EFFECT OF HUMAN SERUM ON THE PH-INDUCED RHEOLOGICAL PROPERTIES OF POLYMETHACRYLIC ACID

The use of polyelectrolytes have been proposed for the production of pH sensitive microcapsules and liposomes. Polymethacrylic acid (PMA) has been synthesized for this purpose and has been shown to be extremely effective in increasing the release from these delivery systems a pH's below 6.0 in distilled water. The current studies show that serum and ionic strength conditions dramatically effect the rate and extent of any PMA conformational changes. The rate of conformational change was found to be proportional to time in contrast to the cube root of time reported within molecular probe investigations. Conformational changes in this study have been monitored using a cone/plate rotational viscometer. The results of this study suggest that under biologically relevant conditions, PMA (Mv 400,000) may not be suitable for use in pH sensitive delivery systems buy may have other important uses.