Complexes of Dendrimers with Bovine Serum Albumin

Sweet corn phytoglycogen dendrimers as a lyoprotectant for dry-state protein storage

Protein biotherapeutics typically require expensive cold-chain storage to maintain their fold and function. Packaging proteins in the dry state via lyophilization can reduce these cold-chain requirements. However, formulating proteins for lyophilization often requires extensive optimization of excipients that both maintain the protein folded state during freezing and drying (i.e., "cryoprotection" and "lyoprotection"), and form a cake to carry the dehydrated protein. Here we show that sweet corn phytoglycogens, which are glucose dendrimers, can act as both a protein lyoprotectant and a cake-forming agent. Phytoglycogen (PG) dendrimers from 16 different maize sources (PG1-16) were extracted via ethanol precipitation. PG size was generally consistent at ~70-100 nm for all variants, whereas the colloidal stability in water, protein contaminant level, and maximum density of cytocompatibility varied for PG1-16. 10 mg/mL PG1, 2, 9, 13, 15, and 16 maintained the activity of various proteins, including green fluorescent protein, lysozyme, β-galactosidase, and horseradish peroxidase, over a broad range of concentrations, through multiple rounds of lyophilization. PG13 was identified as the lead excipient candidate as it demonstrated narrow dispersity, colloidal stability in phosphate-buffered saline, low protein contaminants, and cytocompatibility up to 10 mg/mL in NIH3T3 cell cultures. All dry protein-PG13 mixtures had a cake-like appearance and all frozen protein-PG13 mixtures had a Tg' of ~ -26°C. The lyoprotection and cake-forming properties of PG13 were density-dependent, requiring a minimum density of 5 mg/mL for maximum activity. Collectively these data establish PG dendrimers as a new class of excipient to formulate proteins in the dry state.

Designing nanodiscs as versatile platforms for on-demand therapy

Nowadays, there has been an increasing utilization of nanomedicines for disease treatment. Nanodiscs (NDs) have emerged as a novel platform technology that garners significant attention in biomedical research and drug discovery. NDs are nanoscale phospholipid bilayer discs capable of incorporating membrane proteins and lipids within a native-like environment. They are assembled using amphiphilic biomacromolecular materials, such as apolipoprotein A1 or membrane scaffold proteins (MSPs), peptides, and styrene-maleic acid polymers (SMAs). NDs possess well-defined sizes and shapes, offering a stable, homogeneous, and biologically relevant environment for studying membrane proteins and lipids. Their unique properties have made them highly desirable for diverse applications, including cancer immunotherapy, vaccine development, antibacterial and antiviral therapy, and treating Alzheimer's disease (AD) and diabetes-related conditions. This review discusses the classifications, advantages, and applications of NDs in disease therapy.

Biophysical interactions of mixed lipid-polymer nanoparticles incorporating curcumin: Potential as antibacterial agent

The technology of lipid nanoparticles has a long history in drug delivery, which begins with the discovery of liposomes by Alec D Bangham in the 1960s. Since then, numerous studies have been conducted on these systems, and several nanomedicinal products that utilize them have entered the market, with the latest being the COVID-19 vaccines. Despite their success, many aspects of their biophysical behavior are still under investigation. At the same time, their combination with other classes of biomaterials to create more advanced platforms is a promising endeavor. Herein, we developed mixed lipid-polymer nanoparticles with incorporated curcumin as a drug delivery system for therapy, and we studied its interactions with various biosystems. Initially, the nanoparticle physicochemical properties were investigated, where their size, size distribution, surface charge, morphology, drug incorporation and stability were assessed. The incorporation of the drug molecule was approximately 99.8 % for a formulated amount of 10 % by weight of the total membrane components and stable in due time. The association of the nanoparticles with human serum albumin and the effect that this brings upon their properties was studied by several biophysical techniques, including light scattering, thermal analysis and circular dichroism. As a biocompatibility assessment, interactions with erythrocyte membranes and hemolysis induced by the nanoparticles were also studied, with empty nanoparticles being more toxic than drug-loaded ones at high concentrations. Finally, interactions with bacterial membrane proteins of Staphylococcus aureus and the antibacterial effect of the nanoparticles were evaluated, where the effect of curcumin was improved when incorporated inside the nanoparticles. Overall, the developed mixed nanoparticles are promising candidates for the delivery of curcumin to infectious and other types of diseases.

