Electrospun PLLA nanofiber scaffolds and their use in combination with BMP-2 for reconstruction of bone defects

Extracellular derivatives for bone metabolism

BACKGROUND

Bone metabolism can maintain the normal homeostasis and function of bone tissue. Once the bone metabolism balance is broken, it will cause osteoporosis, osteoarthritis, bone defects, bone tumors, or other bone diseases. However, such orthopedic diseases still have many limitations in clinical treatment, such as drug restrictions, drug tolerance, drug side effects, and implant rejection.

AIM OF REVIEW

In complex bone therapy and bone regeneration, extracellular derivatives have become a promising research focus to solve the problems of bone metabolic diseases. These derivatives, which include components such as extracellular matrix, growth factors, and extracellular vesicles, have significant therapeutic potential. It has the advantages of good biocompatibility, low immune response, and dynamic demand for bone tissue. The purpose of this review is to provide a comprehensive perspective on extracellular derivatives for bone metabolism and elucidate the intrinsic properties and versatility of extracellular derivatives. Further discussion of them as innovative advanced orthopedic materials for improving the effectiveness of bone therapy and regeneration processes.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we first listed the types and functions of three extracellular derivatives. Then, we discussed the effects of extracellular derivatives of different cell sources on bone metabolism. Subsequently, we collected applications of extracellular derivatives in the treatment of bone metabolic diseases and summarized the advantages and challenges of extracellular derivatives in clinical applications. Finally, we prospected the extracellular derivatives in novel orthopedic materials and clinical applications. We hope that the comprehensive understanding of extracellular derivatives in bone metabolism will provide new solutions to bone diseases.

Nanotechnology development in surgical applications: recent trends and developments

This paper gives a detailed analysis of nanotechnology's rising involvement in numerous surgical fields. We investigate the use of nanotechnology in orthopedic surgery, neurosurgery, plastic surgery, surgical oncology, heart surgery, vascular surgery, ophthalmic surgery, thoracic surgery, and minimally invasive surgery. The paper details how nanotechnology helps with arthroplasty, chondrogenesis, tissue regeneration, wound healing, and more. It also discusses the employment of nanomaterials in implant surfaces, bone grafting, and breast implants, among other things. The article also explores various nanotechnology uses, including stem cell-incorporated nano scaffolds, nano-surgery, hemostasis, nerve healing, nanorobots, and diagnostic applications. The ethical and safety implications of using nanotechnology in surgery are also addressed. The future possibilities of nanotechnology are investigated, pointing to a possible route for improved patient outcomes. The essay finishes with a comment on nanotechnology's transformational influence in surgical applications and its promise for future breakthroughs.

Advances of three-dimensional (3D) culture systems for in vitro spermatogenesis

The loss of germ cells and spermatogenic failure in non-obstructive azoospermia are believed to be the main causes of male infertility. Laboratory studies have used in vitro testicular models and different 3-dimensional (3D) culture systems for preservation, proliferation and differentiation of spermatogonial stem cells (SSCs) in recent decades. The establishment of testis-like structures would facilitate the study of drug and toxicity screening, pathological mechanisms and in vitro differentiation of SSCs which resulted in possible treatment of male infertility. The different culture systems using cellular aggregation with self-assembling capability, the use of different natural and synthetic biomaterials and various methods for scaffold fabrication provided a suitable 3D niche for testicular cells development. Recently, 3D culture models have noticeably used in research for their architectural and functional similarities to native microenvironment. In this review article, we briefly investigated the recent 3D culture systems that provided a suitable platform for male fertility preservation through organ culture of testis fragments, proliferation and differentiation of SSCs.

A mini-review on the emerging role of nanotechnology in revolutionizing orthopedic surgery: challenges and the road ahead

An emerging application of nanotechnology in medicine currently being developed involves employing nanoparticles to deliver drugs, heat, light, or other substances to specific types of cells (such as cancer cells). As most biological molecules exist and function at the nanoscale, engineering and manipulating matter at the molecular level has many advantages in the field of medicine (nanomedicine). Although encouraging, it remains unclear how much of this will ultimately result in improved patient care. In surgical specialties, clinically relevant nanotechnology applications include the creation of surgical instruments, suture materials, imaging, targeted drug therapy, visualization methods, and wound healing techniques. Burn lesion and scar management is an essential nanotechnology application. Prevention, diagnosis, and treatment of numerous orthopedic conditions are crucial technological aspects for patients' functional recovery. Orthopedic surgery is a specialty that deals with the diagnosis and treatment of musculoskeletal disorders. In recent years, the field of orthopedics has been revolutionized by the advent of nanotechnology. Using biomaterials comprised of nanoparticles and structures, it is possible to substantially enhance the efficacy of such interactions through nanoscale material modifications. This serves as the foundation for the majority of orthopedic nanotechnology applications. In orthopedic surgery, nanotechnology has been applied to improve surgical outcomes, enhance bone healing, and reduce complications associated with orthopedic procedures. This mini-review summarizes the present state of nanotechnology in orthopedic surgery, including its applications as well as possible future directions.

Heterogeneous porous PLLA/PCL fibrous scaffold for bone tissue regeneration

Bone tissue engineering has become one of the most promising therapeutic methods to treat bone defects. A suitable scaffolding material to regenerate new bone tissues should have a high specific surface area, high porosity and a suitable surface structure which benefit cell attachment, proliferation, and differentiation. In this study, an acetone post-treatment strategy was developed to generate heterogeneous structure. After PLLA/PCL nanofibrous membranes were electrospun and collected, they were treated with acetone to generate a highly porous structure. Meanwhile, part of PCL was extracted from the fibre and enriched on the fibre surface. The cell affinity of the nanofibrous membrane was verified by human osteoblast-like cells assay. The proliferation rate of heterogeneous samples increased 190.4 %, 265.5 % and 137.9 % at day 10 compared with pristine samples. These results demonstrated that the heterogeneous PLLA/PCL nanofibrous membranes could enhance osteoblast adhesion and proliferation. With high surface area (average surface area 36.302 m²/g) and good mechanical properties (average Young's modulus 1.65 GPa and average tensile strength 5.1 MPa), the heterogeneous PLLA/PCL membrane should have potential applications in the field of bone regeneration.

