Resonance Light Scattering Technique Research Articles

Sensitively and Selectively Detect Biothiols by Using Fluorescence Method and Resonance Light Scattering Technique Simultaneously.

In this paper, we designed a new quantitative and qualitive detection method for biothiols by using fluorescence method and resonance light scattering (RLS) technique. Nitrogen doped carbon quantum dots (C/N-dots) were obtained from tartaric acid and ethylenediamine by hydrothermal method, and then their morphology and optical properties were characterized by different techniques. A detection system consisting of C/N-dots and Ag+ complex was established. In this system, C/N-dots possessed the photoluminescent property and the Ag+ complex owned the RLS property, so, by combining the two luminescent properties to achieve complementary advantages, we could detect biothiols and solve the problem of distinguishing between Cys and GSH. Additionally, we optimized detecting conditions and investigated the detection mechanism of fluorescence quenching and RLS detecting. Results showed that the analytical response of fluorescence was linear in the range 0–140 μM and the detection limit (LOD) was calculated to be 6.6 μM for Cys, and the addition of GSH had no effect on fluorescence. RLS response ranges were 0–167 μM for Cys and 0–200 μM for GSH, with LOD down to 64 nM and 74 nM, respectively. Furthermore, the probe was successfully used for detecting Cys in fetal bovine serum (FBS) samples by fluorescence method, and also, by RLS technique, the content of GSH in FBS samples was detected.

Structural transition of lactoferrin upon interaction with estradiol as revealed by spectroscopic techniques: a molten globule state investigation

Proteins have numerous physiological functions in the body. Their most important property is serving as depot carriers and as target molecules for many drugs. Three-dimensional fluorescence spectroscopy, zeta potential analysis, resonance light scattering (RLS), thermodynamic analysis, circular dichroism and fluorescence resonance energy transfer (FRET) measurements were performed to study the interactions between estradiol and human lactoferrin (Hlf). According to the three-dimensional fluorescence spectra, the binding of the drug to Hlf induced a slight destabilization of the protein. Circular dichroism results provided new insight into the course of structural transitions of Hlf after addition of estradiol, and revealed that a molten globule state was intermediate between the native and unfolded states. This is a compact state with a significant amount of native-like secondary structure, but a largely disordered tertiary structure. The experimental results further indicated that the fluorescence quenching mechanism between Hlf and estradiol corresponded to a static quenching procedure. The binding constant and the number of binding sites were obtained from modified Stern–Volmer diagrams. The distance r between donor and acceptor was obtained by FRET and found to be 1.96 nm for estradiol and Hlf. The critical induced aggregation concentrations (CCIAC) of estradiol on Hlf were determined by a non-linear relationship between the enhancement of the RLS intensities and drug concentrations. The zeta potential results were used to verify the existence of complexes and confirmed the CCIAC values obtained by the RLS technique. In addition, molecular modeling showed that estradiol was bound within the domain II of the C-lobe and N-lobe of the Hlf via hydrophobic interactions and hydrogen bonding.

Ultrasensitive Detection of Protein Based on Graphene Quantum Dots with Resonance Light Scattering Technique.

In this paper, a simple, label-free and ultrasensitive resonance light scattering (RLS) method for ultratrace protein detection was investigated using graphene quantum dots (GQDs) as probes. Due to the electrostatic interaction between GQDs and protein, the RLS intensity was gradually enhanced as the protein was added into the GQDs solution. Through a series of optimization experiments, the optimal detection conditions of the GQDs solution were as follows: pH = 7.4, 2 M ion concentration and 60 μM GQDs. Under the optimized conditions, the linear correlation between the GQDs and the concentration of protein was observed from 10 μM to 60 μM with the correlation coefficient (R2) of 0.9978, and the limit of detection (LOD) was 2.4 μM. Time-resolved fluorescence spectrum showed that the electron transition channel was not affected by the protein self-assembled on the surface of GQDs, which indicated that the interaction between GQDs and protein was mainly the electrostatic interaction. The proposed method revealed that the RLS enhancement effect from the self-assembled GQDs-protein hybrid nano-system provided a green and simple method to establish ultrasensitive biosensors.

