Biomedical subjects

Ru-Qin Yu

Publications and source records attributed to Ru-Qin Yu.

At least 37 records · Page 2Linked to original sources

PubMed2005

QSAR analysis of substituted bis[(acridine-4-carboxamide)propyl]methylamines using optimized block-wise variable combination by particle swarm optimization for partial least squares modeling.

In the current work, we employed optimized block-wise variable combination (OBVC) by particle swarm optimization (PSO) based on partial least squares (PLS) modeling for variable combination and compared it to the traditional methods. It has been demonstrated that the modified PSO is a useful tool for searching optimized variable combination. Quantitative structure-activity relationship (QSAR) model has been formulated for a set of DNA binding topoisomerase (topo) (substituted bis[(acridine-4-carboxamide)propyl]methylamines) on murine Lewis lung carcinoma (LL(c)) cells. The spatial descriptors especially Jurs descriptors play important roles in predicting the compound's inhibitory activity to murine LL(c) cells, and polar interactions are the principal binding strength between compounds and murine LL(c) cells. In addition, rotatable bonds in molecules and molar refractivity of the compounds will markedly affect the compounds' inhibitory activity.

Acridines↗

PubMed2005

An electrochemical stripping metalloimmunoassay based on silver-enhanced gold nanoparticle label.

A novel, sensitive electrochemical immunoassay has been developed based on the precipitation of silver on colloidal gold labels which, after silver metal dissolution in an acidic solution, was indirectly determined by anodic stripping voltammetry (ASV) at a glassy-carbon electrode. The method was evaluated for a noncompetitive heterogeneous immunoassay of an immunoglobulin G (IgG) as a model. The influence of relevant experimental variables, including the reaction time of antigen with antibody, the dilution ratio of the colloidal gold-labeled antibody and the parameters of the anodic stripping operation, upon the peak current was examined and optimized. The anodic stripping peak current depended linearly on the IgG concentration over the range of 1.66 ng ml(-1) to 27.25 microg ml(-1) in a logarithmic plot. A detection limit as low as 1 ng ml(-1) (i.e., 6 x 10(-12) M) human IgG was achieved, which is competitive with colorimetric enzyme linked immuno-sorbent assay (ELISA) or with immunoassays based on fluorescent europium chelate labels. The high performance of the method is attributed to the sensitive ASV determination of silver (I) at a glassy-carbon electrode (detection limit of 5 x 10(-9) M) and to the catalytic precipitation of a large number of silver on the colloidal gold-labeled antibody.

Biosensing Techniques↗

PubMed2005

Immunosensor for rapid detection of gibberellin acid in the rice grain.

A rapid, selective, sensitive, accurate, and inexpensive immunosensor for gibberellin acid detection was designed by coupling immunoassay with the square wave anodic stripping voltammetry (SWASV) technique involving copper ion labeled antigen in the competitive immunoreaction. The response signal expressed as the percentage of current reduction CR % (y) is linearly related to the concentration of GA (x) in the 1 microg/mL to approximately 150 microg/mL range with a regression equation of the form y = 0.44x + 15.59 and a correlation coefficient of 0.99. The results of the immunosensor assay were compared with those obtained by HPLC and ELISA, which show a satisfactory agreement. The immunosensor was used to determine the GA content in the hybrid rice grain samples taken in the growing period.

Antigens↗

PubMed2005

A sensitive immunoassay based on electropolymerized films by capacitance measurements for direct detection of immunospecies.

Fabrication of a capacitive immunosensor based on electropolymerized polytyramine (Pty) film for the direct detection of human serum albumin (HSA) without any labeling is described. The capacitance change of the heterostructures, Pty films/covalently bonded antibodies/buffered medium, is utilized for monitoring the specific antibody-antigen interaction. The Pty films are ultrathin and the HSA assay is nearly specific. Experimental parameters affecting antibody immobilization and the sensing of HSA are investigated in detail and optimized. This capacitive sensor prepared with the present method can provide high sensitivity. Under the optimized experimental conditions, a linear calibration curve in the concentration range 1.84-368.6 ng/ml when plotted vs the logarithm of the antigen concentration is obtained and the detection limit (S/N=3) is 1.60 ng/ml. After an acidic washing the present system can be used again. The applicability and reliability of the sensor are also demonstrated.

