Three-dimensional Porous Scaffolds Research Articles

A facile strategy for tuning the density of surface-grafted biomolecules for melt extrusion-based additive manufacturing applications

AbstractMelt extrusion-based additive manufacturing (ME-AM) is a promising technique to fabricate porous scaffolds for tissue engineering applications. However, most synthetic semicrystalline polymers do not possess the intrinsic biological activity required to control cell fate. Grafting of biomolecules on polymeric surfaces of AM scaffolds enhances the bioactivity of a construct; however, there are limited strategies available to control the surface density. Here, we report a strategy to tune the surface density of bioactive groups by blending a low molecular weight poly(ε-caprolactone)5k (PCL5k) containing orthogonally reactive azide groups with an unfunctionalized high molecular weight PCL75k at different ratios. Stable porous three-dimensional (3D) scaffolds were then fabricated using a high weight percentage (75 wt.%) of the low molecular weight PCL5k. As a proof-of-concept test, we prepared films of three different mass ratios of low and high molecular weight polymers with a thermopress and reacted with an alkynated fluorescent model compound on the surface, yielding a density of 201–561 pmol/cm2. Subsequently, a bone morphogenetic protein 2 (BMP-2)-derived peptide was grafted onto the films comprising different blend compositions, and the effect of peptide surface density on the osteogenic differentiation of human mesenchymal stromal cells (hMSCs) was assessed. After two weeks of culturing in a basic medium, cells expressed higher levels of BMP receptor II (BMPRII) on films with the conjugated peptide. In addition, we found that alkaline phosphatase activity was only significantly enhanced on films containing the highest peptide density (i.e., 561 pmol/cm2), indicating the importance of the surface density. Taken together, these results emphasize that the density of surface peptides on cell differentiation must be considered at the cell-material interface. Moreover, we have presented a viable strategy for ME-AM community that desires to tune the bulk and surface functionality via blending of (modified) polymers. Furthermore, the use of alkyne–azide “click” chemistry enables spatial control over bioconjugation of many tissue-specific moieties, making this approach a versatile strategy for tissue engineering applications. Graphic abstract

Meniscal repair with additive manufacture of bioresorbable polymer: From physicochemical characterization to implantation of 3D printed poly (L-co-D, L lactide-co-trimethylene carbonate) with autologous stem cells in rabbits.

Three-dimensional (3D) structures are actually the state-of-the-art technique to create porous scaffolds for tissue engineering. Since regeneration in cartilage tissue is limited due to intrinsic cellular properties this study aims to develop and characterize three-dimensional porous scaffolds of poly (L-co-D, L lactide-co-trimethylene carbonate), PLDLA-TMC, obtained by 3D fiber deposition technique. The PLDLA-TMC terpolymer scaffolds (70:30), were obtained and characterized by scanning electron microscopy, gel permeation chromatography, differential scanning calorimetry, thermal gravimetric analysis, compression mechanical testing and study on in vitro degradation, which showed its amorphous characteristics, cylindrical geometry, and interconnected pores. The in vitro degradation study showed significant loss of mechanical properties compatible with a decrease in molar mass, accompanied by changes in morphology. The histocompatibility association of mesenchymal stem cells from rabbit's bone marrow, and PLDLA-TMC scaffolds, were evaluated in the meniscus regeneration, proving the potential of cell culture at in vivo tissue regeneration. Nine New Zealand rabbits underwent total medial meniscectomy, yielding three treatments: implantation of the seeded PLDLA-TMC scaffold, implantation of the unseeded PLDLA-TMC and negative control (defect without any implant). After 24weeks, the results revealed the presence of fibrocartilage in the animals treated with polymer. However, the regeneration obtained with the seeded PLDLA-TMC scaffolds with mesenchymal stem cells had become intimal to mature fibrocartilaginous tissue of normal meniscus both macroscopically and histologically. This study demonstrated the effectiveness of the PLDLA-TMC scaffold in meniscus regeneration and the potential of mesenchymal stem cells in tissue engineering, without the use of growth factors. It is concluded that bioresorbable polymers represent a promising alternative for tissue regeneration.

