Fabrication of Protein-Conjugated Silver Sulfide Nanorods in the Bovine Serum Albumin Solution

Thin Film Formation of HSA in the Presence of CTAB-Capped Gold Nanorods through Phase Separation

Phase behavior in protein-nanoparticle systems in light of protein corona formation has been investigated. We report the formation of HSA thin films following the addition of a solid protein to a solution of CTAB-capped gold nanorods (AuNRs) via phase separation. The phase separation behavior was observed through UV-vis spectroscopy, turbidity assays, and DLS studies. UV-vis spectra for the protein-AuNR solution indicated a possible self-assembly formation by CTAB-HSA complexes and AuNR-HSA conjugates. The turbidity was found to increase linearly up to 30-50% v/v for each component. The growth phase slope is proportional to the concentration of the components, AuNRs, and HSA, with no lag phase. Dynamic light scattering (DLS) shows the formation of larger aggregates with time, implying a segregated phase of AuNR-HSA and a CTAB-HSA-AuNR network. ζ-potential values confirm surface modification, implying protein corona formation on nanorods. The thin films were also characterized using SEM, AFM, SAXS, XPS, FTIR, and TGA studies. SEM images show a smooth surface with a reduced number of pores, indicating the compactness of the deposited structure. AFM shows two different structural pattern formations with the deposition, indicating possible self-assembly of the protein-conjugated nanoparticles. FTIR studies indicate a change in the hydrogen bonding network and confirm the CTAB-HSA-AuNR complex network formation. The XPS studies indicate Au-S bond formation, along with Au-S-S-Au interactions. SAXS studies indicate the formation of aggregates (oligomers), as well as the presence of dominant attractive intermolecular interactions in the thin films.

Protein-directed synthesis of fluorescent sulfur quantum dots for highly robust detection of pyrophosphate

Inorganic pyrophosphate anions (PPi) play a key role in various biological processes and act as an essential indicator for physiological function evaluation and disease diagnosis. However, there is still a lack of available approaches for straightforward, robust, and convenient PPi detection. Herein, we design an on-off-on fluorescent switching nanoprobe employing Fe³⁺-mediated fluorescent sulfur quantum dots (SQDs) for highly robust detection of PPi. The bovine serum protein (BSA)-capped SQDs with fine water dispersibility and good optical stability are synthesized by an H₂O₂-assisted chemical etching reaction. Specifically, Fe³⁺ can strongly induce the aggregation of the SQDs into relatively larger sizes, resulting in aggregation-induced fluorescence quenching behavior. PPi can selectively bind with Fe³⁺ via emulative coordination and in preventing the aggregation of SQDs this is accompanied by recovery of fluorescence. The physicochemical properties of aggregated and disaggregated SQDs have been systematically investigated. Aggregation and disaggregation of the SQDs and the corresponding quenching and recovery of fluorescence occurs and guarantees the high-contrast sensing performance of the SQD system in complex and challenging aquatic environments. Our designed on-off-on nanoswitch holds great potential for the design of elemental quantum dot-based biosensors for the highly robust detection of analytes in the near future.

Synthesis, Properties and Bioimaging Applications of Silver-Based Quantum Dots

Ag-based quantum dots (QDs) are semiconductor nanomaterials with exclusive electrooptical properties ideally adaptable for various biotechnological, chemical, and medical applications. Silver-based semiconductor nanocrystals have developed rapidly over the past decades. They have become a promising luminescent functional material for in vivo and in vitro fluorescent studies due to their ability to emit at the near-infrared (NIR) wavelength. In this review, we discuss the basic features of Ag-based QDs, the current status of classic (chemical) and novel methods ("green" synthesis) used to produce these QDs. Additionally, the advantages of using such organisms as bacteria, actinomycetes, fungi, algae, and plants for silver-based QDs biosynthesis have been discussed. The application of silver-based QDs as fluorophores for bioimaging application due to their fluorescence intensity, high quantum yield, fluorescent stability, and resistance to photobleaching has also been reviewed.

