Deliang He

A study of adsorption behavior of human serum albumin and ovalbumin on hydroxyapatite/chitosan composite.

In situ adsorption of human serum albumin (HSA) and ovalbumin (OVA) was real-time monitored by piezoelectric quartz crystal impedance (PQCI) technique to fully understand the initial cellular response on hydroxyapatite/chitosan (HAP/CS) composite. The PQCI parameters, such as resonant frequency (f), static capacitance (C(s)), and motional resistance (R(m)) were measured for investigating the kinetic adsorption behaviors of both proteins. The change in frequency shifts (Deltaf) depends on the amount of the adsorbed protein, and the change in motional resistance (DeltaR(m)) results from the microporosity variation of HAP/CS coating. The results show that the amount of the absorbed HSA is much greater than that of OVA on HAP/CS coating because of the unique construction of HSA as well as a flexible protein. Furthermore, Deltaf and DeltaR(m) data were fitted according to the kinetic exponential decay equations. It can be seen that there is only one adsorption process for OVA, but the absorption process for HSA is followed by a rearrangement process, and the former process is faster than the rearrangement process. Subsequently, the composite binding with proteins were demonstrated by the Fourier transform infrared (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Bulk acoustic wave sensor using molecularly imprinted polymers as recognition elements for the determination of pyrimethamine

A new bulk acoustic wave (BAW) sensor modified with a molecularly imprinted polymer (MIP) was fabricated and applied for the determination of pyrimethamine. This sensor exhibited high selectivity and sensitive response to pyrimethamine. Factors such as pH and the amount of coating influencing sensor properties, were investigated in detail and optimized. The calibration curve was linear in the range 6.0x10(-7)-1.0x10(-4) M. The determination limit was 2.0x10(-7) M. In harsh chemical environments such as high temperature, organic solvents, bases, acids, etc., the sensor still exhibited long-term stability. The proposed method has been satisfactorily applied for the determination of pyrimethamine in serum and urine media.

A new study of the enzymatic hydrolysis of carboxymethyl cellulose with a bulk acoustic wave sensor

A new bulk acoustic wave (BAW) cellulase sensing technique, which is based on the enzymatic hydrolysis process of sodium carboxymethylcellulose (CMC) by cellulase, was established. The frequency shift curves of BAW sensor indicated that the viscosity of the tested solutions decreased during the hydrolysis process. The hydrolysis rate of CMC by cellulase was calculated from the frequency shift curves. The hydrolysis rate of CMC under different pH conditions at 30 degrees C showed that cellulase had high hydrolysis ability approximately at pH 5.0. Kinetic parameters (the Michaelis constant K(m) and the maximum rate V(max)) of the process were estimated by using a linear method of Lineweaver-Burk plot. K(m) is 1.95+/-0.25 mg ml(-1) and V(max) is -(4.25+/-0.58) x 10(-3) g(1/2) cm(-3/2) cP(1/2) min(-1). Also the activation energy (E(a)) of the enzymatic hydrolysis, with a value of 51.99+/-1.26 kJ mol(-1), was estimated in this work.

α-Amylase immobilized on bulk acoustic-wave sensor by UV-curing coating

A new method for immobilization of alpha-amylase by UV-curing coating is proposed in this paper. The immobilization procedure of UV-curing coating on piezoelectric quartz crystal is simple and convenient, and causes less loss of enzymatic activity. The activity of the immobilized alpha-amylase is monitored by a technique based on bulk acoustic-wave (BAW) sensor. The frequency shift of BAW sensor can reflect the degree of hydrolysis of starch by the immobilized alpha-amylase. It is appropriate for the immobilized alpha-amylase to hydrolyze the soluble starch under pH 7.0 condition, which is similar to that of the free alpha-amylase. Kinetic parameters (the Michaelis constant, K(m), and the maximum initial rate V(max)) of the enzymatic hydrolysis of starch by the immobilized alpha-amylase are estimated by using a linear method of Lineweaver-Burk plot. K(m)=12.7mgml(-1) and V(max)=15.9Hzmin(-1). And the experimental results show that the immobilized alpha-amylase entrapped by the UV-curing coating retains adequate enzymatic activity and can be reused more than 50 times under certain experimental conditions.

Preparation of a novel nanocomposite of polyaniline core decorated with anatase-TiO 2 nanoparticles in ionic liquid/water microemulsion

Polyaniline core decorated with TiO2 (PANI-TiO2) nanocomposite particles was successfully synthesized in ionic liquid/water (IL/water) microemulsion in the presence of anatase TiO2 nanoparticles. The TiO2 nanoparticles had been dispersed beforehand in OP-10 and n-butanol to weaken the strong particles agglomeration of TiO2. The PANI-TiO2 nanocomposites were characterized by fourier transform infrared spectroscopy (FTIR), ultraviolet visible spectroscopy (UV-Vis), scanning electron microscopy (SEM), and transmission electron microscope (TEM), and their electrochemical behavior was estimated by the electrochemical workstation. SEM micrographs showed that the nanocomposites exhibited spherical morphology with particle sizes about 70 nm. The TEM result showed that the PANI-TiO2 nanocomposites had a novel structure and that nanocrystalline TiO2 deposited onto the surface of PANI, which was different from the reported structure of TiO2-PANI nanocomposites. Both FTIR and UV-Vis spectra indicate that polyaniline and nano-TiO2 particles are not simply blended or mixed up. A possible reaction mechanism for this nanocomposite preparation is suggested and analyzed.

