Conductive Scaffolds for Bone Tissue Engineering: Current State and Future Outlook

Advancements in tissue engineering for cardiovascular health: a biomedical engineering perspective

Myocardial infarction (MI) stands as a prominent contributor to global cardiovascular disease (CVD) mortality rates. Acute MI (AMI) can result in the loss of a large number of cardiomyocytes (CMs), which the adult heart struggles to replenish due to its limited regenerative capacity. Consequently, this deficit in CMs often precipitates severe complications such as heart failure (HF), with whole heart transplantation remaining the sole definitive treatment option, albeit constrained by inherent limitations. In response to these challenges, the integration of bio-functional materials within cardiac tissue engineering has emerged as a groundbreaking approach with significant potential for cardiac tissue replacement. Bioengineering strategies entail fortifying or substituting biological tissues through the orchestrated interplay of cells, engineering methodologies, and innovative materials. Biomaterial scaffolds, crucial in this paradigm, provide the essential microenvironment conducive to the assembly of functional cardiac tissue by encapsulating contracting cells. Indeed, the field of cardiac tissue engineering has witnessed remarkable strides, largely owing to the application of biomaterial scaffolds. However, inherent complexities persist, necessitating further exploration and innovation. This review delves into the pivotal role of biomaterial scaffolds in cardiac tissue engineering, shedding light on their utilization, challenges encountered, and promising avenues for future advancement. By critically examining the current landscape, we aim to catalyze progress toward more effective solutions for cardiac tissue regeneration and ultimately, improved outcomes for patients grappling with cardiovascular ailments.

Conductive Polyisocyanide Hydrogels Inhibit Fibrosis and Promote Myogenesis

Reliable in vitro models closely resembling native tissue are urgently needed for disease modeling and drug screening applications. Recently, conductive biomaterials have received increasing attention in the development of in vitro models as they permit exogenous electrical signals to guide cells toward a desired cellular response. Interestingly, they have demonstrated that they promote cellular proliferation and adhesion even without external electrical stimulation. This paper describes the development of a conductive, fully synthetic hydrogel based on hybrids of the peptide-modified polyisocyanide (PIC-RGD) and the relatively conductive poly(aniline-co-N-(4-sulfophenyl)aniline) (PASA) and its suitability as the in vitro matrix. We demonstrate that incorporating PASA enhances the PIC-RGD hydrogel's electroactive nature without significantly altering the fibrous architecture and nonlinear mechanics of the PIC-RGD network. The biocompatibility of our model was assessed through phenotyping cultured human foreskin fibroblasts (HFF) and murine C2C12 myoblasts. Immunofluorescence analysis revealed that PIC-PASA hydrogels inhibit the fibrotic behavior of HFFs while promoting myogenesis in C2C12 cells without electrical stimulation. The composite PIC-PASA hydrogel can actively change the cell fate of different cell types, providing an attractive tool to improve skin and muscle repair.

The effect of graphene and graphene oxide induced reactive oxygen species on polycaprolactone scaffolds for bone cancer applications

Bone cancer remains a critical healthcare problem. Among current clinical treatments, tumour resection is the most common strategy. It is usually effective but may present several limitations such as multiple operations, long hospital time, and the potential recurrence caused by the incomplete removal of cancer cells. To address these limitations, three-dimensional (3D) scaffolds fabricated through additive manufacturing have been researched for both bone cancer treatment and post-treatment rehabilitation. Polycaprolactone (PCL)-based scaffolds play an important role in bone regeneration, serving as a physical substrate to fill the defect site, recruiting cells, and promoting cell proliferation and differentiation, ultimately leading to the regeneration of the bone tissue without multiple surgical applications. Multiple advanced materials have been incorporated during the fabrication process to improve certain functions and/or modulate biological performances. Graphene-based nanomaterials, particularly graphene (G) and graphene oxide (GO), have been investigated both in vitro and in vivo, significantly improving the scaffold's physical, chemical, and biological properties, which strongly depend on the material type and concentration. A unique targeted inhibition effect on cancer cells was also discovered. However, limited research has been conducted on utilising graphene-based nanomaterials for both bone regeneration and bone cancer treatment, and there is no systematic study into the material- and dose-dependent effects, as well as the working mechanism on 3D scaffolds to realise these functions. This paper addresses these limitations by designing and fabricating PCL-based scaffolds containing different concentrations of G and GO and assessing their biological behaviour correlating it to the reactive oxygen species (ROS) release level. Results suggest that the ROS release from the scaffolds is a dominant mechanism that affects the biological behaviour of the scaffolds. ROS release also contributes to the inhibition effect on bone cancer due to healthy cells and cancer cells responding differently to ROS, and the osteogenesis results also present a certain correlation with ROS. These observations revealed a new route for realising bone cancer treatment and subsequent new bone regeneration, using a single dual-functional 3D scaffold.

