Molecular interaction of 2,4-diacetylphloroglucinol (DAPG) with human serum albumin (HSA): The spectroscopic, calorimetric and computational investigation

Interaction studies of cannabidiol with human serum albumin by surface plasmon resonance, spectroscopy, and molecular docking

The binding interaction of cannabidiol (CBD) and human serum albumin (HSA) under physiological blood pH conditions (pH 7.4) was conducted by surface plasmon resonance (SPR), fluorescence spectroscopy, UV-Visible spectrophotometry, and molecular docking. The responses from SPR measurement increased with the increase in CBD concentration until equilibrium was reached at the equilibrium dissociation constant (KD) of 9.8 × 10-4 M. The results from fluorescence and UV-Visible spectroscopy showed that CBD bound to HSA at one site in a spontaneous manner to form protein-CBD complexes. The quenching process involved both static and dynamic mechanisms while the static mechanism contributed predominantly to the binding between CBD and albumin. The binding constants estimated from the fluorescence studies were from 0.16 × 103 to 8.10 × 103 M-1, which were calculated at different temperature conditions using Stern-Volmer plots. The thermodynamic parameters demonstrated that the binding interaction was a spontaneous reaction as Gibbs free energy had negative values (ΔG = -12.57 to -23.20 kJ.mol-1). Positive ΔH and ΔS values (ΔH = 2.46 × 105 J.mol-1 and ΔS = 869.81 J.mol-1K-1) indicated that the hydrophobic force was the major binding interaction. Finally, confirmation of the type and extent of interaction was provided using UV-spectroscopy and molecular docking studies. The outcomes of this study are expected to serve as a platform to conduct future studies on binding interactions and toxicological research of CBD.Communicated by Ramaswamy H. Sarma.

Interaction mechanism of a cysteine protease inhibitor, odanacatib, with human serum albumin: In vitro and bioinformatics studies

Odanacatib (ODN) is a selective cathepsin K inhibitor that acts as an anti-resorptive agent to treat osteoporosis. ODN is also found effective in reducing the effect of severe periodontitis. The interaction between ODN and human serum albumin (HSA) was investigated using spectroscopic, microscopic, and in silico approaches to characterize their binding. The fluorescence intensity of HSA increased upon the addition of increasing concentrations of ODN accompanied by blueshift in the fluorescence spectrum, which suggested hydrophobic formation around the microenvironment of the fluorophores upon ODN binding. A moderate binding affinity was obtained for ODN-HSA binding, with binding constant (Ka) values of ∼104 M-1. Circular dichroism results suggested that the overall secondary and tertiary structures of HSA were both only slightly altered upon ODN binding. The surface morphology of HSA was also affected upon ODN binding, showing aggregate formation. Drug displacement and molecular docking results revealed that ODN preferably binds to site III in subdomain IB of HSA, while molecular dynamics simulations indicated formation of a stable protein complex when site III was occupied by ODN. The ODN-HSA complex was mainly stabilized by a combination of hydrogen bonding, hydrophobic interactions, and van der Waals forces. These findings provide additional information to understand the interaction mechanism of ODN in blood circulation and may help in future improvements on the adverse effects of ODN.

Exploring the binding mechanism and adverse toxic effects of degradation metabolites of pyrethroid insecticides to human serum albumin: Multi-spectroscopy, calorimetric and molecular docking approaches

Pyrethroid insecticides (PIs), a class of structurally similar non-persistent organic pollutants, can be degraded and metabolized to more toxic, and longer half-life products. In this study, the binding interaction mechanisms between human serum albumin (HSA) and the main degradation metabolites of PIs, 3-phenoxybenzoic acid (3-PBA) and 4-fluoro-3-phenoxybenzoic acid (4-F-3-PBA), were studied by theoretical simulation and experimental verification. Steady state fluorescence spectra showed that the fluorescence quenching mechanism was static. According to the binding constant, 4-F-3-PBA (1.53 × 105 L mol-1) was bound more strongly to HSA than 3-PBA (1.42 × 105 L mol-1) in subdomain ⅡA (site I). It was found by isothermal titration calorimetry that the metabolites and HSA spontaneously combined mainly through hydrogen bond and van der Waals interaction. Ultraviolet absorption spectra and circular dichroism spectra showed that the metabolites caused slight changes in the microenvironment and conformation of HSA. The above results were proved by molecular docking. The toxicity properties of the metabolites were further analyzed by software, and 4-F-3-PBA was found to be more toxic than 3-PBA. Considering the high exposure level of these metabolites in food, the environment and human body, it is necessary to further explore the toxicity of PIs metabolites.

