Preparation and characterization of methacrylate hydrogels for zeta potential control

A technique based on the measurement of streaming potentials has been developed to evaluate the effects of hydrophilic coatings on electroosmotic flow. The apparatus and procedure are described as well as some results concerning the electrokinetic potential of glass capillaries as a function of ionic strength, pH, and temperature. The effect that turbulence and entrance flow conditions have on accurate streaming potential measurements is discussed. Various silane adhesion promoters exhibited only a slight decrease in streaming potential. A coating utilizing a glycidoxy silane base upon which methylcellulose is applied affords a six-fold decrease over uncoated tubes. Hydrophilic methacrylate gels show similar streaming potential behavior, independent of the water content of the gel. By introduction of positive or negative groups into the hydrophilic methacrylate gels, a range of streaming potential values are obtained having absolute positive or negative signs

STUDIES ON NORETHINDRONE COVALENTLY BONDED TO POLY-N**5(3-HYDROXYPROPYL)-L-GLUTAMINE.

This paper is concerned with the subject of sustained release of drugs from polymeric matrices. Until now only a few examples are available where steroids are covalently bonded to a polymeric system and no data are available about the coupling of steroids to biodegradable polymers. In this paper the authors report a new derivatization of 17 alpha -ethynyl-17 beta -hydroxy steroids which report applicable for attachment to biodegradable poly( alpha -amino acids). The reports covers the following topics - syntheses; in-vivo pharmacokinetic study; in-vitro lability study of carbonate bond between NE and the Spacer Group; in-vitro hydrolysis of compounds VI and VII; in vitro release of drug from compound VIII; immunologic and biocompatibility studies

Dynamic wettability of pHEMA-based hydrogel contact lenses

Standard methods of contact angle analysis include sessile drop, captive bubble and Wilhelmy plate techniques; however, these methodologies are not particularly well suited for assessing the wettability of the surfaces of formed hydrogel contact lenses. This paper describes two methodologies that are adaptations of previously described techniques. The maximum adherent force method is an adaptation of the dynamic Wilhelmy plate technique that allows the assessment of whole, finished contact lenses. The dynamic photographic method allows the simultaneous assessment of the front and back surfaces of strip samples for the assessment of advancing and receding contact angles. Lenses investigated were made from polyhydroxyethyl methacrylate, hydroxyethyl methacrylate/methacrylic acid and hydroxyethyl methacrylate/glycerol methacrylate. The lenses were manufactured by lathing, spin-casting or cast-moulding techniques. Overall, both techniques demonstrated few differences between the wettability of different lens materials and no differences between materials of the 'same' lens type but manufactured by different methods. These findings are consistent with the results of clinical studies, which have shown little difference between contact lens surface wettability in vivo, which may be due to the apparent natural surface wettability-enhancing properties of the pre-lens tear film