Affinity For Bovine Serum Albumin Research Articles

Pentaerythritol-DOPA (PE-DOPA): A tetra-catechol derivative for versatile hydrophilic nanocoatings

Pentaerythritol (PE) was modified with 3,4-dihydroxy-L-phenylalanine (L-DOPA) to produce a tetra(catecholamine) tetra-ester derivative (PE-DOPA). Subsequently, PE-DOPA was used to dip-coat glass, stainless steel (SS) and various plastics under alkaline conditions and formed a poly(PE-DOPA) surface coating ranging in thickness between 1.0–3.0 nm on glass and 9.0–12.0 nm on SS, as estimated by X-ray photoelectron spectroscopy (XPS). The as-coated poly(PE-DOPA) showed increased hydrophilicity compared to the bare substrate, as demonstrated by water contact angle (WCA) measurements, whilst subsequent thermal annealing of poly(PE-DOPA) coatings on glass and SS at 120 °C for 6 h reversed the as-coated hydrophilicity through an indole ring formation reaction. The molecular structure of the poly(PE-DOPA) coating was investigated by adsorption studies, suggesting monolayer formation on glass and multilayer on SS. Surface modification of plastic substrates (e.g. Nylon, polyester, polyolefines, PTFE) was also confirmed at the molecular level by XPS and at bulk properties level by WCA. PTFE was the only plastic substrate that didn’t show any altering of its bulk hydrophilicity. Lastly, the fabrication of multilayer structures where poly(PE-DOPA) was coated by bovine serum albumin (BSA) allowed for a first assessment of poly(PE-DOPA) affinity for BSA and the associated possibility of tailoring poly(PE-DOPA) response.

Affinity Constants of Bovine Serum Albumin for 5 nm Gold Nanoparticles (AuNPs) with ω-Functionalized Thiol Monolayers Determined by Fluorescence Spectroscopy.

A detailed understanding of the binding of serum proteins to small (dcore <10 nm) nanoparticles (NPs) is essential for the mediation of protein corona formation in next generation nanotherapeutics. While a number of studies have investigated the details of protein adsorption on large functionalized NPs, small NPs (with a particle surface area comparable in size to the protein) have not received extensive study. This study determined the affinity constant (Ka) of BSA when binding to three different functionalized 5 nm gold nanoparticles (AuNPs). AuNPs were synthesized using three ω-functionalized thiols (mercaptoethoxy-ethoxy-ethanol (MEEE), mercaptohexanoic acid (MHA), and mercaptopentyltrimethylammonium chloride (MPTMA)), giving rise to particles with three different surface charges. The binding affinity of bovine serum albumin (BSA) to the different AuNP surfaces was investigated using UV-visible absorbance spectroscopy, dynamic light scattering (DLS), and fluorescence quenching titrations. Fluorescence titrations indicated that the affinity of BSA was actually highest for small AuNPs with a negative surface charge (MHA-AuNPs). Interestingly, the positively charged MPTMA-AuNPs showed the lowest Ka for BSA, indicating that electrostatic interactions are likely not the primary driving force in binding of BSA to these small AuNPs. Ka values at 25 °C for MHA, MEEE, and MPTMA-AuNPs were 5.2 ± 0.2 × 107, 3.7 ± 0.2 × 107, and 3.3 ± 0.16 × 107 M-1 in water, respectively. Fluorescence quenching titrations performed in 100 mM NaCl resulted in lower Ka values for the charged AuNPs, while the Ka value for the MEEE-AuNPs remained unchanged. Measurement of the hydrodynamic diameter (Dh) by dynamic light scattering (DLS) suggests that adsorption of 1-2 BSA molecules is sufficient to saturate the AuNP surface. DLS and negative-stain TEM images indicate that, despite the lower observed Ka values, the binding of MPTMA-AuNPs to BSA likely induces significant protein misfolding and may lead to extensive BSA aggregation at specific BSA:AuNP molar ratios.

