Unveiling the potential of melt electrowriting in regenerative dental medicine

Abstract

For nearly three decades, tissue engineering strategies have been leveraged to devise effective therapeutics for dental, oral, and craniofacial (DOC) regenerative medicine and treat permanent deformities caused by many debilitating health conditions. In this regard, additive manufacturing (AM) allows the fabrication of personalized scaffolds that have the potential to recapitulate native tissue morphology and biomechanics through the utilization of several 3D printing techniques. Among these, melt electrowriting (MEW) is a versatile direct electrowriting process that permits the development of well-organized fibrous constructs with fiber resolutions ranging from micron to nanoscale. Indeed, MEW offers great prospects for the fabrication of scaffolds mimicking tissue specificity, healthy and pathophysiological microenvironments, personalized multi-scale transitions, and functional interfaces for tissue regeneration in medicine and dentistry. Excitingly, recent work has demonstrated the potential of converging MEW with other AM technologies and/or cell-laden scaffold fabrication (bioprinting) as a favorable route to overcome some of the limitations of MEW for DOC tissue regeneration. In particular, such convergency fabrication strategy has opened great promise in terms of supporting multi-tissue compartmentalization and predetermined cell commitment. In this review, we offer a critical appraisal on the latest advances in MEW and its convergence with other biofabrication technologies for DOC tissue regeneration. We first present the engineering principles of MEW and the most relevant design aspects for transition from flat to more anatomically relevant 3D structures while printing highly-ordered constructs. Secondly, we provide a thorough assessment of contemporary achievements using MEW scaffolds to study and guide soft and hard tissue regeneration, and draw a parallel on how to extrapolate proven concepts for applications in DOC tissue regeneration. Finally, we offer a combined engineering/clinical perspective on the fabrication of hierarchically organized MEW scaffold architectures and the future translational potential of site-specific, single-step scaffold fabrication to address tissue and tissue interfaces in dental, oral, and craniofacial regenerative medicine. STATEMENT OF SIGNIFICANCE: Melt electrowriting (MEW) techniques can further replicate the complexity of native tissues and could be the foundation for novel personalized (defect-specific) and tissue-specific clinical approaches in regenerative dental medicine. This work presents a unique perspective on how MEW has been translated towards the application of highly-ordered personalized multi-scale and functional interfaces for tissue regeneration, targeting the transition from flat to anatomically-relevant three-dimensional structures. Furthermore, we address the value of convergence of biofabrication technologies to overcome the traditional manufacturing limitations provided by multi-tissue complexity. Taken together, this work offers abundant engineering and clinical perspectives on the fabrication of hierarchically MEW architectures aiming towards site-specific implants to address complex tissue damage in regenerative dental medicine.

Keywords: 3D printing; Biofabrication; Dentistry; Melt electrowriting; Regeneration; Scaffolds.

Fig. 1.

Schematic illustration of the anatomy of relevant dental, oral, and craniofacial (DOC) tissues; craniomaxillofacial bone and periodontal complex (i.e., alveolar bone, gingiva, periodontal ligament [PDL], and cementum).

Fig. 2.

MEW devices components of air-pressure-assisted dispensing, electrical heating system, and collector at different configurations (A) Flat-computer-assisted collector. From Castilho et al. ( 2017) [21]. (B) MEW fiber deposition over rotating grounded mandrel to form tubular scaffolds, From Genderen et al. (2020) [20].

Fig. 3.

Cell’s behaviors in various MEW design. (A) Well-aligned (0-90°-oriented junctions) fibrous 3D architecture with 500 μm strand spacing shows human-derived mesenchymal stem cells (hMSCs)/MEW poly(e-caprolactone) scaffold interaction. From Dubey et al. (2020) [7]. (B) Confocal microscopy images and SEM images show significant hPDLSCs bridging in 500 μm F/CaP-coated scaffolds and non-coated scaffolds after 7 days. Note pronounced cell spreading was detected along the nanostructured F/CaP-coated scaffolds (white arrows indicate important filopodia protrusion along and around the fibers). From Daghrery et al. (2021) [27]. (C) MEW fiber orientation and cellular organization in anterior cruciate ligament tissue engineering. From Gwiazda et al. (2020) [81]. (D) SEM images of highly-order MEW porous and gradient scaffolds and mineralization of hOB on MEW scaffolds after 30 days of culture. From Abbasi et al. (2020) [42].

Fig. 4.

Biomimetic print designs of MES scaffolds. (A) Biomimetic serpentine patterns design for heart valve tissue engineering and (B) Custom-made flow loop system, where the MEW scaffold is sutured into a silicone aortic root as single leaflets and functionality assessment of the opening and closing sequence of the valve. From Saidy et al. (2019) [45]. (C) Characterization of scaffolds printed at 30°, 45°, and 60° winding angle for fabrication of personalized aortic root scaffolds. From Saidy et al. (2020) [57]. (D) Macroscale and microscopic images of MEW-based personalized biodegradable coronary stents. From Somszor et al., 2020 [46]..