Development of porous hydroxyapatite/PVA/gelatin/alginate hybrid flexible scaffolds with improved mechanical properties for bone tissue engineering

Porous scaffolds based on gelatin and hydroxyapatite particles (HAp) are promising for applications in bone tissue engineering and regenerative medicine. However, they are not ideal for stress and shock protection due to low compressive strength, brittleness, and poor toughness. Herein, we developed porous hybrid scaffolds by combining multiple components into a single bone scaffold, including hydroxyapatite nanoparticles (HAp NPs), alginate, polyvinyl alcohol (PVA), and gelatin with different gelatin/PVA composition ratios. HAp NPs were synthesized in situ in PVA solution and scaffolds were fabricated using a freeze-drying method. The results showed good physicochemical properties of the scaffolds: formation of pure HAp NPs phase, high porosity, large pore sizes, large swelling capacity depending on varying gelatin/PVA ratios, as well as a long-term degradation rate up to 28 days. The porous scaffolds exhibited compressive strength close to the cancellous bone with stress-strain behavior exhibiting three-stage flexible behavior indicating improved fracture resistance with an energy absorbing capability up to 1.9 MJ/m3. The scaffolds have a yield strength of 70–403 kPa, a compressive strength at 65 % strain of 0.96–1.80 MPa, a nonporous elastic modulus of 10.44–12.40 GPa, and a densification strain of approximately 0.92 %. This work develops three-dimensional (3D) porous hybrid bone scaffolds with mechanical strength within the minimum compressive strength of cancellous bone and mechanical energy absorption capacity favor for cancellous bone repair, bone tissue engineering, and regenerative medicine applications.

An Overview on the Big Players in Bone Tissue Engineering: Biomaterials, Scaffolds and Cells.

Presently, millions worldwide suffer from degenerative and inflammatory bone and joint issues, comprising roughly half of chronic ailments in those over 50, leading to prolonged discomfort and physical limitations. These conditions become more prevalent with age and lifestyle factors, escalating due to the growing elderly populace. Addressing these challenges often entails surgical interventions utilizing implants or bone grafts, though these treatments may entail complications such as pain and tissue death at donor sites for grafts, along with immune rejection. To surmount these challenges, tissue engineering has emerged as a promising avenue for bone injury repair and reconstruction. It involves the use of different biomaterials and the development of three-dimensional porous matrices and scaffolds, alongside osteoprogenitor cells and growth factors to stimulate natural tissue regeneration. This review compiles methodologies that can be used to develop biomaterials that are important in bone tissue replacement and regeneration. Biomaterials for orthopedic implants, several scaffold types and production methods, as well as techniques to assess biomaterials' suitability for human use-both in laboratory settings and within living organisms-are discussed. Even though researchers have had some success, there is still room for improvements in their processing techniques, especially the ones that make scaffolds mechanically stronger without weakening their biological characteristics. Bone tissue engineering is therefore a promising area due to the rise in bone-related injuries.

Soy conglycinin amyloid fibril and chitosan complex scaffold for cultivated meat application

This study addresses the critical need in cultivated meat production for suitable scaffolds that support the growth and differentiation of muscle cells. We explore the synergy of soy conglycinin (7S) amyloid protein fibrils and chitosan to create three-dimensional (3D) porous scaffolds, specifically designed for this application. By varying the molecular weight and deacetylation degrees of chitosan, we employed a controlled temperature water annealing method to produce these complex scaffolds. The formation mechanism of the 7S-chitosan scaffolds was elucidated through molecular simulation and Fourier-transform infrared (FTIR) analysis. Characterization of the scaffolds revealed pore sizes within the 50–250 μm range, porosities from 71% to 78%, and compressive moduli varying between 4.8 and 15.3 kPa, dependent on the chitosan's deacetylation degree and molecular weight. Notably, these scaffolds maintained structural integrity in refrigerated Phosphate Buffered Saline (PBS) for up to three months and effectively supported the growth and differentiation of C2C12 mouse skeletal muscle cells without necessitating additional cell adhesion enhancements. Their mechanical properties, comparable to natural muscle tissue, and compatibility with high-temperature sterilization processes, underscore their potential as innovative solutions in the field of cultivated meat production.

Multilayered Shape-Morphing Scaffolds with a Hierarchical Structure for Uterine Tissue Regeneration.