Gallium and indium complexes with isoniazid-derived ligands: Interaction with biomolecules and biological activity against cancer cells and Mycobacterium tuberculosis

Gallium and indium octahedral complexes with isoniazid derivative ligands were successfully prepared. The ligands, isonicotinoyl benzoylacetone (H₂L¹) and 4-chlorobenzoylacetone isonicotinoyl hydrazone (H₂L²), and their respective coordination compounds with gallium and indium [GaL¹(HL¹)] (GaL¹), [GaL²(HL²)] (GaL²), [InL¹(HL¹)] (InL¹) and [InL²(HL²)] (InL²) were investigated by NMR, ESI-MS, UV-Vis, IR, single-crystal X-ray diffraction and elemental analysis. In vitro interaction studies with human serum albumin (HSA) evidenced a moderate affinity of all complexes with HSA through spontaneous hydrophobic interactions. The greatest suppression of HSA fluorescence was caused by GaL² and InL², which was associated to the higher lipophilicity of H₂L². In vitro interaction studies with CT-DNA indicated weak interactions of the biomolecule with all complexes. Cytotoxicity assays with MCF-7 (breast carcinoma), PC-3 (prostate carcinoma) and RWPE-1 (healthy human prostate epithelial) cell lines showed that complexes with H₂L² are more active and selective against MCF-7, with the greatest cytotoxicity observed for InL² (IC₅₀ = 10.34 ± 1.69 μM). H₂L¹ and H₂L² were labelled with gallium-67, and it was verified that ⁶⁷GaL² has a greater lipophilicity than ⁶⁷GaL¹, as well as higher stability in human serum or in the presence of apo-transferrin. Cellular uptake assays with ⁶⁷GaL¹ and ⁶⁷GaL² evidenced that the H₂L²-containing radiocomplex has a higher accumulation in MCF-7 and PC-3 cells than the non-halogenated congener ⁶⁷GaL¹. The anti-Mycobacterium tuberculosis assays revealed that both ligands and metal complexes are potent growth inhibitors, with MIC₉₀ (μg mL^-1) values observed from 0.419 ± 0.05 to 1.378 ± 0.21.

Pseudouridimycin-A Potent Nucleoside Inhibitor of the RNA Polymerase Beta Prime Subunit of Streptococcus pyogenes

Streptococcus pyogenes (group A streptococcus, GAS), a Gram-positive bacterium, is a major cause of mild to severe life-threatening infections. Antibacterial resistance to penicillin and macrolides poses a major threat in the treatment of GAS and necessitates alternate drugs and newer antibiotics. In this direction, nucleotide-analog inhibitors (NIAs) have emerged as important antiviral, antibacterial, and antifungal agents. Pseudouridimycin (PUM), a nucleoside analogue inhibitor discovered from the soil bacterium Streptomyces sp., has proven to be effective against multidrug-resistant S. pyogenes. However, the mechanism of its activity remains elusive. In this study, subunits of the RNA polymerase of GAS have been identified as targets for PUM inhibition and the binding regions have been mapped to the N-terminal domain of the β' subunit, using computational methods. The antibacterial activity of PUM against macrolide-resistant GAS was evaluated. PUM showed effective inhibition at 0.1-1 μg/mL concentration, which was higher when compared to earlier reports. The molecular interaction between PUM and the RNA polymerase β'-N terminal subunit was investigated using isothermal titration calorimetry (ITC), circular dichorism (CD), and intrinsic fluorescence spectroscopy. The thermodynamic characterization by ITC showed an affinity constant of 6.175 × 10⁵ M^-1 denoting a moderate affinity. Fluorescence studies revealed that the interaction of protein-PUM was spontaneous in nature and follows a static quenching of tyrosine signals from the protein. The near- and far-UV CD spectral analysis concluded that PUM induced local tertiary structural changes in the protein, predominantly contributed by aromatic amino acids rather than notable changes in the secondary structure. Hence PUM could be a promising lead drug target for macrolide-resistant strains of S. pyogenes and enable eradication of pathogen in the host system.

New look at the metabolism of nonsteroidal anti-inflammatory drugs: influence on human serum albumin antioxidant activity

Body's homeostasis is dependent on many factors, such as maintaining balance between free radicals formation and degradation. Human serum albumin (HSA) also plays an important role in homeostasis. The aim of this study was thermodynamic analysis of the interaction between ketoprofen (KET), naproxen (NPX), diclofenac (DIC) and HSA, as well as the effect of drug-albumin binding on HSA antioxidant activity using calorimetric and spectrophotometric techniques. Based on the calorimetric analysis it has been shown that accompanied by hydrophobic interaction drugs-albumin binding is an exoenergetic reaction. All analyzed drugs and HSA showed the ability to react with free radicals such as a radical cation, formed as a result of the reaction between 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and potassium persulfate (K₂S₂O₈). Using ABTS assay a synergistic effect of ketoprofen (KET) and naproxen (NPX) on HSA antioxidant activity was observed while the effect of diclofenac (DIC) binding with albumin was probably additive. Because some medications including KET, NPX and DIC belong to over the counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs), it is necessary to understand their influence on HSA antioxidant activity.Communicated by Ramaswamy H. Sarma.

