Study on antibacterial properties and cytocompatibility of EPL coated 3D printed PCL/HA composite scaffolds

Biomaterial scaffolds play a critical role in bone tissue engineering. Moreover, 3D printing technology has enormous advantage in the manufacture of bioengineering scaffolds for patient-specific bone defect treatments. In order to provide an aseptic environment for bone regeneration, ε-poly-l-lysine (EPL), an antimicrobic cationic polypeptide, was used for surface modification of 3D printed polycaprolactone/hydroxyapatite (PCL/HA) scaffolds which were fabricated by fused deposition modeling (FDM) technology. The scaffold morphology and micro-structure were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transform infrared spectroscopy (FT-IR). The release profile surface roughness, open porosity, and mechanical properties of the scaffolds were evaluated. Cell adhesion, proliferation, differentiation potential and antibacterial properties were also examined. As a result, 3D printed PCL/HA scaffolds with interconnected pores showed a slightly rough surface and improved mechanical properties due to adding hydroxyapatite (HA) particles. After being modified by EPL, favorable biocompatibility and osteoconductivity of ε-poly-l-lysine/polycaprolactone/hydroxyapatite (EPL/PCL/HA) scaffolds were observed. Moreover, antibacterial activity of the EPL/PCL/HA scaffolds was apparent. As a consequence, the EPL/PCL/HA scaffolds had great potential for bone regeneration and prevention of infections. This would yield a patient-specific bioactive and antibacterial composite scaffold for advanced bone tissue engineering applications.

Biomaterial scaffolds play a critical role in bone tissue engineering.     

Polydopamine functionalized VEGF gene-activated 3D printed scaffolds for bone regeneration

Bone is a highly vascularized organ and the formation of new blood vessels is essential to regenerate large critical bone defects. In this study, polylactic acid (PLA) scaffolds of 20–80% infill were three-dimensionally (3D) printed using a fused deposition modeling based 3D printer. The PLA scaffolds were coated with polydopamine (PDA) and then were surface-functionalized with polyethyleneimine (PEI) and VEGF-encoding plasmid DNA (pVEGF) nanoplexes (PLA-PDA-PEI-pVEGF). The PLA-PDA-PEI-pVEGF scaffolds with 40% infill demonstrated higher encapsulation efficiency and sustained release of pVEGF than scaffolds with 20, 60 and 80% infill and were therefore used for in vitro and in vivo studies. The PLA-PDA-PEI-pVEGF increased the translation and secretion of VEGF and BMP-2. The PLA-PDA-PEI-pVEGF also yielded a 2- and 4.5-fold change in VEGF and osteocalcin gene expression in vitro, respectively. A tube formation assay using human umbilical vascular endothelial cells (HUVECs) showed a significant increase in tube length when exposed to the PLA-PDA-PEI-pVEGF scaffold, in comparison to PLA and PLA-PDA scaffolds. The PLA-PDA-PEI-pVEGF scaffold in an in vivo rat calvarial critical bone defect model demonstrated 1.6-fold higher new bone formation compared to the PLA-PDA scaffold. H&E and Masson''s trichrome staining of bone sections also revealed that the PLA-PDA-PEI-pVEGF scaffold facilitated the formation of more blood vessels in the newly formed bone compared to the PLA and PLA-PDA scaffold groups. Thus, PLA-PDA-PEI-pVEGF might be a potential 3D printed gene activated scaffold for bone regeneration in clinical situations.

Bone is a highly vascularized organ and the formation of new blood vessels is essential to regenerate large critical bone defects.     

Characterization and osteogenic evaluation of mesoporous magnesium–calcium silicate/polycaprolactone/polybutylene succinate composite scaffolds fabricated by rapid prototyping