Chitosan nanocomposite for tissue engineering and regenerative medicine: A review

Regenerative medicine and tissue engineering have emerged as a multidisciplinary promising field in the quest to address the limitations of traditional medical approaches. One of the key aspects of these fields is the development of such types of biomaterials that can mimic the extracellular matrix and provide a conducive environment for tissue regeneration. In this regard, chitosan has played a vital role which is a naturally derived linear bi-poly-aminosaccharide, and has gained significant attention due to its biocompatibility and unique properties. Chitosan possesses many unique physicochemical properties, making it a significant polysaccharide for different applications such as agriculture, nutraceutical, biomedical, food, nutraceutical, packaging, etc. as well as significant material for developing next-generation hydrogel and bio-scaffolds for regenerative medicinal applications. Moreover, chitosan can be easily modified to incorporate desirable properties, such as improved mechanical strength, enhanced biodegradability, and controlled release of bioactive molecules. Blending chitosan with other polymers or incorporating nanoparticles into its matrix further expands its potential in tissue engineering applications. This review summarizes the most recent studies of the last 10 years based on chitosan, blends, and nanocomposites and their application in bone tissue engineering, hard tissue engineering, dental implants, dental tissue engineering, dental fillers, and cartilage tissue engineering.

Biophysical control of plasticity and patterning in regeneration and cancer

Cells and tissues display a remarkable range of plasticity and tissue-patterning activities that are emergent of complex signaling dynamics within their microenvironments. These properties, which when operating normally guide embryogenesis and regeneration, become highly disordered in diseases such as cancer. While morphogens and other molecular factors help determine the shapes of tissues and their patterned cellular organization, the parallel contributions of biophysical control mechanisms must be considered to accurately predict and model important processes such as growth, maturation, injury, repair, and senescence. We now know that mechanical, optical, electric, and electromagnetic signals are integral to cellular plasticity and tissue patterning. Because biophysical modalities underly interactions between cells and their extracellular matrices, including cell cycle, metabolism, migration, and differentiation, their applications as tuning dials for regenerative and anti-cancer therapies are being rapidly exploited. Despite this, the importance of cellular communication through biophysical signaling remains disproportionately underrepresented in the literature. Here, we provide a review of biophysical signaling modalities and known mechanisms that initiate, modulate, or inhibit plasticity and tissue patterning in models of regeneration and cancer. We also discuss current approaches in biomedical engineering that harness biophysical control mechanisms to model, characterize, diagnose, and treat disease states.

Effects of Space Dimensionality within Scaffold for Bone Regeneration with Large and Oriented Blood Vessels

The internal structure of the scaffolds is a key factor for bone regeneration. In this study, we focused on the space dimensionality within the scaffold that may control cell migration and evaluated the effects on the size and orientation of blood vessels and the amount of bone formation in the scaffold. The carbonate apatite scaffolds with intrascaffold space allowing one-dimensional (1D), two-dimensional (2D), or three-dimensional (3D) cell migration were fabricated by 3D printing. These scaffolds had the same space size, i.e., distances between the struts (~300 µm). The scaffolds were implanted into the medial condyle of rabbit femurs for four weeks. Both the size and orientation degree of the blood vessels formed in the scaffolds allowing 1D cell migration were 2.5- to 4.0-fold greater than those of the blood vessels formed in the scaffolds allowing 2D and 3D cell migration. Furthermore, the amount of bone formed in the scaffolds allowing 1D cell migration was 1.4-fold larger than that formed in the scaffolds allowing 2D and 3D cell migration. These are probably because the 1D space limited the direction of cell migration and prevented the branching of blood vessels, whereas 2D and 3D spaces provided the opportunity for random cell migration and blood vessel branching. Thus, scaffolds with 1D space are advantageous for inducing large and oriented blood vessels, resulting in a larger amount of bone formation.