Mimicking biological process to detect alkaline phosphatase activity using the vitamin B6 cofactor conjugated bovine serum albumin capped CdS quantum dots

This manuscript presents a novel bioanalytical approach for the selective ratiometric fluorescent sensing of enzymatic activity of the alkaline phosphatase (ALP) in the biological samples. The probe was designed by conjugating the pyridoxal 5'-phosphate (PLP) over the surface of bovine serum albumin (BSA) stabilized CdS quantum dots (QDs) through the interaction of free amine present in BSA with the aldehyde group of PLP. The conjugation of PLP quenched the emission of QDs. Upon addition of the ALP, the emission of QDs was restored due to the dephosphorylation and the conversion of the functionalized PLP in to pyridoxal. With this probe, the ALP activity can be detected down to 0.05 U/L and also successfully applied for the detection of ALP activity in biological samples such as human serum and plasma.

A welding phenomenon of dissimilar nanoparticles in dispersion

The oriented attachment of small nanoparticles (NPs) is recognized as an important mechanism involved in the growth of inorganic nanocrystals. However, non-oriented attachment of dissimilar NPs has been rarely observed in dispersion. This communication reports a welding phenomenon occurred directly between as-synthesized dispersions of single-component Au and chalcogenide NPs, which leads to the formation of asymmetric Au-chalcogenide hybrid NPs (HNPs). The welding of dissimilar NPs in dispersion is mainly driven by the ligand desorption-induced conformal contact between NPs and the diffusion of Au into chalcogenide NPs. The welding process can occur between NPs with distinct shapes or different capping agents or in different solvent media. A two-step assembly-welding mechanism is proposed for this process, based on our in situ electron spin resonance measurements and ab initio molecular dynamics simulation. The understanding of NP welding in dispersion may lead to the development of unconventional synthetic tools for the fabrication of hybrid nanostructures with diverse applications.

Nunes C, Tarczay G, Fausto R. Selective conformational control by excitation of NH imino vibrational antennas

We provide experimental evidence for the occurrence of selective and reversible conformational control over the SH group by vibrational excitation of remote NH groups. Using an imino group that acts as a molecular antenna has no precedents.

Discrete SeNPs-Macromolecule Binding Manipulated by Hydrophilic Interaction

Nanoparticle-protein conjugates are promising probes for biological diagnostics and versatile building blocks for nanotechnology. Here we demonstrate the interaction of SeNPs with BSA macromolecule simply by physical adsorption method. The interaction between SeNPs and BSA has been investigated by UV-Vis, fluorescence, circular dichroism (CD) spectroscopic and thermal methods. The esterase-like activity of BSA towards PNPA was investigated in the presence of SeNPs. The effects of SeNPs on the stability and conformational changes of BSA were studied, which indicated that the binding of SeNPs with BSA induced relative changes in secondary structure of protein. SeNPs acted as a structure stabilizer for BSA which was further confirmed by thermal denaturation study. The hydrophilic bonding forces played important roles in the BSA-SeNPs complex formation. The putative binding site of SeNPs on BSA was near to Sudlow's site II. The hydrophilic interaction of SeNPs on the stability and structure of BSA would find promising application in drug delivery system.

Using Nanoparticles in Medicine for Liver Cancer Imaging

One of the most important types of liver cancer is hepatocellular carcinoma (HCC). HCC is the fifth most common cancer, and its correct diagnosis is very important. For the quick diagnosis of HCC, the use of nanoparticles is helpful. The major applications of nanoparticles are in medicine for organ imaging. Two methods of liver imaging are X-ray computed tomography (CT) and magnetic resonance imaging (MRI). In this review, we attempt to summarize some of the contrast agents used in imaging such as superparamagnetic iron oxide nanoparticles (SPIONs) and iron oxide nanoparticles (IONPs), various types of enhanced MRI for the liver, and nanoparticles like gold (AuNPs), which is used to develop novel CT imaging agents.

