Synthesis of biodegradable thermo- and pH-responsive hydrogels for controlled drug release

Novel intelligent hydrogels composed of biodegradable and pH-sensitive poly(L-glutamic acid) (PGA) and temperature sensitive poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) (PNH) were synthesized and characterized for controlled release of hydrophilic drug. The influence of pH on the equilibrium swelling ratios of the hydrogels was investigated. A higher PNH content resulted in lower equilibrium swelling ratios. Although temperature had little influence on the swelling behaviors of the hydrogels, the changes of optical transmittance of hydrogels as a function of temperature were marked, which showed that the PNH part of hydrogel exhibited hydrophobic property at temperature above the lower critical solution temperature (LCST). The biodegradation rate of the stimuli-sensitive hydrogels in the presence of enzyme was directly proportional to the PGA content. Lysozyme was chosen as a model drug and loaded into the hydrogels.

Investigations on the adsorption behavior of Neutral Red on mercaptoethane sulfonate protected gold nanoparticles

A detailed investigation on the adsorption behavior of Neutral Red (NR) molecules on mercaptoethane sulfonate-monolayer protected gold clusters (MES-MPCs) has been conducted by the spectroscopic method. It is found that cationic NR molecules are adsorbed on the negatively charged MPCs surfaces via electrostatic attractive forces. The absorption study shows that the optical properties of NR molecules are significantly influenced upon the adsorption. Based on the electrostatic adsorption nature and the excellent stability of MES-MPCs against the electrolytes, this association can be released by the addition of electrolyte salts, which can be monitored by both absorption and fluorescence spectroscopy. In addition, dication Ca2+ is found to be more effective in the release of NR than univalent Na+. Moreover, the MES-MPCs exert energy transfer quenching of NR fluorescence by both static and dynamic quenching. However, static quenching seems to be the dominating quenching mechanism. Furthermore, this energy transfer quenching exhibits strong dependence of Au core size, and 5.0 nm MPCs show stronger ability in quenching the NR fluorescence than that of 2.7 nm MPCs.

Synthesis and thermoelectric properties of Ca2.6Nd0.4Co4O9 compound

The layered cobaltite Ca2.6Nd0.4Co4O9 was synthesized by the solid-state reaction. Their crystal structure was determined by the X-ray powder diffraction and CELL program. The prepared Ca2.6Nd0.4Co4O9 compound has the monoclinic symmetry. The electrical conductivity and Seebeck coefficient were measured from room temperature to 700 degreesC in air. Both the properties increase while rising temperature. The thermoelectric power of Ca2.6Nd0.4Co4O9 is about 242.4 muV (.) K-1. The results imply a promising way to enhance the thermoelectric properties of the layered cobaltite oxides by optimizing their composition and microstructure.

Computer simulation for effect of Tb3+ on Ca2+ speciation in human plasma

Effect of Tb3+ on Ca2+ speciation in human plasma was studied by means of the computer program of MINTEQA2. When Tb3+ ions are not added into the system, Ca2+ ions mostly distribute in free Ca2+ (74.7%) and the surplus distributes in Ca2+ complexes, such as [CaHCO3](+) (7.9%),[Ca(Lac)](+) (6.4%), CaHPO4 (1.3%), [CaHistidinateThreoninateH(3)](3+) (2.4%), [CaCitrateHistidinateH(2)] (2.3%) and CaCO3 (1.1%). Tb3+ can compete with Ca2+ for inorganic as well as biological ligands. An increase of concentration of Tb3+ in the system results in an increase of content of free Ca2+ and a decrease of contents of Ca2+ complexes.

Induction effect of Ca2+ on ion-channel behavior of supported phospholipid membranes

As a kind of supported bilayer lipid membranes, hybrid bilayer membrane (HBM) was applied to the interaction between Ca2+ and lipid for the first time. By using Fe(CN)(6)(3-) as a probe, we found that Ca2+ could induce the ion channel of HBM to be in open state. STM images study proved this phenomenon.

Effects of La3+ and Gd3+ on Ca2+ influx in rat hepatoma H-35 cells

Effects of La3+ and Gd3+ on Ca2+ influx were investigated in rat hepatoma H-35 cells by measuring the initial rate of Ca-45(2+) uptake. It was found that the maximum initial rate of Ca2+ uptake was increased six- to ten-fold at low concentrations of La3+ and Gd3+. Kinetic analyses by measuring the initial rate of Ca2+ influx at different external Ca2+ concentrations indicated the existence of two intracellular exchangeable components in the basal Ca2+ system, with low and high affinities for Ca2+, and only one class of Ca2+ binding sites was observed in the La3+- or Gd3+-treated cells. For high affinity, La3+ and Gc(3+) increased both kinetic parameters K-m and V-max of basal Ca2+ influx. La3+ and Gd3+ compete directly with Ca2+ for Ca2+ binding site for low affinity. The kinetics is competitive.

Probe beam deflection study on electrochemically controlled release of 5-fluorouracil

In this paper, the polypyrrole (PPy) film modified electrodes are used as an electroreleasing reservoir. The electrochemically controlled release of 5-fluorouracil (5-FU) from a PPy film modified electrode to aqueous electrolytes is studied by the in situ probe beam deflection (PBD) method combined with cyclic voltammetry (CV) and chronoamperometry (CA). The PBD results reveal that the release of 5-FU from PPy film depends on the electrochemical redox process of the PPy film electrode. The released amount is controlled by the reduction potential and is proportional to the thickness of the film. The exchange of 5-FU anions with Cl- on an open circuit is slow on the time scale of minutes, but the release of 5-FU anions can proceed quickly at -0.6 V (vs Ag/AgCl). The amount of released 5-FU decreases with the time that the PPy film is soaked in aqueous solution. (C) 1998 Elsevier Science Ltd. All rights reserved.

ELECTROCHEMICAL CONTROLLED-RELEASE OF ADENOSINE-TRIPHOSPHATE

Polypyrrole (PPy) film was synthesized by anodic polymerization of pyrrole onto the surface of platinum electrode in the solution of sodium p-toluene sulfonate (NaTsO). When this film was oxidized anodically in an aqueous solution of adenosine triphosphatle (ATP), the ATP anions were incorporated into the film. Release of ATP From the film could be accomplished by reduction of the film in aqueous electrolyte solution. The total amount of ATP released from the film was determined by UV spectroscopic method.

ELECTROCHEMICALLY CONTROLLED RELEASE OF ADENOSINE 5'-TRIPHOSPHATE FROM POLYPYRROLE FILM

Polypyrrole (PPy) film is synthesized by anodic polymerization of pyrrole onto the surface of a platinum electrode in the presence of toluene-p-sulfonate and the film is used for the controlled release of the neurotransmitter, adenosine 5'-triphosphate (ATP).