Locating the binding sites of anticancer tamoxifen and its metabolites 4-hydroxytamoxifen and endoxifen on bovine serum albumin

Spectroscopic investigation and structural simulation in human serum albumin with hydroxychloroquine/Silybum marianum and a possible potential COVID-19 drug candidate

In this study, the interaction between human serum albumin (HSA) and the hydroxychloroquine/Silybum marianum (HCQ/SM) mixture was investigated using various techniques. The observed high binding constant (Kb) and Stern-Volmer quenching constant (KSV) indicate a strong binding affinity between the HCQ/SM mixture and HSA. The circular dichroism (CD) analysis revealed that HCQ/SM induced conformational changes in the secondary structure of HSA, leading to a decrease in the α-helical content. UV-Vis analysis exhibited a slight redshift, indicating that the HCQ/SM mixture could adapt to the flexible structure of HSA. The experimental results demonstrated the significant conformational changes in HSA upon binding with HCQ/SM. Theoretical studies were carried out using molecular dynamics simulation via the Gromacs simulation package to explore insights into the drug interaction with HSA-binding sites. Furthermore, molecular docking studies demonstrated that HCQ/SM-HSA exhibited favorable docking scores with the receptor (5FUZ), suggesting a potential therapeutic relevance in combating COVID-19 with a value of -6.24 kcal mol-1. HCQ/SM exhibited stronger interaction with both SARS-CoV-2 virus main proteases compared to favipiravir. Ultimately, the experimental data and molecular docking analysis presented in this research offer valuable insights into the pharmaceutical and biological properties of HCQ/SM mixtures when interacting with serum albumin.

Enhancing Solid-Phase Extraction of Tamoxifen and Its Metabolites from Human Plasma Using MOF-Integrated Polyacrylonitrile Composites: A Study on CuBTC and ZIF-8 Efficacy

This study investigates electrospun fibers of metal-organic frameworks (MOFs), particularly CuBTC and ZIF-8, in polyacrylonitrile (PAN) for the solid-phase extraction (SPE) of Tamoxifen (TAM) and its metabolites (NDTAM, ENDO, and 4OHT) from human blood plasma. The focus is on the isolation, pre-concentration, and extraction of the analytes, aiming to provide a more accessible and affordable breast cancer patient-monitoring technology. The unique physicochemical properties of MOFs, such as high porosity and surface area, combined with PAN's stability and low density, are leveraged to improve SPE efficiency. The study meticulously examines the interactions of these MOFs with the analytes under various conditions, including elution solvents and protein precipitators. Results reveal that ZIF-8/PAN composites outperform CuBTC/PAN and PAN alone, especially when methanol is used as the protein precipitator. This superior performance is attributed to the physicochemical compatibility between the analytes' properties, like solubility and polarity, and the MOFs' structural features, including pore flexibility, active site availability, surface polarity, and surface area. The findings underscore MOFs' potential in SPE applications and provide valuable insights into the selectivity and sensitivity of different MOFs towards specific analytes, advancing more efficient targeted extraction methods in biomedical analysis.

Membrane-active substituted triazines as antibacterial agents against Staphylococcus aureus with potential for low drug resistance and broad activity

A library of new naphthalimide-triazine analogues was synthesized as broad-spectrum antibacterial agents to overcome drug resistance. Bioactivity assay reveals that derivative 8e, with benzylamine in its structure, exhibits strong antibacterial properties against multi-drug resistance Staphylococcus aureus at a concentration of 1.56 μg/ml. It was also found to be better than chloromycin and amoxicillin. The active compound 8e efficiently inhibits the development of drug resistance within 11 passages. In addition, compound 8e inhibits the formation of biofilms in S. aureus and acts rapidly in bactericidal efficacy. Furthermore, mechanistic studies reveal that compound 8e effectively destroys the cytoplasmic membrane of bacteria, leading to leakage of intercellular protein content and loss in metabolic activity. Compound 8e binds to HSA readily with a binding constant of 1.32 × 10⁵ M^-1, indicating that the compound could be delivered to the target site effectively. Compound 8e can also form a supramolecular complex with DNA to obstruct DNA replications. These results suggest that analogue 8e could be further developed as a potential antibacterial agent. Furthermore, the cytotoxicity of all the synthesized compounds was evaluated against 60 human cancer cell lines to test their potential for anticancer agents.

Antibiotic impregnation and nanocoating of external ventricular drainage catheters for antibacterial applications: Evaluation of in vitro studies and molecular docking

The most suitable method to treat hydrocephalus disease is to insert a shunt catheter that drains the cerebral spinal fluid (CSF); however, shunt implantation is often associated with various bacterial infections. In this study, antibiotic-loaded nanospheres were prepared using the solvent evaporation technique and coated on an antibiotic-impregnated shunt surface to promote shunt antibacterial properties. Clindamycin (CDM) and rifampicin (RIF) were in combination loaded in a single nanosphere, whereas trimethoprim (TMP) was loaded individually in triblock copolymers [(d,l-lactide-random-ε-caprolactone)-block-poly(ethylene glycol)-block-(d,l-lactide-random-ε-caprolactone)] (PLEC). The drug-loading content, encapsulation efficiency, yield, size, and zeta potential of the antibiotic-loaded nanospheres were measured. The results showed that the drug-loading content of clindamycin- and rifampicin-loaded nanospheres (CDM/RIF-NPs) was approximately 3% and 8%, respectively, at a drug to polymer ratio of 1:2. In addition, trimethoprim-loaded nanospheres (TMP-NPs) showed nearly 7% drug loading at equal drug and polymer ratios. The amount of drug release was determined before and after the coating of nanospheres on the shunt surface. In addition, in silico molecular docking studies indicated the good chemical interaction of these antibiotics with PLEC, and the results were consistent with those of impregnation studies. Antibacterial tests of coated external ventricular drainage showed antibacterial activity for up to 21 days.