Osteogenic Potential of Human Dental Pulp Stem Cells (hDPSCs) Growing on Poly L-Lactide-Co-Caprolactone and Hyaluronic Acid (HYAFF-11TM) Scaffolds

Bone tissue engineering using different scaffolds is a new therapeutic approach in regenerative medicine. This study explored the osteogenic potential of human dental pulp stem cells (hDPSCs) grown on a hydrolytically modified poly(L-lactide-co-caprolactone) (PLCL) electrospun scaffold and a non-woven hyaluronic acid (HYAFF-11™) mesh. The adhesion, immunophenotype, and osteogenic differentiation of hDPSCs seeded on PLCL and HYAFF-11™ scaffolds were analyzed. The results showed that PLCL and HYAFF-11™ scaffolds significantly supported hDPSCs adhesion; however, hDPSCs' adhesion rate was significantly higher on PLCL than on HYAFF-11™. SEM analysis confirmed good adhesion of hDPSCs on both scaffolds before and after osteogenesis. Alizarin red S staining showed mineral deposits on both scaffolds after hDPSCs osteogenesis. The mRNA levels of runt-related transcription factor 2 (Runx2), collagen type I (Coll-I), osterix (Osx), osteocalcin (Ocn), osteopontin (Opn), bone sialoprotein (Bsp), and dentin sialophosphoprotein (Dspp) gene expression and their proteins were higher in hDPSCs after osteogenic differentiation on both scaffolds compared to undifferentiated hDPSCs on PLCL and HYAFF-11™. These results showed that PLCL scaffolds provide a better environment that supports hDPSCs attachment and osteogenic differentiation than HYAFF-11™. The high mRNA of early osteogenic gene expression and mineral deposits observed after hDPSCs osteogenesis on a PLCL mat indicated its better impact on hDPSCs' osteogenic potential than that of HYAFF-11™, and hDPSC/PLCL constructs might be considered in the future as an innovative approach to bone defect repair.

Pretreatment of Mesenchymal Stem Cells with Electrical Stimulation as a Strategy to Improve Bone Tissue Engineering Outcomes

Electrical stimulation (EStim), whether used alone or in combination with bone tissue engineering (BTE) approaches, has been shown to promote bone healing. In our previous in vitro studies, mesenchymal stem cells (MSCs) were exposed to EStim and a sustained, long-lasting increase in osteogenic activity was observed. Based on these findings, we hypothesized that pretreating MSC with EStim, in 2D or 3D cultures, before using them to treat large bone defects would improve BTE treatments. Critical size femur defects were created in 120 Sprague-Dawley rats and treated with scaffold granules seeded with MSCs that were pre-exposed or not (control group) to EStim 1 h/day for 7 days in 2D (MSCs alone) or 3D culture (MSCs + scaffolds). Bone healing was assessed at 1, 4, and 8 weeks post-surgery. In all groups, the percentage of new bone increased, while fibrous tissue and CD68+ cell count decreased over time. However, these and other healing features, like mineral density, bending stiffness, the amount of new bone and cartilage, and the gene expression of osteogenic markers, did not significantly differ between groups. Based on these findings, it appears that the bone healing environment could counteract the long-term, pro-osteogenic effects of EStim seen in our in vitro studies. Thus, EStim seems to be more effective when administered directly and continuously at the defect site during bone healing, as indicated by our previous studies.

