Size-dependent Effects of Gold Nanoparticles on Osteogenic Differentiation of Human Periodontal Ligament Progenitor Cells

Urinary dengue NS1 detection on Au-decorated ZnO nanowire platform

Biodetection for non-invasive diagnostics of fluids, especially urine, remains a challenge to scientists due to low target concentrations. And biological complexes of the detection target may contain contaminants that also interfere with any assay. Dengue non-structural 1 protein (Dengue NS1) is an important biomarker for dengue hemorrhagic fever and dengue shock syndrome. Here, we developed an Au-decorated nanowire platform and applied it with a sandwich fluorophore-linked immunosorbent well plate assay (FLISA) to detect Dengue NS1 in urine. For the platform, we fabricated zinc oxide (ZnO) nanowires to provide a high surface area and then coated them with gold nanoparticles (ZnO/Au nanowires) to simply modify the Dengue NS1 antibody and enhance the fluorescence intensity. Our platform employs a sandwich FLISA that exhibits high sensitivity, specifically detecting Dengue NS1 with a limit of detection (LOD) of 1.35 pg/mL. This LOD was 4500-fold lower than the LOD of a commercially available kit for Dengue NS1 enzyme-linked immunosorbent assay. We believe that our ZnO/Au nanowire platform has the potential to revolutionize the field of non-invasive diagnostics for dengue.

Autophagy, a double-edged sword for oral tissue regeneration

BACKGROUND

Oral health is of fundamental importance to maintain systemic health in humans. Stem cell-based oral tissue regeneration is a promising strategy to achieve the recovery of impaired oral tissue. As a highly conserved process of lysosomal degradation, autophagy induction regulates stem cell function physiologically and pathologically. Autophagy activation can serve as a cytoprotective mechanism in stressful environments, while insufficient or over-activation may also lead to cell function dysregulation and cell death.

AIM OF REVIEW

This review focuses on the effects of autophagy on stem cell function and oral tissue regeneration, with particular emphasis on diverse roles of autophagy in different oral tissues, including periodontal tissue, bone tissue, dentin pulp tissue, oral mucosa, salivary gland, maxillofacial muscle, temporomandibular joint, etc. Additionally, this review introduces the molecular mechanisms involved in autophagy during the regeneration of different parts of oral tissue, and how autophagy can be regulated by small molecule drugs, biomaterials, exosomes/RNAs or other specific treatments. Finally, this review discusses new perspectives for autophagy manipulation and oral tissue regeneration.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Overall, this review emphasizes the contribution of autophagy to oral tissue regeneration and highlights the possible approaches for regulating autophagy to promote the regeneration of human oral tissue.

Nanochemistry of gold: from surface engineering to dental healthcare applications

Advancements in nanochemistry have led to the development of engineered gold nanostructures (GNSs) with remarkable potential for a variety of dental healthcare applications. These innovative nanomaterials offer unique properties and functionalities that can significantly improve dental diagnostics, treatment, and overall oral healthcare applications. This review provides an overview of the latest advancements in the design, synthesis, and application of GNSs for dental healthcare applications. Engineered GNSs have emerged as versatile tools, demonstrating immense potential across different aspects of dentistry, including enhanced imaging and diagnosis, prevention, bioactive coatings, and targeted treatment of oral diseases. Key highlights encompass the precise control over GNSs' size, crystal structure, shape, and surface functionalization, enabling their integration into sensing, imaging diagnostics, drug delivery systems, and regenerative therapies. GNSs, with their exceptional biocompatibility and antimicrobial properties, have demonstrated efficacy in combating dental caries, periodontitis, peri-implantitis, and oral mucosal diseases. Additionally, they show great promise in the development of advanced sensing techniques for early diagnosis, such as nanobiosensor technology, while their role in targeted drug delivery, photothermal therapy, and immunomodulatory approaches has opened new avenues for oral cancer therapy. Challenges including long-term toxicity, biosafety, immune recognition, and personalized treatment are under rigorous investigation. As research at the intersection of nanotechnology and dentistry continues to thrive, this review highlights the transformative potential of engineered GNSs in revolutionizing dental healthcare, offering accurate, personalized, and minimally invasive solutions to address the oral health challenges of the modern era.

The impact of nanomaterials on autophagy across health and disease conditions

Autophagy, a catabolic process integral to cellular homeostasis, is constitutively active under physiological and stress conditions. The role of autophagy as a cellular defense response becomes particularly evident upon exposure to nanomaterials (NMs), especially environmental nanoparticles (NPs) and nanoplastics (nPs). This has positioned autophagy modulation at the forefront of nanotechnology-based therapeutic interventions. While NMs can exploit autophagy to enhance therapeutic outcomes, they can also trigger it as a pro-survival response against NP-induced toxicity. Conversely, a heightened autophagy response may also lead to regulated cell death (RCD), in particular autophagic cell death, upon NP exposure. Thus, the relationship between NMs and autophagy exhibits a dual nature with therapeutic and environmental interventions. Recognizing and decoding these intricate patterns are essential for pioneering next-generation autophagy-regulating NMs. This review delves into the present-day therapeutic potential of autophagy-modulating NMs, shedding light on their status in clinical trials, intervention of autophagy in the therapeutic applications of NMs, discusses the potency of autophagy for application as early indicator of NM toxicity.

Near-infrared light responsive gold nanoparticles coating endows polyetheretherketone with enhanced osseointegration and antibacterial properties

Polyetheretherketone (PEEK) is considered as a promising dental implant material owing to its excellent physicochemical and mechanical properties. However, its wide range of applications is limited by its biologically inert nature. In this study, a near-infrared (NIR) light responsive bioactive coating with gold nanoparticles (AuNPs) and metronidazole adhered to the PEEK surface via dopamine polymerization. Compared to pure PEEK, the hydrophilicity of the treated PEEK surface was significantly improved. In addition, under NIR light, the surface coating exhibited photothermal conversion effect, and gold nanoparticles and the antibiotic can be released from the coating. This improved the antibacterial properties of PEEK materials. Moreover, the coating was more conducive to the early adhesion of bone mesenchymal stem cells. The results of in vitro and in vivo osteogenic activity studies showed that the developed coating promoted osseointegration of PEEK implants, and NIR light irradiation further improved the antibacterial ability and osteogenic activity of PEEK implants. Through RNA sequencing, the potential underlying mechanism of promoting bone formation of the AuNPs coating combined metronidazole was interpreted. In summary, the developed coating is a potential surface treatment strategy that endows PEEK with enhanced osseointegration and antibacterial properties.

Modulation of calcium-influx by carboxymethyl tamarind‑gold nanoparticles promotes biomineralization for tissue regeneration

Gold nanoparticles (AuNPs) have been reported to modulate bone tissue regeneration and are being extensively utilized in biomedical implementations attributable to their low cytotoxicity, biocompatibility and simplicity of functionalization. Lately, biologically synthesized nanoparticles have acquired popularity because of their environmentally acceptable alternatives for diverse applications. Here we report the green synthesis of AuNPs by taking the biopolymer Carboxymethyl Tamarind (CMT) as a unique reducing as well as a stabilizing agent. The synthesized CMT-AuNPs were analyzed by UV-vis spectrophotometer, DLS, FTIR, XRD, TGA, SEM and TEM. These results suggest that CMT-AuNPs possess an average size of 19.93 ± 8.52 nm and have long-term stability. Further, these CMT-AuNPs promote the proliferation together with the differentiation and mineralization of osteoblast cells in a "dose-dependent" manner. Additionally, CMT-AuNPs are non-toxic to SD rats when applied externally. We suggest that the CMT-AuNPs have the potential to be a suitable and non-toxic agent for differentiation and mineralization of osteoblast cells in vitro and this can be tested in vivo as well.

