed advanced immobilization method reduces the time required for enzyme isolation, purification and immobilization by more than fourfold compared to a classical stepwise technique.

Scavengome of an antioxidant.

The term "scavengome" refers to the chemical space of all the metabolites that may be formed from an antioxidant upon scavenging reactive oxygen or nitrogen species (ROS/RNS). This chemical space covers a wide variety of free radical metabolites with drug discovery potential. It is very rich in structures representing an increased chemical complexity as compared to the parent antioxidant: a wide range of unusual heterocyclic structures, new CC bonds, etc. may be formed. Further, in a biological environment, this increased chemical complexity is directly translated from the localized conditions of oxidative stress that determines the amounts and types of ROS/RNS present. Biomimetic oxidative chemistry provides an excellent tool to model chemical reactions between antioxidants and ROS/RNS. In this chapter, we provide an overview on the known metabolites obtained by biomimetic oxidation of a few selected natural antioxidants, i.e., a stilbene (resveratrol), a pair of hydroxycinnamates (caffeic acid and methyl caffeate), and a flavonol (quercetin), and discuss the drug discovery perspectives of the related chemical space.

Effect of Binding Linkers on the Efficiency and Metabolite Profile of Biomimetic Reactions Catalyzed by Immobilized Metalloporphyrin.

The investigation of liver-related metabolic stability of a drug candidate is a widely used key strategy in early-stage drug discovery. Metalloporphyrin-based biomimetic catalysts are good and well-described models of the function of CyP450 in hepatocytes. In this research, the immobilization of an iron porphyrin was performed on nanoporous silica particles via ionic interactions. The effect of the metalloporphyrin binding linkers was investigated on the catalytic efficiency and the metabolic profile of chloroquine as a model drug. The length of the amino-substituted linkers affects the chloroquine conversion as well as the ratio of human major and minor metabolites. While testing the immobilized catalysts in the continuous-flow reactor, results showed that the presented biomimetic system could be a promising alternative for the early-stage investigation of drug metabolites regarding analytical or synthetic goals as well.

Increased blood-brain barrier permeability of neuroprotective drug by colloidal serum albumin carriers.

Encapsulation possibilities of two neuroprotective drugs of slightly different structures, kynurenic acid (KYNA) and its more hydrophilic analogue (SzR72), are studied in bovine serum albumin (BSA) nanoparticles (NPs) to increase their permeability through the blood-brain barrier (BBB). The effect of various preparation conditions such as protein concentration, protein-to-drug ratio, pH, ionic strength, type, and amount of desolvation agent and cross-linker concentration are discussed. It was found that the encapsulation proved to be successful only if the drugs are added to the pre-prepared BSA NPs. If the pH of the medium is adjusted to 4.0 instead of 7.4 the drug loading increased (from 4.5 % to 20.7 % for KYNA) due to the electrostatic interaction between the oppositely charged functional groups accompanied by significant secondary structural changes verified by circular dichroism spectroscopy (CD) suggesting the drug insertion in the hydrophobic pockets of BSA. The in vitro polar brain lipid extract (porcine) based permeability test proved the aimed three-, or fourfold higher BBB specific penetration for KYNA in the carrier relative to the unformatted drug.

Synthesis, Pharmacokinetic Characterization and Antioxidant Capacity of Carotenoid Succinates and Their Melatonin Conjugates.

Carotenoid succinates were synthesized from hydroxy carotenoids and were coupled to a commercially available derivative of melatonin via amide bond for producing more powerful anti-oxidants and yet new hybrid lipophilic bifunctional molecules with additional therapeutic effects. The coupling reactions produced conjugates in acceptable to good yields. Succinylation increased the water solubility of the carotenoids, while the conjugation with melatonin resulted in more lipophilic derivatives. The conjugates showed self-assembly in aqueous medium and yielded relatively stable colloidal solutions in phosphate-buffered saline. Antioxidant behavior was measured with ABTS and the FRAP methods for the carotenoids, the carotenoid succinates, and the conjugates with melatonin. A strong dependence on the quality of the solvent was observed. TEAC values of the new derivatives in phosphate-buffered saline were found to be comparable to or higher than those of parent carotenoids, however, synergism was observed only in FRAP assays.