Elucidation of the binding mechanism of astragaloside IV derivative with human serum albumin and its cardiotoxicity in zebrafish embryos

LS-102 is a new derivative of astragaloside IV (AGS IV) that has been shown to possess potentially significant cardioprotective effects. However, there are no reports concerning its interaction with human serum albumin (HSA) and toxicology in vertebrates. The present investigation was undertaken to characterize the interaction of AGS IV and LS-102 with HSA using equilibrium dialysis and UHPLC-MS/MS methods, along with computational methods. Notably, the effects of AGS IV and LS-102 were studied in vivo using the zebrafish embryo model. Markers related to embryonic cardiotoxicity and thrombosis were evaluated. We showed that the plasma protein binding rate of AGS IV (94.04%–97.42%) was significantly higher than that of LS-102 (66.90%–69.35%). Through site marker competitive experiments and molecular docking, we found that AGS IV and LS-102 were located at the interface of subdomains IIA and IIIA, but the site I might be the primary binding site. Molecular dynamics revealed that AGS IV showed a higher binding free energy mainly due to the stronger hydrophobic and hydrogen bonding interactions. Moreover, the secondary structure implied no obvious effect on the protein structure and conformation during the binding of LS-102. LS-102 significantly ameliorated the astramizole-induced heart rate slowing, increased SV-BA spacing, and prevented arachidonic acid-induced thrombosis in zebrafish. To our knowledge, we are the first to reveal that LS-102 binds to HSA with reversible and moderate affinity, indicating its easy diffusion from the circulatory system to the target tissue, thereby providing significant insights into its pharmacokinetic and pharmacodynamic properties when spread in the human body. Our results also provide a reference for the rational clinical application of LS-102 in the cardiovascular field.

2,4-Diacetylphloroglucinol producing Pseudomonas fluorescens JM-1 for management of ear rot disease caused by Fusarium moniliforme in Zea mays L

Maize (Zea mays L.) is a major cereal crop grown in a large number of countries. Loss in maize yield due to biotic stresses including fungal phytopathogens is a matter of immense concern. Control measures applied for eradication of fungal phytopathogens in maize are not up to the mark and more often involve harsh chemical(s)/pesticide(s) that cause deleterious effects both in humans and soil biota. Greener alternatives, such as the use of rhizosphere microbes in the form of bioinoculants, have proven to be very successful in terms of enhancing crop yield and suppressing fungal phytopathogens. In the present study, fluorescent pseudomonads were isolated from the maize rhizosphere and monitored for their plant growth-promoting (PGP) and biocontrol activities against Fusarium moniliforme. Based on various PGP traits and biocontrol potential, isolate JM-1 was found to be most effective and as per 16S rRNA gene sequencing analysis was identified as Pseudomonas fluorescens. Further experiments showed that the biocontrol potential of JM-1 against ear rot fungus involved the production of antifungal compound 2,4-diacetylphloroglucinol (DAPG). When examined for antagonistic interaction under scanning electron microscopy (SEM), structural abnormality, hyphal lysis, and deformity in fungal mycelium were observed. In the pot experiment, application of talc-based JM-1 containing bioformulation (in pot trials) showed significant enhancement in maize growth parameters (including the seed number and weight) in comparison to control even in presence of the phytopathogen. Ear fresh weight, dry weight, number of seeds per plant, and 100-grain weight were found to increase significantly by 34, 34, 52, and 18% respectively, in comparison to control. P. fluorescens JM-1 can therefore be used as a bioinoculant for ear rot disease control and sustainably enhancing maize yield.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03201-7.

Emerging Albumin-Binding Anticancer Drugs for Tumor-Targeted Drug Delivery: Current Understandings and Clinical Translation

Albumin has shown remarkable promise as a natural drug carrier by improving pharmacokinetic (PK) profiles of anticancer drugs for tumor-targeted delivery. The exogenous or endogenous albumin enhances the circulatory half-lives of anticancer drugs and passively target the tumors by the enhanced permeability and retention (EPR) effect. Thus, the albumin-based drug delivery leads to a potent antitumor efficacy in various preclinical models, and several candidates have been evaluated clinically. The most successful example is Abraxane, an exogenous human serum albumin (HSA)-bound paclitaxel formulation approved by the FDA and used to treat locally advanced or metastatic tumors. However, additional clinical translation of exogenous albumin formulations has not been approved to date because of their unexpectedly low delivery efficiency, which can increase the risk of systemic toxicity. To overcome these limitations, several prodrugs binding endogenous albumin covalently have been investigated owing to distinct advantages for a safe and more effective drug delivery. In this review, we give account of the different albumin-based drug delivery systems, from laboratory investigations to clinical applications, and their potential challenges, and the outlook for clinical translation is discussed. In addition, recent advances and progress of albumin-binding drugs to move more closely to the clinical settings are outlined.

