Electrochemical immunosensing of low-density lipoprotein based on sol-gel encapsulation

Abstract Lipoprotein monitoring is desirable in the management of medical conditions such as atherosclerotic cardiovascular disease and coronary artery disease, in which controlling the concentration of these chylomicrons is crucial. Current clinical methods are complex and present poor reproducibility between laboratories. For these reasons, recent guidelines discard the assessment of low-density lipoprotein cholesterol (LDL-C) as a routine analysis during lipid-lowering therapies. Concerning the importance of monitoring this parameter, the authors present an electrochemical immunosensor constructed from a simple and easy-to-reproduce platform that allows detecting and quantifying LDL nanoparticles directly from human serum samples. The performance of the biosensor was studied by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The biosensing platform displays good stability and linearity between 30 mg dL-1 and 135 mg dL-1 with a detection limit of 20 mg dL-1. The proposed biosensor can be easily employed for monitoring LDL concentration in clinical treatments.

Simultaneous determination of steroid drugs in the ointment via magnetic solid phase extraction followed by HPLC-UV / 药物分析学报

The copper-coated iron oxide nanoparticles with core-shell were produced by deposition of a Cu shell on Fe3O4 NPs through reduction of Cu2+ ions in solution using NaBH4. Subsequently, the organosulfur compound, bis-(2,4,4-trimethylpentyl)-dithiophosphinic acid (b-TMP-DTPA), was used to form self-assembled monolayer in order to modify sorbent's surface via covalent bonding between Cu and thiol (-SH) terminal groups. The prepared magnetic nanoparticles were characterized by using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and thermo gravimetric analysis (TGA). Then, the application of this new sorbent was investigated to extract the steroid drugs in ointment samples with the aid of ultrasound.An external magnetic field was applied to collect the magnetic nanoparticles (MNPs). The extracted analytes were desorbed using acetonitrile. The obtained extraction solution was analyzed by HPLC-UV. The main affecting factors on the extraction efficiency including pH, sonication time, amount of sorbent, salt concentration, and desorption conditions were optimized in detail. Under the optimum conditions, good linearity was obtained in the range of 2.5-250.0 μg/ L with reasonable linearity (R2 > 0.99) and the limits of detection (LODs) ranged between 0.5 and 1.0 μg/L (based on S/N = 3). Repeatability (intra-day precision) based on five replicates and preconcentration factors were calculated to be 3.6％-4.7％ and 87116,respectively.Relative recoveries in ointment samples at two spiked levels of the target analytes were obtained in the range of 90.0％-103.2％. The results illustrated that the Fe3O4@Cu@ b-TMP-DTPA NPs have the capability of extraction of steroid drugs from ointment samples.

Electrocatalytic Properties of Dopamine and Uric Acid at Vitamin B1 Self-assembled Monolayer Gold Electrode / 分析化学

Vitamin B1 self-assembled monolayer modified electrode (VB1-Au/SAMs/CME) was prepared and its electrochemical behavior was studied by cyclic voltammetry. The results showed that a self-assembled monolayer (SAM) was formed on the surface of gold electrode. \3-/4-redox couple was used as the electrochemical probe to study the electrochemical characteristics of SAM modified gold electrode and the results indicated that the existence of Vitamin B1 membrane on gold surface hindered the electron transfer. The electrochemical behaviors of dopamine(DA) and uric acid (UA) were investigated at VB1-Au/SAMs/CME. The results showed that the electrochemical oxidation of DA and UA could be electrocatalyzed. There were linear relationships between the anodic peak current and the concentration of DA(8.0×10-6-4.0×10-4 mol/L) and UA (6.0×10-5-2.2×10-4mol/L) respectively in differential pulse voltammograms. This modified electrode was effective to detect DA and UA in simultaneous determination of these species in a mixture.

Methods for Cell Micropatterning on Two-Dimensional Surfaces and Their Applications in Biology / 分析化学

The technologies that we call cell micropatterning allow the control of the shape and size of cell adhesion. Combination of micro/nano technology, surface chemistry, electrochemistry and photochemistry enables us to control the adhesion, migration, differentiation of cells and the interactions between different types of cells. These methodologies bring about a new platform for the studies of cell biology. A number of techniques for cell patterning and compares their advantages and disadvantages were reviewed in this article. The applications of cell micropatterning, including those for fundamental studies in cell biology, tissue engineering and cell-based biosensors were also discussed.

A radioimmunoassay method for detection of DNA based on chemical immobilization of anti-DNA antibody

High selectivity provided by biomolecules such as antibodies and enzymes has been exploited during the last two decades for development of biosensors. Of particular importance are efficient immobilization methods for biomolecules in order to preserve their biological activities. In this study, we have evaluated immobilization strategies for an anti-DNA antibody on a self-assembled monolayer of omega-functionalized thiols. The antibody was immobilized via peptide bond formation between the primary amines in the antibody and the carboxyl groups on the self-assembled monolayer. The peptide bond coupling was achieved by activating COOH groups on the surface through N-Hydroxysuccimide (NHS)-ester formation, followed by acylation of NH2 group in the antibody. DNA binding activity of the immobilized antibody was examined by counting beta emission from 35S-labeled DNA.