Double-walled polymer microspheres for controlled drug release

Abstract

One approach to the controlled release of drugs involves incorporation of the drug molecules into the matrix of microscopic polymer spheres or capsules. Existing methods for preparing such microparticles do not, however, always guarantee a constant release rate, for example because drug molecules may be trapped preferentially at the surface, because they have to diffuse through an increasing thickness of polymer when the particles are non-eroding or because the surface area changes for eroding particles. In other situations pulsed release may be required--an application to which simple polymer microspheres do not readily lend themselves. Multi-walled microspheres might solve some of these problems. Here we describe a one-step process for preparing double-walled polymer microspheres with diameters ranging from about 20 to 1,000 micrometers. Our technique involves the phase separation of a polymer mixture owing to solvent evaporation: with an appropriate choice of interfacial tensions and evaporation rate, a spherical droplet of one polymer becomes coated with a highly uniform layer of the other. This process, which might be adapted to yield multi-walled microspheres, should make possible the engineering of highly specific drug-release properties.

Fabrication of Janus particles composed of poly (lactic-co-glycolic) acid and hard fat using a solvent evaporation method

“…In addition to the extraction rate, there may be other factors that affect the formation of Janus particles including the balance of interfacial tension. The conformation of particles composed of two materials has been reported to be affected by the interfacial tension between the phases of both materials in the dispersed oil phase and between the continuous aqueous phase and each phase in dispersed oil phase (27). The investigation of the effect of the balance in the interfacial tension will be the focus of our next investigation.…”

NanoCipro encapsulation in monodisperse large porous PLGA microparticles

“…3 and 4) suggest that the canola oil had a similar affinity for the aqueous extraction phase as PLGA. The thermodynamics of this phenomena, which considers interfacial tension effects on spreading coefficients, have been addressed thoroughly in the context of microencapsulation by Mathiowitz and others [30,31] as well as in other previous reports [20,32]. The two competing effects are the rate at which the boundary is moving (convection), and the rate at which the oil is diffusing through the medium.…”

Poly-L-lysine improves gene transfer with adenovirus formulated in PLGA microspheres

“…Samples were viewed with an Hitachi S-4000 scanning electron microscope with a field emission electron source. 34 HPLC/Mass spectrometry (LC/MS) analysis: The samples to be quantified using the LC/MS were prepared by the addition of different concentrations of PLL to a standard virus solution to attain a range of PLL:viral particle ratios (10 6 , 5 × 10 5 , 10 5 , 5 × 10 4 , 10 4 5 × 10 3 , 10 3 , 500, 100, or 50 to 1). The adenovirus content in each sample was 10 9 particles.…”