Novel Electroactive Mineralized Polyacrylonitrile/PEDOT:PSS Electrospun Nanofibers for Bone Repair Applications

Bone defect repair remains a critical challenge in current orthopedic clinical practice, as the available therapeutic strategies only offer suboptimal outcomes. Therefore, bone tissue engineering (BTE) approaches, involving the development of biomimetic implantable scaffolds combined with osteoprogenitor cells and native-like physical stimuli, are gaining widespread interest. Electrical stimulation (ES)-based therapies have been found to actively promote bone growth and osteogenesis in both in vivo and in vitro settings. Thus, the combination of electroactive scaffolds comprising conductive biomaterials and ES holds significant promise in improving the effectiveness of BTE for clinical applications. The aim of this study was to develop electroconductive polyacrylonitrile/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PAN/PEDOT:PSS) nanofibers via electrospinning, which are capable of emulating the native tissue's fibrous extracellular matrix (ECM) and providing a platform for the delivery of exogenous ES. The resulting nanofibers were successfully functionalized with apatite-like structures to mimic the inorganic phase of the bone ECM. The conductive electrospun scaffolds presented nanoscale fiber diameters akin to those of collagen fibrils and displayed bone-like conductivity. PEDOT:PSS incorporation was shown to significantly promote scaffold mineralization in vitro. The mineralized electroconductive nanofibers demonstrated improved biological performance as observed by the significantly enhanced proliferation of both human osteoblast-like MG-63 cells and human bone marrow-derived mesenchymal stem/stromal cells (hBM-MSCs). Moreover, mineralized PAN/PEDOT:PSS nanofibers up-regulated bone marker genes expression levels of hBM-MSCs undergoing osteogenic differentiation, highlighting their potential as electroactive biomimetic BTE scaffolds for innovative bone defect repair strategies.

A Free-Standing Chitosan Membrane Prepared by the Vibration-Assisted Solvent Casting Method

Much attention has been paid to the surface modification of artificial skin barriers for the treatment of skin tissue damage. Chitosan is one of the natural materials that could be characterized by its biocompatibility. A number of methods for the preparation of chitosan membranes have been described in scientific articles, including solvent casting methods. This study investigates an improved technology to produce chitosan membranes. Thus, chitosan membranes were prepared using a vibration-assisted solvent casting method. First, aqueous acetic acid was used to pretreat chitosan. Then, free-standing chitosan membranes were prepared by solvent casting on nanoporous anodized aluminum oxide (AAO) membrane templates, allowing for the solvent to evaporate. Using finite element methods, a study was obtained showing the influence of chitosan solutions of different concentrations on the fluid flow into nanopores using high-frequency excitation. The height of the nanopillars and the surface area of the chitosan membrane were also evaluated. In this study, the surface area of the chitosan membrane was found to increase by 15, 10 and 6 times compared to the original flat surface area. The newly produced nanopillared chitosan membranes will be applicable in the fabrication of skin barriers due to the longer nanopillars on their surface and the larger surface area.

Intervertebral disc degeneration-Current therapeutic options and challenges

Degeneration of the intervertebral disc (IVD) is a normal part of aging. Due to the spine's declining function and the development of pain, it may affect one's physical health, mental health, and socioeconomic status. Most of the intervertebral disc degeneration (IVDD) therapies today focus on the symptoms of low back pain rather than the underlying etiology or mechanical function of the disc. The deteriorated disc is typically not restored by conservative or surgical therapies that largely focus on correcting symptoms and structural abnormalities. To enhance the clinical outcome and the quality of life of a patient, several therapeutic modalities have been created. In this review, we discuss genetic and environmental causes of IVDD and describe promising modern endogenous and exogenous therapeutic approaches including their applicability and relevance to the degeneration process.

A propitious role of marine sourced polysaccharides: Drug delivery and biomedical applications

Numerous compounds, with extensive applications in biomedical and biotechnological fields, are present in the oceans, which serve as a prime renewable source of natural substances, further promoting the development of novel medical systems and devices. Polysaccharides are present in the marine ecosystem in abundance, promoting minimal extraction costs, in addition to their solubility in extraction media, and an aqueous solvent, along with their interactions with biological compounds. Certain algae-derived polysaccharides include fucoidan, alginate, and carrageenan, while animal-derived polysaccharides comprise hyaluronan, chitosan and many others. Furthermore, these compounds can be modified to facilitate their processing into multiple shapes and sizes, as well as exhibit response dependence to external conditions like temperature and pH. All these properties have promoted the use of these biomaterials as raw materials for the development of drug delivery carrier systems (hydrogels, particles, capsules). The present review enlightens marine polysaccharides providing its sources, structures, biological properties, and its biomedical applications. In addition to this, their role as nanomaterials is also portrayed by the authors, along with the methods employed to develop them and associated biological and physicochemical properties designed to develop suitable drug delivery systems.

