Banca de DEFESA: MELINA CARDILO CAMPOS ALVES

Development and characterization of a controlled release system containing pyriproxyfen to control immature 

forms of Haematobia irritans in cattle.

Polymeric films, intra-ruminal release, horn fly.

Haematobia irritans is considered a major livestock pest in Brazil and causes economic losses to the livestock industry globally. New control strategies are based on safer compounds, such as the class of insect growth regulators (IGRs), analogous to juvenile hormones that inhibit insect development. The oral efficacy of pyriproxyfen allows the development of formulations that guarantee the safety and extension of the pharmacological action. This study aimed to develop a pyriproxyfen-based Rumino-Reticulum Device (RRD) consisting of films of poly(vinyl)alcohol (PVA) and sodium carboxymethylcellulose (NaCMC) to control the horn fly in cattle. Films were obtained by the solvent casting method by PVA/NaCMC crosslinking. The assays was include physical-chemical characterization, weight variation and pH measurement, swelling degree test (SD), drug content determination, in vitro drug release test, X rays diffraction analysis (XRD), fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). Films were subjected individually to weight variation measurement (n=3), with an average value of 0.446 ± 0.02 mg and presented basic pH values (6.5 ± 0.09), near the ruminal pH (6.5-7.5). The SD predicted by the absorption capacity of the film in the time interval obtained was 331,40% with an absorption capacity. HPLC determined the drug content of films, and the value obtained was 104.81%. The in vitro release results supported a slow-release profile, indicating pseudo-first-order kinetics. FTIR analysis elucidated the characteristic bands of PVA, NaCMC, and pyriproxyfen, and demonstrated the absence of the drug after release. SEM images showed changes in the porosity distribution of the samples after the addition of pyriproxyfen, and XRD analysis showed an increase in crystallinity due to the presence of pyriproxyfen (Xc of 36.59%). Thermal analysis revealed that pyriproxyfen and its delivery altered chain packing, with Tg values of 74 ºC and Tm of 208 °C. The pyriproxyfen-based RRD developed, in addition to fulfilling the characteristics of prolonged release, allows it to be rolled up (compressed form) facilitating swallowing and subsequent conversion to an expanded form that is retained in the rumen throughout the treatment period.