Nanoscale β-TCP-Laden GelMA/PCL Composite Membrane for Guided Bone Regeneration

Bifunctional naringenin-laden gelatin methacryloyl scaffolds with osteogenic and anti-inflammatory properties

OBJECTIVE

To fabricate and characterize an innovative gelatin methacryloyl/GelMA electrospun scaffold containing the citrus flavonoid naringenin/NA with osteogenic and anti-inflammatory properties.

METHODS

GelMA scaffolds (15 % w/v) containing 0/Control, 5, 10, or 20 % of NA w/w were obtained via electrospinning. The chemical composition, fiber morphology/diameter, swelling/degradation profile, and NA release were investigated. Cytotoxicity, cell proliferation, adhesion and spreading, total protein/TP production, alkaline phosphatase/ALP activity, osteogenic genes expression (OCN, OPN, RUNX2), and mineralized nodules deposition/MND with human alveolar bone-derived mesenchymal stem cells (aBMSCs) seeded on the scaffolds were assessed. Moreover, aBMSCs seeded on the scaffolds and stimulated with tumor necrosis factor-alpha/TNF-α were submitted to collagen, nitric oxide/NO, interleukin/IL-1α, and IL-6 production assessment. Data were analyzed using ANOVA and t-student/post-hoc tests (α = 5 %).

RESULTS

NA-laden scaffolds presented increased fiber diameter, lower swelling capacity, and faster degradation profile over 28 days (p < 0.05). NA release was detected over time. Cell adhesion and spreading, and TP production were similar between GelMA and GelMA+NA5 % scaffolds, while cell proliferation, ALP activity, OCN/OPN/RUNX2 gene expression, and MND were higher for GelMA+NA5 % scaffolds (p < 0.05). Cells seeded on control scaffolds and TNF-α-stimulated presented higher levels of NO, IL-1α/IL-6, and lower levels of collagen (p < 0.05). In contrast, cells seeded on GelMA+NA5 % scaffolds showed downregulation of inflammatory markers and higher collagen synthesis (p < 0.05).

SIGNIFICANCE

GelMA+NA5 % scaffold was cytocompatible, stimulated aBMSCs proliferation and differentiation, and downregulated inflammatory mediators' synthesis, suggesting its therapeutic effect as a multi-target bifunctional scaffold with osteogenic and anti-inflammatory properties for bone tissue engineering.

Shear Flow-Assembled Janus Membrane with Bifunctional Osteogenic and Antibacterial Effects for Guided Bone Regeneration

Guided bone regeneration (GBR) membranes that reside at the interface between the bone and soft tissues for bone repair attract increasing attention, but currently developed GBR membranes suffer from relatively poor osteogenic and antibacterial effects as well as limited mechanical property and biodegradability. We present here the design and fabrication of a bifunctional Janus GBR membrane based on a shear flow-driven layer by a layer self-assembly approach. The Janus GBR membrane comprises a calcium phosphate-collagen/polyethylene glycol (CaP@COL/PEG) layer and a chitosan/poly(acrylic acid) (CHI/PAA) layer on different sides of a collagen membrane to form a sandwich structure. The membrane exhibits good mechanical stability and tailored biodegradability. It is found that the CaP@COL/PEG layer and CHI/PAA layer contribute to the osteogenic differentiation and antibacterial function, respectively. In comparison with the control group, the Janus GBR membrane displays a 2.52-time and 1.84-time enhancement in respective volume and density of newly generated bone. The greatly improved bone repair ability of the Janus GBR membrane is further confirmed through histological analysis, and it has great potential for practical applications in bone tissue engineering.

The role of fibroblast growth factor-2 in modulating the differentiation of periodontal ligament and alveolar bone-derived stem cells

OBJECTIVE

This study examined how range concentrations of Fibroblast Growth Factor-2 (FGF-2) influence the differentiation and activity of human-derived periodontal ligament (hPDLSCs) and alveolar bone-derived stem cells (haBMSCs).