Graphite nanopowder incorporated xanthan gum scaffold for effective bone tissue regeneration purposes with improved biomineralization

In the current work, biomaterial composed of Xanthan gum and Diethylene glycol dimethacrylate with impregnation of graphite nanopowder filler in their matrices was fabricated successfully for their potential usage in the engineering of bone defects. Various physicochemical properties associated with the biomaterial were characterized using FTIR, XRD, TGA, SEM etc. The biomaterial rheological studies imparted the better notable properties associated with the inclusion of graphite nanopowder. The biomaterial synthesized exhibited a controlled drug release. Adhesion and proliferation of different secondary cell lines do not generate ROS on the current biomaterial and thus show its biocompatibility and non-toxic nature. The synthesized biomaterial's osteogenic potential on SaOS-2 cells was supported by increased ALP activity, enhanced differentiation and biomineralization under osteoinductive circumstances. The current biomaterial demonstrates that in addition to the drug-delivery applications, it can also be a cost-effective substrate for cellular activities and has all the necessary properties to be considered as a promising alternative material suitable for repairing and restoring bone tissues. We propose that this biomaterial may have commercial importance in the biomedical field.

Eggshell Membrane as a Biomaterial for Bone Regeneration

The physicochemical features of the avian eggshell membrane play an essential role in the process of calcium carbonate deposition during shell mineralization, giving rise to a porous mineralized tissue with remarkable mechanical properties and biological functions. The membrane could be useful by itself or as a bi-dimensional scaffold to build future bone-regenerative materials. This review focuses on the biological, physical, and mechanical properties of the eggshell membrane that could be useful for that purpose. Due to its low cost and wide availability as a waste byproduct of the egg processing industry, repurposing the eggshell membrane for bone bio-material manufacturing fulfills the principles of a circular economy. In addition, eggshell membrane particles have has the potential to be used as bio-ink for 3D printing of tailored implantable scaffolds. Herein, a literature review was conducted to ascertain the degree to which the properties of the eggshell membrane satisfy the requirements for the development of bone scaffolds. In principle, it is biocompatible and non-cytotoxic, and induces proliferation and differentiation of different cell types. Moreover, when implanted in animal models, it elicits a mild inflammatory response and displays characteristics of stability and biodegradability. Furthermore, the eggshell membrane possesses a mechanical viscoelastic behavior comparable to other collagen-based systems. Overall, the biological, physical, and mechanical features of the eggshell membrane, which can be further tuned and improved, make this natural polymer suitable as a basic component for developing new bone graft materials.

3D bioprinting of human mesenchymal stem cells-laden hydrogels incorporating MXene for spontaneous osteodifferentiation

Contemporary advances in three-dimensional (3D) bioprinting technologies have enabled the fabrication of tailored live 3D tissue mimetics. Furthermore, the development of advanced bioink materials has been highlighted to accurately reproduce the composition of a native extracellular matrix and mimic the intrinsic properties of laden cells. Recent research has shown that MXene is one of promising nanobiomaterials with osteogenic activity for bone grafts and scaffolds due to its unique atomic structure of three titanium layers between two carbon layers. In this study, the MXene-incorporated gelatin methacryloyl (GelMA) and hyaluronic acid methacryloyl (HAMA) (i.e., GelMA/HAMA-MXene) bioinks were prepared to explore if they have the potential to enable the spontaneous osteodifferentiation of human mesenchymal stem cells (hMSCs) when the hMSCs-laden GelMA/HAMA-MXene bioinks were 3D printed. The physicochemical and rheological characteristics of the GelMA/HAMA-MXene hydrogels were proven to be unprecedentedly favorable supportive matrices suited for the growth and survival of hMSCs. Furthermore, hMSCs were shown to spontaneously differentiate into osteoblasts within GelMA-HAMA/MXene composites to provide favorable microenvironments for osteogenesis. Therefore, our results suggest that the remarkable biofunctional advantages of the MXene-incorporated GelMA/HAMA bioink can be utilized in a wide range of strategies for the development of effective scaffolds in bone tissue regeneration.

