Resonance Light Scattering Enhancement Research Articles

High sensitive assay of formaldehyde using resonance light scattering technique based on carbon dots aggregation

Formaldehyde (FA) is widely used in industry and also common in daily life. Finding an efficient method to determine FA is quite an industrial challenge. Herein, a novel method based on a resonance light scattering (RLS) technique was developed for the detection of FA with high sensitivity. Carbon dots (CDs) were used as RLS probes. CDs were obtained via one-pot solvothermal treatment from o-phenylenediamine. CDs showed yellow fluorescence with a quantum yield of 0.41. Due to the multiple amino groups on the surface of CDs, FA can be captured easily by formation of a covalent C = N bond based on the Schiff-base reaction. Owing to the covalent crosslinking, CD nanoparticles aggregated, and even formed precipitate. The aggregation of CDs induced RLS enhancement, where the RLS increment was linearly related to the concentration of FA ranging from 4 nM to 1.6 mM, with a limit of detection (LOD) of 1.6 nM. In comparison with many previous reports, the present RLS method showed a wider linear range and lower LOD. Furthermore, the RLS system was successfully used to detect FA in real food samples. The proposed system has prospective applicability in the detection of FA in food fields.

A hybrid ratiometric probe for glucose detection based on synchronous responses to fluorescence quenching and resonance light scattering enhancement of boronic acid functionalized carbon dots

Enzymatic assay for glucose as a traditional protocol has always been suffering from cost-expensiveness and time-consumption, and instability and denaturation of glucose oxidase. Boronate affinity chemosensors currently became the research hotspots in the field of sugar sensing. Herein a simple but effective hybrid ratiometric platform has been addressed for glucose detection based on synchronous fluorescence quenching and resonance light scattering (RLS) enhancement of boronic acid functionalized carbon dots (C-dots). The C-dots was fabricated by one step “synthesis-modification integration” strategy using 3-aminophenyl boronic acid and sodium citrate as precursors. The retained boronic acid groups on the C-dots surface can assembly with cis-diols group of glucose to form coordination compound, which resulted in the fluorescence quenching of C-dots by aggregation states. Also, the aggregation among C-dots simultaneously induced the great RLS enhancement of C-dots because of the existence of two pairs of cis-diols groups. A hybrid ratiometric chemosensor for glucose was therefore constructed. Significantly, due to the inert surface of the C-dots, this ratiometric probe can assay down to 10 μM glucose without the interference from a variety of biomolecules and metal ions in real water samples, and exhibits an excellent selectivity over other analogues. The present sensing system has been successfully applied to the assay of glucose in urine samples. It displays great promise as a practical platform for glucose detection due to its simplicity and effectiveness.

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.

Simultaneous determination of five fluoroquinolones by the selective high performance liquid chromatography associating with sensitive resonance light scattering and mechanism study

A novel and selective high performance liquid chromatography (HPLC) technique incorporating resonance light scattering (RLS) detection approach was developed for the determination of five fluoroquinolones (FQS) synchronously for the first time, including enoxacin (ENO), ofloxacin (OFLX), lomefloxacin (LMLX), gatifloxacin (GFLX) and sparfloxacin (SPLX). In pH4.4 Britton - Robinson (BR) buffer medium, the ENO, OFLX, LMLX, GFLX, SPLX separated by HPLC reacted with erythrosine (ERY) to form 1:1 ion-association complexes, which led to significant enhancement of RLS. The maximum RLS wavelength of the ion-association complexes located at 330nm. The detection limits of ENO, OFLX, LMLX, GFLX, SPLX were 5.1ng·mL−1, 3.1ng·mL−1, 4.2ng·mL−1, 3.8ng·mL−1, 17.5ng·mL−1 respectively at a signal-to-noise ratio of 3. In this work, the optimum experimental conditions and reaction mechanism were investigated in detail. The proposed method could be applied to the determination of ENO, OFLX, LMLX, GFLX, SPLX in water samples synchronously and the results were satisfactory.