The properties of scaffolds for bone tissue engineering, including their biocompatibility, highly interconnected porosity, and mechanical integrity, are critical for promoting cell adhesion, proliferation, and osteoinduction. We used various physical and biological assays to obtain in vitro confirmation that the proposed composite scaffolds are potentially suitable for applications to bone tissue engineering. The proposed new composite scaffolds, which we fabricated by a rapid prototyping technique, were composed of mesoporous magnesium–calcium silicate (m_MCS), polycaprolactone (PCL), and polybutylene succinate (PBSu). We systematically evaluated the characteristics of the composite scaffolds, such as the hydrophilicity and bioactivity. We also investigated the proliferation and osteogenic differentiation of human mesenchymal stem cells (MSCs) scaffolded on the m_MCS/PCL/PBSu composite. Our results showed that, compared to the m_MCS/PCL scaffold, the m_MCS/PCL/PBSu scaffold has improved water absorption, in vitro degradability, biocompatibility, and bioactivity in simulated body fluid, while its mechanical strength is reduced. Moreover, the results of the cytotoxicity tests specified in ISO 10993-12 and ISO 10993-5 clearly indicate that the m_MCS/PCL scaffold is not toxic to cells. In addition, we obtained significant increases in initial cell attachment and improvements to the osteogenic MSC differentiation by replacing the m_MCS/PCL scaffold with the m_MCS/PCL/PBSu scaffold. Our results indicate that the m_MCS/PCL/PBSu scaffold achieves enhanced bioactivity, degradability, cytocompatibility, and osteogenesis. As such, this scaffold is a potentially promising candidate for use in stem cell-based bone tissue engineering.

A new composite scaffold consisting of mesoporous magnesium–calcium silicate (m_MCS), polycaprolactone (PCL), and polybutylene succinate (PBSu) was manufactured by a rapid prototyping technique, for stem cell-based bone tissue engineering.     

3D-printed composite scaffold with anti-infection and osteogenesis potential against infected bone defects

In the field of orthopedics, an infected bone defect is a refractory disease accompanied by bone infection and defects as well as aggravated circulation. There are currently no personalized scaffolds that can treat bone infections using local stable and sustained-release antibiotics while providing mechanical support and bone induction to promote bone repair in the process of absorption in vivo. In our previous study, rifampicin/moxifloxacin-poly lactic-co-glycolic acid (PLGA) microspheres were prepared and tested for sustained release and antibacterial activity. The composite scaffold of poly-l-lactic acid (PLLA)/Pearl had a positive effect on mechanics supports and promoted osteogenesis. Therefore, in this study, the personalized scaffolds of PLLA/Pearl were first prepared by 3D printing. Then, rifampicin/moxifloxacin-PLGA (RM-P) microspheres were loaded into the scaffold pores to prepare the PLLA/Pearl/RM-P scaffolds. In this in vitro study, we investigated the structural characteristics and cytocompatibility of 3D-printed composite scaffolds, which indicates the integrity of the components in the scaffolds. The PLLA/Pearl and PLLA/Pearl/RM-P composite scaffolds can promote adhesion, proliferation, and differentiation of human bone marrow mesenchymal stem cells. Moreover, a rabbit model of infected bone defects of the radius was established. PLLA, PLLA/Pearl, and PLLA/Pearl/RM-P scaffolds were implanted into the bone nidus. The therapeutic effect of the three scaffolds on the infected bone defects was evaluated through imaging and microbiological and histological analysis after surgery. Among the three scaffolds, only the PLLA/Pearl/RM-P scaffold had anti-infection and bone defect repair in vivo. 3D printing provides support for personalized scaffold structures, and composite materials ensure that the scaffolds exert anti-infection and bone repair effects. Our study suggests that the PLLA/Pearl/RM-P scaffold is a promising new material in the clinical treatment of infected bone defects.

Indication the mechanism of dual-functional scaffold in the treatment of infected bone defects.     

Bone regeneration in critically sized rat mandible defects through the endochondral pathway using hydroxyapatite-coated 3D-printed Ti6Al4V scaffolds