Hepatoprotective activity of Butea monosperma bark against thioacetamide-induced liver injury in rats

For thousands of years, the plant-based natural products have been a source of curative agents for various ailments. Butea monosperma (Fabaceae) has an important place in Indian traditional system of medicine for curing number of disorders. The present study deals with evaluation of hepatoprotective properties of ethyl acetate fraction (Beac) from B. monosperma bark in rat model. In preliminary antioxidant studies, Beac demonstrated pronounced superoxide scavenging (IC₅₀ 88.85μg/ml) and anti-lipid peroxidation (IC₅₀ 131.66μg/ml) potential. In animal studies, Beac showed protective effect against thioacetamide-induced pathophysiology in liver of male Wistar rats. The levels of different parameters related to hepatic functions were altered by thioacetamide treatment (300mg/g bw) in rats. The pre-treatment of rats with Beac (50, 100 and 200mg/kg bw) was able to normalize the biochemical markers viz. serum bilirubin, SGOT, SGPT, albumin and ALP along with liver antioxidative molecules viz. SOD, CAT, GSH and GR. Results of histopathological and colorimetric studies revealed that Beac treatment also restored the markers of fibrosis i.e. collagen and hydroxyproline towards normal level. Beac considerably inhibited thioacetamide-induced expression of p-PI3K, p-Akt and p-mTOR in hepatocytes as revealed from immunohistochemical studies. This finding is the first evidence of inhibitory action of B. monosperma bark on these pro-carcinogenic proteins. HRMS analysis revealed the presence of quercetin, buteaspermin B and ononin in Beac fraction of Butea monosperma. From the results, it can be concluded that B. monosperma bark is a rich source of phytochemicals with in vitro and in vivo protective activities which deserves further mechanistic studies for its use as a hepatoprotective agent in the prevention of hepatic inflammation and its related malignancies.

Antibacterial and biological properties of biofunctionalized nanocomposites on titanium for implant application

Titanium implants possessing excellent antibacterial activity are highly desirable for the prevention of implant-associated infections. In this study, we demonstrate a simple one-step, water-based procedure for the fabrication of biofunctionalized nanocomposites on titanium for implant application. The formation of biofunctionalized silver nanoparticles with varied biomolecule templates is confirmed by Fourier-transform infrared spectroscopic, contact angle, field-emission scanning electron microscopy, and inductively coupled plasma atomic emission spectrometry analysis. Antibacterial properties of the specimens were determined by challenging them against Staphylococcus aureus. The Ag-incorporated titanium shows excellent antibacterial ability against planktonic bacteria in the suspension and ability to prevent bacterial adhesion. The specimens with optimized biomolecule/silver ratio promote osteoblast differentiation. These biofunctionalized silver nanoparticles-doped titanium specimens, with improved antibacterial activity while maintaining healthy osteoblast cellular activity, have promising application in orthopedics, dentistry, and other biomedical devices.

Sulfur antisite-induced intrinsic high-temperature ferromagnetism in Ag2S:Y nanocrystals

Sulfur antisite-induced intrinsic robust high-temperature ferromagnetism has been achieved in Ag₂S:Y nanocrystals.

Mechanistic and Electrochemical Investigation of Catechol Oxidation in the Presence of Thioacetamide: Application for Voltammetric Determination of Thioacetamide in Aqueous Media

Electrochemical oxidation of catechol has been studied in the presence of thioacetamide (TAM) in a phosphate buffer solution (0.2 mol L−1, pH=6.0) at the surface of glassy carbon electrode by means of cyclic voltammetry. After the cyclic voltammetric investigation of the reaction mechanism of TAM with catechol, TAM has been determinated by means of the differential pulse voltammetry technique. The results showed that the cathodic peak current of catechol reduced in the presence of various concentrations of TAM and that catechol can participate in a 1,4-Michael addition reaction with TAM under an EC mechanism. The decreasing of the cathodic current of catechol showed a linear relationship with the TAM concentration that can be used for the determination of TAM with a detection limit less than 3 μmol L−1.

Direct synthesis of CdS nanodots embedded in bovine serum albumin without external sulfur source for cell imaging

CdS nanodots with good water solubility and low cell cytotoxicity were synthesized using BSA as template without external sulfur.

