Resonance Rayleigh scattering method for the determination of chitosan using erythrosine B as a probe and PVA as sensitization

Antibody-labeled gold nanoparticle based resonance Rayleigh scattering detection of S100B

Traumatic brain injury (TBI) is a sudden brain injury due to an external force that causes a large number of deaths and permanent disabilities every year. S100B has been recognized as a potential objective quantitative biomarker for screening the prognosis of TBI and severe head injury. In this article, an anti-S100B monoclonal antibody was immobilized on cysteamine (Cy) functionalized gold nanoparticles (AuNPs) by EDC-NHS chemistry, which enabled S100B resonance Rayleigh scattering (RRS) detection based on antibody-labeled gold nanoparticles. The prepared conjugates were characterized by ultraviolet-visible spectroscopy (UV-vis), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Based on the specific binding of the antibody and antigen, the RRS intensities at 381 nm and 541 nm wavelengths were significantly enhanced, and thus a dual wavelength overlapping resonance Rayleigh scattering (DWO-RRS) method was established. The scattering intensity of the two overlapping peaks was proportional to the concentration of S100B in the range of 0.05-4.5 ng mL-1 with a detection limit of 0.002 ng mL-1. The proposed DWO-RRS method is time-saving, simple, sensitive, and can be used to determine the concentration of S100B in human serum with satisfactory results, which has a promising application in the early diagnosis of TBI.

Utility of Cilefa Pink B, a foodstuff dye as a fluoro-substrate in the devising of the first facile green Molecular-mass-Related Fluorescence Sensor for quantifying amlodipine in batched material and dosage forms; content uniformity evaluation

This study introduces the first and unique Molecular-mass-Related Fluorescence Sensor as the first fluorimetric strategy for determining amlodipine. An environmentally friendly, single-step, and direct spectrofluorimetric approach was utilized to evaluate the analyte. In an acidic setting, combining the amlodipine medication and the fluorescent dye Cilefa Pink B generated an instantaneous ultra-fluorescent product. An increase in dye response after adding amlodipine was proportional to the molecular weight of the generated complex, as measured at 329 nm. was the idea ofthe applied fluorimetric analysis. The complexing process increased the molecular mass from 879.86 to 1288.739 g mol-1. The medication's range of 0.050-1.00 µg mL-1 is directly correlated with this molecular massenlargement. The ideal settings for the changeable parameters of the system were established through an analysis of the response of the amlodipine-Cilefa Pink B system. Furthermore, the developed sensor complied with ICH (International Council for Harmonization) standards. The sensitivity limits were 0.0139 µg mL-1 (for the detection limit, LOD) and 0.042 µg mL-1 (for the quantification limit, LOQ). Additionally, this method effectively recovered the drug in its original and therapeutic dosage forms. Finally, the proposed process's environmental impact was also assessed through different modern greenness evaluation tools.

Determination of phosphate in food based on molybdenum yellow derivatization coupled with resonance Rayleigh scattering method

This paper proposed a rapid, selective and sensitive molybdenum yellow derivatization coupled with Resonance Rayleigh scattering (MYD-RRS) method for detection of phosphate. Under the acidic condition, phosphate can be selectively transformed to Keggin type of phosphomolybdic acid (PMA, i.e., PMo12O403-) through molybdenum yellow derivatization reaction prior to RRS detection. The PMA can further react with cationic methyl violet (MV) to form larger PMA-MV ion association complexes, generating significant RRS signal. The concentration of phosphate was linearly related to the RRS signal in the range of 8-200 ng/mL, with the determining coefficient (R2) of 0.9973 and the detection limit of 4 ng/mL. The analytical procedure can be completed within 10 min and the RRS signal intensity can remain stable more than 4 h. The method showed good stability toward temperature and time, and good anti-interference capability. The method was applied to the determination of phosphate in real food samples with the recovery of 85-117% and RSD of 1-5.2%. With the advantages of rapidness, high sensitivity and good selectivity, the MYD-RRS method exhibits great potential to the determination of phosphate in food. It also provides an instructive strategy for detection of analytes with weak RRS signal.

