Carbon dots enhance extracellular matrix secretion for dentin-pulp complex regeneration through PI3K/Akt/mTOR pathway-mediated activation of autophagy.

Pulp injury is one of the most common clinical diseases, and severe cases are usually associated with the functional loss of the tooth, while the current clinical treatment modality is only a cavity filling procedure without the regeneration of the dentin-pulp complex, thus leading to a devitalized and brittle tooth. In this study, carbon dots (CDots) with excellent biocompatibility are prepared from ascorbic acid and polyethyleneimine via a hydrothermal method. The as-prepared CDots can enhance extracellular matrix (ECM) secretion of human dental pulp stem cells (DPSCs), giving rise to increased cell adhesion on ECM and a stronger osteogenic/odontogenic differentiation capacity of DPSCs. Further, the mechanism underlying CDots-enhanced ECM secretion is revealed by the transcriptome analysis, Western blot assay and molecular dynamics simulation, identifying that the pharmacological activities of CDots are originated from a reasonable activation of the autophagy, which is mediated by regulating phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin signaling pathway. Based on the abundant CDots-induced ECM and thereby the reinforcement of the cell-ECM adhesion, an intact dental pulp stem cell sheet can be achieved, which in return promote in vivo the efficient regeneration of dentin-pulp complex as well as blood vessels.

Modification of Metal-Organic Framework Nanoparticles Using Dental Pulp Mesenchymal Stem Cell Membranes to Target Oral Squamous Cell Carcinoma.

Engineering a targetable nanoparticle to tumor cell is a challenge issue for clinical application. Our results demonstrated that the chemokine CXCL8 secreted by oral squamous cell carcinoma (OSCC) could act as a chemoattractant to attract dental pulp mesenchymal stem cell (DPSC), which expressed the CXCL8 binding receptor, CXCR2, to the OSCC. Therefore, to create OSCC targetable nanoparticles, we used DPSC membranes to modify nanoparticles of metal-organic framework nanoparticles (MOFs) resulting in a novel MOF@DPSCM nanoparticle. Interestingly, results from in vitro and in vivo experiments illustrated that MOF@DPSCM possessed specificity for the OSCC, and the MOF@DPSCM carried DOX (doxorubicin), MOF-DOX@DPSCM could induce CAL27 cell death in vitro and block CAL27 tumor growth in vivo. Our data suggest that this novel MOF-DOX@DPSCM nanoparticle is a potential targetable drug delivery system for the OSCC in the future clinical application.

Ascorbic Acid-PEI Carbon Dots with Osteogenic Effects as miR-2861 Carriers to Effectively Enhance Bone Regeneration.

Nucleic acid transfer has shown significant potential in the treatment of bone damage because of its long lasting local effect and lower cost. Nonviral vectors, such as nanomaterials, with higher biocompatibility are increasedly applied in the study of bone defect repair. Carbon dots with various reactive groups on the surface not only provide a unique surface to carry therapeutic genes, but also some carbon dots have been reported to promote osteogenic differentiation. The bone regeneration effect of carbon dots in vivo, however, is rarely investigated. MiR-2861 has revealed osteogenic differentiation effects. In the current study, we created ascorbic acid-PEI carbon dots (CD), which were able to carry miR-2861, by the microwave-assisted pyrolysis method. Results demonstrated that CD had excellent fluorescence stability leading to good fluorescence imaging in vitro and in vivo. CD was efficiently internalized into bone marrow stromal cells (BMSCs) through the clathrin-mediated endocytosis pathway and distributed in the mitochondria, endoplasmic reticulum, lysosome, and nucleus. Results from alkaline phosphatase staining, alizarin red staining, and reverse transcription real-time PCR (RT-QPCR) showed that our CD indeed had osteogenic effects in vitro. Flow cytometry data indicated that CD could efficiently deliver miR-2861 into BMSCs in vitro, and CD carrying miR-2861 (CD@miR) had the strongest osteogenic effects. Analyses of hematology, serum biochemistry, and histology showed that CD and CD@miR did not have cytotoxicity and had higher biocompatibility in vivo. Most interestingly, CD and miR-2861 in the CD@miR could act synergistically to promote osteogenic differentiation in vitro and new bone regeneration in vivo remarkably. Our results clearly indicate that the osteogenic CD delivering osteogenic therapeutic gene, miR-2861, can obtain much stronger bone regeneration ability, suggesting that our CD has great potential in future clinical application.

Controllable acidophilic dual-emission fluorescent carbonized polymer dots for selective imaging of bacteria.

Fluorescent materials can be powerful contrast agents in photoelectric devices and for bioimaging. As emerging fluorescent materials, carbonized polymer dots (CPDs) with high quantum yields (QYs), long-wavelength emission and multiple functions are highly desired. Despite great progress in the synthetic methods and QYs of CPDs, multiple emission of CPDs is challenging. Therefore, we developed CPDs with dual-emission fluorescence in terms of inherent blue and red emission. In addition, CPDs with sole blue emission (B-CPDs) and red emission (R-CPDs) were synthesized, respectively, by regulating the reaction conditions to control the quantitative structure and emission centers. The absolute QY of R-CPDs in water was 24.33%. These three types of CPDs with dual/sole emission could be used in optoelectronic and bioimaging applications. With different CPDs coated on a commercially available gallium nitride light-emitting diode chip as a color-conversion layer, LEDs with blue, yellow, and red emission were achieved. Benefiting from the different emission intensities and emission peaks of R/B-CPDs in different pH conditions, they were used (without further modification) to distinguish between Porphyromonas gingivalis, Streptococcus mutans, Escherichia coli and Staphylococcus aureus in dental plaque biofilms (the first time this has been demonstrated). These findings could enable a new development direction of CPDs based on the design of multi-emission centers.

