Yixia Zhang

Biosynthesis of gold nanoparticles using chloroplasts

In this paper, a new method of one-pot biosynthesizing of gold nanoparticles (GNPs), using chloroplasts as reductants and stabilizers is reported. The as-prepared GNPs were characterized by ultraviolet visible spectroscopy, transmission electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy (FTIR). The cytotoxicity of the GNPs was evaluated using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method against gastric mucous cell line GES-1 and gastric cancer cell line MGC-803. Rhodamine 6G as a Raman probe was used for investigating surface-enhanced Raman spectroscopy (SERS) enhancement of GNPs. The transmission electron microscopy results indicated that the GNPs were spherical in structure and almost 20 nm in diameter. Ultraviolet visible spectroscopy exhibited an absorption peak at 545 nm. The GNPs exhibited high crystallinity, with the (111) plane as the predominant orientation, clarified by X-ray powder diffraction. In addition, a potential mechanism was proposed to interpret the formation process of GNPs, mainly based on the analysis of FTIR results. The FTIR spectrum confirmed that the GNPs were carried with N–H groups. Toxicological assays of as-prepared GNPs revealed that the green GNPs were nontoxic. SERS analysis revealed that the GNPs without any treatment could substantially enhance the Raman signals of rhodamine 6G. The Raman enhancement factor was calculated to be nearly 1010 orders of magnitude. In conclusion, the GNPs with good biocompatibility and excellent SERS effect were successfully synthesized using chloroplasts. These biogenetic GNPs have great potential for ultrasensitive detection of biomarkers in vitro and in vivo based on SERS.

Gram scale synthesis of superparamagnetic Fe3O4 nanoparticles and fluid via a facile solvothermal route

Herein, we report a facile solvothermal route for the gram scale synthesis of near monodisperse superparamagnetic Fe3O4 nanoparticles and fluid. The efficacy in generating large scale Fe3O4 nanoparticles arises from the interfacial hydroxyl-aided Ostwald ripening process. Uniform Fe3O4 nanoparticles have been obtained in a high scale (∼1.19 g per one-pot).

A novel HBV genotypes detecting system combined with microfluidic chip, loop-mediated isothermal amplification and GMR sensors

Genotyping of hepatitis B virus (HBV) can be used for clinical effective therapeutic drug-selection. A novel microfluidic biochip for HBV genotyping has been fabricated, for the first time, integrating loop-mediated isothermal amplification (LAMP), line probes assay (LiPA) and giant magnetoresistive (GMR) sensors. Coupling LAMP with LiPA in microfluidic chip shortened reaction time substantially, and combining LAMP with GMR sensor enabled limit of detection to attain 10 copies mL(-1) target HBV DNA molecules in 1 h. Furthermore, the independent designed GMR sensors and microfluidic chip can decrease manufacturing cost and patients test-cost, and facilitate GMR detector repeating use for signal detection. In addition, the detection system has a lower background signal owing to application of superparamagnetic nanoclusters. And it can be expected to use for multiple target molecules synchronous detection in microfluidic chip based on a characteristic of stationary reaction temperature of LAMP. In conclusion, the neoteric detecting system is well suitable for quick genotyping diagnosis of clinical HBV and other homothetic biomolecule detection in biological and medical fields.

Identification of volatile biomarkers of gastric cancer cells and ultrasensitive electrochemical detection based on sensing interface of Au-Ag alloy coated MWCNTs.

Successful development of novel electrochemical biosensing interface for ultrasensitive detection of volatile biomarkers of gastric cancer cells is a challenging task. Herein we reported to screen out novel volatile biomarkers associated with gastric cancer cells and develop a novel Au-Ag alloy composites-coated MWCNTs as sensing interface for ultrasensitive detection of volatile biomarkers. MGC-803 gastric cancer cells and GES-1 gastric mucous cells were cultured in serum-free media. The sample preparation approaches and HS-SPME conditions were optimized for screening volatile biomarkers. Volatiles emitted from the headspace of the cells/medium culture were identified using GC-MS. The Au-Ag nanoparticles-coated multiwalled carbon nanotubes were prepared as a sensing interface for detection of volatile biomarkers. Results showed that eight different volatile metabolites were screened out between MGC-803 cells and GES-1 cells. Two compounds such as 3-octanone and butanone were specifically present in the headspace of the MGC-803 cells. Three volatiles such as 4-isopropoxybutanol, nonanol and 4-butoxy 1-butanol coexisted in the headspace of both the MGC-803 cells and the GES-1 cells, their concentrations in the headspace of the GES-1cells were markedly higher than those in the MGC-803 cells, three volatiles such as formic acid propyl ester, 1.4-butanediol and 2, 6, 11-trimethyl dodecane solely existed in the headspace of the GES-1 cells. The nanocomposites of MWNTs loaded with Au-Ag nanoparticles were prepared as a electrochemical sensing interface for detection of two volatile biomarkers, cyclic voltammetry studies showed that the fabricated sensor could detect 3-octanone in the range of 0~0.0025% (v/v) and with a detection limitation of 0.3 ppb, could detect butanone in the range of 0 ~ 0.055% (v/v), and with a detection limitation of 0.5 ppb, and exhibited good selectivity. The novel electrochemical biosensor combined with volatile biomarkers of gastric cancer owns great potential in applications such as early diagnosis and the prognosis of gastric cancer in near future.

