biodegradable 20 - 40 um beads for slow release

[Mark Bradley]

While not specifically relating to drug delivery you might 
like to look at the following references concerning microsphere
delivery systems:

J. of Controlled Release 11: (1990) pp 205-214 Eldridge et al 
Int. J. Pharmaceutics 75: (1991) pp 1-24 Gilligan & Po

There are refs cited in these which refer to development of microsphere
technology

Mark Bradley
CSIRO, Div. Wildlife & Ecology
Canberra 
Australia
Email: mpb at cbr.dwe.csiro.au