Biocompatible hydrogels of controlled hydrophobicity from copolymers of N-vinyl-2-pyrrolidone and furfuryl methacrylate.

Biocompatible copolymers of N-vinylpyrrolidone (P) and furfuryl methacrylate (F) were prepared by free radical polymerization in N,N-dimethylformamide solution at 50 degrees C, using 2,2'-azobisisobutyronitrile as initiator, at low and high conversion. The microstructure of copolymers prepared at low conversion was determined from the composition data by the application of statistical relationships, considering the terminal copolymerization model of Mayo-Lewis, whereas for high conversion copolymers the noticeable difference between the reactivity of F and P was taken into consideration. The swelling behaviour of films prepared from solutions of copolymers with different composition was followed gravimetrically and the diffusion of water was analysed on the basis of the stress relaxation model of copolymer chains. The results obtained are in good agreement with second-order diffusion kinetics, showing that the hydrophilic character of the films is controlled mainly by the content of P in the copolymer systems and the distribution of comonomeric units along the copolymer systems.

Self-curing membranes of chitosan/PAA IPNs obtained by radical polymerization: preparation, characterization and interpolymer complexation.

Chitosan/polyacrylic acid I PN's were prepared by radical polymerization of acrylic acid, AA, activated at low temperature, in an aqueous/alcoholic chitosan dispersion. AA monomer to polymer conversion and membrane compositions were determined by elemental analysis and FTIR. Evidences of interpolyelectrolite complex formation were found from the FTIR spectra as well. The gravimetric measurements and the elemental analysis after some exhaustive PAA extraction support the existence of some PAA grafting on the reactive amine group of the chitosan. Swelling degree of the membranes is highly dependent on pH and composition, showing a higher swelling in membranes richer in AA and increased pH due to the breaking of interpolyelectrolite salt bonds.

Long distance runners and body-builders exhibit elevated plasma levels of lipoprotein(a).

A one-point cross-sectional study of 20 sedentary individuals, 20 low-aerobic athletes (body-builders), and 20 high-aerobic athletes (long distance, endurance runners) was conducted in Mexico City, Mexico to determine the influence of these diverse life-styles on the plasma levels of Lp(a). Only non-obese male subjects, aged 23-33, who were nonsmokers, non-alcoholics, and had never used anabolic steroids were included in this study. Blood samples were drawn 24 h following the last period of physical activity, and after a 12-14-h fast-period and a 15-min sitting-rest. Plasma levels of Lp(a) and other parameters, including postheparin lipoprotein lipase (LPL) and hepatic lipase (HL) activities, triglycerides (TG), total cholesterol (TC), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C), as well as % body fat and muscle mass, and maximum aerobic capacity (VO2max) were measured to determine possible correlations with Lp(a) and to serve as convenient internal standards. Mean Lp(a) concentrations were significantly higher in the runners (52 +/- 19 mg/dl) than in the body-builders (40 +/- 6.4 mg/dl, P < 0.05) and the sedentary subjects (24 +/- 5 mg/dl, P < 0.001). Positive correlations between Lp(a) and Vo2max (P < 0.001), HDL-C (P < 0.005) and HDL2-C subfraction (P < 0.005), and a negative correlation with TG were determined. Agglomerative cluster methods suggested three close-distance clusters and a fourth cluster which is composed of four runners who exhibited low LDL-C/HDL-C and high LPL/HL ratios, high mean Lp(a), HDL2-C, and Vo2max levels, but low TG levels. These data show that some individuals who maintain a life-style of very high level physical exertion may have remarkably elevated plasma Lp(a) concentrations. The highly increased concentrations of Lp(a) in high exercise athletes may represent a normal metabolic response to repeated small tissue injuries resulting from frequent and prolonged large muscle movement.

Study of the interpolyelectrolyte reaction between chitosan and alginate: influence of alginate composition and chitosan molecular weight.

The interpolyelectrolyte reaction between chitosan (CHI) and alginate (ALG) was followed by conductimetry and potentiometry. Five chitosan samples, all with almost the same degree of N-acetylation (DA approximately 0.20) and molecular weights ranging from 5 x 10(3) to 2.5 x 10(5) Da were used. The polyelectrolyte complex was formed using alginate samples with three different M/G values (0.44, 1.31 and 1.96). The composition of the complex, Z (Z = [CHI]/[ALG]) resulted 0.70 +/- 0.02, independently of the molecular weight of chitosan and the composition of the alginate used. The degree of complexation was 0.51 with no dependence on the alginate composition.

Passive adsorption of human antirrabic immunoglobulin onto a polystyrene surface.

The latex agglutination immunoassay technique uses polymer colloids as carriers of adsorbed proteins to enhance the antigen-antibody reaction. The aim of the present work is to study the adsorption of Human Antirrabic Immunoglobulin (HA-IgG) on polystyrene latex (PS). The physical adsorption of HA-IgG on PS latex was investigated as a function of pH at 2 mM ionic strength. The amount of HA-IgG adsorbed onto PS latex greatly depends on pH; its value showed a maximum in the neighborhood of the IEP of HA-IgG. The electrophoretic method was applied to characterize latex particles. The influence of the amount of HA-IgG adsorbed (J(ads)) on the electrophoretic mobility and zeta-potential values was also studied.

Chitosan-based hydrogels: synthesis and characterization.

Chitosan (CHI) is a polysaccharide of beta-1,4-linked 2-amino-2-deoxy-D-glucopyranose derived by N-deacetylation of chitin in aqueous alkaline medium. The shells of crustaceans such as crabs, shrimp, and lobster are the current source of chitosan. It is known to be non-toxic, odourless, biocompatible in animal tissues and enzymatically biodegradable. For these reasons much research interest has been paid to its biomedical, ecological, and industrial applications over the past decade. However, its rigid crystalline structure, poor solubility in organic solvents and poor processability have limited its use. To broadening its range of applications, a growth research effort has been devoted to explore ways of modifying Chitosan. Here it has been reported on the synthesis of new hydrogels, obtained by self-curing chitosan with acrylic acid (AA) and methyl acrylate (MA). The hydrogels were characterized by FTIR, swelling and rheological analysis. The results of this study showed that the swelling and mechanical properties of chitosan are highly improved by the presence of poly acrylate. The swelling degree of these materials does not depend upon the ratio MA/AA. It is possible to improve and modulate the mechanical properties of the hydrogels by changing the relative MA/AA ratio.