Bioactive Three-Dimensional Graphene Oxide Foam/Polydimethylsiloxane/Zinc Silicate Scaffolds with Enhanced Osteoinductivity for Bone Regeneration

Injectable Polyhydroxyalkanoate-Nano-Clay Microcarriers Loaded with r-BMSCs Enhance the Repair of Cranial Defects in Rats

Purpose

Successful regeneration of cranial defects necessitates the use of porous bone fillers to facilitate cell proliferation and nutrient diffusion. Open porous microspheres, characterized by their high specific surface area and osteo-inductive properties, offer an optimal microenvironment for cell ingrowth and efficient ossification, potentially accelerating bone regeneration.

Materials and Methods

An in vitro investigation was conducted to assess the physicochemical properties, porosity, and biocompatibility of PHA-nano-clay open porous microspheres. Subsequently, PHA-nano-clay microspheres loaded with rat bone marrow mesenchymal stem cells were implanted into 5 mm cranial defects in rats for a duration of 12 weeks and were evaluated through histological and immunohistochemical analyses.

Results

The incorporation of nano-clay into PHA resulted in improved mechanical properties of the porous scaffolds. Furthermore, cell adhesion, viability, and morphology on the scaffolds were maintained. The PHA-3% nano-clay open porous microspheres effectively enhanced the repair of cranial defects compared to the control group, without recurrence or complications.

Conclusion

Porous PHA-nano-clay microspheres, with their high specific surface area, biodegradability, and osteo-inductive properties, can be utilized as a bone-filling material for improved bone defect repair through cell delivery. In particular, PHA-3% nano-clay open porous microspheres exhibit promising therapeutic potential in the repair of cranial defects.

Application of loaded graphene oxide biomaterials in the repair and treatment of bone defects

Addressing bone defects is a complex medical challenge that involves dealing with various skeletal conditions, including fractures, osteoporosis (OP), bone tumours, and bone infection defects. Despite the availability of multiple conventional treatments for these skeletal conditions, numerous limitations and unresolved issues persist. As a solution, advancements in biomedical materials have recently resulted in novel therapeutic concepts. As an emerging biomaterial for bone defect treatment, graphene oxide (GO) in particular has gained substantial attention from researchers due to its potential applications and prospects. In other words, GO scaffolds have demonstrated remarkable potential for bone defect treatment. Furthermore, GO-loaded biomaterials can promote osteoblast adhesion, proliferation, and differentiation while stimulating bone matrix deposition and formation. Given their favourable biocompatibility and osteoinductive capabilities, these materials offer a novel therapeutic avenue for bone tissue regeneration and repair. This comprehensive review systematically outlines GO scaffolds' diverse roles and potential applications in bone defect treatment.

ECM-inspired calcium/zinc laden cellulose scaffold for enhanced bone regeneration

Cellulose-based polymer scaffolds are highly diverse for designing and fabricating artificial bone substitutes. However, realizing the multi-biological functions of cellulose-based scaffolds has long been challenging. In this work, inspired by the structure and function of the extracellular matrix (ECM) of bone, we developed a novel yet feasible strategy to prepare ECM-like scaffolds with hybrid calcium/zinc mineralization. The 3D porous structure was formed via selective oxidation and freeze drying of bacterial cellulose. Following the principle of electrostatic interaction, calcium/zinc hybrid hydroxyapatite nucleated, crystallized, and precipitated on the 3D scaffold in simulated physiological conditions, which was well confirmed by morphology and composition analysis. Compared with alternative scaffold cohorts, this hybrid ion-loaded cellulose scaffold exhibited a pronounced elevation in alkaline phosphatase (ALP) activity, osteogenic gene expression, and cranial defect regeneration. Notably, the hybrid ion-loaded cellulose scaffold effectively fostered an M2 macrophage milieu and had a strong immune effect in vivo. In summary, this study developed a hybrid multifunctional cellulose-based scaffold that appropriately simulates the ECM to regulate immunomodulatory and osteogenic differentiation, setting a measure for artificial bone substitutes.

