Progesterone-loaded solid lipid nanoparticles for use in the regulation of the estrous cycle in female rats

Protocols used for artificial insemination involve the effective synchronization of the estrous cycle by the administration of exogenous hormones including progesterone analogs. Although widespread in the world, the current techniques present many disadvantages that need to be overcome such as the time dependency of progesterone levels in the blood and the need to remove the release dispositive. Nanotechnology may offer the tools for it, and solid lipid nanoparticles (SLN) are a promising candidate to be used as nanocarriers for progesterone. In this work, progesterone-loaded SLNs were investigated in the regulation of the estrous cycle in female rats. First, the obtention of the SLN was investigated to determine how experimental parameters may affect the encapsulation efficiency of progesterone and the morphology of the nanoparticles. Also, in vitro release profiles of progesterone were also evaluated. Sexual receptivity, mutagenicity, hepatic inflammation and steatosis, hormone measurement, and biometric parameters of pups were also determined. Progesterone-loaded SLN induced estrous cycle synchronization and were able to maintain the estrous phase of the estrous cycle while inducing a greater latency release for its onset. Progesterone induced an increase in the sexual receptivity of the females and did not alter the biometric parameters like the body weight of the mothers and puppies, until weaning. Results gathered here demonstrated that encapsulation of progesterone may be a promising alternative to the conventional methods for synchronization of the estrous cycle of female animals in artificial insemination procedures.