Ag nanoparticles for determination of bisphenol A by resonance light-scattering technique

Resonance light-scattering (RLS) technique was developed for studying the interaction of silver nanoparticles (Ag NPs) with bisphenol A. A simple and environmentally friendly method was developed to synthesize Ag NPs using cinnamon extract. Synthesized nanoparticles were characterized using various measurement techniques. The synthesized Ag NPs were nearly spherical, with the sizes ranging from 30 to 60 nm. Spectral analysis indicated that the cinnamon extract acted as the reducing and capping agents on the surface of Ag NPs. RLS technique was used as the detection method. Light-scattering properties of the synthesized nanoparticles in the presence or absence of bisphenol A was selected as the detection signal. Under the optimal conditions, the linear dynamic range and RSD were found to be 0.01–10.0 mg L−1 and 2.78% (n = 3), respectively. A limit of detection of 0.005 mg L−1 was obtained for the determination of bisphenol A. The obtained results showed successful application of the method for the analysis of bisphenol A in real samples.

Rotatable anisotropy on ferromagnetic/antiferromagnetic bilayer investigated by Brillouin light scattering

The nature of the rotatable anisotropy in ferromagnetic/antiferromagnetic (FM/AF) NiFe/IrMn bilayers has been investigated using magneto-optical Kerr effect magnetometry, ferromagnetic resonance, and Brillouin Light Scattering (BLS) techniques. The behavior of the magnon frequencies with an external magnetic field applied in the bilayer plane has been measured by BLS. The angular dependence of magnon frequency shows a shift when compared to numerical calculation for different magnetic field intensities. This frequency shift can be associated with the rotatable anisotropy and it depends on the magnetic field intensity. As a result, the rotatable anisotropy field exhibits a non-monotonic dependence on the applied field. The results are interpreted considering the coexistence of parallel and antiparallel coupling at the FM/AF interface.

"Click on the bidirectional switch": the aptasensor for simultaneous detection of lysozyme and ATP with high sensitivity and high selectivity.

A bifunctional and simple aptasensor was designed to one-spot simultaneously detect two analytes, lysozyme and ATP. The aptasensor was obtained by the electronic interaction between methyl violet (MV) and dsDNA. The dsDNA was obtained by hybridization of ATP aptamer and lysozyme aptamer. And we used the resonance light scattering (RLS) technique to detect the concentration of lysozyme and ATP. During the procedure of detection, the aptasensor works like a bidirectional switch, the corresponding side of the dsDNA will open when the target (lysozyme or ATP) “click” the aptamer, which results in corresponding RLS signal change. By the combination of the RLS technique, it is found that the changed RLS intensity was proportional to the concentration of lysozyme and ATP. The mixtures of ATP and lysozyme also met two binary function relations. The results indicated that the aptasensor could achieve simultaneous detection of ATP and lysozyme, the detection limits of ATP and lysozyme could reach 10−11 M and 10−12 M, respectively. The aptasensor shows potential application for small molecule and protein detection by RLS, it could extend the application of RLS technique.

A novel resonance light scattering sensing for glucose based on the conversion of gold nanoclusters into gold nanoparticles

A novel and label-free resonance light scattering (RLS) assay for sensing glucose was constructed based on the conversion of gold nanoclusters into gold nanoparticles. It was observed that a size-focusing conversion of ultra-small size protein stabilized gold nanoclusters (Au NCs) into larger diameter gold nanoparticles (Au NPs) after the introduction of hydrogen peroxide (H2O2). As for the stepwise enlargement for gold nanoclusters with increasing concentration of H2O2, the RLS intensity can be gradually increased, which offers the new approach for the quantitative detection of H2O2. Combined with the biocatalytic reaction that produces H2O2 by glucose oxidase, the strategy of biocatalytic-induced size conversion provides a new way for sensing glucose by RLS technique. The method exhibits good performance with high selectivity, a low detection limit (20nM) and excellent stability both in the buffer and serum samples. The assay shows great potential for versatile application of detecting various substrates which generate H2O2 by using their corresponding oxidases.

Glutathione-Protected Hierarchical Colorimetric Response of Gold Nanoparticles: a Simple Assay for Creatinine Rapid Detection by Resonance Light Scattering Technique

Although numerous methods have been reported for the analysis of creatinine in human serum, the development of a simple, rapid, and practical sensor still remains a great challenge. In this work, a hierarchical colorimetric sensor was demonstrated based on the anti-aggregation effect of glutathione (GSH)-protected gold nanoparticles (AuNPs). Creatinine molecule could induce the aggregation of AuNPs, and the system could show blue color simultaneously. When GSH was added to incubate with AuNPs in advance, the solution could perform a hierarchical color change corresponding to different concentration of creatinine. Consequently, the change of AuNPs in size resulted in the difference of resonance light scattering (RLS) intensity and the quantitative detection of creatinine could be achieved. Meanwhile, the determination of creatinine in human serum could be attained with a detection limit of 1.21 μM, and the colorimetric sensor could be applied to detect creatinine in human serum successfully in a wide range from 10 to 1000 μM. As above, the creatinine in human serum could be distinguished using proper concentration of GSH. More practically, we could identify if the sample exceeded or below the critical value with our naked eye. This sensing proposal was accompanied with prominent simplicity, speediness, and practicability clinically.

