Interaction of eugenol-based anti-tuberculosis nanoemulsion with bovine serum albumin: A spectroscopic study including Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol

Tuberculosis (TB), a deadly infectious disease, is primarily caused by the bacterium Mycobacterium tuberculosis. The misuse of antibiotics has led to the development of drug resistance, prompting researchers to explore new technologies to combat multidrug-resistant Tuberculosis (MDR TB). Phospholipid-based nanotherapeutics, such as nanoemulsions, are gaining traction as they enhance drug solubility, stability, and bioavailability. Our study focuses on the interaction between Bovine Serum Albumin (BSA) and a drug-loaded nanoemulsion based on Eugenol. This nanoemulsion incorporates Eugenol, Clove, cinnamon oil, and first-line anti-tuberculosis drugs like Rifampicin, Isoniazid, Pyrazinamide, and Ethambutol. The primary objective is to assess the biosafety profile of the nanoemulsion upon interaction with BSA. We employed Fluorescence, UV-visible, and Fourier Transform Infrared Spectroscopy (FTIR) to analyze this interaction. UV-visible spectroscopy detected changes in hydrophobicity due to structural alterations in BSA near the tryptophan residue, leading to the formation of ground-state complexes. Fluorescence spectroscopy demonstrated that the nanoemulsion effectively quenched fluorescence originating from tryptophan and tyrosine residues. Studies using synchronous and three-dimensional spectroscopy point to a potential modification of the aromatic environment of BSA by the nanoemulsion. Resonance light scattering spectra indicated the formation of large aggregates due to the interaction with the nanoemulsion. The second derivative FTIR spectra showed an increase in the magnitude of secondary structure bands, suggesting a conformational shift. This research has significant pharmacological implications for developing safer, more targeted drug delivery systems. The information obtained from the interaction of the nanoemulsion with the blood carrier protein is vital for the future development of superior carriers with minimal adverse effects on patients. It is crucial to remember that conformational changes brought on by drug-ligand complexes attaching to carrier proteins may have negative consequences. Therefore, this study enhances the in vitro evaluation of potential adverse effects of the nanoemulsion on serum proteins.

Delivery Mechanism of the Pharmaceutical Complex of Genistein-Adenine Based on Spectroscopic and Molecular Modelling at Atomic Scale

Genistein (GS) exhibits various biological activities, but its clinical application is limited because of the low bioavailability. In this study, a GS-adenine pharmaceutical complex was prepared through solvent evaporation to improve the bioavailability of GS, and a molecular model of a two-component supramolecular pharmacological transport mechanism was established. The structure of GS-adenine was characterized, in addition, interaction patterns between GS and adenine were investigated using density functional theory. The results showed that the solubility of GS-adenine was five times higher than that of GS, and the cumulative release rate of GS-adenine was 86 %. The results of fluorescence spectroscopy and molecular dynamic simulations showed that GS-adenine bound to the Sudlow's site I of HSA mainly through hydrophobic interactions. This study provides a useful reference for synthesizing pharmaceutical complexes to improve solubility and for exploring the mechanism of multiple pharmaceutical components in vivo.

Exploring the binding interactions of janus green blue with serum albumins from spectroscopic and calorimetric studies aided by in silico calculations

Binding interactions of the phenazinium dye Janus green blue (JGB) with human and bovine serum albumins (BSA - and BSA) have been explored for the first time from multi-spectroscopic and calorimetric measurements aided by in silico calculations. The formation of ground state complexes between JGB and the respective serum albumins have been suggested from the UV-Vis and steady-state fluorescence spectroscopic studies. The nonlinear Stern Volmer (SV) plots at higher concentrations of JGB primarily indicate the formation of more than one ground state complexes in BSA -/BSA-JGB systems. Modified SV plots and isothermal titration calorimetry (ITC) studies however signify the possibilities of one type of binding complexes between HSA/BSA - JGB systems. Binding constants and the thermodynamic parameters associated with the HSA/BSA-JGB complexes have also been estimated from the ITC studies. Förster distances (R₀) for HSA-JGB and BSA-JGB complexes are estimated from Förster resonance energy transfer (FRET) results. Variations in the micro-environment of the Tyr and Trp residues of the serum proteins in presence of JGB have been observed from the synchronous fluorescence measurements. The conformational changes in the protein structures induced by the dye JGB have been revealed from 3 D fluorescence and circular dichroism (CD) studies. The experimental observations are supported by in silico calculations. This in depth investigation on the interactions of serum albumins with JGB may provide the fundamental information toward exploring the therapeutic efficacy of JGB as a potent drug molecule. Communicated by Ramaswamy H. Sarma.