Unveiling the interaction mechanism of alogliptin benzoate with human serum albumin: Insights from spectroscopy, microcalorimetry, and molecular docking and molecular dynamics analyses

The interaction between a DPP-4 inhibitor, alogliptin benzoate (AB), and human serum albumin (HSA) was systematically investigated via spectroscopy, microcalorimetry and molecular simulations. Steady-state fluorescence and time-resolved fluorescence spectrometry illustrated that the fluorescence quenching type of AB to HSA was static and caused by the formation of ground state AB-HSA complex. Isothermal titration calorimetry (ITC) combined with fluorescence spectra revealed that the affinity of AB to the subdomain IIA of HSA was moderate with a binding constant in the order of 10⁴. Molecular docking analysis and thermodynamic parameters demonstrated that this combination was maintained by hydrogen bonding along with van der Waals force and hydrophobic force. Circular dichroism and three-dimensional (3D) fluorescence showed that AB increased the hydrophobicity of Trp residue and the α-helix content of HSA by 1.99%. Microdifferential scanning calorimetry revealed that the addition of AB enhanced the thermal stability of HSA. The action forces, binding stability, binding sites, and protein structure of the AB-HSA system were evaluated via molecular dynamics analysis in the simulated environment. On the basis of molecular docking, MD simulation constructed a more reliable 3D model of the AB-HSA complex in terms of spatial structure.

Investigation of the binding properties between levamlodipine and HSA based on MCR-ALS and computer modeling

Levamlodipine (LEE) is a drug commonly used for antihypertensive treatment in clinical therapy. The overlapping fluorescence spectra of LEE and human serum albumin (HSA) cause some trouble in analysis of interactions between them by using the classic fluorescence method. Here, the multivariate curve resolution-alternating least squares (MCR-ALS) approach was used to overcome this disadvantage. Meanwhile, the binding properties of LEE-HSA complex were then explored through computer modeling. The MCR-ALS results suggested that LEE-HSA complex was present in the mixture solution of LEE and HSA. This conclusion was then confirmed by the Stern-Volmer equation and time-resolved fluorescence experiment. The binding constant (K_a) was 2.139 × 10⁴ L·mol^-1 at 298 K. LEE was located close to the Trp-214 residue of HSA, with van der Waals forces and hydrogen bonding as main driving forces for this interaction. LEE can alter the conformation of HSA, in which the content of α-helix reduced from 57.2% to 52.3%. The Pi-Alkyl interactions contributed to maintaining the stability of the LEE-HSA complex. The results of molecular dynamics simulations showed that LEE-HSA complex was formed within 5 ns, and the particle size (R_g) of HSA was altered by the binding reaction. This study would promote better understanding of the transportation and distribution mechanisms of LEE in the human body.

The study on the interactions of two 1,2,3-triazoles with several biological macromolecules by multiple spectroscopic methodologies and molecular docking

1-(4-chlorophenyl)-5-phenyl-1H-1,2,3-triazole (CPTC) and 5-(3-chlorophenyl) -1-phenyl-1H-1,2,3-triazole (PCTA) are two new derivatives of 1,2,3-triazole. Their structural and spectral properties were characterized by density functional theory calculations (DFT). The binding properties of CPTC or PCTA with several typical biomacromolecules such as human serum albumin (HSA), bovine hemoglobin (BHb), human immunoglobulin (HIgG) or DNA were investigated by molecular docking and multiple spectroscopic methodologies. The different parameters including binding constants and thermodynamic parameters for CPTC/PCTA-HSA/BHb/HIgG/DNA systems were obtained based on various fluorescence enhancement or quenching mechanisms. The results of binding constants indicated that there were the strong interactions between two triazoles and four biological macromolecules due to the higher order of magnitude between 10³ and 10⁵. The values of thermodynamic parameters revealed that the binding forces for these systems are mainly hydrophobic interactions, electrostatic force, or hydrogen bond, respectively, which are in agreement with the results of molecular docking to a certain extent. Moreover, the information from synchronous, 3D fluorescence and UV-Vis spectroscopies proved that two compounds CPTC and PCTA could affect the microenvironment of amino acids residues of three kinds of proteins. Based on the above experimental results, a comparison of the interaction mechanisms for CPTC/PCTA-proteins/DNA systems have been performed in view of their different molecular structures, which is beneficial for the further research in order to design them as the novel drugs.

Albumin as a drug: its biological effects beyond volume expansion

Albumin is the most abundant and perhaps most important protein in human blood. Research has identified many of albumin's possible roles in modulating acid-base balance, modifying inflammation, maintaining vascular endothelial integrity, and binding endogenous and exogenous compounds. Albumin plays a key role in the homeostasis of vascular endothelium, offering protection from inflammation and damage to the glycocalyx. Albumin binds a diverse range of compounds. It transports, delivers and clears drugs, plus it helps with uptake, storage and disposal of potentially harmful biological products. The biological effects of albumin in critical illness are incompletely understood, but may enhance its clinical role beyond use as an intravenous fluid. In this article, we summarise the evidence surrounding albumin's biological and physiological effects beyond its use for plasma volume expansion, and explore potential mechanistic effects of albumin as a disease modifier in patients with critical illness.