Sensitive Determination of Proteins with Naphthol Green B by Resonance Light Scattering Technique

A new quantitative determination method for trace proteins using naphthol green B (NGB) by resonance light scattering (RLS) spectroscopy has been developed. The method is based on the interaction of protein and NGB at pH 3.00, which causes a substantial enhancement of the resonance scattering signal of NGB in the wavelength range 300–550 nm with the maximum RLS at 392.0 nm. Under optimum conditions, the linear range is 0.010–28.2 μg/ml for bovine serum albumin (BSA) and 0.010–31.3 μg/ml for human serum albumin (HSA). The detection limits (S/N=3) are 8.2 ng/ml for BSA and 7.9 ng/ml for HSA, respectively. There is little or no interference from amino acids, most of the metal ions, or other coexisting substances. The easy-to-use method, with high sensitivity and good reproducibility, was satisfactorily applied to the determination of total protein in human serum samples. The determination results for human serum samples are identical to those provided by clinical physicians.

Binding investigation on the interaction between Methylene Blue (MB)/TiO2 nanocomposites and bovine serum albumin by resonance light-scattering (RLS) technique and fluorescence spectroscopy

The interaction between Methylene Blue (MB)/TiO2 nanocomposites and bovine serum albumin (BSA) was investigated by resonance light scattering (RLS), fluorescence, three-dimension spectra and UV–vis absorbance spectroscopy. Several factors which may influence the RLS intensity were also investigated before characterizing MB/TiO2–BSA complex. It was proved that the mechanism of MB/TiO2 nanocomposites binding to BSA was mainly a result of the formation of MB/TiO2–BSA complex. The binding constant of MB/TiO2–BSA is 0.762×10−5Lmol−1 at 298K. By calculating the binding constant at different temperature, the thermodynamic parameters ΔH, ΔG, and ΔS can be observed and deduced that the hydrophobic interactions played an important role to stabilize the complex. The distance r (3.73nm) between donor (BSA) and acceptor (MB/TiO2) was obtained according to fluorescence resonance energy transfer (FRET). The binding site for MB/TiO2 on BSA was mainly located in sub-domain IIA. The UV–vis absorbance, circular dichroism and three dimension fluorescence have also been used to investigate the effect of MB/TiO2 on the conformation of BSA.

Study on the Interaction between Quinine Sulfate and DNA by Multiple Spectral Methods and Their Analytical Applications

The interaction of quinine sulfate (QS) and DNA has been investigated by spectra methods including fluorescence spectroscopy and resonance light scattering (RLS) technique in aqueous solutions. The QS showed an obvious decrease of fluorescence intensity upon the addition of trace amounts of DNA, and the quenching mechanism was suggested to be static quenching according to the Stern-Volmer equation. Under the acidic condition of pH 2.5, the quenched fluorescence intensity of the QS-DNA system was linearly dependent on the concentration of ctDNA ranging from 0.02 to 2.5 mg/L. The interaction between QS and DNA as well as the detection of DNA was further confirmed by RLS technique, and the results showed that enhanced RLS intensity was linearly related to the concentration of ctDNA from 0.01 to 3.5 mg/L. Therefore, two spectral methods for the detection of ctDNA have been established with the use of a QS small molecular probe.

Investigation on the Interaction between Cyclophosphamide and Lysozyme in the Presence of Three Different Kind of Cyclodextrins: Determination of the Binding Mechanism by Spectroscopic and Molecular Modeling Techniques