Determination of methylene blue by resonance light scattering method using silica nanoparticles as probe

A simple and novel method was developed to determine methylene blue (MB) by resonance light scattering (RLS) using silica nanoparticles (SiO2NPs) as the probe. It was found that MB could enhance the RLS intensity of SiO2NPs. Moreover, the increase in RLS intensity was linear with the concentration of MB over the range of 0.01–3.0μgmL−1. The limit of detection (LOD) was as low as 4.36ngmL−1 (3σ) and the relative standard deviation (RSD) was 2.4% (n=6). Under the optimum experimental conditions, this proposed method was successfully applied for the determination of MB in aquaculture samples with recoveries between 96.3% and 107%. Possible mechanisms for the RLS enhancement of SiO2NPs in the presence of MB were also discussed.

Binding site identification of metformin to human serum albumin and glycated human serum albumin by spectroscopic and molecular modeling techniques: a comparison study

The interaction between metformin and human serum albumin (HSA), as well as its glycated form (gHSA) was investigated by multiple spectroscopic techniques, zeta potential, and molecular modeling under physiological conditions. The steady state and time-resolved fluorescence data displayed the quenching mechanism of HSA–metformin and gHSA–metformin was static. The binding information, including the binding constants, number of binding sites, effective quenching constant showed that the binding affinity of metformin to HSA was greater than to gHSA which also confirmed by anisotropy measurements. It was determined that metformin had two and one set of binding sites on HSA and gHSA, respectively. Far-UV CD spectra of proteins demonstrated that the α-helical content decreased with increasing metformin concentration. The zeta potential and resonance light scattering (RLS) diagrams provided that lower drug concentration induced metformin aggregation on gHSA surface as compare to HSA. The increase in polarizability was one of the important factors for the enhancement of RLS and the formation of drug/protein complexes. The zeta potential results suggested that both hydrophobic and electrostatic interactions played important roles in the protein–metformin complex formation. Site marker experiments and molecular modeling showed that the metformin bound to subdomain IIIA (Sudlow’s site II) on HSA and gHSA.

Determination of metallothioneins by fluorescence and resonance light scattering strategies based on ciprofloxacin–Cu(II) system

Based on ciprofloxacin (CIP)–Cu(II) system, the novel methods for the detection of metallothioneins (MTs) have been developed by fluorescence (FL) and resonance light scattering (RLS) strategies. The FL strategy avoids the label and derivatization steps in common methods, while the RLS strategy can be applied for determining bio-macromolecules and small molecules without native fluorescence. The response signals linearly correlated with the concentration of MTs over the ranges of 1.03×10−8–1.23×10−6molL−1 for FL, and of 2.56×10−7–1.54×10−6molL−1 for RLS. The limits of detection (LOD) are 3.1×10−9molL−1 for FL and 7.68×10−8molL−1 for RLS. This study represents the comparison of these two methods using the same CIP–Cu2+–MTs system. They not only allow practical application for MTs detection but also serve as a potential choice for the operators according to their concrete needs. In addition, the mechanisms for FL and RLS enhancement of the system were also discussed.

Resonance light scattering technique for determination of polychlorinated biphenyls with silver nanoparticles

In this paper, a simple and novel method for the determination of polychlorinated biphenyls (PCBs), using silver nanoparticles (AgNPs) as a resonance light scattering (RLS) probe, is proposed. Under optimized conditions, there existed linear relationships between the enhancing RLS intensity of the system and the concentrations of PCBs in the range 8.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 2,4,4'-trichlorbiphenyl (PCB28), 9.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 2,2',5,5'-tetrachlorbiphenyl (PCB52) and 4.0 × 10(-8) -1.0 × 10(-6) g mL(-1) for 3,3',4,4'-tetrachlorobiphenyl (PCB77). The corresponding detection limits (S/N = 3) were 2.6 × 10(-8) g mL(-1) for PCB28, 3.3 × 10(-8) g mL(-1) for PCB52 and 6.3 × 10(-9) g mL(-1) for PCB77, respectively. Finally, the mechanism of RLS enhancement was also studied. The results indicated that PCBs were adsorbed on the surface of AgNPs to form larger AgNP-PCB aggregates, resulting in the RLS enhancement of the system.

