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Biomedical subjects

Guoan Luo

Publications and source records attributed to Guoan Luo.

At least 19 recordsLinked to original sources
PubMed2006

High-speed, whole-column fluorescence imaging detection for isoelectric focusing on a microchip using an organic light emitting diode as light source.

An integrated and simplified microfluidic device using a 250 microm x 1-4 cm of organic light emitting diode (OLED) array as a two-dimensional light source for single-channel and multichannel whole-column imaging detection was developed. This fluorescence detection system was used for isoelectric focusing (IEF) of R-phycoerythrin in a microchip. The IEF conditions were optimized, and the total analysis time was extremely reduced to 30 s for 2-cm-long microchannels at 700 V/cm of electric field strength without the presence of electroosmotic flow. The compression of pH gradient caused by electrolytes drawing into the microchannels was efficiently restrained when 1% hydroxylpropylmethyl cellulose in 2% ampholyte was used as the carrier for IEF. Under optimized IEF conditions, the detection limit of this system was approximately 0.6 microg/mL or 45 pg at 75 nL/column injection of R-phycoerythrin. This OLED-induced fluorescence detection system for WCID provides a high-speed IEF technique with quantitative ability and the potential for high integration and throughput microchip systems.

Fluorescence↗
PubMed2006

Off-line comprehensive two-dimensional high-performance liquid chromatography system with size exclusion column and reverse phase column for separation of complex traditional Chinese medicine Qingkailing injection.

A comprehensive two-dimensional liquid chromatography system was constructed on the combination of size exclusion chromatography (SEC) and reverse phase liquid chromatography (RPLC). The first dimension used a SEC column with 300 mm x 8mm i.d., packed with Toyopearl HW-40S. The column was eluted with 0.05 mol/l Tris-HCl (pH 6.9) at a flow rate of 0.4 ml/min. The second dimension used a RPLC column with 100 mm x 4.6mm i.d., which was operated in gradient form at a flow rate of 1.0 ml/min. An automatic switching valve was used to collect the effluent of the SEC column every 3 min, and the effluent was automatically injected into the RPLC column. Mass spectrometer was used for peak identification. This system was used to separate Qingkailing injection, a traditional Chinese medicine (TCM). The result showed that the total peak capacity of this system could reach 1134 and the qualitative analysis of seven chemical components of the Qingkailing injection was accomplished by this system. The results show that comprehensive two-dimensional liquid chromatography system is of great importance and high value in the separation of complex TCM.

Chromatography, High Pressure Liquid↗
PubMed2006

Simultaneous determination of geniposide, baicalin, cholic acid and hyodeoxycholic acid in rat serum for the pharmacokinetic investigations by high performance liquid chromatography-tandem mass spectrometry.

A simple, rapid, and specific analytical method for simultaneous determination of geniposide, baicalin, cholic acid and hyodeoxycholic acid in 50 microL samples of rat serum was developed by high performance liquid chromatography-tandem mass spectrometry. The quantification of the target compounds was determined by multiple reaction monitoring (MRM) mode using electrospray ionization (ESI). The correlation coefficients of the calibration curves were better than 0.997. The intra- and inter-day accuracy, precision, and linear range had been investigated in detail. This method was subsequently applied to pharmacokinetic studies of geniposide, baicalin, cholic acid and hyodeoxycholic acid in rats successfully.

Animals↗
PubMed2006

Determination of helicidum and its metabolites in dog plasma by LC/UV/MS/MS and its application to pharmacokinetic studies.