Aminoglycoside antibiotic kanamycin functionalized tetraphenylethylene molecular probe for highly selective detection of bovine serum albumin protein

A novel tetraphenylethylene (TPE) functionalized aminoglycoside antibiotic kanamycin (TPE-kana 1) has been successfully synthesized and characterized by means of modern analytical and spectroscopic techniques. The probe TPE-kana 1 showed strong affinity towards bovine serum albumin (BSA) compared to its other biological competitors. The recognition of BSA have been investigated employing UV–Vis absorption and fluorescence emission spectroscopy. The significant color change of TPE-kana 1 with BSA can be observed by necked eye, where the role of AIE-active TPE molecule is handle in both optical and colorimetric changes. The quenching of fluorescence of TPE-kana 1 with BSA was characterized by fluorescence spectroscopy, with 71.16% of quenching efficiency. Moreover, the Stern–Volmer quenching constant was calculated and found to be 2.46 × 10⁷ M⁻¹. Probe TPE-kana 1 showed detection limit of 2.87 nM (nM) towards BSA with binding constant 7.56 × 10⁷ M. A molecular docking study is also performed to investigate the detail interactions between TPE-kana 1 with the sites of BSA via non-covalent i.e., H-bonding, π-cation interactions, π-donor hydrogen bonds and π-π interactions. The lowest binding energy conformation was found at − 10.42 kcal/mol.

Refolding of denatured gold nanoparticles-conjugated bovine serum albumin through formation of catanions between gemini surfactant and sodium dodecyl sulphate

The present work elucidates binding interactions of sodium dodecyl sulphate (SDS) with the conjugated gold nanoparticles (AuNPs)-bovine serum albumin (BSA), unfolded by each of two gemini surfactants, 1,4-bis(dodecyl-N,N-dimethylammonium bromide)-butane (12-4-12,2Br-) or 1,8-bis(dodecyl-N,N-dimethylammonium bromide)-octane (12-8-12,2Br-). Initially, at a low concentration of SDS there is a relaxation of bioconjugates from their compressed form due to the formation of catanions between SDS and gemini surfactants. On moving towards higher concentrations of SDS, these relaxed unfolded bioconjugates renature by removal of residual bound gemini surfactants. Mixed assemblies of SDS and gemini surfactants formed during refolding of bioconjugates are characterized by DLS and FESEM measurements. A step-by-step process of refolding observed for these denatured protein bioconjugates is exactly the inverse of their unfolding phenomenon. Parameters concerning nanometal surface energy transfer (NSET) and Förster's resonance energy transfer (FRET) phenomenon were employed to develop a binding isotherm. Moreover, there remains an inverse relationship between α-helix and β-turns of bioconjugates during the refolding process. Significantly, in the presence of 12-8-12,2Br-, SDS induces more refolding as compared to that for 12-4-12,2Br-. Bioconjugation shows an effect on the secondary structures of refolded BSA, which has been explored in detail through various studies such as Fourier transform infrared spectroscopy, fluorescence, and circular dichroism (CD). Therefore, this approach vividly describes the refolding of denatured bioconjugates, exploring structural information regarding various catanions formed during the process that would help in understanding distance-dependent optical biomolecular detection methodologies and physicochemical properties.

Dendrimers as Antiamyloid Agents

Dendrimer-protein conjugates have significant prospects for biological applications. The complexation changes the biophysical behavior of both proteins and dendrimers. The dendrimers could influence the secondary structure of proteins, zeta-potential, distribution of charged regions on the surface, the protein-protein interactions, etc. These changes offer significant possibilities for the application of these features in nanotheranostics and biomedicine. Based on the dendrimer-protein interactions, several therapeutic applications of dendrimers have emerged. Thus, the formation of stable complexes retains the disordered proteins on the aggregation, which is especially important in neurodegenerative diseases. To clarify the origin of these properties and assess the efficiency of action, the mechanism of protein-dendrimer interaction and the nature and driving force of binding are considered in this review. The review outlines the antiamyloid activity of dendrimers and discusses the effect of dendrimer structures and external factors on their antiamyloid properties.