Study on the interaction between a fluorine-containing amphiphilic cationic copolymer and nucleic acid by resonance light scattering technique

A novel fluorine-containing amphiphilic cationic copolymer P(HFMA-St-MOTAC)-g-PEG was synthesized as a new probe to detect DNA based on the RLS technique. The aggregation of P(HFMA-St-MOTAC)-g-PEG on the molecular surface of DNA occurred under pH 4.0–7.0 resulted in an enhanced resonance light-scattering (RLS) peaks at 370 nm, 400 nm, 420 nm and 470 nm. The intensity of resonance light-scattering was found to be proportional to the concentration of DNA. The detection limit was 5.8 μg L −1. It was found that the P(HFMA-St-MOTAC)-g-PEG has strong interaction with DNA as confirmed by the resonance light scattering (RLS) spectroscopy, UV spectra, IR spectra, and TEM.

Investigation on the interaction between tamoxifen and human holo-transferrin: Determination of the binding mechanism by fluorescence quenching, resonance light scattering and circular dichroism methods

The interaction between tamoxifen (TMX) and human serum transferrin (HTF) was for the first time studied at varying pH values by fluorescence spectroscopy, circular dichroism (CD) and resonance light scattering (RLS). The fluorescence spectroscopy experiments were performed in order to study conformational changes, possibly due to a discrete reorganization of tryptophan residues during TMX–HTF binding at varying ligand concentrations, as well as quenching properties of the drug-serum transferrin complex and the differentiation between static and dynamic quenching. The binding affinity and number of binding sites were obtained for the TMX–HTF interaction at different pH. Second derivative fluorescence spectroscopy was employed for monitoring the complex and characterizing the transitions taking place in the environments of tyrosine and tryptophan (mainly tryptophans) in proteins. The variation of the K SV value suggested that hydrophobic and electrostatic interactions were the predominant intermolecular forces stabilizing the complex. The RLS technique was utilized to determine the protein type, and to investigate the effect of anticancer drugs on its determination. This is the first report of its kind. An explanation is also given of the enhancement in RLS intensity, which attributed to the new complex formation between TMX and the protein a self-aggregation process and the formation of a precipitate HTF occurred and a micelle came into being when the amount of TMX was augmented. The great increase of polarizability was one of the important factors for the enhancement of RLS and the formation of complexes. The results from synchronous fluorescence spectroscopy showed that the micro-environment around tryptophan and tyrosine demonstrated a faint red shift. The circular dichroism data revealed that the presence of TMX decreased the α-helix content of HTF and induced the remarkable unfolding of the polypeptides of the protein. This confirmed certain micro-environmental and conformational changes of the HTF molecule. The binding distance ( r) between TMX and the tryptophan residue of HTF was obtained according to the Förster theory of non-radioactive energy transfer. This study on the interaction of drugs with HTF should prove helpful for realizing the distribution and transportation of drugs in vivo, elucidating the action mechanism and dynamics of a drug at the molecular level. It should moreover be of great use for understanding the pharmacokinetic and pharmacodynamic mechanisms of the drug.

Determination of Bovine Serum Albumin by a Resonance Light-Scattering Technique with a New Mixed-Complex La(C7H5O5S)(phen)3+

A new mixed-complex of La(C7H5O5S)(phen)3+ was synthesized. Resonance light-scattering characteristics of the interaction between La(C7H5O5S)(phen)3+ with bovine serum albumin (BSA) were studied. After BSA was added, aggregation of La(C7H5O5S)(phen)3+ on the molecular surface of the bovine serum albumin occurred at the pH 4.5∼6.2, which resulted in an enhanced resonance light-scattering (RLS) peak at 400 nm. The intensity of resonance light-scattering was found to be proportional to the concentration of BSA.

