Graphene: A Multifaceted Carbon-Based Material for Bone Tissue Engineering Applications

Advances of Hydroxyapatite Nanoparticles in Dental Implant Applications

Hydroxyapatite nanoparticles (HANPs) are becoming increasingly crucial in dental implant applications as they are highly compatible with biological systems, actively support biological processes, and closely resemble bone minerals. This review covers the latest progress in how HANPs are made, studied, and used in dentistry. It looks at critical methods for creating HANPs, such as sol-gel, microwave hydrothermal synthesis, and biomimetic approaches, and how they affect the particles' size, structure, and activity. The green synthesis method illustrated a new door to synthesize HAp for maintaining biocompatibilityand increasing antibacterial properties. The review also explores how HANPs improve the integration of implants with bone, support bone growth, and help treat sensitive teeth based on various laboratory and clinical studies. The usage of HAp in dentin and enamel shows higher potentiality through FTIR, XPS, XRD, EDS, etc., for mechanical stability and biological balance compared to natural teeth. Additionally, the use of HANPs in dental products like toothpaste and mouthwash is discussed, highlighting its potential to help rebuild tooth enamel and fight bacteria. There are some challenges for long-term usage against oral bacteria, but doping with inorganic materials, like Zn, has already solved this periodontal problem. Much more research is still essential to estimate the fabrication variation based on patient problems and characteristics. Still, it has favorable outcomes regarding its bioactive nature and antimicrobial properties. Due to their compatibility with biological tissues and ability to support bone growth, HANPs hold great promise for advancing dental materials and implant technology, potentially leading to better dental care and patient outcomes.

The Combination of Graphene and Polycaprolactone Scaffolds Enhancing Bone Mineralization and Hydroxyapatite

This study aimed to evaluate the effects of incorporating varying concentrations of graphene (0.5, 1.5, and 2.5 wt%) into polycaprolactone (PCL) scaffolds on mineralization and hydroxyapatite formation for bone tissue engineering applications.PCL scaffolds were fabricated with three different graphene concentrations: 0.5, 1.5, and 2.5 wt%. The scaffolds underwent characterization using Fourier-transform infrared spectroscopy (FTIR) to assess chemical composition and mineralization. Radiological imaging was employed to evaluate structural integrity and mineral density over a 21-day period. Additionally, histology analysis was performed to assess cellular interactions and scaffold integration.FTIR analysis on day 7 indicated early mineralization across all scaffolds, evidenced by phosphate (∼1030 cm-1) and hydroxyl (∼3500 cm-1) peaks, suggesting initial hydroxyapatite deposition. By day 21, the 2.5 wt% graphene scaffold demonstrated the highest degree of mineralization, with significantly increased hydroxyapatite formation compared with the other groups. However, this scaffold also exhibited signs of degradation, implying that higher graphene concentrations might compromise long-term scaffold stability. The 1.5 wt% graphene scaffold showed consistent mineralization and favorable osteoconductivity but did not reach the mineral deposition levels observed in the 2.5 wt% group.Incorporating graphene into PCL scaffolds enhances mineralization and hydroxyapatite formation, with the 2.5 wt% concentration achieving the most substantial effects. The 2.5 wt% graphene scaffold presents a balanced alternative, promoting steady mineralization and maintaining structural integrity, making it a promising candidate for bone tissue engineering applications.

Development of a Photocrosslinkable Collagen-Bone Matrix Hydrogel for Bone Tissue Engineering

Bone tissue engineering aims to restore lost bone and create an environment conducive to new bone formation. To address this challenge, we developed a novel biomimetic hydrogel that combines maleic anhydride-modified type I collagen (ColME) with maleic anhydride-modified demineralized and decellularized porcine bone matrix particles (mDBMp), forming a composite ColME-mDBMp (CMB) hydrogel. Chemical modification of collagen resulted in a high degree of substitution, thereby enhancing its photocrosslinkability. Integration of mDBMp into the ColME hydrogel via photocrosslinking resulted in enhanced physiological stability, reduced shrinkage, and improved mechanical strength compared to gelatin methacrylate (GelMA)-based hydrogels. Moreover, mineralization of the CMB hydrogel promoted the formation of pure hydroxyapatite (HAp) crystals, providing superior stiffness while maintaining ductility relative to GelMA-based hydrogels. In vitro, human bone marrow mesenchymal stem cells (hBMSCs) encapsulated in CMB hydrogels exhibited enhanced proliferation, cell-matrix interactions, and osteogenic differentiation, as evidenced by increased calcium deposition and histological analysis. These results demonstrate that the CMB hydrogel, enriched with extracellular matrix (ECM) components, shows considerable promise over current GelMA-based hydrogels for bone tissue engineering.