Owing to dysfunction of the uterus, millions of couples around the world suffer from infertility. Different from conventional treatments, tissue engineering provides a new and promising approach to deal with difficult problems such as human tissue or organ failure. Adopting scaffold-based tissue engineering, three-dimensional (3D) porous scaffolds in combination with stem cells and appropriate biomolecules may be constructed for uterine tissue regeneration. In this study, a hierarchical tissue engineering scaffold, which mimicked the uterine tissue structure and functions, was designed, and the biomimicking scaffolds were then successfully fabricated using solvent casting, layer-by-layer assembly, and 3D bioprinting techniques. For the multilayered, hierarchical structured scaffolds, poly(l-lactide-co-trimethylene carbonate) (PLLA-co-TMC, "PLATMC" in short) and poly(lactic acid-co-glycolic acid) (PLGA) blends were first used to fabricate the shape-morphing layer of the scaffolds, which was to mimic the function of myometrium in uterine tissue. The PLATMC/PLGA polymer blend scaffolds were highly stretchable. Subsequently, after etching of the PLATMC/PLGA surface and employing estradiol (E2), polydopamine (PDA), and hyaluronic acid (HA), PDA@E2/HA multilayer films were formed on PLATMC/PLGA scaffolds to build an intelligent delivery platform to enable controlled and sustained release of E2. The PDA@E2/HA multilayer films also improved the biological performance of the scaffold. Finally, a layer of bone marrow-derived mesenchymal stem cell (BMSC)-laden hydrogel [which was a blend of gelatin methacryloyl (GelMA) and gelatin (Gel)] was 3D printed on the PDA@E2/HA multilayer films of the scaffold, thereby completing the construction of the hierarchical scaffold. BMSCs in the GelMA/Gel hydrogel layer exhibited excellent cell viability and could spread and be released eventually upon biodegradation of the GelMA/Gel hydrogel. It was shown that the hierarchically structured scaffolds could evolve from the initial flat shape into the tubular structure completely in an aqueous environment at 37 °C, fulfilling the requirement for curved scaffolds for uterine tissue engineering. The biomimicking scaffolds with a hierarchical structure and curved shape, high stretchability, and controlled and sustained E2 release appear to be very promising for uterine tissue regeneration.

Structural descriptor and surrogate modeling for design of biodegradable scaffolds

Biodegradable scaffolds are important to regenerative medicine in that they provide an amicable environment for tissue regrowth. However, establishing structure-property (SP) relationships for scaffold design is challenging due to the complexity of the three-dimensional porous scaffold geometry. The complexity requires high-dimensional geometric descriptors. The training of such a SP surrogate model will need a large amount of experimental or simulation data. In this work, a schema of constructing SP relationship surrogates is developed to predict the degraded mechanical properties from the initial scaffold geometry. A new structure descriptor, the extended surfacelet transform (EST), is proposed to capture important details of pores associated with the degradation of scaffolds. The efficiency is further enhanced with principal component analysis to reduce the high-dimensional EST data into a low-dimensional representation. The schema also includes a kinetic Monte Carlo biodegradation model to simulate the biodegradation of polymer scaffolds and to generate the training data for the formation of SP relationships. The schema is demonstrated with the design of polycaprolactone biodegradable scaffolds by connecting the initial scaffold geometry to the degraded compressive modulus.

A biomimetic three-dimensional porous scaffold of mineralized recombinant collagen-sodium alginate for efficiently repairing critical-size cranial defects

The reconstruction of critical-size bone defects caused by trauma, tumor resection, and congenital anomalies remains a fundamental challenge in tissue engineering. Biomimetic scaffolds have received extensive attention for the discovery of advanced artificial bone substitutes due to their inherent biocompatibility and biodegradability. Herein, we have for the first time developed a biomimetic three-dimensional porous scaffold of mineralized recombinant collagen-sodium alginate (MRCSA) with supreme healing efficacy for critical-size cranial defects. In situ biomineralization using recombinant collagen as the unique biotemplate results in the formation of nano-hydroxyapatite with well-ordered mineralized recombinant collagen with fibrous morphology. The MRCSA scaffold finely mimics the organic-inorganic composition and the uniform porous nanostructures of natural bone, which exhibits excellent biocompatibility, adequate biodegradability, superior cellular activity, and exceptional osteogenic differentiation capability. Magnetic resonance imaging (MRI), Micro-computed tomography (micro-CT), and histological characterization of rat models of critical-size cranial defects have consistently demonstrated that the MRCSA scaffold has regenerated an abundance of new bones to refill the defect sites with much higher bone mineral density, bone volume/total volume as well as trabeculae. The novel biomimetic scaffold provides a remarkably improved remedy of critical-size cranial defects, suggesting very promising applications in orthopedics and plastics.

