Multimodal and multifunctional stealth polymer nanospheres for sustained drug delivery

We report the preparation of fluorescent and magnetic PMMA nanospheres, and a corresponding PEGylated 'stealth' analogue prepared using a block copolymer. The nanospheres contain encapsulated magnetite nanoparticles and fluorescent BODIPY dyes, including a new such dye with pH-sensitive fluorescent emission. The new dye could potentially be used as an indicator of the immediate physiological environment. The nanospheres were non-toxic at up to 500 mu g ml super(-1) in PC12 cells. Lomerizine, a lipophilic calcium channel blocker, was also encapsulated in the nanospheres and displayed sustained, pH-dependent release characteristics. The nanospheres may be of use to release lomerizine and other water-insoluble drugs at central nervous system injury sites.