Animals↗

PubMed2005

Nanosized flower-like ZnO synthesized by a simple hydrothermal method and applied as matrix for horseradish peroxidase immobilization for electro-biosensing.

Nanosized flower-like ZnO was synthesized by a simple hydrothermal method which is a convenient, environment friendly, inexpensive and efficient process. Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to confirm the material structure and the crystallite microstructure. Then ZnO was dispersed in the chitosan solution to form a ZnO/chitosan composite matrix for the fabrication of H2O2 biosensor. This composite combined the advantages of inorganic species (ZnO) and organic polymer (chitosan). The parameters affecting the fabrication and experimental conditions of biosensors were optimized. Using hydroquinone as the mediator, the biosensor showed a fast response of less than 5s with the linear range of 1.0x10(-5) to 1.8x10(-3) M H2O2 with a correlation coefficient of 0.995 (n=20). The detection limit of the sensor was found to be 2.0 microM, based on a signal-to-noise ratio of 3. The biosensor exhibited satisfactory reproducibility and stability and retained about 78% of its original response after 40 days storage in a phosphate buffer at 4 degrees C.

Biosensing Techniques↗

PubMed2005

Optochemical sensor for an ornidazole assay using 1-amino-4-allyloxyanthraquinone as a fluorescent indicator.

To improve the stability of optochemical sensors (optodes), the fluorescence indicator 1-amino-4-allyloxyanthraquinone (AAA), which was synthesized by reacting allyl bromide with 1-amino-4-hydroxyanthraquinone, was covalently immobilized on surface-modified glass slides. The resulting sensor was used to determine the content of ornidazole based on fluorescence quenching. It showed a linear response toward ornidazole in the concentration range of 9.0 x 10(-6) to 1.0 x 10(-3) mol L(-1) with a detection limit of 8 x 10(-6) mol L(-1) at pH 7.5. This AAA-immobilized sensor has a rapid response, high stability and good selectivity to ornidazole.

Anthraquinones↗

PubMed2004

Piezoelectric immunoassay for complement C4 based on a Nafion-modified interface for antibody immobilization.

A piezoelectric immunosensor based on a Nafion membrane interface with a simple immobilization procedure has been developed for the determination of complement C4 in human serum. The polyanionic perfluorosulfonated Nafion polymer was used to modify the electrode surface of quartz-crystal microbalance (QCM) as a platform for the immobilization of complement C4 antibodies. The surface morphology of QCM modified with Nafion membrane was investigated using scanning electron microscopy. The system was optimized with regard to the parameters involved in the preparation of the immunosensor and the assay process. The proposed immunosensor responds well to C4 in the range of 0.08-1.6 microg/ml with a relative standard deviation of <5.3%. Moreover, the proposed immunosensor has advantages in terms of the speed and simplicity of the immobilization procedure as well as the simple and advantageous regeneration process. The experimental results obtained with regard to nonspecific adsorption and recovery indicate that the proposed immunosensor offers a promising alternative tool for the clinical diagnosis of complement C4.

Antibodies↗

PubMed2004

Hybridized particle swarm algorithm for adaptive structure training of multilayer feed-forward neural network: QSAR studies of bioactivity of organic compounds.

