Immobilization of carboxymethyl chitosan/laponite on polycaprolactone nanofibers as osteoinductive bone scaffolds

Decellularized extracellular matrix coupled with polycaprolactone/laponite to construct a biomimetic barrier membrane for bone defect repair

Barrier membranes play a prominent role in guided bone regeneration (GBR), and polycaprolactone (PCL) is an attractive biomaterial for the fabrication of barrier membranes. However, these nanofiber membranes (NFMs) require modification to improve their biological activity. PCL-NFMs incorporating with laponite (LAP) achieve biofunctional modification. Decellularized extracellular matrix (dECM) could modulate cell behaviour. The present study combined dECM with PCL/LAP-NFMs to generate a promising strategy for bone tissue regeneration. Bone marrow mesenchymal stem cells (BMSCs) were cultured on NFMs and deposited with an abundant extracellular matrix (ECM), which was subsequently decellularized to obtain dECM-modified PCL/LAP-NFMs (PCL/LAP-dECM-NFMs). The biological functions of the membranes were evaluated by reseeding MC3T3-E1 cells in vitro and transplanting them into rat calvarial defects in vivo. These results indicate that PCL/LAP-dECM-NFMs were successfully constructed. The presence of dECM slightly improved the mechanical properties of the NFMs, which exhibited a Young's modulus of 0.269 MPa, ultimate tensile strength of 2.04 MPa and elongation at break of 51.62 %. In vitro, the PCL/LAP-dECM-NFMs had favourable cytocompatibility, and the enhanced hydrophilicity was conducive to cell adhesion, proliferation, and osteoblast differentiation. PCL/LAP-dECM-NFMs exhibited an excellent bone repair capacity in vivo. Overall, dECM-modified PCL/LAP-NFMs should be promising biomimetic barrier membranes for GBR.

Design of chemobrionic and biochemobrionic scaffolds for bone tissue engineering

Chemobrionic systems have attracted great attention in material science for development of novel biomimetic materials. This study aims to design a new bioactive material by integrating biosilica into chemobrionic structure, which will be called biochemobrionic, and to comparatively investigate the use of both chemobrionic and biochemobrionic materials as bone scaffolds. Biosilica, isolated from Amphora sp. diatom, was integrated into chemobrionic structure, and a comprehensive set of analysis was conducted to evaluate their morphological, chemical, mechanical, thermal, and biodegradation properties. Then, the effects of both scaffolds on cell biocompatibility and osteogenic differentiation capacity were assessed. Cells attached to the scaffolds, spread out, and covered the entire surface, indicating the absence of cytotoxicity. Biochemobrionic scaffold exhibited a higher level of mineralization and bone formation than the chemobrionic structure due to the osteogenic activity of biosilica. These results present a comprehensive and pioneering understanding of the potential of (bio)chemobrionics for bone regeneration.

Carboxymethyl Chitosan-Functionalized Polyaniline/Polyacrylonitrile Nano-Fibers for Neural Differentiation of Mesenchymal Stem Cells

Electroconductive scaffolds based on polyaniline (PANi)/polyacrylonitrile (PAN) were fabricated and surface-functionalized by carboxymethyl chitosan (CMC) as efficient scaffolds for nerve tissue regeneration. The results of scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, and water contact angle measurement approved the successful fabrication of CMC-functionalized PANi/PAN-based scaffolds. Human adipose-derived mesenchymal stem cells (hADMSCs) were cultured on the scaffolds for 10 d in the presence or absence of β-carotene (βC, 20 µM) as a natural neural differentiation agent. The MTT and SEM results confirmed the attachment and proliferation of hADMSCs on the scaffolds. The expression of MAP2 at the mRNA and protein levels showed the synergic neurogenic induction effect of CMC-functionalization and βC for hADMSCs on the scaffolds. The CMC-functionalized nanofibrous PANi/PAN-based scaffolds are potential candidates for nerve tissue engineering.

