PDA/CPP bilayer prepared via two-step immersion for accelerating the formation of a crack-free biomimetic hydroxyapatite coating on titanium substrates.

Polydopamine (PDA)/casein phosphopeptide (CPP) bilayers were prepared on titanium (Ti) substrates through a simple two-step immersion process at room temperature. The adhering PDA interlayers linked the natural biomolecule, CPP, to the Ti surface via covalent bonds. The outer layer of CPP served as a template to bind Ca 2+ and thus promoted nucleation and growth of hydroxyapatite (HA). Our results indicate that: (i) PDA and CPP can be successfully grafted onto Ti substrates; (ii) an HA coating can be formed within 1 day through the biomimetic HA coating method on the Ti substrate modified with PDA/CPP bilayer; and (iii) no cracking is observed in the HA coating, indicating stable binding between HA and the modified substrate. [ABSTRACT FROM AUTHOR]