A simple, rapid and reliable method was developed for the identification and quantification of helicidum and its metabolites in beagle dog plasma by liquid chromatography/ultra-violet/electrospray ionization-ion trap mass spectrometry (LC/UV/ESI-ITMS). Two metabolites were identified by MS: formylphenyl-O-beta-d-pyranosyl alloside (I) and hydroxylmethylphenyl-O-beta-d-pyranosyl alloside (II). UV was used for concentration determination with the wavelength of 270 nm. Liquid-liquid extraction was used and the extraction recovery exceeded 90%. Kromacil C(18) column (5 microm, 4.6mm i.d. x 250 mm) was used as the analytical column. Linear detection responses were obtained for helicidum concentration ranging from 1.76 x 10(-4) to 70.4 x 10(-4) micromol/mL (0.050-2.00 microg/mL). The precision and accuracy data, based on intra- and inter-day variations over 3 days, were less than 5%. The limit of determination and quantitation (LOD, LOQ) for helicidum was 0.010 and 0.030 microg/mL, respectively. Pharmacokinetic data of helicidum and the two metabolites were obtained with this method after administration of intravenous injection and a single oral dose of tablets to six beagle dogs, respectively.

Animals↗
PubMed2006

[Study of blending method for the extracts of herbal plants].

The irregularity in herbal plant composition is influenced by multiple factors. As for quality control of traditional Chinese medicine, the most critical challenge is to ensure the dosage content uniformity. This content uniformity can be improved by blending different batches of the extracts of herbal plants. Nonlinear least-squares regression was used to calculate the blending coefficient, which means no great absolute differences allowed for all ingredients. For traditional Chinese medicines, even relatively smaller differences could present to be very important for all the ingredients. The auto-scaling pretreatment was used prior to the calculation of the blending coefficients. The pretreatment buffered the characteristics of individual data for the ingredients in different batches, so an improved auto-scaling pretreatment method was proposed. With the improved auto-scaling pretreatment, the relative. differences decreased after blending different batches of extracts of herbal plants according to the reference samples. And the content uniformity control of the specific ingredients could be achieved by the error control coefficient. In the studies for the extracts of fructus gardeniae, the relative differences of all the ingredients is less than 3% after blending different batches of the extracts. The results showed that nonlinear least-squares regression can be used to calculate the blending coefficient of the herbal plant extracts.

Drugs, Chinese Herbal↗
PubMed2005

Simultaneous determination of nine components in Qingkailing injection by HPLC/ELSD/DAD and its application to the quality control.

High-performance liquid chromatography coupled with photo diode array detection and evaporative light scattering detection (HPLC/DAD/ELSD) was established to simultaneously determine nine ingredients in Qingkailing injection. Four wavelengths at 240, 254, 280 and 330 nm, respectively, were chosen as the monitoring wavelength to determine two nucleosides (uridine and adenosine), geniposide, baicalin and two organic acids (chlorogenic acid and caffeic acid), and an evaporative light scattering detector combined was employed to determine three steroids (cholic acid, ursodeoxycholic acid and hyodeoxycholic acid). This assay was fully validated in respect to precision, repeatability and accuracy. The proposed method was successfully applied to quantify the nine ingredients in 19 different Qingkailing injection samples and by principal component analysis (PCA) and hierarchical clustering analysis (HCA), it demonstrated significant variations in the content of these compounds in the samples from different manufacturers and preparation procedures. This method could be readily utilized as a quality control method for traditional Chinese medicine (TCM).

Chromatography, High Pressure Liquid↗
PubMed2005

Rapid and reliable determination of illegal adulterant in herbal medicines and dietary supplements by LC/MS/MS.

In recent years, dietary supplements and herbal medicines are increasing in popularity all over the world. However, it is problematic that some manufacturers illegally included synthetic drugs in their products. Due to the extremely complex matrices of those products, most existing methods for screening illegal adulterations are time-consuming and liable to false positive. In this paper, a robust LC/MS/MS method for the high-throughput, sensitive and reliable determination of illegal adulterations from herbal medicines and dietary supplements was established. Minimal LC separation was employed and MRM was used to simultaneously monitor the three transitions under their respective optimal collision energy for each compound. Positive results were determined only if well-defined peaks appeared at all of the three transitions and the ratios among the peak areas were within given threshold. In this study, the method had been applied for the screening of nine most commonly adulterated therapeutic substances, such as sildenafil (Viagra) and famotidine, and the lower limits of detection of these compounds ranged from 0.05 to 1.5 ng/ml. Little sample preparation was needed for this method and the analysis time was less than 5 min/sample. The reliability has been demonstrated by the test with blank matrix. Over 200 products that were under suspicion by SDA of China had been assayed and till now no false negative or positive result was found. This method is rapid, simple, reliable and capable of screening multiple adulterants in one run.