Electrospun and 3D printed polymeric materials for one-stage critical-size long bone defect regeneration inspired by the Masquelet technique: Recent Advances

Critical-size long bone defects represent one of the major causes of fracture non-union and remain a significant challenge in orthopaedic surgery. Two-stage procedures such as a Masquelet technique demonstrate high level of success however their main disadvantage is the need for a second surgery, which is required to remove the non-resorbable cement spacer and to place the bone graft into the biological chamber formed by the 'induced membrane'. Recent research efforts have therefore been dedicated towards the design, fabrication and testing of resorbable implants that could mimic the biological functions of the cement spacer and the induced membrane. Amongst the various manufacturing techniques used to fabricate these implants, three-dimensional (3D) printing and electrospinning methods have gained a significant momentum due their high-level controllability, scalable processing and relatively low cost. This review aims to present recent advances in the evaluation of electrospun and 3D printed polymeric materials for critical-size, long bone defect reconstruction, emphasizing both their beneficial properties and current limitations. Furthermore, we present and discuss current state-of-the art techniques required for characterisation of the materials' physical, mechanical and biological characteristics. These represent the essential first steps towards the development of personalised implants for single-surgery, large defect reconstruction in weight-bearing bones.

Ternary MXene-loaded PLCL/collagen nanofibrous scaffolds that promote spontaneous osteogenic differentiation

Conventional bioinert bone grafts often have led to failure in osseointegration due to low bioactivity, thus much effort has been made up to date to find alternatives. Recently, MXene nanoparticles (NPs) have shown prominent results as a rising material by possessing an osteogenic potential to facilitate the bioactivity of bone grafts or scaffolds, which can be attributed to the unique repeating atomic structure of two carbon layers existing between three titanium layers. In this study, we produced MXene NPs-integrated the ternary nanofibrous matrices of poly(L-lactide-co-ε-caprolactone, PLCL) and collagen (Col) decorated with MXene NPs (i.e., PLCL/Col/MXene), as novel scaffolds for bone tissue engineering, via electrospinning to explore the potential benefits for the spontaneous osteogenic differentiation of MC3T3-E1 preosteoblasts. The cultured cells on the physicochemical properties of the nanofibrous PLCL/Col/MXene-based materials revealed favorable interactions with the supportive matrices, highly suitable for the growth and survival of preosteoblasts. Furthermore, the combinatorial ternary material system of the PLCL/Col/MXene nanofibers obviously promoted spontaneous osteodifferentiation with positive cellular responses by providing effective microenvironments for osteogenesis. Therefore, our results suggest that the unprecedented biofunctional advantages of the MXene-integrated PLCL/Col nanofibrous matrices can be expanded to a wide range of strategies for the development of effective scaffolds in bone tissue regeneration.

Advances in Electrospun Hybrid Nanofibers for Biomedical Applications

Electrospun hybrid nanofibers, based on functional agents immobilized in polymeric matrix, possess a unique combination of collective properties. These are beneficial for a wide range of applications, which include theranostics, filtration, catalysis, and tissue engineering, among others. The combination of functional agents in a nanofiber matrix offer accessibility to multifunctional nanocompartments with significantly improved mechanical, electrical, and chemical properties, along with better biocompatibility and biodegradability. This review summarizes recent work performed for the fabrication, characterization, and optimization of different hybrid nanofibers containing varieties of functional agents, such as laser ablated inorganic nanoparticles (NPs), which include, for instance, gold nanoparticles (Au NPs) and titanium nitride nanoparticles (TiNPs), perovskites, drugs, growth factors, and smart, inorganic polymers. Biocompatible and biodegradable polymers such as chitosan, cellulose, and polycaprolactone are very promising macromolecules as a nanofiber matrix for immobilizing such functional agents. The assimilation of such polymeric matrices with functional agents that possess wide varieties of characteristics require a modified approach towards electrospinning techniques such as coelectrospinning and template spinning. Additional focus within this review is devoted to the state of the art for the implementations of these approaches as viable options for the achievement of multifunctional hybrid nanofibers. Finally, recent advances and challenges, in particular, mass fabrication and prospects of hybrid nanofibers for tissue engineering and biomedical applications have been summarized.

3D Printed Hydroxyapatite Promotes Congruent Bone Ingrowth in Rat Load Bearing Defects

3D porous hydroxyapatite scaffolds produced by conventional foaming processes have limited control over the scaffold's pore size, geometry, and pore interconnectivity. In addition, random internal pore architecture often results in limited clinical success. Imitating the intricate 3D architecture and the functional dynamics of skeletal deformations is a difficult task, highlighting the necessity for a custom-made, on-demand tissue replacement, for which 3D printing is a potential solution. To combat these problems, here we report the ability of 3D printed hydroxyapatite scaffolds for in vivo bone regeneration in a rat tibial defect model. Rapid prototyping using the direct-write technique to fabricate 25 mm2 hydroxyapatite scaffolds were employed for precise control over geometry (both external and internal) and scaffold chemistry. Bone ingrowth was determined using histomorphometry and a novel micro-CT image analysis. Substantial bone ingrowth was observed in implants that filled the defect site. Further validating this quantitatively by micro-CT, the Bone mineral density of the implant at the defect site was 1024 mgHA/ccm, which was approximately 61.5% more than the bone mineral density found with the sham control at the defect site. In addition, no evident immunoinflammatory response was observed in the H&E micrographs. Interestingly, the present study showed a positive correlation with the outcomes obtained in our previous in vitro study. Overall, the results suggest that 3D printed hydroxyapatite scaffolds developed in this study offer a suitable matrix for rendering patient-specific and defect-specific bone formation and warrant further testing for clinical application.