Investigating the binding mechanism of topiramate with bovine serum albumin using spectroscopic and computational methods

Various spectroscopic techniques involving fluorescence spectroscopy, circular dichroism (CD), and computational approaches were used to elucidate the molecular aspects of interaction between the antiepileptic drug topiramate and the multifunctional transport protein bovine serum albumin (BSA) under physiological conditions. Topiramate quenched BSA fluorescence in a static quenching mode, according to the Stern-Volmer quenching constant (K_sv ) data derived from fluorescence spectroscopy for the topiramate-BSA complex. The binding constant was also used to calculate the binding affinity for the topiramate-BSA interaction. Fluorescence and circular dichroism experiments demonstrate that the protein's tertiary structure is affected by the microenvironmental alterations generated by topiramate binding to BSA. To establish the exact binding site, interacting residues, and interaction forces involved in the binding of topiramate to BSA, molecular modeling and simulation approaches were used. According to the MMPBSA calculations, the average binding energy between topiramate and BSA is -421.05 kJ/mol. Topiramate was discovered to have substantial interactions with BSA, changing the structural dynamic and Gibbs free energy landscape patterns.

Doxorubicin-NO Releaser Molecular Hybrid Activatable by Green Light to Overcome Resistance in Breast Cancer Cells

The biological activity of a molecular hybrid (DXNO-GR) joining doxorubicin (DOX) and an N-nitroso moiety releasing nitric oxide (NO) under irradiation with the biocompatible green light has been investigated against DOX-sensitive (MCF7) and -resistant (MDA-MB-231) breast cancer cells in vitro. DXNO-GR shows significantly higher cellular internalization than DOX in both cell lines and, in contrast to DOX, does not experience cell efflux in MDR overexpressing MDA-MB-231 cells. The higher cellular internalization of the DXNO-GR hybrid seems to be mediated by bovine serum albumin (BSA) as a suitable carrier among serum proteins, according to the high binding constant measured for DXNO-GR, which is more than one order of magnitude larger than that reported for DOX. Despite the higher cellular accumulation, DXNO-GR is not toxic in the dark but induces remarkable cell death following photoactivation with green light. This lack of dark toxicity is strictly related to the different cellular compartmentalization of the molecular hybrid that, different from DOX, does not localize in the nucleus but is mainly confined in the Golgi apparatus and endoplasmic reticulum and therefore does not act as a DNA intercalator. The photochemical properties of the hybrid are not affected by binding to BSA as demonstrated by the direct detection of NO photorelease, suggesting that the reduction of cell viability observed under light irradiation is a combined effect of DOX phototoxicity and NO release which, ultimately, inhibits MDR1 efflux pump in DOX-resistant cells.

Sensitive detection of SARS-CoV-2 spike protein using vertically-oriented silicon nanowire array-based biosensor

The COVID-19 pandemic has caused tremendous damage to the world. In order to quickly and accurately diagnose the virus and contain the spread, there is a need for rapid, sensitive, accurate, and cost-effective SARS-CoV-2 biosensors. In this paper, we report on a novel biosensor based on angiotensin converting enzyme 2 (ACE-2)-conjugated vertically-oriented silicon nanowire (vSiNW) arrays that can detect the SARS-CoV-2 spike protein with high sensitivity and selectivity relative to negative controls. First, we demonstrate the efficacy of using ACE-2 receptor to detect the SARS-CoV-2 spike protein via a capture assay test, which confirms high specificity of ACE-2 against the mock protein, and high affinity between the spike and ACE-2. We then report on results for ACE-2-conjugated vSiNW arrays where the biosensor device architecture is based on a p-n junction transducer. We confirm via analytical modeling that the transduction mechanism of the biosensor involves induced surface charge depletion of the vSiNWs due to negative electrostatic surface potential induced by the spike protein after binding with ACE-2. This vSiNW surface charge modulation is measured via current-voltage characteristics of the functionalized biosensor. Calibrated concentration dependent electrical response of the vSiNW sensor confirms the limit-of-detection for virus spike concentration of 100 ng/ml (or 575 pM). The vSiNW sensor also exhibits highly specific response to the spike protein with respect to negative controls, offering a promising point-of-care detection method for SARS-CoV-2.

Anticancer nano-delivery systems based on bovine serum albumin nanoparticles: A critical review

Among the health-promotional protein-based vehicles, bovine serum albumin nanoparticles (BSA NPs) are particularly interesting. Meeting requirements e. g., non-toxicity, non-immunogenicity, biodegradability, biocompatibility, and high drug-binding capacity, has introduced BSA NPs as a promising candidate for efficient anti-cancer drug delivery and its application is now a rapidly-growing strategy to promote cancer therapy. Nevertheless, the leverage of such carriers requires an in-depth understanding of structural/physicochemical features of the BSA molecule and its derived nanovehicles, together with the utilized nano-formulation approaches, effective variables in delivery mechanism, specific shortfalls, and recent nanoencapsulation progresses. The current review highlights the novel advances in the application of BSA NPs to engineer drug vehicles for delivering anti-cancer agents. The factors influencing the efficiency of the therapeutics in such nano-delivery systems, alongside their advantaged and limitations are also discussed.

