Resonance Light Scattering Research Articles

Study on the Interaction between a Novel Ionic Liquid Probe and Anionic Surfactants Using Resonance Light Scattering Spectra and Its Analytical Application

AbstractThe interaction between anionic surfactants (AS) and 1‐hexadecyl‐3‐methylimidazolium bromide [C16mim]Br was studied by using resonance light scattering (RLS) technique, UV‐Vis spectrophotometry and fluorometric methods. In Britton Robinson (BR) buffer (pH 6.0), [C16mim]Br reacted with AS to form supermolecular complex which resulted in enhancement in RLS intensity. Their maximum RLS wavelengths were all at 390 nm. Some important interacting experimental variables, such as the solution acidity, [C16mim]Br concentration, salt effect and addition order of the reagents, were investigated and optimized. Under the optimum conditions, quantitative determination ranges were 0.001–7 μg·mL−1 for dodecyl sodium sulfate (SDS), 0.001–6 μg·mL−1 for sodium dodecylbenzene sulfonate (SDBS) and 0.005–7 μg·mL−1 for sodium lauryl sulfonate (SLS), respectively, while the detection limits were 1.3 ng·mL−1 for SDS, 1.0 ng·mL−1 for SDBS and 5.1 ng·mL−1 for SLS, respectively. Based on the ion‐association reaction, a highly sensitive, simple and rapid method has been established for the determination of AS.

Study on the interaction between hematoporphyrin monomethyl ether and DNA and the determination of hematoporphyrin monomethyl ether using the resonance light scattering technique

The interaction between photosensitizer anticancer drug hematoporphyrin monomethyl ether (HMME) and ctDNA has been studied based on the decreased resonance light scattering (RLS) phenomenon. The RLS, UV–vis and fluorescence spectra characteristics of the HMME–ctDNA system were investigated. Besides, the phosphodiesters quaternary ammonium salt (PQAS), a kind of new gemini surfactant synthesized recently, was used to determine anticancer drug HMME based on the increasing RLS intensity. Under the optimum assay conditions, the enhanced RLS intensity was proportional to the concentration of HMME. The linear range was 0.8–8.4 μg mL −1, with correlation coefficient R 2 = 0.9913. The detection limit was 0.014 μg mL −1. The human serum samples and urine samples were determined satisfactorily, which proved that this method was reliable and applicable in the determination of HMME in body fluid. The presented method was simple, sensitive and straightforward and could be a significant method in clinical analysis.

Rapid and sensitive determination of proteins with Eriochrome Red in the presence of anionic surfactant by multi-spectroscopic methods

A new high-sensitivity detection of protein assay at the nanogram level is proposed based on multi-spectroscopic methods including resonance light scattering (RLS), atomic force microscopy (AFM), ultraviolet spectra (UV) and fluorescence spectra etc. Under the optimum conditions, the amplified RLS signals of anionic azo dyes Eriochrome Red B (ERB) in the presence of anionic surfactant sodium dodecyl sulphonate (SDS) was in proportion to the concentration of proteins in the range of 0.0–3.5 mg L −1 and 3.5–12.5 mg L −1 for bovine serum albumin (BSA), 0.0–2.0 mg L −1 and 2.0–8.0 mg L −1 for human serum albumin (HSA). The detection limits were 4.2 ng mL −1 and 2.7 ng mL −1, respectively. The method was satisfactorily applied to the measurement of total protein in human serum samples and a high-sensitivity was achieved.

Determination of anionic surfactant in surface water by resonance light-scattering technology

A sensitive and rapid method, without any extraction procedure, for the determination of the anionic surfactant expressed in the terms of sodium dodecyl benzene sulfonate (SDBS) by the resonance light scattering (RLS) technique is described in this paper. In the pH value 3.0 Britton-Robinson (BR) buffer, Victoria blue B (VBB) reacted with SDBS and produced large particles which resulted in the remarkable enhancement of the RLS intensity of VBB. The enhanced RLS intensity of the assay system was proportional to the concentration of SDBS in the range of 0.08–3.0 mg L–1 and the correlation coefficient was r = 0.9996. The detection limit was 0.013 mg L–1. This method was applied to determine the anionic surfactant in the surface water samples and satisfactory results were obtained. The reaction mechanism was also studied and the interaction between VBB and SDBS was mainly governed by electrostatic effect and the π–π stacking effect.