Capsules↗
PubMed2005

A microfluidic device using a green organic light emitting diode as an integrated excitation source.

A simply fabricated microfluidic device using a green organic light emitting diode (OLED) and thin film interference filter as integrated excitation source is presented and applied to fluorescence detection of proteins. A layer-by-layer compact system consisting of glass/PDMS microchip, pinhole, excitation filter and OLED is designed and equipped with a coaxial optical fiber and for fluorescence detection a 300 microm thick excitation filter is employed for eliminating nearly 80% of the unwanted light emitted by OLEDs which has overlaped with the fluorescence spectrum of the dyes. The distance between OLED illuminant and microchannels is limited to approximately 1 mm for sensitive detection. The achieved fluorescence signal of 300 microM Rhodamine 6G is about 13 times as high as that without the excitation filter and 3.5 times the result of a perpendicular detection structure. This system has been used for fluorescence detection of Rhodamine 6G, Alexa 532 and BSA conjugates in 4% linear polyacrymide (LPA) buffer (in 1 x TBE, pH 8.3) and 1.4 fmol and 35 fmol mass detection limits at 0.7 nl injection volume for Alexa and Rhodamine dye have been obtained, respectively.

Acrylic Resins↗
PubMed2005

Application of a high-pressure electro-osmotic pump using nanometer silica in capillary liquid chromatography.

A novel designed electro-osmotic pump (EOP) with simple structure was assembled using three 20 cm x 530 microm i.d. fused-silica capillaries packed with 20 +/- 5 nm silica grains for capillary liquid chromatography. It was found that the pump could generate pressures over 20 MPa and several microL/min flow rate for most of the liquids being delivered with the applied voltage less than 10 kV. By increasing the pressure, decreasing the applied voltage and the electrical current, the thermodynamic efficiency was about 1-4%. A practical application of the EOP in a 20cm x 150 microm i.d. 3 microm C18 fused-silica analytical capillary column demonstrated the applicability of the pump.

Chromatography, Liquid↗
PubMed2005

Separation of tissue proteins of human lung carcinomas by partial-filling capillary electrophoresis.

Tissue proteins from human squamous cell lung carcinomas (SQCLC) and small cell lung carcinomas (SCLC) were separated in 0.01% hydroxypylmethyl cellulose (HPMC) linear polymer sieving solutions in the inlet portion of the capillary and next to the outlet of the capillary, followed by capillary zone electrophoresis (CZE) in 40 mM phosphate buffer, pH 2.5. A proper HPMC concentration could cause a molecular sieving effect through the formation of an entangled polymer network. The migration time of the analyte in this matrix depended on the size and electrophoretic mobility of the analyte, the mesh size, and the electric field strength. In the CZE separation, the electroosmotic flow and the charge-to-size ratio of the analyte were important parameters. HPMC concentration and zone length were examined to optimize the separation. Applying this partial-filling technique to the separation of water-soluble proteins from human lung tissues, we found a greatly improved resolution and increased peak intensity. The capillary electrophoresis patterns of normal, SQCLC, and SCLC were obtained and compared for their molecular classifications.

Carcinoma, Small Cell↗
PubMed2005

Proteomics analysis of stage-specific proteins expressed in human squamous cell lung carcinoma tissues.