Binding interactions of cationic gemini surfactants with gold nanoparticles-conjugated bovine serum albumin: A FRET/NSET, spectroscopic, and docking study

This work demonstrates binding interactions of two cationic gemini surfactants, 12-4-12,2Br^- and 12-8-12,2Br^- with gold nanoparticles (AuNPs)-conjugated bovine serum albumin (BSA) presenting binding isotherms from specific binding to saturation binding regions of surfactants. The binding isotherm has been successfully constructed using Förster's resonance energy transfer (FRET) and nanometal surface energy transfer (NSET) parameters calculated based on fluorescence quenching of donor, tryptophan (Trp) residue by acceptor, AuNP. Energy transfer efficiency (E_T) changes due to alteration in the donor-acceptor distance when surfactants interact with bioconjugates. A solid reverse relationship between α-helix and β-turn contents of BSA-AuNPs-conjugates is noted while interacting with surfactants. 12-8-12,2Br^- shows stronger binding interactions with BSA-bioconjugates than 12-4-12,2Br^-. The effect of bioconjugation on secondary/tertiary structures of BSA in the absence and presence of a surfactant is studied through circular dichroism, fluorescence, and Fourier transform infrared spectroscopic measurements. Motional restrictions imposed by AuNPs on Trp residues of folded and unfolded BSA have been investigated using red edge emission shift (REES) measurements. Finally, the molecular docking results present the modes of interactions of 12-4-12,2Br^- and 12-8-12,2Br^-, and Au-nanoclusters (Au₉₂) with BSA. An approach to describe the binding isotherms of surfactants using AuNPs-bioconjugates as optical-based molecular ruler and possible effects of AuNPs on microenvironment and conformations of the protein is presented.

Synthesis of Murrayaquinone-A Derivatives and Investigation of Potential Anticancer Properties

A series of novel murrayaquinone a derivatives were synthesized and their anti-cancer activity were evaluated on healthy colon cell lines (CCD-18Co), primary (Caco-2) and metastatic (DLD-1) colon cancer cell lines. The results showed that the cytotoxicity of murrayaquinone molecules is significantly high even in micromolar levels. The DNA binding, cell cycle arrest and metabolic activity studies of these molecules were also carried out and the results showed that these molecules induce apoptosis. In conclusion, the data support further studies on murrayaquinone derivatives toward selection of a candidate for cancer treatment.

Molecular Basis of Interactions between the Antibiotic Nitrofurantoin and Human Serum Albumin: A Mechanism for the Rapid Drug Blood Transportation

Nitrofurantoin is an antimicrobial agent obtained through the addition of a nitro group and a side chain containing hydantoin to a furan ring. The interactions of the antibiotic with human serum albumin (HSA) have been investigated by fluorescence, UV-VIS, Fourier transform infrared spectroscopy (FTIR) spectroscopy, and protein-ligand docking studies. The fluorescence studies indicate that the binding site of the additive involves modifications of the environment around Trp214 at the level of subdomain IIA. Fluorescence and UV-VIS spectroscopy, displacement studies, and FTIR experiments show the association mode of nitrofurantoin to HSA, suggesting that the primary binding site of the antibiotic is located in Sudlow’s site I. Molecular modeling suggests that nitrofurantoin is involved in the formation of hydrogen bonds with Trp214, Arg218, and Ser454, and is located in the hydrophobic cavity of subdomain IIA. Moreover, the curve-fitting results of the infrared Amide I’ band indicate that the binding of nitrofurantoin induces little change in the protein secondary structure. Overall, these data clarify the blood transportation process of nitrofurantoin and its rapid transfer to the kidney for its elimination, hence leading to a better understanding of its biological effects and being able to design other molecules, based on nitrofurantoin, with a higher biological potential.

