Systematically investigation of interactions between BSA and different charge-capped CdSe/ZnS quantum dots

Application of non-metal nanoparticles, as a novel approach, for improving the stability of blood products: 2011-2021

Despite the importance of the proper quality of blood products for safe transfusion, conventional methods for preparation and their preservation, they lack significant stability. Non-metal nanoparticles with particular features may overcome these challenges. This review study for the first time provided a comprehensive vision of the interaction of non-metal nanoparticles with each blood product (red blood cells, platelets and plasma proteins). The findings of this review on the most effective nanoparticle for improving the stability of RBCs indicate that graphene quantum dots and nanodiamonds show compatibility with RBCs. For increasing the stability of platelet products, silica nanoparticles exhibited a suppressive impact on platelet aggregation. Pristine graphene also shows compatibility with platelets. For better stability of plasma products, graphene oxide was indicated to preserve free human serum albumin from thermal shocks at low ionic strength. For increased stability of Factor VIII, mesoporous silica nanoparticles with large pores exhibit the superb quality of recovered proteins. Furthermore, 3.2 nm quantum dots exhibited anticoagulant effects. As the best promising nanoparticles for immunoglobulin stability, graphene quantum dots showed compatibility with γ-globulins. Overall, this review recommends further research on the mentioned nanoparticles as the most potential candidates for enhancing the stability and storage of blood components.

Serum proteins on nanoparticles: early stages of the "protein corona"

Nanoparticles in biological systems such as the bloodstream are exposed to a complex solution of biomolecules. A "corona" monolayer of proteins has historically been thought to form on nanoparticles upon introduction into such environments. To examine the first steps of protein binding, Fluorescence Correlation/Cross Correlation Spectroscopy and Fluorescence Resonance Energy Transfer were used to directly analyze four different nanoparticle systems. CdSe/ZnS core/shell quantum dots, 100 nm diameter polystyrene fluospheres, 200 nm diameter polystyrene fluospheres, and 200 nm diameter PEG-grafted DOTAP liposomes were studied with respect to serum protein binding, using bovine serum albumin as a model. Surface heterogeneity is found to be a key factor in protein binding to these nanoparticles, and as such we present a novel conceptualization of the early hard corona as low-ratio, non-uniform binding rather than a uniform monolayer.

Thermodynamic Implications and Time Evolution of the Interactions of Near-Infrared PbS Quantum Dots with Human Serum Albumin

Near-infrared (NIR)-emitting PbS quantum dots (QDs) are endowed with good stability, high quantum yield, and long lifetime in the body, so they are promising agents in biological imaging. They quickly form the so-called "protein corona" through nonspecific adsorption with proteins in biological fluids once upon exposure to the biological system. Here, PbS QDs and human serum albumin (HSA) were selected as the model system. Fluorescence quenching spectroscopic studies indicated a static quenching process caused by the addition of PbS QDs, which was corroborated by the UV-vis absorption spectroscopy and fluorescence lifetime. Thermodynamic parameters were obtained by the fluorescence quenching method. The enthalpy change and entropy change were well correlated with the "enthalpy-entropy compensation" (EEC) equation summarized in this work. The slope (α = 1.08) and the intercept (TΔS ₀ = 34.44 kJ mol^-1) indicated that the interaction resembled a protein-protein association. The both negative signs of enthalpy change and entropy change were elucidated by a proposed "two-step association-interaction" (TSAI) model. Agarose gel electrophoresis (AGE) and dynamic light scattering (DLS) showed that the binding ratio was roughly 2:1 (HSA/QDs), resembling sandwich-like structures. Furthermore, the secondary structure of HSA depended on the concentration of added QDs and the incubation time. The results preliminarily uncovered the physicochemical properties of QDs in the presence of proteins and elucidated the role of time evolution. These will inspire us to make the fluorescent QDs more biocompatible and use them in a proper way.