An investigation of the binding of two cinnamate UV filters to bovine serum albumin separately and simultaneously

A study of the separate/simultaneous interaction mechanism between two common cinnamate ultraviolet filters (UVFs), Octtocrylene (OC) and 2-ethylhexyl 4-methoxycinnamate (EHMC), with bovine serum albumin (BSA) was conducted. Both OC and EM can bind to BSA. A more obvious fluorescence quenching effect was observed with EHMC on BSA, as well as a stronger affinity for BSA and a greater effect on the amino acid microenvironment. UVFs and BSA's binding constants were decreased when EHMC and OC interacted simultaneously with BSA, while the distance between UVFs and BSA was increased. Coexistence affected both OC and EHMC, making them less able to binding to BSA. While binding simultaneously to EHMC and OC, BSA's secondary structure underwent significant changes.

Ascorbic and salicylic acids modulate the binding interactions of an emergency contraceptive pill levonorgestrel to a model transport protein: Insights from spectroscopy and molecular docking analysis

Serum proteins generally help to transport and distribute drug molecules within the body. In this study, the binding characteristics of bovine serum albumin (BSA) with levonorgestrel (LVG), an emergency contraceptive pill, and the influences of ascorbic acid (ASC) and salicylic acid (SAL) on the binding behaviour and protein structure were elucidated using multi-spectroscopic techniques and molecular docking. The results showed that levonorgestrel decreased BSA intrinsic fluorescence via static quenching mechanism. Binding constant (Ka) values for BSA-LVG complexes were 103 to 104 M-1, indicating their high stabilities. Site probing/docking analysis indicated LVG bound between BSA subdomains IIA and IIIA. UV–visible absorption, Fourier Transform-Infrared and 3D fluorescence spectroscopies affirmed LVG-induced changes in BSA structure, especially in α-helix and β-sheet contents. ASC and SAL influenced BSA conformation for LVG binding and reduced the Ka values by 3.37 and 5.43-folds, respectively. LVG altered the microenvironments of tyrosine residues, interacted with Arg-217, Lys-221, Val-292, Glu-443 etc. within the binding domains. The process was spontaneous (ΔG<0), entropy driven (TΔS>ΔH) and involved van der Waals forces and hydrogen bonding. The findings of the study offered details on the binding interaction between BSA and LVG, and also indicated that prior intake of ASC or SAL could suppress the binding affinity of BSA for levonorgestrel.

Simultaneous binding characterization of different chromium speciation to serum albumin.

The binding process between three species of chromium and serum albumin (SA) was investigated, as well as the interaction between K2Cr2O7 and bovine serum albumin (BSA) under coexistence of different chromium forms. CrCl3, K2Cr2O7 and Crpic bound to SA spontaneously through Van der Waals force, and their binding constants were 103-104M-1 at 298K, respectively. K2Cr2O7 and Crpic both had strong binding affinity for BSA, and significantly affected the secondary structure of BSA and the microenvironment surrounding amino acid residues. Chromium exhibited a greater fluorescence quenching constant towards HSA than toward BSA, and K2Cr2O7 induced greater conformational changes in human serum albumin (HSA) than in BSA. A weak binding of CrCl3 to BSA had no significant effect on the binding affinity of K2Cr2O7 to BSA. K2Cr2O7 and BSA have a greater binding affinity when coexisting with Crpic, and K2Cr2O7 induces a greater conformational change in BSA.