Turning weakness into strength: Albumin nanoparticle-redirected amphotericin B biodistribution for reducing nephrotoxicity and enhancing antifungal activity

As the gold standard treatment for invasive fungal infection, amphotericin B (AmB) is limited by its severe nephrotoxicity. It has been shown that AmB complex with albumin in vivo forms a sub-10 nm nanocomplex within kidney excretion size range and eventually induces the nephrotoxicity. This study presents an approach to take advantage of the "weakness" of such unique interaction between AmB and albumin to form AmB nanocomplex beyond the size range of kidney excretion. Herein, a novel strategy was developed by directly assembling molecular BSA into larger-sized nanostructures with the reconstructed intermolecular disulfide bond and hydrophobic interaction. The rich binding sites of AmB within BSA nanostructures enabled the efficient AmB loading and forming nanoparticle (AmB-NP) which exceeds the size range of kidney excretion (~ 60 nm). We found nanoassembly with BSA redirected biodistribution of AmB with a 2.8-fold reduction of drug accumulation in the kidney and significantly improved its renal impairment in mice. Furthermore, we found that nanoassembly with BSA significantly increased the biodistribution of AmB in brain and endowed it 100-folds increase in pharmacological effect against meningoencephalitis caused by common fungal pathogen Cryptococcus neoformans. Together, this study not merely overcomes the nephrotoxicity of AmB using its "weakness" by a nanoassembly method, and provides a new strategy for reducing toxicity of drugs with high albumin binding rate in vivo.

Understanding the structure and conformation of bovine hemoglobin in presence of the drug hydroxyurea: multi-spectroscopic studies supported by docking and molecular dynamics simulation

Binding interaction between the small antitumor drug Hydroxyurea (HU) and Bovine Hemoglobin (BHb) has been explored in details from multi-spectroscopic and computational studies. The formation of ground state complex between BHb and HU has been suggested from the electronic UV-Vis and steady-state fluorescence spectroscopic studies. The quenching in fluorescence of BHb in presence of HU at varied concentrations has been analyzed from the SV plots. Static type of quenching has been suggested from time-resolved fluorescence spectroscopic studies. Binding parameters associated with the BHb-HU complex have also been estimated from the temperature dependent fluorescence spectroscopic studies. Alterations in the micro-environment of the Tyr and Trp residues of BHb in presence of HU have been observed from the synchronous fluorescence measurement. The result obtained from CD spectroscopic measurements signify partial unfolding in the secondary structure of BHb due to binding with HU molecule. The experimental observations are supported by theoretical studies. Molecular docking and molecular dynamics simulations have been performed to investigate the structural stability and compactness of BHb in the binding interaction between BHb and HU. The interaction of BHb with HU is expected to provide fundamental insights towards understanding the therapeutic effectiveness of HU upon interaction with BHb used in chemo-, radio therpeutic procedures and also in the treatment of SCD.

Structural alteration of myoglobin with two homologous cationic surfactants and effect of β-cyclodextrin: multifaceted insight and molecular docking study

Structural alteration and regeneration of myoglobin.