Utility of Cilefa Pink B, a food dye in a facile decoration of the first green molecular-size-based fluorescence probe (MSBFP) for determining trimebutine; application to bulk, dosage forms, and real plasma

This research presents the first novel green molecular-size-based fluorescence probe (MSBFP) as a spectroscopic strategy for detecting the Trimebutine drug. The method used a green, one-pot, direct spectrofluorimetric methodology to validate and assess the medication. Trimebutine drug and Cilefa Pink B formed an immediate ultra-fluorescent complex when mixed in an acidic environment. The fluorimetric study relied on Trimebutine's amplification of the dye response, which correlated to the generated complex's molecular size at 361 nm. Upon complexation, the molecular mass has grown from 504.5 to 1384.4 g mol^-1. This growth is proportionally coupled to the drug concentration range of 0.035-1.5 µg mL^-1. The lower and upper limits of the sensitivity varied from 0.010 and 0.029 µg mL^-1, respectively. Trimebutine-Cilefa Pink B complexes were analyzed to determine optimal values for all the tunable system variables. Also, The International Council for Harmonization (ICH) requirements were successfully met by the system. In addition, this method effectively retrieved the drug in the intended pharmaceutical dosages. A significant achievement was using the developed fluorimetric method to monitor the drug of interest in human biofluids. The environmental friendliness of the planned procedure was then evaluated.

A novel liquid crystal resonance Rayleigh scattering spectral probe for determination of trace Cr6

Hexavalent chromium (Cr⁶⁺) has strong oxidizing property and toxicity. It has been identified as a carcinogen with obvious carcinogenic effect by the International Anti-cancer Research Center. Therefore, it has a great significance to establish a simple and sensitive method for Cr⁶⁺. In the solution, liquid crystal (LC) trans, trans-4-(3,4-difluorophenyl)-4'-n-pentylbicyclohexyl (DP) exhibits strong resonance Rayleigh scattering (RRS) effect due to formation DP nanoparticles. It was used firstly as nanoprobe, to establish a simple and sensitive RRS energy transfer (RRS-ET) method for the determination of trace Cr⁶⁺ in water samples. The Cr⁶⁺ reacts with diphenylcarbazide (DCB) to produce purple complex. It is adsorbed on the nanoprobe surface, the purple complex as energy receptor and DP as energy donor to produce RRS-ET phenomenon, to make the RRS signal of 370 nm decreasing. In the range of 3-30 nmol/L Cr⁶⁺, with the increase of concentration, the RRS signal decreased linearly at 370 nm, with a detection limit of 0.49 nmol/L. This new RRS-ET method was applied to the determination of Cr⁶⁺ in water samples, with recovery of 96.0-104.7% and the relative standard deviation (RSD) of 4.44-9.98%.

A resonance Rayleigh scattering method for sensitive detection of chitosan based on supramolecular complex and mechanism study

A convenient and sensitive resonance Rayleigh scattering (RRS) method for the detection of chitosan (CTS) has been developed via forming Cu-Zn supramolecular complex by complexation reaction, hydrophobic force and electrostatic attraction. The microstructure of the complex was characterized by FT-IR, zeta potential, scanning electron microscope (SEM), UV-vis and RRS. Furthermore, the interaction mechanism among Cu(II), Zn(II), CTS and sodium dodecyl benzene sulfonate (SDBS) was studied. The results revealed that CTS and Cu(II) or Zn(II) formed a supramolecular complex with RRS enhancement in weak acid condition. In the presence of SDBS, the RRS intensity of CTS-Cu(II)-SDBS or CTS-Zn(II)-SDBS was significantly higher than that of the binary system without SDBS at the same CTS concentration. The RRS intensity of CTS-Cu(II)-Zn(II)-SDBS was higher than that of CTS-Cu(II)-SDBS and CTS-Zn(II)-SDBS. The RRS intensity increased linearly with the increase of CTS concentration made it possible to determine CTS quantitatively. In the range extending from 0.10 to 5.00 μg/mL, the equation of linear regression was ΔI=1848.8c-138.3 with a correlation coefficient 0.9996, and the detection limit was estimated to be 37.96 ng/mL. The study was successfully applied for the determination of CTS in health food samples, suggesting its great potential toward CTS analysis.

A novel aptamer RRS assay platform for ultratrace melamine based on COF-loaded Pd nanocluster catalytic amplification

Two COFs of BzBD and BzBD loaded Pd nanoclusters (BzBD_Pd) were prepared using 1,3,5-benzenetricarboxaldehyde (Bz), benzidine (BD) and CO reducing agent, and were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and other techniques. BzBD_Pd can strongly catalyze the new and stable Au@NiP nanoreaction that exhibit a strong resonance Rayleigh scattering (RRS) peak at 538 nm and a surface plasmon resonance (SPR) absorption peak at 395 nm, and the sensitive and facile RRS technique was used to study the indicator reaction. Combining the nanocatalytic amplification reaction with specific aptamer (Apt) of some target molecules such as melamine (ML), urea (UR) and bisphenol A (BPA), a simple, sensitive and selective Apt RRS assay platform was established. The linear range of the RRS detection platform for melamine is 0.0025-0.04 nmol/L, and the detection limit (DL) is 1.96 × 10^-4 nmol/L. In addition, ML in real sample was analyzed, the stability of BzBD, BzBD_Pd, PdNPs and the catalytic mechanism of COF_Pd were also considered.

