Pulse Electrochemical Driven Rapid Layer-by-Layer
Assembly of Polydopamine and Hydroxyapatite Nanofilms via Alternative
Redox <i>in Situ</i> Synthesis for Bone Regeneration
Polydopamine (PDA) is an important
candidate material for the surface
modification of biomedical devices because of its good adhesiveness
and biocompatibility. However, PDA nanofilms lack osteoinductivity,
limiting their applications in bone tissue engineering. Hydroxyapatite
nanoparticles (HA-NPs) are the major component of natural bone, which
can be used to effectively enhance the osteoinductivity of PDA nanofilms.
Herein, we developed a pulse electrochemical driven layer-by-layer
(PED-LbL) assembly process to rapidly deposit HA-NPs and PDA (HA-PDA)
multilayer nanofilms. In this process, PDA and HA-NPs are <i>in situ</i> synthesized in two sequential oxidative and reductive
pulses in each electrochemical deposition cycle and alternately deposited
on the substrate surfaces. PDA assists the <i>in situ</i> synthesis of HA-NPs by working as a template, which avoids the noncontrollable
HA nucleation and aggregation. The HA-PDA multilayer nanofilms serve
as a tunable reservoir to deliver bone morphogenetic protein-2 and
exhibit high osteoinductivity both <i>in vitro</i> and <i>in vivo</i>. This PED-LbL assembly process breaks the limitation
of traditional LbL assembly, allowing not only the rapid assembly
of oppositely charged polyelectrolytes but also the <i>in situ</i> synthesis of organic/inorganic NPs that are uniformly incorporated
in the nanofilm. It has broad applications in the preparation of versatile
surface coatings on various biomedical devices
