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Biomedical subjects

Jicun Ren

Publications and source records attributed to Jicun Ren.

At least 19 recordsLinked to original sources
PubMed2006

Study of fluorescence quenching and dialysis process of CdTe quantum dots, using ensemble techniques and fluorescence correlation spectroscopy.

Luminescence properties of quantum dots (QDs) are closely related to their surface structure and chemical properties. In this work some ensemble techniques and fluorescence correlation spectroscopy (FCS) were used to study the fluorescence quenching and dialysis process of CdTe QDs. It is found that when some heavy metal ions, such as silver ions (Ag+), quench QDs, the free Ag+ ions bind with bare Te atoms and form the AgTe structure on the surface. The FCS experimental results show that the quenching process is not the gradual reduction of fluorescence intensity of single QDs, but the decrease in the number of bright QDs with the addition of Ag+ ions. In other words, the bright QDs turn into dark directly in the quenching process. It is observed that some dark QDs converse into the bright QDs in the dialysis experiments and the dialysis process can improve the brightness per QDs. Furthermore, the results of FCS and fluorescence spectroscopy illustrate that the increase of the fluorescence quantum yield (QY) is mainly attributed to the removal of excess unreacted Cd-MPA complex and the possible chemical change of the QDs surface in the dialysis process. These new results can help us to further understand the complex surface structure of water-soluble QDs, improve their surface chemical features, and expand their applications in some fields.

Journal Article↗
PubMed2006

Comparisons between capillary zone electrophoresis and real-time PCR for quantification of circulating DNA levels in human sera.

BACKGROUND: Recently, some research results showed that the circulating DNA in serum or plasma had potential for the molecular diagnosis and prognosis of certain cancers. Several methods have been employed for the quantification of circulating DNA. However, the circulating DNA levels obtained by various methods exhibited considerable differences. Additionally, these methods were labor-extensive and time-consuming, and not suitable for the quantification of circulating DNA in numerous samples due to the use of commercial DNA extraction kits for the purification of circulating DNA. We presented a new method for the quantification of circulating DNA in sera by capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF). METHODS: In the present work, we want to make comparison between CZE-LIF assay and real time PCR for the quantification of circulating DNA levels. Linearity, intra and inter variability of two methods were evaluated. RESULTS: The intra and inter variability of circulating DNA quantification by real-time PCR were 7.3% and 14.92%, respectively. In CZE assay the intra and inter variability were 4.19% and 6.91%, respectively. The R.S.D. values of the same coated capillary and different coated capillaries were 5.14% and 9.02%, respectively. Our data showed that the circulating DNA levels obtained by two methods had a good correlation. Moreover, we further confirmed that blood samples collection, serum preparation and other treatment procedures had a significant impact on the DNA levels in sera. CONCLUSION: Our data further illustrated that CZE-LIF is a simple, rapid and sensitive method for the quantification of circulating DNA in human sera, and well suitable for the analysis of a large number of samples in clinical diagnosis.

Calibration↗
PubMed2006

Microwave-assisted aqueous synthesis: a rapid approach to prepare highly luminescent ZnSe(S) alloyed quantum dots.

In this paper, we present a new procedure for the rapid synthesis of luminescent ZnSe nanocrystals in aqueous phase by microwave irradiation with controllable temperature. The effects of microwave irradiation and experimental conditions on the synthesis of nanocrystals were investigated systematically. It was found that there were significant effects of pH value of reaction solutions, molar ratio of precursors, and heating time of microwave irradiation on the optical properties of the ZnSe nanocrystals. A series of nanocrystals with different size was prepared in 1 h, and the photoluminescence quantum yield reached up to 17% at the optimal reaction condition. The results of HRTEM and XRD showed that the as-prepared nanocrystals had high crystallinity. The characterizations of EDS spectra and elemental analysis showed that the sulfur content of nanocrystals increased with the growth of nanocrystals. We speculated that the structure of nanocrystals was an alloy ZnSe(S) shell on the surface of the ZnSe particles core. Furthermore, we found that the oxygen from air in the reaction vessel played an important role in the decomposition of the thiol group under microwave irradiation.

Journal Article↗
PubMed2006

Characterization of quantum dot bioconjugates by capillary electrophoresis with laser-induced fluorescent detection.