Detection of Human p53 In-Vitro Expressed in a Transcription-Translation Cell-Free System by a Novel Conjugate Based on Cadmium Sulphide Nanoparticles

Here, cadmium sulphide quantum dots (CdS QDs) have been synthetized and functionalized with Bovine Serum Albumin (BSA) in a colloidal aqueous solution with a stability of over 3 months. Specific synthesis conditions, in homogeneous phase and at low temperature, have allowed limitation of S2- concentration, hence, as a consequence, there is restricted growth of the nanoparticles (NPs). This fact allows binding with BSA in the most favorable manner for the biomolecule. The presence of Cd2+ ions on the surface of the CdS nanoparticle is counteracted by the negatively charged domains of the BSA, resulting in the formation of small NPs, with little tendency for aggregation. Temperature and pH have great influence on the fluorescence characteristics of the synthetized nanoparticles. Working at low temperatures (4 °C) and pH 10-11 have proven the best result as shown by hydrolysis kinetic control of the thioacetamide precursor of S2- ion. Biological activity of the coupled BSA is maintained allowing subsequent bioconjugation with other biomolecules such as antibodies. The chemical conjugation with anti-Glutathione S-transferase (α-GST) antibody, a common tag employed in human recombinant fusion proteins, produces a strong quenching of fluorescence that proves the possibilities of its use in biological labelling. Finally, p53, onco-human recombinant protein (GST tagged in COOH terminus), has been in situ IVTT (in vitro transcription-translation) expressed and efficiently captured by the α-GST-CdS QD conjugate as a proof of the biocompatibility on IVTT systems and the functionality of conjugated antibody.

Investigating the interaction between DNA-templated gold nanoclusters and HSA via spectroscopy

Gold nanoclusters (AuNCs) have attracted great attention in bioimaging and drug transportation due to their biocompatibility, but a few studies have shown their potential toxicity.

Role of surface charge on the interaction between carbon nanodots and human serum albumin

Carbon nanodots (Cdots) have aroused widespread concerns in the field of biomedical applications. In order to achieve better implications of behavior of Cdots in the biological environment, an array of spectroscopic, electrochemical and calorimetric techniques were performed to study the interaction of Cdots possessing different charges with human serum albumin (HSA) in physiological condition. Two polymer, polyethylene glycol (PEG) and polyetherimide (PEI), were applied to passivate the bare Cdots to achieve the Cdots with different surface charge, namely negatively charged PEG Cdots and positively charged PEI Cdots. The fluorescence of HSA was obviously quenched by both Cdots in a charge-independent behavior through a dynamic collision mechanism. Moreover, the association affinity of PEG Cdots or PEI Cdots bound to HSA was very close to each other. In addition, PEG Cdots with diverse content exhibited little effects on the secondary structure of HSA while only high content of PEI Cdots induced obvious conformation perturbation of HSA. The electrostatic forces dominate the association between HSA and PEI Cdots while the association of PEG Cdots to HSA is initiated by hydrophobic and van der Waals forces. Furthermore, the results of isothermal titration calorimetry revealed that both the interaction was driven by favorable entropy and enthalpy, which confirmed that these association processes are thermodynamically spontaneous. Finally, the sites marker competitive experiment showed that the association sites of Cdots with HSA exhibit a charge dependent manner, namely PEG Cdots effectively occupy the site I of HSA while the association sites of PEI Cdots are mainly located in site II.

Fluorescence alteration of MPA capped CdSe quantum dots by spontaneous biomarker protein adsorption

