Nano-encapsulation of furosemide microcrystals for controlled drug release

Furosemide microcrystals were encapsulated with polyions and gelatin to control the release of the drug in aqueous solutions. Charged linear polyions and gelatin were alternatively deposited on 5-microm drug microcrystals through layer-by-layer (LbL) assembly. Sequential layers of poly(dimethyldiallyl ammonium chloride) (PDDA) and poly(styrenesulfonate) (PSS) were followed by adsorption of two to six gelatin/PSS bilayers with corresponding capsule wall thicknesses ranging from 45 to 115 nm. The release of furosemide from the coated microparticles was measured in aqueous solutions of pH 1.4 and 7.4. At both pH values, the release rate of furosemide from the encapsulated particles was reduced by 50-300 times (for capsules coated with two to six bilayers) compared to uncoated furosemide. The results provide a method of achieving prolonged drug release through self-assembly of polymeric shells on drug microcrystals.