Uso de ciclodextrina na formação de complexos de inclusão com o hormônio masculinizante 17-α-metiltestosterona

Abstract

17α-methyltestosterone (MT) is the most widely used synthetic androgen for sex reversal in tilapia. Due to its physicochemical properties, the cyclodextrin (CD) used to form inclusion complexes with methyltestosterone is a new possibility of sex reversal method. In this study, inclusion complexes between β-CD and MT were prepared by lyophilization, kneading and physical mixture. The product was characterized by spectroscopic methods, thermal analysis and microscopy. The behavior of the hormone in the presence of cyclodextrin was evaluated for change in polarity of the solvation environment. Evaluation of solubility and estimated stoichiometry of the inclusion complex were performed by phase techniques. Differential scanning calorimetry and scanning electron microscopy were used to assess the formation of complexes in the solid state. The interactions between guest and host were evaluated by 1H NMR and DOSY measurements. 2D ROESY experiments were used to establish the structure of the complex, and how the interaction occurs, confirming the results of molecular dynamics for the formation of the inclusion complex in vacuum. The formation of the inclusion complex provided a 6-fold increase in the solubility of the hormone, the formation of a complex with limited solubility and a 1:2 stoichiometry (MT:CD). The suppression of endothermic hormone peaks and water solvation of cyclodextrins, as well as the change in morphology of the products obtained confirm the formation of inclusion complexes. The chemical shifts of H3 and H5 in cyclodextrin point out to a complete inclusion of the hormone in the cavity. The association constant Ka=2.846 mol L-1and the complexed fraction of 76%was determined with the DOSY. Release tests showed a slower release for the complexes prepared by lyophilization, with 65% for the 1:1 molar ratio complex, and 50% for the 1:2 molar ratio complex. The in vivo experiments seem to indicate that the formulations of the complexes are a viable method to be used commercially; however, the results are still preliminary and require further studies. Thus, the use of nanotechnology, represented by the association of methyltestosterone with β-cyclodextrin, has strong potential to be used in aquaculture for sex reversal of tilapia.