Selective anions mediated fluorescence "turn-on", aggregation induced emission (AIE) and lysozyme targeting properties of pyrene-naphthalene sulphonyl conjugate

We have designed and synthesized a novel pyrene-naphthalene sulphonyl conjugate, 1-((1Z)-(4-((Z)-4-(pyrene-1-yl)methyleneamino)phenylsulfonyl)phenylimino)methyl)naphthalene-2-ol (PSN) through a facile two-step reactions. It was characterized by various spectral techniques. Fluorescence spectral studies showed that compound PSN featured fluorescence enhancement upon increasing the water content in THF. This can be attributed to the phenomena of aggregated induced emission (AIE), which is confirmed by SEM and AFM studies, due to the restriction of CHN isomerization of PSN. The anion sensing of PSN was examined with various anions. Among these anions, H₂PO₄^- and F^- ions were selectively sensing with a low detection limit of 3.52 × 10^-7 M and 7.23 × 10^-7 M, respectively, and an obvious color change from yellow to orange was observed by the naked eye. The mechanism of sensing involved the formation of hydrogen bonding interaction between O-H group of PSN and H₂PO₄^-/ F^- ions. The binding of PSN with LYZ was also examined by docking studies, which shows that H-bonding and hydrophobic interactions play crucial roles for the interaction of LYZ toward PSN.

Nano-scale selective and sensitive optical sensor for metronidazole based on fluorescence quenching: 1H-Phenanthro[9,10-d]imidazolyl-calix[4]arene fluorescent probe

It is crucial to determine and control the metronidazole (MET) ingredient in food and pharmaceuticals for human health and food safety. Even though many sensors have been previously reported to detect MET, there is still a need for a highly selective and sensitive, easy, fast, cost-effective sensor in this area. Herein, we report a fluorescent calix[4]arene derivative (PIMC) for highly selective and sensitive and facile and rapid MET detection based on fluorescence (FL) quenching. The highest FL quenching occurs when PIMC is exposed to MET solution at 400 nm (λ_ex = 340). Owing to the quenching efficacy of MET linearly up to 5.5 × 10⁴ nM was obtained a detection limit of 2.44 nM. Besides, interferences of other pharmaceuticals and ions on probe performance were investigated. The FL probe was successful in MET detection without the assistance of any separation techniques in a pharmaceutical sample (tablet) with an acceptable recovery of 101.3%. The applicability of the current probe as a paper-based sensor to MET detection has been successfully tested. As a result, the proposed probe presents a fast and suitable strategy to sensitive and selective detect MET and proves a good potential for practical applications, especially pharmaceutical preparations.

Analysis of dendrimer-protein interactions and their implications on potential applications of dendrimers in nanomedicine

This work addresses how G5.5 PAMAM dendrimers form complexes with bovine serum albumin (BSA). Analytical techniques, such as UV-vis spectrophotometry, dynamic light scattering, electrophoretic mobility, quartz crystal microbalance with dissipation monitoring (QCM-D), circular dichroism (CD), and contact angle were used to analyze the properties of the dendrimers systems. The binding of protein to dendrimers can alter the structure, mobility, conformation and functional activity of the dendrimer. The results show that BSA interactions with G5.5 dendrimer carriers are driven both by electrostatic and hydrophobic forces. Dendrimer surface charge is reduced upon contact with the protein. The protein shell formed on the surface of the carrier is very stable as evidenced by the QCM-D measurements. On the other hand, the CD spectra indicates a change in the secondary structure of the protein. The size of the changes is significantly dependent on the ratio of protein to dendrimer. Understanding the mechanism of interaction of potential carriers with proteins is important for their internalization into the cell.

Preparation and Characterization of Soy Isoflavones Nanoparticles Using Polymerized Goat Milk Whey Protein as Wall Material

Soy isoflavones (SIF) are a group of polyphenolic compounds with health benefits. However, application of SIF in functional foods is limited due to its poor aqueous solubility. SIF nanoparticles with different concentrations were prepared using polymerized goat milk whey protein (PGWP) as wall material. The goat milk whey protein was prepared from raw milk by membrane processing technology. The encapsulation efficiencies of all the nanoparticles were found to be greater than 70%. The nanoparticles showed larger particle size and lower zeta potential compared with the PGWP. Fourier Transform Infrared Spectroscopy indicated that the secondary structure of goat milk whey protein was changed after interacting with SIF, with transformation of α-helix and β-sheet to disordered structures. Fluorescence data indicated that interactions between SIF and PGWP decreased the fluorescence intensity. All nanoparticles had spherical microstructure revealed by Transmission Electron Microscope. Data indicated that PGWP may be a good carrier material for the delivery of SIF to improve its applications in functional foods.