Study on the interaction of nucleic acids with silver nanoparticles—Al(III) by resonance light scattering technique and its analytical application

It is found that Al(III) can further enhance the intensity of resonance light scattering (RLS) of the silver nanoparticles (AgNPs) and nucleic acids system. Based on this, a novel method of determination of nucleic acids is proposed in this paper. Under optimum conditions, there are linear relationships between the enhancing extent of RLS and the concentration of nucleic acids in the range of 1.0 × 10 −9–1.0 × 10 −7 g mL −1, 1.0 × 10 −7–2.0 × 10 −6 g mL −1 for fish sperm DNA (fsDNA), 1.0 × 10 −9–7.0 × 10 −8 g mL −1 for calf thymus DNA (ctDNA) and 1.0 × 10 −9–1.0 × 10 −7 g mL −1 for yeast RNA (yRNA). The detection limits (S/N = 3) of fsDNA, ctDNA and yRNA are 4.1 × 10 −10 g mL −1, 4.0 × 10 −10 g mL −1 and 4.5 × 10 −10 g mL −1, respectively. The studies indicate that the RLS enhancement effect should be ascribed to the formation of AgNPs–Al(III)–DNA aggregations through electrostatic attraction and adsorption bridging action of Al(III). And the sensitivity and stability of the AgNPs–fsDNA system could be enhanced by Al(III).

Determination of protein by resonance light scattering technique using dithiothreitol–sodium dodecylbenzene sulphonate as probe

The resonance light scattering (RLS) spectra of bovine serum albumin (BSA)–dithiothreitol (DTT)–sodium dodecylbenzene sulphonate (SDBS) and its analytical application were investigated. The RLS intensity of this system can be effectively enhanced in the presence of BSA. Based on the enhanced RLS intensity, a simple assay for BSA was developed. The experimental results indicate that the enhanced RLS intensity is proportional to the concentration of BSA in the range from 1.0 × 10 −8 to 7.5 × 10 −7 mol L −1 with the determination limit of 5.0 × 10 −9 mol L −1. The effects of pH, concentration of SDBS and DTT on the RLS enhancement were discussed. Most metal ions have little interference on the determination of BSA. Some synthetic and real samples were analyzed, and the results obtained were in good agreement with those obtained by Bradford method.

Resonance light-scattering spectrometric study of interaction between enzyme and MPA-modified CdTe nanoparticles

This paper described a novel assay of enzyme based on the measurement of enhanced resonance light-scattering (RLS) signals resulting from the electrostatic and coordination interaction of functionalized CdTe nanoparticles with enzyme. The CdTe nanoparticles which were modified with 3-mercaptocarboxylic acid (MPA) have abundant carboxylic groups ( COOH). So the nanoparticles are water-soluble, stable and biocompatible. At pH 8.3 phosphate buffered saline (PBS), the RLS signals of functionalized nano-CdTe are greatly enhanced by bromelain and papain in the region of 220–800 nm characterized by the peak around 318–314 nm, respectively. The optimization conditions of the reaction were also examined and selected. Under the selected conditions, the enhanced RLS intensity is linearly proportional to the concentration of bromelain and papain. The liner range is (0.09–0.9) × 10 −6 mol/L for bromelain and (0.048–0.702) × 10 −6 mol/L for papain. The influences of some foreign substances were also examined. This method can be applied to the determination of enzyme.

Resonance scattering method for the ultrasensitive determination of peptides using semiconductor nanocrystals

Resonance light scattering (RLS) of the functionalized ZnS nanocrystals–peptides system and its analytical application have been studied. The RLS intensity can be efficiently enhanced when various peptides were added. The mechanism of the RLS enhancement of ZnS nanocrystals was discussed. The change of RLS intensity was in proportion to the concentration of peptides. The limits of detection were in range of 2.8–5.7 ng mL −1. Application results to synthetic samples showed simplicity, rapidity, high sensitivity and satisfactory reproducibility of the presented method. Measurements of real samples also give satisfactory results which were in good agreement with those obtained using high performance liquid chromatography (HPLC) and liquid chromatography–mass spectrography (LC–MS) methods.