Chemical Immobilization of Carboxymethyl Chitosan on Polycaprolactone Nanofibers as Osteochondral Scaffolds

Carboxymethyl chitosan (CMC) as a bio-based osteochondral inductive material was chemically immobilized on the surface of polycaprolactone (PCL) nanofibers to fabricate scaffolds for osteochondral tissue engineering applications. The chemical immobilization process included the aminolysis of ester bonds and bonding of the primary amines with glutaraldehyde as a coupling agent. The SEM and FTIR results confirmed the successfulness of the CMC immobilization. The fabricated scaffolds presented cell viabilities of > 82% and supported the attachment and proliferation of the human bone marrow mesenchymal stem cells (hBM-MSCs). The CMC-immobilized scaffolds concentration dependently induced the diverse osteochondral differentiation pathways for the hBM-MSCs without using any external differential agents. According to the Alcian Blue and Alizarin Red staining and immunocytochemistry results, scaffolds with a higher content of CMC presented more chondro-inductivity and less osteoinductivity. Thus, the CMC-immobilized scaffolds can be employed as great potential candidates for osteochondral tissue engineering applications.

3D printed macroporous scaffolds of PCL and inulin-g-P(D,L)LA for bone tissue engineering applications

Bone repair and tissue-engineering (BTE) approaches require novel biomaterials to produce scaffolds with required structural and biological characteristics and enhanced performances with respect to those currently available. In this study, PCL/INU-PLA hybrid biomaterial was prepared by blending of the aliphatic polyester poly(ε-caprolactone) (PCL) with the amphiphilic graft copolymer Inulin-g-poly(D,L)lactide (INU-PLA) synthetized from biodegradable inulin (INU) and poly(lactic acid) (PLA). The hybrid material was suitable to be processed using fused filament fabrication 3D printing (FFF-3DP) technique rendering macroporous scaffolds. PCL and INU-PLA were firstly blended as thin films through solvent-casting method, and then extruded by hot melt extrusion (HME) in form of filaments processable by FFF-3DP. The physicochemical characterization of the hybrid new material showed high homogeneity, improved surface wettability/hydrophilicity as compared to PCL alone, and right thermal properties for FFF process. The 3D printed scaffolds exhibited dimensional and structural parameters very close to those of the digital model, and mechanical performances compatible with the human trabecular bone. In addition, in comparison to PCL, hybrid scaffolds showed an enhancement of surface properties, swelling ability, and in vitro biodegradation rate. In vitro biocompatibility screening through hemolysis assay, LDH cytotoxicity test on human fibroblasts, CCK-8 cell viability, and osteogenic activity (ALP evaluation) assays on human mesenchymal stem cells showed favorable results.

Multilayer functional bionic fabricated polycaprolactone based fibrous membranes for osteochondral integrated repair

Osteochondral defect repair is one of the challenging problems in orthopedics. In this study, a multilayer polycaprolactone (PCL) based fibrous membrane for osteochondral defect repair was biomimetically fabricated by combining self-induced crystallization, biomimetic mineralization and layer-by-layer electrospinning techniques. The multilayer functional bionic fibrous membrane consisted of cartilage repair layer, intermediate transition repair layer and subchondral bone repair layer. Glucosamine hydrochloride (GAH) encapsulated in core-shell structured PCL fibrous membrane (MGPCL) was suitable for cartilage repair. Shish-kebab (SK) structured PCL fibrous membrane with calcium phosphate coating (MSKPCL) was designed for subchondral bone repair. SK structured MGPCL fibrous membrane (SKMGPCL) was used as intermediate transition repair. The tensile modulus of MG/SKMG/MSKPCL fibrous membrane was 34.24 ± 2.39 MPa which met the requirements of cartilage and subchondral bone repair scaffolds, and in vitro culture results showed that MG/SKMG/MSKPCL fibrous membrane had good biological activity and osteogenic ability. These results showed that MG/SKMG/MSKPCL fibrous membrane provides a promising material basis for osteochondral integrated repair scaffold.