Multifunctional Metal-Phenolic Composites Promote Efficient Periodontitis Treatment via Antibacterial and Osteogenic Properties

Periodontitis, a complex inflammatory disease initiated by bacterial infections, presents a significant challenge in public health. The increased levels of reactive oxygen species and the subsequent exaggerated immune response associated with periodontitis often lead to alveolar bone resorption and tooth loss. Herein, we develop multifunctional metal-phenolic composites (i.e., Au@MPN-BMP2) to address the complex nature of periodontitis, where gold nanoparticles (AuNPs) are coated by metal-phenolic networks (MPNs) and bone morphogenetic protein 2 (BMP2). In this design, MPNs exhibit remarkable antibacterial and antioxidant properties, and AuNPs and BMP2 promote osteogenic differentiation of bone marrow mesenchymal stem cells under inflammatory conditions. In a rat model of periodontitis, treatment with Au@MPN-BMP2 leads to notable therapeutic outcomes, including mitigated oxidative stress, reduced progression of inflammation, and the significant prevention of inflammatory bone loss. These results highlight the multifunctionality of Au@MPN-BMP2 nanoparticles as a promising therapeutic approach for periodontitis, addressing both microbial causative factors and an overactivated immune response. We envision that the rational design of metal-phenolic composites will provide versatile nanoplatforms for tissue regeneration and potential clinical applications.

Effects of Nanomaterials on Synthesis and Degradation of the Extracellular Matrix

Extracellular matrix (ECM) remodeling is accompanied by the continuous synthesis and degradation of the ECM components. This dynamic process plays an important role in guiding cell adhesion, migration, proliferation, and differentiation, as well as in tissue development, body repair, and maintenance of homeostasis. Nanomaterials, due to their photoelectric and catalytic properties and special structure, have garnered much attention in biomedical fields for use in processes such as tissue engineering and disease treatment. Nanomaterials can reshape the cell microenvironment by changing the synthesis and degradation of ECM-related proteins, thereby indirectly changing the behavior of the surrounding cells. This review focuses on the regulatory role of nanomaterials in the process of cell synthesis of different ECM-related proteins and extracellular protease. We discuss influencing factors and possible related mechanisms of nanomaterials in ECM remodeling, which may provide different insights into the design and development of nanomaterials for the treatment of ECM disorder-related diseases.

Enzymatically Bioactive Nucleus Pulposus Matrix Hydrogel Microspheres for Exogenous Stem Cells Therapy and Endogenous Repair Strategy to Achieve Disc Regeneration

Exogenous stem cell therapy and endogenous repair has shown great potential in intervertebral disc regeneration. However, limited nutrients and accumulation of lactate largely impair the survival and regenerative capacity of implanted stem cells and endogenous nucleus pulposus cells (NPCs). Herein, an injectable hydrogel microsphere (LMGDNPs) have been developed by immersing lactate oxidase (LOX)-manganese dioxide (MnO2 ) nanozyme (LM) into glucose-enriched decellularized nucleus pulposus hydrogel microspheres (GDNPs) through a microfluidic system. LMGDNPs showed a delayed release profile of LOX and satisfactory enzymatic capacity in consuming lactate. Mesenchymal stem cells (MSCs) plated on LMGDNPs exhibited better cell viability than cells on GelMA and decellularized nucleus pulposus microspheres (DNP) and showed a obviously increased NPCs phenotype. LMGDNPs prevented MSCs and NPCs death and promoted extracellular matrix synthesis by exhausting lactate. It is determined that LMGDNPs promoted NPCs autophagy by activating transforming growth factor β2 overlapping transcript 1 (TGFB2-OT1), relying on the nanozyme. MSCs-loaded LMGDNPs largely preserved disc hydration and alleviated matrix degradation in vivo. Summarily, LMGDNPs promoted cell survival and matrix regeneration by providing a nutrient supply, exhausting lactate, and activating autophagy via TGFB2-OT1 and its downstream pathway and may serve as an ideal delivery system for exogenous stem cell therapy and endogenous repair.

Nel-like Molecule Type 1 Combined with Gold Nanoparticles Modulates Macrophage Polarization, Osteoclastogenesis, and Oral Microbiota in Periodontitis

The disruption of host-microbe homeostasis and uncontrolled inflammatory response have been considered as vital causes for developing periodontitis, subsequently leading to an imbalance between the bone and immune system and the collapse of bone homeostasis. Consequently, strategies to modulate the immune response and bone metabolization have become a promising approach to prevent and treat periodontitis. In this study, we investigated the cooperative effects of Nel-like molecule type 1 (Nell-1) and gold nanoparticles (AuNPs) on macrophage polarization, osteoclast differentiation, and the corresponding functions in an experimental model of periodontitis in rats. Nell-1-combined AuNPs in in vitro studies were found to reduce the production of inflammatory factors (TNF-α, p < 0.0001; IL-6, p = 0.0012), modulate the ratio of M2/M1 macrophages by inducing macrophage polarization into the M2 phenotype, and inhibit cell fusion, maturation, and activity of osteoclasts. Furthermore, the local application of Nell-1-combined AuNPs in in vivo studies resulted in alleviation of damages to the periodontal and bone tissues, modulation of macrophage polarization and the activity of osteoclasts, and alteration of the periodontal microbiota, in which the relative abundance of the probiotic Bifidobacterium increased (p < 0.05). These findings reveal that Nell-1-combined AuNPs could be a promising drug candidate for the prevention and treatment of periodontitis. However, Nell-1-combined AuNPs did not show organ toxicity or impair the integrity of intestinal epithelium but alter the gut microbiota, leading to the dysbiosis of gut microbiota. The adverse impact of changes in gut microbiota needs to be further investigated. Nonetheless, this study provides a novel perspective and direction for the biological safety assessment of biomaterials in oral clinical applications.

AFF4 regulates osteogenic potential of human periodontal ligament stem cells via mTOR-ULK1-autophagy axis

Scaffold protein AF4/FMR2 family member 4 (AFF4) has been found to play a role in osteogenic commitment of stem cells. However, function of AFF4 in human periodontal ligament stem cells (hPDLSCs) has not been studied yet. This present study aims to investigate the biological effect of AFF4 on osteogenic differentiation of hPDLSCs and potential mechanistic pathway. First, AFF4 expression profile was evaluated in conditions of periodontitis and osteogenic differentiation of hPDLSCs by immunohistochemical staining, western blot and qRT-PCR. Next, si-RNA mediated knockdown and lentiviral transduction mediated overexpression of AFF4 were adopted to explore impact of AFF4 on osteogenic capacity of hPDLSCs. Then, possible mechanistic pathway was identified. At last, pharmacological agonist of autophagy, rapamycin, was utilized to affirm the role of autophagy in AFF4-regulated osteogenesis of hPDLSCs. First, AFF4 expressions were significantly lower in inflamed periodontal tissues and lipopolysaccharides-treated hPDLSCs than controls, and were up-regulated during osteogenic differentiation of hPDLSCs. Next, osteogenic potential of hPDLSCs was impaired by AFF4 knockdown and potentiated by AFF4 overexpression. Moreover, AFF4 was found to positively regulate autophagic activity in hPDLSCs. At last, rapamycin treatment was shown to be able to partly restore AFF4 knockdown-suppressed osteogenic differentiation. Our study demonstrates that AFF4 regulates osteogenic potential of hPDLSCs via targeting autophagic activity. The involvement of AFF4 in periodontal homeostasis was identified for the first time.

A multifunctional quercetin/polycaprolactone electrospun fibrous membrane for periodontal bone regeneration

Image 1.

Multifunctional gold nanoparticles for osteoporosis: synthesis, mechanism and therapeutic applications

Osteoporosis is currently the most prevalent bone disorder worldwide and is characterized by low bone mineral density and an overall increased risk of fractures. To treat osteoporosis, a range of drugs targeting bone homeostasis have emerged in clinical practice, including anti-osteoclast agents such as bisphosphonates and denosumab, bone formation stimulating agents such as teriparatide, and selective oestrogen receptor modulators. However, traditional clinical medicine still faces challenges related to side effects and high costs of these types of treatments. Nanomaterials (particularly gold nanoparticles [AuNPs]), which have unique optical properties and excellent biocompatibility, have gained attention in the field of osteoporosis research. AuNPs have been found to promote osteoblast differentiation, inhibit osteoclast formation, and block the differentiation of adipose-derived stem cells, which thus is believed to be a novel and promising candidate for osteoporosis treatment. This review summarizes the advances and drawbacks of AuNPs in their synthesis and the mechanisms in bone formation and resorption in vitro and in vivo, with a focus on their size, shape, and chemical composition as relevant parameters for the treatment of osteoporosis. Additionally, several important and promising directions for future studies are also discussed, which is of great significance for prevention and treatment of osteoporosis.

