Enhanced storage stability of solid lipid nanoparticles by surface modification of comb-shaped amphiphilic inulin derivatives.

Solid lipid nanoparticles (SLNs) have been widely used as a vehicle for drug delivery. However, highly ordered lipid lattices and poor storage stability limit their practical application. Highly ordered crystal lattices may result from the low drug payload. In addition, the lipid matrix of SLNs may undergo a polymorphic transition from high energy and disordered modifications to low energy and ordered modifications during storage. This leads to drug expulsion and precipitation. Meanwhile, SLNs are susceptible to particle aggregation and size growth during storage. To improve the performance of SLNs, two comb-shaped amphiphilic macromolecular materials (CAMs), dodecyl inulin (Inu12) and octadecyl inulin (Inu18), were synthesized and utilized as emulsifiers to modify and stabilize SLNs (Inu12/Inu18-SLNs). The results indicated that Inu12 and Inu18 could more effectively reduce the lipid crystallinity and crystal lattice order of fresh SLNs versus Poloxamer 188 and Tween-80. Moreover, after six months of storage at 4 °C or 25 °C, both blank and Cyclosporine A (CsA)-loaded Inu12/Inu18-SLNs had a slower crystal transition than Tween/P188-SLNs. The particle size increases of Inu12/Inu18-SLNs were much smaller than those of Tween/P188-SLNs. The drug encapsulation efficiencies of CsA-loaded Inu12/Inu18-SLNs during storage decreased more slowly than Tween-SLNs. Therefore, Inu12 and Inu18 could more effectively inhibit lipid crystal transition and prevent particle aggregation during storage. This, in turn, leads to better storage physical stability of SLNs. Thus, the Inu12 and Inu18 CAMs were superior to Tween-80 and Poloxamer 188 (common straight-chain surfactants).