Interaction between aspirin and vitamin C with human serum albumin as binary and ternary systems

Foods generally contain special ingredients which easily to interact with drugs human intaking, thus affecting drug efficacy and excretion, and even cause adverse reactions. Vitamin C (Vit. C) is abundant in fresh fruits and vegetables. It plays a regulatory role in redox metabolism, and its absence can cause scurvy. Aspirin (ASP) can be used to treat many diseases, is the earliest, common and widely used as antipyretic, analgesic and antirheumatic medicine. Human serum albumin (HSA) is the most abundant protein in vertebrate plasma and has the property of combining and transporting endogenous and exogenous substances. In this paper, the effects of Vit. C on the combination of ASP and HSA were studied by multi-spectra and voltammetric approaches. Fluorescence spectra showed that the quenching mode between Vit. C and HSA is dynamic, and the main binding force is hydrophobic force. The quenching mode between ASP and HSA is static one, and the main binding force is hydrogen bond and van der Waals force. For ternary biological system of (HSA-ASP)-Vit. C, the binding constant decreases compared with HSA-Vit. C system. However, for (HSA-Vit. C)-ASP system, the binding constant does not change when compared with binary system of HSA-ASP. Based on the technology combination of voltammetry, infrared, three-dimensional fluorescence and circular dichroism (CD), it is proved that the existence of ASP will influence the binding process of Vit. C to HSA. It could be concluded that taking Vit. C first doesn't affect the absorption of ASP and may be good for health; in contrast, it is not good to take Vit. C immediately as one have just taken ASP, because the existence of ASP reduce the absorption of Vit. C for human body.

Biomolecular interactions and binding dynamics of tyrosine kinase inhibitor erdafitinib, with human serum albumin

Erdafitinib is an approved tyrosine kinase inhibitor that inhibits fibroblast growth factor receptor. It has been described as one of the potent anti-tumor drugs especially for the treatment of urothelial carcinoma. In this study, we have investigated the binding dynamics of erdafitinib with human serum albumin (HSA) using multiple spectroscopic techniques. The outcome of the results suggests the occurrence of static quenching during the interaction of HSA with erdafitinib which leads to the formation of non-fluorescent HSA-erdafitinib ground state complex. Formation of HSA-erdafitinib complex was also confirmed from the findings of absorption spectral analysis. The changes in microenvironment around hydrophobic domains (especially tryptophan and tyrosine) were deciphered from fluorescence spectroscopy which was further confirmed by synchronous spectral analysis. In order to gain insight into the binding site of erdafitinib in HSA, molecular docking combined with competitive displacement assay was performed. The modified form of Stern Volmer equation was used to estimate various binding parameters including number of binding sites. The findings are indicative of a single binding site (n = 1) with binding constant in the order of 10⁴. The negative values of thermodynamic parameters like ΔG, ΔH and ΔS were suggestive of the binding reaction being spontaneous and exothermic, while the hydrogen bonds and Van der Waals interactions being the major forces present between HSA and erdafitinib. Circular dichroism spectral analysis revealed the alterations in the conformation of HSA structure and reduction in its α-helical content.Communicated by Ramaswamy H. Sarma[Formula: see text].

Opo FD, Shahriar M, Akhter R, Halim MA. A possible alternative therapy for type 2 diabetes using Myristica fragrans Houtt in combination with glimepiride: in vivo evaluation and in silico support

The current study aimed to evaluate the in vivo hypoglycemic potential of Myristica fragrans seed extract co-administered with glimepiride in Swiss albino mice. Computational tools were used to further verify the in vivo findings and to help compare this combination to the glimepiride-pioglitazone combination in terms of the binding affinity of the ligands to their respective target protein receptors and the relative stability of the drug-protein complexes. The effect of the combined therapy was observed both in alloxan- and glucose-induced hyperglycemic Swiss albino mice. The mean fasting blood glucose level of the test groups was measured and statistically evaluated using Student’s t test. The combined therapy significantly reduced the blood glucose level in a time-dependent manner compared to glimepiride alone. The binding affinity of glimepiride was found to be −7.6 kcal/mol with sulfonylurea receptor 1 in molecular docking. Conversely, macelignan-peroxisome proliferator-activated receptor (PPAR) α and macelignan-PPAR γ complexes were stabilized with −9.2 and −8.3 kcal/mol, respectively. Molecular dynamic simulation revealed that macelignan-PPAR α and γ complexes were more stable than pioglitazone complexes. The combination shows promise in animal and computer models and requires further trials to provide evidence of its activity in humans.

New selective thiolate gold(i) complexes inhibit the proliferation of different human cancer cells and induce apoptosis in primary cultures of mouse colon tumors

New thiolate gold(i) complexes with P(NMe₂)₃ (HMPT) as phosphane group have been developed as proapoptotic and selective anticancer drugs.