Mechanistic insights into the spontaneous induction of bone formation

The grand discovery of morphogens, or "form-generating substances", revealed that tissue morphogenesis is initiated by soluble molecular signals or morphogens primarily belonging to the transforming growth factor-β (TGF-β) supergene family. The regenerative potential of bone rests on its extracellular matrix, which is the repository of several morphogens that tightly control cellular differentiating pathways, cellular matrix deposition and remodeling. Alluringly, the matrix also contains specific factors transferred from the heterotopic implanted bone matrices initiating "Tissue Induction", as provocatively described in Nature in 1945. Later, it was found that selected genes and gene products of the TGF-β supergene family singly, synchronously, and synergistically mastermind the induction of bone formation. This review describes the phenomenon of the spontaneous and/or intrinsic osteoinductivity of calcium phosphate-based biomaterials and titanium' constructs without the applications of soluble osteogenetic molecular signals. The review shows the spontaneous induction of bone formation initiated by Ca++ activating stem cell differentiation and up-regulation of bone morphogenetic proteins genes. Expressed gene products are embedded into the concavities of the calcium phosphate-based substrata, initiating bone formation as a secondary response. Pure titanium's substrata do not initiate the spontaneous induction of bone formation. The induction of bone is solely dependent on acid, alkali and heat treatments to form apatite layers on the treated titanium surfaces. The induction of bone formation is achieved exclusively by apatite-based biomaterial surfaces. The hydroxyapatite, in its various forms and geometric configurations, finely tunes the induction of bone formation in heterotopic sites. Cellular differentiation by fine-tuning of the cellular molecular machinery is initiated by specific geometric modularity of the hydroxyapatite substrata that push cellular buttons that start the ripple-like cascade of "Tissue Induction", generating newly formed ossicles with bone marrow in heterotopic extraskeletal sites. The highlighted mechanistic insights into the spontaneous induction of bone formation are a research platform invocating selected molecular elements to construct the induction of bone formation.

Exploring the Osteogenic Potential of Zinc-Doped Magnesium Phosphate Cement (ZMPC): A Novel Material for Orthopedic Bone Defect Repair

In orthopedics, the repair of bone defects remains challenging. In previous research reports, magnesium phosphate cements (MPCs) were widely used because of their excellent mechanical properties, which have been widely used in the field of orthopedic medicine. We built a new k-struvite (MPC) cement obtained from zinc oxide (ZnO) and assessed its osteogenic properties. Zinc-doped magnesium phosphate cement (ZMPC) is a novel material with good biocompatibility and degradability. This article summarizes the preparation method, physicochemical properties, and biological properties of ZMPC through research on this material. The results show that ZMPC has the same strength and toughness (25.3 ± 1.73 MPa to 20.18 ± 2.11 MPa), that meet the requirements of bone repair. Furthermore, the material can gradually degrade (12.27% ± 1.11% in 28 days) and promote osteogenic differentiation (relative protein expression level increased 2-3 times) of rat bone marrow mesenchymal stem cells (rBMSCs) in vitro. In addition, in vivo confirmation revealed increased bone regeneration in a rat calvarial defect model compared with MPC alone. Therefore, ZMPC has broad application prospects and is expected to be an important repair material in the field of orthopedic medicine.

Mussel-inspired cortical bone-adherent bioactive composite hydrogels promote bone augmentation through sequential regulation of endochondral ossification

Endochondral ossification (ECO) plays an integral part in bone augmentation, which undergoes sequential processes including mesenchymal stem cells (MSC) condensation, chondrocyte differentiation, chondrocyte hypertrophy, and mineralized bone formation. Thus, accelerating these steps will speed up the osteogenesis process through ECO. Herein, inspired by the marine mussels' adhesive mechanism, a bioactive glass-dopamine (BG-Dopa) hydrogel was prepared by distributing the micro-nano BG to aldehyde modified hyaluronic acid with dopamine-modified gelatin. By in vitro and in vivo experiments, we confirm that after implanting in the bone augmentation position, the hydrogel can adhere to the cortical bone surface firmly without sliding. Moreover, the condensation and hypertrophy of stem cells were accelerated at the early stage of ECO. Whereafter, the osteogenic differentiation of the hypertrophic chondrocytes was promoted, which lead to accelerating the late stage of ECO process to achieve more bone augmentation. This experiment provides a new idea for the design of bone augmentation materials.

