PROVIDENCE, R.I.--In the current issue of the journal Nature, a team of Brown University scientists reports the production of drug-filled microscopic polymer spheres that when taken orally enter the bloodstream by crossing the intestinal lining, travel body-wide and degrade, releasing their therapeutic load. The process dramatically increases the oral effectiveness of several drugs. It suggests a new oral delivery system for compounds, such as insulin, which until now could not be delivered orally.
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The researchers describe the enhanced absorption of three therapeutic compounds with widely different properties encapsulated in microspheres made of "bioerodible" polymers. The compounds are the anticoagulant dicumarol, plasmid DNA, which is a material used in gene therapy, and insulin, used to treat diabetes.
The spheres are engineered from biodegradable plastics, which become more adhesive to body tissues as the plastics degrade in water. The spheres range in size from 0.1 to 5 micrometers. For purposes of comparison, one thousand 1-micrometer spheres could fit end-to-end on a pinhead. A novel proprietary process, dubbed PIN for "Phase Inversion Nanoencapsulation," was used to produce the spheres and efficiently enclose the drugs.
In the study, microspheres made of the bioadhesive or "sticky" plastics stayed in contact with the intestines longer than spheres made of other materials. The microspheres moved through the intestinal wall and between individual cells as early as one hour after being fed to rats. After three and six hours, there was an intense uptake of the spheres by cells lining the intestines, liver and spleen.