An Instrument-Based Screening Assay for DNA-Targeted Anticancer Drugs Using Resonance Light Scattering

DNA is a valid drug target for development of target-based therapeutics against cancer. Screening DNA-targeted anticancer drugs is a key process for the research and development of new anticancer drugs. The traditional anticancer drug screening methods, including animal experiments and cell-based screening assays, have unavoidable drawbacks. In this contribution, the new instrument-based screening assay for DNA-targeted anticancer drugs in vitro using resonance light scattering (RLS) technique was proposed. The experiments suggested that the increment of RLS intensity was directly proportional to the antitumor effect of anticancer drugs. Therefore, it was intuitive to obtain the sequence of the antitumor activity of four anticancer drugs without data processing as follows: mitoxantrone (MIT) > pirarubicin (PIR) > daunorubicin (DAU) > doxorubicin (DOX) by RLS screening spectra. Moreover, the apparent equilibrium constant (K) was 1.23 x 10(4), 2.22 x 10(4), 4.66 x 10(4) L/mol for DOX, DAU, and PIR, respectively. The inhibitory concentration 50 (IC50) was 0.148, 0.102, 0.025, 0.013 micromol/L for DOX, DAU, PIR, MIT, respectively. Therefore, the antitumor effect of four drugs was as follows: MIT > PIR > DAU > DOX, which was in good agreement with the result obtained from RLS screening assays. The mechanism between DNA and anthracycline drugs was investigated using UV-vis spectroscopy, fluorescence spectroscopy, and electrophoresis experiments. The proposed assay is a rapid, intuitive, and easy-to-conduct bioassay with good accuracy and reproducibility.

Direct Determination of Urinary Lysozyme Using Surface Plasmon Resonance Light-Scattering of Gold Nanoparticles

The purpose of this study was to establish a simple and sensitive analytical method for lysozyme using Plasmon Resonance Light-Scattering (PRLS) technique with Gold Nanoparticles (AuNPs) as the probe. Nanomolar level of lysozyme induced AuNPs aggregation with enhanced PRLS. For 1.4 nM citrate-capped AuNPs (13 nm in diameter), the linear range of the calibration curve was 15-50 nM with a detection limit of 13.1 nM for lysozyme. Six nanomolar lysozyme can produce an observable PRLS enhancement. Most potential interfering substances present in urine had a negligible effect on the determination. The interference from human serum albumin in the urinary sample can be reduced by precipitating the albumin with ethanol at pH 4.8-4.9. The 90.1-118.2% recovery was achieved for 8 individual lysozyme-spiked urinary samples. This simple and sensitive method for lysozyme does not require sample clean-up and AuNPs modification, thus provided an alternative for urinary lysozyme determination.

Interaction between the fluorinated amphiphilic copolymer poly(2,2,3,4,4,4-hexafluorobutyl methacrylate)-graft-poly(SPEG) and DNA

A synthesized copolymer, synthesized from HFMA (hexaflurobutyl methacrylate) and SPEG (PHFMA-g-PSPEG), was synthesized. PHFMA-g-PSPEG intercalated to the DNA base pair via a strong hydrophobic force, and this was conformed by ultraviolet spectroscopy, transmittance measurements, micropolarity measurements, resonance light scattering (RLS) spectroscopy, and particle size measurements. The copolymer was used as a new probe to detect DNA according to the RLS technique. The hydrophobic interaction between PHFMA-g-PSPEG and DNA significantly enhanced the RLS signal, and the enhanced RLS intensity at 422 nm was proportional to the nucleic acid concentration within the range of 0.09–0.90 mg/L with a detection limit (3σ) of 4.0 μg/L. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

DNA对Ru(bpy)2(dppx)2+-SDS体系共振光散射的猝灭作用及其应用

The resonance light scattering (RLS) spectra of Ru (bpy) 2 (dppx) (superscript 2+)-SDS-DNA (bpy=2, 2'-bipyridine; dppx=7, 8-dimethyl-dipyrido [3, 2-a: 2', 3'-c] phenazine) system was studied. The results show that the solution of Ru (bpy) 2 (dppx) (superscript 2+)-SDS exhibits a high RLS signal in the presence of the premicellar aggregation of an anionic surfactant, sodium dodecyl sulphate (SDS), and adding DNA in the solution of Ru (bpy) 2 (dppx) (superscript 2+)-SDS results in the quenching of the RLS. The mechanism of the reaction was explored. Based on the quenching effect of DNA on the RLS of Ru (bpy) 2 (dppx) (superscript 2+)-SDS system, a novel RLS method for the determination of DNA was proposed. Under optimal conditions, the quenched intensity of RLS at 393 nm is proportional to the concentration of DNA. The linear range of the determination is 0.01~1.2 mg/L. The detection limit is 1.5 μg/L. This method was successful applied to the determination of DNA in synthetic and real samples.