The Critical Role of 12-Methyl Group of Anthracycline Dutomycin to Its Antiproliferative Activity

Anthracycline dutomycin is a tetracyclic quinone glycoside produced by Streptomyces minoensis NRRL B-5482. SW91 is a C-12 demethylated dutomycin derivative, which was identified in our previous research. In vitro cytotoxicity and apoptosis assays of these two compounds were conducted to demonstrate their antiproliferation activities. The results showed that both dutomycin and SW91 block cells at the S phase, whereas dutomycin shows more significant inhibition of cell growth. Their interactions with calf thymus DNA (CT-DNA) were investigated, with dutomycin exhibiting higher binding affinity. The molecular docking demonstrated that the 12-methyl group makes dutomycin attach to the groove of DNA. These findings suggest that dutomycin has binding higher affinity to DNA and impairs DNA replication resulting in more significant antitumor activity.

Synthesis and photobiological applications of naphthalimide-benzothiazole conjugates: cytotoxicity and topoisomerase IIα inhibition

Conjugates of naphthalimide, benzothiazole, and indole moieties are synthesized that show excellent cytotoxicity against A549 (lung), MCF7 (breast), and HeLa (cervix) cancer cell lines with IC₅₀ values in the range of 0.14–8.59 μM. Compounds 12 and 13 substituted with ethanolamine and propargyl groups reveal potent cytotoxicity towards A549 cancer cells with IC₅₀ values of 140 and 310 nM, respectively. These compounds are further evaluated as potent inhibitors of human type IIα topoisomerase. These conjugates also reveal strong interaction towards human serum albumin (HSA) with binding constant values of 1.75 × 10⁵ M⁻¹ and 1.88 × 10⁵ M⁻¹, respectively, and formation of the stable complex at ground state with static quenching. Docking studies also confirm the effective interactions between conjugates and topoisomerase.

Conjugates of naphthalimide, benzothiazole, and indole moieties are synthesized that show excellent cytotoxicity against A549 (lung), MCF7 (breast), and HeLa (cervix) cancer cell lines with IC₅₀ values in the range of 0.14–8.59 μM.

Assembling cyanidin-3-O-glucoside by using low-viscosity alginate to improve its in vitro bioaccessibility and in vivo bioavailability

In this work, an enteric soluble alginate was proposed to improve the absorption efficiency of cyanidin-3-O-glucoside (C3G) through molecular self-assembly. Under the optimized conditions, the obtained low-viscosity alginate (LVA) was released completely during the simulated gastrointestinal digestion and an LVA-C3G complex with 84.2% binding efficiency was acquired. Fourier transform infrared spectroscopy displayed that the characteristic spectrum of C3G had disappeared after the LVA conjugation. Furthermore, based on the analysis of scanning electron microscopy and differential scanning calorimetry, a porous network structure and the shifted endothermic peak in the thermograms were observed, further confirming the formation of a complex between LVA and C3G. The results of simulated gastrointestinal digestion reveal that the LVA assembly significantly (p < 0.05) improved the bioaccessibility of C3G. Correspondingly, the C3G level in mouse plasma was increased by 27.4% in the C3G-LVA group. This suggests the suitability of LVA as an oral delivery vehicle for dietary anthocyanins.

Unraveling the binding mechanism of an Oxovanadium(IV) - Curcumin complex on albumin, DNA and DNA gyrase by in vitro and in silico studies and evaluation of its hemocompatibility

An oxovanadium(IV) - curcumin based complex, viz. [VO(cur)(2,2´-bipy)(H₂O)] where cur is curcumin and bipy is bipyridine, previously synthesized, has been studied for interaction with albumin and DNA. Fluorescence emission spectroscopy was used to evaluate the interaction of the complex with bovine serum albumin (BSA) and the BSA-binding constant (K_b) was calculated to be 2.56 x 10⁵ M^-1, whereas a single great-affinity binding site was revealed. Moreover, the hemocompatibility test demonstrated that the complex presented low hemolytic fraction (mostly below 1%), in all concentrations tested (0-250 μΜ of complex, 5% DMSO) assuring a safe application in interaction with blood. The binding of the complex to DNA was also investigated using absorption, fluorescence, and viscometry methods indicating a binding through a minor groove mode. From competitive studies with ethidium bromide the apparent binding constant value to DNA was estimated to be 4.82 x 10⁶ M^-1. Stern-Volmer quenching phenomenon gave a Κ_SV constant [1.92 (± 0.05) x 10⁴ M^-1] and k_q constant [8.33 (± 0.2) x 10¹¹ M^-1s^-1]. Molecular docking simulations on the crystal structure of BSA, calf thymus DNA, and DNA gyrase, as well as pharmacophore analysis for BSA target, were also employed to study in silico the ability of [VO(cur)(2,2´-bipy)(H₂O)] to bind to these target bio-macromolecules and explain the observed in vitro activity.

