Structural characterization and in-vivo histocompatibiliy trials of controlled hormone release microcapsules for the control of oestrous cycle in cattle

MARIO WEIBEL; MATIAS LAPISSONDE; JUAN PABLO VECICONTI; IGNACIO RINTOUL

Puerto Iguazu

Congreso; 13º Congreso Internacional en Ciencia y Tecnologia de Metalurgia y Materiales; 2013

Universidad Nacional de Misiones y Asociacion Argentina de Materiales

<!-- @page { margin: 2cm } P { margin-bottom: 0cm; direction: ltr; color: #000000; line-height: 200%; text-align: justify; widows: 2; orphans: 2 } P.western { font-family: "Times New Roman", serif; font-size: 12pt; so-language: en-US } P.cjk { font-family: "Times New Roman", serif; font-size: 12pt; so-language: zh-CN } P.ctl { font-family: "Times New Roman", serif; font-size: 12pt; so-language: ar-SA } A:link { so-language: zThe control of the oestrous cycle and ovulation in bovine breeders significantly improves the livestock cattle business. Controlled hormones release through loaded biopolymeric matrices may control the oestrous 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 labour costs and to optimize the delivery periods and the feeding and vaccination programs of calves. In this contribution, a dropping/gelling solvent free technique to produce hydrogel microcapsules of polyvinyl alcohol loaded with progesterone and 1 mm of diameter is described. Three different crosslinking strategies to obtain the hydrogel structure were used. The progesterone final content and the encapsulation process efficiency (EE) were measured by UV spectrophotometry. In addition, the obtained microcapsules were characterized by DSC, IR, optical microscopy and SEM. Finally, the histocompatibility of the microcapsules were evaluated by in-vivo tests performed in Brangus beef cows. Capsules were found to be roughly spherical and with a narrow size distribution. The analysis of DSC and IR spectra shows that progesterone did not undergo any chemical change but suffered of a physical change in its crystalline structure during the encapsulation process. The EE increased with increasing content of progesterone in the primary dropping suspension reaching 90%. For each type of hydrogel microcapsules, three doses were implanted in the back of a cow. Biopsies were extracted at 4, 8 and 75 days post implantation. The combinations of crosslinkinng strategies permitted to control the bioassimilation time while keeping histocompatibiliy and healing rates. No autoimmune reactions were observed.