To explore the mechanism and behavior of polyelectrolyte multilayer films (PEM)of gene-loaded lipopolysaccharide-amine nanopolymersomes/hyaluronic acid self assembled on titanium or quartz surface.

Via layer-by-layer self assembly technology, PEM were constructed on titanium or quartz surface by using bone morphogenetic protein-2(BMP-2)plasmid-loaded lipopolysaccharide-amine nanopolymersomes(pNPs)as a polycation, and hyaluronic acid(HA)as a polyanion. The constructed PEM was defined as substrate-pNPs-(HA/pNPs)_n, where a successive deposition of HA and pNPs on substrate surface was defined as one assembly cycle, and n was the cycle number. The changes in topography and roughness of films during assembly were observed by atomic force microscope(AFM). The surface zeta potential was determined by a zeta potential and nanoparticle size analyzer. The assembly procedure was monitored in real time by a quartz crystal microbalance with dissipation(QCM-D), and their assembly patterns were explored.

AFM results showed that pNPs discretely and uniformly adhere to the substrate surface at first, and then with self assembly, a dense and strong tree-like three-dimensional nanostructure is gradually formed, followed by the progressive increase in their surface roughness. The zeta potential of films increases in a zigzag pattern with self assembly. For quartz surface, it is -4.83 mV, and after pNPs deposition, it increases to positive. For films with outmost layer of pNPs, after 3 assembly cycles, it was stabilized at 18 mV. For films with outmost layer of HA, their zeta potential gradually changes from negative to positive with assembly. The QCM-D results showed that with self assembly, the film mass and thickness increase in an exponential type.

Gene-loaded lipopolysaccharide-amine nanopolymersomes/hyaluronic acid can construct polyelectrolyte multilayer films with distinctive three-dimensional nanostructure via layer-by-layer self assembly, their growth mode is exponential, and the films have nano-scale roughness with non-dense texture.