Syntheses, structures, Hirshfeld surface analyses, BSA interactions and molecular docking studies of two leucine Schiff base complexes of oxovanadium(IV)

Two mixed-ligand oxovanadium(IV) complexes with a Schiff base derived from o-vanillin and leucine and 1,10-phenanthroline or 2,2´-bipyridine as a co-ligand, [VO(o-van-Leu)phen] (1) and [VO(o-van-Leu)bipy]·H2O (2), were prepared and structurally characterized by IR spectra, elemental analyses and single-crystal X-ray diffraction. The crystal structures reveal that each oxovanadium(IV) atom in complexes 1 and 2 is surrounded by a N3O3 coordination sphere to form a distorted octahedron with a Schiff base and neutral bidentate ligand phen or bipy. Hirshfeld surface analyses and 2D fingerprint plots indicated that the molecular packings in crystals were dominated by H···H, O···H/H···O, C···H/H···C and π-π interactions. The interactions of both complexes with bovine serum albumin (BSA) were studied by using various spectroscopic and molecular docking methods. BSA binding constants (K), estimated by UV–Vis spectroscopy, were 2.53 × 104M−1 for 1 and 3.18 × 104M−1 for 2, respectively. Together with results of fluorescence and CD spectral studies, it showed that complex 2 has a better affinity for BSA than complex 1. Molecular docking investigation indicated that the two complexes had the similar mode of binding and located within subdomain IIA of BSA. Complex 2 had greater binding activity with the binding free energy (∆Gbinding) of –6.5 kcal/mol than Complex 1 with ∆Gbinding of–5.42 kcal/mol, consisting with the analyses of spectroscopic experimental results.

In vitro BSA-binding, antimicrobial, and antitumor activity against human cancer cell lines of two lanthanide (III) complexes.

The investigation involved examining the binding of two lanthanide complexes, specifically those containing Holmium (Ho) and Dysprosium (Dy), with a ligand called 1, 10-phenanthroline (phen), and bovine serum albumin (BSA). The evaluation was carried out utilizing fluorescence measurements, Förster theory, and docking studies. The findings indicated that both the Ho-complex and Dy-complex possessed a significant ability to quench the emission of the protein. Furthermore, the primary mechanism of interaction was identified as a static process. The values indicate a strong tendency of these complexes for binding with BSA. The Kb values show the strangely high affinity of BSA to complexes and the following order for binding affinity: Ho-complex > Dy-complex. The thermodynamic parameters were found to be negative, affirming that the main forces driving the interaction between BSA and the lanthanide complexes are van der Waals engagement and hydrogen bonds. Additionally, the investigation included the examination of competition site markers, and molecular docking proposed that the engagement sites of the Ho-complex and Dy-complex with BSA were predominantly located in site 3 (specifically, subdomain IB). Moreover, the Ho-complex and Dy-complex were specifically chosen for their potential anticancer and antimicrobial properties. Consequently, these complexes could present promising prospects as novel candidates for anti-tumor and antibacterial applications.

Spectroscopic aspects on the interaction of nisin with serum albumin: thermodynamic and kinetic studies.

Nisin is a bacteriocin produced by Streptococcus and Lactococcus species and has antimicrobial activity against other bacteria. Nisin omits the need to use chemical preservatives in food due to its biological preserving properties. In the present in vitro study, we investigated nisin interaction with bovine serum albumin (BSA) using fluorescence spectroscopy and surface plasmon resonance (SPR) analysis to obtain information about the mechanisms of BSA complex formation with nisin. The BSA fluorescence intensity values gradually diminished with rising nisin concentration. The BSA fluorescence quenching analysis indicated that a combined quenching mechanism plays the main role. Finally, the Kb values were reduced with increasing temperature, which is demonstrative of nisin-BSA complex stability decrease at high temperatures. The negative values of ΔH° and ΔS° showed that hydrogen bonds and van der Waals forces are the foremost binding force between BSA and nisin. Meanwhile, the negative values of ΔG° demonstrated the exothermic and random nature of the reaction process. The results of the SPR verified the gained results through the fluorescence spectroscopy investigation, which denoted that the BSA affinity to nisin diminished upon increasing temperature. Overall, fluorescence spectroscopy and SPR results showed that the BSA interaction with nisin decreased with rising temperatures.

