pH-dependent mucoadhesion of a poly(N-isopropylacrylamide) copolymer reveals design rules for drug delivery.

This study investigated the mucoadhesive property of a hydrophobically modified copolymer N-isopropylacryamide and glycidylacrylamide NIPAM-N-Gly-(C18)2 (NIPAM-Gly). Prior studies demonstrated that the interfacial properties of this copolymer are pH dependent and that the chains form strong hydrogen bonds at pH < 7 via the carboxylic acid side chains of the glycine moieties. Mucin interactions with the copolymer brushes were investigated by surface plasmon resonance and by direct force measurements. Mucin adsorption was determined as a function of pH, ionic strength, and mucin concentration. It adsorbs to the copolymer strongly at pH 5, but the adsorption decreases with increasing pH. The adsorbed amount is also ionic-strength dependent, decreasing with increasing monovalent salt concentrations at all pH values investigated. When compared with similar investigations with poly(ethylene oxide), these results provide insights into both the chemical characteristics and the solution conditions that determine the mucoadhesive properties of polymers.

Tuning the interfacial properties of grafted chains with a pH switch.

Environmentally responsive, water-soluble polymers have a wide variety of uses ranging from drug delivery to viscosity modifiers. Their utility lies in the ability to use environmental perturbations to dramatically alter the material properties. Here, we describe the interfacial properties of a hydrophobically modified copolymer of N-isopropylacrylamide and glycinylacrylamide (NIPAM-N-Gly-(C18)2), which is both temperature and pH responsive. Direct force measurements quantified the substantial pH-dependent change in the molecular properties of end-grafted NIPAM-N-Gly-(C18)2 monolayers. At pH 8.0, where the glycine side chains are ionized, the polymers exhibit stereotypical polyelectrolyte behavior. Side chain neutralization at pH 5.0 causes a substantial decrease in the film thickness, and the polymer films adhere strongly. The adhesion is presumably through H-bonding between the glycine side chains. Our findings revealed the likely molecular basis of pH-dependent changes in the copolymer films and identified clear design criteria for tuning the interfacial properties of these polymer films.

Hepatitis E virus seroprevalence in children living in rural Ghana.

Large outbreaks of hepatitis E virus have been reported in warm climates with poor sanitation although it exists in endemic form in these areas too. This oro-fecally transmitted infection has been described mainly in adults with very little data from children. This study looked at seroprevalence in children resident in a rural district in Ghana with very little pipe-borne water supply. Sera from 803 randomly selected pupils aged 6-18 years were evaluated for anti-HEV. The overall seroprevalence was 4.4% with seroprevalence increasing from 1% in 6-7 year olds to 8.1% in 16-18 year olds. Females had a significantly higher seroprevalence than males. Anti-seroprevalence was also not influenced by the presence of hepatitis B and C virus markers. Anti-HEV seroprevalence was however, far lower than suspected seroprevalence of hepatitis A virus which is also transmitted oro-fecally. The short life of anti-HEV may be responsible for this low seroprevalence.

Beliefs and practices regarding childhood vaccination among urban pediatric providers in New Jersey.

BACKGROUND: In 1991, the fourth largest measles outbreak in the nation (824 cases) occurred in the Jersey City, New Jersey area. Data from a subsequent intervention trial in Jersey City demonstrated that vaccinations were more likely to be delayed for children who had received care from private rather than public clinic providers. In addition, failure to administer multiple indicated vaccines at a single visit was associated with vaccination delay, and reluctance to administer multiple vaccines was more common among private providers. These findings prompted an investigation of vaccination beliefs and practices among urban pediatric providers. METHODS: A telephone survey of vaccination beliefs and practices was administered to all pediatric providers in both private and public clinics in the Paterson and Jersey City areas. RESULTS: Private providers were less likely than public clinic providers to consider vaccinating children during emergency room visits (relative risk [RR] = 2.2; 95% confidence interval [CI] = 1.2-4.2) or hospital admissions (RR = 13.2; 95% CI = 1.9-92.7) and less likely to believe that all recommended vaccine doses should be administered simultaneously (RR = infinite; lower 95% confidence limit = 3.0). Private providers were less likely to consider administering live-virus vaccines to children with minor acute illnesses and low-grade fever (RR = 2.2; 95% CI = 1.2-3.8) or killed-virus vaccines to children with minor acute illnesses without fever (RR = 3.4; 95% CI = 1.4-8.5) or with low-grade fever (RR = 2.2; 95% CI = 1.2-3.9). Private providers were more likely to believe that multiple injections should be avoided because of potential psychological and physical trauma to the child (RR = 4.0; 95% CI = 1.3-12.3). CONCLUSIONS: Adherence to Standards for Pediatric Immunization Practices by pediatric providers could improve vaccine coverage rates among urban children.