The endochondral approach has been proved to be a promising pathway in bone tissue engineering. However, whether it is suitable for repairing critically sized mandible defects is unknown. We designed Ti₆Al₄V scaffolds with a suitable shape and pore size by a 3D-printing selective-laser-melting technique to implement this approach. In order to improve the surface bioactivity of the scaffolds, hydroxyapatite (HA) coatings (HA/L group and HA/H group) of different crystallite size were prepared on the scaffolds via electrochemical deposition. Rat bone mesenchymal stem cells (BMSCs) were seeded onto the scaffolds and chondrogenically differentiated in vitro for 4 weeks and then the scaffolds were implanted into critically sized rat mandible defects for 8 weeks. The bare scaffold and HA coatings were characterized with field emission scanning electron microscopy, water contact angle measurements and X-ray diffractometry. Cell proliferation results showed that the bioactivity of the HA coatings could better improve the growth rate of BMSCs compared with the bare surface. Additionally, safranin O staining showed abundant cartilage matrix and chondrocytes in the HA coated scaffold. Analyses using qPCR detected higher expression of chondrogenic-related gene Col2α1 and vegfα in the HA coated groups, especially in the HA/H group. Together these data demonstrate that the HA coating could improve the chondrogenic differentiation of BMSCs. In vivo, methylene blue staining of histological sections and micro-computed tomography revealed that the HA-coated groups, especially the HA/H group, increased new bone formation via endochondral ossification compared with the control group. Therefore, this strategy provides an alternative method to improve bone formation in mandible defects via the endochondral pathway and the scaffold with larger HA crystals was superior to those with smaller HA crystals.

Bone regeneration in critically sized rat mandible defects through the endochondral pathway using hydroxyapatite-coated scaffolds.     

Recombinant human BMP-7 grafted poly(lactide-co-glycolide)/hydroxyapatite scaffolds via polydopamine for enhanced calvarial repair

Poly(lactic-co-glycolic acid) (PLGA) and hydroxyapatite (HA) are considered potential osteoinductive materials because of their biodegradability and mineralization features. However, the hydrophobicity of scaffold surfaces is less supportive of cell attachment and proliferation because of poor wettability. The mode of binding of growth factors to the scaffold also affects cell differentiation into osteoblasts. The half-life of a growth factor in vivo can be increased by binding the factor to the scaffold surface. In this work, we prepared a porous PLGA/HA scaffold grafted with recombinant human bone morphogenic protein-7 (rhBMP-7) attached via polydopamine (pDA) for bone repair. The pDA coated PLGA/HA (pDA-PLGA/HA) scaffolds were characterized by energy dispersive X-ray analysis and Fourier-transform infrared spectroscopy. The microstructure and porosity of PLGA/HA scaffolds were analyzed by scanning electron microscopy and micro-computed tomography. The release profile of rhBMP-7 grafted onto the pDA-PLGA/HA (pDA-PLGA/HA/BMP-7) scaffolds was examined for 21 days. The attachment efficiency, cell proliferation rate, alkaline phosphatase activity, calcium deposition, and osteoblast-related gene expression of bone marrow-derived stem cells to PLGA/HA, pDA-PLGA/HA, and pDA-PLGA/HA/BMP-7 scaffolds were evaluated. To assess the ability of bone repair in vivo, scaffolds were implanted into critical-sized calvarial defects created in mice, and the in vivo tissue-engineered bone was monitored by micro-computed tomography and histology. In vivo experiments revealed rapid healing of the defects treated with the pDA-PLGA/HA/BMP-7 scaffolds compared with pDA-PLGA/HA and PLGA/HA scaffolds at week 8 post-surgery. These results collectively demonstrate that the rhBMP-7-immobilized PLGA/HA scaffold via pDA is a promising candidate for calvarial repair.

Polydopamine-assisted rhBMP-7 immobilization on PLGA/hydroxyapatite scaffold via phase inversion for enhanced calvarial repair in vivo.     

Fabrication and functionalization of 3D-printed soft and hard scaffolds with growth factors for enhanced bioactivity