Recent Advances in Functionalized Electrospun Membranes for Periodontal Regeneration

Periodontitis is a global, multifaceted, chronic inflammatory disease caused by bacterial microorganisms and an exaggerated host immune response that not only leads to the destruction of the periodontal apparatus but may also aggravate or promote the development of other systemic diseases. The periodontium is composed of four different tissues (alveolar bone, cementum, gingiva, and periodontal ligament) and various non-surgical and surgical therapies have been used to restore its normal function. However, due to the etiology of the disease and the heterogeneous nature of the periodontium components, complete regeneration is still a challenge. In this context, guided tissue/bone regeneration strategies in the field of tissue engineering and regenerative medicine have gained more and more interest, having as a goal the complete restoration of the periodontium and its functions. In particular, the use of electrospun nanofibrous scaffolds has emerged as an effective strategy to achieve this goal due to their ability to mimic the extracellular matrix and simultaneously exert antimicrobial, anti-inflammatory and regenerative activities. This review provides an overview of periodontal regeneration using electrospun membranes, highlighting the use of these nanofibrous scaffolds as delivery systems for bioactive molecules and drugs and their functionalization to promote periodontal regeneration.

AuNP-Loaded Electrospinning Membrane Cooperated with CDs for Periodontal Tissue Engineering

BACKGROUND

Guided bone regeneration (GBR) is commonly used to regenerate periodontal tissue. However, the bone inductivity and antibacterial properties of the GBR membranes currently in use are severely limited. This issue can be resolved by loading growth factors and antibiotics. Bioactive substitutes, such as Au nanoparticles (AuNPs) and carbon quantum dots (CDs), were proposed to prevent the denaturation of osteogenic growth factors and the induction of antibacterial drug resistance.

METHODS

Ornidazole was initially used as the raw material to prepare the CDs, followed by the incorporation of an optimal ratio of nanoparticles to produce the electrospun membrane doped with AuNPs and novel traceable antibacterial CDs. The morphology of the membrane was characterized. The adhesion, proliferation, and osteogenic differentiation of cells on the membrane were evaluated in vitro. The antimicrobial characteristics of the membrane were also investigated. The electrospun membrane was implanted into a rat skull defect model in vivo to investigate its osteogenic potential.

RESULTS

The blending of nanomaterials did not affect the micro morphology of the fiber, resulting in enhanced mechanical properties. Membranes doped with AuNPs and CDs exhibited excellent biocompatibility, increased ALP activity, improved calcified nodules, and increased expression of osteogenic-associated proteins, in addition to pronounced antibacterial effects. The membrane also demonstrated excellent osteogenic characteristics in rat models.

CONCLUSION

The synergistic effect of loaded AuNPs electrospun fiber membrane with CDs can promote periodontal bone regeneration and exert antibacterial activity.

Tracking cellular uptake, intracellular trafficking and fate of nanoclay particles in human bone marrow stromal cells

Clay nanoparticles, in particular synthetic smectites, have generated interest in the field of tissue engineering and regenerative medicine due to their utility as cross-linkers for polymers in biomaterial design and as protein release modifiers for growth factor delivery. In addition, recent studies have suggested a direct influence on the osteogenic differentiation of responsive stem and progenitor cell populations. Relatively little is known however about the mechanisms underlying nanoclay bioactivity and in particular the cellular processes involved in nanoclay-stem cell interactions. In this study we employed confocal microscopy, inductively coupled plasma mass spectrometry and transmission electron microscopy to track the interactions between clay nanoparticles and human bone marrow stromal cells (hBMSCs). In particular we studied nanoparticle cellular uptake mechanisms and uptake kinetics, intracellular trafficking pathways and the fate of endocytosed nanoclay. We found that nanoclay particles present on the cell surface as μm-sized aggregates, enter hBMSCs through clathrin-mediated endocytosis, and their uptake kinetics follow a linear increase with time during the first week of nanoclay addition. The endocytosed particles were observed within the endosomal/lysosomal compartments and we found evidence for both intracellular degradation of nanoclay and exocytosis as well as an increase in autophagosomal activity. Inhibitor studies indicated that endocytosis was required for nanoclay upregulation of alkaline phosphatase activity but a similar dependency was not observed for autophagy. This study into the nature of nanoclay-stem cell interactions, in particular the intracellular processing of nanosilicate, may provide insights into the mechanisms underlying nanoclay bioactivity and inform the successful utilisation of clay nanoparticles in biomaterial design.

Endowing improved osteogenic activities with collagen membrane by incorporating biocompatible iron oxide nanoparticles

Introduction: Collagen-based scaffolds, renowned for their exceptional biocompatibility, have garnered attention as promising scaffolds for advancing bone tissue regeneration. Nevertheless, these scaffolds possess inherent limitations, such as notably compromised osteo-conductivity and osteo-inductivity. Methods: Our study focused on enhancing the mechanical properties and osteogenic bioactivities of bovine-derived collagen membranes (CMs) from the Achilles tendon by incorporating FDA-approved iron oxide nanoparticles (IONPs), termed as IONP-CM. Three types of IONP-CMs (IONP-CM-0.5, IONP-CM-1, and IONPCM-1.5) were constructed by altering the amounts of feeding IONPs. Results: Surface topography analysis demonstrated comparable characteristics between the IONP-CM and neat CM, with the former exhibiting augmented mechanical properties. In vitro evaluations revealed the remarkable biocompatibility of IONP-CMs toward mouse calvarial pre-osteoblast MC3T3-E1 cells, concurrently stimulating osteogenic differentiation. Mechanistic investigations unveiled that the osteogenic differentiation induced by IONP-CMs stemmed from the activation of the Wnt/β-catenin signaling pathway. Furthermore, in vivo bone regeneration assessment was performed by implanting IONP-CMs into the radial defect in rabbits. Results derived from micro-computed tomography and histological analyses unequivocally substantiated the capacity of IONP-CMs to expedite bone repair processes. Discussion: IONP-CMs emerged as scaffolds boasting exceptional biocompatibility and enhanced osteogenic properties, positioning them as promising candidates for facilitating bone tissue regeneration.

Promising renoprotective effect of gold nanoparticles and dapagliflozin in diabetic nephropathy via targeting miR-192 and miR-21

Diabetic nephropathy (DN) is a worldwide issue that eventually leads to end-stage renal failure, with limited therapeutic options. Prior research has revealed that gold nanoparticles (AuNPs) have a substantial antidiabetic impact. In addition, sodium-glucose cotransporter2 (SGLT2) inhibitors, including dapagliflozin (DAPA), had renoprotective impact on DN. Therefore, this research attempted to determine the potential AuNPs and DAPA impacts in ameliorating experimentally DN induction and the underlying mechanisms focusing on miR-192 and miR-21, correlating them with autophagy, apoptosis, fibrosis, and oxidative stress. Diabetes induction was through a single intraperitoneal streptozotocin (55 mg/kg) injection, and rats with diabetes received AuNPs (2.5 mg/kg/day) as well as DAPA (2 mg/kg/day) for 7 weeks as a treatment. AuNPs and DAPA treatment for 7 weeks substantially alleviated DN. AuNPs and DAPA significantly increased catalase (CAT) activity as well as serum total antioxidant capacity (TAC), along with a substantial decline in malondialdehyde (MDA). AuNPs and DAPA treatment alleviated renal fibrosis as they decreased transforming growth factorß1(TGF-ß1) as well as matrix metalloproteinase-2 (MMP-2) renal expression, decreased apoptosis through alleviating the proapoptotic gene (caspase-3) renal expression and increased the antiapoptotic gene (Bcl-2) renal expression, and increased autophagy as they increased LC-3 as well as Beclin-1 renal expression. Autophagy activation, inhibition of apoptosis, and renal fibrosis could be due to their inhibitory impact on miR-192 and miR-21 renal expression. AuNPs and DAPA have a protective effect on DN in rats by targeting miR-192 and miR-21 and their downstream pathways, including fibrosis, apoptosis, autophagy, and oxidative stress.