The multilayer feed-forward ANN is an important modeling technique used in QSAR studying. The training of ANN is usually carried out only to optimize the weights of the neural network and without paying attention to the network topology. Some other strategies used to train ANN are, first, to discover an optimum structure of the network, and then to find weights for an already defined structure. These methods tend to converge to local optima, and may also lead to overfitting. In this article, a hybridized particle swarm optimization (PSO) approach was applied to the neural network structure training (HPSONN). The continuous version of PSO was used for the weight training of ANN, and the modified discrete PSO was applied to find appropriate the network architecture. The network structure and connectivity are trained simultaneously. The two versions of PSO can jointly search the global optimal ANN architecture and weights. A new objective function is formulated to determine the appropriate network architecture and optimum value of the weights. The proposed HPSONN algorithm was used to predict carcinogenic potency of aromatic amines and biological activity of a series of distamycin and distamycin-like derivatives. The results were compared to those obtained by PSO and GA training in which the network architecture was kept fixed. The comparison demonstrated that the HPSONN is a useful tool for training ANN, which converges quickly towards the optimal position, and can avoid overfitting in some extent.

Journal Article↗

PubMed2004

QSAR analysis of cyclooxygenase inhibitor using particle swarm optimization and multiple linear regression.

Quantitative structure-activity relationship (QSAR) models of inhibiting action of some diarylimidazole derivatives on cylcooxygenase (COX) enzyme were constructed using modified particle swarm optimization (PSO) method. As a comparison to this method, the genetic algorithm (GA) was also tested. It has been demonstrated that the modified PSO is a useful tool for variable selection comparable to GA and even superior to GA. QSAR models are constructed separately for COX-2 inhibitory activity and selectivity of COX-2 inhibition over COX-1. The spatial descriptors play a key role in the compounds' activity and selectivity to COX-2, especially Jurs descriptors. Polar interactions are the principal binding strength between compounds and COX-2 enzyme. In addition, the aqueous desolvation free energy (FH2O) value of substituent will affect the COX-2 inhibitory activity, while the charge distribution can affect the selectivity to COX-2.

Cyclooxygenase Inhibitors↗

PubMed2004

Capacitive chemical sensor for fenvalerate assay based on electropolymerized molecularly imprinted polymer as the sensitive layer.

A capacitive chemical sensor for fenvalerate is reported. By using ac impedance measurements the sensor has been based on the decrease in capacitance caused by the analyte used as the template in the formulation of an electropolymerized molecularly imprinted polymer as receptor layer. Improvement of the insulating properties of the sensor was investigated in detail. The capacitive sensor was prepared by a deposition of a self-assembled monolayer of 2-mercaptobenzimidazole (2-MBI) before electropolymerization of 2-MBI and subsequent treatment with n-dodecanethiol to eliminate pinholes and defects in the polymerized 2-MBI film. From the calibration curve concentrations of fenvalerate up to 9 microg mL(-1) could be detected with a linear determination range up to 5 microg mL(-1) and a detection limit of 0.36 microg mL(-1). No significant interference was observed from common pyrethroid insecticides.

Journal Article↗

PubMed2004

An amperometric hydrogen peroxide biosensor based on immobilizing horseradish peroxidase to a nano-Au monolayer supported by sol-gel derived carbon ceramic electrode.

A novel strategy for fabricating horseradish peroxidase (HRP)-based H(2)O(2) sensor has been developed by combining the merits of carbon sol-gel supporting matrix and nano-scaled particulate gold (nano-Au) mediator. The thiol functional group-derived carbon ceramic electrode (CCE) was first constructed using (3-mercaptopropyl) trimethoxy silane as sol-gel monomer. Then, the stable nano-Au monolayer was obtained through covalent linkage between nano-Au and thiol group on the surface of CCE. The experimental results showed that nano-Au monolayer formed not only could steadily immobilize HRP but also efficiently retain its bioactivity. Hydrogen peroxide was detected with the aid of hydroquinone mediator to transfer electrons between the electrode and HRP. The process parameters for the fabrication of the enzyme electrode and various experimental variables such as the operating potential, mediator concentration and pH of background electrolyte were explored for optimum analytical performance of the enzyme electrode. The biosensor had a fast response of less than 8 s with linear range of 1.22 x 10(-5) to 1.10 x 10(-3)mol l(-1) and a detection limit of 6.1 x 10(-6)mol l(-1). The sensitivity of the sensor for H(2)O(2) was 0.29 A l mol(-1) cm(-2). The activation energy for enzyme reaction was calculated to be 10.1 kJ mol(-1). The enzyme electrode retained 75% of its initial activity after 5 weeks storage in phosphate buffer at pH 7.