Binding of levobupivacaine-loaded gold nanoparticles to human serum albumin: a simulated physiological study

Techniques such as Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) spectra, fluorescence, circular dichroism (CD) and spectroscopy were applied to elucidate the formation, structure and physicochemical properties of levobupivacaine-gold nanoparticle (LGN) binding to human serum albumin (HSA). Thermodynamic parameters (ΔG = -2.58 × 10⁴ J·mol^-1 , ΔS = -7.80 J·mol^-1 ·K^-1 , and ΔS = -2.82 × 10⁴ J·mol^-1 at 305 K) suggested one weak binding site on HSA, which was governed by van der Waals forces as well as hydrogen bonds. Moreover, the outcomes of UV-vis, CD, FTIR, synchronous and three-dimensional fluorescence suggested that the microenvironment of HSA had been changed with addition of LGN. Based on the results of fluorescence resonance energy transfer, a distance of 2.8 nm between the LGN and HSA was observed. This approach has potential value for illustrating the pharmacodynamics of LGN when in combination with transmembrane transport, biomolecular function effect, and other experiments.

Poly(propylene imine) dendrimers can bind to PEGylated albumin at PEG and albumin surface: Biophysical examination of a PEGylated platform to transport cationic dendritic nanoparticles

Cationic dendrimers are considered one of the best drug transporters in the body. However, in order to improve their biocompatibility, modification of them is required to reduce toxicity. In this way, many dendrimers may lose their original properties, for example, anticancer. To improve biocompatibility of dendrimers, it is possible to complex them with albumin, as is done very often in drug delivery. However, the interaction of dendrimers with albumin can lead to protein structure disruption or no complexation at all. Therefore, the investigation of the interaction between cationic poly-(propylene imine) dendrimers and polyethylene glycol (PEG)-albumin by fluorescence, circular dichroism, small angle X-ray scattering (SAXS), and transmission electron microscopy was carried out. Results show that cationic dendrimers bind to PEGylated albumin at PEG and albumin surfaces. The obtained results for 5k-PEG indicate a preferential binding of the dendrimers to PEG. For 20k-PEG binding of dendrimers to PEG and protein could induce a collapse of the PEG chain onto the protein surface. This opens up new possibilities to the use of PEGylated albumin as a platform to carry dendrimers without changing the albumin structure and improve the pharmacokinetic properties of dendrimers without further modification.

In vitro toxicity and molecular interacting mechanisms of chloroacetic acid to catalase

Chloroacetic acid (CAA), one of typical disinfection by-products (DBPs), has attracted considerable concerns for its biological safety. Antioxidant enzyme catalase (CAT) plays a crucial part in the regulation of redox state balance. Herein, CAA was used to test its adverse effects on CAT and explore the underlying mechanism. The cell viability of mouse primary hepatocytes decreased under CAA exposure. A bell-shaped response to CAA exposure was observed in intracellular CAT activity, whose change was partly influenced by molecular CAT activity. CAA binds to CAT mainly via van der Waals forces and hydrogen bonds with a stoichiometry of 9.2. The binding caused structural changes in CAT with the unfolding of polypeptide chains and the decrease of α-helical content. CAA interacts with the amino acid residues surrounding the active sites and substrate channel of CAT. These interactions result in the decrease of molecular CAT activity, which could be restored by high ionic strength. This study has provided a combined molecular and cellular tactics for studying the adverse effects of DBPs on biomarkers and the underlying mechanisms.

Covalent Functionalization of Bovine Serum Albumin with Graphene Quantum Dots for Stereospecific Molecular Recognition

Stereospecific molecular recognition with simple and easily available proteins is of significant importance in life science and biomaterial science. Herein, we report on a chiral sensing platform, graphene quantum dots (GQDs)-functionalized bovine serum albumin (BSA), for chiral recognition of tryptophan (Trp) isomers. Amidation reaction between BSA and GQDs was directly responsible for the introduction of GQDs to BSA, resulting in significant changes in the spatial configuration of BSA and the exposure of more chiral sites at the protein surface. The BSA-GQDs-based chiral sensor exhibited good biomolecular homochirality in the recognition of Trp isomers, and the higher affinity of BSA-GQDs toward l-Trp than its isomer, d-Trp, was also revealed by density functional theory (DFT) considering the possible hydrogen bonds between the Trp isomers and the solvent-accessible residues of BSA.