Biological Performance of Primary Dental Pulp Stem Cells Treated with Gold Nanoparticles

Gold nanoparticles (AuNPs) are one of the most stable nanoparticles that have been prevalently used as examples for biological and biomedical applications. Herein, we evaluate the effect of AuNPs on the biological processes of dental pulp stem cells derived from exfoliated deciduous teeth (SHED). Two different shapes of PEGylated AuNPs, rods (AuNR-PEG) and spheres (AuNS-PEG), were prepared and characterized. SHED cells were treated with different concentrations of AuNR-PEG and AuNS-PEG to determine their effect on the stemness profile of stem cells (SCs), proliferation, cytotoxicity, cellular uptake, and reactive oxygen species (ROS), for cells cultured in media containing-fetal bovine serum (FBS) and serum-free media (SFM). Our results showed that both nanoparticle shapes maintained the expression profile of MSC surface markers. Moreover, AuNS-PEG showed a stimulatory effect on the proliferation rate and lower toxicity on SHED, compared to AuNR-PEG. Higher concentrations of 0.5-0.125 nM of AuNR-PEG have been demonstrated to cause more toxicity in cells. Additionally, cells treated with AuNPs and cultured in FBS showed a higher proliferative rate and lower toxicity when compared to the SFM. For cellular uptake, both AuNS-PEG and AuNR-PEG were uptaken by treated cells efficiently. However, cells cultured in SFM media showed a higher percentage of cellular uptake. For ROS, AuNR-PEG showed a significant reduction in ROS at lower concentrations (<0.03 nM), while AuNS-PEG did not show any significant difference compared to the control untreated cells. Thus, our results give evidence about the optimum concentration and shape of AuNPs that can be used for the differentiation of stem cells into specific cell lineages in tissue engineering and regenerative medicine.

Autophagy and Biomaterials: A Brief Overview of the Impact of Autophagy in Biomaterial Applications

Macroautophagy (hereafter autophagy), a tightly regulated physiological process that obliterates dysfunctional and damaged organelles and proteins, has a crucial role when biomaterials are applied for various purposes, including diagnosis, treatment, tissue engineering, and targeted drug delivery. The unparalleled physiochemical properties of nanomaterials make them a key component of medical strategies in different areas, such as osteogenesis, angiogenesis, neurodegenerative disease treatment, and cancer therapy. The application of implants and their modulatory effects on autophagy have been known in recent years. However, more studies are necessary to clarify the interactions and all the involved mechanisms. The advantages and disadvantages of nanomaterial-mediated autophagy need serious attention in both the biological and bioengineering fields. In this mini-review, the role of autophagy after biomaterial exploitation and the possible related mechanisms are explored.

Autophagy inhibitors for cancer therapy: Small molecules and nanomedicines

Autophagy is a conserved process in which the cytosolic materials are degraded and eventually recycled for cellular metabolism to maintain homeostasis. The dichotomous role of autophagy in pathogenesis is complicated. Accumulating reports have suggested that cytoprotective autophagy is responsible for tumor growth and progression. Autophagy inhibitors, such as chloroquine (CQ) and hydroxychloroquine (HCQ), are promising for treating malignancies or overcoming drug resistance in chemotherapy. With the rapid development of nanotechnology, nanomaterials also show autophagy-inhibitory effects or are reported as the carriers delivering autophagy inhibitors. In this review, we summarize the small-molecule compounds and nanomaterials inhibiting autophagic flux as well as the mechanisms involved. The nanocarrier-based drug delivery systems for autophagy inhibitors and their distinct advantages are also described. The progress of autophagy inhibitors for clinical applications is finally introduced, and their future perspectives are discussed.

Potential application of inorganic nano-materials in modulation of macrophage function: Possible application in bone tissue engineering

Nanomaterials indicate unique physicochemical properties for drug delivery in osteogenesis. Benefiting from high surface area grades, high volume ratio, ease of functionalization by biological targeting moieties, and small size empower nanomaterials to pass through biological barriers for efficient targeting. Inorganic nanomaterials for bone regeneration include inorganic synthetic polymers, ceramic nanoparticles, metallic nanoparticles, and magnetic nanoparticles. These nanoparticles can effectively modulate macrophage polarization and function, as one of the leading players in osteogenesis. Bone healing procedures in close cooperation with the immune system. Inflammation is one of the leading triggers of the bone fracture healing barrier. Macrophages commence anti-inflammatory signaling along with revascularization in the damaged site to promote the formation of a soft callus, bone mineralization, and bone remodeling. In this review, we will discuss the role of macrophages in bone hemostasis and regeneration. Furthermore, we will summarize the influence of the various inorganic nanoparticles on macrophage polarization and function in the benefit of osteogenesis.

Nanomaterials for Periodontal Tissue Regeneration: Progress, Challenges and Future Perspectives

Bioactive nanomaterials are increasingly being applied in oral health research. Specifically, they have shown great potential for periodontal tissue regeneration and have substantially improved oral health in translational and clinical applications. However, their limitations and side effects still need to be explored and elucidated. This article aims to review the recent advancements in nanomaterials applied for periodontal tissue regeneration and to discuss future research directions in this field, especially focusing on research using nanomaterials to improve oral health. The biomimetic and physiochemical properties of nanomaterials such as metals and polymer composites are described in detail, including their effects on the regeneration of alveolar bone, periodontal ligament, cementum and gingiva. Finally, the biomedical safety issues of their application as regenerative materials are updated, with a discussion about their complications and future perspectives. Although the applications of bioactive nanomaterials in the oral cavity are still at an initial stage, and pose numerous challenges, recent research suggests that they are a promising alternative in periodontal tissue regeneration.

Gold nanoparticles: promising biomaterials for osteogenic/adipogenic regulation in bone repair

Bone defects are a common bone disease, which are usually caused by accidents, trauma and tumors. However, the treatment of bone defects is still a great clinical challenge. In recent years, research on bone repair materials has continued with great success, but there are few reports on the repair of bone defects at a high lipid level. Hyperlipidemia is a risk factor in the process of bone defect repair, which has a negative impact on the process of osteogenesis, increasing the difficulty of bone defect repair. Therefore, it is necessary to find materials that can promote bone defect repair under the condition of hyperlipidemia. Gold nanoparticles (AuNPs) have been applied in the fields of biology and clinical medicine for many years and developed to modulate osteogenic differentiation and adipogenic differentiation. In vitro and vivo studies displayed that they promoted bone formation and inhibited fat accumulation. Further, the metabolism and mechanisms of AuNPs acting on osteogenesis/adipogenesis were partially revealed by researchers. This review further clarifies the role of AuNPs in osteogenic/adipogenic regulation during the process of osteogenesis and bone regeneration by summarizing the related in vitro and in vivo research, discussing the advantages and challenges of AuNPs and highlighting several possible directions for future research, with the aim to provide a new strategy for dealing with bone defects in hyperlipidemic patients.