DESIGN

hPDLSCs and haBMSCs were cultured with varying concentrations of FGF-2 (0, 1, 2.5, 5, 10, 20 ng/mL) and monitored for osteogenic differentiation through alkaline phosphatase (ALP) activity and quantification of gene expression (qRT-PCR) for osteogenesis markers. Additionally, alizarin red staining and a hydroxyproline colorimetric assay evaluated and quantified osteogenic matrix mineralization and collagen deposition. Statistical analyses were performed using one-way ANOVA or two-way ANOVA for multiple comparisons between groups.

RESULTS

At low FGF-2 concentrations, hPDLSCs differentiated toward an osteogenic lineage, whereas higher concentrations of FGF-2 inhibited osteogenesis and promoted fibroblastic differentiation. The effect of FGF-2 at the lowest concentration tested (1 ng/mL) led to significantly higher ALP activity than osteogenically induced positive controls at early time points and equivalent RUNX2 expression at early and later time points. FGF-2 supplementation of haBMSC cultures was sufficient, at all concentrations, to increase ALP activity at an earlier time point. Mineralization of haBMSC cultures increased significantly within 5-20 ng/mL FGF-2 concentrations under basal growth media conditions (α-minimal essential medium supplemented with 15 % fetal bovine serum and 1 % penicillin/streptomycin).

CONCLUSIONS

FGF-2 has a dual capacity in promoting osteogenic and fibroblastic differentiation within hPDLSCs contingent upon the dosage and timing of administration, alongside supporting osteogenic differentiation in haBMSCs. These findings underscore the need for precision growth factors dosing when considering the design of biomaterials for periodontal regeneration.

Application and Development of Electrospun Nanofiber Scaffolds for Bone Tissue Engineering

Nanofiber scaffolds have gained significant attention in the field of bone tissue engineering. Electrospinning, a straightforward and efficient technique for producing nanofibers, has been extensively researched. When used in bone tissue engineering scaffolds, electrospun nanofibers with suitable surface properties promote new bone tissue growth and enhance cell adhesion. Recent advancements in electrospinning technology have provided innovative approaches for scaffold fabrication in bone tissue engineering. This review comprehensively examines the utilization of electrospun nanofibers in bone tissue engineering scaffolds and evaluates the relevant literature. The review begins by presenting the fundamental principles and methodologies of electrospinning. It then discusses various materials used in the production of electrospun nanofiber scaffolds for bone tissue engineering, including natural and synthetic polymers, as well as certain inorganic materials. The challenges associated with these materials are also described. The review focuses on novel electrospinning techniques for scaffold construction in bone tissue engineering, such as multilayer nanofibers, multifluid electrospinning, and the integration of electrospinning with other methods. Recent advancements in electrospinning technology have enabled the fabrication of precisely aligned nanofiber scaffolds with nanoscale architectures. These innovative methods also facilitate the fabrication of biomimetic structures, wherein bioactive substances can be incorporated and released in a controlled manner for drug delivery purposes. Moreover, they address issues encountered with traditional electrospun nanofibers, such as mechanical characteristics and biocompatibility. Consequently, the development and implementation of novel electrospinning technologies have revolutionized scaffold fabrication for bone tissue engineering.

Enhancing calvarial defects repair with PDGF-BB mimetic peptide hydrogels

Addressing bone defects represents a significant challenge to public health. Localized delivery of growth factor has emerged as promising approach for bone regeneration. However, the clinical application of Platelet-Derived Growth Factor (PDGF) is hindered by its high cost and short half-life. In this work, we introduce the application of PDGF-mimicking peptide (PMP1) hydrogels for calvarial defect restoration, showcasing their remarkable effectiveness. Through osteogenic differentiation assays and q-PCR analyses, we demonstrate PMP1's substantial capacity to enhance osteogenic differentiation of bone marrow mesenchymal stem cell (BMSC), leading to increased expression of crucial osteogenic genes. Further molecular mechanistic investigations reveal PMP1's activation of the PI3K-AKT-mTOR signaling pathway, a key element of its osteogenic effect. In vivo experiments utilizing a rat calvaria critical-sized defect model underscore the hydrogels' exceptional ability to accelerate new bone formation, thereby significantly advancing the restoration of calvaria defects. This research provides a promising bioactive material for bone tissue regeneration.