A scoping review of graphene-based biomaterials for in vivo bone tissue engineering

The growing demand for more efficient materials for medical applications brought together two previously distinct fields: medicine and engineering. Regenerative medicine has evolved with the engineering contributions to improve materials and devices for medical use. In this regard, graphene is one of the most promising materials for bone tissue engineering and its potential for bone repair has been studied by several research groups. The aim of this study is to conduct a scoping review including articles published in the last 12 years (from 2010 to 2022) that have used graphene and its derivatives (graphene oxide and reduced graphene) in preclinical studies for bone tissue regeneration, searching in PubMed/MEDLINE, Embase, Web of Science, Cochrane Central, and clinicaltrials.gov (to confirm no study has started with clinical trial). Boolean searches were performed using the defined key words "bone" and "graphene", and manuscript abstracts were uploaded to Rayyan, a web-tool for systematic and scoping reviews. This scoping review was conducted based on Joanna Briggs Institute Manual for Scoping Reviews and the report follows the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses - Extension for Scoping Reviews (PRISMA-ScR) statement. After the search protocol and application of the inclusion criteria, 77 studies were selected and evaluated by five blinded researchers. Most of the selected studies used composite materials associated with graphene and its derivatives to natural and synthetic polymers, bioglass, and others. Although a variety of graphene materials were analyzed in these studies, they all concluded that graphene, its derivatives, and its composites improve bone repair processes by increasing osteoconductivity, osteoinductivity, new bone formation, and angiogenesis. Thus, this systematic review opens up new opportunities for the development of novel strategies for bone tissue engineering with graphene.

The effect of GelMA/alginate interpenetrating polymeric network hydrogel on the performance of porous zirconia matrix for bone regeneration applications

Bone tissue is a natural composite, exhibiting complicated structures and unique mechanical/biological properties. With an attempt of mimicking the bone tissue, a novel inorganic-organic composite scaffolds (ZrO2-GM/SA) was designed and prepared via the vacuum infiltration method and the single/double cross-linking strategy by blending GelMA/alginate (GelMA/SA) interpenetrating polymeric network (IPN) into the porous zirconia (ZrO2) scaffold. The structure, morphology, compressive strength, surface/interface properties, and biocompatibility of the ZrO2-GM/SA composite scaffolds were characterized to evaluate the performance of the composite scaffolds. Results showed that compared to ZrO2 bare scaffolds with well-defined open pores, the composite scaffolds prepared by double cross-linking of GelMA hydrogel and sodium alginate (SA) presented a continuous, tunable and honeycomb-like microstructure. Meanwhile, GelMA/SA showed favorable and controllable water-uptake capacity, swelling property and degradability. After the introduction of IPN components, the mechanical strength of composite scaffolds was further improved. The compressive modulus of composite scaffolds was significantly higher than the bare ZrO2 scaffolds. In addition, ZrO2-GM/SA composite scaffolds had highly biocompatibility and displayed a potent proliferation and osteogenesis of MC3T3-E1 pre-osteoblasts compared to bare ZrO2 scaffolds and ZrO2-GelMA composite scaffolds. At the same time, ZrO2-10GM/1SA composite scaffold regenerated significantly greater bone than other groups in vivo. This study demonstrated that the proposed ZrO2-GM/SA composite scaffolds had great research and application potential in bone tissue engineering.