Current Methods in the Study of Nanomaterials for Bone Regeneration

Nanomaterials show great promise as bone regeneration materials. They can be used as fillers to strengthen bone regeneration scaffolds, or employed in their natural form as carriers for drug delivery systems. A variety of experiments have been conducted to evaluate the osteogenic potential of bone regeneration materials. In vivo, such materials are commonly tested in animal bone defect models to assess their bone regeneration potential. From an ethical standpoint, however, animal experiments should be minimized. A standardized in vitro strategy for this purpose is desirable, but at present, the results of studies conducted under a wide variety of conditions have all been evaluated equally. This review will first briefly introduce several bone regeneration reports on nanomaterials and the nanosize-derived caveats of evaluations in such studies. Then, experimental techniques (in vivo and in vitro), types of cells, culture media, fetal bovine serum, and additives will be described, with specific examples of the risks of various culture conditions leading to erroneous conclusions in biomaterial analysis. We hope that this review will create a better understanding of the evaluation of biomaterials, including nanomaterials for bone regeneration, and lead to the development of versatile assessment methods that can be widely used in biomaterial development.

In vitro comparison of nanofibrillar and macroporous-spongious composite tissue scaffolds for periodontal tissue engineering

PURPOSE/AIM OF THE STUDY

The ultimate goal of periodontal treatment is to regenerate the lost periodontal tissues. The interest in nanomaterials in dentistry is growing rapidly and has focused on improvements in various biomedical applications, such as periodontal regeneration and periodontal tissue engineering. To enhance periodontal tissue regeneration, hydroxyapatite (HA) was used in conjunction with other scaffold materials, such as Poly lactic-co-glycolic-acid (PLGA) and collagen (C). The main target of this study was to compare the effects of nano and macrostructures of the tissue scaffolds on cell behavior in vitro for periodontal tissue engineering.

MATERIALS AND METHODS

Nanofibrillar and macroporous-spongious composite tissue scaffolds were produced using PLGA/C/HA. Subgroups with BMP-2 signal molecule and without HA were also created. The scaffolds were characterized by FTIR, SEM/EDX techniques, and mechanical tests. The scaffolds were compared in the periodontal ligament (PDL) and MCT3-E1 cell cultures. The cell behaviors; adhesions by SEM, proliferation by WST-1, differentiation by ALP and mineralization with Alizarin Red Tests were determined.

RESULTS

Cell adhesion and mineralization were higher in the nanofibrillar scaffolds compared to the macroporous-spongious scaffolds. Macroporous-spongious scaffolds seemed better for the proliferation of PDL cells and differentiation of MC3T3-E1-preosteoblastic cells, while nanofibrillar scaffolds were more convenient for the differentiation of PDL cells and proliferation of MC3T3-E1-preosteoblastic cells.

CONCLUSIONS

In general, nanofibrillar scaffolds showed more favorable results in cell behaviors, compared to the macroporous-spongious scaffolds, and mostly, BMP-2 and HA promoted the activities of the cells.

Experimental study on the biocompatibility and osteogenesis induction ability of PLLA/DDM scaffolds

To investigate the characterization and function of a novel porous osteogenic material (PLLA / DDM) containing polylactic acid and demineralized dentin matrix. The surface morphology and composition of the material were observed by SEM and EDS. The physical characteristics of the material were detected by roughness and water contact angle analyses. The rate of weight loss and change in the pH value of the material were observed by scaffold degradation experiments. Four types of material were investigated: polylactic acid (PLLA) scaffold, demineralized dentin matrix (DDM) particles, PLLA/DDM scaffold and a blank control. The osteogenic effect and osteogenic characteristics of the new materials were explored through in vivo and in vitro osteogenic experiments. SEM analysis showed that DDM powder was uniformly distributed in the polylactic acid scaffold, and the water contact angle revealed that the water absorption of the porous scaffold was improved after the addition of DDM powder. The EDS results showed that the peak values of calcium and phosphorus were obviously increased after the addition of DDM powder, and the porosity test showed that the scaffold had higher porosity after the addition of DDM powder. Scaffold degradation experiments revealed that the scaffold gradually degraded with increasing time, and its pH value slightly increased. The results of cell culture and animal model experiments showed that the porous PLLA/DDM scaffold had good bio-compatibility and promoted cell proliferation and differentiation. In histological and micro-CT evaluations, the material showed good bio-compatibility, biodegradability and bone conductivity with host bone tissue in vivo. PLLA / DDM hybrid showed better performance than PLLA or DDM. The biocompatibility and cell growth promoting properties were stronger than those of single material.

Preparation and Characterization of Electrospun Polylactic Acid (PLA) Fiber Loaded with Birch Bark Triterpene Extract for Wound Dressing

Drug-loaded electrospun fibers have attracted increasing attention as a promising wound dressing material due to their capability of preventing from infections and inflammation and maintaining an appropriate environment for wound healing. In this study, polylactic acid (PLA), which is widely used in wound management, was chosen as electrospinnable polymer. A triterpene extract (TE) from the outer bark of birch known for its anti-inflammatory, antiviral, antibacterial, and wound healing effects was chosen to produce TE-loaded PLA electrospun fibers for wound dressing. A binary solvent system of dichloromethane (DCM) and dimethyl sulfoxide (DMSO) was employed, and the ratio of the solvents was optimized for preparing smooth and uniform fibers. The morphology of TE-loaded PLA electrospun fibers was investigated by scanning electron microscopy (SEM). The entrapment of TE in PLA fibers was confirmed by confocal laser scanning microscopy (CLSM). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to analyze the solid state of TE in PLA fibers. The release behavior of TE was assayed by a shaking flask method for a period of 96 h. The results revealed that TE-loaded electrospun PLA microfibers could be reliably prepared and are promising future candidates in wound therapy.