The role of autophagy in bone metabolism and clinical significance

The skeletal system is the basis of the vertebral body composition, which affords stabilization sites for muscle attachment, protects vital organs, stores mineral ions, supplies places to the hematopoietic system, and participates in complex endocrine and immune system. Not surprisingly, bones are constantly reabsorbed, formed, and remodeled under physiological conditions. Once bone metabolic homeostasis is interrupted (including inflammation, tumors, fractures, and bone metabolic diseases), the body rapidly initiates bone regeneration to maintain bone tissue structure and quality. Macroautophagy/autophagy is an essential metabolic process in eukaryotic cells, which maintains metabolic energy homeostasis and plays a vital role in bone regeneration by controlling molecular degradation and organelle renewal. One relatively new observation is that mesenchymal cells, osteoblasts, osteoclasts, osteocytes, chondrocytes, and vascularization process exhibit autophagy, and the molecular mechanisms and targets involved are being explored and updated. The role of autophagy is also emerging in degenerative diseases (intervertebral disc degeneration [IVDD], osteoarthritis [OA], etc.) and bone metabolic diseases (osteoporosis [OP], osteitis deformans, osteosclerosis). The use of autophagy regulators to modulate autophagy has benefited bone regeneration, including MTOR (mechanistic target of rapamycin kinase) inhibitors, AMPK activators, and emerging phytochemicals. The application of biomaterials (especially nanomaterials) to trigger autophagy is also an attractive research direction, which can exert superior therapeutic properties from the material-loaded molecules/drugs or the material's properties such as shape, roughness, surface chemistry, etc. All of these have essential clinical significance with the discovery of autophagy associated signals, pathways, mechanisms, and treatments in bone diseases in the future.Abbreviations: Δψm: mitochondrial transmembrane potential AMPK: AMP-activated protein kinase ARO: autosomal recessive osteosclerosis ATF4: activating transcription factor 4 ATG: autophagy-related β-ECD: β-ecdysone BMSC: bone marrow mesenchymal stem cell ER: endoplasmic reticulum FOXO: forkhead box O GC: glucocorticoid HIF1A/HIF-1α: hypoxia inducible factor 1 subunit alpha HSC: hematopoietic stem cell HSP: heat shock protein IGF1: insulin like growth factor 1 IL1B/IL-1β: interleukin 1 beta IVDD: intervertebral disc degradation LPS: lipopolysaccharide MAPK: mitogen-activated protein kinase MSC: mesenchymal stem cell MTOR: mechanistic target of rapamycin kinase NP: nucleus pulposus NPWT: negative pressure wound therapy OA: osteoarthritis OP: osteoporosis PTH: parathyroid hormone ROS: reactive oxygen species SIRT1: sirtuin 1 SIRT3: sirtuin 3 SQSTM1/p62: sequestosome 1 TNFRSF11B/OPG: TNF receptor superfamily member 11b TNFRSF11A/RANK: tumor necrosis factor receptor superfamily, member 11a TNFSF11/RANKL: tumor necrosis factor (ligand) superfamily, member 11 TSC1: tuberous sclerosis complex 1 ULK1: unc-51 like autophagy activating kinase 1.

Development of SiC-TiO2-Graphene neem extracted antimicrobial nano membrane for enhancement of multiphysical properties and future prospect in dental implant applications

This paper presents the coating technology on Nano membrane using SiC-TiO2-Graphene with varying percentages of Azadirachta indica (Neem) extract with an objective to develop new coating materials. The nanomembranes have been synthesized by electrospinning machine over aluminum foil paper using the raw materials PVA grain, SiC, TiO2, Graphene, and neem. The nanomembranes have been characterized by SEM, XRD, FTIR, Surface Roughness, antibacterial, and Cytotoxicity test. FTIR analysis established the presence of PVA and neem indicating the formation of different organic compounds. It also confirmed that no chemical reaction occurred during the synthesis process. The membrane's roughness analysis obtained average roughness values from 1.15 to 3.84. The formation of homogeneous and smooth membranes with the formation of micropores was confirmed by SEM analysis. Miller Indices identified different types of crystal structures in XRD analysis. Antibacterial activity increased with the increase of the percentage of neem confirmed by the antibacterial test. No toxic effects were observed from the membrane during the cytotoxicity test. The obtained data confirmed that the synthesized nanomembrane could be used in different biomedical applications.

Gold nanoparticles targeting the autophagy-lysosome system to combat the inflammation-compromised osteogenic potential of periodontal ligament stem cells: From mechanism to therapy

Although substantial data indicate that the osteogenic potential of periodontal ligament stem cells (PDLSCs) is compromised under inflammatory conditions, the underlying mechanism remains largely unexplored. In this study, we found that both the autophagy levels and autophagic flux levels were decreased in PDLSCs incubated under inflammatory conditions (I-PDLSCs). Based on the increased expression of LC3 II (at an autophagy level) and decreased accumulation of LC3 II (at an autophagic flux level) in I-PDLSCs, we speculated that the disruption of I-PDLSC autophagy arose from dysfunction of the cellular autophagy-lysosome system. Subsequently, our hypothesis was demonstrated by inhibited autophagosome-lysosome fusion, damaged lysosomal function, and suppressed activation of transcription factor EB (TFEB, a master regulator of the autophagy-lysosome system) in I-PDLSCs and verified by TFEB overexpression in I-PDLSCs. We found that gold nanoparticle (Au NP) treatment rescued the osteogenic potential of I-PDLSCs by restoring the inflammation-compromised autophagy-lysosome system. In this context, Au NP ceased to be effective when TFEB was knocked down in PDLSCs. Our data demonstrate the crucial role of the autophagy-lysosome system in cellular osteogenesis under inflammatory conditions and suggest a new target for rescuing inflammation-induced cell dysfunction using nanomaterials to aid cell biology and tissue regeneration.

Nanomaterials in Bone Regeneration

Nanomaterials are promising in the development of innovative therapeutic options that include tissue and organ replacement, as well as bone repair and regeneration. The expansion of new nanoscaled biomaterials is based on progress in the field of nanotechnologies, material sciences, and biomedicine. In recent decades, nanomaterial systems have bridged the line between the synthetic and natural worlds, leading to the emergence of a new science called nanomaterial design for biological applications. Nanomaterials replicating bone properties and providing unique functions help in bone tissue engineering. This review article is focused on nanomaterials utilized in or being explored for the purpose of bone repair and regeneration. After a brief overview of bone biology, including a description of bone cells, matrix, and development, nanostructured materials and different types of nanoparticles are discussed in detail.

Multimodal Potentials of Gold Nanoparticles for Bone Tissue Engineering and Regenerative Medicine: Avenues and Prospects

Osseous tissue repair has advanced due to the introduction of tissue engineering. The key elements required while engineering new tissues involve scaffolds, cells, and bioactive cues. The macrostructural to the nanostructural framework of such complex tissue has engrossed the intervention of nanotechnology for efficient neo-bone formation. Gold nanoparticles (GNPs) have recently gained interest in bone tissue regeneration due to their multimodal functionality. They are proven to modulate the properties of scaffolds and the osteogenic cells significantly. GNPs also influence different metabolic functions within the body, which directly or indirectly govern the mechanism of bone regeneration. Therefore, this review highlights nanoparticle-mediated osteogenic development, focusing on different aspects of GNPs ranging from scaffold modulation to cellular stimulation. The toxic aspects of gold nanoparticles studied so far are critically explicated, while further insight into the advancements and prospects of these nanoparticles in bone regeneration is also highlighted.

Detection and imaging of Hg(II) in vivo using glutathione-functionalized gold nanoparticles

The optical and biological properties of functionalized gold nanoparticles (GNPs) have been widely used in sensing applications. GNPs have a strong binding ability to thiol groups. Furthermore, thiols are used to bind functional molecules, which can then be used, for example, to detect metal ions in solution. Herein, we describe 13 nm GNPs functionalized by glutathione (GSH) and conjugated with a rhodamine 6G derivative (Rh6G2), which can be used to detect Hg(II) in cells. The detection of Hg²⁺ ions is based on an ion-catalyzed hydrolysis of the spirolactam ring of Rh6G2, leading to a significant change in the fluorescence of GNPs-GSH-Rh6G2 from an "OFF" to an "ON" state. This strategy is an effective tool to detect Hg²⁺ ions. In cytotoxicity experiments, GNPs-GSH-Rh6G2 could penetrate living cells and detect mercury ions through the fluorescent "ON" form.