Consolidation of Spray-Dried Amorphous Calcium Phosphate by Ultrafast Compression: Chemical and Structural Overview.

A large amount of research in orthopedic and maxillofacial domains is dedicated to the development of bioactive 3D scaffolds. This includes the search for highly resorbable compounds, capable of triggering cell activity and favoring bone regeneration. Considering the phosphocalcic nature of bone mineral, these aims can be achieved by the choice of amorphous calcium phosphates (ACPs). Because of their metastable property, these compounds are however to-date seldom used in bulk form. In this work, we used a non-conventional "cold sintering" approach based on ultrafast low-pressure RT compaction to successfully consolidate ACP pellets while preserving their amorphous nature (XRD). Complementary spectroscopic analyses (FTIR, Raman, solid-state NMR) and thermal analyses showed that the starting powder underwent slight physicochemical modifications, with a partial loss of water and local change in the HPO42- ion environment. The creation of an open porous structure, which is especially adapted for non-load bearing bone defects, was also observed. Moreover, the pellets obtained exhibited sufficient mechanical resistance allowing for manipulation, surgical placement and eventual cutting/reshaping in the operation room. Three-dimensional porous scaffolds of cold-sintered reactive ACP, fabricated through this low-energy, ultrafast consolidation process, show promise toward the development of highly bioactive and tailorable biomaterials for bone regeneration, also permitting combinations with various thermosensitive drugs.

ASSESSMENT OF MECHANICAL RESPONSES BETWEEN TRABECULAR BONES AND POROUS SCAFFOLDS UNDER STATIC LOADING AND FLUID FLOW CONDITIONS: A MULTISCALE APPROACH

A three-dimensional porous scaffold is one of the standard and evocative approaches to create a favorable biomechanical environment in tissue engineering for tissue regeneration and repair. The architectural design parameters (e.g., pore-shape, size, distribution and interconnectivity; permeability; specific surface area; etc.) of the porous model have significant influence on their mechano-biological behavior. Along with this, interstitial fluid flow dynamics within the porous scaffold also regulate cell behavior. Therefore, von Mises stress, deformation, wall shear stress, and permeability across the model have been investigated. In this work, a multiscale approach has been applied to explore the various mechanical stimuli that control the cell mechanobiology within a scaffold and compare it to the natural bone with different porosity to identify which architectural design of the scaffold is close to the bone.

3D printed bioactive calcium silicate ceramics as antibacterial scaffolds for hard tissue engineering

VAT photopolymerization technology was applied to fabricate three-dimensional (3D) porous β-Ca2SiO4 ceramic scaffolds functionalized with graphene oxide (GO) sheets decorated with silver nanoparticles (AgNPs).

Chitosan/PVA reinforced boron/strontium multi-substituted hydroxyapatite-based biocomposites: Effects of synthesis pH and coating on the physicochemical, mechanical, and in vitro biological properties of scaffolds

Bioceramics are used in hard tissue applications to repair and replace damaged parts inside the human body. Hydroxyapatite (HAp) is the most widely used bioceramic due to its ability to bind to hard tissues. Furthermore, enhancing the bioactivity of HAp in hard tissue applications through co-substituted particles is of great interest. In this study, different types of HAp microparticles, including unsubstituted, boron-substituted (B-HAp), strontium-substituted (Sr-HAp), boron and strontium co-substituted HAp (B–Sr-HAp) were synthesized at pH 9 and 11 using the wet precipitation method. The impact of synthesis pH on the chemical composition and crystalline structure of the microparticles was investigated. Sintered porous three-dimensional ceramic scaffolds were prepared, polyvinyl alcohol (PVA) and chitosan (Chi) were chosen to improve the mechanical properties of the ceramic scaffolds owing to their biocompatibility and functional groups. In vitro cytotoxicity and in vitro hemocompatibility studies were conducted to evaluate the biocompatibility of the constructs. The results revealed that synthesis pH of 11 yielded the highest substitution without altering the crystalline phase. Also, the PVA/Chi coating improved the compressive strength of all scaffolds, with the most significant improvement observed in Br-HAp due to borate-diol complexation at the ceramic-polymer interface. Preliminary in vitro studies revealed that scaffolds were non-cytotoxic and hemocompatible.