Quantum dots (QDs) have significant potentials in biomedical applications of bioimaging and biosensing. Spontaneous adsorption of proteins on QDs surface is a common phenomenon, which occurred to serum proteins in biological samples, and has been observed to enhance QDs fluorescence. In this study, fluorescence alteration of 3-mercaptopropionic acid (MPA) capped CdSe quantum dots by four individual biomarker proteins was investigated. By monitoring the fluorescence emission of QDs, the biomarker protein adsorbed spontaneously on QDs surface was recognized and quantified. When alpha fetoprotein (AFP) or heat shock protein 90 alpha (HSP90α) were present, the QDs became brighter. The presence of cytochrome C (CytoC) or lysozyme (Lyz) made the QDs dimmer first, and then brighter. Within five minutes response time all four biomarker proteins were detected individually with the estimated detection limit in the range of 1-10 ng/mL and good linear dynamic ranges. The results suggested that the fluorescence of QDs was responsive to not only serum proteins but also biomarker proteins. The fluorescence response was able to correlate quantitatively with the amount of biomarker proteins in relatively low concentrations. These results provide more information to understand QDs and support their applications in biomedical fields.

Investigation of biocompatible and protein sensitive highly luminescent quantum dots/nanocrystals of CdSe, CdSe/ZnS and CdSe/CdS

The size and shape dependent semiconductor quantum dots (0D nanoparticles) with color tunability demonstrating significant influence in a biological system and considered as ideal probes. Here, a non-coordinated colloidal approach was used for the synthesis of CdSe, CdSe/ZnS and CdSe/CdS core-shell quantum dots (QDs) of 3-4nm. The synthesized nanocrystals show a high crystallinity, examined by X-ray diffraction (XRD) and high-resolution electron microscopy (HRTEM). The core-shell semiconductor QDs exhibit stronger photoluminescence (PL) as compared to the core QDs. The strong PL with small full-width half maximum (FWHM) indicates that the prepared QDs have a nearly uniform size distribution and well dispersibility. The quantum yield (QY) of core-shell QDs increases due to the surface passivation. Further, the PL of BSA is quenched strongly by the presence of core-shell QDs and follows the well-known Stern-Volmer (S-V) relation, whereas the PL lifetime does not follow the S-V relation, demonstrating that the observed quenching is predominantly static in nature. Among CdSe core, CdSe/ZnS and CdSe/CdS core-shell QDs, the CdSe/ZnS QDs shows the least cytotoxicity and most biocompatibility. Thus, the prepared core-shell QDs are biocompatible and exhibit strong sensing ability.

Binding analysis of carbon nanoparticles to human immunoglobulin G: Elucidation of the cytotoxicity of CNPs and perturbation of immunoglobulin conformations

The chemical compositions, sizes and fluorescent properties of synthesized carbon nanoparticles (CNPs) were characterized. Escherichia coli (E. coli) cells were used as a model to study the cytotoxicity of CNPs, and the results of the cellular uptake of CNPs yielded excellent results: the CNPs demonstrated good biocompatibility and were non-toxic to the growth of the E. coli cells. Moreover, to assess the potential toxicity of CNPs to human health, the binding behavior of CNPs with human immunoglobulin G (HIgG) was examined by fluorescence quenching spectroscopy, synchronous fluorescence spectroscopy and circular dichroism spectroscopy under physiological conditions. The fluorescence quenching constants and parameters for the interaction at different temperatures had been calculated according to Scatchard. The thermodynamic parameters, such as enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG), were calculated, and the results indicated strong static quenching and showed that van der Waals forces, hydrogen bonds and hydrophobic interactions were the predominant intermolecular forces stabilizing the CNP-HIgG complex. Synchronous fluorescence and circular dichroism spectra provided information regarding the conformational alteration of HIgG in the presence of CNPs. These findings help to characterize the interactions between CNPs and HIgG, which may clarify the potential risks and undesirable health effects of CNPs, as well as the related cellular trafficking and systemic translocation.