A critical review on polydopamine surface-modified scaffolds in musculoskeletal regeneration

Increasing concern about age-related diseases, particularly musculoskeletal injuries and orthopedic conditions, highlights the need for strategies such as tissue engineering to address them. Surface modification has been developed to create pro-healing interfaces, personalize scaffolds and provide novel medicines. Polydopamine, a mussel-inspired adhesive polymer with highly reactive functional groups that adhere to nearly all substrates, has gained attention in surface modification strategies for biomaterials. Polydopamine was primarily developed to modify surfaces, but its effectiveness has opened up promising approaches for further applications in bioengineering as carriers and nanoparticles. This review focuses on the recent discoveries of the role of polydopamine as a surface coating material, with focus on the properties that make it suitable for tackling musculoskeletal disorders. We report the evolution of using it in research, and discuss papers involving the progress of this field. The current research on the role of polydopamine in bone, cartilage, muscle, nerve, and tendon regeneration is discussed, thus giving comprehensive overview about the function of polydopamine both in-vitro and in-vivo. Finally, the report concludes presenting the critical challenges that must be addressed for the clinical translation of this biomaterial while exploring future perspectives and research opportunities in this area.

Green Chemistry for Biomimetic Materials: Synthesis and Electrospinning of High-Molecular-Weight Polycarbonate-Based Nonisocyanate Polyurethanes

Conventional synthesis routes for thermoplastic polyurethanes (TPUs) still require the use of isocyanates and tin-based catalysts, which pose considerable safety and environmental hazards. To reduce both the ecological footprint and human health dangers for nonwoven TPU scaffolds, it is key to establish a green synthesis route, which eliminates the use of these toxic compounds and results in biocompatible TPUs with facile processability. In this study, we developed high-molecular-weight nonisocyanate polyurethanes (NIPUs) through transurethanization of 1,6-hexanedicarbamate with polycarbonate diols (PCDLs). Various molecular weights of PCDL were employed to maximize the molecular weight of NIPUs and consequently facilitate their electrospinnability. The synthesized NIPUs were characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, gel permeation chromatography, and differential scanning calorimetry. The highest achieved molecular weight (M _w) was 58,600 g/mol. The NIPUs were consecutively electrospun into fibrous scaffolds with fiber diameters in the submicron range, as shown by scanning electron microscopy (SEM). To assess the suitability of electrospun NIPU mats as a possible biomimetic load-bearing pericardial substitute in cardiac tissue engineering, their cytotoxicity was investigated in vitro using primary human fibroblasts and a human epithelial cell line. The bare NIPU mats did not need further biofunctionalization to enhance cell adhesion, as it was not outperformed by collagen-functionalized NIPU mats and hence showed that the NIPU mats possess a great potential for use in biomimetic scaffolds.

The effects of process parameters on polydopamine coatings employed in tissue engineering applications

The biomaterials’ success within the tissue engineering field is hinged on the capability to regulate tissue and cell responses, comprising cellular adhesion, as well as repair and immune processes’ induction. In an attempt to enhance and fulfill these biomaterials’ functions, scholars have been inspired by nature; in this regard, surface modification via coating the biomaterials with polydopamine is one of the most successful inspirations endowing the biomaterials with surface adhesive properties. By employing this approach, favorable results have been achieved in various tissue engineering-related experiments, a significant one of which is the more rapid cellular growth observed on the polydopamine-coated substrates compared to the untreated ones; nonetheless, some considerations regarding polydopamine-coated surfaces should be taken into account to control the ultimate outcomes. In this mini-review, the importance of coatings in the tissue engineering field, the different types of surfaces requiring coatings, the significance of polydopamine coatings, critical factors affecting the result of the coating procedure, and recent investigations concerning applications of polydopamine-coated biomaterials in tissue engineering are thoroughly discussed.

