2 research outputs found
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
Mussel-Inspired Adhesive and Tough Hydrogel Based on Nanoclay Confined Dopamine Polymerization
Adhesive
hydrogels are attractive biomaterials for various applications,
such as electronic skin, wound dressing, and wearable devices. However,
fabricating a hydrogel with both adequate adhesiveness and excellent
mechanical properties remains a challenge. Inspired by the adhesion
mechanism of mussels, we used a two-step process to develop an adhesive
and tough polydopamine-clay-polyacrylamide (PDA-clay-PAM) hydrogel.
Dopamine was intercalated into clay nanosheets and limitedly oxidized
between the layers, resulting in PDA-intercalated clay nanosheets
containing free catechol groups. Acrylamide monomers were then added
and <i>in situ</i> polymerized to form the hydrogel. Unlike
previous single-use adhesive hydrogels, our hydrogel showed repeatable
and durable adhesiveness. It adhered directly on human skin without
causing an inflammatory response and was easily removed without causing
damage. The adhesiveness of this hydrogel was attributed to the presence
of enough free catechol groups in the hydrogel, which were created
by controlling the oxidation process of the PDA in the confined nanolayers
of clay. This mimicked the adhesion mechanism of the mussels, which
maintain a high concentration of catechol groups in the confined nanospace
of their byssal plaque. The hydrogel also displayed superior toughness,
which resulted from nanoreinforcement by clay and PDA-induced cooperative
interactions with the hydrogel networks. Moreover, the hydrogel favored
cell attachment and proliferation, owning to the high cell affinity
of PDA. Rat full-thickness skin defect experiments demonstrated that
the hydrogel was an excellent dressing. This free-standing, adhesive,
tough, and biocompatible hydrogel may be more convenient for surgical
applications than adhesives that involve <i>in situ</i> gelation
and extra agents