Fig. 5.

Various complex MEW scaffold design. (A) Novel complex overhanging structures by controlled layer shifting and multiphasic walls formed by an abrupt change in printing trajectory. From Liashenko et al. ( 2020) [24]. (B) Ultrafast 3D printing of cylindrical microstructures single suspended polyethylene oxide (PEO) fiber bridging a gap between 2 parallel nano wall using electrostatic jet deflection. From Liashenko et al. ( 2020) [59]. (C) Web-based application, showing the printing path for an eight pivot point, to generate printing path for porous tubes like structure for TE. From McColl et al. (2018) [19]. (D) Variants of stabilizing fibers produced in a radial manner. From Ruijter et al. (2018) [67].

Fig. 6.

MEW-hydrogel reinforced composite approaches. (A) MEW enabled a good control intended 0°-90° crosshatch at 200 μm, 400 μm, and 600 μm fiber spacing for fiber-reinforced hydrogels of fibrin, sPEG/Hep and hydrogels. From Bas et al. (2017) [65]. (B) Amorphous magnesium phosphate (AMP) modified gelatin methacryloyl (GelMA) hydrogel infiltrated highly porous MEW PCL meshes with well-controlled 3D architecture. Note the hydrogel phase uniformly infiltrated within the highly order porous structure. Stress-strain curves and stiffness of GelMA indicates higher results when increasing the number of PCL meshes. From Dubey et al. (2020) [7].

Fig. 7.

Multilayered/Multiphasic scaffolds for osteochondral and periodontal regeneration. (A) Multiphasic construct for vertical bone augmentation, graphic view of melt electrospun mesh inserted to FDM scaffold and PLLA dome shaped construct and Surgical implantation of constructs onto the sheep calvarium. Adapted from. From Vaquette et al. (2021) [70]. (B) Schematic illustration of the multiscale osteochondral construct processed via melt writing electrospun fibers reinforced hydrogel-ceramic interfaces. From Diloksumpan et al. (2020) [74]. (C) Bone regeneration assessment of offset and gradient MEW scaffolds implanted in rat calvarial defects and 3-D reconstructed Micro-CT images showing the degree of bone repair at 4 weeks and 8 weeks post-implantation. From Abbasi et al. (2020) [75].

Fig. 8.

Multitechnology biofabrication approaches. (A) Cell distribution and out-of-plane printing architecture. From Ruijter et al. (2019) [77]. (B) Bilayer self-folded tube via 3D printing and melt electrowriting (MEW) of PCL fibers on methacrylated alginate (AA-MA) hydrogel, can be folded at different directions direction; parallel, perpendicular or diagonal-wise. The presence of MEW fibers support Myofibroblast orientation to a higher degree not achievable by AA-MA film without fibers. From Constante et al. (2021) [78]. (C) Cell electrowritten (CEW) fibers on gelnor-based cell-laden scaffolds compared to conventional extrusion bioprinting. Single cells precisely aligned along the pattern in CEW while extrusion-bioprinted fibers had thicker filament of multiple cells distributed homogeneously. CEW allows simultaneous multiple bioinks printing in a single construct. From Castilho et al. (2021) [28].

Fig. 9.

Current In vitro platforms for MEW for studying disease and engineering tissues. (A) Macrophages and MEW scaffold interaction suggested spontaneous differentiation of M1 toward the anti-inflammatory type (M2), while both M1-markers, IL-1β and IL-8, were decreased and the M2 markers, CD163 and IL-10, rather increased. From. Tylek et al. (2020) [43]. (B) Schematic of the MEW circular structure of a 3D in vitro radial culture device for glioblastoma cell migration analysis. From Bakirci et al. (2020) [84]. (C) Adipose stem cells (ASC) spheroids in box-structured MEW scaffolds shows attachment to the fibers and adjacent spheroids. From McMaster et al. (2019) [44].

Fig. 10.

Tissue-specific scaffolds/constructs that direct stem cells differentiation and mimic the biomechanics of the tissue to be regenerated. (A) F/CaP scaffold exhibited distinct surface texture and bioactivity when immersed in SBF. From Daghrery et al. (2021) [27]. (B) Non flat geometries via resurfacing PCL to mimicking the contour of a human femoral condyle surface, enables cartilage-like tissue formation. From Peiffer et al. (2021) [25].

Fig. 11.

Highly-Ordered, nanostructured fluorinated cap-coated melt electrowritten scaffold for periodontal regeneration (A) Generation and characterization of rat mandibular periodontal fenestration defect model. (B) Micro-CT assessments and MT-stained indicated neotissue formation and Sharpey’s fiber insertions to new bone and cementum formation after 6 weeks post-implantation of MEW-F/CaP scaffold. From Daghrery et al. (2021) [27].