Enhanced osteogenic differentiation of stem cells by 3D printed PCL scaffolds coated with collagen and hydroxyapatite

Bone tissue engineering uses various methods and materials to find suitable scaffolds that regenerate lost bone due to disease or injury. Poly(ε-caprolactone) (PCL) can be used in 3D printing for producing biodegradable scaffolds by fused deposition modeling (FDM). However, the hydrophobic surfaces of PCL and its non-osteogenic nature reduces adhesion and cell bioactivity at the time of implantation. This work aims to enhance bone formation, osteogenic differentiation, and in vitro biocompatibility via PCL scaffolds modification with Hydroxyapatite (HA) and Collagen type I (COL). This study evaluated the osteosupportive capacity, biological behavior, and physicochemical properties of 3D-printed PCL, PCL/HA, PCL/COL, and PCL/HA/COL scaffolds. Biocompatibility and cells proliferation were investigated by seeding human adipose tissue-derived mesenchymal stem cells (hADSCs) onto the scaffolds, which were analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, and 6-diamidino-2-phenylindole (DAPI) staining. In addition, the bone differentiation potential of the hADSCs was assessed using calcium deposition, alkaline phosphatase (ALP) activity, and bone-related protein and genes. Although all constructed scaffolds support hADSCs proliferation and differentiation, the results showed that scaffold coating with HA and COL can boost these capacities in a synergistic manner. According to the findings, the tricomponent 3D-printed scaffold can be considered as a promising choice for bone tissue regeneration and rebuilding.

Laponite/amoxicillin-functionalized PLA nanofibrous as osteoinductive and antibacterial scaffolds

In this study, Amoxicillin (AMX) was loaded on laponite (LAP) nanoplates and then immobilized on the surface of electrospun polylactic acid (PLA) nanofibers to fabricate scaffolds with osteoinductive and antibacterial activities. The highest loading efficiency (49%) was obtained when the concentrations of AMX and LAP were 3 mg/mL and 1 mg/mL, respectively. FTIR and XRD spectroscopies and zeta potentiometry confirmed the successful encapsulating of AMX within LAP nanoplates. The immobilization of AMX-loaded LAPs on the surface of PLA nanofibers was verified by SEM and FTIR spectroscopy. In vitro release study showed a two-phase AMX release profile for the scaffolds; an initial burst release within the first 48 h and a later sustained release up to 21 days. In vitro antibacterial tests against Staphylococcus aureus and Escherichia coli presented the ability of scaffolds to inhibit the growth of both bacteria. The biocompatibility assays revealed the attachment and viability of human bone marrow mesenchymal stem cells (hBMSCs) cultured on the surface of scaffolds (p ≤ 0.05). The increased ALKALINE PHOSPHATASE (ALP) activity (p ≤ 0.001), calcium deposition, and expression of ALP and OSTEONECTIN genes indicated the osteoinductivity of functionalized scaffolds for hBMSCs. These LAP/AMX-functionalized scaffolds might be desirable candida for the treatment of bone defects.

Supercritical carbon dioxide dried double layer laponite XLS and alginate/polyacrylamide construct and immune response

Fabrication of immunocompatible tissue constructs for bone-cartilage defect regeneration is of prime importance. In this study, a double layer hydrogel was successfully synthesized, where alginate/polyacrylamide were formulated to represent cartilage layer (5-10 % (w/w) total polymer ratio) and laponite XLS (2-5-8% (w/w))/alginate/polyacrylamide formed bone layer. Hydrogels were dried by supercritical CO₂ at 100 and 200 bar, 45 °C, 5 g/min CO₂ flow rate for 2 h. Constructs were treated with collagen, then cellularized and embedded in cell-laden GelMA to mimic the cellular microenvironment. The optimum weight ratio of alginate/polyacrylamide:laponite XLS was 10:5 based on mechanical strength test results. The constructs yielded high porosity (91.50 m²/g) and mesoporous structure, owing to the diffusivity of CO₂ at 200 bar (0.49 × 10^-7  m²/s). Constructs were then treated with collagen to increase cell adhesion and ATDC5 cells were seeded in the cartilage layer, whereas hFOB cells to the bone layer. About 10-15 % higher cell viability was attained. The porous structure of the construct allowed infiltration of macrophages, promoted polarization and positively affected the behavior of macrophages, yielding a decrease in M1 markers, whereas an increase in M2 on day 4. The formulated tissue constructs would be of value in tissue engineering applications.