Copper(I) and silver(I) complexes of anthraldehyde thiosemicarbazone: synthesis, structure elucidation, in vitro anti-tuberculosis/cytotoxic activity and interactions with DNA/HSA

A reaction of copper(i) halides (X = I, Br, Cl) and silver(i) halides with 9-anthraldehyde thiosemicarbazone (9-Hanttsc, H1L) and triphenylphosphine produced halogen-bridged dinuclear complexes, [M2(μ2-X)2(η1-S-9-Hanttsc)2(Ph3P)2] (M = Cu, X = Cl, 1; Br, 2; I, 3; M = Ag, X = Cl, 4; Br, 5). A similar reaction of 9-anthraldehyde-N1-methyl thiosemicarbazone (9-Hanttsc-N1-Me, H2L) with Ph3P and silver(i) halides yielded sulfur-bridged dimers, [Ag2X2(μ2-S-9-Hanttsc-N1-Me)2(Ph3P)2] (X = Cl, 9; Br, 10), however with copper(i) halides insoluble compounds were formed, which upon the addition of one extra mole of Ph3P gave mononuclear complexes of the formula [CuX(η1-S-9-Hanttsc-N1-Me)(Ph3P)2] (X = Cl, 6; Br, 7; I, 8). All of the complexes have been characterized by elemental analysis, NMR (1H, 13C) spectroscopy and single crystal X-ray crystallography (2, 5, 6, and 9). Both the ligands (H1L and H2L) and their complexes (1-10) were tested for their anti-tubercular and anticancer activities. The interactions of the ligands and their complexes (copper and silver) with calf thymus DNA (ct-DNA) and human serum albumin (HSA) were examined through UV-visible and fluorescence spectroscopy. Results showed that copper complex 2 displayed strong interactions with ct-DNA and HSA having binding constant values of 6.66 × 104 M-1 and 3.28 × 104 M-1, respectively, followed by silver complex 10 which gave binding constant values of 4.60 × 104 M-1 and 3.06 × 104 M-1, respectively. All of the complexes also showed good interactions with DNA in docking studies.

Spectroscopy and molecular docking approach for investigation on the binding of nocodazole to human serum albumin

The interaction between nocodazole (Nz) and human serum albumin (HSA) under controlled physiological condition (pH 7.4) is examined using absorption, emission, fluorescence lifetime (FLT) and circular dichroism (CD) spectroscopic techniques. The binding constant (order of 10⁵ M^-1) from UV-vis and fluorescence spectroscopy reveals a strong interaction between Nz and HSA. Fluorescence quenching study shows that Nz binds with HSA through static quenching process. It is induced by formation of Nz-HSA complex because the Stern-Volmer quenching constant is inversely correlated with the temperature which is further verified by time-resolved fluorescence spectroscopy. The thermodynamic parameters at different temperatures indicate that the binding process is spontaneous where hydrogen bonding interactions and Van der Waals forces play major roles during the interaction between Nz and HSA. By means of spectroscopy and molecular modeling, we have discovered and interpreted the alteration of the secondary structure of HSA by Nz complexation. Synchronous, three-dimensional fluorescence and CD spectroscopic results reveal that the addition of Nz to HSA affects changes in the micro-environment and conformation of HSA. According to Förster Resonance Energy Transfer (FRET), the binding distance (r) between Nz and residue of HSA is <8 nm with excellent energy efficiency. The docking study suggests that nocodazole binds at Domain IIA in the hydrophobic pocket of human serum albumin.

Investigation of the binding interactions between dimethyl phthalate and its metabolite with bovine serum albumin by multispectroscopy

To understand the behavior of dimethyl phthalate (DMP) and realize the effect of DMP and its metabolite, monomethyl phthalate (MMP), on the conformation changes of bovine serum albumin (BSA), the interaction mechanisms of DMP and MMP with BSA were investigated by multispectroscopy and molecular docking. The results of the fluorescence quenching experiment showed that the fluorescence quenching of BSA by DMP and MMP was due to the formation of a complex though static quenching, which was also confirmed by time-resolved fluorescence measurements. The binding constants were 8.06 × 10⁴ M^-1 and 4.74 × 10⁴ M^-1 for DMP-BSA and MMP-BSA, respectively, and the number of binding sites were 1.20 (DMP) and 1.18 (MMP). The thermodynamic parameters showed different binding forces for DMP and MMP with BSA. The binding of DMP to BSA was driven mainly by hydrophobic interactions and hydrogen bonding, and MMP bound to BSA by van der Waals forces and hydrogen bonding, which were in accordance with the results from the molecular docking. The conformation and structural alterations of BSA upon DMP or MMP binding were studied by UV-vis spectroscopy, circular dichroism spectroscopy and synchronous fluorescence spectroscopy. The presence of metabolite did not change the quenching mechanism but decreased the binding affinity of DMP toward BSA as well as shortened the binding distance, which may be attributed to the competition between DMP and MMP for binding to BSA. This study revealed the combined effects of DMP and its metabolite on BSA at the molecular level.