In this paper, we present a universal, highly efficient and sensitive method for the characterization of quantum dot (QD) bioconjugates based on capillary electrophoresis with laser-induced fluorescent (LIF) detection. We first prepared CdTe QDs in aqueous phase by a chemical route with mercaptopropionic acid as a ligand, and then were coupled to certain proteins using bifunctional linkage reagent or electrostatic attraction. The QD bioconjugates were characterized by capillary electrophoresis with LIF detection. We found that QD bioconjugates were efficiently separated with free QDs by the optimization of buffer pH. Furthermore, we found that ultrafiltration was an effective and simple approach to purify QD conjugates with bovine serum albumin (BSA). Due to their broad absorption spectra and size dependent emission wavelength tunability, QDs can be excited to emit different colour fluorescence using a single wavelength laser source, and therefore, we believe that CE with LIF detection will become a universal and efficient tool for the characterization of QD bioconjugates.

Electrophoresis, Capillary↗
PubMed2006

Highly efficient size separation of CdTe quantum dots by capillary gel electrophoresis using polymer solution as sieving medium.

In this paper, we present a new method for highly efficient size separation of water-soluble CdTe quantum dots (QDs) based on CGE using polymer solution as sieving medium. CdTe QDs were synthesized in aqueous phase by a chemical route with mercaptopropionic acid as a ligand. In the alkaline solution, CdTe QDs possess negative charges and migrate to the anode in the electric field. In linear polyacrylamide sieving medium, the migration time of CdTe QDs was increased with the size of CdTe QDs. The effects of some factors, such as types, concentrations, and pH of sieving media, on the separation of CdTe QDs were investigated systematically. Highly efficient separation of CdTe QDs was obtained in linear polyacrylamide sieving medium, and collection of fractions was automatically accomplished by CGE technique. Our preliminary results show that CGE technique is an efficient tool for characterization and size-dependent separation of water-soluble nanoparticles. In addition, the fraction collection in CGE may be useful in certain special applications such as fabrication of nanodevices in the future.

Acrylic Resins↗
PubMed2006

Genetic mutation analysis by CE with LIF detection using inverse-flow derivatization of DNA fragments.

Inverse-flow derivatization is a novel approach to obtain fluorescent DNA derivatives in DNA analysis based on CE with LIF detection. In the present work, we want to explore the feasibility of the application of this method into the mutation detection based on constant denaturant capillary electrophoresis (CDCE) and SSCP analysis. The DNA fragments were first amplified by PCR using a pair of common primers without fluorescent label, and then the mutations were determined by CDCE or SSCP analysis based on CE-LIF with inverse-flow derivatization of DNA fragments. The experimental conditions were investigated systematically, and different labeling modes including inverse-flow derivatization, on-column derivatization and fluorescent labeled primer technique were compared. The inverse-flow derivatization was successfully used in the detection of C677T mutation in the methylenetetrahydrofolate reductase gene by CDCE or SSCP analysis. Our preliminary results demonstrate that inverse-flow derivatization is very simple, inexpensive and sensitive and well suitable for the genetic analysis in clinical diagnosis.

DNA↗
PubMed2006

Capillary electrophoresis of double-stranded DNA fragments using a new fluorescence intercalating dye EvaGreen.

EvaGreen is a new DNA intercalating dye successfully used in quantitative real-time PCR. In the present work, we firstly apply EvaGreen to the analysis of dsDNA by CE with LIF detection. Comparisons of EvaGreen dye with the commonly used dyes SYBR Green I and SYBR Gold were preformed in dsDNA analysis by CE. The linear range of dsDNA using EvaGreen was slightly wider than that using SYBR Gold and SYBR Green I, and the detection limits of dsDNA were not significantly different for the three dyes. Good separations of dsDNA fragments were obtained using the three dyes. Reproducibility of migration time and the peak area of dsDNA fragments with EvaGreen were better than those for SYBR Green I and SYBR Gold. The RSD values were 0.24-0.27% for migration time and 3.45-7.59% for peak area within the same day, 1.35-1.63% for migration time and 6.72-12.05% for peak area for three days. Our data demonstrated that EvaGreen is well suited for the dsDNA analysis by CE with LIF detection.

Benzothiazoles↗
PubMed2006

Fabrication of PDMS/glass microchips by twofold replication of PDMS and its application in genetic analysis.

In this paper, we describe a simple method for fabrication of high quality poly(dimethylsiloxane) (PDMS)/glass microchip by twofold replica molding of PDMS. This technique first served to transfer the negative microchannels from the glass template to the PDMS substrate as a master, and then this PDMS master with positive microchannels was used to replicate the PDMS replica with negative microchannels. Finally, the PDMS replica was bound to a glass sheet by UV radiation. The fabricated microchips were successfully applied for the detection of C677T mutation from the human methylenetetrahydrofolate reductase gene.

Base Sequence↗
PubMed2006

Luminescent quantum dots: a very attractive and promising tool in biomedicine.