Twisted intramolecular charge transfer (TICT) based fluorescent probe for lighting up serum albumin with high sensitivity in physiological conditions

Accurate detection of human serum albumin (HSA) in biological samples is quite meaningful for early disease diagnosis and treatment. Herein, a novel fluorescent probe 1-ethyl-4-[2-[4-(diethylamino)-2-hydroxyphenyl]ethenyl]]-pyridinium salt (DEHP) was developed for HSA determination. The inherent fluorescence of DEHP is essentially negligible at physiological conditions assigned to the well-developed twisted intramolecular charge transfer (TICT) protocol. An intriguing fluorescence light up is triggered as the addition of HSA, on account of the inhibited TICT procedure when DEHP enters the hydrophobic cavity of protein HSA. This combination leads to a turn on fluorescent response for HSA with a detection limit of 4.8 nM. After an overall investigation, it has been proved that the strong binding between DEHP and HSA is specific-site-related. In additional, the probe implies a great potential to assist clinical diagnosis due to the usage in actual serum detection. Cell imaging also shows that the probe is expected to monitor HSA production process at cell level.

High Potency of SN-38-Loaded Bovine Serum Albumin Nanoparticles Against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer with a worse prognosis than other types. There are currently no specific approved treatments for TNBC. Albumin is a promising biomimetic material that may be fabricated into nanoparticles to possibly exert passive effects on targeted tumors. Irinotecan has been extensively used in clinical settings, although a high dosage is required due to its low efficiency of conversion into the active metabolite SN-38, also known as 7-ethyl-10-hydroxy-camptothecin. The aim of this work was to optimize SN-38-loaded bovine serum albumin nanoparticles (sBSANPs) and evaluate their potency against TNBC. The sBSANPs were characterized by a small size of about 134-264 nm, a negative charge of -37 to -40 mV, an entrapment efficiency of 59-71%, and a particle yield of 65-86%. The cytotoxicity assays using sBSANPs showed a higher potency specifically against both MDA-MB-468 and MDA-MB-231 cells (ER-, PR-, HER2-) compared to MCF-7 (ER+, PR+, HER2-), and exhibited an extremely low IC₅₀ at the nanomolar levels (2.01-6.82 nM). The release profiles indicated that SN-38 presented an initial burst release within 12 h, and sBSANPs had a slow release pattern. Flow cytometry results showed that the fluorescence intensity of sBSANPs was significantly higher than that of the control group. The confocal images also confirmed that sBSANPs were taken up by MDA-MB-468 cells. Moreover, we found that a larger BSANP size resulted in an increased hemolytic effect. In vivo animal studies demonstrated that loading of SN-38 into bovine serum albumin nanoparticles could minimize the initial concentration without extending the elimination half-life, but significantly minimized the Cmax (p < 0.001) as compared with irinotecan treatment.

Capping gold nanoparticles with albumin to improve their biomedical properties

Nanotechnology is an emerging field which has created great opportunities either through the creation of new materials or by improving the properties of existing ones. Nanoscale materials with a wide range of applications in areas ranging from engineering to biomedicine have been produced. Gold nanoparticles (AuNPs) have emerged as a therapeutic agent, and are useful for imaging, drug delivery, and photodynamic and photothermal therapy. AuNPs have the advantage of ease of functionalization with therapeutic agents through covalent and ionic binding. Combining AuNPs and other materials can result in nanoplatforms, which can be useful for biomedical applications. Biomaterials such as biomolecules, polymers and proteins can improve the therapeutic properties of nanoparticles, such as their biocompatibility, biodistribution, stability and half-life. Serum albumin is a versatile, non-toxic, stable, and biodegradable protein, in which structural domains and functional groups allow the binding and capping of inorganic nanoparticles. AuNPs coated with albumin have improved properties such as greater compatibility, bioavailability, longer circulation times, lower toxicity, and selective bioaccumulation. In the current article, we review the features of albumin, as well as its interaction with AuNPs, focusing on its biomedical applications.

Enantioseparation, recognition mechanisms and binding of xanthones on human serum albumin by liquid chromatography

Aim: To develop a method for enantioseparation of several chiral derivatives of xanthones (CDXs) by LC using a human serum albumin-chiral stationary phase (HSA-CSP) and screening CDX-HSA affinity. Additionally, recognition mechanisms were investigated. Materials & methods: The influence of organic modifier, buffer type, pH and ionic strength of mobile phase, and temperature were explored. The affinity was determined by measuring the retention times and further calculation of bound percentage. Chiral recognition mechanisms were investigated by docking. Results: Enantioselectivity and resolution values ranged from 1.40 to 9.16 and 1.51 to 4.97. Bound percentages ranged from 79.02 to 99.99%. Conclusion: LC systematic study and binding affinity of CDXs on HSA-CSP are presented here for the first time, expanding the applications of HSA-CSP for this class of compounds.