Enhanced osteogenesis on proantocyanidin-loaded date palm endocarp cellulosic matrices: A novel sustainable approach for guided bone regeneration

Developing inexpensive, biocompatible natural scaffolds that can support the differentiation and proliferation of stem cells has been recently emphasized by the research community to faster obtain the FDA approvals for regenerative medicine. In this regard, plant-derived cellulose materials are a novel class of sustainable scaffolding materials with high potentials for bone tissue engineering (BTE). However, low bioactivity of the plant-derived cellulose scaffolds restricts cell proliferation and cell differentiation. This limitation can be addressed though surface-functionalization of cellulose scaffolds with natural antioxidant polyphenols, e.g., grape seed proanthocyanidin (PCA)-rich extract (GSPE). Despite the various merits of GSPE as a natural antioxidant, its impact on the proliferation and adhesion of osteoblast precursor cells, and on their osteogenic differentiation is an as-yet unknown issue. Here, we investigated the effects of GSPE surface functionalization on the physicochemical properties of decellularized date (Phoenix dactyliferous) fruit inner layer (endocarp) (DE) scaffold. In this regard, various physiochemical characteristics of the DE-GSPE scaffold such as hydrophilicity, surface roughness, mechanical stiffness, porosity, and swelling, and biodegradation behavior were compared with those of the DE scaffold. Additionally, the impact of the GSPE treatment of the DE scaffold on the osteogenic response of human mesenchymal stem cells (hMSCs) was thoroughly studied. For this purpose, cellular activities including cell adhesion, calcium deposition and mineralization, alkaline phosphatase (ALP) activity, and expression levels of bone-related genes were monitored. Taken together, the GSPE treatment enhanced the physicochemical and biological properties of the DE-GSPE scaffold, thereby raising its potentials as a promising candidate for guided bone regeneration.

Chitosan-polyethylene oxide/clay-alginate nanofiber hydrogel scaffold for bone tissue engineering: Preparation, physical characterization, and biomimetic mineralization

This study aimed to prepare a novel organic-mineral nanofiber/hydrogel of chitosan-polyethylene oxide (CS-PEO)/nanoclay-alginate (NC-ALG). The effects of NC particles on the mineralization and biocompatibility of the scaffold were investigated. A layer-by-layer scaffold composed of CS-PEO and NC-ALG was prepared. The morphological properties, swelling, biodegradation, and mechanical behaviors of the scaffolds were evaluated. Furthermore, scaffolds were characterized by the Fourier Transform Infrared (FTIR), the Field Emission Scanning Electron Microscope (FE-SEM), and X-Ray Diffraction (XRD) techniques. Bone-like apatite formation ability of the scaffolds was determined by the mineralization test in a simulated body fluid (M-SBF). In addition, the crystalline phase of bone-like apatite precipitates was investigated by XRD analysis. The cell compatibility of the scaffolds was also studied with osteoblastic cell line MC3T3-E1 by MTT assay. Notably, the incorporation of NC particles in CS-PEO/ALG scaffolds is suitable for bone tissue regeneration which enhances bone-like apatite formation. Further, the hemolysis and MTT assays demonstrated that CS-PEO/NC-ALG scaffold was compatible and safe for MC3T3 cells.

Drug/bioactive eluting chitosan composite foams for osteochondral tissue engineering

Joint defects associated with a variety of etiologies often extend deep into the subchondral bone leading to functional impairment and joint immobility, and it is a very challenging task to regenerate the bone-cartilage interface offering significant opportunities for biomaterial-based interventions to improve the quality of life of patients. Herein drug-/bioactive-loaded porous tissue scaffolds incorporating nano-hydroxyapatite (nHAp), chitosan (CS) and either hydroxypropyl methylcellulose (HPMC) or Bombyx mori silk fibroin (SF) are fabricated through freeze drying method as subchondral bone substitute. A combination of spectroscopy and microscopy (Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and X-ray fluorescence (XRF) were used to analyze the structure of the porous biomaterials. The compressive mechanical properties of these scaffolds are biomimetic of cancellous bone tissues and capable of releasing drugs/bioactives (exemplified with triamcinolone acetonide, TA, or transforming growth factor-β1, TGF-β1, respectively) over a period of days. Mouse preosteoblast MC3T3-E1 cells were observed to adhere and proliferate on the tissue scaffolds as confirmed by the cell attachment, live-dead assay and alamarBlue™ assay. Interestingly, RT-qPCR analysis showed that the TA downregulated inflammatory biomarkers and upregulated the bone-specific biomarkers, suggesting such tissue scaffolds have long-term potential for clinical application.