Spectroscopic and computational exploration of hypoxanthine riboside interacting with plasma albumin

Hypoxanthine riboside (HXR) is a nucleoside essential for wobble base pairs to translate the genetic code. In this work, an absorption and luminescence study showed that HXR and human serum albumin (HSA) formed a new complex through hydrogen bonds and van der Waals forces at ground state. Fluorescence probe experiments indicated that HXR entered the first subdomain of domain II in HSA and was fixed by amino acid residues in site I defined by Sudlow, and after competing with a known site marker. The recognition interaction featured negative ΔH^ϴ , ΔS^ϴ and ΔG^ϴ thermodynamic parameters. Fluorescence and circular dichroism spectra described the polarity of residues and α-helix and β-strand content changed because of HXR binding. The most rational structure for the HXR-HSA complex was recommended by the molecular docking method, in which the binding location, molecular orientation, adjacent amino acid residues, and hydrogen bonds were included. In addition, the influence of β-cyclodextrin and some essential metal ions on the balance of the HSA-HXR system interaction was measured. The study gained comprehensive information on the transportation mechanism for HXR in blood, and was of great significance in understanding the theory of HXR biotransformation and in discussing its clinical in vivo half-life.

Stabilizing proteins to prevent conformational changes required for amyloid fibril formation

Amyloid fibrillation is associated with several human maladies, such as Alzheimer's, Parkinson's, Huntington's diseases, prions, amyotrophic lateral sclerosis, and type 2 diabetes diseases. Gaining insights into the mechanism of amyloid fibril formation and exploring novel approaches to fibrillation inhibition are crucial for preventing amyloid diseases. Here, we hypothesized that ligands capable of stabilizing the native state of query proteins might prevent protein unfolding, which, in turn, may reduce the propensity of proteins to form amyloid fibrils. We demonstrated the efficient inhibition of amyloid formation of the human serum albumin (HSA) (up to 85%) and human insulin (up to 80%) by a nonsteroidal anti-inflammatory drug, ibuprofen (IBFN). IBFN significantly increases the conformational stability of both HSA and insulin, as confirmed by differential scanning calorimetry (DSC). Moreover, increasing concentration of IBFN boosts its amyloid inhibitory propensity in a linear fashion by influencing the nucleation phase as assayed by thioflavin T fluorescence, transmission electron microscopy, and dynamic light scattering. Furthermore, circular dichroism analysis supported the DSC results, showing that IBFN binds to the native state of proteins and almost completely prevents their tendency to lose secondary and tertiary structures. Cell toxicity assay confirms that species formed in the presence of IBFN are less toxic to neuronal cells (SH-SY5Y). These results demonstrate the feasibility of using a small molecule to stabilize the native state of proteins, thereby preventing the amyloidogenic conformational changes, which appear to be the common link in several human amyloid diseases.

Interaction of anticancer drug pinostrobin with lysozyme: a biophysical and molecular docking approach

Communicated by Ramaswamy H. Sarma.

Unveiling the stimulatory effects of tartrazine on human and bovine serum albumin fibrillogenesis: Spectroscopic and microscopic study

Amyloid fibrils are playing key role in the pathogenesis of various neurodegenerative diseases. Generally anionic molecules are known to induce amyloid fibril in several proteins. In this work, we have studied the effect of anionic food additive dye i.e., tartrazine (TZ) on the amyloid fibril formation of human serum albumins (HSA) and bovine serum albumin (BSA) at pHs7.4 and 3.5. We have employed various biophysical methods like, turbidity measurements, Rayleigh Light Scattering (RLS), Dynamic Light Scattering (DLS), intrinsic fluorescence, Congo red assay, far-UV CD, transmission electron microscopy (TEM) and atomic force microscopy (AFM) to decipher the mechanism of TZ-induce amyloid fibril formation in both the serum albumins at pHs7.4 and 3.5. The obtained results suggest that both the albumins forms amyloid-like aggregates in the presence of 1.0 to 15.0mM of TZ at pH3.5, but no amyloid fibril were seen at pH7.4. The possible cause of TZ-induced amyloid fibril formation is electrostatic and hydrophobic interaction because sulfate group of TZ may have interacted electrostatically with positively charged amino acids of the albumins at pH3.5 and increased protein-protein and protein-TZ interactions leading to amyloid fibril formation. The TEM, RLS and DLS results are suggesting that BSA forms bigger size amyloids compared to HSA, may be due to high surface hydrophobicity of BSA.