Strategies to improve the acceptance of scaffolds by the body is crucial in tissue engineering (TE) which requires tailoring of the pore structure, mechanical properties and surface characteristics of the scaffolds. In the current study we used a 3-dimensional (3D) printing technique to tailor the pore structure and mechanical properties of (i) nanocellulose based hydrogel scaffolds for soft tissue engineering and (ii) poly lactic acid (PLA) based scaffolds for hard tissue engineering in combination with surface treatment by protein conjugation for tuning the scaffold bioactivity. Dopamine coating of the scaffolds enhanced the hydrophilicity and their capability to bind bioactive molecules such as fibroblast growth factor (FGF-18) for soft TE scaffolds and arginyl glycyl aspartic acid (RGD) peptide for hard TE scaffolds, which was confirmed using MALDI-TOFs. This functionalization approach enhanced the performance of the scaffolds and provided antimicrobial activity indicating that these scaffolds can be used for cartilage or bone regeneration applications. Blood compatibility studies revealed that both the materials were compatible with human red blood cells. Significant enhancement of cell attachment and proliferation confirmed the bioactivity of growth factor functionalized 3D printed soft and hard tissues. This approach of combining 3D printing with biological tuning of the interface is expected to significantly advance the development of biomedical materials related to soft and hard tissue engineering.

3D printed scaffolds with tailored bioactivity using protein conjugation.     

Effects of vitamin D3 release from 3D printed calcium phosphate scaffolds on osteoblast and osteoclast cell proliferation for bone tissue engineering

Vitamin D₃ is a hydrophobic micronutrient and is known for inhibiting osteoclastic bone resorption in vivo via suppression of the Receptor Activator of Nuclear factor-Kappa B (RANK ligand) expression in osteoblasts. Although vitamin D is well-known for its promotion in bone health, little is known on its effects directly on bone cells. The objective of this study was to understand the effects of vitamin D₃ release from 3D printed calcium phosphate scaffolds towards bone cell proliferation. In this study, cholecalciferol, a common intake form of vitamin D₃, was successfully able to release from the scaffold matrix via the use of polyethylene glycol. Results showed a decrease in osteoclast resorption pits and healthier osteoblast cellular morphology compared to the control. Additively manufactured tricalcium phosphate scaffolds with designed porosity were loaded with vitamin D₃ and showed controlled release profiles in phosphate buffer and acetate buffer solutions. The release kinetics of vitamin D₃ from calcium phosphate scaffolds enabling osteoblast proliferation and inhibiting osteoclastic resorption can enhance healing for low load bearing applications for bone defects or permeate voids left by tumor resection.

Release of Vitamin D₃, cholecalciferol, from 3D printed calcium phosphate scaffolds showed reduced osteoclast resorption activity.     

Strontium ranelate-loaded POFC/β-TCP porous scaffolds for osteoporotic bone repair

It is of considerable significance to fabricate scaffolds with satisfactory osteogenic activities and high osteogenesis quality to accelerate osteoporotic repair. In this study, we initially fabricated the POFC/β-TCP porous scaffold in the light of composition and structure bionics, and then loaded the SR to the optimized POFC/β-TCP porous scaffold by 3D printing based on FFS-MDJ. The hydrophilicity, mechanical properties biodegradability and cell response of the composite scaffolds were systematically investigated. The result showed that modified POFC enhanced the hydrophilicity and ameliorated the brittleness of pure β-TCP. β-TCP buffered the acidity and improved the degradability and cell affinity of the scaffold, and the release of strontium ranelate significantly promote the proliferation and differentiation of osteoblasts and guided bone regeneration. The results indicated that POFC/β-TCP scaffolds had uniform macropores of 300–500 μm and a porosity of approximately 48%, adjustable biodegradability and a high compressive modulus of 30–60 MPa. The strontium ranelate-loaded POFC/β-TCP scaffold enhanced the osteogenic differentiation of rBMSCs, which might be a promising candidate for osteoporotic-related bone defect repair.

It is of considerable significance to fabricate scaffolds with satisfactory osteogenic activities and high osteogenesis quality to accelerate osteoporotic repair.     

A three-dimensional hydroxyapatite/polyacrylonitrile composite scaffold designed for bone tissue engineering

In recent years, various composite scaffolds based on hydroxyapatite have been developed for bone tissue engineering. However, the poor cell survival micro-environment is still the major problem limiting their practical applications in bone repairing and regeneration. In this study, we fabricated a class of fluffy and porous three-dimensional composite fibrous scaffolds consisting of hydroxyapatite and polyacrylonitrile by employing an improved electrospinning technique combined with a bio-mineralization process. The fluffy structure of the hydroxyapatite/polyacrylonitrile composite scaffold ensured the cells would enter the interior of the scaffold and achieve a three-dimensional cell culture. Bone marrow mesenchymal stem cells were seeded into the scaffolds and cultured for 21 days in vitro to evaluate the response of cellular morphology and biochemical activities. The results indicated that the bone marrow mesenchymal stem cells showed higher degrees of growth, osteogenic differentiation and mineralization than those cultured on the two-dimensional hydroxyapatite/polyacrylonitrile composite membranes. The obtained results strongly supported the fact that the novel three-dimensional fluffy hydroxyapatite/polyacrylonitrile composite scaffold had potential application in the field of bone tissue engineering.

