In vitro protoscolicidal effects of high-intensity focused ultrasound enhanced by a superabsorbent polymer

Echinococcus granulosus, the etiologic agent of cystic echinococcosis in humans and other animal hosts, is distributed worldwide. Echinococcosis is an increasing public health and socioeconomic concern. The present work evaluated whether or not a superabsorbent polymer (SAP) could enhance the damage efficacy of high-intensity focused ultrasound (HIFU) on the viability of E. granulosus protoscolices in vitro. HIFU of 100 W acoustic power and 0.01 g superabsorbent polymer were used to treat 5,000 protoscolices in 2-ml protoscolices suspension. After different HIFU exposure time (5, 10, 20, 30, 40, 50, and 60 s, respectively), the temperature of protoscolices suspension was taken, and the treated protoscolices were stained by trypan-blue exclusion assay, and their structures were observed by light microscopy. To better understand the biological mechanisms responsible for the deaths of protoscolices, the activity of succinate dehydrogenase (SDH) of the protoscolices treated with HIFU was examined. The temperature of protoscolices suspension treated with HIFU rose slowly, and the death rate of protoscolices was 73.7 % in the group of HIFU treatment time of 40 s; however, with the same HIFU treatment time of 40 s, the temperature of protoscolices suspension in the group of HIFU combined with SAP rose quickly, and the death rate of protoscolices was 100 %. The same protoscolicidal effect (100 %) of HIFU of 100 W acoustic power combined with SAP was also observed in the groups of HIFU treatment time of 50 and 60 s, respectively. The dead protoscolices were stained to blue, shrunken and black calcareous corpuscles, and disordered and decreasing hooks though of intact membrane, as well as some protoscolices lost hooks and tore open on membrane were observed. In the group of HIFU combined with SAP, it was found that the superabsorbent polymer was surrounded by the spoiled, and the destruction of protoscolices was much stronger than in the group of HIFU. The dead protoscolices exhibited the reduction or absence of SDH staining intensity in the parenchymal cell and calcareous corpuscles after HIFU irradiation, where a large number of necrotic cells were evident. These results suggested that HIFU could induce the damage and loss of viability of protoscolices; SAP could enhance the HIFU energy focused and cause more severe destruction efficacy on protoscolices; and mitochondrial energetic function is involved in the regulation of cell-death pathways of protoscolices.