Bioinspired, direct synthesis of aqueous CdSe quantum dots for high-sensitive copper(II) ion detection

Luminescent CdSe semiconductor quantum dots (QDs), which are coated with a denatured bovine serum albumin (dBSA) shell, have been directly synthesized via a bioinspired approach. The dBSA coated CdSe QDs are ultrasmall (d < 2.0 nm) with a narrow size distribution and exhibit a strong green fluorescent emission at about 525 nm. They can be stored for months at room temperature and possess excellent stability against ultraviolet irradiation, high salt concentration, and a wide physiological range of pH. Systematic experimental investigations have shown the contribution of dBSA with free cysteine residues for both their effective ion chelating and surface passivating interactions during the formation and stabilization of CdSe QDs. The luminescent QDs are used for copper(II) ion detection due to their highly sensitive and selective fluorescence quenching response to Cu(2+). The concentration dependence of the quenching effect can be best described by the typical Stern-Volmer equation in a linearly proportional concentration of Cu(2+) ranging from 10 nM to 7.5 μM with a detection limit of 5 nM. As confirmed by various characterization results, a possible quenching mechanism is given: Cu(2+) ions are first reduced to Cu(+) by the dBSA shell and then chemical displacement between Cu(+) and Cd(2+) is performed at the surface of the ultrasmall metallic core to impact the fluorescence performance.

Microwave-assisted synthesis of glycopolymer-functionalized silver nanoclusters: combining the bioactivity of sugar with the fluorescence and cytotoxicity of silver

Copolymers of 2-(methacrylamido)glucopyranose (MAG) and methacrylic acid (MAA) are synthesized by RAFT polymerization and then used as templates to prepare glycopolymer-functionalized Ag nanoclusters (Gly-Ag NCs) through microwave irradiation. Polymers and the resulting nanoclusters are characterized by NMR, GPC, UV-Vis, SEM, TEM, AAS and fluorescence spectroscopy. The bio-activity of the fluorescent Gly-Ag NCs are further examined using GLUT-1 over-expressing cancer cells K562. Gly-Ag NCs show efficient binding ability toward K562 cells and inhibit the cell viability in a dose dependent manner (IC50 = 0.65 μg mL(-1)), indicating their potential biological applications for both cancer imaging and targeted cancer therapy.

Rapid synthesis of NADPH responsive CdSe quantum dots from selenium nanoparticles

Herein we developed a new approach for CdSe quantum dots (QDs) synthesis.

An approach for catalyst design in artificial photosynthetic systems: focus on nanosized inorganic cores within proteins

Some enzymes can be considered as a catalyst having a nanosized inorganic core in a protein matrix. In some cases, the metal oxide or sulfide clusters, which can be considered as cofactors in enzymes, may be recruited for use in other related reactions in artificial photosynthetic systems. In other words, one approach to design efficient and environmentally friendly catalysts in artificial photosynthetic systems for the purpose of utilizing sunlight to generate high energy intermediates or useful material is to select and utilize inorganic cores of enzymes. For example, one of the most important goals in developing artificial photosynthesis is hydrogen production. However, first, it is necessary to find a "super catalyst" for water oxidation, which is the most challenging half reaction of water splitting. There is an efficient system for water oxidation in cyanobacteria, algae, and plants. Published data on the Mn-Ca cluster have provided details on the mechanism and structure of the water oxidizing complex as a Mn-Ca nanosized inorganic core in photosystem II. Progress has been made in introducing Mn-Ca oxides as efficient catalysts for water oxidation in artificial photosynthetic systems. Here, in the interest of designing efficient catalysts for other important reactions in artificial photosynthesis, a few examples of our knowledge of inorganic cores of proteins, and how Nature used them for important reactions, are discussed.

Systematic investigation of the toxicity interaction of ZnSe@ZnS QDs on BSA by spectroscopic and microcalorimetry techniques

The interaction of ZnSe@ZnS quantum dots (QDs) and bovine serum albumin (BSA) was investigated by means of fluorescence (FL) spectrometry, circular dichroism (CD) spectra, and isothermal titration calorimetry (ITC). The fluorescence intensity of BSA decreased regularly with the increasing of QDs concentration. The decrease of BSA fluorescence intensity was proved to be a kind of static quenching. CD results show the helicity of BSA decreased from 38.04% to 26.51% with the addition of QDs, which suggests a stronger structural change that is related to a low degree of surface coverage. And also, both ion strength and pH value could affect the interaction between BSA and QDs, suggesting that both the static electronic attraction and H-bond contribute to the interaction between BSA and QDs. The thermodynamics of interaction between BSA and QDs were calculated from ITC data. Both enthalpy and entropy changes were favorable for the interaction in Tris-buffer, while only enthalpy change was favorable for the interaction in NaCl or HCl solution.