Biodegradable cross-linked chitosan nanoparticles improve anti-Candida and anti-biofilm activity of TistH, a peptide identified in the venom gland of the Tityus stigmurus scorpion

Among several bioactive peptides identified from the venom glands of the Tityus stigmurus scorpion, one peptide with hypotensive action (TistH, Tityus stigmurus Hypotensin) showed multifunctional and biotechnological applications. The maximum efficacy of this class of compounds can be achieved by immobilizing it in specific and suitable biomaterials or suitable carriers. In this study, distinct entrapment methods of TistH in chitosan nanoparticles was tested using its incorporation (CN-TistH-Inc) or adsorption (CN-TistH-Ads) methods by ionotropic gelification. Physico-chemical properties as well as biocompatibility and antifungal efficacy were assessed for different samples. Atomic force microscopy and field emission gun scanning electronic microscopy images associated with particle size measurements demonstrated that the two methods induced cationic spherical, small (< 160 nm), and narrow-sized (PdI about 0.3) nanoparticles, even after peptide loading greater than 96.5%, which was confirmed using Fourier transform infrared spectroscopy. The colloidal suspensions showed to be stable for 8 weeks and were able to induce the desired slow in vitro peptide release. Cytotoxicity assays performed in normal cells originated from murine macrophages (RAW 264.7) and kidneys of African green monkeys (Vero E6) suggested biocompatibility of samples. The CN-TistH-Inc and CN-TistH-Ads showed a minimal inhibitory concentration of 89.2 μg.mL^-1 against Candida albicans, 11.1 μg.mL^-1 for C. parapsilosis and C. tropicalis, confirmed by minimum fungicidal concentrations assay. Moreover, the TistH-loaded cross-linked chitosan nanoparticles significantly reduced the biofilm formation of clinical yeast sepsis of C. tropicalis and C. krusei, as well as clinical yeasts of vulvovaginal candidiasis of C. albicans. In this approach, biodegradable nanocarriers prepared using simple and reproducible methods demonstrated the ability to deliver the TistH peptide from T. stigmurus and improve its antifungal efficacy.

Photodegradable coumarin-derived amphiphilic dendrons for DNA binding: Self-assembly and phototriggered disassembly in water and air-water interface

In this article, we demonstrate the self-assembly and photoresponive behavior of a novel coumarin-based amphiphilic dendron in both aqueous solution and air-water interface. The dendritic structure, namely C-IG₁, was composed of a lipophilic cholesterol and hydrophilic poly(amido amine) (PAMAM) dendron, and the amphiphilic counterpart is interconnected by a photolabile coumarin carbonate ester, enabling the photoinduced degradation of the amphiphiles in protic solvents via S_N1-like mechanism. A Nile red solubilization fluorescence assay suggests a low critical aggregation concentration for the micelle formation of C-IG₁ in aqueous solutions (3.9 × 10^-5 M); the Langmuir analysis further indicates that C-IG₁ possesses significant compressibility in air-water interface, eventually forming homogeneous monolayers with a final molecular area (A₀) of 36 Ų. Notably, the micelles and Langmuir monolayer are quite stable until photo-triggered dissociation based on the photocleavage of C-IG₁ amphiphile activated by 365-nm incident light. Moreover, the transition in interfacial morphology of the Langmuir monolayer during the assembly and photodegradation processes also can be visually analyzed by incorporating Nile red probes with in situ monitoring through fluorescence microscopy. The thin film deposited on a glass substrate by the Langmuir-Blodgett technique also shows a photoresponsive behavior based on the change in the contact angles of a water droplet on the surface upon light stimulation. The binding affinity of C-IG₁ and cyclic DNA determined by the fluorescence quenching analysis of the coumarin reporter suggests a ground-state macromolecular complexation process occurring through polyvalent interactions between the pseudodendrimers and biomacromolecules. The ethidium bromide displacement assay further indicates thus dendriplex formation at low nitrogen-to-phosphorous value (N/P < 1) and confirms that the decomplexation accompanied by DNA release can be achieved through an active phototriggered route under spatiotemporal control.

Urea-based porous organic polymer/graphene oxide hybrid as a new sorbent for highly efficient extraction of bovine serum albumin prior to its spectrophotometric determination

A 3D urea-based porous organic polymer (Urea-POP) was prepared via the reaction of tetrakis(4-aminophenyl)methane and 1,4-Phenylene diisocyanate. The polymer was subsequently reacted with 2D layered nanosheets of graphene oxide (GO) to prepare Urea-POP/GO as a novel and highly efficient sorbent for pre-concentration and extraction of serum albumin samples, prior to spectrophotometric determination. The hybrid material combines advantages of both POP and GO such as hydrophilicity, high dispersion stability, porosity, and having a large number of nitrogen- and oxygen-containing functional groups. Parameters which influence the extraction efficiency such as the amount of the adsorbent, pH of sample solution, ionic strength, adsorption and desorption time were investigated and optimized. For the method, detection limit of 0.068 mg L^-1 and determination coefficient (R²) of 0.9991 were obtained. The intra- and inter-day was calculated with five replicates in the same day and seven consecutive days, respectively. Intra-day and inter-day precisions were 1.7% and 5.9%, respectively. The maximum sorption capacity was 357.1 mg g^-1, which is higher than the other reported sorbents. The proposed method was demonstrated to be sensitive enough for determination of serum albumin from bio-samples.