Use of Gemini surfactant in a one-step ellagic acid assay by resonance light scattering technique

Ellagic acid (EA) reacted with Gemini zwitterionic surfactant, phosphodiesters quaternary ammonium salt (PQAS), and formed fine particles which produced strong enhancement in intensity of resonance light scattering (RLS). The effects of several factors on the RLS signal, such as pH, ionic strength, PQAS concentration and so on, were optimized. The relationship between enhanced RLS intensity and EA concentration was constructed. A novel and rapid method for the determination of EA was built. The linear range of this method was 0.016–4.0 μg mL −1 and the detection limit was 13.9 ng mL −1. Under the optimum conditions, the proposed method was applied to determine EA in body fluids with the results of quantitative recoveries between 98.4–101.4% in human serum samples and 99.1–102% in human urine samples. This method characterized by low limit detection is very sensitive and the cost is low, and constitutes a fast one-step procedure which requires only measuring the RLS intensities. The mechanism of the reaction was also studied. This investigation could contribute to the research on the delivery and release of bioactive molecules by Gemini surfactants.

Enhancement of J Aggregation of Zinc Tetraphenylporphyrin in Water/Ethanol Binary Solution in the Presence of Cyclodextrin

An aggregation behavior of zinc tetraphenylporphyrin (ZnTPP) in water/ethanol binary mixture in the presence of cyclodextrins was investigated by means of steady-state absorption, fluorescence, and resonance light scattering (RLS) spectra. In absorption spectra, only broad Soret band at 422 nm was observed in the absence of γ-cyclodextrin (γ-CD), which indicates that ZnTPP exists as weakly bound random-structure aggregates. As the γ-CD concentration increased, a satellite peak, that is characteristic to J aggregate, appeared at around 450 nm. In RLS spectra, the intensity of the J band was enhanced with increasing γ-CD concentrations. In the atomic force microscopy (AFM) image, rod-shape feature was observed, and its height and width were 1.5 nm and 30 nm, respectively.

Photoprotective role of the xanthophyll cycle studied by means of modeling of xanthophyll–LHCII interactions

The problem of photoprotection associated with the xanthophyll cycle is addressed by examination of effects of exogenous violaxanthin and zeaxanthin on isolated antenna complex LHCII. Analysis of electronic absorption spectra suggests multiple sites of binding of violaxanthin and zeaxanthin to the protein environment. Xanthophyll binding results in enhancement of excitonic bands at ca. 530 and 740 nm, as concluded on the basis of Resonance Light Scattering spectra. The energy states attributed to these excitonic bands are concluded to quench singlet excitations. Fluorescence Lifetime Imaging Microscopy shows that both xanthophylls, but in particular zeaxanthin, promote formation of supramolecular structures characterized by extremely low fluorescence yield. Photoprotective meaning of the xanthophyll cycle is concluded to be primarily based upon role of zeaxanthin in promoting formation of supramolecular structures of LHCII characterized by high rate of energy dissipation.

Detection of Newcastle disease virus with quantum dots-resonance light scattering system

A sensitive QDs-based RLS assay method for the detection of Newcastle disease virus (NDV) antibody has been developed. CdTe quantum dots (QDs) were conjugated with Newcastle disease virus and used as RLS-based probes to detect NDV antibody. The electrostatic interaction between CdTe QDs and NDV resulted in enhanced resonance light scattering (RLS) signal characterized at 555 nm. Upon the addition of NDV antibody, QDs–NDV formed dispersive immunocomplex that can decrease the RLS signal. The decreased RLS intensity at 555 nm (Δ I RLS) was linearly proportional to the concentration of NDV antibody ( C anti-NDV) in the range of 0.5–50 ng/mL, with correlation coefficient of 0.974 and detection limit of 0.1 ng/mL under the optimization conditions. The proposed method was applied to the determination of NDV antibody in spiked samples with satisfactory results.

