Interrupting the blood-testis barrier with a flutamide-loaded nanostructured lipid carrier: A novel nonsurgical contraceptive approach for male animals.

Flutamide is an antagonist of testosterone, an essential hormone in male reproduction. However, the use of flutamide as a contraceptive agent for nonsurgical castration in veterinary practice remains challenging due to its poor bioavailability. Here, the flutamide-loaded nanostructure lipid carrier (FLT-NLC) was synthesized, and its biological effects were demonstrated by an in vitro blood-testis barrier model. The flutamide was incorporated into the nanostructure lipid carrier by a homogenization method resulting in a high encapsulation efficiency (99.7 ± 0.04%). The FLT-NLC was negatively charged (-27.90 ± 0.10 mV), with a nano size (182.13 ± 0.47 nm) and narrow dispersity index (0.17 ± 0.01). An in vitro release study demonstrated a slower release profile of FLT-NLC when compared with flutamide solution (FLT). The FLT-NLC at doses up to 50 μM showed no significant cytotoxic effects against mouse Sertoli cells (TM4) or mouse fibroblast cells (NIH/3T3) (p > 0.05). An in vitro blood-testis barrier with FLT-NLC demonstrated remarkable lower transepithelial electrical resistance when compared with those lacking FLT-NLC (p < 0.01). Moreover, FLT-NLC significantly decreased the mRNA expression of blood-testis barrier proteins, CLDN11 and OCLN. In conclusion, we successfully synthesized FLT-NLC and confirmed its potential antifertility effects on in vitro blood-testis barrier, thus indicating its possible application as nonsurgical contraception for male animals.