Effect of Cu2+ and Al3+ on the interaction of chlorogenic acid and caffeic acid with serum albumin

Despite the phenolic acids' health benefits, their interactions with proteins are still unclear. In this study, the interactions of Bovine Serum Albumin (BSA) with chlorogenic acid (CHA), caffeic acid (CA), and their Al3+, Cu2+ complexes were studied by using circular dichroism (CD) spectroscopy, fluorescence spectroscopy, and UV/Vis spectroscopy. It was found that esterification of carboxyl group of CA with quinic acid increased the binding affinities for BSA. After chelating with Cu2+ and Al3+, both CHA and CA exhibited high binding affinities for BSA. CHA could form CHA-Cu2 and CHA-Al2 complex with Cu2+ and Al3+. The result of CD spectroscopy demonstrated that the binding of CHA and Al3+ with BSA contributed to the folding of BSA secondary structure. In addition, with the presence of CHA, binding with Al3+ could also induce changes in BSA conformation. The binding sites of both CHA and CA were closed to Trp213.

Interaction mechanism of benzophenone-type UV filters on bovine serum albumin: Insights from structure-affinity relationship

Benzophenone (BP)-type UV filters can cause structural changes of carrier protein in plasma. The binding process of five BP-type UV filters with bovine serum albumin (BSA) was investigated by multiple characterization methods, along with their structure-affinity relationship involving the structure of the five BP-type UV filters and their binding affinity for BSA. The BP-type UV filters investigated bound to BSA spontaneously, and altered conformation of BSA. The binding constants and number of binding sites between BP-type UV filters and BSA were 103–106 M−1 and 0.82–1.26, respectively. These BP-type UV filters and BSA interacted with the same binding forces and went through the similar binding process, suggesting that the benzophenone skeleton structure was primarily responsible for the BP-type UV filters and BSA binding, and changes in the structure of the BSA. The BP-type UV filters with hydroxyl substituent (BP-1 and BP-9) and non-polar molecules (BP-6) had a high affinity for binding BSA and had a greater impact on BSA conformation.

Lophine-cinnamoyl hybrids: Synthesis, photophysical properties and a spectroscopic and molecular dynamics approach towards interactions with bovine serum albumin

Lophine and cinnamic acid derivatives have gained considerable attention due their chemical, biological and fluorescence emission properties. Herein we reported the synthesis of a new family of lophine-cinnamoyl hybrids connected by a methylene chain with two to nine carbon atoms. The hybrids show absorption in the ultraviolet and emission in the blue-violet region independent of the length of the alkyl chain spacer. Non-covalent interactions of the hybrids to bovine serum albumin (BSA) were investigated by UV–Vis absorption and fluorescence spectroscopy. Overall, the hybrids display moderate affinities for BSA (binding constants in the range 10–14 × 104 M−1) and can be effectively employed as protein probes using BSA as a model. The theoretical calculations showed preferential interactions of the hybrids with the binding pocket located near to Trp213 and the number of binding sites equal to 1 are in agreement with the experimental data obtained through the Stern-Volmer approach.

Binding and mechanistic studies of 5-HT7 specific benzothiazolone derivatives with bovine serum albumin: Spectroscopic and in silico studies