3D-Printed conductive polymeric scaffolds with direct current electrical stimulation for enhanced bone regeneration

Various methods have been used to treat bone defects caused by genetic disorders, injury, or disease. Yet, there is still great need to develop alternative approaches to repair damaged bone tissue. Bones naturally exhibit piezoelectric potential, or the ability to convert mechanical stresses into electrical impulses. This phenomenon has been utilized clinically to enhance bone regeneration in conjunction with electrical stimulation (ES) therapies; however, oftentimes with critical-sized bone defects, the bioelectric potential at the site of injury is compromised, resulting in less desirable outcomes. In the present study, the potential of a 3D-printed conductive polymer blend to enhance bone formation through restoration of the bioelectrical microenvironment was evaluated. A commercially available 3D printer was used to create circular, thin-film scaffolds consisting of either polylactide (PLA) or a conductive PLA (CPLA) composite. Preosteoblast cells were seeded onto the scaffolds and subjected to direct current ES via a purpose-built cell culture chamber. It was found that CPLA scaffolds had no adverse effects on cell viability, proliferation or differentiation when compared with control scaffolds. The addition of ES, however, resulted in a significant increase in the expression of osteocalcin, a protein indicative of osteoblast maturation, after 14 days of culture. Furthermore, xylenol orange staining also showed the presence of increased mineralized calcium nodules in cultures undergoing stimulation. This study demonstrates the potential for low-cost, conductive scaffolding materials to support cell viability and enhance in vitro mineralization in conjunction with ES.

Hydrogel scaffolds in bone regeneration: Their promising roles in angiogenesis

Bone tissue engineering (BTE) has become a hopeful potential treatment strategy for large bone defects, including bone tumors, trauma, and extensive fractures, where the self-healing property of bone cannot repair the defect. Bone tissue engineering is composed of three main elements: progenitor/stem cells, scaffold, and growth factors/biochemical cues. Among the various biomaterial scaffolds, hydrogels are broadly used in bone tissue engineering owing to their biocompatibility, controllable mechanical characteristics, osteoconductive, and osteoinductive properties. During bone tissue engineering, angiogenesis plays a central role in the failure or success of bone reconstruction via discarding wastes and providing oxygen, minerals, nutrients, and growth factors to the injured microenvironment. This review presents an overview of bone tissue engineering and its requirements, hydrogel structure and characterization, the applications of hydrogels in bone regeneration, and the promising roles of hydrogels in bone angiogenesis during bone tissue engineering.

The Role of Microsphere Structures in Bottom-Up Bone Tissue Engineering

Bone defects have caused immense healthcare concerns and economic burdens throughout the world. Traditional autologous allogeneic bone grafts have many drawbacks, so the emergence of bone tissue engineering brings new hope. Bone tissue engineering is an interdisciplinary biomedical engineering method that involves scaffold materials, seed cells, and "growth factors". However, the traditional construction approach is not flexible and is unable to adapt to the specific shape of the defect, causing the cells inside the bone to be unable to receive adequate nourishment. Therefore, a simple but effective solution using the "bottom-up" method is proposed. Microspheres are structures with diameters ranging from 1 to 1000 µm that can be used as supports for cell growth, either in the form of a scaffold or in the form of a drug delivery system. Herein, we address a variety of strategies for the production of microspheres, the classification of raw materials, and drug loading, as well as analyze new strategies for the use of microspheres in bone tissue engineering. We also consider new perspectives and possible directions for future development.

Bioresorbable Chitosan-Based Bone Regeneration Scaffold Using Various Bioceramics and the Alteration of Photoinitiator Concentration in an Extended UV Photocrosslinking Reaction