Green synthesis of fluorescent carbon dots with antibacterial activity and their application in Atlantic mackerel (Scomber scombrus) storage

Antimicrobial materials prepared from natural products could provide new ways to preserve seafood and extend the shelf life. Herein, four kinds of fluorescent carbon dots were prepared using onion, ginger, garlic, and fish through one-step hydrothermal synthesis. The four prepared carbon dots were nearly spherical and nanosized, with amorphous structure, neutral charge and good water dispersibility. The onion and garlic carbon dots contained more sulfur elements than the ginger and fish carbon dots. Interestingly, the onion carbon dots exhibited the best antibacterial activity against Pseudomonas fragi with good stability over a wide pH range. In addition, the onion carbon dots also exhibited antimicrobial activity against representative Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. The minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) of onion carbon dots against Pseudomonas fragi were 2 mg mL^-1 and 4 mg mL^-1, respectively. The integrity of the cell wall and the cell membrane were damaged for Pseudomonas fragi, and the extracellular alkaline phosphatase (AKP) and ATP activity also increased after exposure to the onion carbon dots, thus leading to a decrease in the cell viability and alteration of the cellular morphology for Pseudomonas fragi. Furthermore, the preservation effect of onion carbon dots on Atlantic mackerel evaluated by storage at 4 °C revealed that the onion carbon dots significantly reduced drip loss, total volatile basic nitrogen (TVB-N) value and total viable counts (TVC) value, and extended the shelf life of Atlantic mackerel by 2 days. This finding suggests that onion carbon dots have potential to be applied as a bacteriostatic agent for aquatic products.

Determining the Interaction Behavior of Calf Thymus DNA with Anastrozole in the Presence of Histone H1: Spectroscopies and Cell Viability of MCF-7 Cell Line Investigations

The interaction of calf thymus DNA (ct DNA) with anastrozole, which is acknowledged as an antineoplastic drug, has been enquired into in the absence and presence of histone H1, through the means of absorbance, fluorescence, circular dichroism spectroscopy, viscosity, thermal melting, and molecular modeling techniques. In addition, the effects of anastrozole on MCF 7 cell line have been thoroughly investigated. Fluorescence spectroscopy results have indicated that quenching mechanism of ct DNA-anastrozole are known as static quenching procedures, since the Stern-Volmer quenching constant (K_SV) seems to face a decrease as the temperature is enhanced; this is a significant evidence for intercalative binding mode of anastrozole with ct DNA. Regarding the ternary system in the presence of H1, the constant of Stern-Volmer quenching was increased as the temperature was heightened. The thermodynamic parameters suggested that the binding could be characterized as exothermic by negative and positive enthalpy and entropy changes in both binary and ternary systems, respectively. It is vital to mention that hydrogen bonds and hydrophobic contributions play significant roles in anastrozole association to ct DNA in the absence and presence of H1. In accordance to the absorption spectroscopy and melting temperature curve outcomes, the binding mode of anastrozole with ct DNA in absence and presence of H1 was indicative of intercalative and nonintercalative bindings, respectively. The viscosity results as binary and ternary systems, which have been elucidated from a sensitive viscometer, have confirmed the fluorescence spectroscopy determinations. The intercalation of anastrozole to ct DNA seemed to be significantly related to an induced reduction in MCF-7 cell proliferation. The molecular modeling results have suggested that anastrozole could bind to H1 in ct DNA-H1 complex in ternary systems, which supports the conclusions that have been obtained from experimental data.