Aggregation behavior of tetrakis(N, N′, N″, N‴-tetramethyl tetra-2,3-pyridino)porphyrazine copper(II) and its interaction with ct-DNA: a thermodynamic approach

The association behavior of tetrakis( N , N ′, N ″, N ‴-tetramethyl tetra-2,3-pyridino)porphyrazine copper(II) ([ Cu(II) 2,3- tmtppa ]4+) was investigated in aqueous solutions at 25 °C and various ionic strengths using optical absorption and resonance light scattering (RLS) spectroscopies. The results show that ([ Cu(II) 2,3- tmtppa ]4+) does not have any affinity for aggregation due to increasing of salt concentration and exists as monomers even in homogeneous aqueous solutions of high ionic strengths (more than 1 M NaCl ). Interaction of ([ Cu(II) 2,3- tmtppa ]4+) with calf thymus DNA has also been studied in 1 mM aqueous phosphate buffer of pH 7.0, by optical absorption and RLS spectroscopies, and thermal denaturation experiments. The appearance of hypochromicity of less than 10% and bathochromicity shift of Δλ ≤ 2 nm in UV-vis spectra of ([ Cu(II) 2,3- tmtppa ]4+), increasing of thermal melting point of DNA, and no change in RLS spectra of porphyrazine due to interaction with DNA, represent the minor outside groove binding mode without any stack aggregate formation. The thermodynamic of the binding of ([ Cu(II) 2,3- tmtppa ]4+)-DNA also has been studied. The binding constant (K) was obtained by analysis of the optical absorption spectra of the complex at various DNA concentrations using SQUAD software. The value of K was estimated to be 2.34 × 105 ± 0.06 M -1 at 25 °C. The thermodynamic parameters were calculated by van't Hoff equation. The enthalpy and entropy changes were 41.83 ± 3.28 kJ/mol and 242.08 ± 9.88 J/mol.K at 25 °C, respectively. The results indicate that the process is entropy-driven and suggest that hydrophobic interactions are the main driving forces for the complex formation. Increasing of the ionic strength due to addition of NaCl destabilized porphyrazine-DNA complexes, indicating the competition of Na + ions with porphyrazine complexes for occupation of minor groove binding sites.

Antibody microarray-based strategies for detection of bacteria by lectin-conjugated gold nanoparticle probes

In this paper, we propose an effective protocol for bacterial detection using antibody microarray-based strategies with gold nanoparticle probes. In this approach, bacteria are captured by immobilized IgGs on the microarray spots. The capturing events are marked by attachment of lectin (e.g. Ricinus Communis Agglutini (RCA) and Concanavalin A (ConA)) conjugated gold nanoparticles followed by silver deposition for signal enhancement. The detection principle is resonance light scattering (RLS). Using this technique, highly selective discrimination of bacterial strain types (i.e., gram-negative, gram-positive and fungus) down to 10 3 cells per assay with a dynamic range of nearly three orders of magnitude are demonstrated. In addition, the capturing process can be inhibited by lipopolysaccharides (LPS), which gives further evidence of the binding mechanism. Furthermore, antibacterial assay with antibacterial drugs (amoxicillin and vancomycin) demonstrates that the approach enables to detect antibacterial efficiency as well as derive MIC (minimum inhibitory concentration) plots.

Analysis of interaction between tamoxifen and ctDNA in vitro by multi-spectroscopic methods

Multi-spectroscopic methods including resonance light scattering (RLS), ultraviolet spectra (UV), fluorescence spectra, (1)H NMR spectroscopy, coupled with thermo-denaturation experiments were firstly used to study the interaction of antitumor drug tamoxifen (TMX) with calf thymus (ctDNA) in acetate buffer solutions (pH 4.55). The interaction of TMX with ctDNA could cause a significant enhancement of RLS intensity, the hyperchromic effect, red shift of absorption spectra and the fluorescence quenching of TMX, indicating that there is an inserting interaction between TMX and ctDNA. This inference was confirmed by (1)H NMR spectroscopy. The chemical shift of the benzene proton changes significantly which indicates that TMX could insert into the base pairs of ctDNA. These studies are valuable for a better understanding the mode of TMX-ctDNA interaction further, which are important and useful for designing of new ctDNA targeted drug. And the antitumor drug TMX inserted directly into ctDNA in vitro, which can provide a lot of useful information to explore the development of new and highly effective anti-cancer drugs.

Screening Kinase Inhibitors with a Microarray-Based Fluorescent and Resonance Light Scattering Assay

In this technical note, a microarray-based spectroscopic assay with two readout principles, fluorescence and resonance light scattering (RLS), for screening kinase inhibitors has been reported. In this assay, the phosphorylation and inhibition events are marked by biotinylated antiphosphoserinen/antiphosphotyrosine antibodies, and gold nanoparticles are attached to the antibodies by standard avidin-biotin chemistry followed by silver deposition for RLS signal enhancement. The avidin conjugated fluorescein is used as a fluorescent probe. Assays for both serine kinase, the alpha-catalytic subunit of cyclic adenosine 5'-monophosphate (cAMP) dependent protein kinase (PKA), and tyrosine kinase, leukocyte-specific protein tyrosine kinase (LCK), have been developed. The utility of this assay to high-throughput screening was demonstrated with a commercial inhibitor library, a collection of 80 kinase inhibitors, and satisfactory results were obtained. In addition, quantitative determination of binding strength and the inhibiting type (type I) of these inhibitors are also demonstrated by the adenosine 5'-triphosphate (ATP) competing assays.

