Aminoglycoside/Hexadecanoic Acid Complex Lamellar Core Nanoparticles.

An aminoglycoside, tobramycin sulfate (TbS), was complexed with hexadecanoic acid (HdA), resulting in a TbS/HdA complex with a repeat unit of 5.3 nm of a lamellar nanostructure. The nanometer-sized TbS/HdA particles were produced using poloxamer 188 as a dispersing agent. The particles were agglomerate-free with sizes in the range of 90-450 nm. The particle size was controlled by optimizing the homogenization conditions and the concentration of poloxamer-188. The lamellar nanostructure of the TbS/HdA complex was retained in the nanoparticle cores, even after the rigorous homogenization step. These core-shell-type nanoparticles were called lamellosomes because each particle consisted of a TbS/HdA lamellar core surrounded by a crown of hydrophilic poloxamer. The ζ-potentials of nanoparticles were in the range of -20 to -26 mV and did not aggregate even after exposing them up to the concentrations of 0.2 mol  L NaCl. However, the nanoparticles were sensitive to the changes in the pH in terms of their aggregation or disintegration. Thus, the steric effects and ionic charge seem to be responsible for the stabilization of the nanoparticles. The TbS/HdA matrix or HdA lamella could dissolve dexamethasone up to ∼2% (w/w) without causing crystallization. The release of the entrapped drug was significantly retarded. The TbS/HdA lamellosomes could serve as aminoglycoside carriers, which can further load drugs, showing potential as a multidrug cargo.