Preparation and Properties of Polyaniline Codoped with Ionic Liquid and Dodecyl Benzene Sulfonic Acid or Hydrochloric Acid

Three nanosized polyaniline (PAn) powders doped with ionic liquid and dodecyl benzene sulfonic acid (DBSA) or hydrochloric acid have been prepared for the first time in an ionic liquid-water emulsion system. The oil-phase ionic liquid is used as both a monomer solvent and doped counterion. The effects of different counterions on the properties (molecular weight, electrical conductivity, glass transition temperature, electrochemical activity) of PAn are investigated. PAn codoped with 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid and DBSA shows the highest molecular weight (81 104 g mol−1), the highest electrical conductivity (1.85 S cm−1), the lowest glass transition temperature (181°C) and the highest redox reaction current density; PAn doped with an ionic liquid only exhibits the lowest conductivity (0.0018 S cm−1) and a lower redox reaction current density. PAn codoped with ionic liquid and HCl shows higher conductivity. They also exhibit good electrochemical stability and charge-discharge performance. These indicate that codoping of different counterions under acidic conditions could improve the degree of oxidation and doping ratio of PAn and could result in high electrical conductivity and good electrochemical properties.

A study of the viscoelasticity of zinc phosphate coatings using a quartz crystal impedance system

Abstract Zinc phosphating processes in manganese-modified low-zinc phosphating baths have been studied firstly by employing an in-situ quartz crystal impedance system (QCIS) which allows rapid and simultaneous measurements of admittance spectra of the piezoelectric quartz crystal (PQC) resonator. The conductance ( G ) and susceptance ( B ) data are acquired synchronously by QCIS and used to obtain the maximum conductance ( G max ), the half bandwidth (Δ f whh ) of the curve of G and scanning frequency ( f ), and thereby the quality factor ( Q ) of zinc-coated PQC. The experimental results show that the viscoelasticity changes of zinc phosphate coatings can be assessed by the variations of these parameters during the phosphating. The effects of an accelerator (NaNO 2 ) on the viscoelasticity change of zinc phosphate coatings are also discussed in detail. It is shown to be found that the viscoelasticity of zinc phosphate coatings decreases with phosphating time and the concentration of NaNO 2 .

Real-time monitoring of zinc phosphating process by quartz crystal impedance system

Abstract The zinc phosphating process in manganese-modified low-zinc phosphating baths has been monitored firstly by an in situ quartz crystal impedance system (QCIS) which allows rapid and simultaneous measurements of admittance spectra of the zinc-coated piezoelectric quartz crystal (PQC) resonator. The electrical equivalent circuit parameters are obtained by non-linear least square regression analysis of synchronously acquired conductance and susceptance data. The experimental results show that the kinetic growth process of zinc phosphate coating can be monitored on-line by measuring the equivalent circuit parameters and frequency shifts of the zinc-coated PQC resonator. According to the motional inductance (Lm) change of zinc-coated PQC during zinc phosphating treatment, the whole process can be divided into four regions: pickling reaction, exponential growth, linear growth and exponential decay growth, respectively. And effects of inorganic additives (Ni2+ and/or Mn2+) on the properties and performance of zinc phosphating coatings as well as the variations of equivalent circuit parameters of zinc-coated PQC during the phosphating treatment are also investigated.

Non-Aqueous Assay System for Phenobarbital Using Biomimetic Bulk Acoustic Wave Sensor Based on a Molecularly Imprinted Polymer

ABSTRACT A new biomimetic bulk acoustic wave (BAW) sensor based on a molecularly imprinted polymer (MIP) was fabricated and applied for the determination of phenobarbital The MIP was synthesized using phenobarbital as the template molecule and methacrylic acid as the functional monomer by the non-covalent method. In absolute ethanol, the sensor exhibited good selectivity and sensitivity. A linear relationship between 9.0×10−8 M and 5.0×10−5 M was revealed. The determination limit was 5.0×10−8 M. In harsh chemical environments such as high temperature, organic solvent, bases, acids, etc., the sensor still exhibited long-time stability. Satisfactory results of real sample assay were obtained by the proposed method.

A new study of the degradation of hyaluronic acid by hyaluronidase using quartz crystal impedance technique

A new quartz crystal impedance sensing technique for the assay of hyaluronidase (HAse) activity is presented. It is based on the changes in viscosity and density during the enzymatic hydrolysis of hyaluronic acid (HA) by HAse. The variations of equivalent circuit parameters of piezoelectric quartz crystal (PQC) during the enzymatic degradation are discussed. The motional resistance shift curves indicate that the viscosity of the test solutions decreases during the hydrolysis process. The initial hydrolysis rates of HA are obtained from changes in viscosity and density as a function of incubation time. Kinetic parameters (the Michaelis constant K(m) and the maximum hydrolysis rate V(max)) of the degradation reaction are estimated by using a linear Lineweaver-Burk plot in this work. The K(m) was 0.44+/-0.03 mg.ml(-1) and the V(max) was -(5.29+/-0.36)x10(-3) kg.m(-2).s(-1/2).min(-1).