Bone tissue engineering (BTE) is an ongoing field of research based on clinical needs to treat delayed and non-union long bone fractures. An ideal tissue engineering scaffold should have a biodegradability property matching the rate of new bone turnover, be non-toxic, have good mechanical properties, and mimic the natural extracellular matrix to induce bone regeneration. In this study, biodegradable chitosan (CS) scaffolds were prepared with combinations of bioactive ceramics, namely hydroxyapatite (HAp), tricalcium phosphate-α (TCP- α), and fluorapatite (FAp), with a fixed concentration of benzophenone photoinitiator (50 µL of 0.1% (w/v)) and crosslinked using a UV curing system. The efficacy of the one-step crosslinking reaction was assessed using swelling and compression testing, SEM and FTIR analysis, and biodegradation studies in simulated body fluid. Results indicate that the scaffolds had comparable mechanical properties, which were: 13.69 ± 1.06 (CS/HAp), 12.82 ± 4.10 (CS/TCP-α), 13.87 ± 2.9 (CS/HAp/TCP-α), and 15.55 ± 0.56 (CS/FAp). Consequently, various benzophenone concentrations were added to CS/HAp formulations to determine their effect on the degradation rate. Based on the mechanical properties and degradation profile of CS/HAp, it was found that 5 µL of 0.1% (w/v) benzophenone resulted in the highest degradation rate at eight weeks (54.48% degraded), while maintaining compressive strength between (4.04 ± 1.49 to 10.17 ± 4.78 MPa) during degradation testing. These results indicate that incorporating bioceramics with a suitable photoinitiator concentration can tailor the biodegradability and load-bearing capacity of the scaffolds.

NiFe2O4/ZnO-coated Poly(L-Lactide) nanofibrous scaffold enhances osteogenic differentiation of human mesenchymal stem cells

Background: A combination of bioceramics and polymeric materials has attracted the research community’s interest in bone tissue engineering. These composites are essential to support cell attachment, proliferation, and osteogenesis differentiation, which are vital as a classic strategy in bone tissue engineering. In this study, NiFe2O4/ZnO-coated poly L-Lactide (PLLA) was employed as a scaffold to evaluate the osteogenic differentiation capability of human adipose tissue derived mesenchymal stem cells (hAMSCs).

Material and methods: The electrospun PLLA nanofibers were fabricated, coated with nanocomposite (NiFe2O4/ZnO), and evaluated by the water contact angle (WCA), tensile test, attenuated total reflectance fourier-transform infrared (ATR-FTIR) and scanning electron microscopy (SEM). Then, the osteogenic differentiation potential of hAMSCs was assessed using NiFe2O4/ZnO-coated PLLA compared to tissue culture plastic (TCP) and a simple scaffold (PLLA) in vitro conditions.

Results: The adhesion, proliferation, and differentiation of hAMSCs were supported by the mechanical and biological properties of the NiFe2O4/ZnO-coated PLLA scaffold, according to SEM and 4′,6-Diamidino-2-phenylindole dihydrochloride (DAPI) staining patterns. During bone differentiation, Alkaline phosphatase (ALP) enzyme activity, biomineralization, calcium content, and osteogenic gene expression (ALP, Osteonectin, Osteocalcin, Collagen type I, and Runx2) were higher on NiFe2O4/ZnO-coated PLLA scaffold than on PLLA scaffold and TCP.

Conclusion: Based on our results, the osteogenic differentiation of hAMSCs on the improved biological scaffold (PLLA coated with NiFe2O4/ZnO) could accelerate due to the stimulating effect of this nanocomposite.

Could Curdlan/Whey Protein Isolate/Hydroxyapatite Biomaterials Be Considered as Promising Bone Scaffolds?-Fabrication, Characterization, and Evaluation of Cytocompatibility towards Osteoblast Cells In Vitro

The number of bone fractures and cracks requiring surgical interventions increases every year; hence, there is a huge need to develop new potential bone scaffolds for bone regeneration. The goal of this study was to gain knowledge about the basic properties of novel curdlan/whey protein isolate/hydroxyapatite biomaterials in the context of their use in bone tissue engineering. The purpose of this research was also to determine whether the concentration of whey protein isolate in scaffolds has an influence on their properties. Thus, two biomaterials differing in the concentration of whey protein isolate (i.e., 25 wt.% and 35 wt.%; hereafter called Cur_WPI25_HAp and Cur_WPI35_HAp, respectively) were fabricated and subjected to evaluation of porosity, mechanical properties, swelling ability, protein release capacity, enzymatic biodegradability, bioactivity, and cytocompatibility towards osteoblasts in vitro. It was found that both biomaterials fulfilled a number of requirements for bone scaffolds, as they demonstrated limited swelling and the ability to undergo controllable enzymatic biodegradation, to form apatite layers on their surfaces and to support the viability, growth, proliferation, and differentiation of osteoblasts. On the other hand, the biomaterials were characterized by low open porosity, which may hinder the penetration of cells though their structure. Moreover, they had low mechanical properties compared to natural bone, which limits their use to filling of bone defects in non-load bearing implantation areas, e.g., in the craniofacial area, but then they will be additionally supported by application of mechanically strong materials such as titanium plates. Thus, this preliminary in vitro research indicates that biomaterials composed of curdlan, whey protein isolate, and hydroxyapatite seem promising for bone tissue engineering applications, but their porosity and mechanical properties should be improved. This will be the subject of our further work.