Osteogenesis of Iron Oxide Nanoparticles-Labeled Human Precartilaginous Stem Cells in Interpenetrating Network Printable Hydrogel

Smart biomaterials combined with stem cell-based therapeutic strategies have brought innovation in the field of bone tissue regeneration. However, little is known about precartilaginous stem cells (PCSCs), which can be used as seed cells and incorporated with bioactive scaffolds for reconstructive tissue therapy of bone defects. Herein, iron oxide nanoparticles (IONPs) were employed to modulate the fate of PCSCs, resulting in the enhanced osteogenic differentiation potential both in vitro and in vivo. PCSCs were isolated from the ring of La-Croix extracted from polydactylism patient and identified through immunohistochemically staining using anti-FGFR-3 antibodies. Potential toxicity of IONPs toward PCSCs was assessed through cell viability, proliferation, and attachment assay, and the results demonstrated that IONPs exhibited excellent biocompatibility. After that, the effects of IONPs on osteogenic differentiation of PCSCs were evaluated and enhanced ALP activity, formation of mineralized nodule, and osteogenic-related genes expressions could be observed upon IONPs treatment. Moreover, in vivo bone regeneration assessment was performed using rabbit femur defects as a model. A novel methacrylated alginate and 4-arm poly (ethylene glycol)-acrylate (4A-PEGAcr)-based interpenetrating polymeric printable network (IPN) hydrogel was prepared for incorporation of IONPs-labeled PCSCs, where 4A-PEGAcr was the common component for three-dimensional (3D) printing. The implantation of IONPs-labeled PCSCs significantly accelerated the bone formation process, indicating that IONPs-labeled PCSCs could endow current scaffolds with excellent osteogenic ability. Together with the fact that the IONPs-labeled PCSCs-incorporated IPN hydrogel (PCSCs-hydrogels) was biosafety and printable, we believed that PCSCs-hydrogels with enhanced osteogenic bioactivity could enrich the stem cell-based therapeutic strategies for bone tissue regeneration.

Dental-derived mesenchymal stem cell sheets: a prospective tissue engineering for regenerative medicine

Stem cells transplantation is the main method of tissue engineering regeneration treatment, the viability and therapeutic efficiency are limited. Scaffold materials also play an important role in tissue engineering, whereas there are still many limitations, such as rejection and toxic side effects caused by scaffold materials. Cell sheet engineering is a scaffold-free tissue technology, which avoids the side effects of traditional scaffolds and maximizes the function of stem cells. It is increasingly being used in the field of tissue regenerative medicine. Dental-derived mesenchymal stem cells (DMSCs) are multipotent cells that exist in various dental tissues and can be used in stem cell-based therapy, which is impactful in regenerative medicine. Emerging evidences show that cell sheets derived from DMSCs have better effects in the field of regenerative medicine applications. Extracellular matrix (ECM) is the main component of cell sheets, which is a dynamic repository of signalling biological molecules and has a variety of biological functions and may play an important role in the application of cell sheets. In this review, we summarized the application status, mechanisms that sheets and ECM may play and future prospect of DMSC sheets on regeneration medicine.

Cerium oxide nanoparticles loaded nanofibrous membranes promote bone regeneration for periodontal tissue engineering

Bone regeneration is a crucial part in the treatment of periodontal tissue regeneration, in which new attempts come out along with the development of nanomaterials. Herein, the effect of cerium oxide nanoparticles (CeO2 NPs) on the cell behavior and function of human periodontal ligament stem cells (hPDLSCs) was investigated. Results of CCK-8 and cell cycle tests demonstrated that CeO2 NPs not only had good biocompatibility, but also promoted cell proliferation. Furthermore, the levels of alkaline phosphatase activity, mineralized nodule formation and expressions of osteogenic genes and proteins demonstrated CeO2 NPs could promote osteogenesis differentiation of hPDLSCs. Then we chose electrospinning to fabricate fibrous membranes containing CeO2 NPs. We showed that the composite membranes improved mechanical properties as well as realized release of CeO2 NPs. We then applied the composite membranes to in vivo study in rat cranial defect models. Micro-CT and histopathological evaluations revealed that nanofibrous membranes with CeO2 NPs further accelerated new bone formation. Those exciting results demonstrated that CeO2 NPs and porous membrane contributed to osteogenic ability, and CeO2 NPs contained electrospun membrane may be a promising candidate material for periodontal bone regeneration.

Gold nanotheranostics: future emblem of cancer nanomedicine

Cancer nanotheranostics aims at providing alternative approaches to traditional cancer diagnostics and therapies. In this context, plasmonic nanostructures especially gold nanostructures are intensely explored due to their tunable shape, size and surface plasmon resonance (SPR), better photothermal therapy (PTT) and photodynamic therapy (PDT) ability, effective contrast enhancing ability in Magnetic Resonance imaging (MRI) and Computed Tomography (CT) scan. Despite rapid breakthroughs in gold nanostructures based theranostics of cancer, the translation of gold nanostructures from bench side to human applications is still questionable. The major obstacles that have been facing by nanotheranostics are specific targeting, poor resolution and photoinstability during PTT etc. In this regard, various encouraging studies have been carried out recently to overcome few of these obstacles. Use of gold nanocomposites also overcomes the limitations of gold nanostructure probes and emerged as good nanotheranostic probe. Hence, the present article discusses the advances in gold nanostructures based cancer theranostics and mainly emphasizes on the importance of gold nanocomposites which have been designed to decipher the past questions and limitations of in vivo gold nanotheranostics.

Visible Light-Mediated Sustainable Antibacterial Activity and Osteogenic Functionality of Au and Pt Multi-Coated TiO2 Nanotubes

The visible light reactions of noble metal-based photocatalysts have been increasingly utilized to investigate their antibacterial activities. Furthermore, the photoreactions at various visible light wavelengths for specific combinations of titania nanotubes and noble metal nanoparticles have been found to promote osteogenic functionality. In this investigation, a novel multi-coating combination of noble metals (gold and platinum) on titania nanotubes was assessed using plasmonic photocatalysis and low-level laser therapy at 470 and 600 nm. The results showed that this coating on the nanotubes promoted antibacterial activity and osteogenic functionality. The order in which the gold and platinum coatings were layered onto the titania nanotubes strongly affected the osteogenic performance of the human mesenchymal stem cells. These results have identified a new approach for the development of efficient novel combinations of noble metal nanoparticles and titania nanotubes with visible light responses, sustainable antimicrobial activity, and osteogenic functionality.

Metallic Nanoscaffolds as Osteogenic Promoters: Advances, Challenges and Scope

Bone injuries and fractures are often associated with post-surgical failures, extended healing times, infection, a lack of return to a normal active lifestyle, and corrosion associated allergies. In this regard, this review presents a comprehensive report on advances in nanotechnology driven solutions for bone tissue engineering. The fabrication of metals such as copper, gold, platinum, palladium, silver, strontium, titanium, zinc oxide, and magnetic nanoparticles with tunable physico-chemical and opto-electronic properties for osteogenic scaffolds is discussed here in detail. Furthermore, the rational selection of a polymeric base such as chitosan, collagen, poly (L-lactide), hydroxyl-propyl-methyl cellulose, poly-lactic-co-glycolic acid, polyglucose-sorbitol-carboxymethy ether, polycaprolactone, natural rubber latex, and silk fibroin for scaffold preparation is also discussed. These advanced materials and fabrication strategies not only provide for appropriate mechanical strength but also render integrity, making them appealing for orthopedic applications. Further, such scaffolds can be functionalized with ligands or biomolecules such as hydroxyapatite, polypyrrole (PPy), magnesium, zinc dopants, and growth factors to stimulate osteogenic differentiation, mineralization, and neovascularization to aid in rapid healing. Future directions to co-incorporate bioceramics, biogenic nanoparticles, and fourth generation biomaterials to enhance biocompatibility, mechanical properties, and rapid recovery are also included in this review. Hence, the further development of such biomimetic metal-based nano-scaffolds at a lower cost with reduced risks and greater efficacy at regrowing bone can revolutionize the future of orthopedics.

Discoidin domain receptors (DDRs): Potential implications in periodontitis

Periodontitis is a chronic inflammatory disease leading to the destruction of periodontal tissues associated with high prevalence and significant economic burden. As special collagen-binding tyrosine kinase receptors, the discoidin domain receptors (DDRs) can control cell migration, adhesion, proliferation, and extracellular matrix remodeling. DDRs are constitutively expressed and widely distributed in periodontal tissues which are rich in collagen. Ddr1/2 knockout mice showed significant periodontal defects including connective tissue destruction, alveolar bone loss, and even tooth loss. It has been demonstrated that bone homeostasis, inflammation, matrix metalloproteinases, and autophagy are crucial characteristics involved in the pathogenesis of periodontitis. Of note, DDRs have been reported to participate in the above pathophysiological processes, implicating the potential roles of DDRs in periodontitis. In this review article, we aim to illustrate the possible roles of DDRs in periodontitis in an attempt to explore their potential value as therapeutic targets for periodontitis.