A Biomimetic Macroporous Hybrid Scaffold with Sustained Drug Delivery for Enhanced Bone Regeneration

Bone regeneration is a highly complex physiological process regulated by several factors. In particular, bone-mimicking extracellular matrix and available osteogenic growth factors such as bone morphogenetic protein (BMP) have been regarded as key contributors for bone regeneration. In this study, we developed a biomimetic hybrid scaffold (CEGH) with sustained release of BMP-2 that would result in enhanced bone formation. This hybrid scaffold, composed of BMP-2-loaded cryoelectrospun poly(ε-caprolactone) (PCL) (CE) surrounded by a macroporous gelatin/heparin cryogel (GH), is designed to overcome the drawbacks of the relatively weak mechanical properties of cryogels and poor biocompatibility and hydrophobicity of electrospun PCL. The GH component of the hybrid scaffold provides a hydrophilic surface to improve the biological response of the cells, while the CE component increases the mechanical strength of the scaffold to provide enhanced mechanical support for the defect area and a stable environment for osteogenic differentiation. After analyzing characteristics of the hybrid scaffold such as hydrophilicity, pore difference, mechanical properties, and surface charge, we confirmed that the hybrid scaffold shows enhanced cell proliferation rate and apatite formation in simulated body fluid. Then, we evaluated drug release kinetics of CEGH and confirmed the sustained release of BMP-2. Finally, the enhanced osteogenic differentiation of CEGH with sustained release of BMP-2 was confirmed by Alizarin Red S staining and real-time PCR analysis.

Growth factor loading on aliphatic polyester scaffolds

Cells, scaffolds and growth factors are three elements of tissue engineering. The success of tissue engineering methods relies on precise and dynamic interactions between cells, scaffolds and growth factors. Aliphatic polyester scaffolds are promising tissue engineering scaffolds that possess good mechanical properties, low immunogenicity, non-toxicity, and adjustable degradation rates. How growth factors can be loaded onto/into aliphatic polyester scaffolds and be constantly released with the required bioactivity to regulate cell growth and promote defect tissue repair and regeneration has become the main concern of tissue engineering researchers. In this review, the existing main methods of loading growth factors on aliphatic polyester scaffolds, the release behavior of loaded growth factors and their positive effects on cell, tissue repair and regeneration are introduced. Advantages and shortcomings of each method also are mentioned. It is still a great challenge to control the release of loaded growth factors at a certain time and at a concentration simulating the biological environment of native tissue.

Micro Magnetic Field Produced by Fe3O4 Nanoparticles in Bone Scaffold for Enhancing Cellular Activity

The low cellular activity of poly-l-lactic acid (PLLA) limits its application in bone scaffold, although PLLA has advantages in terms of good biocompatibility and easy processing. In this study, superparamagnetic Fe₃O₄ nanoparticles were incorporated into the PLLA bone scaffold prepared by selective laser sintering (SLS) for continuously and steadily enhancing cellular activity. In the scaffold, each Fe₃O₄ nanoparticle was a single magnetic domain without a domain wall, providing a micro-magnetic source to generate a tiny magnetic field, thereby continuously and steadily generating magnetic stimulation to cells. The results showed that the magnetic scaffold exhibited superparamagnetism and its saturation magnetization reached a maximum value of 6.1 emu/g. It promoted the attachment, diffusion, and interaction of MG63 cells, and increased the activity of alkaline phosphatase, thus promoting the cell proliferation and differentiation. Meanwhile, the scaffold with 7% Fe₃O₄ presented increased compressive strength, modulus, and Vickers hardness by 63.4%, 78.9%, and 19.1% compared with the PLLA scaffold, respectively, due to the addition of Fe₃O₄ nanoparticles, which act as a nanoscale reinforcement in the polymer matrix. All these positive results suggested that the PLLA/Fe₃O₄ scaffold with good magnetic properties is of great potential for bone tissue engineering applications.

Direct incorporation of mesenchymal stem cells into a Nanofiber scaffold - in vitro and in vivo analysis

Bony defects are a common problem in musculoskeletal surgery. Replacement with autologous bone grafts is limited by availability of transplant material. Sterilized cancellous bone, while being osteoconductive, has limited osteoinductivity. Nanofiber scaffolds are currently used for several purposes due to their capability of imitating the extracellular matrix. Furthermore, they allow modification to provide functional properties. Previously we showed that electrospun nanofiber scaffolds can be used for bone tissue regeneration. While aiming to use the osteoinductive capacities of collagen type-I nanofibers we saw reduced scaffold pore sizes that limited cellular migration and thus colonization of the scaffolds. Aim of the present study was the incorporation of mesenchymal stem cells into the electrospinning process of a nanofiber scaffold to produce cell-seeded nanofiber scaffolds for bone replacement. After construction of a suitable spinning apparatus for simultaneous electrospinning and spraying with independently controllable spinning and spraying devices and extensive optimization of the spinning process, in vitro and in vivo evaluation of the resulting scaffolds was conducted. Stem cells isolated from rat femora were incorporated into PLLA (poly-l-lactide acid) and PLLA-collagen type-I nanofiber scaffolds (PLLA Col I Blend) via simultaneous electrospinning and -spraying. Metabolic activity, proliferation and osteoblastic differentiation were assessed in vitro. For in vivo evaluation scaffolds were implanted into critical size defects of the rat scull. After 4 weeks, animals were sacrificed and bone healing was analyzed using CT-scans, histological, immunhistochemical and fluorescence evaluation. Successful integration of mesenchymal stem cells into the scaffolds was achieved by iteration of spinning and spraying conditions regarding polymer solvent, spinning distance, the use of a liquid counter-electrode, electrode voltage and spinning duration. In vivo formation of bone tissue was achieved. Using a PLLA scaffold, comparable results for the cell-free and cell-seeded scaffolds were found, while the cell-seeded PLLA-collagen scaffolds showed significantly better bone formation when compared to the cell-free PLLA-collagen scaffolds. These results provide support for the future use of cell-seeded nanofiber scaffolds for large bony defects.

Adjuvant Drug-Assisted Bone Healing: Advances and Challenges in Drug Delivery Approaches

Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.