Novel Tamoxifen Nanoformulations for Improving Breast Cancer Treatment: Old Wine in New Bottles

Breast cancer (BC) is one of the leading causes of death from cancer in women; second only to lung cancer. Tamoxifen (TAM) is a hydrophobic anticancer agent and a selective estrogen modulator (SERM), approved by the FDA for hormone therapy of BC. Despite having striking efficacy in BC therapy, concerns regarding the dose-dependent carcinogenicity of TAM still persist, restricting its therapeutic applications. Nanotechnology has emerged as one of the most important strategies to solve the issue of TAM toxicity, owing to the ability of nano-enabled-formulations to deliver smaller concentrations of TAM to cancer cells, over a longer period of time. Various TAM-containing-nanosystems have been successfully fabricated to selectively deliver TAM to specific molecular targets found on tumour membranes, reducing unwanted toxic effects. This review begins with an outline of breast cancer, the current treatment options and a history of how TAM has been used as a combatant of BC. A detailed discussion of various nanoformulation strategies used to deliver lower doses of TAM selectively to breast tumours will then follow. Finally, a commentary on future perspectives of TAM being employed as a targeting vector, to guide the delivery of other therapeutic and diagnostic agents selectively to breast tumours will be presented.

Evaluation of competitive binding interaction of neratinib and tamoxifen to serum albumin in multidrug therapy

Co-administration of two drugs to obtain a therapeutic goal is a common practice clinically and for effective use of drug therapy. However, the co-administration can sometimes cause adverse effects due to pharmacokinetic drug interactions. Breast Cancer treatment regimen include tyrosine kinase inhibitor neratinib (NRB) and/or tamoxifen (TMX). In this study neratinib and tamoxifen interaction with bovine serum albumin (BSA) and human serum albumin (HSA) individually and in combination using fluorescence spectroscopy was studied. The aim of this study was to find out whether there is a possibility of either of the two drugs interfering in the plasma protein binding of the other drug. Subdomain IIA of both the BSA and HSA was found to bind tamoxifen and neratinib. The λ_ex = 280 nm and 295 nm were used for the analysis of neratinib-SA, tamoxifen-SA, neratinib: SA in presence of constant concentration of tamoxifen and similarly tamoxifen-SA in presence of constant concentration of neratinib. The interaction study of the binary and the ternary systems suggest that neratinib doesn't affect the interaction between SA and tamoxifen. In contrast, the interaction between neratinib and SA was affected by tamoxifen. The binding constant and quenching constant values suggest that tamoxifen dislodges neratinib from its serum albumin complex whereas neratinib doesn't affect the interaction between SA and tamoxifen. Thus, it was concluded from the results the study that during simultaneous administration of neratinib and tamoxifen, their competition for the SA binding sites should be taken into account.

Synthesis of naphthalimide-phenanthro[9,10-d]imidazole derivatives: In vitro evaluation, binding interaction with DNA and topoisomerase inhibition

The synthesis and characterization of a series of naphthalimide and phenanthro[9,10-d]imidazole conjugate is described. These compounds are evaluated in vitro for their cytotoxicity towards 60 human cancer cell lines. Derivative 16 shows excellent cytotoxic activity against these cancer cell lines with the range of growth inhibition from -55.78 to 94.53. The most potent derivative (ethylpiperazine, 16) is further studied to evaluate the interaction with ct-DNA using absorption and emission spectroscopy as well as DNA viscosity measurement. The DNA binding studies indicate that compound 16 is significantly interacted with DNA through groove binding having binding constant value of 7.81 × 10⁴ M^-1 alongwith partial intercalation between the base pairs of DNA strands. Further, topoisomerase inhibition study suggests that compound 16 is induced apoptosis and inhibits human topoisomerase (Topo-IIα) as a possible intracellular target. Molecular docking study of compound 16 with ct-DNA shows good docking score.

Tumor pH-Responsive Albumin/Polyaniline Assemblies for Amplified Photoacoustic Imaging and Augmented Photothermal Therapy

Tumor-microenvironment-responsive theranostics have great potential for precision diagnosis and effective treatment of cancer. Polyaniline (PANI) is the first reported pH-responsive organic photothermal agent and is widely used as a theranostic agent. However, tumor pH-responsive PANI-based theranostic agents are not explored, mainly because the conversion from the emeraldine base (EB) to emeraldine salt (ES) state of PANI requires pH < 4, which is lower than tumor acidic microenvironment. Herein, a tumor pH-responsive PANI-based theranostic agent is designed and prepared for amplified photoacoustic imaging guided augmented photothermal therapy (PTT), through intermolecular acid-base reactions between carboxyl groups of bovine serum albumin (BSA) and imine moieties of PANI. The albumin/PANI assemblies (BSA-PANI) can convert from the EB to ES state at pH < 7, accompanied by the absorbance redshift from visible to near-infrared region. Both in vitro and in vivo results demonstrate that tumor acidic microenvironment can trigger both the photoacoustic imaging (PAI) signal amplification and the PTT efficacy enhancement of BSA-PANI assemblies. This work not only highlights that BSA-PANI assemblies overcome the limitation of low-pH protonation, but also provides a facile assembly strategy for a tumor pH-responsive PANI-based nanoplatform for cancer theranostics.