Janus Membrane with Intrafibrillarly Strontium-Apatite-Mineralized Collagen for Guided Bone Regeneration

Commercial collagen membranes face difficulty in guided bone regeneration (GBR) due to the absence of hierarchical structural design, effective interface management, and diverse bioactivity. Herein, a Janus membrane called SrJM is developed that consists of a porous collagen face to enhance osteogenic function and a dense face to maintain barrier function. Specifically, biomimetic intrafibrillar mineralization of collagen with strontium apatite is realized by liquid precursors of amorphous strontium phosphate. Polycaprolactone methacryloyl is further integrated on one side of the collagen as a dense face, which endows SrJM with mechanical support and a prolonged lifespan. In vitro experiments demonstrate that the dense face of SrJM acts as a strong barrier against fibroblasts, while the porous face significantly promotes cell adhesion and osteogenic differentiation through activation of calcium-sensitive receptor/integrin/Wnt signaling pathways. Meanwhile, SrJM effectively enhances osteogenesis and angiogenesis by recruiting stem cells and modulating osteoimmune response, thus creating an ideal microenvironment for bone regeneration. In vivo studies verify that the bone defect region guided by SrJM is completely repaired by newly formed vascularized bone. Overall, the outstanding performance of SrJM supports its ongoing development as a multifunctional GBR membrane, and this study provides a versatile strategy of fabricating collagen-based biomaterials for hard tissue regeneration.

Injectable and Photocurable Gene Scaffold Facilitates Efficient Repair of Spinal Cord Injury

RNA interference-based gene therapy has led to a strategy for spinal cord injury (SCI) therapy. However, there have been high requirements regarding the optimal gene delivery vector for siRNA-based SCI gene therapy. Here, we developed an injectable and photocurable lipid nanoparticle GelMA (PLNG) hydrogel scaffold for controlled dual siRNA delivery at the SCI wound site. The prepared PLNG scaffold could efficiently protect and retain the bioactivity of the siRNA nanocomplex. It facilitated sustainable siRNA release along with degradation in 7 days. After loading dual siRNA targeting phosphatase and tensin homologue (PTEN) and macrophage migration inhibitory factor (MIF) simultaneously, the locally administered siRNAs/PLNG scaffold efficiently improved the Basso mouse scale (BMS) score and recovered ankle joint movement and plantar stepping after treatment with only three doses. We further proved that the siRNAs/PLNG scaffold successfully regulated the activities of neurons, microglia, and macrophages, thus promoting neuron axon regeneration and remyelination. The protein array results suggested that the siRNAs/PLNG scaffold could increase the expression of growth factors and decrease the expression of inflammatory factors to regulate neuroinflammation in SCI and create a neural repair environment. Our results suggested that the PLNG scaffold siRNA delivery system is a potential candidate for siRNA-based SCI therapy.

A Bioactive Gelatin-Methacrylate Incorporating Magnesium Phosphate Cement for Bone Regeneration

Maintaining proper mechanical strength and tissue volume is important for bone growth at the site of a bone defect. In this study, potassium magnesium phosphate hexahydrate (KMgPO4·6H2O, MPC) was applied to gelma-methacrylate hydrogel (GelMA) to prepare GelMA/MPC composites (GMPCs). Among these, 5 GMPC showed the best performance in vivo and in vitro. These combinations significantly enhanced the mechanical strength of GelMA and regulated the degradation and absorption rate of MPC. Considerably better mechanical properties were noted in 5 GMPC compared with other concentrations. Better bioactivity and osteogenic ability were also found in 5 GMPC. Magnesium ions (Mg2+) are bioactive and proven to promote bone tissue regeneration, in which the enhancement efficiency is closely related to Mg2+ concentrations. These findings indicated that GMPCs that can release Mg2+ are effective in the treatment of bone defects and hold promise for future in vivo applications.