A Review of Woven Tracheal Stents: Materials, Structures, and Application

The repair and reconstruction of tracheal defects is a challenging clinical problem. Due to the wide choice of materials and structures, weaving technology has shown unique advantages in simulating the multilayer structure of the trachea and providing reliable performance. Currently, most woven stent-based stents focus only on the effect of materials on stent performance while ignoring the direct effect of woven process parameters on stent performance, and the advantages of weaving technology in tissue regeneration have not been fully exploited. Therefore, this review will introduce the effects of stent materials and fabric construction on the performance of tracheal stents, focusing on the effects of weaving process parameters on stent performance. We will summarize the problems faced by woven stents and possible directions of development in the hope of broadening the technical field of artificial trachea preparation.

Recent advancement in polymer/halloysite nanotube nanocomposites for biomedical applications

Halloysite nanotubes (HNTs) have recently been the subject of extensive research as a reinforcing filler. HNT is a natural nanoclay, non-toxic and biocompatible, hence, applicable in biomedical fields. This review focuses on the mechanical, thermal, and functional properties of polymer nanocomposites with HNT as a reinforcing agent from an experimental and theoretical perspective. In addition, this review also highlights the recent applications of polymer/HNT nanocomposites in the biomedical fields.

Mesenchymal Stem Cells–Hydrogel Microspheres System for Bone Regeneration in Calvarial Defects

The repair of large bone defects in clinic is a challenge and urgently needs to be solved. Tissue engineering is a promising therapeutic strategy for bone defect repair. In this study, hydrogel microspheres (HMs) were fabricated to act as carriers for bone marrow mesenchymal stem cells (BMSCs) to adhere and proliferate. The HMs were produced by a microfluidic system based on light-induced gelatin of gelatin methacrylate (GelMA). The HMs were demonstrated to be biocompatible and non-cytotoxic to stem cells. More importantly, the HMs promoted the osteogenic differentiation of stem cells. In vivo, the ability of bone regeneration was studied by way of implanting a BMSC/HM system in the cranial defect of rats for 8 weeks. The results confirmed that the BMSC/HM system can induce superior bone regeneration compared with both the HMs alone group and the untreated control group. This study provides a simple and effective research idea for bone defect repair, and the subsequent optimization study of HMs will provide a carrier material with application prospects for tissue engineering in the future.

Structural Characterization Analyses of Low Brass Filler Biomaterial for Hard Tissue Implanted Scaffold Applications

A biomaterial was created for hard tissue implanted scaffolds as a translational therapeutic approach. The existing biomaterials containing titanium dioxide filler posed a risk of oxygen gas vacancy. This will block the canaliculars, leading to a limit on the nutrient fluid supply. To overcome this problem, low brass was used as an alternative filler to eliminate the gas vacancy. Low brass with composition percentages of 0%, 2%, 5%, 15%, and 30% was filled into the polyester urethane liquidusing the metallic filler polymer reinforced method. The structural characterizations of the low brass filler biomaterial were investigated by Field Emission Scanning Electron Microscopy. The results showed the surface membrane strength was higher than the side and cross-section. The composition shapes found were hexagon for polyester urethane and peanut for low brass. Low brass stabilised polyester urethane in biomaterials by the formation of two 5-ringed tetrahedral crystal structures. The average pore diameter was 308.9 nm, which is suitable for articular cartilage cells. The pore distribution was quite dispersed, and its curve had a linear relationship between area and diameter, suggestive of the sphere-shaped pores. The average porosities were different between using FESEM results of 6.04% and the calculated result of 3.28%. In conclusion, this biomaterial had a higher surface membrane strength and rather homogeneous dispersed pore structures.