Fillable polymer microparticles offer a new means for delivering vaccines

Three-dimensional printing is a powerful technique for rapid prototyping, but when put into practical use, the approach may not be compatible with materials used for biomedical applications such as drug delivery. Robert S. Langer, Ana Jaklenec, and coworkers at Massachusetts Institute of Technology have developed an alternative method for making microdevices from biomedically relevant materials, such as poly(lactic-co-glycolic acid) (Science 2017, DOI: 10.1126/science.aaf7447). The researchers use polydimethylsiloxane molds to shape individual layers of multilayer polymeric devices. They then align, assemble, and bond the layers using heat. The MIT team used the method to make fillable polymer microparticles that release their contents according to a preprogrammed schedule on the basis of polymer composition. They built particle bases, filled them with drug solution, capped the bases with polymer lids, sealed them by heating, and then scraped the microparticles off the substrate. In a test application, the researchers made single-injection vaccines by placing antigen doses in microparticles that release the contents at desired intervals. They gave mice a single injection of a mixture of microparticles that released ovalbumin, a model antigen, nine and 41 days after injection. Those mice achieved antibody levels higher than those in mice given separate ovalbumin injections at days six and 36. In addition to drug delivery applications, the MIT researchers used the fabrication method to make a pH sensor and microfluidic devices.