Fullerene carbon dot catalytic amplification-aptamer assay platform for ultratrace As+3 utilizing SERS/RRS/Abs trifunctional Au nanoprobes

Under microwave conditions, Au-doped carbon dots (CD_Au) were prepared using fullerene as a precursor, and characterized in details. It is found that CD_Au can strongly catalyze the reaction of HAuCl₄-fructose to generate gold nanoparticles (AuNPs). The new nanocatalytic reaction was studied by surface-enhanced Raman scattering (SERS), resonance Rayleigh scattering (RRS) and absorption (Abs) spectrometry. Based on the specific aptamer (Apt_As)-As⁺³ reaction mediated the CD_Au-HAuCl₄-fructose nanoreaction, and the products of AuNPs as SERS/RRS/Abs trifunctional indicator nanoprobes, a new trimode Apt assay strategy was developed for detection of ultratrace As⁺³. A 0.07-0.70, 0.10-0.60 and 0.20-0.70 μg L^-1 were determined by SERS, RRS and Abs, with detection limits (DL) of 0.04, 0.06, 0.10 μg L^-1 respectively. The aptamer-regulation CD_Au catalytic amplification platform can be also used to assay 1.7-13.3 nmol L^-1 Pb²⁺ and 2.0-12 μmol L^-1 Hg²⁺, with DL of 0.80 nmol L^-1 and 0.90 μmol L^-1 respectively.

A resonance Rayleigh scattering and fluorescence quenching dual-channel sensor for sensitive detection of chitosan based on Eosin Y

The sensitive chitosan (CTS) detection methods based on the resonance Rayleigh scattering (RRS) quenching method and fluorescence quenching of Eosin Y were put forward. In the HAC-NaAC buffer solution, Eosin Y interacted with Triton X-100 to generate the binary complex which served as the RRS spectral probe. When CTS was interacted with the binary complex, the RRS intensity decreased with the increase of CTS. At the same time, the fluorescence intensity of Eosin Y decreased in the presence of Triton X-100, and the fluorescence intensity of "Eosin Y+Triton X-100" system further decreased when CTS was added. So it was further proved that there was a forming complex in "Eosin Y+Triton X100+CTS" system. The interaction was characterized by zeta potential, RRS, fluorescence spectrum, and UV-Vis spectroscopy. Under optimal conditions, there was a good linear relationship between the RRS decreased intensity (ΔI) and the concentration of CTS in the range of 0.05-1.30 μg/mL, with a regression equation of ΔI = 1325c + 73.66 and correlation coefficient (R²) of 0.9907. The detection limit was 0.0777 μg/mL. Likewise, the linear range of the fluorescence quenching was 0.03-1.30 μg/mL; the regression equation was ΔF = 1926c + 294.0 with R² = 0.9800 under fluorescence quenching. The detection limit was 0.0601 μg/mL. Therefore, the dual-channel sensor for the determination of CTS was applied to the health products, and the results were satisfactory. The t test result showed that there was no statistical difference between the two methods.

Resonance Rayleigh scattering and spectrofluorimetric approaches for the selective determination of rupatadine using erythrosin B as a probe: application to content uniformity test

In this study, spectrofluorimetric and resonance Rayleigh scattering techniques were applied for the first time for determination of rupatadine through two validated methods. The proposed methods were based on a facile association complex formation between rupatadine and erythrosin B reagent in acidic medium. Spectrofluorimetric determination relied on the quenching effect of rupatadine on the fluorescence intensity of erythrosin B at 556 nm (excitation = 530 nm). Conversely, the resonance Rayleigh scattering (RRS) method relied on enhancement in the resonance Rayleigh scattering spectrum of erythrosin B at 344 nm after the addition of rupatadine. The developed methods produced linear results over ranges 0.15-2.0 μg/ml and 0.1-1.5 μg/ml, with detection limits of 0.030 μg/ml and 0.018 μg/ml for the spectrofluorimetric method and the RRS method, respectively. All reaction conditions for rupatadine-erythrosin B formation were optimized experimentally and both methods were validated according to International Council for Harmonisation guidelines. The developed methods were applied to estimate rupatadine content in its pharmaceutical tablet dosage form with acceptable recoveries. Furthermore, a content uniformity test for the commercial rupatadine tablets was successfully applied by the suggested spectroscopic methods according to United States Pharmacopeia guidelines.

Application of Gelatin Decorated with Allura Red as Resonance Rayleigh Scattering Sensor to Detect Chito-Oligosaccharides

A convenient and sensitive triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method for the detection of chito-oligosaccharides (COS) was proposed based on enhancing the rigid surface of porous reticular spatial structure of gelatin and COS by introducing allura red AC (AR). The interaction and resultant porous reticular spatial structure were characterized with transmission electron microscopy (TEM), RRS, and UV-Vis spectroscopy. The results indicated that gelatin and COS formed porous reticular spatial structure with an average diameter of 1.5-2.0 μm, and the RRS value of COS-AR-gelatin ternary system with gelatin participation was significantly higher than that of COS-AR binary system. Under the optimal conditions, the enhanced TWO-RRS intensity of the system was linearly proportional to COS concentration in the range of 0.30-2.50 μg/mL, and the regression equation was ΔI = 4933.2c-446.21 with R2 = 0.9980. The limit of detection was 0.0478 μg/mL. So, a new method for the detection of COS was established and verified in the health products with satisfactory results.