There is a growing interest in applying proteomics to gain insight into the mechanism of tumorigenesis, develop new markers for molecular diagnosis and accelerate drug development. In an attempt to find new stage-specific tumor markers, patients suffering from squamous cell lung carcinomas (SQCLC) at different pathologic stages have been selected to achieve differential protein expression patterns. Two-dimensional polyacrylamide gel electrophoresis (2-DE) profiles of human SQCLC and normal tissue were compared. Differential protein spots were identified with peptide mass fingerprinting (PMF) based on matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF-MS) and database searching. A total of 63 unique proteins were identified in this experiment. Among them, peroxiredoxin 1 (PRDX1) expression level was significantly increased from stage I to III, and had a slight decrease at stage IV; whereas, a lasting decrease in the expression level of tropomyosins 3 (TPM3), was observed with the malignant progression from I stage to IV stage. These results provide further insight into malignant transformation in SQCLC and proteins may serve as new biomarkers for early diagnosis.

Biomarkers, Tumor↗
PubMed2005

[Simultaneous determination of five groups of components in qingkailing injection by high performance liquid chromatography with photo diode array detector and evaporative light scattering detector].

A method was established for the simultaneous quantification of nine components of five different structural types in Qingkailing injection. High performance liquid chromatography coupled with a photo diode array detector and an evaporative light scattering detector (HPLC-DAD-ELSD) was employed in the determination. Four monitoring wavelengths of 240, 254, 280 and 330 nm were set to determine nucleosides (uridine and adenosine), iridoid glucoside (geniposide), flavone glycoside (baicalin) and organic acids (chlorogenic acid and caffeic acid) respectively, and a combined evaporative light scattering detector was used to detect three steroid compounds (cholic acid, ursodesoxycholic acid and hyodeoxycholic acid). The proposed method permitted the simultaneous separation and determination of five groups of compounds in Qingkailing injection, and acceptable validation results of the precision, repeatability, stability and accuracy tests were achieved. The method was applied to the analysis of 19 Qingkailing injection samples from three different plants, and the results indicated that the method could be used as a convenient and reliable method in the multi-component determination and quality control of traditional Chinese medicines.

Adenosine↗
PubMed2005

[Pharmacokinetics of breviscapine in dogs and rabbits following single intravenous administration].

OBJECTIVE: To study pharmacokinetics of breviscapine in dogs and rabbits after iv. single dose. METHODS: Lc/Lc extract was used to prepare test samples and HPLC was used to determine breviscapine. RESULTS: Breviscaplin was fitted to double-department model in dogs and rabbits after iv. single dose. The main parameters in dogs were: A = 56.93 +/- 23.14, B = 1.61 +/- 1.11, alpha = 0.2328 +/- 0.1321 min, beta = 0.0255 +/- 0.0187 min(-1), t(1/2alpha) = 2.98 +/- 1.42 min, t(1/2beta) = 27.14 +/- 14.35 min, K21 = 0.10312 +/- 0.0112 min(-1), K10 = 0.1904 +/- 0.1319 min(-1), K12 = 0.0367 +/- 0.0306 min(-1), CL = 39.41 +/- 20.44 ml x min(-1), AUC = 3074 +/- 1055 mg x min x L(-1), respectively. The main parameters in rabbits were:A = 2.64 +/- 1.12, B = 0.28 +/- 0.12, alpha = 0.1439 +/- 0.0681 min(-1), beta = 0.0162 +/- 0.0456 min(-1), t1/2alpha = 4.82 +/- 1.65 min, th1/2beta = 42.66 +/- 18.77 min, K21 = 0.0285 +/- 0.0147 min(-1), K10 = 0.0820 +/- 0.00378 min(-1), K12 = 0.0496 +/- 0.0241 min, CL = 337.05 +/- 156.48ml x min(-1), AUC = 356 +/- 114 mg x min x L(-1), respectively. CONCLUSION: Breviscapine has short half-life after intravenous administration to dogs and rabbits,which show breviscapine is eliminated rapidly and has short action time.