Spectroscopic investigations on the binding of dibazol to bovine serum albumin

Abstract The characteristics of the binding reaction of dibazol to bovine serum albumin (BSA) were investigated by fluorescence, UV–vis, resonance light scattering (RLS) and Fourier transform infrared (FT-IR) spectroscopy. Results show that dibazol causes the fluorescence quenching of BSA through a static quenching procedure. The binding constants for the formation of a complex between dibazol and BSA are 0.83, 1.23 and 1.62 × 105 mol−1 L at 295, 302 and 309 K, respectively. Positive values of thermodynamic parameters namely enthalpy change (ΔH) and entropy change (ΔS) indicate that the interaction between dibazol and BSA is driven mainly by hydrophobic forces. It seems that the binding is spontaneous at standard state for the change in standard Gibbs free energy (ΔG) value is negative. The binding distance between BSA and dibazol was calculated to be about 4.28 nm according to the Forster theory. The site marker competitive experiments confirmed that the binding of dibazol to BSA primarily occurred in site I of BSA. In addition, the effect of dibazol on the conformation of BSA was also analyzed by using synchronous fluorescence and FT-IR spectroscopy.

Ultrasensitive determination of serum albumin using resonance light scattering based on ZnS-polyacrylic acid nanoparticles

ZnS-polyacrylic acid (ZnS-PAA) was prepared by an in situ polymerization method using nano-ZnS as core in the presence of acrylic acid (AA), and ZnS-PAA nanoparticles was characterized by ultraviolet spectrometry (UV) and transmission electron microscopy (TEM). Based on the significant increase of the resonance light scattering (RLS) intensity with the interaction between nanoparticles and serum albumin, RLS method was developed for the sensitive determination of serum albumin (BSA and HSA). Under optimum conditions, the change of the intensity (DeltaI) of the RLS spectra at lambda=392nm was linearly proportional to the concentration of BSA and HSA. The linear range was 1-100ngmL(-1) for HSA and 1-120ngmL(-1) for BSA, and the limit of detection (LOD) was 0.4ngmL(-1) for HSA and 0.5ngmL(-1) for BSA. This method proved to be very sensitive, rapid, simple and tolerant of most interfering substances.

Study on interaction between cationic polystyrene nanoparticles and DNA, and the detection of DNA by resonance light scattering technology

Monodisperse cationic polystyrene nanoparticles (PS-NPs) were prepared through microemulsion polymerization. Photon correlation spectrometry and transmission electron microscopy revealed that these cationic PS-NPs have a z-average particle size of 30 nm. Size analysis, circular dichroism spectroscopy and transmission electron microscopy indicate that the PS-NPs nanoparticles undergo electrostatic interaction with DNA to form a PS–DNA complex that obviously enhances the resonance light scattering (RLS) signal. A method is presented where the PS-NPs act as a probe for the detection of DNA by RLS. The method is convenient, sensitive, reproducible, and enables high-throughput. The PS-NPs are inexpensive and exhibit low toxicity.

Screening DNA-targeted anticancer drug in vitro based on the drug-conjugated DNA by resonance light scattering technique

A sensitive and reliable assay has been developed to directly screen DNA-targeted anticancer drugs in vitro via using resonance light scattering (RLS) technique. The results of experiments displayed that the increment of RLS intensity was directly proportional to the antitumor effect of anticancer drugs. Through the RLS spectra, the activities of four drugs have been demonstrated as mitoxantrone (MIT) > epirarubicin (EPI) > daunorubicin (DAU) > adriamycin (ADM). However, to further verify the activities of the above four drugs, binding constant ( k) for each of them has been calculated by RLS technique as follows: k RLS (MIT, 8.75 × 10 5 L mol −1) > k RLS (EPI, 6.58 × 10 5 L mol −1) > k RLS (DAU, 4.79 × 10 5 L mol −1) > k RLS (ADM, 3.82 × 10 5 L mol −1). Also, this RLS assay result was validated by seasoned vitro screening methods for anticancer drugs. In all, the proposed RLS is not only a simple, sensitive, objective and straightforward method, but also it is an unprecedented assay for primarily screening DNA-targeted anticancer drugs.