A fluffy and porous (3D) HA composite fibrous scaffold was fabricated by employing an improved electrospinning technique combined with a bio-mineralization process.     

Fabrication of fibrillated and interconnected porous poly(ε-caprolactone) vascular tissue engineering scaffolds by microcellular foaming and polymer leaching

This paper provides a method combining eco-friendly supercritical CO₂ microcellular foaming and polymer leaching to fabricate small-diameter vascular tissue engineering scaffolds. The relationship between pore morphology and mechanical properties, and the cytocompatibility, are investigated with respect to the effects of poly(ε-caprolactone)/poly(ethylene oxide) (PCL/PEO) phase morphologies and PEO leaching. When PEO content increases, the pore size decreases and the pore density increases. After the leaching process, highly interconnected and fibrillated porous structures are detected in the foamed PCL70 blend with droplet-matrix morphologies. Moreover, the leaching process had a greater contribution to improve the open-cell content in the PCL50 blend, which has a co-continuous morphology and easily obtained open-cell content of more than 80%. Small-diameter tubular PCL70 and PCL50 porous scaffolds with an average pore size of 48 ± 1.4 μm and 30 ± 1.0 μm respectively, are fabricated successfully. Prominent orientated pores are found in the PCL70 scaffold, and a mixed microstructure combining interconnected channels and open cells occurs in PCL50 scaffold. The PCL70 scaffold has a greater longitudinal tensile strength, longer toe region, and larger cyclical recoverability. HUVECs tend to align along the direction of the pore orientation in the PCL70 scaffold, whereas HUVECs have a higher density and spreading area in the PCL50 scaffold. The results gathered in this paper may provide a theoretical basis and data support for fabricating small-diameter porous tissue engineering vascular scaffolds.

This paper provides a method combining eco-friendly supercritical CO₂ microcellular foaming and polymer leaching to fabricate small-diameter vascular tissue engineering scaffolds.     

Sodium alginate/collagen composite multiscale porous scaffolds containing poly(ε-caprolactone) microspheres fabricated based on additive manufacturing technology

Biocompatible porous scaffolds with adjustable pore structures, appropriate mechanical properties and drug loading properties are important components of bone tissue engineering. In this work, biocompatible sodium alginate (SA)/collagen (Col) multiscale porous scaffolds containing poly(ε-caprolactone) microspheres (Ms-PCL) have been facilely fabricated based on 3D extrusion printing of the pre-crosslinked composite hydrogels. The prepared composite hydrogels can be 3D extrusion printed into porous scaffolds with different designed shapes and adjustable pore structures. The hydroxyapatite (HAP) nanoparticles have been added into the SA/Col hydrogels to achieve stress dispersion and form double crosslinking networks. SA-Ca²⁺ crosslinking networks and Col–genipin (GP) crosslinking networks have been constructed to improve the mechanical properties of the scaffolds (about 2557 kPa of compressive stress at 70% strain), and reduce the swelling rate and degradation rate of SA/Col scaffolds. Moreover, the SA/Col hydrogels contain hydrophobic antibacterial drug enrofloxacin loaded Ms-PCL, and in vitro drug release research shows a sustained-release function of porous scaffolds, indicating the potential application of SA/Col porous scaffolds as drug carriers. In addition, the antibacterial experiments show that the composite scaffolds display a distinguished and long-term antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, mouse bone mesenchymal stem cells (mBMSCs) are seeded on the SA/Col composite scaffolds, and an in vitro biocompatibility experiment shows that the mBMSCs can adhere well on the composite scaffolds, which indicate that the fabricated composite scaffolds are biocompatible. In short, all of the above results suggest that the biocompatible SA/Col composite porous scaffolds have enormous application and potential in bone tissue engineering.

