Huanbao Fa

Discrimination of Chinese green tea according to varieties and grade levels using artificial nose and tongue based on colorimetric sensor arrays

Colorimetric artificial tongue and nose were used to discriminate nine Chinese green teas from different geographical origins and grade levels. Printing nanoporous porphyrin, dimeric metalloporphyrins, metallosalophen complexes and chemically responsive dyes on a hydrophobic membrane, the developed sensor array of artificial tongue and nose showed a unique pattern of colorimetric change upon exposure to green tea liquids or gases. All green tea samples, both in liquid and gas analysis, gave distinct patterns according to geographical origin and grade level, thus resulting in their facile identification. The good reproducibility of colorimetric artificial tongue and nose was proved. Data analysis was performed by chemometric techniques: hierarchical cluster analysis (HCA), and principal component analysis (PCA). Chinese green tea from the same geographical origin could cluster together in PCA score plot. No errors in classification by HCA were observed in 90 trials. The colorimetric artificial tongue and nose can be used to discriminate Chinese green tea according to geographical origin and grade level.

Interaction of monosulfonate tetraphenyl porphyrin (H2TPPS1) with plant-esterase: Determination of the binding mechanism by spectroscopic methods

The interaction of monosulfonate tetraphenyl porphyrin (H(2)TPPS(1)) with plant-esterase was investigated using fluorescence and UV-vis absorption spectroscopy. Fluorescence quenching, from which the binding parameters were evaluated, revealed that the quenching of the esterase by H(2)TPPS(1) resulted from the formation of a dye-esterase complex. According to the modified Stern-Volmer equation, the effective quenching constants (K(a)) between H(2)TPPS(1) and plant-esterase at four different temperatures (297 K, 300 K, 303 K, and 306 K) were obtained to be 14.132×10(5), 5.734×10(5), 2.907×10(5), and 2.291×10(5) M(-1), respectively. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be -181.67 kJ M(-1) and -0.49 kJ M(-1)K(-1), indicating that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. Site marker competitive experiments showed that the binding of H(2)TPPS(1) to plant-esterase primarily took place in the active site. The binding distance (r) was obtained to be 5.99 nm according to Förster theory of non-radioactive energy transfer. The conformation of plant-esterase was investigated by synchronous fluorescence and UV-vis absorption spectroscopy, and the results confirmed some micro-environmental and conformational changes of plant-esterase molecules.

Molecular interactions of monosulfonate tetraphenylporphyrin (TPPS1) and meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) with dimethyl methylphosphonate (DMMP)

The molecular interactions of monosulfonate tetraphenylporphyrin (TPPS(1)) and meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) with dimethyl methylphosphonate (DMMP) have been investigated by UV-vis and fluorescence spectroscopies. The association constants and interaction stoichiometries of the bindings were obtained through Benesi-Hildebrand (B-H) method. Particularly, both linear and nonlinear fitting procedures were performed to evaluate the possible 1:2 interactions. Experimental results showed that hydrogen-bonding interactions existed in both of the two systems, resulting in regular changes in the absorbance and fluorescence characteristics of the porphyrins. The association constants and stoichiometries determined from absorbance and fluorescence studies were in excellent agreement. Using a nonlinear fitting method, we demonstrated that the one-step 1:2 interaction took place in the TPPS(1)-DMMP system, and the association constants were determined to be 71.4 M(-1) by absorbance measurements and 70.92 M(-1) by fluorescence measurements. The interaction stoichiometry of the TPPS-DMMP system was 1:1, and the association constants were determined to be 16.06 M(-1) by absorbance measurements and 16.03 M(-1) by fluorescence measurements. It was concluded that the interaction between TPPS(1) and DMMP was stronger than that between TPPS and DMMP.

Synthesis of superparamagnetic iron oxide nanoparticles coated with a DDNP-carboxyl derivative for in vitro magnetic resonance imaging of Alzheimer's disease.

Superparamagnetic iron oxide nanoparticles (SPIONs) have been proposed for use in magnetic resonance imaging as versatile ultra-sensitive nanoprobes for Alzheimers disease imaging. In this work, we synthetized an efficient contrast agent of Alzheimers disease using 1,1-dicyano-2-[6-(dimethylamino)naphthalene-2-yl]propene (DDNP) carboxyl derivative to functionalize the surface of SPIONs. The DDNP-SPIONs are prepared by conjugating DDNP carboxyl derivative to oleic acid-treated SPIONs through ligand exchange. The structure, size distribution and magnetic property were identified by IR, TGA-DTA, XRD, TEM, Zetasizer Nano and VSM. TEM and Zetasizer Nano observations indicated that the DDNP-SPIONs are relatively mono-dispersed spherical distribution with an average size of 11.7nm. The DDNP-SPIONs were then further analyzed for their MRI relaxation properties using MR imaging and demonstrated high T2 relaxivity of 140.57s(-1)FemM(-1), and the vitro experiment that DDNP-SPIONs binding to β-Amyloid aggregates were then investigated by fluorophotometry, the results showed that the combination had induced the fluorescence enhancement of the DDNP-SPIONs and displayed tremendous promise for use as a contrast agent of Alzheimers disease in MRI.

Colorimetric detection of Cr (VI) based on the leaching of gold nanoparticles using a paper-based sensor.