Investigation of the interaction between curcumin and nucleic acids in the presence of CTAB

It is found that nucleic acid can enhance the resonance light scattering (RLS) enhancement effect of curcumin (CU) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The investigation indicates that in BR (pH 4.3) buffer, both the positive CTAB and negative yeast RNA (yRNA) combine and form a positive large association, then which is bound on the two carbon atoms of the carbonyls of CU through hydrogen bond and hydrophobic force and form CU–CTAB–yRNA ternary complex, resulting in the RLS enhancement of this system. Based on it, a sensitive method for determination of nucleic acids at ng ml −1 is established.

A High-Sensitivity Assay of Nucleic Acids with Tetraphenyl Porphyrin Cobalt Chlorine by Resonance Light Scattering Technique

A novel probe, tetraphenyl porphyrin cobalt chlorine (CoTPPCl), is first applied to determine nucleic acids at the nanogram level based on the measurement of resonance light scattering (RLS) signals, which result from the interaction of CoTPPCl with nucleic acids. Under pH 6.37 conditions, the reaction between CoTPPCl and nucleic acid enhances the weak resonance light scattering (RLS) signal of CoTPPCl, and the enhanced light scattering intensity is proportional to the concentration of nucleic acid. The method is sensitive (3.45 ng/mL for ctDNA), simple (one step and a common fluorimeter), and tolerant of the metal ions and other coexistent substances. The mode of the combination between CoTPPCl and nucleic acids and the reasons for RLS enhancement are clearly clarified. Synthetic samples were determined with satisfactory results.

Determination of bovine serum albumin by a resonance light-scattering technique with the mixed-complex La(Phth)(phen) 3+

A mixed-complex of La(Phth)(phen) 3+ was synthesized. Resonance light-scattering characteristics of interaction between La(Phth)(phen) 3+ with bovine serum albumin (BSA) were studied. When BSA was added, aggregation of La(Phth)(phen) 3+ on the molecular surface of bovine serum albumin occurred in the pH 5.5–6.3, resulted in an enhanced resonance light-scattering (RLS) peak at 360 nm. The intensity of resonance light-scattering was found to be proportional to the concentration of BSA.

Study on the interaction between methylene violet and calf thymus DNA by molecular spectroscopy

The fluorescence and solid surface room temperature phosphorescence (SS-RTP) spectral properties of methylene violet (MV) were investigated. And the factors influencing the phosphorescence emission were discussed. The interaction of MV and ctDNA was studied by molecular spectroscopy. Deduced from the fluorescence, SS-RTP and resonance light-scattering spectral data, there were two different interaction mechanism involved in the whole interaction process depending on the R-values( R: the molar ratio of MV to ctDNA) at pH = 7.56. The value R = 1.9 is the turning point; when R < 1.9, enhanced resonance light-scattering (RLS) was observed, which indicated long range assembly of MV on the ctDNA molecular surface. In this process long-range assembly is the main binding mode. The second process occurs when R > 1.9, where MV intercalated into the ctDNA helix, the intercalative binding is predominant, supported by fluorescence polarization experiment and potassium iodide quenching study. Based on the fluorescence quenched experiment of MV by ct DNA, the binding constant of MV binding to ctDNA was 1 × 106 L/mol, the binding site was 1.0.

The Determination of Deoxyribonucleic Acids with Triadimenol Based on the Enhancement of Resonance Light Scattering

For the first time, triadimenol was used to determine nucleic acid (DNA) using the resonance light scattering (RLS) technique. The RLS of triadimenol was greatly enhanced by DNA in the range of pH 1.6 ∼ 1.9. A resonance light‐scattering peak at 310nm was found, and the enhanced intensity of RLS at this wavelength was proportional to the concentration of DNA. The linear range of the calibration curve was 0 ∼ 9 µg/ml with the detection limit of 24 ng ml− 1. The mechanism studies of the system indicated that the enhanced RLS is due to the aggregation of triadimenol on DNA. The nucleic acids in synthetic samples and in rice seedling extraction were analyzed with satisfactory results. Compared with other methods, this method is convenient, rapid, inexpensive and simple.