Biocompatible porous scaffolds with adjustable pore structures, appropriate mechanical properties and drug loading properties are important components of bone tissue engineering.     

β-Carotene: a natural osteogen to fabricate osteoinductive electrospun scaffolds

β-Carotene (βC) as a natural osteogenic material was incorporated in PCL electrospun mats to fabricate scaffolds for bone tissue engineering. These scaffolds successfully supported the attachment and proliferation of mesenchymal stem cells (MSCs). Seeded scaffolds were calcinated during 21 days of cell culture in a non-differential medium, which showed the osteodifferentiation of MSCs. Expression of RUNX2, SOX9, and osteonectin proved the osteoinductive effect of incorporated β-carotene on the differentiation of MSCs to osteoblasts without using any external osteogenic differential agent. However, the cells did not pass the early phase of osteogenesis and were still osteochondro-progenitor after 21 days of incubation. Thus, the fabricated fibrous scaffolds are potential candidates for direct bone tissue engineering.

Electrospun PCL scaffolds containing β-carotene as a natural osteogenic material can differentiate MSCs to osteoblasts without using external differential agents.     

Chitosan-vancomycin hydrogel incorporated bone repair scaffold based on staggered orthogonal structure: a viable dually controlled drug delivery system

In clinical practice, challenges remain in the treatment of large infected bone defects. Bone tissue engineering scaffolds with good mechanical properties and antibiotic-controlled release are powerful strategies for infection treatment. In this study, we prepared polylactic acid (PLA)/nano-hydroxyapatite (nHA) scaffolds with vertical orthogonal and staggered orthogonal structures by applying 3D printing technology. In addition, vancomycin (Van)-based chitosan (CS) hydrogel (Gel@Van) was loaded on the scaffold (PLA/nHA/CS-Van) to form a local antibiotic release system. The microstructure of the composite scaffold had high porosity with interconnected three-dimensional networks. The mechanical properties of the PLA/nHA/CS-Van composite scaffold were enhanced by the addition of CS-Van. The results of the water contact angle analysis showed that the hydrophilicity of the drug-loaded scaffold improved. In addition, the composite scaffold could produce sustained release in vitro for more than 8 weeks without adverse effects on the proliferation and differentiation of mouse embryonic osteoblasts (MC3T3-E1), which confirmed its good biocompatibility. During the in vitro antimicrobial study, the composite scaffold effectively inhibited the growth of Staphylococcus aureus (S. aureus). Therefore, our results suggest that the PLA/nHA/CS-Van composite scaffold is a promising strategy for treating infected bone defects.

The schematic diagram of preparing the composite scaffolds.     

Synergistic delivery of bFGF and BMP-2 from poly(l-lactic-co-glycolic acid)/graphene oxide/hydroxyapatite nanofibre scaffolds for bone tissue engineering applications

One of the goals of bone tissue engineering is to create scaffolds with excellent biocompatibility, osteoinductive ability and mechanical properties. The application of bioactive proteins, such as bone morphogenetic protein (BMP)-2 and basic fibroblast growth factor (bFGF), has been showed to be an effective way to improve the osteoinductivity and biocompatibility of bone scaffold materials. Therefore, the development of novel materials capable of delivering multiple growth factors is urgent and essential for bone defect repair. In this study, a composite nanofibre scaffold composed of poly(l-lactic-co-glycolic acid) (PLGA), hydroxyapatite (HA), and graphene oxide (GO) has been fabricated to deliver basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) simultaneously. The data show that the incorporation of GO and HA into PLGA nanofibres significantly improved the mechanical properties and hydrophilicity of the nanofibre scaffolds. More importantly, compared to PLGA and PLGA/HA nanofibre scaffolds, the PLGA/HA/GO nanofibre scaffolds could more efficiently immobilize bFGF and BMP-2. Moreover, biological assays indicated that the loaded bFGF and BMP-2 loaded in the composite nanofibre scaffolds have a synergistic differentiation effect on the cell adhesion, proliferation, and osteogenesis differentiation of MC3T3-E1 cells. In contrast to the PLGA/HA/GO/bFGF and PLGA/HA/GO/BMP-2 nanofibre scaffolds, the PLGA/HA/GO/bFGF/BMP-2 scaffolds have shown higher ALP activity and higher expression levels of osteogenesis-related genes. In summary, our findings indicated that the incorporation of GO into nanofibre scaffolds is an effective method to immobilize growth factors onto biomaterial surfaces, and the synergistic effects of a combination of BMP-2 and bFGF may have potential use in bone regenerative therapeutics.

