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In this review, different barrier membranes for guided bone regeneration (GBR) are described as a useful surgical technique to enhance bone regeneration in damaged alveolar sites before performing implants and fitting other dental appliances. The GBR procedure encourages bone regeneration through cellular exclusion and avoids the invasion of epithelial and connective tissues that grow at the defective site instead of bone tissue. The barrier membrane should satisfy various properties, such as biocompatibility, non-immunogenicity, non-toxicity, and a degradation rate that is long enough to permit mechanical support during bone formation. Other characteristics such as tissue integration, nutrient transfer, space maintenance and manageability are also of interest. In this review, various non-resorbable and resorbable commercially available membranes are described, based on expanded polytetrafluoroethylene, poly(lactic acid), poly(glycolic acid) and their copolymers. The polyester-based membranes are biodegradable, permit a single-stage procedure, and have higher manageability than non-resorbable membranes; however, they have shown poor biocompatibility. In contrast, membranes based on natural materials, such as collagen, are biocompatible but are characterized by poor mechanical properties and stability due to their early degradation. Moreover, new approaches are described, such as the use of multi-layered, graft-copolymer-based and composite membranes containing osteoconductive ceramic fillers as alternatives to conventional membranes.

Fibrous substrates, functioning as a temporary extracellular matrix, can be easily prepared by 5 electrospinning which allows to obtain fibrous matrices suitable as internal filler for nerve guidance 6 channels. In this study, gelatin micro-or nano-fibres have been prepared by electrospinning 7 technique by tuning gelatin concentration and solution flow rate. The influence of gelatin fibre 8 diameter on cell adhesion and proliferation was tested in vitro using Schwann cells (SC) and dorsal 9 root ganglia (DRG) explant cultures. Cell adhesion was evaluated by quantifying cell spreading area, 10 actin cytoskeleton organization and focal adhesion complex formation. Nano-fibres showed to 11 promote cell spreading and actin cytoskeleton organization, resulting in higher cellular adhesion 12 and proliferation rate. Yet, cell migration and motility were quantified by transwell and time lapse 13 assays respectively and results showed that cells cultured on micro-fibres displayed higher motility 14 and migration rate. Finally, DRG axon outgrowth resulted to be higher on micro-fibres. These data 15 suggest that gelatin electrospun fibres topography can be adjusted in order to modulate SC and 16 axons organization and that both nano-and micro-fibres are promising fillers for the design of 17 devices for peripheral nerve repair. 18 19

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The aim of this work was the preparation and characterization of scaffolds with mechanical and functional properties able to regenerate bone. Porous scaffolds made of chitosan/gelatin (POL) blends containing different amounts of a bioactive glass (CEL2), as inorganic material stimulating biomineralization, were fabricated by freeze-drying. Foams with different compositions (CEL2/POL 0/100; 40/60; 70/30 wt %/wt) were prepared. Samples were crosslinked using genipin (GP) to improve mechanical strength and thermal stability. The scaffolds were characterized in terms of their stability in water, chemical structure, morphology, bioactivity, and mechanical behavior. Moreover, MG63 osteoblast-like cells and periosteal-derived stem cells were used to assess their biocompatibility. CEL2/POL samples showed interconnected pores having an average diameter ranging from 179 ± 5 μm for CEL2/POL 0/100 to 136 ± 5 μm for CEL2/POL 70/30. GP-crosslinking and the increase of CEL2 amount stabilized the composites to water solution (shown by swelling tests). In addition, the SBF soaking experiment showed a good bioactivity of the scaffold with 30 and 70 wt % CEL2. The compressive modulus increased by increasing CEL2 amount up to 2.1 ± 0.1 MPa for CEL2/POL 70/30. Dynamical mechanical analysis has evidenced that composite scaffolds at low frequencies showed an increase of storage and loss modulus with increasing frequency; furthermore, a drop of E' and E″ at 1 Hz was observed, and for higher frequencies both moduli increased again. Cells displayed a good ability to interact with the different tested scaffolds which did not modify cell metabolic activity at the analyzed points. MTT test proved only a slight difference between the two cytotypes analyzed.