Evaluation of the interaction between naringenin and human serum albumin: Insights from fluorescence spectroscopy, electrochemical measurement and molecular docking

Naringenin (Nar) is a flavanone compound found in grapefruits that is endowed with diverse pharmacological and biological activities. Here, the interaction between Nar and human serum albumin (HSA) was investigated via various methods, including fluorescence spectroscopy, electrochemical methods and molecular docking. The Stern-Volmer quenching constants inversely correlated with temperature, demonstrating that the fluorescence quenching about HSA-Nar system is initiated by the formation of a compound, which has confirmed by electrochemical measurements. Three-dimensional fluorescence demonstrated that Nar induces the slight unfolding of the polypeptides of HSA. The calculated thermodynamic parameters suggesting that the binding of Nar to HSA is spontaneous, and the mainly force is electrostatic interactions. In addition, site marker competitive experiments indicated that Nar binds to HSA both on site I (subdomain IIA) and site II (subdomain IIIA), with higher affinity to the latter one, consistence with molecular docking. Furthermore, the fluorescence resonance energy transfer (FRET) experiment showed the binding distance (r) is 2.65 nm. And the effects of metal ions on the HSA-Nar system are also discussed.

Study on the molecular interaction of graphene quantum dots with human serum albumin: combined spectroscopic and electrochemical approaches

Graphene quantum dots (GQDs) have attracted great attention in biological and biomedical applications due to their super properties, but their potential toxicity investigations are rarely involved. Since few studies have addressed whether GQDs could bind and alter the structure and function of human serum albumin (HSA), the molecular interaction between GQDs and HSA was systematically characterized by the combination of multispectroscopic and electrochemical approaches. GQDs could quench the intrinsic fluorescence of HSA via static mode. The competitive binding fluorescence assay revealed that the binding site of GQDs was site I of HSA. Some thermodynamic parameters suggested that GQDs interacted with HSA mainly through van der Waals interactions and hydrogen bonding interactions, and protonation might also participate in the process. As further revealed by FT-IR spectroscopy and circular dichroism technique, GQDs could cause the global and local conformational change of HSA, which illustrated the potential toxicity of GQDs that resulted in the structural damage of HSA. Electrochemical techniques demonstrated the complex formation between GQDs and HSA. Our results offered insights into the binding mechanism of GQDs with HSA and provided important information for possible toxicity risk of GQDs to human health.

Thermodynamic investigation of interaction between [(η6-p-cymene) RuII(acetone-N4-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin: spectroscopic and electrochemical studies

In this contribution, the interaction between [(η (6)-p-cymene)Ru(II)(acetone-N (4)-phenylthiosemicarbazone)Cl]Cl (Ru-TSC) anticancer drug and human serum albumin (HSA) was investigated by spectroscopic and electrochemical techniques. The fluorescence spectra results indicated that Ru-TSC anticancer drug could quench the intrinsic fluorescence of HSA through dynamic quenching mode. The calculated corresponding activation energy of the interaction between Ru-TSC anticancer drug and HSA was 35.62 kJ mol(-1). The distance between HSA and Ru-TSC anticancer drug was obtained according to fluorescence resonance energy transfer. The results of synchronous fluorescence spectra, three-dimensional fluorescence spectra, Fourier transform infrared spectroscopy (FTIR) spectra, and circular dichroism (CD) spectra indicated that the microenvironment and the conformation of HSA were all changed in the presence of Ru-TSC anticancer drug. The results of cyclic voltammetry further validated the interaction between Ru-TSC and HSA. These results indicated that the biological activity of HSA was affected by Ru-TSC anticancer drug dramatically.

Interaction of digestive enzymes with tunable light emitting quantum dots: a thorough Spectroscopic investigation

In this article, we have examined the direct spectroscopic and microscopic evidence of efficient quantum dots-α-chymotrypsin (ChT) interaction. The intrinsic fluorescence of digestive enzyme is reduced in the presence of quantum dots through ground-state complex formation. Based on the fluorescence data, quenching rate constant, binding constant, and number of binding sites are calculated under optimized experimental conditions. Interestingly, fluorescence quenching method clearly illustrated the size dependent interaction of MPA-CdTe quantum dots. Conformational change of ChT was traced using synchronous fluorescence measurements, circular dichroism and FTIR spectroscopic methods. Furthermore, the AFM results revealed that the individual enzyme molecule dimensions were changed after interacting with quantum dot. Consequently, this result could be helpful for constructing safe and effective utilisation of QDs in biological applications.

