S‐layer Coated Emulsomes as Potential Nanocarriers

Abstract The present study introduces a novel nanocarrier system comprising lipidic emulsomes and S‐layer (fusion) proteins as functionalizing tools coating the surface. Emulsomes composed of a solid tripalmitin core and a phospholipid shell are created reproducibly with an average diameter of approximately 300 nm using temperature‐controlled extrusion steps. Both wildtype (wt) and recombinant (r) S‐layer protein SbsB of Geobacillus stearothermophilus PV72/p2 are capable of forming coherent crystalline envelope structures with oblique (p1) lattice symmetry, as evidenced by transmission electron microscopy. Upon coating with wtSbsB, positive charge of emulsomes shifts to a highly negative zeta potential, whereas those coated with rSbsB become charge neutral. This observation is attributed to the presence of a negatively charged glycan, the secondary cell wall polymer (SCWP), which is associated only with wtSbsB. The present study shows for the first time the ability of recombinant and wildtype S‐layer proteins to cover the entire surface of emulsomes with its characteristic crystalline lattice. Furthermore, in vitro cell culture studies reveal that S‐layer coated emulsomes can be uptaken by human liver carcinoma cells (HepG2) without showing any significant cytotoxicity over a wide range of concentrations. The utilization of S‐layer fusion proteins equipped in a nanopatterned fashion by identical or diverse functions may lead to further development of emulsomes in nanomedicine, especially for drug delivery and targeting.