Glutathione S-transferase omega 1 inhibition activates JNK-mediated apoptotic response in breast cancer stem cells

Glutathione S-transferase omega 1 (GSTO1) contributes to the inactivation of a wide range of drug compounds via conjugation to glutathione during phase reactions. Chemotherapy-induced GSTO1 expression in breast cancer cells leads to chemoresistance and promotes metastasis. In search of novel GSTO1 inhibitors, we identified S2E, a thia-Michael adduct of sulfonamide chalcone with low LC₅₀ (3.75 ± 0.73 μm) that binds to the active site of GSTO1, as revealed by molecular docking (glide score: -8.1), cellular thermal shift assay and fluorescence quenching assay (K_b  ≈ 10 × 10⁵  mol·L^-1 ). Docking studies confirmed molecular interactions between GSTO1 and S2E, and identified the hydrogen bond donor Val-72 (2.14 Å) and hydrogen bond acceptor Ser-86 (2.77 Å). Best pharmacophore hypotheses could effectively map S2E and identified the 4-methyl group of the benzene sulfonamide ring as crucial to its anti-cancer activity. Lack of a thiophenyl group in another analog, 2e, reduced its efficacy as observed by cytotoxicity and pharmacophore matching. Furthermore, GSTO1 inhibition by S2E, along with tamoxifen, led to a significant increase in apoptosis and decreased migration of aggressive MDA-MB-231 cells, as well as significantly decreased migration, invasion and mammosphere formation in sorted breast cancer stem cells (CSCs, CD24^- /CD44⁺ ). GSTO1 silencing in breast CSCs also significantly increased apoptosis and decreased migration. Mechanistically, GSTO1 inhibition activated the c-Jun N-terminal kinase stress kinase, inducing a mitochondrial apoptosis signaling pathway in breast CSCs via the pro-apoptotic proteins BAX, cytochrome c and cleaved caspase 3. Our study elucidated the role of the GSTO1 inhibitor S2E as a potential therapeutic strategy for preventing chemotherapy-induced breast CSC-mediated cancer metastasis and recurrence.

Interaction of repaglinide with bovine serum albumin: Spectroscopic and molecular docking approaches

Repaglinide (RPG) regulates the amount of glucose by stimulating the pancreas to release insulin in the blood. In view of its biological importance, we have examined the interaction between RPG and a model protein, bovine serum albumin (BSA) employing various spectroscopic, electrochemical and molecular docking methods. Fluorescence spectra of BSA were recorded in the presence and absence of RPG in phosphate buffer of pH 7.4. Fluorescence intensity of BSA was decreased upon the addition of increased concentrations of RPG, indicating the interaction between RPG and BSA. Stern-Volmer quenching analysis results revealed that RPG quenched the intensity of BSA through dynamic quenching mechanism. This was further confirmed from the time-resolved fluorescence measurements. The binding constant as calculated from the spectroscopic and voltammetric results was observed to be in the order of 10⁴ M⁻¹ at 298 K, suggesting the moderate binding affinity between RPG and BSA. Competitive experimental results revealed that the primary binding site for RPG on BSA was site II. Absorption and circular dichroism studies indicated the changes in the secondary structure of BSA upon its interaction with RPG. Molecular simulation studies pointed out that RPG was bound to BSA in the hydrophobic pocket of site II.

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Dynamic mode of quenching mechanism was noticed in RPG-BSA interaction.

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RPG was bound to BSA at the Sudlow’s site II and the resultant RPG-BSA complex was mainly stabilized by hydrophobic forces.

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The binding constant of RPG-BSA of the order of 10⁴ M⁻¹ at 298 K indicated the non-covalent interactions.

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Secondary structural changes in BSA upon binding to RPG were evident from absorption and circular dichroism studies.

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The influence of β-cyclodextrin and metal ions on RPG-BSA binding affinity was examined.

Mutual influence of piceatannol and bisphenol F on their interaction with pepsin: Insights from spectroscopic, isothermal titration calorimetry and molecular modeling studies

The individual and combined interactions of bisphenol F and piceatannol with pepsin were investigated using spectroscopic methods (fluorescence, UV-vis absorption, and circular dichroism spectroscopy), combined with isothermal titration calorimetry and molecular docking. Thermodynamic data showed that hydrogen bonds and van der Waals forces might play a major role for the binding process. Site marking experiments and molecular docking confirmed the binding sites of these two ligands on pepsin. The discrepancy in the binding constant between the binary and ternary systems indicated the competitive binding of piceatannol and bisphenol F to pepsin. Circular dichroism spectra studies suggested that the binding of the two ligands led to a loosening of pepsin backbone. Enzyme activity assays indicated that the inhibition of pepsin activity by piceatannol and bisphenol F was competitive. These results will be helpful to understand the mechanism of piceatannol and bisphenol F affecting the activity of digestive proteases in the sight of the food security.