Scientific, Clinical, Regulatory, and Economic Aspects of Choosing Bone Graft/Biological Options in Spine Surgery

Spinal arthrodesis is a major element of the spinal surgeon's practice. To attain successful fusion rates, attention must be paid to spinal segment immobilization and proper selection of bone graft. Autogenous bone graft (ie, ICBG), the "gold standard," with or without graft extenders and enhancers provides the foundation for most spinal fusions. ABG is the only graft option containing all 3 factors of new bone growth: osteoconductivity, osteoinductivity, and osteogenicity. While many bone graft alternatives function well as bone graft extenders, only growth factors proteins (ie, rhBMP-2 or OP-2) function as bone graft enhancers and substitutes. The search for optimal hybrid interbody cages, bone graft substitutes, autogenous or allogenic stem cells, and nanostructure scaffolds for release of growth factors continues.

The dose-time effects of fluoride on the expression and DNA methylation level of the promoter region of BMP-2 and BMP-7 in rats

Skeletal fluorosis is a chronic metabolic bone disease caused by excessive exposed to fluoride. Recent studies have shown that fluoride causes abnormal bone metabolism through disrupting the expression of Bone Morphogenetic Proteins (BMPs). However, the relationship between fluoride and BMPs is not fully understood, and the mechanism of fluoride on BMPs expression is still unclear. This study investigated the dose-time effects of fluoride on BMP-2 and BMP-7 levels and DNA methylation status of the promoter regions of these two genes in peripheral blood of rats. Eighty Wistar male rats were randomly divided into four groups and treated for 1 month and 3 months with distilled water (control), 25 mg/L, 50 mg/L or 100 mg/L of sodium fluoride (NaF). Rats exposed to fluoride had higher protein expression of BMP-2 and BMP-7 in plasma at 1 month and 3 months. An increase in BMP-2 expression was also observed with an increase of fluoride exposure time. Significant hypomethylation was observed in 2 CpG sites (CpGs) of BMP-2 and 1 CpG site of BMP-7 promoter regions in the fluoride treatment groups. It concludes that fluoride has a dose-response effect on BMP-2 in fluorosis rats, and fluoride-induced hypomethylation of specific CpGs may play an essential role in the regulation of BMP-2 and BMP-7 expression in rats.

Immobilized Macrophage Colony-Stimulating Factor (M-CSF) Regulates the Foreign Body Response to Implanted Materials

The functionality and durability of implanted biomaterials are often compromised by an exaggerated foreign body reaction (FBR). M1/M2 polarization of macrophages is a critical regulator of scaffold-induced FBR. Macrophage colony-stimulating factor (M-CSF), a hematopoietic growth factor, induces macrophages into an M2-like polarized state, leading to immunoregulation and promoting tissue repair. In the present study, we explored the immunomodulatory effects of surface bound M-CSF on poly-l-lactic acid (PLLA)-induced FBR. M-CSF was immobilized on the surface of PLLA via plasma immersion ion implantation (PIII). M-CSF functionalized PLLA, PLLA-only, and PLLA+PIII were assessed in an IL-1β luciferase reporter mouse to detect real-time levels of IL-1β expression, reflecting acute inflammation in vivo. Additionally, these different treated scaffolds were implanted subcutaneously into wild-type mice to explore the effect of M-CSF in polarization of M2-like macrophages (CD68⁺/CD206⁺), related cytokines (pro-inflammatory: IL-1β, TNF and MCP-1; anti-inflammatory: IL-10 and TGF-β), and angiogenesis (CD31) by immunofluorescent staining. Our data demonstrated that IL-1β activity in M-CSF functionalized scaffolds was ∼50% reduced compared to PLLA-only at day 1 (p < 0.01) and day 2 (p < 0.05) post-implantation. There were >2.6-fold more CD206+ macrophages in M-CSF functionalized PLLA compared to PLLA-only at day 7 (p < 0.001), along with higher levels of IL-10 at both day 7 (p < 0.05) and day 14 (p < 0.01), and TGF-β at day 3 (p < 0.05), day 7 (p < 0.05), and day 14 (p < 0.001). Lower levels of pro-inflammatory cytokines were also detected in M-CSF functionalized PLLA in the early phase of the immune response compared to PLLA-only: a ∼58% decrease at day 3 in IL-1β; a ∼91% decrease at day 3 and a ∼66% decrease at day 7 in TNF; and a ∼60% decrease at day 7 in MCP-1. Moreover, enhanced angiogenesis inside and on/near the scaffold was observed in M-CSF functionalized PLLA compared to PLLA-only at day 3 (p < 0.05) and day 7 (p < 0.05), respectively. Overall, M-CSF functionalized PLLA enhanced CD206+ macrophage polarization and angiogenesis, consistent with lower levels of pro-inflammatory cytokines and higher levels of anti-inflammatory cytokines in early stages of the host response, indicating potential immunoregulatory functions on the local environment.

Fabrication and Plasma Modification of Nanofibrous Tissue Engineering Scaffolds

This paper provides a comprehensive overview of nanofibrous structures for tissue engineering purposes and the role of non-thermal plasma technology (NTP) within this field. Special attention is first given to nanofiber fabrication strategies, including thermally-induced phase separation, molecular self-assembly, and electrospinning, highlighting their strengths, weaknesses, and potentials. The review then continues to discuss the biodegradable polyesters typically employed for nanofiber fabrication, while the primary focus lies on their applicability and limitations. From thereon, the reader is introduced to the concept of NTP and its application in plasma-assisted surface modification of nanofibrous scaffolds. The final part of the review discusses the available literature on NTP-modified nanofibers looking at the impact of plasma activation and polymerization treatments on nanofiber wettability, surface chemistry, cell adhesion/proliferation and protein grafting. As such, this review provides a complete introduction into NTP-modified nanofibers, while aiming to address the current unexplored potentials left within the field.