Effective synthesis of benzimidazoles-imidazo[1,2-a]pyrazine conjugates: A comparative study of mono-and bis-benzimidazoles for antitumor activity

A novel series of 6-substituted-8-(1-cyclohexyl-1H-benzo[d]imidazole-6-yl)imidazo[1,2-a]pyrazine and 6-substituted-8-(1-benzyl-1H-benzo[d]imidazole-6-yl)imidazo[1,2-a]pyrazine is first time synthesized and screen in vitro biological activity for 60 human cancer cell lines representing nine different cancer types. Derivatives 10 and 36 show antitumor activity for all tested cell lines, display comparable full panel mean-graph midpoint growth inhibition (MG_MID GI₅₀) values of 2.10 and 2.23 μM, respectively. Furthermore, these derivatives show strong binding interactions with DNA and bovine serum albumin (BSA), studied through absorption, emission, and circular dichroism techniques. These spectroscopic studies reveal that imidazo[1,2-a]pyrazine-benzimidazoles 10 and 36, intercalate with ct-DNA as a leading interaction for fundamental biologically significant effects, with monobenzimidazole show better activity than bisbenzimidazole. These experiments have confirmed that the imidazo[1,2-a]pyrazine and benzimidazole moieties are efficient pharmacophores to trigger binding to DNA. These compounds have also interacted with bovine serum albumin protein that demonstrating high values of binding constant.

Bovine serum albumin-cobalt(ii) Schiff base complex hybrid: an efficient artificial metalloenzyme for enantioselective sulfoxidation using hydrogen peroxide

An artificial metalloenzyme (BSA-CoL) based on the incorporation of a cobalt(ii) Schiff base complex {CoL, H2L = 2,2'-[(1,2-ethanediyl)bis(nitrilopropylidyne)]bisphenol} with bovine serum albumin (BSA) has been synthesized and characterized. Attention is focused on the catalytic activity of this artificial metalloenzyme for enantioselective oxidation of a variety of sulfides with H2O2. The influences of parameters such as pH, temperature, and the concentration of catalyst and oxidant on thioanisole as a model are investigated. Under optimum conditions, BSA-CoL as a hybrid biocatalyst is efficient for the enantioselective oxidation of a series of sulfides, producing the corresponding sulfoxides with excellent conversion (up to 100%), chemoselectivity (up to 100%) and good enantiomeric purity (up to 87% ee) in certain cases.

Cooperative Assembly of a Peptide Gelator and Silk Fibroin Afford an Injectable Hydrogel for Tissue Engineering

Silk fibroin (SF) from Bombyx mori has received increasing interest in biomedical fields, because of its slow biodegradability, good biocompatibility, and low immunogenicity. Although SF-based hydrogels have been studied intensively as a potential matrix for tissue engineering, weak gelation performance and low mechanical strength are major limitations that hamper their widespread applicability. Therefore, searching for new strategies to improve the SF gelation property is highly desirable in tissue engineering research. Herein, we report a facile approach to induce rapid gelation of SF by a small peptide gelator (e.g., NapFF). Following the simple mixing of SF and NapFF in water, a stable hydrogel of SF was obtained in a short time period at physiological pH, and the minimum gelation concentration of SF can reach as low as 0.1%. In this process of gelation, NapFF not only can behave itself as a gelator for supramolecular self-assembly, but also can trigger the conformational transition of the SF molecule from random coil to β-sheet structure via hydrophobic and hydrogen-bonding interactions. More importantly, for the generation of a scaffold with favorable cell-surface interactions, a new peptide gelator (NapFFRGD) with Arg-Gly-Asp (RGD) domain was applied to functionalize SF hydrogel with improved bioactivity for cell adhesion and growth. Following encapsulating the vascular endothelial growth factor (VEGF), the SF gel was subcutaneously injected in mice, and served as an effective matrix to trigger the generation of new blood capillaries in vivo.

Enhancement of anticancer activity and drug delivery of chitosan-curcumin nanoparticle via molecular docking and simulation analysis

Computational analyses followed by traditional wet-bench experiments have become a method of choice due to successful results. To enhance the solubility and bioavailability of curcumin within chitosan nanoparticle, we have exploited computational methodologies i.e. docking, BBD-RSM and MD simulation for the polymer selection, NPs' formulation, optimization and their stability confirmation in an aqueous medium, respectively. Formulated CSCur NPs were assessed for in-vitro release, which exhibited a sustained release pattern and four-fold higher cytotoxic activity in a nanoparticulated system. Enhanced uptake, apoptotic effect of CSCur NPs were established by morphological changes in cells as observed by fluorescence microscopy and FE-SEM. DNA damage, cell-cycle blockage and elevated ROS levels further confirm the anticancer activity of the CSCur NPs following apoptotic pathways. In-vivo study on Danio rerio, for uptake and toxicity reveal the particle's biocompatibility and nontoxicity. Therefore, CSCur NPs could be the potential formulation for a safe chemotherapeutic drug for cancer.

