Solid lipid nanoparticles (SLN) are regarded as interesting carriers to improve sunscreens’ safety and
effectiveness. In this work, surfactant effects on the physico-chemical properties of SLN loading two of
the most widely used UV-filters, octylmethoxycinnamate (OMC) and butylmethoxydibenzoylmethane
(BMBM), were evaluated and the interactions between SLN components and loaded UV-filters were
investigated by differential scanning calorimetry (DSC). All the SLN showed a mean size ranging from
30 to 95 nm, and a single peak in size distribution. The use of isoceth-20 or oleth-20 as primary surfactants
did not provide SLN with suitable physico-chemical properties since: (a) OMC loaded SLN proved
unstable; (b) BMBM could not be loaded. OMC or BMBM loaded SLN prepared using ceteth-20 as primary
surfactant were stable but their loading capacity lowered when both sunscreens were loaded simultaneously.
DSC analyses showed that OMC distributed inside the SLN and caused a decrease of the lipid
matrix molecules cooperativity while BMBM did not affect SLN calorimetric behaviour. When OMC and
BMBM were loaded together into these SLN, an interaction between BMBM and OMC occurred. These
results suggest that the interactions between sunscreens and between sunscreens and SLN components
deserve further investigation to evaluate their effect on UV-filter-loaded SLN effectiveness