Simultaneous determination of cytokinins by high performance liquid chromatography with resonance Rayleigh scattering and mechanism discussion

A reliable, highly sensitive and highly selective method of high performance liquid chromatography associated with resonance Rayleigh scattering (HPLC-RRS) was developed to detect three cytokinins, namely, 6-benzylaminopurine (BA), kinetin (KT) and zeatin (ZT). In this work, Pd(ii) is added into the system to form ternary ion association complexes for the first time, which results in a lower limit of detection and extends the application of HPLC-RRS. The experimental conditions were optimized. In order to investigate the reaction mechanism, the ternary ion association complexes were characterized by ultraviolet-visible spectrophotometry, dynamic light scattering, scanning electron microscopy and density functional theory calculations. In a HAc-NaAc buffer solution (pH = 4.1), a ternary complex of cytokinin : Pd(ii) : EryB (1 : 1 : 2) was formed. The detection limits (S/N = 3) of BA, KT, and ZT were 0.9, 1.5 and 2.3 ng mL-1, respectively. In addition, this method was applied for the simultaneous detection of cytokinins in real samples with satisfactory results.

The triple-wavelength overlapping resonance Rayleigh scattering method and the fluorescence quenching method for the determination of chitooligosaccharides using trisodium-8-hydroxypyrene-1,3,6-trisulfonate as a probe

In this assay, the triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method and the fluorescence quenching method for the quantitative detection of chitooligosaccharides (COS) were developed. In the weakly Britton-Robinson buffer solution, COS interacted with Trisodium-8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to form an ion-association complex of HPTS-COS, which increased the RRS intensities at 321 nm, 430 nm and 511 nm and decreased the fluorescence intensities of the system at 512 nm. And the changes in the intensities of both methods were related to the changes in the concentration of COS. Moreover, for the TWO-RRS method, OP-10 made the RRS intensities increased stronger, finally, the three peaks' total was linear to the concentration of COS in the range of 1.00-8.00 μg/mL and the limit of detection (LOD) was 0.247 μg/mL, and for the fluorescence quenching method, the linear range was 0.50-3.50 μg/mL with the LOD of 0.108 μg/mL. Based on these, two new and fast spectral methods with high sensitivity and simplicity for the determination of trace COS had been established. The generation mechanism of the TWO-RRS and the fluorescence quenching was studied. At the same time, the two methods were applied to the determination of COS in health products with satisfactory results.

Label free aptasensor for ultrasensitive detection of tobramycin residue in pasteurized cow's milk based on resonance scattering spectra and nanogold catalytic amplification

TOB aptamer can be adsorbed on the AuNPs surface to form AuNPs-aptamer complexation to prevent AuNPs aggregation in high salt solution. When TOB was added to the AuNPs solution, the aptamer would bind with TOB and depart from the AuNPs surface. The amount of the AuNPs-aptamer complexation depends on the TOB concentration. Different concentration of AuNPs-aptamer can catalyze the reduction reaction of CuSO₄ to produce different size Cu₂O particle. The resonance scattering peak intensities are correlated with the Cu₂O size. Large size Cu₂O particle as a resonance scattering spectroscopy probe can remarkable improve the TOB detection sensitivity. We have succeeded to detect the trace TOB in aqueous solutions. The linear range and limit of detection were 0.50-17 nM and 0.19 nM, respectively. This simple and inexpensive method exhibited high sensitivity and selectivity, which was successfully used to detect TOB in milk. The results indicated the accuracy and precision were satisfied.

