pH- and Thermo-sensitive Hydrogel Nanoparticles.

pH- and temperature-sensitive hydrogel nanoparticles of copolymers of vinylpyrrolidone (VP) and acrylic acid (AA) cross-linked with NN' methylene bis acrylamide (MBA) of sizes up to 50 nm diameter loaded with marker compound FITC-dextran (mol wt. 19.3 kD) were prepared in the aqueous core of reverse micellar droplets and were dispersed in aqueous buffer. These particles have high entrapment efficiency, and the lyophilized powder can be redissolved in buffer without any significant agglomeration. The release of FITC-dextran from these particles was found to be pH- and temperature-dependent. The release was slow in acid solution, but it increased considerably as the pH of the medium was increased. The release rate was also increased with the increase of temperature. Copyright 1998 Academic Press.

Size Modulation of Polymeric Nanoparticles under Controlled Dynamics of Microemulsion Droplets

Polyacrylamide nanoparticles of different size (<100 nm) were prepared in reverse micelles under various dynamic conditions of micellar systems. The nanoparticles were always larger than the aqueous core in which they were formed; however, the size of the nanoparticles could be controlled if the interdroplet interaction and coalescence rate in reverse micelles were regulated. Factors such as interfacial rigidity of the droplets, size of the aqueous core, temperature, and concentrations of acrylamide (monomer) and N ,N '-methylenebisacrylamide (crosslinking agent) have a profound effect on the size of nanoparticles. By adjustment of these parameters in reverse micelles, nanoparticles ranging from about 10 to more than 100 nm have been prepared.