Comprehensive spectroscopic studies on the interaction of biomolecules with surfactant detached multi-walled carbon nanotubes

This paper investigates the interaction of ten diverse biomolecules with surfactant detached Multi-Walled Carbon Nanotubes (MWCNTs) using multiple spectroscopic methods. Declining fluorescence intensity of biomolecules in combination with the hyperchromic effect in UV-Visible spectra confirmed the existence of the ground state complex formation. Quenching mechanism remains static and non-fluorescent. 3D spectral data of biomolecules suggested the possibilities of disturbances to the aromatic microenvironment of tryptophan and tyrosine residues arising out of CNTs interaction. Amide band Shifts corresponding to the secondary structure of biomolecules were observed in the of FTIR and FT-Raman spectra. In addition, there exists an increased Raman intensity of tryptophan residues of biomolecules upon interaction with CNTs. Hence, the binding of the aromatic structures of CNTs with the aromatic amino acid residues, in a particular, tryptophan was evidenced. Far UV Circular spectra have showed the loss of alpha-helical contents in biomolecules upon interaction with CNTs. Near UV CD spectra confirmed the alterations in the tryptophan positions of the peptide backbone. Hence, our results have demonstrated that the interaction of biomolecules with OH-MWCNTs would involve binding cum structural changes and alteration to their aromatic micro-environment.

Studies on the interaction of apigenin with calf thymus DNA by spectroscopic methods

The interaction between apigenin and calf thymus deoxyribonucleic acid (ctDNA) in a pH 7.4 Tris-HCl buffer solution was investigated by UV-Vis spectroscopy, fluorescence spectroscopy, DNA melting techniques, and viscosity measurements. It was found that apigenin molecules could intercalate into the base pairs of DNA, forming a apigenin-DNA complex with a binding constant of K310K=6.4×10(4)Lmol(-1). The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) and Gibbs free energy (ΔG) were calculated to be 7.36×10(4)Jmol(-1), 329JK(-1)mol(-1) and -2.84×10(4)Jmol(-1) at 310K, respectively. Hydrophobic interaction was the predominant intermolecular force in stabilizing the apigenin-DNA complex. Thermal denaturation study suggested that the stabilization of the ctDNA helix was increased when the apigenin binding to ctDNA as indicated by the increase in thermal denaturation temperature of ctDNA at around 5.0°C in the presence of apigenin. Spectroscopic techniques together with melting techniques and viscosity determination provided evidences of intercalation mode of binding for the interaction between apigenin and ctDNA.

A heparin-mimicking reverse thermal gel for controlled delivery of positively charged proteins

Positively charged therapeutic proteins have been used extensively for biomedical applications. However, the safety and efficacy of proteins are mostly limited by their physical and chemical instability and short half-lives in physiological conditions. To this end, we created a heparin-mimicking sulfonated reverse thermal gel as a novel protein delivery system by sulfonation of a graft copolymer, poly(serinol hexamethylene urea)-co-poly(N-isopropylacylamide), or PSHU-NIPAAm. The net charge of the sulfonated PSHU-NIPAAm was negative due to the presence of sulfonate groups. The sulfonated PSHU-NIPAAm showed a typical temperature-dependent sol-gel phase transition, where polymer solutions turned to a physical gel at around 32°C and maintained gel status at body temperature. Both in vitro cytotoxicity tests using C2C12 myoblast cells and in vivo cytotoxicity tests by subcutaneous injections demonstrated excellent biocompatibility. In vitro release tests using bovine serum albumin revealed that the release from the sulfonated PSHU-NIPAAm was more sustained than that from the plain PSHU-NIPAAm. Furthermore, this sulfonated PSHU-NIPAAm system did not affect protein structure after 70-day observation periods.