Phytol-mixed micelles alleviate dexamethasone-induced osteoporosis in zebrafish: Activation of the MMP3-OPN-MAPK pathway-mediating bone remodeling

This research investigates the therapeutic efficacy of phytol-mixed micelles in mitigating dexamethasone (Dex)-induced osteoporosis in zebrafish, with a particular focus on scale regeneration. Osteoporosis was induced in zebrafish through exposure to Dex, and the effects of phytol-mixed micelles were evaluated in this model. Following phytol therapy, bone mineralization was assessed using calcium, phosphorus, and alizarin red staining tests. Additionally, commercially available kits quantified the levels of tartrate-resistant acid phosphatase (TRAP), hydroxyproline (HP), and alkaline phosphatase (ALP). The mRNA expression levels of MMP3, osteopontin (OPN), and mitogen-activated protein kinase (MAPK) were examined using reverse transcription polymerase chain reaction (RT-PCR). The findings indicated that phytol significantly increased calcium and phosphorus concentrations. Phytol-mixed micelle therapy led to increased calcium deposition and enhanced bone formation, as evidenced by alizarin red staining. Moreover, phytol administration resulted in increased HP content and upregulated ALP and TRAP activities in zebrafish. RT-PCR tests demonstrated that phytol plays a role in the restoration of the MMP3-OPN-MAPK pathway. In summary, this research highlights the potential of phytol-mixed micelles in ameliorating Dex-induced osteoporosis in zebrafish. Clarifying phytol's mechanism, particularly its stimulation of the MMP3-OPN-MAPK pathway, provides insight into its role in facilitating bone remodeling.

Composite Graphene for the Dimension- and Pore-Size-Mediated Stem Cell Differentiation to Bone Regenerative Medicine

As one of the most promising means to repair diseased tissues, stem cell therapy with immense potential to differentiate into mature specialized cells has been rapidly developed. However, the clinical application of stem-cell-dominated regenerative medicine was heavily hindered by the loss of pluripotency during the long-term in vitro expansion. Here, a composite three-dimensional (3D) graphene-based biomaterial, denoted as GO-Por-CMP@CaP, with hierarchical pore structure (micro- to macropore), was developed to guide the directional differentiation of human umbilical cord MSCs (hucMSCs) into osteoblasts. GO-Por-CMP@CaP could act as a high-efficiency living composite material without a "dead space", effectively regulating the cellular response. The 3D topological structure generated via the two-step modification on two-dimensional graphene could effectively mimic the natural 3D microenvironment of cells, enhancing the stem cell attachment, which is not only conducive for the proliferation of stem cells but also beneficial for the osteogenic differentiation. Meanwhile, the wide existence of interconnected macropores was favorable for bone ingrowth, capillary formation, as well as the nutrients transportation. Furthermore, the concurrent existence of micro- and mesopores significantly promoted the extracellular matrix (ECM) adsorption, which ensured cellular attachment, leading to multiscale osteointegration. Both in vitro and in vivo assay demonstrated the above three factors collaborated mutually with nanosized calcium phosphate (CaP, with chemical similarities to the inorganic components of bone), which provided abundant adhesive sites to adequately induce osteogenic differentiation in the absence of any soluble growth factors. Proteomic analysis experiments confirmed that GO-Por-CMP@CaP promoted the differentiation of hucMSCs cells into osteoblasts by affecting the PI3K-Akt signaling pathway through the up-regulation of SPP1 protein. Our study offers a pure material-based stem cell differentiation regulating behavior via engineering the dimension and porosity of material, which provides insights into the design and development of substitutes to bone repair materials.

Graphene-Based Materials for Bone Regeneration in Dentistry: A Systematic Review of In Vitro Applications and Material Comparisons

INTRODUCTION

Graphene, a two-dimensional arrangement of carbon atoms, has drawn significant interest in medical research due to its unique properties. In the context of bone regeneration, graphene has shown several promising applications. Its robust structure, electrical conductivity, and biocompatibility make it an ideal candidate for enhancing bone tissue regeneration and repair processes. Studies have revealed that the presence of graphene can stimulate the proliferation and differentiation of bone cells, thereby promoting the formation of new bone tissue. Additionally, its ability to act as an effective carrier for growth factors and drugs allows controlled release, facilitating the engineering of specific tissues for bone regeneration.

AIM

To assess the efficacy of graphene in enhancing bone regeneration through in vitro studies, identify key safety concerns, and propose directions for future research to optimize its clinical applicability.

MATERIALS AND METHODS

The present systematic review was carried out using the PRISMA 2020 guideline. A first search was carried out on 20 November 2023 and was later updated on 14 February and 15 April 2024 in the databases of PubMed, Scopus, and Web of Science. Those in vitro studies published in English that evaluated the potential for bone regeneration with graphene in dentistry and also those which met the search terms were selected. Furthermore, the quality of the studies was assessed following the modified CONSORT checklist of in vitro studies on dental materials.

RESULTS

A total of 17 in vitro studies met the inclusion criteria. Among these, 12 showed increased osteoblast adhesion, proliferation, and differentiation, along with notable enhancements in mineralized matrix formation. Additionally, they exhibited a significant upregulation of osteogenic markers such as RUNX and COL1 (p < 0.05). However, the variability in methodologies and a lack of long-term assessments were noted as critical gaps.

CONCLUSIONS

The evaluation of the efficacy and safety of graphene in bone regeneration in dentistry revealed significant potential. However, it is recognized that clinical implementation should be approached with caution, considering identified areas of improvement and suggestions for future research. Future studies should focus on standardized experimental designs, including in vivo studies to evaluate long-term safety, immune responses, and vascularization processes in realistic biological environments.