The interactions between cyclophosphamide (CYC) and lysozyme (LYZ) in the presence of different cyclodextrins (CDs) were investigated by UV absorption, fluorescence spectroscopy, circular dichroism (CD), and molecular modeling techniques under imitated physiological conditions. The UV absorption results showed the formation of complexes between CYC and LYZ in the presence of different CDs. Fluorescence data show that CYC has a stronger quenching effect on LYZ, and the red shifts suggested that the microenvironment of Trp residues was changed and became more hydrophilic. The interaction of CYC with LYZ and quenching properties of the complexes caused strong static fluorescence quenching in binary and ternary systems. The binding affinities as well as the number of binding sites were obtained from interaction between CYC and LYZ in the presence of different CDs as binary and ternary systems by modified Stern-Volmer plots. The Resonance Light Scattering (RLS) technique was utilized to investigate the effect of drug and CDs on conformational changes of LYZ as separate and simultaneous. The results suggested that the enhancement of RLS intensity was attributed to the formation of a complex between drug and protein in absence and presence of CDs. The effect of CYC and cyclodextrins on the conformation of LYZ was analyzed using synchronous fluorescence spectroscopy. Our results revealed that the fluorescence quenching of LYZ originated from the Trp and Tyr residues, and demonstrated conformational changes of LYZ with the addition of CYC and CDs. The molecular distances between the donor (LYZ) and acceptor (CYC and CDs) in binary and ternary systems were estimated according to Forster’s theory and showed static quenching for protein with CYC in the presence of CDs. The CD spectra indicated that the binding of the CYC induced secondary structural changes in LYZ in binary and ternary systems. Molecular modeling suggested the binding sites of CYC in the ternary systems differ from those in the binary systems. estimated the distance between CYC and Trp residues in binary and ternary systems in the presence of CDs and confirmed the experimental results.

Investigation on the Interaction Between Anthracyclines and DNA in the Presence of Quercetin by Resonance Light Scattering Technique and Its Analytical Application

Investigation on the Interaction Between Anthracyclines and DNA in the Presence of Quercetin by Resonance Light Scattering Technique and Its Analytical Application

Determination of Human Serum Albumin with Tetra-amino Copper Phthalocyanine by Resonance Light Scattering Technique

Determination of Human Serum Albumin with Tetra-amino Copper Phthalocyanine by Resonance Light Scattering Technique

Quantitative Detection of Proteins by [Co(NH3)6]3+-DNA Probe of Resonance Light Scattering Technique

[Co(NH3)(6)](3+)-DNA complex produces strong electrical force with proteins, which results in strong enhancement of resonance light scattering intensity. Resonance light scattering intensity at 346 nm was proportional to the concentration of bovine serum albumin in the range of 0.05-1.3 mu g/mL. The limit of determination for bovine serum albumin has obtained at nanogram level. The method is applied to the assay of bovine serum albumin and good results have been obtained compared with custom measure methods. A sensitive, accurate and convenient new analysis method for micro-determination of proteins is established.

Determination of rhodium by resonance light-scattering technique coupled with solid phase extraction using Rh(III) ion-imprinted polymers as sorbent

A resonance light-scattering method (RLS) for the determination of Rh(III) was initially developed, based on the reaction among Rh(III), WO42− and ethylrhodamine B. The method possesses high sensitivity, but lacks selectivity. Therefore, a Rh(III) ion-imprinted polymer (IIP), prepared by precipitation polymerization using 2-(allylthio)nicotinic acid (ANA) as functional monomer, was used as sorbent to construct a ion-imprint based solid-phase extraction (IIP-SPE) method for separation of rhodium from complicated matrices prior to its determination by RLS. The experimental parameters affecting the extraction efficiency and selectivity of IIP-SPE were studied carefully. Under the optimal conditions, the IIP-SPE column with the enrichment factor (EF) of 10 could be used at least 20 times without decreasing its extraction recovery (above 90%) significantly. The calibration graph for the determination of rhodium by RLS coupled with IIP-SPE procedure was linear in the range of 0.06–1.5ngmL−1 with the detection limit of 0.024ngmL−1. There is no metal ions tested at the concentration below 10ngmL−1 interfered in the determination of 0.8ngmL−1 Rh(III). The proposed IIP-SPE–RLS method was successfully applied to the extraction and measurement of trace rhodium in catalyst, water and geochemical samples with the relative standard deviation (RSD) of less than 4.0% (n=4).

Investigation on the Interaction Between Anthracyclines and DNA in the Presence of Quercetin by Resonance Light Scattering Technique and Its Analytical Application

Resonance light scattering technique has been employed to investigate the interaction between anthracyclines and DNA in the presence of quercetin. Upon binding to DNA, anthracyclines undergo dramatic enhancement in their resonance light scattering intensities, while quercetin goes through no obvious change in its intensity. Once being added into anthracyclines- DNA system, quercetin can induce great difference in resonance light scattering intensities between anthracyclines- DNA-quercetin ternary system and anthracyclines-DNA binary system. Consequently, the DNA binding abilities of anthracyclines can be improved by quercetin. Improved efficiency of quercetin on the interaction between anthracyclines and DNA has been calculated. Under the experimental condition, the improved efficiency values of doxorubicin, epirubicin and mitoxantrone were 38.78%, 28.53% and 16.69%, respectively. Additionally, the weak resonance light scattering intensity of quercetin-DNA system is greatly enhanced by anthracyclines and the enhanced intensity is proportional to the concentration of anthracyclines in the range 0.06-9.0 μg mL-1 for doxorubicin, 0.08-12 μg mL-1 for epirubicin and 0.01-3.0 μg mL-1 for mitoxantrone. The detection limits are 4.7 ng mL-1 for doxorubicin, 5.4 ng mL-1 for epirubicin and 1.4 ng mL-1 for mitoxantrone.

