Thiolation of non-ionic surfactants for the development of lipid-based mucoadhesive drug delivery systems

The aim of this study was to develop thiolated self-emulsifying drug delivery systems (SEDDS) and nanostructured lipid carriers (NLCs) with improved mucoadhesive properties. Two non-ionic surfactants bearing a short and long PEG chain, namely polyoxyethylene (10) stearyl ether (PSE₁₀) and polyoxyethylene (100) stearyl ether (PSE₁₀₀), were thiolated for the first time by substituting the terminal hydroxyl group with a thiol group. The synthesis was confirmed by FT-IR, NMR and Ellman's test. SEDDS and NLCs containing these thiolated compounds were investigated for size, polydispersity index (PDI) and ζ potential. Subsequently, mucus diffusion studies, rheological evaluations after mixing the nanocarriers with mucus and mucoadhesion studies on porcine intestinal mucosa were performed. All nanocarriers had a size less than 250 nm, a maximum PDI of 0.3 and a ζ potential < -9.0 mV. Mucus diffusion studies resulted in the rank order of increasing diffusivity: PSE₁₀-SH < PSE₁₀₀-SH < PSE₁₀-OH < PSE₁₀₀-OH for NLCs and PSE₁₀-OH < PSE₁₀₀-OH < PSE₁₀₀-SH < PSE₁₀-SH for SEDDS. The mucoadhesive properties and increase in viscosity of SEDDS and NLCs ranked: PSE₁₀₀-OH < PSE₁₀-OH < PSE₁₀₀-SH < PSE₁₀-SH. In addition, the short chain PSE₁₀-SH showed higher mucus interactions than the long chain PSE₁₀₀-SH for both SEDDS and NLCs. The thiolated PSE surfactants appeared to be promising excipients for the design of highly mucoadhesive drug delivery systems.

Influence of the surface properties of nanocapsules on their interaction with intestinal barriers

Despite the convenience of the oral route for drug administration, the existence of different physiological barriers associated with the intestinal tract greatly lowers the bioavailability of many active compounds. We have previously suggested the potential polymeric nanocapsules, consisting of an oily core surrounded by a polymer shell, as oral drug delivery carriers. Here we present a systematic study of the influence of the surface properties of these nanocapsules on their interaction with the intestinal barriers. Two different surfactants, Pluronic®F68 (PF68) and F127 (PF127), and two polymeric shells, chitosan (CS) and polyarginine (PARG) were chosen for the formulation of the nanocapsules. We analyzed nine different combinations of these polymers and surfactants, and studied the effect of each specific combination on their colloidal stability, enzymatic degradation, and mucoadhesion/mucodiffusion. Our results indicate that both, the polymer shell and the surfactants located at the oil/water interface, influence the interaction of the nanocapsules with the intestinal barriers. More interestingly, according to our observations, the shell components of the nanosystems may have either synergic or disruptive effects on their capacity to overcome the intestinal barriers.

Nanoparticle passage through porcine jejunal mucus: Microfluidics and rheology

A micro-slide chamber was used to screen and rank sixteen functionalized fluorescent silica nanoparticles (SiNP) of different sizes (10, 50, 100 and 200 nm) and surface coatings (aminated, carboxylated, methyl-PEG₁₀₀₀ylated, and methyl-PEG₂₀₀₀ylated) according to their capacity to permeate porcine jejunal mucus. Variables investigated were influence of particle size, surface charge and methyl-PEGylation. The anionic SiNP showed higher transport through mucus whereas the cationic SiNP exhibited higher binding with lower transport. A size-dependence in transport was identified - 10 and 50 nm anionic (uncoated or methyl-PEGylated) SiNP showed higher transport compared to the larger 100 and 200 nm SiNP. The cationic SiNP of all sizes interacted with the mucus, making it more viscous and less capable of swelling. In contrast, the anionic SiNP (uncoated or methyl-PEGylated) caused minimal changes in the viscoelasticity of mucus. The data provide insights into mucus-NP interactions and suggest a rationale for designing oral nanomedicines with improved mucopermeability.