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.

Recent Advances in Transparent Electrodes and Their Multimodal Sensing Applications

This review examines the recent advancements in transparent electrodes and their crucial role in multimodal sensing technologies. Transparent electrodes, notable for their optical transparency and electrical conductivity, are revolutionizing sensors by enabling the simultaneous detection of diverse physical, chemical, and biological signals. Materials like graphene, carbon nanotubes, and conductive polymers, which offer a balance between optical transparency, electrical conductivity, and mechanical flexibility, are at the forefront of this development. These electrodes are integral in various applications, from healthcare to solar cell technologies, enhancing sensor performance in complex environments. The paper addresses challenges in applying these electrodes, such as the need for mechanical flexibility, high optoelectronic performance, and biocompatibility. It explores new materials and innovative techniques to overcome these hurdles, aiming to broaden the capabilities of multimodal sensing devices. The review provides a comparative analysis of different transparent electrode materials, discussing their applications and the ongoing development of novel electrode systems for multimodal sensing. This exploration offers insights into future advancements in transparent electrodes, highlighting their transformative potential in bioelectronics and multimodal sensing technologies.

Biomaterials Mimicking Mechanobiology: A Specific Design for a Specific Biological Application

Mechanosensing and mechanotransduction pathways between the Extracellular Matrix (ECM) and cells form the essential crosstalk that regulates cell homeostasis, tissue development, morphology, maintenance, and function. Understanding these mechanisms involves creating an appropriate cell support that elicits signals to guide cellular functions. In this context, polymers can serve as ideal molecules for producing biomaterials designed to mimic the characteristics of the ECM, thereby triggering responsive mechanisms that closely resemble those induced by a natural physiological system. The generated specific stimuli depend on the different natural or synthetic origins of the polymers, the chemical composition, the assembly structure, and the physical and surface properties of biomaterials. This review discusses the most widely used polymers and their customization to develop biomaterials with tailored properties. It examines how the characteristics of biomaterials-based polymers can be harnessed to replicate the functions of biological cells, making them suitable for biomedical and biotechnological applications.

Current Perspectives of Protein in Bone Tissue Engineering: Bone Structure, Ideal Scaffolds, Fabrication Techniques, Applications, Scopes, and Future Advances

In view of their exceptional approach, excellent inherent biocompatibility and biodegradability properties, and interaction with the local extracellular matrix, protein-based polymers have received attention in bone tissue engineering, which is a multidisciplinary field that repairs and regenerates fractured bones. Bone is a multihierarchical complex structure, and it performs several essential biofunctions, including maintaining mineral balance and structural support and protecting soft organs. Protein-based polymers have gained interest in developing ideal scaffolds as emerging biomaterials for bone fractured healing and regeneration, and it is challenging to design ideal bone substitutes as perfect biomaterials. Several protein-based polymers, including collagen, keratin, gelatin, serum albumin, etc., are potential materials due to their inherent cytocompatibility, controlled biodegradability, high biofunctionalization, and tunable mechanical characteristics. While numerous studies have indicated the encouraging possibilities of proteins in BTE, there are still major challenges concerning their biodegradability, stability in physiological conditions, and continuous release of growth factors and bioactive molecules. Robust scaffolds derived from proteins can be used to replace broken or diseased bone with a biocompatible substitute; proteins, being biopolymers, provide excellent scaffolds for bone tissue engineering. Herein, recent developments in protein polymers for cutting-edge bone tissue engineering are addressed in this review within 3-5 years, with a focus on the significant challenges and future perspectives. The first section discusses the structural fundamentals of bone anatomy and ideal scaffolds, and the second section describes the fabrication techniques of scaffolds. The third section highlights the importance of proteins and their applications in BTE. Hence, the recent development of protein polymers for state-of-the-art bone tissue engineering has been discussed, highlighting the significant challenges and future perspectives.

Comparison of developmental toxicity of graphene oxide and graphdiyne to zebrafish larvae

Graphdiyne (GDY) is a new member of family of carbon-based 2D nanomaterials (NMs), but the environmental toxicity is less investigated compared with other 2D NMs, such as graphene oxide (GO). In this study, we compared with developmental toxicity of GO and GDY to zebrafish larvae. It was shown that exposure of zebrafish embryos from 5 h post fertilization to GO and GDY for up to 5 days decreased hatching rate and induced morphological deformity. Behavioral tests indicated that GO and GDY treatment led to hyperactivity of larvae. However, blood flow velocity was not significantly affected by GO or GDY. RNA-sequencing data revealed that both types of NMs altered gene expression profiles as well as gene ontology terms and KEGG pathways related with metabolism. We further confirmed that the NMs altered the expression of genes related with lipid droplets and autophagy, which may be account for the delayed development of zebrafish larvae. At the same mass concentrations, GO induced comparable or even larger toxic effects compared with GDY, indicating that GDY might be more biocompatible compared with GO. These results may provide novel understanding about the environmental toxicity of GO and GDY in vivo.