Enhancement of osteoporotic bone regeneration by strontium-substituted 45S5 bioglass via time-dependent modulation of autophagy and the Akt/mTOR signaling pathway

Osteoporosis (OP) is a major systemic bone disease leading to an imbalance in bone homeostasis which remains a challenge in the current treatment of bone defects. Our previous studies on strontium (Sr) doping apparently stimulated osteogenesis of bioceramics, which suggested a promising strategy for the treatment of bone defects. However, the potential effects and the underlying mechanisms of Sr-doping on osteoporotic bone defects still remain unclear. Autophagy is a conventional self-degradation process of cells involved in bone homeostasis and regeneration under physiological and pathological conditions. Therefore, it is essential to design appropriate biomaterials and investigate the associated osteogenic mechanisms via autophagy. Based on this hypothesis, Sr-doped 45S5 bioglass (Sr/45S5) was fabricated, and ovariectomy bone marrow-derived mesenchymal stem cells (OVX-BMSCs) were applied as the in vitro cell culture model. First, the optimal Sr-doping concentration of 10 mol% was screened by cell proliferation, ALP staining, alizarin red S staining and the real-time PCR assay. Then, the results of western blot (WB) analysis showed that Sr-induced osteogenic differentiation of OVX-BMSCs was associated with time-dependent modulation of autophagy and related to the AKT/mTOR signaling pathway. Meanwhile, the autophagy in Sr-induced osteogenic differentiation of OVX-BMSCs was detected by WB, immunofluorescence staining and transmission electron microscopy. Furthermore, the effect of osteogenic differentiation of OVX-BMSCs has been significantly inhibited by the administration of autophagy inhibitors and the AKT/mTOR pathway inhibitors, respectively, in the early and late periods of osteogenic differentiation. Finally, the results of the model of femoral condyle defects in OVX-rats indicated that Sr10/45S5 granules remarkably enhanced bone regeneration which provided the evidences in vivo. Our research indicates that Sr-doping provides a promising strategy to promote osteogenic differentiation of OVX-BMSCs and bone regeneration in osteoporotic bone defects via early improvement of autophagy and late activation of the Akt/mTOR signaling pathway.

Synergistic effect of electromagnetic fields and nanomagnetic particles on osteogenesis through calcium channels and p-ERK signaling

Electromagnetic fields (EMFs) are widely used in a number of cell therapies and bone disorder treatments, and nanomagnetic particles (NMPs) also promote cell activity. In this study, we investigated the synergistic effects of EMFs and NMPs on the osteogenesis of the human Saos-2 osteoblast cell line and in a rat calvarial defect model. The Saos-2 cells and critical-size calvarial defects of the rats were exposed to EMF (1 mT, 45 Hz, 8 h/day) with or without Fe₃ O₄ NMPs. Biocompatibility was evaluated with MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and LDH (lactate dehydrogenase) assays. This analysis showed that NMP and EMF did not induce cell toxicity. Quantitative reverse-transcription polymerase chain reaction indicated that the osteogenesis-related markers were highly expressed in the NMP-incorporated Saos-2 cells after exposure to EMF. Also, the expression of gene-encoding proteins involved in calcium channels was activated and the calcium concentration of the NMP-incorporated + EMF-exposed group was increased compared with the control group. In particular, in the NMP-incorporated + EMF-exposed group, all osteogenic proteins were more abundantly expressed than in the control group. This indicated that the NMP incorporation + EMF exposure induced a signaling pathway through activation of p-ERK and calcium channels. Also, in vivo evaluation revealed that rat calvarial defects treated with EMFs and NMPs had good regeneration results with new bone formation and increased mineral density after 6 weeks. Altogether, these results suggest that NMP treatment or EMF exposure of Saos-2 cells can increase osteogenic activity and NMP incorporation following EMF exposure which is synergistically efficient for osteogenesis.

Gold Nanomaterials and Bone/Cartilage Tissue Engineering: Biomedical Applications and Molecular Mechanisms

Recently, as our population increasingly ages with more pressure on bone and cartilage diseases, bone/cartilage tissue engineering (TE) have emerged as a potential alternative therapeutic technique accompanied by the rapid development of materials science and engineering. The key part to fulfill the goal of reconstructing impaired or damaged tissues lies in the rational design and synthesis of therapeutic agents in TE. Gold nanomaterials, especially gold nanoparticles (AuNPs), have shown the fascinating feasibility to treat a wide variety of diseases due to their excellent characteristics such as easy synthesis, controllable size, specific surface plasmon resonance and superior biocompatibility. Therefore, the comprehensive applications of gold nanomaterials in bone and cartilage TE have attracted enormous attention. This review will focus on the biomedical applications and molecular mechanism of gold nanomaterials in bone and cartilage TE. In addition, the types and cellular uptake process of gold nanomaterials are highlighted. Finally, the current challenges and future directions are indicated.

Inhibiting PHD2 in human periodontal ligament cells via lentiviral vector-mediated RNA interference facilitates cell osteogenic differentiation and periodontal repair

Periodontal defect regeneration in severe periodontitis remains a challenging task in clinic owing to poor survival of seed cells caused by the remaining oxidative stress microenvironment. Recently, the reduction of prolyl hydroxylase domain-containing protein 2 (PHD2), a primary cellular oxygen sensor, has shown an incredible extensive effect on skeletal muscle tissue regeneration by improving cell resistance to reactive oxygen species, whereas its role in periodontal defect repair is unclear. Here, through lentivirus vector-mediated RNA interference, the PHD2 gene in human periodontal ligament cells (hPDLCs) is silenced, leading to hypoxia-inducible factor-1α stabilization in normoxia. In vitro, PHD2 silencing not only exhibited a satisfactory effect on cell proliferation, but also induced distinguished osteogenic differentiation of hPDLCs. Real-time polymerase chain reaction and Western blotting revealed significant up-regulation of osteocalcin, alkaline phosphatase (ALP), runt-related transcription factor 2, and collagen type I (COL I). Under oxidative stress conditions, COL I and ALP expression levels, suppressed by 100 μM H₂ O₂ , were elevated by PHD2-gene-silencing in hPDLCs. In vivo, periodontal fenestration defects were established in 18 female Sprague-Dawley rats aged 6 wk old, followed by implantation of PHD2 silencing hPDLCs in situ for 21 d. Persistent and stable silencing of PHD2 in hPDLCs promoted better new bone formation according to microcomputed tomography 3D reconstruction and related bone parameter analysis. This work demonstrates the therapeutic efficiency of PHD2 gene interference in osteogenic differentiation and periodontal defect repair for highly efficient periodontal regeneration.

Citrate-Stabilized Gold Nanorods-Directed Osteogenic Differentiation of Multiple Cells

Objective

Gold nanorods (AuNRs) show great potential for versatile biomedical applications, such as stem cell therapy and bone tissue engineering. However, as an indispensable shape-directing agent for the growth of AuNRs, cetyltrimethylammonium bromide (CTAB) is not optimal for biological studies because it forms a cytotoxic bilayer on the AuNR surface, which interferes with the interactions with biological cells.

Methods

Citrate-stabilized AuNRs with various aspect-ratios (Cit-NRI, Cit-NRII, and Cit-NRIII) were prepared by the combination of end-selective etching and poly(sodium 4-styrenesulfonate)-assisted ligand exchange method. Their effects on osteogenic differentiation of the pre-osteoblastic cell line (MC3T3-E1), rat bone marrow mesenchymal stem cells (rBMSCs), and human periodontal ligament progenitor cells (PDLPs) have been investigated. Potential signaling pathway of citrate-stabilized AuNRs-induced osteogenic effects was also investigated.