Vascularized bone regeneration accelerated by 3D-printed nanosilicate-functionalized polycaprolactone scaffold

Critical oral-maxillofacial bone defects, damaged by trauma and tumors, not only affect the physiological functions and mental health of patients but are also highly challenging to reconstruct. Personalized biomaterials customized by 3D printing technology have the potential to match oral-maxillofacial bone repair and regeneration requirements. Laponite (LAP) nanosilicates have been added to biomaterials to achieve biofunctional modification owing to their excellent biocompatibility and bioactivity. Herein, porous nanosilicate-functionalized polycaprolactone (PCL/LAP) was fabricated by 3D printing technology, and its bioactivities in bone regeneration were investigated in vitro and in vivo. In vitro experiments demonstrated that PCL/LAP exhibited good cytocompatibility and enhanced the viability of bone marrow mesenchymal stem cells (BMSCs). PCL/LAP functioned to stimulate osteogenic differentiation of BMSCs at the mRNA and protein levels and elevated angiogenic gene expression and cytokine secretion. Moreover, BMSCs cultured on PCL/LAP promoted the angiogenesis potential of endothelial cells by angiogenic cytokine secretion. Then, PCL/LAP scaffolds were implanted into the calvarial defect model. Toxicological safety of PCL/LAP was confirmed, and significant enhancement of vascularized bone formation was observed. Taken together, 3D-printed PCL/LAP scaffolds with brilliant osteogenesis to enhance bone regeneration could be envisaged as an outstanding bone substitute for a promising change in oral-maxillofacial bone defect reconstruction.

Core-Shell Nanofibers with a Shish-Kebab Structure Simulating Collagen Fibrils for Bone Tissue Engineering

The repair of bone defects is one of the great challenges facing modern orthopedics clinics. Bone tissue engineering scaffold with a nanofibrous structure similar to the original microstructure of a bone is beneficial for bone tissue regeneration. Here, a core-shell nanofibrous membrane (MS), MS containing glucosamine (MS-GLU), MS with a shish-kebab (SK) structure (SKMS), and MS-GLU with a SK structure (SKMS-GLU) were prepared by micro-sol electrospinning technology and a self-induced crystallization method. The diameter of MS nanofibers was 50-900 nm. Contact angle experiments showed that the hydrophilicity of SKMS was moderate, and its contact angle was as low as 72°. SK and GLU have a synergistic effect on cell growth. GLU in the core of MS was demonstrated to obviously promote MC3T3-E1 cell proliferation. At the same time, the SK structure grown on MS-GLU nanofibers mimicked natural collagen fibers, which facilitated MC3T3-E1 cell adhesion and differentiation. This study showed that a biomimetic SKMS-GLU nanofibrous membrane was a promising tissue engineering scaffold for bone defect repair.

Simvastatin-loaded graphene oxide embedded in polycaprolactone-polyurethane nanofibers for bone tissue engineering applications

Here, the role of simvastatin-loaded graphene oxide embedded in polyurethane-polycaprolactone nanofibers for bone tissue engineering has been investigated. The scaffolds were physicochemically and mechanically characterized, and obtained polymeric composites were used as MG-63 cell culture scaffolds. The addition of graphene oxide-simvastatin to nanofibers generates a homogeneous and uniform microstructure as well as a reduction in fiber diameter. Results of water-scaffolds interaction indicated higher hydrophilicity and absorption capacity as a function of graphene oxide addition. Scaffolds’ mechanical properties and physical stability improved after the addition of graphene oxide. Inducing bioactivity after the addition of simvastatin-loaded graphene oxide terminated its capability for hard tissue engineering application, evidenced by microscopy images and phase characterization. Nanofibrous scaffolds could act as a sustained drug carrier. Using the optimal concentration of graphene oxide-simvastatin is necessary to avoid toxic effects on tissue. Results show that the scaffolds are biocompatible to the MG-63 cell and support alkaline phosphatase activity, illustrating their potential use in bone tissue engineering. Briefly, graphene-simvastatin-incorporated in polymeric nanofibers was developed to increase bioactive components’ synergistic effect to induce more bioactivity and improve physical and mechanical properties as well as in vitro interactions for better results in bone repair.