Multi-spectroscopic and molecular modeling approaches to elucidate the binding interaction between bovine serum albumin and darunavir, a HIV protease inhibitor

Darunavir (DRV), a second-generation HIV protease inhibitor, is widely used across the world as an important component of HIV therapy. The interaction of DRV with bovine serum albumin (BSA), a major carrier protein, has been studied under simulated physiological conditions (pH7.4) by multi-spectroscopic techniques in combination with molecular modeling. Fluorescence data revealed that the intrinsic fluorescence of BSA was quenched by DRV in terms of a static quenching procedure due to the formation of the DRV-BSA complex. The results indicated the presence of single weak affinity binding site (~10³M^-1, 310K) on protein. The thermodynamic parameters, namely enthalpy change (ΔH⁰), entropy change (ΔS⁰) and Gibbs free energy change (ΔG⁰) were calculated, which signified that the binding reaction was spontaneous, the main binding forces were hydrogen bonding and van der Waals forces. Importantly, competitive binding experiments with three site probes, phenylbutazone (in sub-domain IIA, site I), ibuprofen (in sub-domain IIIA, site II) and artemether (in the interface between sub-domain IIA and IIB, site II'), suggested that DRV was preferentially bound to the hydrophobic cavity in site II' of BSA, and this finding was validated by the docking results. Additionally, synchronous fluorescence, three-dimensional fluorescence and Resonance Rayleigh Scattering (RRS) spectroscopy gave qualitative information on the conformational changes of BSA upon adding DRV, while quantitative data were obtained with Fourier transform infrared spectroscopy (FT-IR).

Deciphering the role of the head group of cationic surfactants in their binding interactions with heme protein and their release by β-cyclodextrin

We decipher the mode of binding of surfactants with hemoglobin and their release by β-cyclodextrin.

Investigating the site selective binding of busulfan to human serum albumin: Biophysical and molecular docking approaches

We have studied the binding of busulfan (BN) to human serum albumin (HSA) at physiological pH 7.4 by using fluorescence, UV-vis and circular dichroism (CD) spectroscopic tools, as well as dynamic light scattering (DLS) measurements and molecular simulation approaches. HSA fluorescence quenching experiments showed that BN reduces the HSA native fluorescence intensity through the static mechanism. In addition, a single binding site on the HSA is occupied by BN with a binding constant at 298K of 1.84×10³M^-1. The enthalpy change (ΔH) and entropy change (ΔS) of BN-HSA interaction were calculated as -1.40kcalmol^-1 and +10.14calmol^-1K^-1 respectively, which suggest the possible interaction mode as hydrophobic and hydrogen bonding. Moreover, the secondary structure alteration of HSA following its complexation with BN was studied and showed that α-helical content of HSA gets increased on interacting with BN. Ligand binding site to HSA was further investigated by site-specific markers in fluorescence measurements as well molecular modeling approach which indicated that BN bind to the nearby sudlow site II of HSA through hydrophobic as well as hydrogen bonding interaction. The present study will be helpful for understanding the binding mechanism of BN to human serum albumin.

Spectrofluorimetric and molecular docking studies on the interaction of cyanidin-3-O-glucoside with whey protein, β-lactoglobulin

The interaction of β-Lactoglobulin (β-Lg) with cyanidin-3-O-glucoside (C3G) was characterized using fluorescence, circular dichroism spectroscopy, and docking studies under physiological conditions. Fluorescence studies showed that β-Lg has a strong binding affinity for C3G via hydrophobic interaction with the binding constant, K_a, of 3.14×10⁴M^-1 at 298K. The secondary structure of β-Lg displayed an increase in the major structure of β-sheet upon binding with C3G, whereas a decrease in the minor structure of α-helix was also observed. In addition, evidenced by near UV-CD, the interaction also disrupted the environments of Trp residues. The molecular docking results illustrated that both hydrogen bonding and the hydrophobic interaction are involved as an acting force during the binding process. These results may contribute to a better understanding over the enhanced physicochemical proprieties of anthocyanins due to the complexation with milk proteins.