GelMA/TCP nanocomposite scaffold for vital pulp therapy

Pulp capping is a necessary procedure for preserving the vitality and health of the dental pulp, playing a crucial role in preventing the need for root canal treatment or tooth extraction. Here, we developed an electrospun gelatin methacryloyl (GelMA) fibrous scaffold incorporating beta-tricalcium phosphate (TCP) particles for pulp capping. A comprehensive morphological, physical-chemical, and mechanical characterization of the engineered fibrous scaffolds was performed. In vitro bioactivity, cell compatibility, and odontogenic differentiation potential of the scaffolds in dental pulp stem cells (DPSCs) were also evaluated. A pre-clinical in vivo model was used to determine the therapeutic role of the GelMA/TCP scaffolds in promoting hard tissue formation. Morphological, chemical, and thermal analyses confirmed effective TCP incorporation in the GelMA nanofibers. The GelMA+20%TCP nanofibrous scaffold exhibited bead-free morphology and suitable mechanical and degradation properties. In vitro, GelMA+20%TCP scaffolds supported apatite-like formation, improved cell spreading, and increased deposition of mineralization nodules. Gene expression analysis revealed upregulation of ALPL, RUNX2, COL1A1, and DMP1 in the presence of TCP-laden scaffolds. In vivo, analyses showed mild inflammatory reaction upon scaffolds' contact while supporting mineralized tissue formation. Although the levels of Nestin and DMP1 proteins did not exceed those associated with the clinical reference treatment (i.e., mineral trioxide aggregate), the GelMA+20%TCP scaffold exhibited comparable levels, thus suggesting the emergence of differentiated odontoblast-like cells capable of dentin matrix secretion. Our innovative GelMA/TCP scaffold represents a simplified and efficient alternative to conventional pulp-capping biomaterials. STATEMENT OF SIGNIFICANCE: Vital pulp therapy (VPT) aims to preserve dental pulp vitality and avoid root canal treatment. Biomaterials that bolster mineralized tissue regeneration with ease of use are still lacking. We successfully engineered gelatin methacryloyl (GelMA) electrospun scaffolds incorporated with beta-tricalcium phosphate (TCP) for VPT. Notably, electrospun GelMA-based scaffolds containing 20% (w/v) of TCP exhibited favorable mechanical properties and degradation, cytocompatibility, and mineralization potential indicated by apatite-like structures in vitro and mineralized tissue deposition in vivo, although not surpassing those associated with the standard of care. Collectively, our innovative GelMA/TCP scaffold represents a simplified alternative to conventional pulp capping materials such as MTA and Biodentine™ since it is a ready-to-use biomaterial, requires no setting time, and is therapeutically effective.

E7-Conjugated Bio-Inspired Microspheres as a Biological Barrier for Guided Tissue Regeneration

Guided tissue regeneration (GTR), which is based on creating a physical barrier to prevent the downgrowth of epithelial and connective tissues into the defect site, has been widely used in clinical practice for periodontal regeneration for many years. However, its outcomes remain variable due to highly specific indications, the demand for proficient surgical skills, and frequent occurrence of complications. In this study, we developed a new GTR biomaterial that acts as a biological barrier for epithelial cells and fibroblasts while also serving as a scaffold for bone marrow-derived mesenchymal stem cells (BMSCs) and periodontal ligament stem cells (PDLSCs). This innovative GTR biomaterial is bioinspired injectable microspheres that are self-assembled from nanofibers, and their surfaces are conjugated with E7, a short peptide that selectively promotes BMSC and PDLSC adhesion but inhibits the attachment and spreading of epithelial cells and gingival fibroblasts. The selective affinity afforded by E7 on the surfaces of the nanofibrous microspheres facilitated the colonization of BMSCs in the periodontal defect, thereby substantially improving functional periodontal regeneration, as evidenced by enhanced new bone formation, reduced root exposure, and diminished attachment loss. The remarkable superiority of the bioinspired microspheres over conventional GTR materials in promoting periodontal regeneration underscores the potential of this innovative approach to enhance the efficacy of functional periodontal tissue regeneration.