Sinapic acid-loaded chitosan nanoparticles in polycaprolactone electrospun fibers for bone regeneration in vitro and in vivo

Sinapic acid (SA) is a plant-derived phenolic compound known for its multiple biological properties, but its role in the promotion of bone formation is not yet well-studied. Moreover, the delivery of SA is hindered by its complex hydrophobic nature, limiting its bioavailability. In this study, we fabricated a drug delivery system using chitosan nanoparticles (nCS) loaded with SA at different concentrations. These were incorporated into polycaprolactone (PCL) fibers via an electrospinning method. nCS loaded with 50 μM SA in PCL fibers promoted osteoblast differentiation. Furthermore, SA treatment activated the osteogenesis signaling pathways in mouse mesenchymal stem cells. A critical-sized rat calvarial bone defect model system identified that the inclusion of SA into PCL/nCS fibers accelerated bone formation. Collectively, these data suggest that SA promoted osteoblast differentiation in vitro and bone formation in vivo, possibly by activating the TGF-β1/BMP/Smads/Runx2 signaling pathways, suggesting SA might have therapeutic benefits in bone regeneration.

Enhancement of osteogenic differentiation of adipose-derived stem cells by PRP modified nanofibrous scaffold

Recent developments in bone tissue engineering have paved the way for more efficient and cost-effective strategies. Additionally, utilization of autologous sources has been considered very desirable and is increasingly growing. Recently, activated platelet rich plasma (PRP) has been widely used in the field of bone tissue engineering, since it harbours a huge number of growth factors that can enhance osteogenesis and bone regeneration. In the present study, the osteogenic effects of PRP coated nanofibrous PES/PVA scaffolds on adipose-derived mesenchymal stem cells have been investigated. Common osteogenic markers were assayed by real time PCR. Alkaline phosphate activity, calcium deposition and Alizarin red staining assays were performed as well. The results revealed that the highest osteogenic differentiation occurred when cells were cultured on PRP coated PES/PVA scaffolds. Interestingly, direct application of PRP to culture media had no additive effects on osteogenesis of cells cultured on PRP coated PES/PVA scaffolds or those receiving typical osteogenic factors. The highest osteogenic effects were achieved by the simplest and most cost-effective method, i.e. merely by using PRP coated scaffolds. PRP coated PES/PVA scaffolds can maximally induce osteogenesis with no need for extrinsic factors. The major contribution of this paper to the current researches on bone regeneration is to suggest an easy, cost-effective approach to enhance osteogenesis via PRP coated scaffolds, with no additional external growth factors.

Design of a 3D BMP-2-Delivering Tannylated PCL Scaffold and Its Anti-Oxidant, Anti-Inflammatory, and Osteogenic Effects In Vitro

In this study, a novel three-dimensional (3D) bone morphogenic protein-2 (BMP-2)-delivering tannylated polycaprolactone (PCL) (BMP-2/tannic acid (TA)/PCL) scaffold with anti-oxidant, anti-inflammatory, and osteogenic activities was fabricated via simple surface coating with TA, followed by the immobilization of BMP-2 on the TA-coated PCL scaffold. The BMP-2/TA/PCL scaffold showed controlled and sustained BMP-2 release. It effectively scavenged reactive oxygen species (ROS) in cells, and increased the proliferation of MC3T3-E1 cells pre-treated with hydrogen peroxide (H₂O₂). Additionally, the BMP-2/TA/PCL scaffold significantly suppressed the mRNA levels of pro-inflammatory cytokines, including matrix metalloproteinases-3 (MMP-3), cyclooxygenase-2 (COX-2), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), in lipopolysaccharide (LPS)-induced MC3T3-E1 cells. Furthermore, it showed outstanding enhancement of the osteogenic activity of MC3T3-E1 cells through increased alkaline phosphatase (ALP) activity and calcium deposition. Our findings demonstrated that the BMP-2/TA/PCL scaffold plays an important role in scavenging ROS, suppressing inflammatory response, and enhancing the osteogenic differentiation of cells.

3D Bone Biomimetic Scaffolds for Basic and Translational Studies with Mesenchymal Stem Cells

Mesenchymal stem cells (MSCs) are recognized as an attractive tool owing to their self-renewal and differentiation capacity, and their ability to secrete bioactive molecules and to regulate the behavior of neighboring cells within different tissues. Accumulating evidence demonstrates that cells prefer three-dimensional (3D) to 2D culture conditions, at least because the former are closer to their natural environment. Thus, for in vitro studies and in vivo utilization, great effort is being dedicated to the optimization of MSC 3D culture systems in view of achieving the intended performance. This implies understanding cell–biomaterial interactions and manipulating the physicochemical characteristics of biomimetic scaffolds to elicit a specific cell behavior. In the bone field, biomimetic scaffolds can be used as 3D structures, where MSCs can be seeded, expanded, and then implanted in vivo for bone repair or bioactive molecules release. Actually, the union of MSCs and biomaterial has been greatly improving the field of tissue regeneration. Here, we will provide some examples of recent advances in basic as well as translational research about MSC-seeded scaffold systems. Overall, the proliferation of tools for a range of applications witnesses a fruitful collaboration among different branches of the scientific community.

Nanotechnology in orthopedics: a clinically oriented review

The utility of nanotechnology in medicine, specifically within the field of orthopedics, is a topic of extensive research. Our review provides a unique comprehensive overview of the current and potential future uses of nanotechnology with respect to orthopedic sub-specialties. Nanotechnology offers an immense assortment of novel applications, most notably the use of nanomaterials as scaffolds to induce a more favorable interaction between orthopedic implants and native bone. Nanotechnology has the capability to revolutionize the diagnostics and treatment of orthopedic surgery, however the long-term health effects of nanomaterials are poorly understood and extensive research is needed regarding clinical safety.

Micro and nanotechnologies for bone regeneration: Recent advances and emerging designs

Treatment of critical-size bone defects is a major medical challenge since neither the bone tissue can regenerate nor current regenerative approaches are effective. Emerging progresses in the field of nanotechnology have resulted in the development of new materials, scaffolds and drug delivery strategies to improve or restore the damaged tissues. The current article reviews promising nanomaterials and emerging micro/nano fabrication techniques for targeted delivery of biomolecules for bone tissue regeneration. In addition, recent advances in fabrication of bone graft substitutes with similar properties to normal tissue along with a brief summary of current commercialized bone grafts have been discussed.