Resonance Rayleigh scattering assay for EGFR using antibody immobilized gold nanoparticles

A highly selectivity determination of epidermal growth factor receptor (EGFR) has been described in the article. Antibody immobilized cysteamine (Cys) functionalized gold nanoparticles (AuNP) were proposed as immunosensors, and resonance Rayleigh scattering (RRS) was used for detection. First, Cys stabilized AuNPs (Cys-AuNP) were prepared by the reduction of chloroauric acid with sodium borohydride in the presence of Cys. Further, anti-EGFR antibody (Cetuximab, C225) was covalently linked to the Cys-AuNP by carbodiimide-mediated amidation protocol to yield the C225-AuNP immunoprobe. The prepared conjugations were characterized by ultraviolet-visible (UV-vis) spectroscopy, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Based on the specific binding of C225 to EGFR, an RRS method was established to determine the concentration of EGFR. Under the optimal conditions, the concentration of EGFR was related to the intensity of RRS in the range 30-130 ng ml^-1 with a low detection limit of 4.0 ng ml^-1 . Meanwhile, the proposed immunosensor exhibited excellent selectivity and anti-interference property. The method was applied to the determination of EGFR in human serum and cancer cell lysate samples with satisfactory results.

Targeting and sensing of some cancer cells using folate bioreceptor functionalized nitrogen-doped graphene quantum dots

In recent years, study of folate receptor (FR) expression related to targeting, drug delivery and counting of tumoral cells have been followed. In this work, a fast and simple strategy was reported to determine the FR expressed cancer cells based on the selective bonding of the folic acid/folate (FA) to the FR-positive tumor cells. The folate decorated Nitrogen-doped graphene quantum dots (N-GQDs) were utilized as selective targeting of the MKN 45 cells. Fluorescent microscopy imaging investigations revealed that the produced FA conjugated N-GQDs could specifically attach to the target FR-positive tumor cells. Due to the fluorescence emission of N-GQDs, the developed cytosensor is free from attaching any fluorescent ligand i.e. Rhodamine B to capture the florescence microscopy images and also flow cytometry analysis. The fabricated cytosensor possesses a dynamic range from 100 to 7.0 × 10⁴ cell·mL^-1 with high selectivity. Furthermore, the cytosensor also could visualized the MCF 7 and HT 29 cells where the dynamic ranges were 100 to 1.0 × 10⁴ and 500 to 4.0 × 10⁴ cells·mL^-1, respectively. In vitro toxicity tests has shown low toxicity of the synthesized N-GQDs where the minimum viability is 68%. The proposed FA-N-GQDs based cytosensor provides a novel platform for detection of MKN 45, HT 29 and MCF 7 cancer cell lines which could be used in multi-channel cancer diagnosis biodevice.

Study on Brilliant Blue-chitosan System by Dual-wavelength Overlapping Resonance Rayleigh Scattering Method and its Analytical Applications

The method was presented for the sensitive and selective determination of chitosan (CTS) in health products with Brilliant Blue (BB) as a probe, based on dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS). In weakly acidic buffer solution, the binding of CTS and BB could result in the RRS intensities getting enhanced significantly at RRS peaks of 344nm and 452nm, and the scattering intensities of the two peaks were proportional to the concentration of CTS within a certain range. When the RRS intensities of the two wavelengths were superposed, the results showed higher sensitivity. Under the optimum experimental conditions, the total of the two increased RRS intensities was linear to the CTS concentration in the range of 0.02-1.80μg/mL and the limit of detection (LOD) was 7.45ng/mL. In this work, the optimum conditions and the effects of some foreign substances were studied. Accordingly, the new method based on DWO-RRS for the determination of CTS was developed. In addition, the effect of the molecular weight and the deacetylation degree between different chitosan molecules was discussed. Finally, this assay was applied to determine the concentration of CTS in health products with satisfactory results.

A facile and highly sensitive resonance Rayleigh scattering-energy transfer method for urea using a fullerene probe

Under ultrasound conditions, a deep yellow fullerene (C₆₀) colloid was prepared, which exhibits two resonance Rayleigh scattering peaks at 385 nm and 530 nm. Urea was reacted with dimethylglyoxime (DMG) to produce 4,5-dimethyl-2-imidazole ketone (DIK), in the presence of stabilizer thiosemicarbazone (TSC). Resonance Rayleigh scattering energy transfer (RRS-ET) was shown to occur between the donor fullerene and acceptor DIK due to an overlap of the DIK absorption and fullerene RRS peaks. Upon an increase in the urea concentration, the RRS-ET was enhanced and the RRS intensity decreased. The decreased RRS intensity was linear to the urea concentration in the range of 6.66–333.00 nmoL L⁻¹, with a detection limit of 2.0 nmoL L⁻¹. Accordingly, a new and simple RRS-ET method was established for detecting trace levels of urea in foods, with satisfactory results.

Under ultrasound conditions, a deep yellow fullerene (C₆₀) colloid was prepared, which exhibits two resonance Rayleigh scattering peaks at 385 nm and 530 nm.