Synthesis, complex formation and corneal permeation of cyclodextrin-modified, thiolated poly(aspartic acid) as self-gelling formulation of dexamethasone.

The present study aimed at developing a potential in situ gellable dexamethasone (DXM) eye drop. Poly(aspartic acid) (PASP) derivatives were synthesized with dual functionality to improve the solubility of DXM, and to achieve in situ gelation. First, amine-modified ß-cyclodextrin (CD) was attached to polysuccinimide (PSI), second, thiol functionalities were added by the reaction of cysteamine and succinimide rings. Finally, the PSI derivatives were hydrolysed to the corresponding PASP derivatives to get water-soluble polymers. Phase-solubility studies confirmed the complexation ability of CD-containing PASP derivatives. In situ gelation and the effect of the CD immobilization on this behaviour were characterized by rheological measurements. The solubilizing effect of CD was confirmed by kinetic solubility measurements, whereas in vitro corneal permeability assay (corneal-PAMPA) measurements were performed to determine in vitro permeability and flux values. The effect of the PASP derivatives on permeation strongly depended on chemical composition and polymer concentration.

Regioselective synthesis, physicochemical properties and anticancer activity of 2-aminomethylated estrone derivatives.

The unique estrogen receptor (ER)-independent antiproliferative and apoptotic activity of 2-methoxyestradiol (2ME2) is well known, however, its use has been limited because of its poor oral bioavailability. In this study, novel 2-aminomethylated estrone (E) and estradiol (E2) derivatives structurally related to 2ME2 were synthesized, and their physicochemical properties as well as their in vitro cytotoxic effects were investigated in the hope of finding more selective antiproliferative agents with improved pharmacokinetic profile. The target compounds were synthesized from 2-dimethylaminomethylated E obtained regioselectively by a three-component Mannich reaction. Quaternization with methyl iodide followed by reacting the ammonium salt with various dialkyl and alicyclic secondary amines afforded the desired products in good yields. The reactions proceeded via a 1,4-nucleophilic addition of the applied secondary amines to the ortho-quinone methide (o-QM) intermediates, generated in situ from the salt by base-promoted ß-elimination. The compound library has been enlarged with structurally similar E2 analogues obtained by stereoselective reduction and with some 17ß-benzylamino derivatives prepared by reductive amination. The potential values of the novel E and E2 derivatives were characterised by means of three different approaches. At the first step compounds were virtually screened using physicochemical parameters. Physicochemical characterization was completed by kinetic solubility and in vitro intestinal-specific permeability measurement. Antiproliferative effects were additionally determined on a panel of malignant and non-cancerous cell lines. The evaluation of the pharmacological profile of the novel E and E2 derivatives was completed with the calculation of lipophilic efficacy (LiPE).

Analysis of the uncharted, druglike property space by self-organizing maps.

Physicochemical properties are fundamental to predict the pharmacokinetic and pharmacodynamic behavior of drug candidates. Easily calculated descriptors such as molecular weight and logP have been found to correlate with the success rate of clinical trials. These properties have been previously shown to highlight a sweet-spot in the chemical space associated with favorable pharmacokinetics, which is superior against other regions during hit identification and optimization. In this study, we applied self-organizing maps (SOMs) trained on sixteen calculated properties of a subset of known drugs for the analysis of commercially available compound databases, as well as public biological and chemical databases frequently used for drug discovery. Interestingly, several regions of the property space have been identified that are highly overrepresented by commercially available chemical libraries, while we found almost completely unoccupied regions of the maps (commercially neglected chemical space resembling the properties of known drugs). Moreover, these underrepresented portions of the chemical space are compatible with most rigorous property filters applied by the pharma industry in medicinal chemistry optimization programs. Our results suggest that SOMs may be directly utilized in the strategy of library design for drug discovery to sample previously unexplored parts of the chemical space to aim at yet-undruggable targets.