Reconstruction of Craniomaxillofacial Bone Defects Using Tissue-Engineering Strategies with Injectable and Non-Injectable Scaffolds

Engineering craniofacial bone tissues is challenging due to their complex structures. Current standard autografts and allografts have many drawbacks for craniofacial bone tissue reconstruction; including donor site morbidity and the ability to reinstate the aesthetic characteristics of the host tissue. To overcome these problems; tissue engineering and regenerative medicine strategies have been developed as a potential way to reconstruct damaged bone tissue. Different types of new biomaterials; including natural polymers; synthetic polymers and bioceramics; have emerged to treat these damaged craniofacial bone tissues in the form of injectable and non-injectable scaffolds; which are examined in this review. Injectable scaffolds can be considered a better approach to craniofacial tissue engineering as they can be inserted with minimally invasive surgery; thus protecting the aesthetic characteristics. In this review; we also focus on recent research innovations with different types of stem-cell sources harvested from oral tissue and growth factors used to develop craniofacial bone tissue-engineering strategies.

Novel Osteobiologics and Biomaterials in the Treatment of Spinal Disorders

Spinal osteobiologics have evolved substantially in this century after the development of many product categories such as growth factors, allograft, and stem cells. The indications for the use of novel biologics within spine surgery are rapidly expanding as the mechanism of each is elucidated. While the knowledge base of bone morphogenetic protein increases with each subsequent year, the application of new nanotechnology and cell-based strategies are being reported. This review will discuss the most recent data in novel osteobiologics, and where we could use future study.

Improved Bone Regeneration With Multiporous PLGA Scaffold and BMP-2-Transduced Human Adipose-Derived Stem Cells by Cell-Permeable Peptide

OBJECTIVE

Currently, much work has focused on the engineering of bone using adipose-derived stem cells (ADSCs), which differentiate into osteogenic cells. This study was conducted to assess the bone-regenerating capacity of ADSCs with genetic modification.

MATERIALS AND METHODS

ADSCs were cultured and transduced with recombinant adenovirus-expressing bone morphogenetic protein-2 (rAd/BMP-2). Two 5-mm full-thickness bone defects were created on the parietal bones of 24 rats. The defects were left empty (n = 12), restored with a scaffold alone (n = 12), transplanted with ADSCs in osteogenic media (n = 12), or transplanted with rAd/BMP-2-transduced ADSCs (n = 12). Six defects from each group were assessed by histologic observation, histomorphometric analysis, and microcomputed tomography (micro-CT) imaging at 4 and 8 weeks after transplantation.

RESULTS

Increased new bone formation was observed in the rAd/BMP-2-transduced ADSC groups, compared with the other groups. On micro-CT, significant differences were noted in bone volume-to-tissue volume ratios between rAd/BMP-2-transduced ADSCs group and the other groups at both time points (P < 0.05).

CONCLUSION

The result demonstrates that transferring BMP-2 promotes the osteogenic differentiation of ADSCs and enhances bone regeneration. Under limitation of this study, genetic modification of ADSCs with BMP-2 could be adopted in clinical application.

Osteogenic differentiation of mesenchymal stem cells cultured on PLLA scaffold coated with Wharton's Jelly

Poly-L-lactic acid (PLLA) electrospun nanofiber scaffold is one of the most commonly used synthetic polymer scaffolds for bone tissue engineering application. However, PLLA is hydrophobic in nature, hence does not maintain proper cell adhesion and tissue formation, moreover, it cannot provide the osteo-inductive environment due to inappropriate surface characteristic and the lack of surface motives participating in the first cellular events. To modify these shortcomings different approaches have been used, among those the most commonly used one is coating of the surface of the electrospun nanofiber with natural materials. In this work Wharton's jelly (WJ), a tissue which surrounds the umbilical cord vessels, reaches in high amounts of extracellular matrix (ECM) components mainly; collagen, hyaluronic acid and several sulphated glycosaminoglycans (GAGs) were used to cover the surface of electrospun PLLA nanofiber scaffolds. The surface morphology of the nanofiber scaffold was evaluated via scanning electron microscope, and the in vitro osteogenic differentiation potential was determined by MTT assay and common osteogenic marker tests such as alkaline phosphatase (ALP) activity and calcium deposition tests. Coating of WJ could not change the surface morphology and diameter of the nanofibers. However, WJ-PLLA scaffolds showed higher proliferation of human mesenchymal stem cells (MSC) than tissue culture plate (TCP) and pristine PLLA scaffolds, moreover, WJ-PPLA scaffold demonstrated significant alkaline phosphatase activity and calcium mineralization than either TCP or PLLA nanofiber scaffolds.

κ-Carrageenan Enhances the Biomineralization and Osteogenic Differentiation of Electrospun Polyhydroxybutyrate and Polyhydroxybutyrate Valerate Fibers

Novel electrospun materials for bone tissue engineering were obtained by blending biodegradable polyhydroxybutyrate (PHB) or polyhydroxybutyrate valerate (PHBV) with the anionic sulfated polysaccharide κ-carrageenan (κ-CG) in varying ratios. In both systems, the two components phase separated as shown by FTIR, DSC and TGA. According to the contact angle data, κ-CG was localized preferentially at the fiber surface in PHBV/κ-CG blends in contrast to PHB/κ-CG, where the biopolymer was mostly found within the fiber. In contrast to the neat polyester fibers, the blends led to the formation of much smaller apatite crystals (800 nm vs 7 μm). According to the MTT assay, NIH3T3 cells grew in higher density on the blend mats in comparison to neat polyester mats. The osteogenic differentiation potential of the fibers was determined by SaOS-2 cell culture for 2 weeks. Alizarin red-S staining suggested an improved mineralization on the blend fibers. Thus, PHBV/κ-CG fibers resulted in more pronounced bioactive and osteogenic properties, including fast apatite-forming ability and deposition of nanosized apatite crystals.

