Figure 1: Schematic illustration of RGD-grafted polyelectrolyte multilayer (PEM) and biomimetic self-assembly ECM nanostructures on Ti surfaces.

(a) Synthesis of RGD -grafted oxidized alginate (RGD-OAlg); (b) RGD-grafted PEM preparation by self-assembling of chitosan (Chi) and RGD-OAlg for 20 bilayers; (c) BMP-2 loaded Chi coated BSA nanoparticles (BMP-CBNP) were prepared by a modified desolvation method. Firstly, the mixed BSA/BMP aqueous solution was desolvated by dropwisely adding ethanol to form BMP-loaded BSA nanoparticles (BMP-BNP). Subsequently, the BMP-BNP were coated with a Chi layer to form positive charged BMP-CBNP; (d) The incorporation of CBNP into PEM to form biomimetic ECM coatings. The ECM coatings were fabricated by sequentially assembling Chi (positively charged), RGD-OAlg (negatively charged), CBNP (positively charged), and RGD-OAlg (negatively charged) on the pretreated Ti to form Chi/RGD-OAlg/CBNP/RGD-OAlg architecture, and this cycle was repeated to achieve 10-tetralayer films to form ECM nanostructures; (e) The reaction mechanism between RGD-OAlg and Chi or CBNP. Free amino groups of Chi and the aldehyde groups of RGD-OAlg react with each other to form covalent bonds through Schiff-base reaction.