Serotonin, commonly known as 5-Hydroxytryptamine, or 5-HT, is a neurotransmitter having a single amine group and is distributed throughout the peripheral nervous system (PNS) and central nervous system (CNS).It is involved in a variety of physiological and behavioural disorders, including severe depression, pain, schizophrenia, obesity, anxiety, etc. Fourteen serotonin receptor (5-HTR) subtypes are known, among which the 5-HT1A/5-HT7 subtypes are the most studied. Agonists of the 5-HT1AR/5-HT7R have neuroprotective properties, whilst antagonists are helpful in the therapy of neurological diseases. Four (arylpiperazinyl-butyl) benzothiazolone (APBBT) derivatives, abbreviated as L1-L4, which are well established ligands for serotonin receptors. The protein–ligand interaction analysis was performed to determine the extent to which the synthesized APBBT derivatives bind to serum proteins for transport to the target organ.The binding affinity of bovine serum albumin (BSA) was evaluated using a computational technique. An enzyme activity assay specific for esterase confirmed its potential tobecome a new marker for 5-HT7. The quenching of fluorescence and details about the change in protein’s confirmation were provided by synchronous fluorescence spectroscopy. In this study, different spectroscopic methodologies were used, which included UV–visible spectroscopy, fluorescence spectroscopy, and circular dichroism (CD) spectroscopy. An enzymatic activity assay was done to assess the binding affinities of four (arylpiperazinyl-butyl)benzothiazolone derivatives with bovine serum albumin. Finally, molecular docking was used to deduce the primary intermolecular forces involved in the binding process between the synthesisedAPBBT derivatives and the BSA structure. On the basis of Glide score, ligand L3 was the most efficient for Sudlow Site I, followed by L1 > L2 > L4. All studies indicated the effective binding of serotonin derivatives with BSA, thus showing the role of BSA in the transport and metabolism of serotonin derivatives.

Temperature, pH and additives effects on the binding of Caffeic acid phenethyl ester to the native state of bovine serum albumin

Caffeic acid phenethyl ester (CAPE, phenethyl 3-(3,4-dihydroxyphenyl)acrylate), an important anti-tumor components of Beehive Propolis, has many pharmacological activities. The interaction of CAPE with bovine serum albumin (BSA) was thus investigated using UV-visible spectroscopy, fluorescence spectroscopy, circular dichroism (CD), dynamic light scattering (DLS), dynamic fluorescence spectrum and molecular docking under physiological conditions. The intrinsic fluorescence quenching of BSA by CAPE was a static process, confirmed by the dynamic Fluorescence Spectrum. The negative values of ΔHmo and ΔSmo indicated that the hydrogen bond and van der Walls force played a predominant role in the enthalpy-driven binding process. The CD spectrum showed that after adding CAPE, the α-helix content structure of BSA decreased, and the secondary structure changed. At pH 6.0 and 8.5, the binding affinity of BSA to CAPE decreased. After adding metal ions, the binding affinity of BSA and CAPE increased. However, the presence of biosurfactants [sodium cholate (NaC) and sodium deoxycholate (NaDC)] decreased the binding affinity of BSA to CAPE because they all bound in the same subdomain of BSA.

Behavior of molybdenum lowly doped SiO2–CaO–P2O5 composite interfacing a simulated biologic medium with serum albumin

This study is focussed on the biocompatibility evaluation by probing the affinity of bovine serum albumin (BSA) towards the surface of a silica based material containing CaMoO4 and hydroxyapatite nanocrystals. The adsorption occurring upon BSA interaction with the sample surface was investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The elemental composition and evaluation of protein surface coverage based on information from the outermost few nanometres surface layer was achieved by XPS analysis. The ratio between carbon and nitrogen on the material surface after incubation in BSA solution was found to be reasonable close to the value obtained from the measurement of pure BSA, that proves the protein adsorption. The comparative analysis of FTIR spectra recorded from lyophilized protein and from biomaterial surface after protein adsorption was considered in order to obtain information about the secondary structure of the proteins. The protein surface coverage was also confirmed by SEM morphological characterization. The results obtained by in vitro test indicate that the nanostructured SiO2–CaO–P2O5−MoO3 system has a great potential for bone tissue engineering with respect to the ability to bind to serum protein.