Porous Three-Dimensional Polyurethane Scaffolds Promote Scar-Free Endogenous Regeneration After Acute Brain Hemorrhage.

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke and is associated with significant morbidity and mortality. Despite advances in the clinical treatment of ICH, limited progress has been made regarding endogenous brain regeneration after ICH. Failure of brain regeneration is mainly attributed to the inhibitive regenerative microenvironment caused by secondary injury after ICH. In this study, we investigated a three-dimensional biodegradable waterborne polyurethane (BWPU) scaffold as a tool to promote brain regeneration after ICH. After implantation into the cavity following hematoma evacuation, these implanted scaffolds could act as a reservoir; store a series of necrotic debris, cytokines, and chemokines; and attract microglia/macrophages to their pores. Subsequently, these microglia/macrophages were polarized into the M1-like subtype to eliminate these substances. This process disperses M1-like immune cells and prevents the formation of dense glial scar-free structures after ICH. Inflammatory cells in scaffolds include scar-free secreted growth factors and extracellular matrix (ECM) proteins, and further induce a M2-like immune cells enriched regeneration-predominant microenvironment to promote endogenous brain regeneration with functional recovery. In summary, in this work, we have revealed the potential and mechanism of the BWPU scaffold as a tool to promote endogenous brain tissue regeneration after ICH.

Biomimetic collagen composite matrix-hydroxyapatite scaffold induce bone regeneration in critical size cranial defects

Although biomimetic scaffolds have been constructed to repair critical-size bone defects, the creation of composite scaffolds that can mimic the anisotropy of natural bone remains a major challenge. Herein, we have for the first time developed a biomimetic collagen composite matrix-hydroxyapatite (CCMH) scaffold, which highly resembles both the composition and the anisotropy hierarchical structure of natural bone. The CCMH scaffold was created through unidirectional freeze-casting and in situ peristaltic mineralization, resulting in uniformly distributed nano-hydroxyapatite on the porous collagen composite matrix (CCM) scaffold. The CCMH scaffold finely mimics the composition and anisotropic channel-like morphology of native bone, which exhibits high biocompatibility, excellent cellular activity and extraordinary osteogenic differentiation capability. Magnetic resonance imaging (MRI), micro-computed tomography (micro-CT) and histological analysis of rat models demonstrated that the CCMH scaffold significantly enhanced new bone formation and accelerated bone regeneration. The innovative unidirectional freezing-in situ peristaltic mineralization approach offers a robust technique for building biomimetic three-dimensional porous scaffolds with excellent biocompatibility and osteoinductivity, which show significant promise for use in bone repair and regeneration.

Immune-microenvironment modulatory polyurethane-hyaluronic acid hybrid hydrogel scaffolds for diabetic wound treatment

The healing of wounds in diabetic patients is a huge challenge issue in clinical medicine due to the disordered immune. Recruiting endogenous cells to play a role in the early stage and timely reducing inflammation to promote healing in the middle or late of injuring are both prerequisites for effective treatment. Here, inspired by natural extracellular matrix, three-dimensional porous polyurethane-hyaluronic acid hybrid hydrogel scaffolds (PUHA) were prepared to repair diabetic wound through activate cell immunity by moderate foreign body reaction, provide cell adhesion growth extracellular matrix of hyaluronic acid (HA) and exhibit anti-inflammatory effect of polyurethane (PU). The interaction between PU and HA alters the compact PU hydrogel into macroporous PUHA hydrogel scaffolds with super-swelling, elastic mechanical properties, and controllable degradation, which are suitable for endogenous cells infiltration, growth and immune activation. Additionally, incorporating with RGD, PUHA hydrogel scaffolds with bioactive physicochemical features can evidently reduce the inflammation and modulate the polarization of macrophage apparently both in vitro and in vivo, mainly through downregulation of cytokine-cytokine receptor interaction genes, leading to reprogramming immune-microenvironment and rapid diabetic wound healing. This method of gathering cells initially and intervening immune-microenvironment in time provides an expected way to design biomaterials for chronic wound healing.

