Banca de QUALIFICAÇÃO: 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 films of poly(vinyl)alcohol (PVA) and sodium carboxymethylcellulose (NaCMC) containing pyriproxyfen with a controlled release profile against immature forms of Haematobia irritans in cattle. The films were obtained with PVA crosslinked with NaCMC, using the solvent casting method with the incorporation of pyriproxyfen. They were subjected to 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 858.8% with an absorption capacity of 0.2613g/cm². 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. PVA/NaCMC/pyriproxyfen films had potential properties for cattle treatment, being able to remain intact in the rumen medium to provide sustained release.