In vitro and in vivo assessment of sporopollenin exine capsule preparations (SpECs) from Lycopodium clavatum spores

Abstract

This study investigated the potential allergenicity of sporopollenin exine capsule preparations (SpECs) derived from plant pollen or spores as allergenicity could limit their use as a therapeutic oral drug delivery system. As allergenicity may differ depending on the method of preparation, raw spores from Lycopodium clavatum, together with 6 L. clavatum SpEC preparations were evaluated in vitro by adenosine triphosphate (ATP) bioassay for cell viability. Subsequently, in vivo evaluations were performed in 6–8 week male Balb/C mice gavaged daily with raw L. clavatum spores, a negative control (PBS), or one of SpEC-3, 4 or 5 preparations for five consecutive days; gastrointestinal tissues were collected 6 hours following the final gavage. In vitro cytotoxicity studies showed that, compared to the cell control, L. clavatum spores and SpEC-2 and SpEC-4 preparations showed significantly decreased cell viability, while no significant differences in cell viability were found for SpEC-1, 3, 5 or 6 preparations, all of which were extracted more intensively than SpEC-2 or SpEC-4 preparations. In vivo safety studies showed no increase in CD68-positive macrophage cell infiltration in any region of the gastrointestinal tract (stomach, duodenum, jejunum, ileum or colon), liver or kidneys. No exines were found in any tissue. We concluded that, whilst differing SpEC manufacturing processes may have residual in vitro cytotoxicity, this did not translate to an acute in vivo oral gastrointestinal immune response, suggesting their safety as a vehicle for gastrointestinal pharmaceutical delivery.