Three-Dimensional Scaffolds for Bone Tissue Engineering.

Immobilization using external or internal splints is a standard and effective procedure to treat minor skeletal fractures. In the case of major skeletal defects caused by extreme trauma, infectious diseases or tumors, the surgical implantation of a bone graft from external sources is required for a complete cure. Practical disadvantages, such as the risk of immune rejection and infection at the implant site, are high in xenografts and allografts. Currently, an autograft from the iliac crest of a patient is considered the "gold standard" method for treating large-scale skeletal defects. However, this method is not an ideal solution due to its limited availability and significant reports of morbidity in the harvest site (30%) as well as the implanted site (5-35%). Tissue-engineered bone grafts aim to create a mechanically strong, biologically viable and degradable bone graft by combining a three-dimensional porous scaffold with osteoblast or progenitor cells. The materials used for such tissue-engineered bone grafts can be broadly divided into ceramic materials (calcium phosphates) and biocompatible/bioactive synthetic polymers. This review summarizes the types of materials used to make scaffolds for cryo-preservable tissue-engineered bone grafts as well as the distinct methods adopted to create the scaffolds, including traditional scaffold fabrication methods (solvent-casting, gas-foaming, electrospinning, thermally induced phase separation) and more recent fabrication methods (fused deposition molding, stereolithography, selective laser sintering, Inkjet 3D printing, laser-assisted bioprinting and 3D bioprinting). This is followed by a short summation of the current osteochondrogenic models along with the required scaffold mechanical properties for in vivo applications. We then present a few results of the effects of freezing and thawing on the structural and mechanical integrity of PLLA scaffolds prepared by the thermally induced phase separation method and conclude this review article by summarizing the current regulatory requirements for tissue-engineered products.

Highly resilient and fatigue-resistant poly(4-methyl-ε-caprolactone) porous scaffold fabricated via thiol-yne photo-crosslinking/salt-templating for soft tissue regeneration

Elastomeric scaffolds, individually customized to mimic the structural and mechanical properties of natural tissues have been used for tissue regeneration. In this regard, polyester elastic scaffolds with tunable mechanical properties and exceptional biological properties have been reported to provide mechanical support and structural integrity for tissue repair. Herein, poly(4-methyl-ε-caprolactone) (PMCL) was first double-terminated by alkynylation (PMCL-DY) as a liquid precursor at room temperature. Subsequently, three-dimensional porous scaffolds with custom shapes were fabricated from PMCL-DY via thiol-yne photocrosslinking using a practical salt template method. By manipulating the Mn of the precursor, the modulus of compression of the scaffold was easily adjusted. As evidenced by the complete recovery from 90% compression, the rapid recovery rate of >500 mm min−1, the extremely low energy loss coefficient of <0.1, and the superior fatigue resistance, the PMCL20-DY porous scaffold was confirmed to harbor excellent elastic properties. In addition, the high resilience of the scaffold was confirmed to endow it with a minimally invasive application potential. In vitro testing revealed that the 3D porous scaffold was biocompatible with rat bone marrow stromal cells (BMSCs), inducing BMSCs to differentiate into chondrogenic cells. In addition, the elastic porous scaffold demonstrated good regenerative efficiency in a 12-week rabbit cartilage defect model. Thus, the novel polyester scaffold with adaptable mechanical properties may have extensive applications in soft tissue regeneration.

Sustained release of resveratrol from fused deposition modelling guided 3D porous scaffold for bone tissue engineering

To promote bone regeneration, bone tissue engineering necessitates development of a three-dimensional porous scaffold with osteoconductive, osteoinductive, and osteogenic features. In this study, a milliporous polylactic acid (PLA) scaffold was 3D printed, into which a microporous polycaprolactone scaffold releasing resveratrol was embedded. Herein, resveratrol-loaded albumin nanoparticles (RSV-Np) were synthesized, homogenously mixed with polycaprolactone (10% w/v & 12% w/v) at 2 different concentrations, and subsequently embedded into the milliporous PLA scaffold. Further, morphological analysis by field emission scanning electron microscopic (FESEM) analysis demonstrated interconnected pores measuring 100–300 µm diameter, and homogenous embedment of RSV-Np throughout the surface. In addition, XRD analysis inferred that resveratrol was present in an amorphous phase in the scaffold, which improves dissolution of the drug, thereby advantageous for drug delivery applications. Furthermore, successful incorporation of RSV-Np was validated by Raman spectroscopy and Fourier transform infrared spectroscopy. The drug release study implied that RSV-Np concentration modulated the resveratrol release from scaffolds. Moreover, in vitro testing of the scaffolds for 16 days showed that resveratrol sustained release enhanced the osteogenic potential of scaffolds. In summary, such scaffolds can be a potential matrix for bone regeneration due to their inherent ability to release resveratrol in a controlled fashion.