Investigation on the Interaction Between Anthracyclines and DNA in the Presence of Quercetin by Resonance Light Scattering Technique and Its Analytical Application

Resonance light scattering technique has been employed to investigate the interaction between anthracyclines and DNA in the presence of quercetin. Upon binding to DNA, anthracyclines undergo dramatic enhancement in their resonance light scattering intensities, while quercetin goes through no obvious change in its intensity. Once being added into anthracyclines- DNA system, quercetin can induce great difference in resonance light scattering intensities between anthracyclines- DNA-quercetin ternary system and anthracyclines-DNA binary system. Consequently, the DNA binding abilities of anthracyclines can be improved by quercetin. Improved efficiency of quercetin on the interaction between anthracyclines and DNA has been calculated. Under the experimental condition, the improved efficiency values of doxorubicin, epirubicin and mitoxantrone were 38.78%, 28.53% and 16.69%, respectively. Additionally, the weak resonance light scattering intensity of quercetin-DNA system is greatly enhanced by anthracyclines and the enhanced intensity is proportional to the concentration of anthracyclines in the range 0.06-9.0 μg mL-1 for doxorubicin, 0.08-12 μg mL-1 for epirubicin and 0.01-3.0 μg mL-1 for mitoxantrone. The detection limits are 4.7 ng mL-1 for doxorubicin, 5.4 ng mL-1 for epirubicin and 1.4 ng mL-1 for mitoxantrone. Keywords: Circular dichroism spectroscopy, DNA, Detection, Doxorubicin, Epirubicin, Interaction, Mitoxantrone, Quercetin, Resonance light scattering, Ultraviolet visible spectroscopy

A highly sensitive label-free resonance light scattering assay of carcinoembryonic antigen based on immune complexes

As a kind of glycoprotein, carcinoembryonic antigen (CEA) is the important tumor marker for clinical diagnosis of the presence or recurrence of cancer. In this work, a novel label-free resonance light scattering (RLS) spectral CEA assay was developed based on the combination of highly selective immunoreaction and ultrasensitive RLS technique. In Tris–HCl buffer solution (pH 7.5), the specific immunoreaction between CEA antigen and mouse anti-CEA formed immune complexes which had a maximum RLS spectral peak at 389.0nm, with the existence of physiological saline and polyethylene glycol 20,000 (PEG 20,000). Under the optimal conditions, the magnitude of enhanced RLS intensity (ΔIRLS) was proportional to the concentration of CEA in the range from 0.1 to 60ngmL−1, with a detection limit (LOD, 3σ) of 0.03ngmL−1. The characteristics of RLS, the CEA immunocomplex, the immune response, the ratio of CEA antigen and mouse anti-CEA, and the optimum conditions of the immunoreaction have been investigated. The CEA concentrations of 20 serum specimens detected by the developed assay showed consistent results in comparison with those obtained by commercially available enzyme-linked immunosorbent assay (ELISA) kit. And this method has many satisfying merits including label-free, sensitivity and high selectivity.

A label-free method for studying DNA sequence recognition of mitoxantrone based on resonance light-scattering technique

A label-free method for studying DNA sequence recognition of mitoxantrone (MIT) by resonance light-scattering (RLS) technique has been developed in this contribution. Through the RLS spectra, the selective no-covalent interactions between MIT and double-stranded DNA, single-stranded DNA (ssDNA), oligonucleotides were systematically studied. The results of the experiments displayed that MIT had an obvious preference to ssDNA with the K (K(RLS)), 15.16 mmol mg(-1) and the number of binding sites (N), 8.68 × 10(-4) mmol mg(-1). Besides, it was found that MIT had a preference to sequences that were rich in guanine and cytosine bases with K(RLS), 17.29 l mmol(-1) and N, 1.19 × 10(-2) l mmol(-1). The recognition mechanisms were well discussed and by fluorescence method and atom force microscopy, the RLS technique was confirmed to be a reliable method in this study. Compared with other methods, what the RLS strategy displayed was the direct interaction between anticancer drugs and DNA in vitro without the influence of a foreign substance. Thus, it can be a simple, fast and label-free strategy for DNA sequence recognition studies of DNA-targeted anticancer drugs.