Herein, we have developed a simple, sensitive and paper-based colorimetric sensor for the selective detection of Chromium (Ⅵ) ions (Cr (VI)). Silanization-titanium dioxide modified filter paper (STCP) was used to trap bovine serum albumin capped gold nanoparticles (BSA-Au NPs), leading to the fabrication of BSA-Au NPs decorated membrane (BSA-Au NPs/STCP). The BSA-Au NPs/STCP operated on the principle that BSA-Au NPs anchored on the STCP were gradually etched by Cr (VI) as the leaching process of gold in the presence of hydrobromic acid (HBr) and hence induced a visible color change. Under optimum conditions, the paper-based colorimetric sensor showed clear color change after reaction with Cr (VI) as well as with favorable selectivity to a variety of possible interfering counterparts. The amount-dependent colorimetric response was linearly correlated with the Cr (VI) concentrations ranging from 0.5µM to 50.0µM with a detection limit down to 280nM. Moreover, the developed cost-effective colorimetric sensor has been successfully applied to real environmental samples which demonstrated the potential for field applications.

Development of a colorimetric sensor array for the discrimination of Chinese liquors based on selected volatile markers determined by GC-MS.

A new colorimetric sensor array was developed for the discrimination of 12 high-alcoholic Chinese base liquors from Luzhou Co., Ltd., and 15 commercial Chinese liquor of different brands as well as flavor types. Seventeen volatile compounds within four chemical groups were determined as markers in the base liquor by GC-MS analysis and factor analysis method (FAM). A specialized colorimetric sensor array composed of 20 sensitive dots was fabricated accordingly to obtain sensitive interaction with different types of volatile markers. Discrimination of the liquor samples was subsequently performed using chemometric and statistical methods, including principal component analysis (PCA) and hierarchical clustering analysis (HCA). The results suggested that facile identification of either base liquors with high-alcoholic volume or commercial liquors of the same flavor types could be achieved by analysis of the color change profiles. The response of the sensor improved significantly in comparison with those that rely on nonspecific interactions, and no misclassification was observed for both liquor samples using two chemometric methods. Besides, it was also found that the discrimination is closely related to the characteristic flavor compounds (esters, aldehydes, and acids) and alcoholic strength in liquors, and its performance was even comparable with that of GC-MS.

A novel chemical detector using colorimetric sensor array and pattern recognition methods for the concentration analysis of NH3

With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30-210 ppb (parts per 10(9))] NH(3) was detected by the system. This prototype successfully differentiated four concentration levels of NH(3) in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs.

Discrimination of Lung Cancer Related Volatile Organic Compounds with a Colorimetric Sensor Array

A simple and rapid discrimination of four lung cancer related volatile organic compounds (VOCs) was achieved with a novel colorimetric sensor array. Based on the cross-responsive mechanism, the sensor system exhibited high sensitivity to selected lung cancer biomarkers, including p-xylene, styrene, isoprene, and hexanal with concentrations varying from 50 ppb to 500 ppb. By extracting color information, it provided good selectivity and fine discrimination of selected gases via pattern recognition with Fisher linear discriminant (FLD). Additionally, with the employment of the Takagi-Sogeno Fuzzy Neural Network (TSFNN), different concentrations of selected VOCs were discriminated. It also suggested that the colorimetric sensor array proposed could not only distinguish different lung cancer related VOCs but also discriminate specific VOCs of different concentrations with an average rate of classification up to 95%. Our preliminary study demonstrated that the cross-responsive sensor array had infinite potential for further clinical and commercial use for early diagnosis of lung cancer.

A highly sensitive electrochemical DNA biosensor for rapid detection of CYFRA21-1, a marker of non-small cell lung cancer

Many studies have confirmed that CYFRA21-1 is both a sensitive and specific marker for non-small cell lung cancer (NSCLC), in particular, squamous cell carcinoma. Therefore, methods to detect CYFRA21-1 are sought to enable early diagnosis. In this manuscript, we report a simple, effective, and convenient method to detect CYFRA21-1 using a novel electrochemical DNA biosensor based on a nanocomposite consisting of carboxyl-functionalized graphene oxide (GO-COOH) and copper oxide nanowires (CuO NWs). The nanocomposite is highly conductive, and was characterized by scanning electron microscopy, transmission electron microscopy, and cyclic voltammetry. Differential pulse voltammetry was also applied to monitor DNA hybridization, using methylene blue as an electrochemical indicator. Under optimal conditions, the biosensor is highly sensitive, with a low detection limit of 1.18 × 10−13 M (at S/N 3). Indeed, CYFRA21-1 could be quantified with good linearity (R2 = 0.9750) from 1.0 × 10−12 to 1.0 × 10−6 M. The sensor has good stability and selectivity, and discriminates between ssDNA sequences with one- or three-base mismatches. PCR-amplified CYFRA21-1 from a clinical sample was successfully detected, indicating potential application of the biosensor in clinical research and practice.

A regenerative and selective electrochemical aptasensor based on copper oxide nanoflowers-single walled carbon nanotubes nanocomposite for chlorpyrifos detection

Chlorpyrifos is a commonly used organophosphorus pesticide in agriculture. However, its neurotoxicity poses a huge threat to human health. To detect trace amounts of chlorpyrifos, we herein developed a regenerative electrochemical aptasensor for the sensitive detection of chlorpyrifos. The nanocomposite consisting of copper oxide nanoflowers (CuO NFs) and carboxyl-functionalized single walled carbon nanotubes (c-SWCNTs) was prepared to improve the sensing performance for chlorpyrifos detection. Various characterization methods such as scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and cyclic voltammetry (CV) were used to demonstrate the successful fabrication of biosensor. Differential pulse voltammetry (DPV) was utilized to optimize test conditions and quantify chlorpyrifos. Under optimal conditions, the biosensor obtained a good linearity for chlorpyrifos ranging from 0.1 to 150ng/mL, with a lower detection limit of 70pg/mL. This aptasensor also exhibited high selectivity and outstanding repeatability, and was successfully applied to the determination of chlorpyrifos in spiked apple and celery cabbage with satisfactory recoveries. Furthermore, the sensor can be easily regenerated by urea for continuous application. With all the features, the proposed strategy provides an excellent platform for regenerative and selective detection of chlorpyrifos.