Biosensing Techniques↗

PubMed2004

Modified particle swarm optimization algorithm for variable selection in MLR and PLS modeling: QSAR studies of antagonism of angiotensin II antagonists.

A version of modified particle swarm optimization (PSO) algorithm has been proposed. The PSO algorithm has been modified to adopt to the discrete combinatorial optimization problem and reduce the probability of sinking into local optima. In the modified PSO algorithm, the velocity represents the probability of element in each particle taking value 1 or 0. The modified discrete PSO algorithm is proposed to select variables in MLR and PLS modeling and to predict antagonism of angiotensin II antagonists. The modified C(p) is employed as fitness function. The results were compared to those obtained by GAs. Experimental results have demonstrated that the modified PSO is a useful tool for variable selection which converges quickly towards the optimal position.

Algorithms↗

PubMed2004

Amperometric hydrogen peroxide biosensor based on horseradish peroxidase-labeled nano-Au colloids immobilized on poly(2,6-pyridinedicarboxylic acid) layer by cysteamine.

A sensitive hydrogen peroxidase (H2O2) amperometric sensor based on horseradish peroxidase (HRP)-labeled nano-Au colloids has been proposed. Nano-Au colloids were immobilized by the thiol group of cysteamine, which was associated with the carboxyl groups of poly(2,6-pyridinedicarboxylic acid) (PPDA). With the aid of the hydroquinone, the sensor displayed excellent electrocatalytical response to the reduction of H2O2. Compared with the non-Au-colloid modified electrode, i.e., PPDA/HRP, the Au-colloid modified electrode exhibited better performance characteristics, including stability, reproducibility, sensitivity and accuracy. The biosensor shows a linear response to H2O2 in the range of 3.0 x 10(-7) - 2 x 10(-3) M. The detection limit was 1.0 x 10(-7) M.

Biosensing Techniques↗

PubMed2003

Proton "off-on" behaviour of methylpiperazinyl derivative of naphthalimide: a pH sensor based on fluorescence enhancement.

In a search for new type pH sensing fluorophores, the possibility of using the proton "off-on" switch behaviour of naphthalimide derivatives for optical pH sensor preparation has been explored. A new compound, N-allyl-4-(4[prime or minute]-methyl-piperazinyl)-1,8-naphthalimide (AMPN), was synthesized. The enhancement of fluorescence of AMPN with the increase of hydrogen ion concentration is based on arresting photo-induced electron transfer to the naphthalimide fluorophore from aliphatic amine group after its protonation. The Stokes Shift of the proposed type of pH sensing fluorophore is significantly larger than that of the fluorescein counterparts. To avoid the leakage of the fluorophore, AMPN was photo-copolymerized with 2-hydroxyethyl methacrylate and acrylamide on the glass surface. The fluorescence intensity of membrane contacted with a pH 3.50 buffer is 4.7 times of that for pH 12.00 buffer solutions. The proposed pH sensor is not susceptible to ionic strength and shows good selectivity, repeatability and short response time. The membrane shows a good stability with a lifetime over two months. The sensor can be used for the determination of pH in the range of pH 4.5-9.0, without interference of most commonly co-existing inorganic ions and some organic species. The sensor has been applied to the analysis of urine samples.

Biosensing Techniques↗

PubMed2003

Amperometric immunosensor based on polypyrrole/poly(m-pheylenediamine) multilayer on glassy carbon electrode for cytokinin N6-(Delta2-isopentenyl) adenosine assay.