Fluorescence resonance energy transfer between ZnSe ZnS quantum dots and bovine serum albumin in bioaffinity assays of anticancer drugs

In the current work, using ZnSe ZnS quantum dots (QDs) as representative nanoparticles, the affinities of seven anticancer drugs for bovine serum albumin (BSA) were studied using fluorescence resonance energy transfer (FRET). The FRET efficiency of BSA-QD conjugates can reach as high as 24.87% by electrostatic interaction. The higher binding constant (3.63×10(7)Lmol(-1)) and number of binding sites (1.75) between ZnSe ZnS QDs and BSA demonstrated that the QDs could easily associate to plasma proteins and enhance the transport efficacy of drugs. The magnitude of binding constants (10(3)-10(6)Lmol(-1)), in the presence of QDs, was between drugs-BSA and drugs-QDs in agreement with common affinities of drugs for serum albumins (10(4)-10(6)Lmol(-1)) in vivo. ZnSe ZnS QDs significantly increased the affinities for BSA of Vorinostat (SAHA), Docetaxel (DOC), Carmustine (BCNU), Doxorubicin (Dox) and 10-Hydroxycamptothecin (HCPT). However, they slightly reduced the affinities of Vincristine (VCR) and Methotrexate (MTX) for BSA. The recent work will not only provide useful information for appropriately understanding the binding affinity and binding mechanism at the molecular level, but also illustrate the ZnSe ZnS QDs are perfect candidates for nanoscal drug delivery system (DDS).

Development of morin-conjugated Au nanoparticles: exploring the interaction efficiency with BSA using spectroscopic methods

In order to enhance its interaction efficiency with biomacromolecules for the usage as a therapeutic agent, we have conjugated morin, an antioxidant activity and anti-tumor drug, with citrate-coated Au nanoparticles (M-C-AuNPs). M-C-AuNPs were prepared by reducing chloroauric acid using trisodium citrate in the boiling condition, and the resulted M-C-AuNPs were characterized by UV-vis absorption spectroscopy, Transmission Electron Microscopy (TEM), X-ray diffraction (XRD) and FTIR analysis. In this article, UV-vis absorption spectroscopy in combination with fluorescence spectroscopy, and circular dichroism (CD) spectroscopy were employed to investigate the interactions between M-C-AuNPs and bovine serum albumin (BSA), C-AuNPs and BSA in a phosphate buffer at pH 7.4. By comparing the quenching constant KSV, effective quenching constant Ka, binding constant Kb and the number of binding sites n, it is clearly suggested that M-C-AuNPs could enhance the binding force of morin with BSA, which would pave the way for the design of nanotherapeutic agents with improved functionality.

Combined spectroscopy and cyclic voltammetry investigates the interaction between [(η6-p-cymene)Ru(benzaldehyde-N(4)-phenylthiosemicarbazone)Cl]Cl anticancer drug and human serum albumin

The interaction between Ru anticancer drug and HSA was investigated systematically under physiological conditions.

Facile synthesis and characterization of highly fluorescent and biocompatible N-acetyl-L-cysteine capped CdTe/CdS/ZnS core/shell/shell quantum dots in aqueous phase

The synthesis of water-soluble quantum dots (QDs) in aqueous phase has received much attention recently. To date various kinds of QDs such as CdTe, CdSe, CdTe/CdS and CdSe/ZnS have been synthesized by aqueous methods. However, generally poor-quality QDs (photoluminescent quantum yield (PLQY) lower than 30%) are obtained via this method and the 3-mercaptopropionic acid stabilizer is notorious for its toxicity and awful odor. Here we introduce a novel thiol ligand, N-acetyl-L-cysteine, as an ideal stabilizer that is successfully employed to synthesize high-quality CdTe/CdS/ZnS QDs via a simple aqueous phase. The core/shell/shell structures of the CdTe/CdS/ZnS QDs were verified by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, x-ray powder diffraction and transmission electron microscopy. These QDs not only possess a high PLQY but also have excellent photostability and favorable biocompatibility, which is vital for many biological applications. This type of water-dispersed QD is a promising candidate for fluorescent probes in biological and medical fields.