Luminescent semiconductor nanocrystals, also known as quantum dots (QDs), are generally composed of II-VI and III-V elements. Due to their quantum confinement of charge carriers in tiny spaces, QDs show some unique and fascinating optical properties, and are characterized as sharp and symmetrical emission spectra, high quantum yields, broad absorption spectra, good chemical and photo-stability and size dependent emission wavelength tunability. Recently, QDs have been successfully used as new fluorescent tags in many biological and biomedical fields, and will become a new promising tool in biomedical studies, clinical diagnostics, drug delivery and photodynamic therapy. In this review, firstly, the methodology of QDs preparation was introduced, which included organic synthesis, aqueous synthesis and microwave assisted aqueous synthesis. Secondly, some procedures for the QDs bio-conjugation with biomarkers were described. And then, some key applications of QDs were summarized, which mainly covered biomedical imaging, immunoassay, DNA hybridization, and photodynamic therapy. Finally, future prospects were discussed.

Animals↗
PubMed2005

A sensitive and rapid immunoassay for quantification of CA125 in human sera by capillary electrophoresis with enhanced chemiluminescence detection.

In this paper we have presented a sensitive and rapid immunoassay (IA) method by capillary electrophoresis with an enhanced chemiluminescence detection system (CE-CL) based on the catalytic effects of horseradish peroxidase (HRP) on the luminol-hydrogen peroxide reaction. The conditions for the CL reaction and electrophoresis were systematically investigated using HRP as a model sample. The linear range from 2.5 x 10(-11) to 1.0 x 10(-9) mol/L (R = 0.999), and the detection limit of 1.0 x 10(-12) mol/L (signal-to-noise ratio = 3) for HRP were achieved using para-iodophenol as CL enhancer. The relative standard deviations of the migration time and peak area for 5.0 x 10(-10) mol/L HRP (n = 7) were 0.26 and 4.8%, respectively, using a CE system with a home-built CL detector. Under the optimal condition, the HRP-labeled CA125 antibody (Ab) and the Ab-antigen complex were well separated within 4 min by CE using a high-pH buffer (pH 10.20). The assay was successfully used for quantification of CA125 in human sera from health controls and patients associated with ovarian cancer, and the recoveries of the standard addition experiments were 93-109%. Our primary results demonstrated that IA based on CE-CL detection is a powerful tool for clinical diagnosis combined with these commercial IA kits.

CA-125 Antigen↗
PubMed2005

On-line chemiluminescence detection for isoelectric focusing of heme proteins on microchips.

In this paper we present a sensitive chemiluminescence (CL) detection of heme proteins coupled with microchip IEF. The detection principle was based on the catalytic effects of the heme proteins on the CL reaction of luminol-H2O2 enhanced by para-iodophenol. The glass microchip and poly(dimethylsiloxane) (PDMS)/glass microchip for IEF were fabricated using micromachining technology in the laboratory. The modes of CL detection were investigated and two microchips (glass, PDMS/glass) were compared. Certain proteins, such as cytochrome c, myoglobin, and horseradish peroxidase, were focused by use of Pharmalyte pH 3-10 as ampholytes. Hydroxypropylmethylcellulose was added to the sample solution in order to easily reduce protein interactions with the channel wall as well as the EOF. The focused proteins were transported by salt mobilization to the CL detection window. Cytochrome c, myoglobin, and horseradish peroxidase were well separated within 10 min on a glass chip and the detection limits (S/N=3) were 1.2x10(-7), 1.6x10(-7), and 1.0x10(-10) M, respectively.

Electrophoresis, Microchip↗
PubMed2004

Separation of purine and pyrimidine bases by capillary electrophoresis using beta-cyclodextrin as an additive.

Capillary electrophoresis was applied to separate purine and pyrimidine bases in the basis of their partial ionization in the alkaline buffer. The effects of buffer pH, buffer and beta-cylclodextrin concentration were systematically investigated using a commercial capillary electrophoresis instrument with UV detector at 254nm. We found that the resolutions of bases (especially for adenine and thymine) were significantly improved in the presence of beta-cylclodextrin. The satisfactory separation of five bases such as cytosine, thymine, adenine, guanine and uracil were achieved by capillary electrophoresis using beta-cylclodextrin as an additive. Under the optimal conditions, the linear range was from 2 to 200microg/ml for bases (R= 0,991-0,9977 ) and the detection limits were from 0.8 to 1.8microg/ml (S/N = 2). The detection limit of 0.05microg/ml ( S/N=2 ) for uracil was obtained by stacking injection mode. The assay was used to determine the deamination of cytosine to uracil by heating in the presence of sodium hydroxide. Our primarily results show that capillary electrophoresis is a very useful tool for determination of purine and pyrimidine bases and study on nucleic acids.

Cyclodextrins↗