A versatile polydopamine platform for facile preparation of protein stationary phase for chip-based open tubular capillary electrochromatography enantioseparation

A novel, simple, and economical method for the preparation of chiral stationary phases for chip-based enantioselective open tubular capillary electrochromatography (OT-CEC) using polydopamine (PDA) coating as an adhesive layer was reported for the first time. After the poly(dimethylsiloxane) (PDMS) microfluidic chip was filled with dopamine (DA) solution, PDA film was gradually formed and deposited on the inner wall of microchannel as permanent coating via the oxidation of DA by the oxygen dissolved in the solution. Due to possessing plentiful catechol and amine functional groups, PDA coating can serve as a versatile multifunctional platform for further secondary reactions, leading to tailoring of the coatings for protein bioconjugation by the thiols and amines via Michael addition or Schiff base reactions. Bovine serum albumin (BSA), acting as a target protein, was then stably and homogeneously immobilized in the PDA-coated PDMS microchannel to fabricate a novel protein stationary phase. Compared with the native PDMS microchannels, the modified surfaces exhibited much better wettability, more stable and enhanced electroosmotic mobility, and less nonspecific adsorption. The water contact angle and electroosmotic flow of PDA/BSA-coated PDMS substrate were measured to be 44° and 2.83×10(-4)cm(2)V(-1)s(-1), compared to those of 112° and 2.10×10(-4)cm(2)V(-1)s(-1) from the untreated one, respectively. Under a mild condition, d- and l-tryptophan were efficiently separated with a resolution of 1.68 within 130s utilizing a separation length of 37mm coupled with in-column amperometric detection on the PDA/BSA-coated PDMS microchips. This present versatile platform, facile conjugation of biomolecules onto microchip surfaces via mussel adhesive protein inspired coatings, may offer new processing strategies to prepare a biomimetic surface design on microfluidic chips, which is promising in high-throughput and complex biological analysis.

Retracted Article: Aqueous synthesis of human serum albumin-stabilized fluorescent Au/Ag core/shell nanocrystals for highly sensitive and selective sensing of copper(ii)

Using human serum albumin as a reductive plus stabilizing agent, fluorescent Au/Ag core/shell nanocrystals were prepared at pH 9.0 and 37 °C, and further developed as a highly sensitive and selective sensor of Cu²⁺.

Bio-mimetically synthesized Ag@BSA microspheres as a novel electrochemical biosensing interface for sensitive detection of tumor cells

The use of a novel cytosensor, comprised of bio-mimetically synthesized Ag@BSA composite microspheres, for the detection of KB cells (a model system) is described. The Ag@BSA composite microspheres were immobilized on Au electrodes via Au-thiol bonds. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) images revealed that the Ag@BSA were well-dispersed microspheres with an average diameter of 500 nm, including the monolayer of BSA. The immobilization of Ag@BSA composite microspheres onto Au electrodes is thought to increase the electrode surface area and accelerate the electron transfer rate while providing a highly stable matrix for the convenient conjugation of target molecules (such as folic acid) and the prolonged incubation of cells. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies showed that the fabricated cytosensor was able to detect KB cells ranging from 6.0×10(1) to 1.2×10(8) cells mL(-1) with a lower detection limit of 20 cells mL(-1). Due to its facile synthesis, high stability and reproducibility and cytocompatibility, the novel cytosensor described here could find multifarious uses in applications, such as cancer diagnosis, drug screening and cell adhesion studies.

Biomineralization: a proposed evolutionary origin for inorganic cofactors of enzymes

In this paper, three different reactions of nanoparticles and proteins are explained. As a model system, the interactions of birnessite, which is a common manganese oxide in the environment, and bovine serum albumin, as a protein that has a strong affinity for a variety of inorganic molecules, are studied. The author proposes that the cofactor-formation in particular enzymes may be considered as a biomineralization in the presence of the protein. One of the numerous and very small nanoparticles produced in the presence of protein could be formed in an appropriate location in proteins and be used as a primitive inorganic core (cofactor) of enzyme.

Protein-induced structural evolution of silver sulfide at the nanoscale: from hollow particles to solid spheres

Herein, a novel structural transformation of Ag(2)S nanoparticles from hollow particles to solid spheres is reported. The features of these structures are identified through a set of characterizations based on which the formation mechanism is also investigated.