One of the goals of bone tissue engineering is to create scaffolds with excellent biocompatibility, osteoinductive ability and mechanical properties.     

An electrospun poly(ε-caprolactone) nanocomposite fibrous mat with a high content of hydroxyapatite to promote cell infiltration

Electrospun polymer/inorganic biomimetic nanocomposite scaffolds have emerged for use in a new strategy for bone regeneration. In this study, a poly(ε-caprolactone) (PCL)/hydroxyapatite (HAp) nanocomposite mat with a HAp content as high as 60% was prepared via one-step electrospinning using trifluoroethanol as the solvent, and it has superior dispersibility and spinnability. The structure and physicochemical properties of the scaffolds were studied using scanning electron microscopy and spectroscopic techniques. X-ray diffraction and Fourier transformed infrared spectroscopy confirmed the presence of HAp in the composite PCL fibers. The results of cell culturing suggested that the incorporation of HAp with PCL could regulate the cytoskeleton and the differentiation of cells. More interestingly, the high content of HAp was also found to be conducive to the infiltration of MC-3T3 cells into the mat. The results indicated the potential of PCL/HAp scaffolds as a promising substitute for bone regeneration.

PCL nanofibers with 60% HAp content were fabricated, and the presence of HAp regulated cell morphology to enhance cell infiltration.     

Gelatin-assisted conglutination of aligned polycaprolactone nanofilms into a multilayered fibre-guiding scaffold for periodontal ligament regeneration

The repair or regeneration of well-aligned periodontal ligaments (PDL) remains a challenging clinical task in reconstructive surgeries and regenerative medicine. Topographical cell guidance has been utilized as a tissue-engineering bionic technique and facilitates the geometric design of composite materials. In this investigation, we manufactured multilayered scaffolds by cementing aligned polycaprolactone (PCL) electrospun films together using gelatin; the fibre-guiding scaffold mimicked the natural structure of periodontal ligaments and was aimed at promoting the growth of functionally oriented ligamentous fibres in vivo. Experiments in vitro demonstrated that this scaffold could provide good attachment and tissue-mimicking microenvironments for “seeding cells”, that is, human periodontal ligament mesenchyme cells (PDLSCs). Histological and immunofluorescence results indicated that a three-dimensional aligned construct could significantly enhance the angulation of new-born PDL-like tissue and facilitate collagen formation and maturation at periodontal fenestration defects compared to an amorphous PCL embedded scaffold. Multilayered fibre-guiding scaffold made of PCL and gelatin was demonstrated to be applicable for oriented neogenesis of periodontium, and it may represent an important potential application for dental stem cell delivery for periodontal regenerative medicine.

The 3D-AL scaffold mimics the physiological structure of periodontal ligaments and could enhance the angulation of regenerated PDL.     

The facile synthesis and bioactivity of a 3D nanofibrous bioglass scaffold using an amino-modified bacterial cellulose template

Porous bioglass (BG) scaffolds are of great importance in tissue engineering because of their excellent osteogenic properties for bone regeneration. Herein, we reported for the first time the use of amino-modified bacterial cellulose (NBC) as a template to prepare a three-dimensional (3D) nanofibrous BG scaffold by a facile modified sol–gel approach under ultrasonic treatment. The results suggested that the amino groups on the BC template could effectively promote the absorption of the deposited CaO and SiO₂ precursors, and the as-obtained BG scaffold showed a 3D interconnected porous network structure consisting of nanofibers with a diameter of about 20 nm. Furthermore, the as-obtained BG scaffold showed very good bioactivity after being immersed in SBF for 7 days. This research provides a facile and efficient way to prepare a nanofibrous BG scaffold with 3D porous structure, which can be used as a promising candidate for biomedical applications.