Polycaprolactone with multiscale porosity and patterned surface topography prepared using sacrificial 3D printed moulds: Towards tailor-made scaffolds

Biocompatible three-dimensional porous scaffolds are widely used in multiple biomedical applications. However, the fabrication of tailor-made 3D structures with controlled and combined multiscale macroscopic-microscopic, surface and inner porosities in a straightforward manner is still a current challenge. Herein, we use multimaterial fused deposition modeling (FDM) to generate poly (vinyl alcohol) (PVA) sacrificial moulds filled with poly (Ɛ-caprolactone) (PCL) to generate well defined PCL 3D objects. Further on, the supercritical CO2 (SCCO2) technique, as well as the breath figures mechanism (BFs), were additionally employed to fabricate specific porous structures at the core and surfaces of the 3D PCL object, respectively. The biocompatibility of the resulting multiporous 3D structures was tested in vitro and in vivo, and the versatility of the approach was assessed by generating a vertebra model fully tunable at multiple pore size levels. In sum, the combinatorial strategy to generate porous scaffolds offers unique possibilities to fabricate intricate structures by combining the advantages of additive manufacturing (AM), which provides flexibility and versatility to generate large sized 3D structures, with advantages of the SCCO2 and BFs techniques, which allow to finely tune the macro and micro porosity at material surface and material core levels.

Matrilin-2 within a three-dimensional lysine-modified chitosan porous scaffold enhances Schwann cell migration and axonal outgrowth for peripheral nerve regeneration.

Background: Matrilin-2 is a key extracellular matrix protein involved in peripheral nerve regeneration. We sought to develop a biomimetic scaffold to enhance peripheral nerve regeneration by incorporating matrilin-2 within a chitosan-derived porous scaffold. We hypothesized that the use of such a novel biomaterial delivers microenvironmental cues to facilitate Schwann cell (SC) migration and enhance axonal outgrowth during peripheral nerve regeneration. Materials and Methods: The effect of matrilin-2 on SC migration was evaluated with agarose drop migration assay on matrilin-2 coated dishes. SC adhesion was determined with SCs cultured atop tissue culture dishes coated with matrilin-2. Various formulations of chitosan vs matrilin-2 in scaffold constructs were examined with scanning electron microscopy. The effect of the matrilin-2/chitosan scaffold on SC migration in the collagen conduits was determined by capillary migration assays. Neuronal adhesion and axonal outgrowth were evaluated with three-dimensional (3D) organotypic assay of dorsal root ganglions (DRG). DRG axonal outgrowth within the scaffolds was determined by immunofluorescence staining of neurofilaments. Results: Matrilin-2 induced SC migration and enhanced its adhesion. A formulation of 2% chitosan with matrilin-2 demonstrated an optimal 3D porous architecture for SC interaction. Matrilin-2/chitosan scaffold enabled SCs to migrate against gravity within conduits. Chemical modification of chitosan with lysine (K-chitosan) further improved DRG adhesion and axonal outgrowth than the matrilin-2/chitosan scaffold without lysine modification. Conclusion: We developed a matrilin-2/K-chitosan scaffold to mimic extracellular matrix cues and provide a porous matrix to enhance peripheral nerve regeneration. Taking advantage of matrilin-2's capability to stimulate SC migration and adhesion, we formulated a porous matrilin-2/chitosan scaffold to support axongal outgrowth. Chemical modification of chitosan with lysine further improved matrilin-2 bioactivity in the 3D scaffold. The 3D porous matrilin-2/K-chitosan scaffolds have high potential for enhancing nerve repair by stimulating SC migration, neuronal adhesion, and axonal outgrowth.