Polyvinylidene fluoride (PVDF), as a typical piezoelectric polymer, has a great potential in reconstructing the electrical microenvironment of bone tissue. In present study, graphene oxide (GO) was introduced into PVDF scaffold manufactured via selective laser sintering, aiming to enhance piezoelectric effect of PVDF by increasing β phase content. In detail, the oxygen-containing functional groups of GO could form strong hydrogen bonding with fluorine groups of PVDF. The interaction would force the fluorine groups to be arranged in parallel and perpendicular to the polymer chain, thereby inducing the transformation from α phase to β phase. Results demonstrated that the PVDF/0.3GO scaffold with improved β phase exhibited the maximal output voltage (~8.2 V) and current (~101.6 nA), which were improved by 82.2% and 68.2%, respectively, in comparison with pure PVDF. In vitro cell culture confirmed that enhanced electrical charges could significantly improve cell behavior. Moreover, the scaffold presented a 97.9% increase in compressive strength and 24.5% increase in tensile strength, which was attributed to GO reinforcements forming strong interaction with PVDF chains. These positive results suggested that the scaffold might have possible application in bone tissue engineering.
In present study, a strategy is presented to construct a magnetic micro-environment in poly-l-lactide/polyglycolic acid (PLLA/PGA) scaffolds fabricated via selective laser sintering by incorporating Fe3O4 magnetic nanoparticles (MNPs), aiming to enhance cell viability and promote bone regeneration. In the micro-environment, each nanoparticle provides a nanoscale magnetic field to activate cellular responses. The results in vitro demonstrated that the magnetic scaffolds not only stimulated cell adhesion and viability, but also enhanced proliferation rate and alkaline phosphatase activity. Meanwhile, the compressive strength and modulus were increased by 81.9% and 71.6%, respectively, which were determined by the rigid enhancement effect of MNPs. Moreover, the magnetic scaffolds were implanted into rabbit radius bone defect in vivo, and the results indicated that the magnetic scaffolds significantly induced substantial blood vessel tissue, fibrous tissue and new bone tissue formation at 2 months post-implantation, revealing the excellent bone regeneration capability. These positive results indicate that the construction of magnetic micro-environment in scaffolds is a working countermeasure to promote bone regeneration.
Strontium ion (Sr2+) enabled us to endow polymer bone scaffolds with bioactivity owing to its excellent osteoinductive capacity. Nevertheless, the burst release of Sr2+ hindered its further application. Herein, strontium substituted hydroxyapatite (SrHA) was constructed to achieve a sustained release system. Specifically, Sr2+ could substitute Ca2+ in a HA lattice framework through ion exchange due to their similar ion radius. The ionic bond formed by Sr2+ and surrounding ions could prevent the rapid escape of Sr2+ and thereby achieve the sustained release of Sr2+. Subsequently, SrHA was introduced into the poly-l-lactic (PLLA) scaffold fabricated by selective laser sintering. Results demonstrated that PLLA/SrHA scaffolds presented a sustained Sr2+ release with a cumulative concentration of 5.6 mg/L over 28 days. The released Sr2+ significantly promoted the cell proliferation and differentiation. Furthermore, the tensile and compressive strengths of PLLA/SrHA scaffolds were also greatly enhanced in comparison with that of PLLA scaffolds. These positive findings demonstrated that PLLA/SrHA scaffolds had considerable potential for bone repair.
Piezoelectric polyvinylidene fluoride (PVDF) provided an opportunity for non-invasive in situ electrical stimulation of cell behavior, yet its electroactive β phase was difficult to obtain due to its instability in the molten state. Herein, polyaniline (PANI) protrusions were in situ oxidation-polymerized on molybdenum disulfide (MoS2) nanosheets (PANI-MoS2). Then, PANI-MoS2 was introduced into laser additive-manufactured PVDF scaffolds. On the one hand, PANI protrusions produced steric hindrance between adjacent MoS2 nanosheets and inhibited the stacking and aggregating of MoS2. On the other hand, PANI-MoS2 could serve as a platform to achieve interfacial polarization locking. Specifically, Mo–S dipoles in MoS2 and π electron clouds over the N atom in PANI locked −CH2 dipoles in PVDF through electrostatic and hydrogen bond interactions, respectively, which forced −CH2 to align perpendicularly to the basal plane of MoS2 and bialy to one side of the PVDF main chain, thereby forming a full-reverse planar zigzag configuration of the polarized β phase and maintaining its stable existence. The results demonstrated that the β phase of the scaffolds was significantly increased from 43 to 90%, which resulted in an enhanced electrical output performance. The improved electrical output greatly promoted osteoblast-like cell proliferation and differentiation. Furthermore, owing to the pulling-out effect of MoS2 and improved interfacial stress transfer between MoS2 and the polymer matrix, the mechanical properties of scaffolds were also enhanced. These findings suggested that the piezoelectric scaffolds had great potential in bone tissue engineering.
Poly l-lactic acid (PLLA) was limited in the further orthopaedic application due to its insufficient mechanical property and poor bioactivity. Graphene oxide (GO) is an effective reinforcement, whereas silicon-doped hydroxyapatite (Si-HA) possesses excellent bioactivity, but either GO or Si-HA tends to aggregate in PLLA matrix. In this study, a [email protected] nanosystem was achieved by in-situ growth of Si-HA on GO, and then incorporated into PLLA scaffold fabricated by laser sintering technology. On one hand, Si-HA on the surface of GO effectively prevented the aggregation of GO by acting as a barrier between GO nanosheets. On the other hand, GO hindered the aggregation of Si-HA by means of anchoring Si-HA. Results displayed that the compressive strength and modulus of the PLLA/[email protected] composite scaffold were enhanced by 85% and 120%, respectively. Meanwhile, the scaffold exhibited significantly improved bioactivity, and consequently promoted cell adhesion, proliferation and differentiation. The developed PLLA/[email protected] composite scaffold with excellent mechanical properties and superior bioactivity could serve as a promising substitute for bone repairing.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)