Size-variable mesoporous micro-biobeads for controlled hormone delivery in programmed animal reproduction

IGNACIO RINTOUL; JUAN MANUEL BADANO; RICARDO GRAU; MARIO WEIBEL

Montpellier

Congreso; EUROMAT 2011. European Congress and Exhibition on Advanced Materials and Processes; 2011

Federation of European Materials Societies, Associazione Italiana di Metallurgia, Société Francaise de Métallurgie et de Matériaux

Selected for oral presentation The control of the estrous cycle and ovulation in bovine breeders significantly improves the livestock cattle business. Controlled hormones release through loaded polymer matrices may control the estrous cycle   and   artificially   induces   ovulation.   Hormones   release from biocompatible, biodegradable and injectable  microbeads  is  an interesting  alternative  to  the existing intravaginal devices. Some advantages of this technology are the possibility to perform massive artificial insemination at very low product and labor costs, to improve the cattle genetics in a fast and economic way and to optimize the delivery periods and the feeding and vaccination programs. In addition, storage, transportation, application and dosage of microbeads are easier than using intravaginal devices. Moreover, aseptic conditions and the actions for introduction, retire and final deposition of intravaginal devices can be avoided.Polyvinyl   alcohol,   dropping/gelling   technique   and   progesterone   were   selected   as   polymer   matrix, microencapsulation technology and case hormone, respectively. The effects of chemical composition and   dropping/gelling   conditions   on   the   geometry   and   size   distribution   of   microbeads   and   the dissolution ­ diffusion processes of progesterone through the matrix were studied. A procedure for microbeads production that maximizes the spherical shape, minimizes the polydispersity of results and regulates   the   pore   size   for   hormone   release   was   developed.   Statistical   methods   were   applied   for experimental  design. The  dissolution  of progesterone  crystals   and  subsequent  diffusion  though   the polymer matrix was regulated by reversible and irreversible crosslinking at the bulk and surface of the microbeads.   The kinetics  of progesterone release  could be  controlled reaching  zero order   patterns. Those polymeric crosslinking strategies allowed to produce microbeads loaded at 5, 20, 33 and 50 wt% of progesterone. The swelling and the dissolution of the polymer matrix could be varied between 50 to 90% and  from 2 hours to 15 days, respectively. Microbeads  loaded at 5wt% released progesterone (47mg/L h) at almost double rate than microbeads loaded at 50wt% (20 mg/L h). In­vitro and in­vivo results for hormone release are presented.