Diverse deformation properties of polymeric nanocapsules and lipid-core nanocapsules

The deformation properties of submicrometric drug carriers can influence their tissue-penetration ability and thus the drug targeting. The aim of this study was to determine whether the oily core composition (raw oils or a dispersion of oils and solid lipid) surrounded by a polymeric wall [poly(epsilon-caprolactone), (PCL)] can affect the deformation properties of nanocapsules (NCs) or lipid-core nanocapsules (LNCs). Formulations were prepared as aqueous suspensions using a polymer and either a mixture of caprylic/capric triglyceride (CCT) and octyl methoxycinnamate (OMC) or a mixture of CCT, OMC and sorbitan monostearate (SM) as core components, respectively. Formulations had mean diameters close to 200 nm presenting monomodal distributions. A polysorbate 80 coating rendered z-potential values close to zero, acting as a steric stabilizer. Atomic force microscopy (AFM) showed, through force curves analysis, that the cantilever deflection was more pronounced for the LNCs than for the NCs. The same force applied to NC produced an indentation around twice that observed for the LNCs. The Young's modulus (E) values were 0.537 MPa (LNC) and 0.364 MPa (NC) considering conical geometry while E = 0.17 MPa (NC) and E = 0.241 (LNC) for spherical geometry. These data confirm that the LNCs are stiffer than the NCs. The rigidity of both the polymer wall and lipid core is higher for LNCs. In conclusion, LNCs presented distinct mechanical properties compared to the conventional polymeric NCs.