A nanofibrous BG scaffold with a high quality 3D porous interconnected structure has been prepared via a facile modified sol–gel approach using amino-modified bacterial cellulose as the template.     

The enhanced osteogenesis and osteointegration of 3-DP PCL scaffolds via structural and functional optimization using collagen networks

Optimal balance between biological activity and mechanical stability should be meticulously considered during scaffold design for bone tissue engineering applications. To fabricate an individualized construct with biomechanical and biological functionality for bone tissue regeneration, a polycaprolactone–collagen (PCL–COL) composite construct was developed through the combination of three-dimensional printing (3-DP) technology and biomimetic collagen matrix incorporation, with a 3-DP PCL framework maintaining the mechanical stability and a porous collagen matrix improving the biological activity. The results indicate that the compressive modulus of the composite constructs increased synergistically (over 40 MPa), providing sufficient mechanical support during new bone formation. On the other hand, the collagen matrix with a micro-porous architecture structurally increased scaffold areas and provided cellular adhesion sites, allowing for the functional construction of a favorable 3D microenvironment for BMSC adhesion, proliferation and extracellular matrix production. Moreover, critical-sized long bone defect (CSD) implantation demonstrated that the optimized composite constructs could promote bone tissue regeneration (5.5-fold) and bone-material osteointegration (4.7-fold), and decrease fibrosis encapsulation, compared to pristine PCL. The results indicate that these biomimetically ornamented PCL–COL constructs exhibit favorable mechanical properties and biological functionality, demonstrating great potential as an effective bone graft substitute for bone defect treatment. Meanwhile, they can also harness the advantages of 3-DP technology and a collagen-based functionalized strategy, facilitating the creation of customized and functional PCL–COL constructs for clinical translation.

Optimal balance between biological activity and mechanical stability should be meticulously considered during scaffold design for bone tissue engineering applications.     

Effect of low-temperature plasma treatment of electrospun polycaprolactone fibrous scaffolds on calcium carbonate mineralisation

This article reports on a study of the mineralisation behaviour of CaCO₃ deposited on electrospun poly(ε-caprolactone) (PCL) scaffolds preliminarily treated with low-temperature plasma. This work was aimed at developing an approach that improves the wettability and permeability of PCL scaffolds in order to obtain a superior composite coated with highly porous CaCO₃, which is a prerequisite for biomedical scaffolds used for drug delivery. Since PCL is a synthetic polymer that lacks functional groups, plasma processing of PCL scaffolds in O₂, NH₃, and Ar atmospheres enables introduction of highly reactive chemical groups, which influence the interaction between organic and inorganic phases and govern the nucleation, crystal growth, particle morphology, and phase composition of the CaCO₃ coating. Our studies showed that the plasma treatment induced the formation of O- and N-containing polar functional groups on the scaffold surface, which caused an increase in the PCL surface hydrophilicity. Mineralisation of the PCL scaffolds was performed by inducing precipitation of CaCO₃ particles on the surface of polymer fibres from a mixture of CaCl₂- and Na₂CO₃-saturated solutions. The presence of highly porous vaterite and nonporous calcite crystal phases in the obtained coating was established. Our findings confirmed that preferential growth of the vaterite phase occurred in the O₂-plasma-treated PCL scaffold and that the coating formed on this scaffold was smoother and more homogenous than those formed on the untreated PCL scaffold and the Ar- and NH₃-plasma-treated PCL scaffolds. A more detailed three-dimensional assessment of the penetration depth of CaCO₃ into the PCL scaffold was performed by high-resolution micro-computed tomography. The assessment revealed that O₂-plasma treatment of the PCL scaffold caused CaCO₃ to nucleate and precipitate much deeper inside the porous structure. From our findings, we conclude that O₂-plasma treatment is preferable for PCL scaffold surface modification from the viewpoint of use of the PCL/CaCO₃ composite as a drug delivery platform for tissue engineering.

This article reports on a study of the mineralisation behaviour of CaCO₃ deposited on electrospun poly(ε-caprolactone) (PCL) scaffolds preliminarily treated with low-temperature plasma.