Injectable microparticle-gel system for prolonged and localized lidocaine release. I. In vitro characterization

Current treatment protocol for postoperative pain is to infuse anesthetic solution around nerves or into the epidural space. This clinical practice is beset by the short duration of the anesthetic effect unless the infusion is continuous. Continuous infusion, however, requires hospitalization of the patients, thereby increasing medical costs. In addition, it also causes systemic accumulation of the drug. We reported herein a novel treatment for the postoperative pain by applying to the surgical site a biodegradable microsphere-gel system for prolonged and localized release of encapsulated anesthetic drugs. This lidocaine-containing biodegradable poly( D , L -lactic acid) (PLA) microsphere system, although being established previously by other investigators, was hindered by a burst release and a followed rapid release of the drug within several hours in vitro . In this article, we demonstrated that by a step-by-step modification of the formulation, prolonged release of lidocaine, up to several days in vitro , could be achieved. Differential scanning calorimetry revealed a lower glass transition temperature for these lidocaine-loaded microspheres comparing to that of lidocaine-free microspheres. This decreased T g explained for the tendency of the lidocaine-loaded microspheres to physically fuse at higher temperatures. In vitro studies showed that microspheres, when loaded with 35% lidocaine, yielded a threefold increase in the degradation rate. The molecular weight of PLA of the drug-loaded microspheres was reduced by 50% within a period of 1 month. Based on the results (of prolonged lidocaine release and rapid PLA microsphere degradation), this lidocaine-loaded PLA microsphere system could offer a simple solution to the treatment of postoperative pain. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 412–419, 2004Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34434/1/30086_ftp.pd

Historical land use change has lowered terrestrial silica mobilization

Continental export of Si to the coastal zone is closely linked to the ocean carbon sink and to the dynamics of phytoplankton blooms in coastal ecosystems. Presently, however, the impact of human cultivation of the landscape on terrestrial Si fluxes remains unquantified and is not incorporated in models for terrestrial Si mobilization. In this paper, we show that land use is the most important controlling factor of Si mobilization in temperate European watersheds, with sustained cultivation (>250 years) of formerly forested areas leading to a twofold to threefold decrease in baseflow delivery of Si. This is a breakthrough in our understanding of the biogeochemical Si cycle: it shows that human cultivation of the landscape should be recognized as an important controlling factor of terrestrial Si fluxes.SCOPUS: ar.jinfo:eu-repo/semantics/publishe