A biomimetic self-assembling peptide promotes bone regeneration in vivo: A rat cranial defect study

Rationally designed, pH sensitive self-assembling β-peptides (SAPs) which are capable of reversibly switching between fluid and gel phases in response to environmental triggers are potentially useful injectable scaffolds for skeletal tissue engineering applications. SAP P₁₁-4 (CH₃COQQRFEWEFEQQNH₂) has been shown to nucleate hydroxyapatite mineral de novo and has been used in dental enamel regeneration. We hypothesised that addition of mesenchymal stromal cells (MSCs) would enhance the in vivo effects of P₁₁-4 in promoting skeletal tissue repair. Cranial defects were created in athymic rats and filled with either Bio-Oss® (anorganic bone chips) or P₁₁-4 ± human dental pulp stromal cells (HDPSCs). Unfilled defects served as controls. After 4 weeks, only those defects filled with P₁₁-4 alone showed significantly increased bone regeneration (almost complete healing), compared to unfilled control defects, as judged using quantitative micro-CT, histology and immunohistochemistry. In silico modelling indicated that fibril formation may be essential for any mineral nucleation activity. Taken together, these data suggest that self-assembling peptides are a suitable scaffold for regeneration of bone tissue in a one step, cell-free therapeutic approach.

Creating hierarchical porosity hydroxyapatite scaffolds with osteoinduction by three-dimensional printing and microwave sintering

Hierarchical porosity, which includes micropores and macropores in scaffolds, contributes to important multiple biological functions for tissue regeneration. This paper introduces a two-step method of combining three-dimensional printing (3DP) and microwave sintering to fabricate two-level hierarchical porous scaffolds. The results showed that 3D printing made the macroporous structure well-controlled and microwave sintering generated micropores on the macropore surface. The resulting hierarchical macro/microporous hydroxyapatite scaffold induced bone formation following intramuscular implantation. Moreover, when comparing the hierarchical macro/microporous hydroxyapatite scaffold to the non-osteoinductive hydroxyapatite scaffolds (either 3D printed or H₂O₂ foamed) subjected to muffle sintering which do not have micropores, the critical role of micropores in material-driven bone formation was shown. The findings presented herein could be useful for the further optimization of bone grafting materials for bone regeneration.

Combinatorial MAPLE deposition of antimicrobial orthopedic maps fabricated from chitosan and biomimetic apatite powders

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248nm, τFWHM=25ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosan-rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite.

Development of functionalized multi-walled carbon nanotube-based polysaccharide–hydroxyapatite scaffolds for bone tissue engineering

fMWCNT–amylopectin–HAP and fMWCNT–gellan gum–HAP were prepared and characterized and their in vitro cell proliferation and ALP activity were checked for the first time.