Nanotechnology in orthopedics

Nanotechnology has revolutionized science and consumer products for several decades. Most recently, its applications to the fields of medicine and biology have improved drug delivery, medical diagnostics, and manufacturing. Recent research of this modern technology has demonstrated its potential with novel forms of disease detection and intervention, particularly within orthopedics. Nanomedicine has transformed orthopedics through recent advances in bone tissue engineering, implantable materials, diagnosis and therapeutics, and surface adhesives. The potential for nanotechnology within the field of orthopedics is vast and much of it appears to be untapped, though not without accompanying obstacles.

Development and characterization of heparin-immobilized polycaprolactone nanofibrous scaffolds for tissue engineering using gamma-irradiation

Polycaprolactone (PCL) has been considered a useful material for orthopedic devices and osseous implants because of its biocompatibility and bone-forming activity.

Osteogenic and tenogenic induction of hBMSCs by an integrated nanofibrous scaffold with chemical and structural mimicry of the bone–ligament connection

A novel electrospinning nanofiber collecting device was designed and utilized to fabricate an integrated PCL nanofibrous scaffold with a “random–aligned–random” structure.

Poly (lactic acid)-based biomaterials for orthopaedic regenerative engineering

Regenerative engineering converges tissue engineering, advanced materials science, stem cell science, and developmental biology to regenerate complex tissues such as whole limbs. Regenerative engineering scaffolds provide mechanical support and nanoscale control over architecture, topography, and biochemical cues to influence cellular outcome. In this regard, poly (lactic acid) (PLA)-based biomaterials may be considered as a gold standard for many orthopaedic regenerative engineering applications because of their versatility in fabrication, biodegradability, and compatibility with biomolecules and cells. Here we discuss recent developments in PLA-based biomaterials with respect to processability and current applications in the clinical and research settings for bone, ligament, meniscus, and cartilage regeneration.

Growth factor-eluting technologies for bone tissue engineering

Growth factors are essential orchestrators of the normal bone fracture healing response. For non-union defects, delivery of exogenous growth factors to the injured site significantly improves healing outcomes. However, current clinical methods for scaffold-based growth factor delivery are fairly rudimentary, and there is a need for greater spatial and temporal regulation to increase their in vivo efficacy. Various approaches used to provide spatiotemporal control of growth factor delivery from bone tissue engineering scaffolds include physical entrapment, chemical binding, surface modifications, biomineralization, micro- and nanoparticle encapsulation, and genetically engineered cells. Here, we provide a brief review of these technologies, describing the fundamental mechanisms used to regulate release kinetics. Examples of their use in pre-clinical studies are discussed, and their capacities to provide tunable, growth factor delivery are compared. These advanced scaffold systems have the potential to provide safer, more effective therapies for bone regeneration than the systems currently employed in the clinic.

Laminated electrospun nHA/PHB-composite scaffolds mimicking bone extracellular matrix for bone tissue engineering

Electrospinning is an effective means to generate nano- to micro-scale polymer fibers resembling native extracellular matrix for tissue engineering. However, a major problem of electrospun materials is that limited pore size and porosity may prevent adequate cellular infiltration and tissue ingrowth. In this study, we first prepared thin layers of hydroxyapatite nanoparticle (nHA)/poly-hydroxybutyrate (PHB) via electrospinning. We then laminated the nHA/PHB thin layers to obtain a scaffold for cell seeding and bone tissue engineering. The results demonstrated that the laminated scaffold possessed optimized cell-loading capacity. Bone marrow mesenchymal stem cells (MSCs) exhibited better adherence, proliferation and osteogenic phenotypes on nHA/PHB scaffolds than on PHB scaffolds. Thereafter, we seeded MSCs onto nHA/PHB scaffolds to fabricate bone grafts. Histological observation showed osteoid tissue formation throughout the scaffold, with most of the scaffold absorbed in the specimens 2months after implantation, and blood vessels ingrowth into the graft could be observed in the graft. We concluded that electrospun and laminated nanoscaled biocomposite scaffolds hold great therapeutic potential for bone regeneration.

PDLLA honeycomb-like scaffolds with a high loading of superhydrophilic graphene/multi-walled carbon nanotubes promote osteoblast in vitro functions and guided in vivo bone regeneration

Herein, we developed honeycomb-like scaffolds by combining poly (d, l-lactic acid) (PDLLA) with a high amount of graphene/multi-walled carbon nanotube oxides (MWCNTO-GO, 50% w/w). From pristine multi-walled carbon nanotubes (MWCNT) powders, we produced MWCNTO-GO via oxygen plasma etching (OPE), which promoted their exfoliation and oxidation. Initially, we evaluated PDLLA and PDLLA/MWCNTO-GO scaffolds for tensile strength tests, cell adhesion and cell viability (with osteoblast-like MG-63 cells), alkaline phosphatase (ALP, a marker of osteoblast differentiation) activity and mineralized nodule formation. In vivo tests were carried out using PDLLA and PDLLA/MWCNTO-GO scaffolds as fillers for critical defects in the tibia of rats. MWCNTO-GO loading was responsible for decreasing the tensile strength and elongation-at-break of PDLLA scaffolds, although the high mechanical performance observed (~600MPa) assures their application in bone tissue regeneration. In vitro results showed that the scaffolds were not cytotoxic and allowed for osteoblast-like cell interactions and the formation of mineralized matrix nodules. Furthermore, MG-63 cells grown on PDLLA/MWCNTO-GO significantly enhanced osteoblast ALP activity compared to controls (cells alone), while the PDLLA group showed similar ALP activity when compared to controls and PDLLA/MWCNTO-GO. Most impressively, in vivo tests suggested that compared to PDLLA scaffolds, PDLLA/MWCNTO-GO had a superior influence on bone cell activity, promoting greater new bone formation. In summary, the results of this study highlighted that this novel scaffold (MWCNTO-GO, 50% w/w) is a promising alternative for bone tissue regeneration and, thus, should be further studied.