Results

The experimental results showed that citrate-stabilized AuNRs have superior biocompatibility and undergo aspect-ratio-dependent osteogenic differentiation via expression of osteogenic marker genes, alkaline phosphatase (ALP) activity and formation of mineralized nodule. Furthermore, Wnt/β-catenin signaling pathway might provide a potential explanation for the citrate-stabilized AuNRs-mediated osteogenic differentiation.

Conclusion

These findings revealed that citrate-stabilized AuNRs with great biocompatibility could regulate the osteogenic differentiation of multiple cell types through Wnt/β-catenin signaling pathway, which promote innovative AuNRs in the field of tissue engineering and other biomedical applications.

l-cysteine-modified chiral gold nanoparticles promote periodontal tissue regeneration

Gold nanoparticles (AuNPs) with surface-anchored molecules present tremendous potential in tissue regeneration. However, little is known about chiral-modified AuNPs. In this study, we successfully prepared L/D-cysteine-anchored AuNPs (L/D-Cys-AuNPs) and studied the effects of chiral-modified AuNPs on osteogenic differentiation and autophagy of human periodontal ligament cells (hPDLCs) and periodontal tissue regeneration. In vitro, more L-Cys-AuNPs than D-Cys-AuNPs tend to internalize in hPDLCs. L-Cys-AuNPs also significantly increased the expression of alkaline phosphatase, collagen type 1, osteocalcin, runt-related transcription factor 2, and microtubule-associated protein light chain 3 II and decreased the expression of sequestosome 1 in hPDLCs compared to the expression levels in the hPDLCs treated by D-Cys-AuNPs. In vivo tests in a rat periodontal-defect model showed that L-Cys-AuNPs had the greatest effect on periodontal-tissue regeneration. The activation of autophagy in L-Cys-AuNP-treated hPDLCs may be responsible for the cell differentiation and tissue regeneration. Therefore, compared to D-Cys-AuNPs, L-Cys-AuNPs show a better performance in cellular internalization, regulation of autophagy, cell osteogenic differentiation, and periodontal tissue regeneration. This demonstrates the immense potential of L-Cys-AuNPs for periodontal regeneration and provides a new insight into chirally modified bioactive nanomaterials.

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L/D-Cys-AuNPs exert a chirality-dependent effect on hPDLCs.

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L-Cys-AuNPs efficiently induced osteogenic differentiation in hPDLCs.

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L-Cys-AuNPs significantly improved periodontal tissue regeneration.

Gold Nanoparticles Combined Human β-Defensin 3 Gene-Modified Human Periodontal Ligament Cells Alleviate Periodontal Destruction via the p38 MAPK Pathway

Periodontitis is a chronic inflammatory disease with plaques as the initiating factor, which will induce the destruction of periodontal tissues. Numerous studies focused on how to obtain periodontal tissue regeneration in inflammatory environments. Previous studies have reported adenovirus-mediated human β-defensin 3 (hBD3) gene transfer could potentially enhance the osteogenic differentiation of human periodontal ligament cells (hPDLCs) and bone repair in periodontitis. Gold nanoparticles (AuNPs), the ideal inorganic nanomaterials in biomedicine applications, were proved to have synergetic effects with gene transfection. To further observe the potential promoting effects, AuNPs were added to the transfected cells. The results showed the positive effects of osteogenic differentiation while applying AuNPs into hPDLCs transfected by adenovirus encoding hBD3 gene. In vivo, after rat periodontal ligament cell (rPDLC) transplantation into SD rats with periodontitis, AuNPs combined hBD3 gene modification could also promote periodontal regeneration. The p38 mitogen-activated protein kinase (MAPK) pathway was demonstrated to potentially regulate both the in vitro and in vivo processes. In conclusion, AuNPs can promote the osteogenic differentiation of hBD3 gene-modified hPDLCs and periodontal regeneration via the p38 MAPK pathway.

Gold Nanoparticles Promote the Bone Regeneration of Periodontal Ligament Stem Cell Sheets Through Activation of Autophagy

OBJECTIVE

Cell sheet technology (CST) is advantageous for repairing alveolar bone defects in clinical situations, and osteogenic induction before implantation may result in enhanced bone regeneration. Herein, we observed the effect of gold nanoparticles (AuNPs) on osteogenic differentiation of periodontal ligament stem cell (PDLSC) sheets and explored their potential mechanism of action.

METHODS

PDLSCs were cultured in cell sheet induction medium to obtain cell sheets. PDLSC sheets were treated with or without AuNPs. Alkaline phosphatase, alizarin red S, von Kossa, and immunofluorescence staining were used to observe the effects of AuNPs on the osteogenic differentiation of PDLSC sheets. Western blotting was performed to evaluate the osteogenic effects and autophagy activity. The cell sheets were transplanted into the dorsa of nude mice, and bone regeneration was analyzed by micro-CT and histological staining.

RESULTS

AuNPs could promote the osteogenic differentiation of PDLSC sheets by upregulating bone-related protein expression and mineralization. The 45-nm AuNPs were more effective than 13-nm AuNPs. Additional analysis demonstrated that their ability to promote differentiation could depend on activation of the autophagy pathway through upregulation of microtubule-associated protein light chain 3 and downregulation of sequestosome 1/p62. Furthermore, AuNPs significantly promoted the bone regeneration of PDLSC sheets in ectopic models.

CONCLUSION

AuNPs enhance the osteogenesis of PDLSC sheets by activating autophagy, and 45-nm AuNPs were more effective than 13-nm AuNPs. This study may provide an AuNP-based pretreatment strategy for improving the application of CST in bone repair and regeneration.

Dendritic polyglycerol-conjugated gold nanostars with different densities of functional groups to regulate osteogenesis in human mesenchymal stem cells

Nanomaterials play an important role in mimicking the biochemical and biophysical cues of the extracellular matrix in human mesenchymal stem cells (MSCs). Increasing studies have demonstrated the crucial impact of functional groups on MSCs, while limited research is available on how the functional group's density on nanoparticles regulates MSC behavior. Herein, the effects of dendritic polyglycerol (dPG)-conjugated gold nanostars (GNSs) with different densities of functional groups on the osteogenesis of MSCs are systematically investigated. dPG@GNS nanocomposites have good biocompatibility and the uptake by MSCs is in a functional group density-dependent manner. The osteogenic differentiation of MSCs is promoted by all dPG@GNS nanocomposites, in terms of alkaline phosphatase activity, calcium deposition, and expression of osteogenic protein and genes. Interestingly, the dPGOH@GNSs exhibit a slight upregulation in the expression of osteogenic markers, while the different charged densities of sulfate and amino groups show more efficacy in the promotion of osteogenesis. Meanwhile, the sulfated nanostars dPGS20@GNSs show the highest enhancement. Furthermore, various dPG@GNS nanocomposites exerted their effects by regulating the activation of Yes-associated protein (YAP) to affect osteogenic differentiation. These results indicate that dPG@GNS nanocomposites have functional group density-dependent influence on the osteogenesis of MSCs, which may provide a new insight into regulating stem cell fate.

Gallium ions promote osteoinduction of human and mouse osteoblasts via the TRPM7/Akt signaling pathway

Gallium (Ga) ions have been widely utilized for biomedical applications; however, their role in osteoblast regulation is not completely understood. The aim of the present study was to investigate the potential effect of Ga ions on osteoinduction in two osteoblast cell lines and to explore the underlying mechanisms. Human hFOB1.19 and mouse MC3T3‑E1 osteoblasts were treated with Ga nitride (GaN) at different concentrations, and the degree of osteoinduction was assessed. Ga ion treatment was found to increase alkaline phosphatase activity and accelerate calcium nodule formation, as assessed using ALP activity assay and Alizarin red S staining. Moreover, upregulated expression levels of osteogenic proteins in osteoblasts were identified using western blotting and reverse transcription‑quantitative PCR. Western blotting was also performed to demonstrate that the biological action of Ga ions was closely associated with the transient receptor potential melastatin 7/Akt signaling pathway. Furthermore, it was found that Ga ions did not cause osteoblast apoptosis, as indicated via flow cytometry, but promoted osteoclast proliferation, migration or invasion. The present study investigated the potential role of Ga ions in regulating osteoinduction of osteoblasts, thereby providing a promising strategy for the treatment of osteoporosis.