3D additive manufactured composite scaffolds with antibiotic-loaded lamellar fillers for bone infection prevention and tissue regeneration

Bone infections following open bone fracture or implant surgery remain a challenge in the orthopedics field.In order to avoid high doses of systemic drug administration,optimized local antibiotic release from scaffolds is required.3D additive manufactured(AM)scaffolds made with biodegradable polymers are ideal to support bone healing in non-union scenarios and can be given antimicrobial properties by the incorporation of antibiotics.In this study,ciprofloxacin and gentamicin intercalated in the interlamellar spaces of magnesium aluminum layered double hydroxides(MgAl)andα-zirconium phosphates(ZrP),respectively,are dispersed within a thermoplastic polymer by melt compounding and subsequently processed via high temperature melt extrusion AM(~190◦C)into 3D scaffolds.The inorganic fillers enable a sustained antibiotics release through the polymer matrix,controlled by antibiotics counterions exchange or pH conditions.Importantly,both antibiotics retain their functionality after the manufacturing process at high temperatures,as verified by their activity against both Gram+and Gram-bacterial strains.Moreover,scaffolds loaded with filler-antibiotic do not impair human mesenchymal stromal cells osteogenic differentiation,allowing matrix mineralization and the expression of relevant osteogenic markers.Overall,these results suggest the possibility of fabricating dual functionality 3D scaffolds via high temperature melt extrusion for bone regeneration and infection prevention.

Advances in spray products for skin regeneration

To date,skin wounds are still an issue for healthcare professionals.Although numerous approaches have been developed over the years for skin regeneration,recent advances in regenerative medicine offer very promising strategies for the fabrication of artificial skin substitutes,including 3D bioprinting,electrospinning or spraying,among others.In particular,skin sprays are an innovative technique still under clinical evaluation that show great potential for the delivery of cells and hydrogels to treat acute and chronic wounds.Skin sprays present significant advantages compared to conventional treatments for wound healing,such as the facility of application,the possibility to treat large wound areas,or the homogeneous distribution of the sprayed material.In this article,we review the latest advances in this technology,giving a detailed description of investigational and currently commercially available acellular and cellular skin spray products,used for a variety of diseases and applying different experimental materials.Moreover,as skin sprays products are subjected to different classifications,we also explain the regulatory pathways for their commercialization and include the main clinical trials for different skin diseases and their treatment conditions.Finally,we argue and suggest possible future trends for the biotechnology of skin sprays for a better use in clinical dermatology.

Thiol-ene conjugation of a VEGF peptide to electrospun scaffolds for potential applications in angiogenesis

Vascular endothelial growth factor(VEGF)plays a vital role in promoting attachment and proliferation of endothelial cells,and induces angiogenesis.In recent years,much research has been conducted on the functionalization of tissue engineering scaffolds with VEGF or a VEGF-mimetic peptide to promote angiogenesis.However,most chemical reactions are nonspecific and require organic solvents,which can compromise control over functionalization and alter peptide/protein activity.An attractive alternative is the fabrication of functionalizable electrospun fibers,which can overcome these hurdles.In this study,we used thiol-ene chemistry for the conjugation of a VEGF-mimetic peptide to the surface of poly(ε-caprolactone)(PCL)fibrous scaffolds with varying amounts of a functional PCL-diacrylate(PCL-DA)polymer.30%PCL-DA was selected due to homogeneous fiber morphology.A VEGF-mimetic peptide was then immobilized on PCL-DA fibrous scaffolds by a light-initiated thiol-ene reaction.7-Mercapto-4-methylcoumarin,RGD-FITC peptide and VEGF-TAMRA mimetic peptide were used to validate the thiol-ene reaction on the fibrous scaffolds.Tensile strength and elastic modulus of the 30%PCL-DA fibrous scaffolds were significantly increased after the reaction.Conjugation of the 30%PCL-DA fibrous scaffolds with the VEGF peptide increased the surface water wettability of the scaffolds.Patterned structures could be obtained after using a photomask on the fibrous film.Moreover,in vitro studies indicated that scaffolds functionalized with the VEGF-mimetic peptide were able to induce phosphorylation of the VEGF receptor and enhanced HUVECs survival,proliferation and adhesion.A chick chorioallantoic membrane(CAM)assay further indicated that the VEGF peptide functionalized scaffolds were able to promote angiogenesis in vivo.These results show that scaffold functionalization can be controlled via a simple polymer mixing approach,and that the functionalized VEGF peptide-scaffolds have potential for vascular tissue regeneration.

Assessing the response of human primary macrophages to defined fibrous architectures fabricated by melt electrowriting

The dual role of macrophages in the healing process depends on macrophage ability to polarize into phenotypes that can propagate inflammation or exert anti-inflammatory and tissue-remodeling functions.Controlling scaf-fold geometry has been proposed as a strategy to influence macrophage behavior and favor the positive host response to implants.Here,we fabricated Polycaprolactone(PCL)scaffolds by Melt Electrowriting(MEW)to investigate the ability of scaffold architecture to modulate macrophage polarization.Primary human macrophages unpolarized(M0)or polarized into M1,M2a,and M2c phenotypes were cultured on PCL films and MEW scaffolds with pore geometries(square,triangle,and rhombus grid)characterized by different angles.M0,M2a,and M2c macrophages wrapped along the fibers,while M1 macrophages formed clusters with rounded cells.Cell bridges were formed only for angles up to 90◦.No relevant differences were found among PCL films and 3D scaffolds in terms of surface markers.CD206 and CD163 were highly expressed by M2a and M2c macrophages,with M2a macrophages presenting also high levels of CD86.M1 macrophages expressed moderate levels of all markers.The rhombus architecture promoted an increased release by M2a macrophages of IL10,IL13,and sCD163 compared to PCL films.The proangiogenic factor IL18 was also upregulated by the rhombus configuration in M0 and M2a macrophages compared to PCL films.The interesting findings obtained for the rhombus architecture represent a starting point for the design of scaffolds able to modulate macrophage phenotype,prompting investigations addressed to verify their ability to facilitate the healing process in vivo.