Low DNA and high BSA binding affinity of cationic ruthenium(II) organometallic featuring pyridine and 2’-hydroxychalcone ligands

The chiral-at-metal, piano-stool ruthenium(II) racemic organometallic [Ru(cymene)(chalconato)(pyridine)]PF6 was prepared by a multistep solution synthesis and its molecular and crystal structure was determined by single crystal X-ray diffraction. The compound crystallizes in a centrosymmetric triclinic P-1 space group with two molecules of opposite chirality within the asymmetric unit. Ruthenium is embedded in an octahedral half-sandwich coordination environment with four different donors, which generates the chirality of the metal centre. The formation of the organometallic was monitored ex-situ by infrared spectroscopy. The pyridine coordination to Ru(II) was particularly analysed to find its characteristic marker bands. The complex was also characterized by elemental analysis and NMR spectroscopy in solution. Its interaction with CT DNA and bovine serum albumin (BSA) was investigated by electron spectroscopy and spectrofluorimetry. The organometallic binds to DNA predominantly by electrostatic forces with low Kb value. On the contrary, its high affinity for BSA was confirmed by strong fluorescence quenching. The synchronous emission spectra revealed that the microenvironment of tryptophan is more affected compared to the environment of tyrosine.

Dopamine-Modified AuCu Bimetallic Nanoclusters as Charge Transfer-Based Biosensors for Highly Sensitive Glycine Detection.

Glycine is the simplest amino acid in living organisms and plays important roles in biology and medicine. However, few biosensors for glycine sensing have been reported. Herein, we present a facile strategy to construct dopamine-modified AuCu bimetallic nanoclusters (denoted as AuCu NC-DA) as charge transfer-based biosensors for highly sensitive glycine sensing. The AuCu NCs stabilized by bovine serum albumin (BSA) exhibited a fluorescence maximum at 400 nm. Because of the high affinity of BSA for dopamine (DA), the surface of the AuCu NCs was modified with DA without any complicated chemical reactions, resulting in fluorescence quenching through a charge transfer process. Among 20 amino acids, AuCu NC-DA exhibited an off/on fluorescence switching response specifically toward glycine through the formation of hydrogen bonds with oxidized DA, which inhibited the charge transfer process, leading to the emergence of a new emission peak at 475 nm. Spectroscopic and thermodynamic results combined with molecular docking analyses provided comprehensive understanding of the sensing mechanism. Furthermore, we showed that AuCu NC-DA was able to sense glycine in cells by imaging. Finally, the practicability of AuCu NC-DA for glycine detection was validated in milk drink samples. This study presents a promising type of a charge transfer-based sensor.

Facile Method to Prepare pH-Sensitive PEI-Functionalized Carbon Nanotubes as Rationally Designed Vehicles for Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) Delivery

A new pH-sensitive system designed for drug-delivery purposes and based on functionalized multiwall magnetic carbon nanotubes (Mag-CNTs) was synthesized for the effective incorporation of non-steroidal anti-inflammatory drugs (NSAIDs), aiming at drug release in characteristic acidic conditions close to the actual conditions of inflamed tissues. Cationic hyperbranched polyethyleneimine (PEI) was immobilized on the surface of Mag-CNTs via electrostatic interactions between the positively charged protonated amines within the polymer and the carboxyl groups on the chemically oxidized Mag-CNT surface. The addition of the NSAID with a carboxylate donor, Naproxen (NAP), was achieved by indirect coupling through the amino groups of the intermediate linker PEI. FT-IR, Raman, and UV–vis spectroscopy were employed to fully characterize the synthesized nanocarrier and its functionalization procedure. The interaction of the designed nanocarrier with bovine serum albumin (BSA) was studied in vitro by fluorescence emission spectroscopy while its in vitro interaction with calf-thymus (CT) DNA was monitored by UV–vis spectroscopy and viscosity measurements and via competitive studies with ethidium bromide. The calculated binding constants were compared to those of free NAP revealing a higher binding affinity for BSA and CT DNA. Finally, drug-release studies were performed, revealing that the electrostatic linkage ensures an effective release of the drug in the acidic pH typical of inflamed cells, while maintaining the multiwall nanotubes (MWNTs)–drug conjugates stable at the typical bloodstream.