Nano-sized manganese oxides as biomimetic catalysts for water oxidation in artificial photosynthesis: a review

There has been a tremendous surge in research on the synthesis of various metal compounds aimed at simulating the water-oxidizing complex (WOC) of photosystem II (PSII). This is crucial because the water oxidation half reaction is overwhelmingly rate-limiting and needs high over-voltage (approx. 1 V), which results in low conversion efficiencies when working at current densities required for hydrogen production via water splitting. Particular attention has been given to the manganese compounds not only because manganese has been used by nature to oxidize water but also because manganese is cheap and environmentally friendly. The manganese-calcium cluster in PSII has a dimension of about approximately 0.5 nm. Thus, nano-sized manganese compounds might be good structural and functional models for the cluster. As in the nanometre-size of the synthetic models, most of the active sites are at the surface, these compounds could be more efficient catalysts than micrometre (or bigger) particles. In this paper, we focus on nano-sized manganese oxides as functional and structural models of the WOC of PSII for hydrogen production via water splitting and review nano-sized manganese oxides used in water oxidation by some research groups.

Facile synthesis of fluorescent porous zinc sulfide nanospheres and their application for potential drug delivery and live cell imaging

Fabrication of intrinsically fluorescent porous nanocarriers that are simultaneously stable in aqueous solutions and photostable is critical for their application in drug delivery and optical imaging but remains a challenge. In this study, fluorescent porous zinc sulfide nanospheres were synthesized by a facile gum arabic-assisted hydrothermal procedure. The morphology, composition and properties of the nanospheres have been characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, N(2) adsorption-desorption analysis, thermal gravimetric analysis, fourier transform infrared spectrograph, optical measurement, dynamic light scattering, and cytotoxicity assay. They exhibit larger surface area, excellent colloidal stability, photostable fluorescent signals, and good biocompatibility, which makes them promising hosts for drug delivery and cellular imaging. The fluorescent dye safranine-T was employed as a drug model and loaded into the porous nanospheres, which were delivered to human cervical cancer HeLa cells in vitro for live cell imaging.

Fungus-mediated biological synthesis of gold nanoparticles: potential in detection of liver cancer

BACKGROUND

Nanomaterials are considered to be the pre-eminent component of the rapidly advancing field of nanotechnology. However, developments in the biologically inspired synthesis of nanoparticles are still in their infancy and consequently attracting the attention of material scientists throughout the world. Keeping in mind the fact that microorganism-assisted synthesis of nanoparticles is a safe and economically viable prospect, in the current study we report Candida albicans-mediated biological synthesis of gold nanoparticles.

METHODS AND RESULTS

Transmission electron microscopy, atomic force microscopy, and various spectrophotometric analyses were performed to characterize the gold nanoparticles. The morphology of the synthesized gold particles depended on the abundance of C. albicans cytosolic extract. Transmission electron microscopy, nanophox particle analysis, and atomic force microscopy revealed the size of spherical gold nanoparticles to be in the range of 20-40 nm and nonspherical gold particles were found to be 60-80 nm. We also evaluated the potential of biogenic gold nanoparticles to probe liver cancer cells by conjugating them with liver cancer cell surface-specific antibodies. The antibody-conjugated gold particles were found to bind specifically to the surface antigens of the cancer cells.

CONCLUSION

The antibody-conjugated gold particles synthesized in this study could successfully differentiate normal cell populations from cancerous cells.

Keratin capped silver nanoparticles--synthesis and characterization of a nanomaterial with desirable handling properties

We report for the first time the stabilization of silver nanoparticles in good yield, average diameter 3.5 nm, using wool keratin hydrolysates as stabilizers. The nanoparticles are extremely stable as a suspension and can be lyophilized into a powder and easily reconstituted in solvent with no change in spectral properties relative to the initial suspension. The nanoparticles interact with nitrogen and oxygen moieties of the keratin hydrolysates under the pH conditions used in the synthesis and appear to act as cross-linkers between adjacent chains. The product has excellent handling properties which we believe will make it a very attractive biocompatible coating/additive, providing prolonged antimicrobial efficacy to a wide variety of products such as textiles, plastics, paints, orthopedic devices and others.