Determination of interactions between human serum albumin and niraparib through multi-spectroscopic and computational methods

The interactions between 2-{4-[(3S)-piperidin-3-yl] phenyl}-2H-indazole-7-carboxamide (niraparib) and human serum albumin (HSA) were investigated through fluorescence and computational studies. Fluorescence experiments showed that the static quenching mechanism and the binding constant of the HSA-niraparib system at a single binding site was approximately 4 × 10⁴ L mol^-1. Thermodynamic constants indicated that the binding of niraparib to HSA was mainly driven by electrostatic interactions. Competition experiments and molecular docking simulations revealed that niraparib bound to site III of HSA. Synchronous fluorescence and Fourier transform infrared spectroscopy (FT-IR) results suggested that interactions between niraparib and HSA could affect the conformation and microenvironment of HSA. Circular dichroism (CD) measurements revealed that the α-helix contents of HSA negligibly increased after binding with niraparib. Molecular dynamics simulations demonstrated the stability of the binary HSA-niraparib system and confirmed that electrostatic forces accounted for the dominant contribution to system energy between HSA and niraparib.

Differences between the binding modes of enantiomers S/R-nicotine to acetylcholinesterase

Nicotine causes neurotoxic effects because it quickly penetrates the blood–brain barrier after entering the human body. Acetylcholinesterase (AChE) is a key enzyme in the central and peripheral nervous system associated with neurotoxicity. In this study, a spectroscopic method and computer simulation were applied to explore the mode of interaction between AChE and enantiomers of nicotine (S/R-nicotine). Fluorescence spectroscopy showed that the quenching mechanism of endogenous fluorescence of AChE by S/R-nicotine was static, as confirmed by the time-resolved steady-state fluorescence. The binding strength of both nicotine to AChE was weak (S-AChE: K_a = 80.06 L mol⁻¹, R-AChE: K_a = 173.75 L mol⁻¹). The main driving forces of S-AChE system interaction process were van der Waals force and hydrogen bonding, whereas that of R-AChE system was electrostatic force. Computer simulations showed that there were other important forces involved. S/R-Nicotine had a major binding site on AChE, and molecular docking showed that they bound mainly to the cavities enclosed by the active sites (ES, PAS, OH, AACS, and AP) in the protein. UV-vis spectroscopy and 3D spectroscopy indicated that nicotine significantly affected the microenvironment of Trp amino acids in AChE. The CD spectra indicated that S-nicotine increased the α-helical structure of AChE, but the overall conformation did not change significantly. By contrast, R-nicotine significantly changed the secondary structure of AChE. 5,5′-Dithiobis-2-nitrobenzoic acid (DTNB) method indicated that S and R nicotine produced different degrees of inhibition on the catalytic activity of AChE. Both experimental methods and computer simulations showed that R-nicotine had a significantly higher effect on AChE than S-nicotine. This research comprehensively and systematically analyzed the mode of interaction between nicotine and AChE for neurotoxicity assessment.

Study on the binding modes of AChE to S/R-nicotine.

Binding behavior of trelagliptin and human serum albumin: Molecular docking, dynamical simulation, and multi-spectroscopy

This study aims to investigate the interaction mechanism of a hypoglycemic agent, trelagliptin (TLP), and human serum albumin (HSA) through computer simulation and assisted spectroscopy methods. Computer simulation including molecular docking and molecular dynamics analysis was conducted under physiological conditions. Molecular docking results indicate that TLP bound to HSA at site I, and the binding behavior was mainly governed by hydrophobic force. Competitive experiments further verified the theoretical conclusion from molecular docking. Molecular dynamics simulation revealed that TLP indeed stably bound to site I of HSA in the hydrophobic subdomain IIA. Moreover, TLP presented a certain effect on the structural compactness of HSA. In molecular dynamics simulation, hydrogen bonds appeared, which suggested the reliability and stability of the combination. The binding energy of the stable phase is around -250 kJ/mol. Fluorescence quenching studies and time-resolved fluorescence analysis indicated that the evident fluorescence quenching phenomenon of HSA could be due to TLP binding initiated by static quenching mechanism. The binding constants (K_a) of the complex were found to be around 10⁴ via fluorescence data, and the calculated thermodynamic parameters indicated that hydrophobic force played major role in the binding of TLP to HSA. Synchronous fluorescence and three-dimensional fluorescence results demonstrated that TLP slightly disturbed the microenvironment of amino residues. Circular dichroism spectra showed that TLP affected the secondary structure of HSA. The theoretical and experimental results showed excellent agreement.

Interactions between the antiviral drug telaprevir and human serum albumin: a combined study with spectroscopic methods and molecular modeling

The binding mechanism between telaprevir and human serum albumin was explored by combining spectroscopic methods and molecular dynamics simulations.

Comparative studies on the interaction of nitrofuran antibiotics with bovine serum albumin

The study indicated that the nitrofurazone (NFZ) offered stronger toxicity than nitrofurantoin (NFT) in the interactions with albumin.