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.

Formability of Printing Ink for Melt Electrowriting

3D printing,also called additive manufacturing,is being used increasingly in tissue engineering.However,the printing accuracy remains limited,making it difficult to prepare a tissue engineering scaffold with high precision and high porosity.Melt electrowriting(MEW)technology is based on extrusion printing,in which an extruded material is pulled by the action of an electric field,thereby reducing the fiber diameter and improving the printing accuracy.However,MEW technology imposes high requirements on the material properties,and therefore,few printing materials are currently available for use in this process.The present study investigates the characteristics and molding conditions of polycaprolactone,a commonly used printing material,as well as other materials such as poly(lactic-co-glycolic acid),poly(ethylene glycol)diacrylate/polyethylene oxide,gelatin methacrylate,and hyaluronic acid methacrylate for MEW applications,and develops new and suitable inks for MEW that will provide more and better choices for constructing a bioactive scaffold in future tissue engineering research.Experiments suggest that a printing ink should have low electrical conductivity,suitable viscosity,and high curing speed for realizing successful printing.

3D printing of bio-instructive materials:Toward directing the cell

Fabrication of functional scaffolds for tissue engineering and regenerative medicine applications requires material systems with precise control over cellular performance.3D printing is a powerful technique to create highly complex and multicomponent structures with well-defined architecture and composition.In this review paper,we explore extrusion-based 3D printing methods(EBP,i.e.,Near Field Electrospinning(NFES),Melt Electrowriting(MEW),Fused Deposition Modeling(FDM),and extrusion bioprinting)in terms of their ability to produce scaffolds with bio-instructive properties.These material systems provide spatio-temporal guidance for cells,allowing controlled tissue regeneration and maturation.Multiple physical and biochemical cues introduced to the EBP scaffolds are evaluated in their ability to direct cell alignment,proliferation,differentiation,specific ECM production,and tissue maturation.We indicate that the cues have different impacts depending on the material system,cell type used,or coexistence of multiple cues.Therefore,they must be carefully chosen based on the targeted application.We propose future directions in bio-instructive materials development,including such concepts as metamaterials,hybrid living materials,and 4D printing.The review gathers the knowledge essential for designing new materials with a controlled cellular response,fabrication of advanced engineered tissue,and developing a better understanding of cell biology,especially in response to the biomaterial.

Tissue-specific melt electrowritten polymeric scaffolds for coordinated regeneration of soft and hard periodontal tissues

Periodontitis is a chronic inflammatory condition that often causes serious damage to tooth-supporting tissues.The limited successful outcomes of clinically available approaches underscore the need for therapeutics that cannot only provide structural guidance to cells but can also modulate the local immune response.Here,three-dimensional melt electrowritten(i.e.,poly(ε-caprolactone))scaffolds with tissue-specific attributes were engineered to guide differentiation of human-derived periodontal ligament stem cells(hPDLSCs)and mediate macrophage polarization.The investigated tissue-specific scaffold attributes comprised fiber morphology(aligned vs.random)and highly-ordered architectures with distinct strand spacings(small 250μm and large 500μm).Macrophages exhibited an elongated morphology in aligned and highly-ordered scaffolds,while maintaining their round-shape on randomly-oriented fibrous scaffolds.Expressions of periostin and IL-10 were more pronounced on the aligned and highly-ordered scaffolds.While hPDLSCs on the scaffolds with 500μm strand spacing show higher expression of osteogenic marker(Runx2)over 21 days,cells on randomly-oriented fibrous scaffolds showed upregulation of M1 markers.In an orthotopic mandibular fenestration defect model,findings revealed that the tissue-specific scaffolds(i.e.,aligned fibers for periodontal ligament and highly-ordered 500μm strand spacing fluorinated calcium phosphate[F/CaP]-coated fibers for bone)could enhance the mimicking of regeneration of natural periodontal tissues.