A biotechnological approach to immunotherapy: Antivenom against Crotalus durissus cascavella snake venom produced from biodegradable nanoparticles

Snakebite envenoming is a tropical disease neglected worldwide. In Brazil, the Crotalus durissus cascavella (CDC) snake belongs to a genus with venom of highest lethality. A search for new immunoadjuvants aimed to expand the therapeutic alternatives to improve vaccines and antivenom. This approach proposed to produce small and narrow-sized cationic CDC venom-loaded chitosan nanoparticles (CHNP) able to induce antibody response against the CDC venom. The ionic gelation method induced the formation of stable and slightly smooth spherical nanoparticles (<160 nm) with protein loading efficiency superior to 90%. The interactions between venom proteins and CHNP assessed using FT-IR spectroscopy corroborated with the in vitro release behavior of proteins from nanoparticles. Finally, the immunization animal model using BALB/c mice demonstrated the higher effectiveness of CDC venom-loaded CHNP compared to aluminum hydroxide, a conventional immunoadjuvant. Thus, CHNPs loaded with CDC venom exhibited a promising biotechnological approach to immunotherapy.

Impact of the alkyl chain length on binding of imidazolium-based ionic liquids to bovine serum albumin

The effects of six imidazolium-based ionic liquids (ILs) with different alkyl chain length ([C_nMim]Cl, n=2, 4, 6, 8, 10, 12) on the structure and functions of bovine serum albumin (BSA) were studied by multi-spectral methods and molecular docking. ILs with the longer alkyl chain length have the stronger binding interaction with BSA and the greater conformational damage to protein. The effects of ILs on the functional properties of BSA were further studied by the determination of non-enzyme esterase activity, β-fibrosis and other properties of BSA. The thermal stability of BSA was reduced, the rate of the formation of beta sheet structures of BSA was lowered, and the esterase-like activity of BSA were decreased with the increase of ILs concentration. Simultaneous molecular modeling technique revealed the favorable binding sites of ILs on protein. The hydrophobic force and polar interactions were the mainly binding forces of them. The calculated results are in a good agreement with the spectroscopic experiments. These studies on the impact of the alkyl chain length on binding of imidazolium-based ionic liquids to BSA are of great significance for understanding and developing the application of ionic liquid in life and physiological system.

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

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

A highly fluorescent turn-on probe in the near-infrared region for albumin quantification in serum matrix

A commercially available styryl based fluorophore in the near-IR region shows exceptional turn-on emission for serum albumins.

Hematological Effects of Gold Nanorods on Erythrocytes: Hemolysis and Hemoglobin Conformational and Functional Changes

Gold nanorods (GNRs) are a unique class of metal nanostructures that have attractive potentials in biomedical applications, and the concern on their biological safety is concomitantly increasing. Hemocompatibility is extremely important as their contact with blood circulation is unavoidable during in vivo delivery. Herein, two kinds of GNRs coated with hexadecyltrimethylammonium bromide (C-GNRs) or poly(sodium-p-styrenesulfonate) are used to test their potential toxicological effects in blood. C-GNRs with positive surface charges efficiently induce hemolysis when encountering erythrocytes. Cellular internalization of C-GNRs is found, and they subsequently bind with hemoglobin, forming bioconjugates. The interaction between hemoglobin and C-GNR (stoichiometry 32.7:1) is regulated by electrostatic forces. Chromophores like tryptophan (Trp) are found to interact with C-GNRs, causing enhancement in fluorescence intensity. The conformation of protein is partially altered, evidenced by decrease in α-helical, increase in β-sheet and random coil of hemoglobin. Although C-GNRs do not essentially decrease oxygen binding capacity of hemoglobin, they hamper oxygen release from the protein. Heme, the oxygen binding unit, releases from hemoglobin upon C-GNR treatment, which could contribute to C-GNR-induced hemolysis. This study demonstrates the hematological effects of GNRs, revealing their potential risk in biomedical applications.