Chloroplasts-mediated biosynthesis of nanoscale Au-Ag alloy for 2-butanone assay based on electrochemical sensor.

We reported a one-pot, environmentally friendly method for biosynthesizing nanoscale Au-Ag alloy using chloroplasts as reducers and stabilizers. The prepared nanoscale Au-Ag alloy was characterized by UV–visible spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). Fourier transform infrared spectroscopy (FTIR) analysis was further used to identify the possible biomolecules from chloroplasts that are responsible for the formation and stabilization of Au-Ag alloy. The FTIR results showed that chloroplast proteins bound to the nanoscale Au-Ag alloy through free amino groups. The bimetallic Au-Ag nanoparticles have only one plasmon band, indicating the formation of an alloy structure. HR-TEM images showed that the prepared Au-Ag alloy was spherical and 15 to 20 nm in diameter. The high crystallinity of the Au-Ag alloy was confirmed by SAED and XRD patterns. The prepared Au-Ag alloy was dispersed into multiwalled carbon nanotubes (MWNTs) to form a nanosensing film. The nanosensing film exhibited high electrocatalytic activity for 2-butanone oxidation at room temperature. The anodic peak current (Ip) has a linear relationship with the concentrations of 2-butanone over the range of 0.01% to 0.075% (v/v), when analyzed by cyclic voltammetry. The excellent electronic catalytic characteristics might be attributed to the synergistic electron transfer effects of Au-Ag alloy and MWNTs. It can reasonably be expected that this electrochemical biosensor provided a promising platform for developing a breath sensor to screen and pre-warn of early cancer, especially gastric cancer.

Breath Analysis Based on Surface-Enhanced Raman Scattering Sensors Distinguishes Early and Advanced Gastric Cancer Patients from Healthy Persons

Fourteen volatile organic compound (VOC) biomarkers in the breath have been identified to distinguish early gastric cancer (EGC) and advanced gastric cancer (AGC) patients from healthy persons by gas chromatography-mass spectrometry coupled with solid phase microextraction (SPME). Then, a breath analysis approach based on a surface-enhanced Raman scattering (SERS) sensor was developed to detect these biomarkers. Utilizing hydrazine vapor adsorbed in graphene oxide (GO) film, the clean SERS sensor is facilely prepared by in situ formation of gold nanoparticles (AuNPs) on reduced graphene oxide (RGO) without any organic stabilizer. In the SERS sensor, RGO can selectively adsorb and enrich the identified biomarkers from breath as an SPME fiber, and AuNPs well dispersed on RGO endow the SERS sensor with an effective detection of adsorbed biomarkers. Fourteen Raman bands associated with the biomarkers are selected as the fingerprints of biomarker patterns to distinguish persons in different states. The approach has successfully analyzed and distinguished different simulated breath samples and 200 breath samples of clinical patients with a sensitivity of higher than 83% and a specificity of more than 92%. In conclusion, the VOC biomarkers and breath analysis approach in this study can not only diagnose gastric cancer but also distinguish EGC and AGC. This work has great potential for clinical translation in primary screening diagnosis and stage determination of stomach cancer in the near future.

One-step synthesis of Fe3O4@C nanotubes for the immobilization of adriamycin

A facile hydrothermal route for one-step synthesis of Fe3O4@C nanotubes (50–100 nm in diameter, several micrometres in length) via rolling graphite oxide sheets has been developed. Functional oxygen groups (e.g., –COOH, –OH and –CO) on the surface of graphite oxide sheets act as the nucleation sites for Fe2+ precipitates. The synthesized Fe3O4@C nanotubes exhibit a strong affinity to adriamycin with a high adsorption capacity (101.3 μg mg−1).

Synthesis of ultrasmall nucleotide-functionalized superparamagnetic γ-Fe2O3 nanoparticles

A novel hydrothermal dephosphorylation route for the synthesis of ultrasmall nucleotide-coated superparamagnetic γ-Fe2O3 nanoparticles (∼5 nm) has been demonstrated. The synthesized γ-Fe2O3 nanoparticles show excellent thermal stability, water dispersion and biocompatibility, allowing possible applications for in vivo X-ray contrast agents.

Preparation of FeCO3–Fe3O4 nanoparticles and flower-like assembliesvia a one-step hydrothermal method

Highly dispersed FeCO3–Fe3O4 nanoparticles with uniform diameters (∼30 nm) and flower-like assemblies (100–150 nm) were prepared by a one-step hydrothermal method. The prepared FeCO3–Fe3O4 composites show good thermal stability, magnetic responsiveness and good adsorption behavior for methylene blue trihydrate in water treatment.

Superparamagnetic Fe3O4–Ag hybrid nanocrystals as a potential contrast agent for CT imaging

Dispersed superparamagnetic Fe3O4–Ag hybrid nanocrystals were successfully synthesized by a seed-assisted hydrothermal strategy. The diameter of the Fe3O4–Ag nanocrystals is 10–20 nm, and the magnetization saturation is over 40 emu g−1. This facilitates their potential applications in magnetic resonance imaging for medical diagnosis.