Injectable Methacrylated Gelatin Hydrogel for Safe Sodium Hypochlorite Delivery in Endodontics

Keeping sodium hypochlorite (NaOCl) within the root canal is challenging in regenerative endodontics. In this study, we developed a drug delivery system using a gelatin methacryloyl (GelMA) hydrogel incorporated with aluminosilicate clay nanotubes (HNTs) loaded with NaOCl. Pure GelMA, pure HNTs, and NaOCl-loaded HNTs carrying varying concentrations were assessed for chemo-mechanical properties, degradability, swelling capacity, cytocompatibility, antimicrobial and antibiofilm activities, and in vivo for inflammatory response and degradation. SEM images revealed consistent pore sizes of 70-80 µm for all samples, irrespective of the HNT and NaOCl concentration, while HNT-loaded hydrogels exhibited rougher surfaces. The hydrogel's compressive modulus remained between 100 and 200 kPa, with no significant variations. All hydrogels demonstrated a 6-7-fold mass increase and complete degradation by the seventh day. Despite an initial decrease in cell viability, all groups recovered to 65-80% compared to the control. Regarding antibacterial and antibiofilm properties, 12.5 HNT(Double) showed the highest inhibition zone on agar plates and the most significant reduction in biofilm compared to other groups. In vivo, the 12.5 HNT(Double) group displayed partial degradation after 21 days, with mild localized inflammatory responses but no tissue necrosis. In conclusion, the HNT-NaOCl-loaded GelMA hydrogel retains the disinfectant properties, providing a safer option for endodontic procedures without harmful potential.

GelMA-based bioactive hydrogel scaffolds with multiple bone defect repair functions: therapeutic strategies and recent advances

Currently, the clinical treatment of critical bone defects attributed to various causes remains a great challenge, and repairing these defects with synthetic bone substitutes is the most common strategy. In general, tissue engineering materials that mimic the structural, mechanical and biological properties of natural bone have been extensively applied to fill bone defects and promote in situ bone regeneration. Hydrogels with extracellular matrix (ECM)-like properties are common tissue engineering materials, among which methacrylate-based gelatin (GelMA) hydrogels are widely used because of their tunable mechanical properties, excellent photocrosslinking capability and good biocompatibility. Owing to their lack of osteogenic activity, however, GelMA hydrogels are combined with other types of materials with osteogenic activities to improve the osteogenic capability of the current composites. There are three main aspects to consider when enhancing the bone regenerative performance of composite materials: osteoconductivity, vascularization and osteoinduction. Bioceramics, bioglass, biomimetic scaffolds, inorganic ions, bionic periosteum, growth factors and two-dimensional (2D) nanomaterials have been applied in various combinations to achieve enhanced osteogenic and bone regeneration activities. Three-dimensional (3D)-bioprinted scaffolds are a popular research topic in bone tissue engineering (BTE), and printed and customized scaffolds are suitable for restoring large irregular bone defects due to their shape and structural tunability, enhanced mechanical properties, and good biocompatibility. Herein, the recent progress in research on GelMA-based composite hydrogel scaffolds as multifunctional platforms for restoring critical bone defects in plastic or orthopedic clinics is systematically reviewed and summarized. These strategies pave the way for the design of biomimetic bone substitutes for effective bone reconstruction with good biosafety. This review provides novel insights into the development and current trends of research on GelMA-based hydrogels as effective bone tissue engineering (BTE) scaffolds for correcting bone defects, and these contents are summarized and emphasized from various perspectives (osteoconductivity, vascularization, osteoinduction and 3D-bioprinting). In addition, advantages and deficiencies of GelMA-based bone substitutes used for bone regeneration are put forward, and corresponding improvement measures are presented prior to their clinical application in near future (created with BioRender.com).