Functionally gradient three-dimensional graphene foam-based polymeric scaffolds for multilayered tissue regeneration

Physiological bioengineering of multilayered tissues requires an optimized geometric organization with comparable biomechanics. Currently, polymer-reinforced three-dimensional (3D) graphene foams (GFs) are gaining interest in tissue engineering due to their unique morphology, biocompatibility, and similarity to extracellular matrixes. However, the homogeneous reinforcement of single polymers throughout a GF matrix does not provide tissue-level organization. Therefore, a triple-layered structure is developed in a GF matrix to closely mimic native tissue structures of the periodontium of the teeth. The scaffold aims to overcome the issue of layer separation, which generally occurs in multilayered structures due to the poor integration of various layers. The 3D GF matrix was reinforced with a polycaprolactone (PCL), polyvinyl alcohol (PVA), and PCL-hydroxyapatite (HA) mixture, added sequentially, via spin coating, vacuum, and hot air drying. Later, PVA was dissolved to create a middle layer, mimicking the periodontal fibers, while the layers present on either side resembled cementum and alveolar bone, respectively. Scanning electron microscopy and micro-computed tomography revealed the structure of the scaffold with internal differential porosities. The nanoindentation and tensile testing demonstrated the closeness of mechanical properties to that of native tissues. The biocompatibility was assessed by the MTT assay with MG63 cells (human osteosarcoma cells) exhibiting high adhesion and proliferation rate inside the 3D architecture. Summing up, this scaffold has the potential for enhancing the regeneration of various multilayered tissues.

Bone surface mimicked PDMS membranes stimulate osteoblasts and calcification of bone matrix

Cellular microenvironments play a crucial role in cell behavior. In addition to the biochemical cues present in the microenvironments, biophysical and biomechanical properties on surfaces have an impact on cellular functionality and eventually cellular fate. Effects of surface topography on cell behavior are being studied extensively in the literature. However, these studies often try to replicate topographical features of tissue surfaces by using techniques such as chemical etching, photolithography, and electrospinning, which may result in the loss of crucial micro- and nano- features on the tissue surfaces such as bone. This study investigates the topographical effects of bone surface by transferring its surface features onto polydimethylsiloxane (PDMS) membranes using soft lithography from a bovine femur. Our results have shown that major features on bone surfaces were successfully transferred onto PDMS using soft lithography. Osteoblast proliferation and calcification of bone matrix have significantly increased along with osteoblast-specific differentiation and maturation markers such as osteocalcin (OSC), osterix (OSX), collagen type I alpha 1 chain (COL1A1), and alkaline phosphatase (ALP) on bone surface mimicked (BSM) PDMS membranes in addition to a unidirectional alignment of osteoblast cells compared to plain PDMS surfaces. This presented bone surface mimicking method can provide a versatile native-like platform for further investigation of intracellular pathways regarding osteoblast growth and differentiation.

Fabrication of functional and nano-biocomposite scaffolds using strontium-doped bredigite nanoparticles/polycaprolactone/poly lactic acid via 3D printing for bone regeneration

Bone tissue engineering is a field to manufacture scaffolds for bone defects that cannot repair without medical interventions. Ceramic nanoparticles such as bredigite have importance roles in bone regeneration. We synthesized a novel strontium (Sr) doped bredigite (Bre) nanoparticles (BreSr) and then developed new nanocomposite scaffolds using polycaprolactone (PCL), poly lactic acid (PLA) by the 3D-printing technique. Novel functional nanoparticles were synthesized and characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS: map). The nanoparticles were uniformly distributed in the polymer matrix composites. The 3D- printed scaffolds were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), attenuated total reflection-fourier transform infrared (ATR-FTIR), degradation rate porosity, mechanical tests, apatite formation and cell culture. Degradation rate and mechanical strength were increased in the PLA/PCL/Bre-5%Sr nanocopmposite scaffolds.. Hydroxyapatite crystals were also created on the scaffold surface in the bioactivity test. The scaffolds supported viability and proliferation of human osteoblasts. Gene expression and calcium deposition in the samples containing nanoparticles indicated statistical different than the scaffolds without nanoparticles. The nanocomposite scaffolds were implanted into the critical-sized calvarial defects in rat for 3 months. The scaffolds containing Bre-Sr ceramic nanoparticles exhibited the best potential to regenerate bone tissue.