Tamoxifen metabolite endoxifen interferes with the polyamine pathway in breast cancer

Tamoxifen is the most widely used drug to treat women with estrogen receptor α (ERα)-positive breast cancer. Endoxifen is recognized as the active metabolite of tamoxifen in humans. We studied endoxifen effects on ERα-positive MCF-7 breast cancer cells. Estradiol increased the proliferation of MCF-7 cells by two- to threefold and endoxifen suppressed its effects. Endoxifen suppressed c-myc, c-fos and Tff1 oncogene expression, as revealed by RT-PCR. Estradiol increased the activity of ornithine decarboxylase (ODC) and adenosyl methioninedecarboxylase (AdoMetDC), whereas endoxifen suppressed these enzyme activities. Endoxifen increased activities of spermine oxidase (SMO) and acetyl polyamine oxidase (APAO) significantly, and reduced the levels of putrescine and spermidine. These data suggest a possible mechanism for the antiestrogenic effects of tamoxifen/endoxifen, involving the stimulation of polyamine oxidase enzymes. Therefore, SMO and APAO stimulation might be useful biomarkers for the efficacy of endoxifen treatment of breast cancer.

Unexpected formation of N'-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester from acephate: chemical, biotechnical and computational study

By the nucleophilic attack of phenylhydrazine on acephate in aqueous medium, a stable product N′-phenyl-thiophosphorohydrazidic acid O,S-dimethyl ester (1) was obtained and characterized by elemental, spectral and thermal analysis. Thermodynamic parameters, Ea, ΔH°, ΔS° and ΔG°, have found to be 62.15, −67.95, −0.068 and −20.05 kJ mol⁻¹ according to the Coats–Redfern equation. Analysis of interaction of 1 with BSA protein was done by using the UV–Vis and FTIR spectroscopic methods. The observed binding constants was 1.12 (±0.09) × 10⁴ M⁻¹. The biological effect of 1 was checked on different plant growth-promoting (PGPR) strains such as Rhizobiumleguminosarum, Pseudomonasfluorescens, Arthrobactercitreus, Bacillusbrevis and Salmonellatyphimurium and compared with parent molecule acephate where 1 has shown less toxicity against PGPRs as compared to acephate. The experimental results for geometric parameters and values of peak position in IR spectra have found to match excellently with the computational studies performed by GAMESS software package. Theoretically, twelve new analogs of 1 were prepared and their comparative reactivity (HOMO–LUMO energy) and biodecomposition (on the basis of polarizability) is discussed.

An experimental and quantum chemical study on the non-covalent interactions of a cyclometallated Rh(iii) complex with DNA and BSA

The interaction of a new cyclometallated Rh(iii) complex with DNA and BSA was investigated. The three-layer ONIOM method was employed to calculate the interaction energy between DNA and the complex.

Biological activity of natural flavonoids as impacted by protein flexibility: an example of flavanones

Naturally multifunctional Rutaceae hesperidin and its aglycone hesperetin have a great variety of biopharmaceutical activities, e.g. anti-cancer, anti-inflammatory, antioxidant and antitumor; however, the influence of the molecular structures of hesperidin and hesperetin, and in particular, the structural properties such as flexibility and dynamic features of protein on the biological activities of these bioactive compounds remains ambiguous. In the present study, the biomolecular recognition of crucial biopolymer - albumin from human serum (HSA) with Rutaceae, the recognition differences between HSA-hesperidin and HSA-hesperetin, the key elements that lead to the discrepancies as well as the structural characters of protein to the recognition processes were comparatively examined by employing biophysical approaches at the molecular scale. The results illustrated distinctly that (1) aglycone hesperetin can form stronger noncovalent bonds with HSA and possess higher recognition stability as compared with hesperidin. This phenomenon suggest that the introduction of glycoside structure into flavanone may possibly not be able to increase the noncovalent recognition of flavanone by a biopolymer, and conversely, this event will probably decrease the recognition capacity. (2) Although hesperidin and hesperetin can be located within subdomains IIA and IIIA, respectively, the conformational stability of flavanones in subdomain IIA is greater than subdomain IIIA; as a result, the recognition ability of subdomain IIIA with flavanones is patently lesser than subdomain IIA. These discrepancies likely originate from the unique characteristics of the respective cavity, or more specifically, subdomain IIA is basically a closed space, whereas subdomain IIIA is a semi-open region. Meanwhile, the detailed analyses of root-mean-square fluctuation interpreted the recognition of flavanones by subdomain IIA on HSA, which would evoke larger conformational alterations in several amino acid residues, and the similar phenomenon also resides in subdomain IIIA, which signifies that the flexible characteristics of different binding patches in protein may possess fairly notable effects on the HSA-flavanones recognition. Moreover, the integral structural changes of HSA exhibit some disparities on account of the dissimilarities of recognition capability to the protein-flavanone biointeractions, and all these conclusions received further forceful supports from fluorescence and circular dichroism experiments in solution. Perhaps the work emerged herein could not only help us to better evaluate the bioavailability of natural flavanones with or without glycoside, but to understand the sketches of the three-dimensional structure trait of certain biomacromolecules for the medicinal properties of flavonoids in the human body.