Synthesis, characterization and evaluation of a fluorinated resin monomer with low water sorption.

A fluorinated acrylate monomer (4-TF-PQEA) without BPA (bisphenol-A) structure was synthesized and mixed with triethylene glycol dimethacrylate (TEGDMA) to used as dental resin system in order to achieve lower water sorption and reduce human exposure to BPA derivatives. Double bond conversion (DC) was measured using Fourier transform infrared spectroscopy (FTIR). Water sorption (WS), water solution (WL) and depth of cure (DOC) were evaluated according to ISO 4049:2009. Water contact angle (CA) was measured using contact angle analyzer. Polymerization shrinkage (PS) was evaluated according to the Archimedes' principle and ISO 17304:2013. Flexural strength (FS) and flexural modulus (FM) were measured by three-point bending test with a universal testing machine according to ISO 4049:2009. Comprehensive strength (CS) and vickers microhardness (VM) were also investigated. Thermal stability test was measure by Thermogravimetric analyzer. Cytotoxicity of three resin systems was tested through MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromid) cytotoxicity method according to the ISO 10993-5:2009. Bisphenol-A glycidyl dimethacrylate (Bis-GMA)/ TEGDMA resin system was used as a control. The results show that 4-TF-PQEA/TEGDMA resin system had lower PS, lower WS and higher DC values than those of Bis-GMA/TEGDMA resin system except some mechanical properties, such as FS, FM and CS. Moreover, properties of other 4-TF-PQEA-containing resin systems were also comparable with those of Bis-GMA/TEGDMA resin system. In particular, the overall performance of resin system consisted of 4-TF-PQEA/Bis-GMA/TEGDMA is optimized when the mixture ratio is 30/40/30(wt/wt/wt). Therefore, the 4-TF-PQEA has potential to be used as resin monomer for dental resin composites to achieve lower water sorption.

Preparation and characterization of silane-modified SiO2 particles reinforced resin composites with fluorinated acrylate polymer.

A series of fluorinated dental resin composites were prepared with two kinds of SiO2 particles. Bis-GMA (bisphenol A-glycerolate dimethacrylate)/4-TF-PQEA (fluorinated acrylate monomer)/TEGDMA (triethylene glycol dimethacrylate) (40/30/30, wt/wt/wt) was introduced as resin matrix. SiO2 nanopartices (30nm) and SiO2 microparticles (0.3µm) were silanized with 3-methacryloxypropyl trimethoxysilane (γ-MPS) and used as fillers. After mixing the resin matrix with 0%, 10%, 20%, 30% SiO2 nanopartices and 0%, 10%, 20%, 30%, 40%, 50% SiO2 microparticles, respectively, the fluorinated resin composites were obtained. Properties including double bond conversion (DC), polymerization shrinkage (PS), water sorption (Wp), water solubility (Wy), mechanical properties and cytotoxicity were investigated in comparison with those of neat resin system. The results showed that, filler particles could improve the overall performance of resin composites, particularly in improving mechanical properties and reducing PS of composites along with the addition of filler loading. Compared to resin composites containing SiO2 microparticles, SiO2 nanoparticles resin composites had higher DC, higher mechanical properties, lower PS and lower Wp under the same filler content. Especially, 50% SiO2 microparticles reinforced resins exhibited the best flexural strength (104.04 ± 7.40MPa), flexural modulus (5.62 ± 0.16GPa), vickers microhardness (37.34 ± 1.13 HV), compressive strength (301.54 ± 5.66MPa) and the lowest polymerization (3.42 ± 0.22%).

Aspirin-Based Carbon Dots, a Good Biocompatibility of Material Applied for Bioimaging and Anti-Inflammation.

The emerging photoluminescent carbon-based nanomaterials are promising in various fields besides cell imaging and carrier transport. Carbon nanomaterials with specific biological functions, however, are rarely investigated. Aspirin is a very common anti-inflammatory medication to relieve aches and pains. In this study, we have tried to create a carbon nanoparticle with aspirin, and we expect that this new carbon nanoparticle will have both anti-inflammatory and fluorescent biomarker functions. Fluorescent aspirin-based carbon dots (FACDs) were synthesized by condensing aspirin and hydrazine through a one-step microwave-assisted method. Imaging data demonstrated that FACDs efficiently entered into human cervical carcinoma and mouse monocyte macrophage cells in vitro with low cell toxicity. Results from quantitative polymerase chain reaction and histological analysis indicated that FACDs possessed effective anti-inflammatory effects in vitro and in vivo compared to aspirin only. Hematology, serum biochemistry, and histology results suggested that FACDs also had no significant toxicity in vivo. Our results clearly demonstrate that FACDs have dual functions, cellular imaging/bioimaging and anti-inflammation, and suggest that FACDs have great potential in future clinical applications.