Animals↗
PubMed2005

[Estimation of measurement uncertainty of analytical results for the determination of three active components from Gardenia jasminoides Ellis. by HPLC].

OBJECTIVE: To estimate the uncertainty for quantitative analysis results of geniposide, chloregenic acid and crocinl I in Gardenia jasminoides Ellis. METHODS: HPLC method was employed to determine the amounts of geniposide, choloregenic acid and crocinl I in Gardenia jasminoides Ellis. Analyzing the uncertainty sources arising from the procedure of analysis, the standard uncertainty and combined uncertainty and expanded uncertainty were calculated according to the data of HPLC. RESULTS: This method met the requirements of modern pharmaceutical analysis, and the expand uncertainties for the HPLC method of the three components are 0.1024, 0.2254, 0.1264, respectively. CONCLUSION: Applying measurement uncertainty to the evaluation of quantitative analysis results of active components in Gardenia jasminoides Ellis. is an improvement to the actual error evaluation system.

Algorithms↗
PubMed2004

Screening and identification of glycosides in biological samples using energy-gradient neutral loss scan and liquid chromatography tandem mass spectrometry.

A rapid, selective, and reliable strategy has been developed for the screening and identification of glycosides in biological samples: a crude extract was directly infused to a triple-quadrupole MS/MS, and major glycosides were screened out with high confidence by an energy-gradient neutral loss scan (EGNLS) for the loss of sugar(s); then these glycosides were further identified with LC/MS/MS. The proposed EGNLS method was established and optimized with 16 representative glycosides (including ginsenosides and the glycosides of flavones, anthraquinones, and terpenoids). The EGNLS method has two major advantages over the conventional fixed-energy neutral loss scan: (1) The latter is liable to '"omit" some target compounds due to the usual mismatch between the preset collision energy and interested compounds' optimal collision energy (OCE), while EGNLS solves this problem by scanning over an energy range. (2) The EGNLS simultaneously measures the screened compounds' OCE, which not only are essential parameters for further LC/MS/MS analysis but also carry some structural information, as proved by this study. This strategy has been successfully demonstrated with the analysis of glycosides in Scutellaria viscidula Bge and transformed Panaxhairy roots (the glycoside constitutions of both had not been studied before): without laborious separation processes; comprehensive glycoside information on those two plants was obtained by a rapid and simple procedure. This strategy is valuable for the study of glycosides in complex samples.

Chromatography, High Pressure Liquid↗
PubMed2004

[LC-MS analysis of three kinds of Mutong medicinal materials].

Three kinds of Mutong medicinal materials (Lardizabalaceae, Ranunculaceae, Aristolochiaceae) were analyzed qualitatively by LC-MS. The results show Mutong of Lardizabalaceae and Mutong of Ranunculaceae have more the same chemical constituents, and Mutong of Aristolochiaceae has less the same constituents with them. These results are consistent with their medicinal properties and explain the similarity and difference in medicinal properties from chemical basis.

Aristolochia↗
PubMed2003

Molecular recognition between 4a S/R-galanthamine diastereoisomers and alpha-cyclodextrin.

Molecular recognition between 4a S/R-galanthamine diastereoisomers (1: 4a S-galanthamine;2: 4a R-galanthamine) and alpha-cyclodextrin (alpha-CD) were studied by use of docking and molecular dynamics (MD) simulation approaches. The binding energy of constructed 2...alpha-CD complexes is approximately 17 kcal mol(-1) lower than that of 1...alpha-CD, implying a stronger binding ability of 2 with alpha-CD than that of1. The theoretical modeling result is consistent with our previous CZE result, which demonstrated that alpha-CD is an efficient chiral additive for separating 1 and 2. The modeling result also indicates that both hydrophobic interaction and H-bond force may work as major factors for molecular recognition between the galanthamine diastereoisomers and alpha-CD.

Computer Simulation↗