The compatibility of Tacrine molecule with poly(n-butylcyanoacrylate) and Chitosan as efficient carriers for drug delivery: A molecular dynamics study

According to the critical role of drug delivery in the treatment of diseases of the central nervous system (CNS), the selection of a suitable carrier plays an important role in the greater effectiveness of drugs. Due to good biocompatibility, biodegradability and low toxicity of polymeric nanoparticles, especially poly(n-butylcyanoacrylate) (PBCA) and Chitosan, these nanoparticles are considered as efficient carriers in drug delivery to the brain. In order to investigate the compatibility of these two polymers with different degrees of polymerization versus a Tacrine unit as the most well known drug for the treatment of Alzheimer's disease, molecular dynamics simulation (MD) is used as a principal tool for studying molecular systems. Interaction energy of the polymer/Tacrine systems, the radius of gyration of the Chitosan and PBCA during the simulation time, solubility and Flory-Huggins interaction parameters has been calculated. According to the results, the Tacrine molecule exhibited higher compatibility with PBCA than Chitosan. Moreover, the interaction between the Tacrine molecules and PBCA nanoparticles became stronger by increasing the length of polymer chain while it was not observed as a regular trend for Chitosan/Tacrine systems. By using these MD simulations, it is possible to find the most appropriate polymer as an efficient drug carrier. We note that the methodology applied here for modeling the polymer/Tacrine system is not restricted to the specific formulations of Tacrine and Chitosan (or PBCA) in the current work and can be extended to various other traditional or new drugs and different polymer drug carriers.

Molecular structure-affinity relationship of bufadienolides and human serum albumin in vitro and molecular docking analysis

The development of bufadienolides as anti-tumor agents is limited due to poor pharmacokinetic properties regarding drug half-lives and toxicity in vivo. These serious factors might be improved by increasing the drug/albumin-binding ratio. This study therefore investigated the relationship between the structural properties of nine bufadienolides and their affinities for human serum albumin (HSA) by a fluorescence spectroscopy-based analysis and molecular docking. Fluorescence quenching data showed that the interaction of each bufadienolide with HSA formed a non-fluorescent complex, while thermodynamic parameters revealed negative ΔS and ΔH values, corresponding to changes in enthalpy and entropy, respectively. The structural differences between the various bufadienolides markedly influenced their binding affinity for HSA. With the exception of a C = O bond at the C12 position that decreased the binding affinity for HSA, other polar groups tended to increase the affinity, especially a hydroxyl (OH) group at assorted bufadienolide sites. The rank order of binding affinities for drugs with tri-hydroxyl groups was as follows: 11-OH > 5-OH > 16-OH; in addition, 16-acetoxy (OAc), 10-aldehyde and 14-epoxy constituents notably enhanced the binding affinity. Among these groups, 11-OH and 16-acetyl were especially important for a seamless interaction between the bufadienolides and HSA. Furthermore, molecular docking analysis revealed that either an 11-OH or a 16-OAc group spatially close to a five-membered lactone ring significantly facilitated the anchoring of these compounds within site I of the HSA pocket via hydrogen bonding (H-bonding) with Tyr150 or Lys199, respectively. In summary, bufadienolide structure strongly affects binding with HSA, and 11-OH or 16-OAc groups improve the drug association with key amino acid residues. This information is valuable for the prospective development of bufadienolides with improved pharmacological profiles as novel anti-tumor drugs.

A mononuclear diketone-based oxido-vanadium(iv) complex: structure, DNA and BSA binding, molecular docking and anticancer activities against MCF-7, HPG-2, and HT-29 cell lines

A mononuclear oxido-vanadium(iv) complex, [VO(L)₂], has been synthesized and its interactions with DNA and BSA have been investigated experimentally and theoretically.

Synthesis and biological evaluation of 5'-glycyl derivatives of uridine as inhibitors of 1,4-β-galactosyltransferase

New 5'-glycyl derivatives of uridine containing fragments of varying lipophilicity were synthesized as analogues of natural peptidyl antibiotics. One of the studied compounds, 5'-O-(N-succinylglycyl)-2',3'-O-isopropylideneuridine (A4), showed moderate inhibition against 1,4-β-galactosyltransferase. However, additional studies showed that the observed inhibitory effect was due to binding to bovine serum albumin, which was used in assays as a stabilizer.

Molecular modeling and spectroscopic studies on the interaction of the chiral drug venlafaxine hydrochloride with bovine serum albumin

This study was designed to examine the interaction of racemic antidepressant drug "S,R-venlafaxine hydrochloride (VEN)" with bovine serum albumin (BSA) under physiological conditions. The mechanism of interaction was studied by spectroscopic techniques combination with molecular modeling. Stern-Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. The thermodynamic parameters indicated that the hydrogen bonding and weak van der Waals interactions are the predominant intermolecular forces stabilizing the complex. The number of binding sites (n) was calculated. Through the site marker competitive experiment, VEN was confirmed to be located in subdomain IIIA of BSA. The binding distance (r=4.93 nm) between the donor BSA and acceptor VEN was obtained according to Förster's non-radiative energy transfer theory. According to UV-vis spectra and CD data binding of VEN leaded to conformational changes of BSA. Molecular docking simulations of S and R-VEN revealed that both isomers have similar interaction and the same binding sites, from this point of view S and R isomers are equal.

Characterization of the Binding of the Finland Trityl Radical with Bovine Serum Albumin

Understanding the interactions of trityl radicals with proteins is required to expand their biomedical applications. In this work, we demonstrate that the Finland trityl radical CT-03 binds to bovine serum albumin (BSA) in aqueous solution. Upon binding with BSA, CT-03 exhibits a much broader electron paramagnetic resonance (EPR) signal and this line broadening can be reversed by proteolysis of the BSA. The binding induces a red-shift of the maximal UV-Vis absorbance wavelength of CT-03 around 470 nm, likely due to localization of CT-03 in the relatively hydrophobic region of the protein. The interaction between CT-03 and BSA is driven by a hydrophobic interaction with an estimated binding constant of 2.18 ×10⁵ M^-1 at 298 K. Furthermore, only one CT-03 is bound to each molecule of BSA and the binding site is determined to be the sub-domain IIA (Sudlow's site I). This protein binding of the trityl probe to albumin can be used to study the structure and function of albumin and also must be considered for its use as an in vivo imaging agent or spin label.

