Sihua Qian

Protein-templated gold nanoclusters based sensor for off–on detection of ciprofloxacin with a high selectivity

In this contribution, bovine serum albumin stabilized gold nanoclusters as novel fluorescent probes were successfully utilized for the detection of ciprofloxacin for the first time. Our prepared gold nanoclusters exhibited strong emission with peak maximum at 635 nm. Cu(2+) was employed to quench the strong fluorescence of the gold nanoclusters, whereas the addition of ciprofloxacin caused the fluorescence intensity restoration of the Cu(2+)-gold nanoclusters system. The increase in fluorescence intensity of Cu(2+)-gold nanoclusters system caused by ciprofloxacin allows the sensitive detection of ciprofloxacin in the range of 0.4 ng mL(-1) to 50 ng mL(-1). The detection limit for ciprofloxacin is 0.3 ng mL(-1) at a signal-to-noise ratio of 3. The present sensor for ciprofloxacin detection possesses a low detection limit and wide linear range. In addition, the real samples were analyzed with satisfactory results.

A new way to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering signal and its potential application

A novel assay has been developed to detect the interaction of DNA and anticancer drugs based on the decreased resonance light scattering (RLS) technique. The proposed method can be used to study those drugs which do not produce a RLS-signal after binding to DNA. RLS was used to monitor the interaction of five anticancer drugs with DNA. The reaction between anticancer drugs and DNA took place in BR buffer solution. From the RLS assay, the sequence of five anticancer drugs activities was as follows: CTX < MTX < Pt < MMC < 5-Fu. Mammary cancer cell DNA (mcDNA) was involved to validate the RLS assay. The results showed that the sensitivities of the five anticancer drugs targeting both mcDNA and ctDNA increased in the same order. However the sensitivity of each drug to mcDNA was higher than that to ctDNA It is a significant innovation of the RLS method to detect the interaction of DNA and anticancer drugs and to obtain drug sensitivity, which provides new strategies to screen DNA targeted anticancer drugs.

Label-free detection of target DNA sequence and single-base mismatch in hepatitis C virus corresponding to oligonucleotide by resonance light scattering technique

A highly sensitive assay to detect sequence-specific DNA by the resonance light scattering (RLS) technique has been developed based on the enhanced RLS intensities of the RLS spectra at 399.5 nm. It was found that Hoechst 33258, when bound to dsDNA and ssDNA in electrolyte solution, displayed different RLS signals. This encouraged us to perform a direct and unlabelled sequence-specific DNA assay. At optimal conditions, this RLS assay can detect complementary target DNA over a range of 4.0 × 10−9–3.8 × 10−7 mol L−1, and the limit of detection was around 1.7 × 10−9 mol L−1. Additionally, the results of experiments showed that different RLS signals reflected a different degree of mismatch between probe DNA and target DNA, and mismatched variants of target DNA with single-base difference can even be well discriminated. Herein, we moved the RLS technique one-step further toward sensitivity, rapidity, simplicity and non-toxicity. The RLS assay results were identified with a fluorescence method, fluorescence polarization assay and atomic force microscope measurement.

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 microg 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.

An assay of DNA by resonance light scattering technique and its application in screening anticancer drugs

In this contribution, a novel assay has been developed to detect the interaction between DNA and drugs using ethidium bromide (EB) as a probe based on the decreased resonance light scattering (RLS) technique. It was found that, in pH 2.0 Britton–Robinson buffer solution, EB underwent dramatic enhancement of RLS signal when binding to DNA. Additionally, the strong RLS signal of the EB–DNA system was remarkably decreased after the addition of DNA-targeted anticancer drugs. The results showed a linear relationship between the enhanced RLS intensity of the EB–DNA system and concentration of DNA in the range of 0.015–40.8 μg mL−1. The linear regression equation is represented as follows: ΔIRLS = 4.15 + 21.14c with regression coefficient r = 0.9970 (n = 10). The detection limit was 0.3 ng mL−1. Only 2.0 × 10−8 mol L−1 was selected as the optimum EB concentration in this assay. Further study demonstrated that the anticancer efficacy of anticancer drugs varied inversely with RLS intensity of the EB–DNA-drug system. So, it is intuitive to see the sequence of antitumor efficiency of anticancer drugs without data processing by RLS screening spectra. Compared with the traditional cell-based screening methods, the proposed method was more convenient, rapid and intuitive. The reaction mechanism is discussed.

A resonance light scattering sensor based on methylene blue-sodium dodecyl benzene sulfonate for ultrasensitive detection of guanine base associated mutations

AbstractA resonance light scattering (RLS) sensor for guanine base associated mutations has been developed on the basis of the high selectivity of methylene blue (MB) for guanine bases in the presence of sodium dodecyl benzene sulfonate (SDBS). MB, when bound to SDBS, underwent a dramatic enhancement of its RLS intensity. However, the addition of double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) caused the strong RLS intensity of MB–SDBS to decrease, and the RLS intensity of MB–SDBS–ssDNA was much lower than that of MB–SDBS–dsDNA. Consequently, it can be concluded that the binding abilities of MB–SDBS with ssDNA and dsDNA were different. Besides, the experimental results showed that MB–SDBS could bind specifically to oligonucleotides rich in guanine bases. Short DNA targets with sequences related to β-thalassaemia, thrombophilia and psoriasis, all of which are guanine base relevant mutations, were synthesized. It was found that MB–SDBS could recognize the single-base mismatches in the mutational DNA, followed by different RLS signal changes between MB–SDBS–normal DNA systems and MB–SDBS–mutational DNA systems. The ultrasensitive sensor allows simple, rapid, sensitive and selective detection of guanine base associated mutations, indicating its potential application in the medical field. FigureAn RLS sensor for the detection of guanine base associated mutations