A novel immunosensor based on a multilayer-coated glassy carbon electrode was designed to determine isopentenyl adenosine (iPA) in plants. The multilayer consists of polypyrrole and poly(m-phenylenediamine) with K4Fe(CN)6 and horseradish peroxidase (HRP) entrapped during electropolymerization. The ferrocyanide doped in polypyrrole functions as the mediator. The glucose oxidase bound on the immunosensor by the competitive immunoreaction involving iPA catalyzed the oxidation of the added glucose with the formation of H2O2, which is in turn reduced in the presence of HRP entrapped in poly(m-phenylenediamine). The current of the oxidized production of ferrocyanide reduced at -50 mV is inversely proportional to the concentration of iPA in the competitive immunoreaction. This immunosensor is able to be used about 40 times; after that its surface can be regenerated for a new immunosensor assembly by washing with 0.1M citrate-phosphate buffer (pH 4.6). The percentage of current response reduction (CR%) (y) is linearly related to the logarithm of the concentration of iPA (x) in the 5-300 microg/ml range, with a regression equation of the form y = 42.13x - 27.79 and a correlation coefficient of 0.9861. Five hybrid rice grain samples were analyzed with results in satisfactory agreement to those obtained by high-performance liquid chromatography.

Animals↗

PubMed2003

Amperometric biosensor with HRP immobilized on a sandwiched nano-Au / polymerized m-phenylenediamine film and ferrocene mediator.

An amperometric biosensor has been developed for the determination of H(2)O(2) in plant samples. Horseradish peroxidase (HRP) is immobilized on a sandwiched nano-Au particle / m-phenylenediamine polymer film by glutaraldehyde cross-linking. The film is formulated on the carbon paste electrode (CPE) blended with ferrocene as an electron transfer mediator. On the low concentration range, the current response is related to the H(2)O(2) concentration linearly from 0 to 8x10(-6) M with a detection limit of 1.3x10(-7) M. On a wider concentration range of 8x10(-6) to 1.4x10(-4) M, the reciprocal of current response is linearly related to the reciprocal of H(2)O(2) concentration. The apparent Michaelis-Menten constant (K(m)(app)) was calculated to be 0.0334 mM. The sensor has been tested by determining H(2)O(2) concentration in plant leaf samples.

Biosensing Techniques↗

PubMed2003

A coumarin derivative covalently immobilized on sensing membrane as a fluorescent carrier for nitrofurazone.

A coumarin derivative 4-methyl-8-methylacrylamide-2H, 5H-pyrano [3, 2-C] benzpyran 2, 5-dione (MMPBD) has been synthesized as a fluorescent carrier for preparing an optical chemical sensor. The carrier is immobilized on a quartz glass plate surface treated with a silanizing agent to prevent the leakage of the dye. This MMPBD sensor can be utilized for a nitrofurazone (NF) assay based on fluorescence quenching. The sensor shows good repeatability, a long lifetime and a fast response of less then 50 s. NF can be determined in the range between 1.0x10(-6)-1.0x10(-3 )mol L(-1) with a detection limit of 8.0x10(-7) mol L(-1 )at pH 7.0.

Coumarins↗

PubMed2003

Competitive interactions of adriamycin and ethidium bromide with DNA as studied by full rank parallel factor analysis of fluorescence three-way array data.

The competitive interactions of adriamycin (AMC) and a fluorescence probe of ethidium bromide (EB) with DNA have been studied by full rank parallel factor analysis (FRA-PARAFAC) of fluorescence excitation-emission three-way data array. The excitation and emission spectra as well as the equilibrium concentrations of co-existing species in different reaction mixtures can be directly obtained by the FRA-PARAFAC treatment. The concordance of the resolved excitation and emission spectra of AMC, EB and EB-DNA with the standard spectra of these species confirmed the reliability of the equilibrium concentrations of these components in the reaction mixtures studied. The results obtained are valuable for providing a deeper insight into the competitive interaction mechanism of AMC and EB with DNA. The conclusion was directly given out that the interaction of AMC with DNA is the intercalating model. The FRA-PARAFAC method as exemplified by the present study provides an useful approach for studying the interaction of clinical drugs with DNA in the presence of disturbance of drug assistants.

Algorithms↗