Gamma radiation-induced crosslinked composite membranes based on polyvinyl alcohol/chitosan/AgNO3/vitamin E for biomedical applications.

Crosslinked hydrogel composite membranes based on polyvinyl alcohol (PVA) and chitosan-loaded AgNO3 and vitamin E were prepared using gamma irradiation. Chitosan has been used as antimicrobial blend materials to provide further biocompatibility for the prepared composite hydrogel membranes. The crosslinking reaction between PVA and chitosan owing to gamma irradiation was verified and characterized by FTIR analysis, while the morphology of hydrogel composite membranes was investigated by SEM. Important parameters affecting on hydrogel membranes formation, such as copolymer concentration, irradiation dose, AgNO3 concentration, plasticizer, and vitamin E of PVA/chitosan membranes were evaluated and discussed in details. In addition, the mechanical and thermal properties of hydrogel composite membranes were examined to evaluate the possibility of its application for wound dressings. The results revealed that the gelation (%) of hydrogel membranes increased dramatically with PVA composition, irradiation dose and glycerol content up to 20%; however, it decreased with AgNP incorporation due to the viscosity of copolymer composition is hyper-increased. The swelling ratio of composed hydrogel membranes decreased notably with increasing the radiation dose and incorporation of AgNP, due to reducing of the crosslinking degree of formed hydrogel membranes. PVA-Cs-Ag composed hydrogel membranes showed significant antimicrobial activity in particular against Streptococcus mutans due to the presence of AgNP in membranes, compared to other bacteria and fungi microbes. Thus, the PVA/chitosan/AgNO3-Vit.E hydrogel composite membranes showed satisfactory properties for use as wound dressing materials.

Bioprocess development for production of alkaline protease by Bacillus pseudofirmus Mn6 through statistical experimental designs.

A sequential optimization strategy, based on statistical experimental designs, is employed to enhance the production of alkaline protease by a Bacillus pseudofirmus local isolate. To screen the bioprocess parameters significantly influencing the alkaline protease activity, a 2-level Plackett-Burman design was applied. Among 15 variables tested, the pH, peptone, and incubation time were selected based on their high positive significant effect on the protease activity. A nearoptimum medium formulation was then obtained that increased the protease yield by more than 5-fold. Thereafter, the response surface methodology (RSM) was adopted to acquire the best process conditions among the selected variables, where a 3-level Box-Behnken design was utilized to create a polynomial quadratic model correlating the relationship between the three variables and the protease activity. The optimal combination of the major medium constituents for alkaline protease production, evaluated using the nonlinear optimization algorithm of EXCEL-Solver, was as follows: pH of 9.5, 2% peptone, and incubation time of 60h. The predicted optimum alkaline protease activity was 3,213 U/ml/min, which was 6.4 times the activity with basal medium.

Anticoagulation for cardioversion of atrial fibrillation.

The cardioversion of chronic atrial fibrillation to sinus rhythm carries a thromboembolic risk of 1.5-6%. These events occasionally occur at the time of cardioversion, but more often happen hours or days later. These strokes and other embolic events may occur even where atrial thrombus has been excluded before cardioversion and it has become apparent that, although atrial electrical activity may be restored by cardioversion, normal mechanical atrial function may take longer to recover. Numerous studies have addressed the role of anticoagulation following cardioversion in patients with atrial fibrillation, however, the mechanism of embolic complications as well as the justification of a standard anticoagulation therapy are not fully established. In this review we will try to present an overview of the mechanisms of thrombosis following cardioversion and give an insight into current anticoagulation strategies.

Increased release of the soluble form of the adhesion molecules L-selectin and ICAM-1 but not E-selectin during attacks of angina pectoris.

Myocardial ischemia leads to the activation of neutrophils as well as endothelial cells. The interaction between these cells is dependent on certain adhesion glycoproteins which are expressed on their surface. Adhesion of neutrophils to endothelium, mediated by adhesion molecules, has been shown to result in coronary capillary plugging and impairment of coronary blood flow. In certain conditions, upon cell activation, adhesion proteins may be released in soluble form into the circulating blood. The purpose of our study was to verify whether myocardial ischemia occurring during angina episodes results in the release of the soluble adhesion molecules, L-selectin, E-selectin, and intracellular adhesion molecule-1 (ICAM-1), into the circulation. Plasma samples were collected by venepuncture from 15 patients admitted to the emergency room with chest pain caused by attacks of angina pectoris and 15 patients with noncardiac chest pain. To confirm the diagnosis, all patients underwent an exercise stress test and, if not conclusive, 99mTc MIBI SPECT or coronary arteriography. Another set of plasma samples were taken from each patient in the absence of chest pain. In addition, blood for analysis was obtained from 15 sex-and age-matched healthy subjects. Soluble adhesion molecules plasma levels were measured by standard enzyme-linked immunosorbent assay. In patients with angina pectoris, plasma levels of soluble L-selectin estimated during chest pain were significantly higher than in the control group and decreased in the absence of chest pain. Similarly, the mean concentration of soluble ICAM-1 at the time of angina onset was significantly elevated in the patients in comparison with the control group and remained higher, although not significantly, in the absence of chest pain. In patients with noncardiac chest pain, plasma levels of soluble L-selectin did not differ significantly from those observed in control subjects. In this group of patients, the plasma levels of soluble ICAM-1 estimated during pain onset and in the absence of this symptom were not significantly elevated. On the contrary, the mean values of soluble E-selectin in the patients with ischemic cardiac pain during chest pain and in the absence of this symptom, as well as those in the patients with noncardiac chest pain during or without symptoms, remained unchanged in comparison with the control group. During attacks of angina pectoris an increase in the plasma levels of the soluble adhesion molecules, ICAM-1 and L-selectin, was noted, possibly reflecting activation of neutrophils and endothelial cells during myocardial ischemia. However, E-selectin plasma levels remained unchanged in response to myocardial ischemia.