Two-Dimensional Nanomaterials beyond Graphene for Biomedical Applications

Two-dimensional (2D) nanomaterials (e.g., graphene) have shown to have a high potential in future biomedical applications due to their unique physicochemical properties such as unusual electrical conductivity, high biocompatibility, large surface area, and extraordinary thermal and mechanical properties. Although the potential of graphene as the most common 2D nanomaterials in biomedical applications has been extensively investigated, the practical use of other nanoengineered 2D materials beyond graphene such as transition metal dichalcogenides (TMDs), topological insulators (TIs), phosphorene, antimonene, bismuthene, metal-organic frameworks (MOFs) and MXenes for biomedical applications have not been appreciated so far. This review highlights not only the unique opportunities of 2D nanomaterials beyond graphene in various biomedical research areas such as bioelectronics, imaging, drug delivery, tissue engineering, and regenerative medicine but also addresses the risk factors and challenges ahead from the medical perspective and clinical translation of nanoengineered 2D materials. In conclusion, the perspectives and future roadmap of nanoengineered 2D materials beyond graphene are outlined for biomedical applications.

The Role of Zinc in Bone Mesenchymal Stem Cell Differentiation

Zinc is an essential trace element for bone growth and bone homeostasis in the human body. Bone mesenchymal stem cells (BMSCs) are multipotent progenitors existing in the bone marrow stroma with the capability of differentiating along multiple lineage pathways. Zinc plays a paramount role in BMSCs, which can be spurred differentiating into osteoblasts, chondrocytes, or adipocytes, and modulates the formation and activity of osteoclasts. The expression of related genes also changed during the differentiation of various cell phenotypes. Based on the important role of zinc in BMSC differentiation, using zinc as a therapeutic approach for bone remodeling will be a promising method. This review explores the role of zinc ion in the differentiation of BMSCs into various cell phenotypes and outlines the existing research on their molecular mechanism.

Nitrogen-Doped Multiwalled Carbon Nanotubes Enhance Bone Remodeling through Immunomodulatory Functions

It has been reported that multiwalled carbon nanotubes (MWCNTs) can reportedly positively affect growth and differentiation of bone-related cells and therefore offer great potential in biomedical applications. To overcome negative immune responses that limit their application, specific doping and functionalization can improve their biocompatibility. Here, we demonstrated that nitrogen-doped carboxylate-functionalized MWCNTs (N-MWCNTs) enhance bone remodeling both in vitro and in vivo with excellent biocompatibility, via stimulation of both bone resorption and formation. We revealed that 0.2 μg/mL N-MWCNTs not only increase the transcription of osteoblastogenic and osteoclastogenic genes but also up-regulate the activities of both TRAP and AKP in the differentiation of bone marrow stromal cells (BMSCs). Additionally, intramuscular administration of N-MWCNTs at a dosage of 1.0 mg/kg body weight enhances bone mineral density and bone mass content in mice, as well as induces potentiated degree of TRAP- and ARS-positive staining in the femur. The positive regulation of N-MWCNTs on bone remodeling is initiated by macrophage phagocytosis, which induces altered production of inflammatory cytokines by immune response pathways, and consequently up-regulates IL1α, IL10, and IL16. These cytokines collectively regulate the central osteoclastogenic transcription factor NFATc1 and osteoblastogenic BMP signaling, the suppression of which confirmed that these factors respectively participate in N-MWCNT-mediated regulation of osteoclastic and osteoblastic bone marrow stem cell activities. These results suggest that N-MWCNTs can be readily generalized for use as biomaterials in bone tissue engineering for metabolic bone disorders.

