Preparation and functionalization of hollow nanoparticles fabricated by the layer-by-layer deposition

To prepare hollow particles in a nano size, we used a layer-by-layer deposition. Liposomes were used as a template for this deposition. At first, negatively charged liposomes composed of dilauroyl phosphatidic acid (DLPA) and dimyristoyl phosphatidylcholine (DMPC) were prepared with the extrusion method. Then, polyelectrolytes were adsorbed on the liposomal template. Poly-L-lysine (P_Lys) and poly-L-aspartic acid (P_Asp) were chosen as adsorbates to make a capsule of the biopolymers. When the alternative adsorption of P_Lys and P_Asp on the liposomes was repeated for thickening the capsule layer, their ζ-potentials changed between positive and negative charges at each deposition. To investigate the release behavior from the liposomes and the liposome-polypeptide complexes, we prepared liposomes incorporating 1-hydroxypyrene-3,6,8-trisulfonic acid (HPTS). It was found that the release experiment to the buffered solutions was related to the adsorption of polymers. When the liposomes were completely covered with P_Lys, the release was suppressed.