Cooperative self-assembly of peptide gelators and proteins

Molecular self-assembly provides a versatile route for the production of nanoscale materials for medical and technological applications. Herein, we demonstrate that the cooperative self-assembly of amphiphilic small molecules and proteins can have drastic effects on supramolecular nanostructuring of resulting materials. We report that mesoscale, fractal-like clusters of proteins form at concentrations that are orders of magnitude lower compared to those usually associated with molecular crowding at room temperature. These protein clusters have pronounced effects on the molecular self-assembly of aromatic peptide amphiphiles (fluorenylmethoxycarbonyl- dipeptides), resulting in a reversal of chiral organization and enhanced order through templating and binding. Moreover, the morphological and mechanical properties of the resultant nanostructured gels can be controlled by the cooperative self-assembly of peptides and protein fractal clusters, having implications for biomedical applications where proteins and peptides are both present. In addition, fundamental insights into cooperative interplay of molecular interactions and confinement by clusters of chiral macromolecules is relevant to gaining understanding of the molecular mechanisms of relevance to the origin of life and development of synthetic mimics of living systems.

Molecular Modeling and Spectroscopic Studies on the Interaction of Transresveratrol with Bovine Serum Albumin

The interaction of transresveratrol (TRES) with bovine serum albumin (BSA) has been investigated by ultraviolet-visible, fluorescence, Fourier transform infrared spectroscopic methods and molecular modeling techniques. The fluorescence results show that the intrinsic fluorescence of BSA is quenched by TRES through a static quenching procedure. The binding constants of TRES with BSA at 292, 297 and 302 K are calculated as10.22×104,8.71×104, and7.59×104 L mol−1, respectively, and corresponding numbers of binding sites are approximately equal to unity. The thermodynamic parameters ΔHand ΔSare estimated to be −21.82 kJ mol−1and +21.15 J mol−1 K−1, which indicates that the interaction of TRES with BSA is driven mainly by hydrophobic forces and there are also hydrogen bonds and electrostatic interactions. The competitive experiments suggest that the binding site of TRES to BSA is probably located on site II. The results of infrared spectra show that the binding of TRES with BSA leads to conformational changes of BSA, and the binding stabilizes theα-helix andβ-sheet at the cost of a corresponding loss in theβ-turn structure of BSA. The results of molecular modeling calculation clarify the binding mode and the binding sites which are in good accordance with the experiment results.

A simple molecular modeling method for the characterization of polymeric drug carriers

A simple molecular modeling method for the characterization of polymeric drug carriers is presented. Six biodegradable polymers have been investigated as drug carriers using molecular simulations: l-polylactide, d-polylactide, chitosan, polyglycolic acid, polyethylene glycol and cellulose. Cyclosporine A has been chosen as a model drug substance. Classical molecular dynamics and docking calculations were employed to model and predict polymer-drug interactions. These interactions have been analyzed by non-bond interaction energy and interaction parameter calculated using Flory-Huggins theory. Flexibility of polymer chains has been characterized by the change of gyration radius along the molecular dynamics trajectory. The relationship between mixing energy, chain length and chain flexibility has been revealed for each polymer/drug system.

Use of spectroscopic, zeta potential and molecular dynamic techniques to study the interaction between human holo-transferrin and two antagonist drugs: comparison of binary and ternary systems

For the first time, the binding of ropinirole hydrochloride (ROP) and aspirin (ASA) to human holo-transferrin (hTf) has been investigated by spectroscopic approaches (fluorescence quenching, synchronous fluorescence, time-resolved fluorescence, three-dimensional fluorescence, UV-vis absorption, circular dichroism, resonance light scattering), as well as zeta potential and molecular modeling techniques, under simulated physiological conditions. Fluorescence analysis was used to estimate the effect of the ROP and ASA drugs on the fluorescence of hTf as well as to define the binding and quenching properties of binary and ternary complexes. The synchronized fluorescence and three-dimensional fluorescence spectra demonstrated some micro-environmental and conformational changes around the Trp and Tyr residues with a faint red shift. Thermodynamic analysis displayed the van der Waals forces and hydrogen bonds interactions are the major acting forces in stabilizing the complexes. Steady-state and time-resolved fluorescence data revealed that the fluorescence quenching of complexes are static mechanism. The effect of the drugs aggregating on the hTf resulted in an enhancement of the resonance light scattering (RLS) intensity. The average binding distance between were computed according to the forster non-radiation energy transfer theory. The circular dichroism (CD) spectral examinations indicated that the binding of the drugs induced a conformational change of hTf. Measurements of the zeta potential indicated that the combination of electrostatic and hydrophobic interactions between ROP, ASA and hTf formed micelle-like clusters. The molecular modeling confirmed the experimental results. This study is expected to provide important insight into the interaction of hTf with ROP and ASA to use in various toxicological and therapeutic processes.