Scaffold-based developmental tissue engineering strategies for ectodermal organ regeneration

Tissue engineering (TE) is a multidisciplinary research field aiming at the regeneration, restoration, or replacement of damaged tissues and organs. Classical TE approaches combine scaffolds, cells and soluble factors to fabricate constructs mimicking the native tissue to be regenerated. However, to date, limited success in clinical translations has been achieved by classical TE approaches, because of the lack of satisfactory biomorphological and biofunctional features of the obtained constructs. Developmental TE has emerged as a novel TE paradigm to obtain tissues and organs with correct biomorphology and biofunctionality by mimicking the morphogenetic processes leading to the tissue/organ generation in the embryo. Ectodermal appendages, for instance, develop in vivo by sequential interactions between epithelium and mesenchyme, in a process known as secondary induction. A fine artificial replication of these complex interactions can potentially lead to the fabrication of the tissues/organs to be regenerated. Successful developmental TE applications have been reported, in vitro and in vivo, for ectodermal appendages such as teeth, hair follicles and glands. Developmental TE strategies require an accurate selection of cell sources, scaffolds and cell culture configurations to allow for the correct replication of the in vivo morphogenetic cues. Herein, we describe and discuss the emergence of this TE paradigm by reviewing the achievements obtained so far in developmental TE 3D scaffolds for teeth, hair follicles, and salivary and lacrimal glands, with particular focus on the selection of biomaterials and cell culture configurations.

Improved nanomechanical and in-vitro biocompatibility of graphene oxide-carbon nanotube hydroxyapatite hybrid composites by synergistic effect

Hydroxyapatite (HAP) is an attractive bio-material for new bone growth process, hard tissue repair, bioactivity, osteoblast adhesion and proliferation due to its physicochemical resembles natural apatite. The intrinsic brittleness and poor mechanical properties of HAP restrict it for potential clinical applications. This problem is undertaken by exploiting the unique properties of carbon nanofillers (carbon nanotube (CNTs), graphene oxide (GO), graphene oxide-carbon nanotube (GCNTs) hybrid) which are used as reinforcement for preparing the carbon nanofillers based HAP composites. The nanomechanical and in-vitro biocompatibility of carbon nanofiller reinforced HAP composites have been studied. Carbon nanofiller reinforced HAP composites led to an improvement in nanomechanical and biocompatibility properties. The nanoindentation hardness and elastic modulus of GCNTs-HAP composites are significantly higher than other carbon nanofiller reinforced composites and pristine HAP powder. The in-vitro cytotoxicity of the prepared carbon nanofillers reinforced HAP composites is examined using MTT-assay on the MDCK cell line. The prepared GCNTs-HAP composites containing 2% of GCNTs nanofiller show higher cell viability, improved compatibility, and superior one cell proliferation induction than the other carbon nanofillers and HAP. These findings will provide the new prospects for utilizing the GO and its hybrid in HAP composites in bone repair, regeneration, augmentation and implantation.

Recent advancement in biomedical applications on the surface of two-dimensional materials: from biosensing to tissue engineering

As biosensors and biomedical devices have become increasingly important to everyday diagnostics and monitoring, there are tremendous, and constant efforts towards developing and improving the reliability and versatility of such technology. As they offer high surface area-to-volume ratios and a diverse range of properties, from electronic to optical, two dimensional (2D) materials have proven to be very promising candidates for biological applications and technologies. Due to the dimensionality, 2D materials facilitate many interfacial phenomena that have shown to significantly improve the performance of biosensors, while recent advances in synthesis techniques and surface engineering methods also enable the realization of future biomedical devices. This short review aims to highlight the influence of 2D material surfaces and the properties that arise due to their 2D structure. Using recent (within the last few years) examples of biosensors and biomedical applications, we emphasize the important role of 2D materials in advancing developments and research for biosensing and healthcare.