Modulation of the binding affinity of naproxen to bovine serum albumin by conversion of the drug into amino acid ester salts

Naproxen (NAP) is one of the most widely prescribed non-steroidal anti-inflammatory drugs. Novel formulations of NAP aiming at better water-solubility, dosage, and the onset of action or new routes of application in order to minimize or prevent side effects of NAP are in the current interest of the pharmaceutical industry. Here, we report the synthesis, chemical, spectral and physicochemical characterization of a series of salts containing cations amino acid alkyl esters (AAE) and NAP anion, which potentially can be used as novel drug formulation. The [l-AAE][NAP] were obtained in three steps: preparation of the AAE hydrochlorides, neutralization of the hydrochlorides to the corresponding AAE, and formation of the target organic salts. All NAP derivatives, tested at a concentration as high as 100 μM, exhibited no toxicity against murine macrophage cell line (RAW 264.7). The binding parameters and stoichiometry of [AAE][NAP]s to bovine serum albumin (BSA) are in the range of that estimated for the parent NAP. Only l-valine isopropyl ester naproxenate characterizes with about one order of magnitude lower binding affinity for BSA, which suggests a faster diffusion rate in the circulatory system than the parent NAP and other derivatives, and therefore faster reach to the target system. Using molecular modeling seven binding pockets of BSA were probed for their suitability to binds the cation and the anion and results are discussed in correlation with the obtained thermodynamic parameters for the binding of NAP derivatives to BSA.

Synthesis, characterization, theoretical, molecular docking and in vitro biological activity studies of Ru(II) (η6 -p-cymene) complexes with novel aniline substituted aroyl selenoureas

A sequence of aroyl selenourea ligands (L1–L3) substituted by aniline and their Ru(II) (η6 -p-cymene) complexes (1-3), [Ru(II) (η6 -p-cymene) L] (L = monodentate aroyl selenourea ligand) have been synthesized and characterized the composition of the ligands and their metal complexes. The molecular structures of ligand L1 and complex 3 were also confirmed by single XRD crystal method. The single-crystal XRD study showed that aroyl selenourea ligand coordinates with Ru via Se novel neutral monodentate atom. In vitro DNA interaction studies were investigated by Fluorescence and UV-Visible spectroscopic methods which showed that the intercalative mode of binding is in the order of 1 > 2 > 3 with Ru(II) (η6 -p-cymene) complexes. Spectroscopic methods have been used for measuring the binding affinity of bovine serum albumin to complex. Moreover, the cytotoxic study of complexes (1–3) were evaluated against HeLa S3, A549, and IMR90 cells, resulting in complexes 1 and 2 showed promising cytotoxic activity against HeLa S3 cell with IC50 values of 24 and 26 µM, respectively. Also, the morphological changes of HeLa S3 and A549 cells were confirmed by fluorescence microscope in the presence of complexes 1 and 2 using AO (acridine orange, 200 µM) and EB (ethidium bromide, 100 µM). In addition, the docking results strongly support the protein binding studies of the complexes. Communicated by Ramaswamy H. Sarma

Formation and Stabilization of Gold Nanoparticles in Bovine Serum Albumin Solution.

The formation and growth of gold nanoparticles (AuNPs) were investigated in pH 7 buffer solution of bovine serum albumin (BSA) at room temperature. The processes were monitored by UV-Vis, circular dichroism, Raman and electron paramagnetic resonance (EPR) spectroscopies. TEM microscopy and dynamic light scattering (DLS) measurements were used to evidence changes in particle size during nanoparticle formation and growth. The formation of AuNPs at pH 7 in the absence of BSA was not observed, which proves that the albumin is involved in the first step of Au(III) reduction. Changes in the EPR spectral features of two spin probes, CAT16 and DIS3, with affinity for BSA and AuNPs, respectively, allowed us to monitor the particle growth and to demonstrate the protective role of BSA for AuNPs. The size of AuNPs formed in BSA solution increases slowly with time, resulting in nanoparticles of different morphologies, as revealed by TEM. Raman spectra of BSA indicate the interaction of albumin with AuNPs through sulfur-containing amino acid residues. This study shows that albumins act as both reducing agents and protective corona of AuNPs.