Di Huang

A facile and one-pot synthesis of fluorescent graphitic carbon nitride quantum dots for bio-imaging applications

As a kind of metal-free polymer, graphitic carbon nitride (g-C3N4) has captivated considerable attention. In this work, an efficient one-pot, economical and green pathway was investigated to simultaneously prepare highly fluorescent g-C3N4 quantum dots (g-C3N4 QDs) and ultrathin g-C3N4 nanosheets via ethanol-thermal treatment of bulk g-C3N4 in the presence of KOH. The as-obtained g-C3N4 QDs exhibited narrow particle size distribution with an average diameter of 3.3 ± 0.3 nm. Benefiting from these alluring properties, such as excellent water solubility, bright blue fluorescence, favorable stability and good biocompatibility, the g-C3N4 QDs were successfully employed as a brand-new but promising candidate for bioimaging in vitro. Furthermore, this convenient strategy would open a new avenue for the large-scale synthesis of other layered materials.

Reinforced chitosan membranes by microspheres for guided bone regeneration

In order to improve the osteogenic activity and mechanical strength of the guided bone regeneration (GBR) membrane for repairing bone defect, nano-hydroxyapatite/chitosan (nHA/CS) composite microspheres were prepared through in situ biomimetic method, then composite microspheres were incorporated into CS membrane. The morphologies and mechanical properties of the composite membranes were investigated through scanning electronic microscopy (SEM) and universal mechanical testing machine. The results show that the in situ biomimetic nHA/CS microspheres were embedded in CS membrane and were integrated tightly with CS matrix. The mechanical properties of GBR membranes containing in situ nHA/CS microspheres is significantly higher than that of membranes containing pure CS microspheres and blending nHA/CS microspheres. Its elongation rate at break reaches 5.61 ± 0.95%. The elastic modulus and strength of the GBR membranes can reach 766.27 ± 20.68 and 43.32 ± 0.95 MPa, respectively. Further, The work-of-fracture of the membranes with in situ microspheres approaches 2.71 ± 0.25 J/m2, which is about 3 times of the pure CS membrane. The cell culture results display that the GBR membranes containing in situ biomimetic nHA/CS microspheres exhibit good cytocompatibility.

A synthetic peptide inhibits human ovarian cancer cell motility

Phage display libraries have been commonly used to identify recognition sites and antigen–antibody binding systems in tumor cells since the 1990s. In the previous study, we isolated a 12-mer binding peptide SVSVGMKPSPRP (SV-peptide) while isolating human ovarian cancer cells (SK-OV-3) using a random phage display library. Therefore, we tested the specific binding and anticancer properties of the SV-peptide with respect to cell viability and motility. The peptide-binding assay showed the immunofluorescent staining intensity of tumor cells (A2780, A549 and SK-OV-3) > control cells (HUVEC). Monolayer scratch healing and Transwell transmigration assays showed that the SV-peptide inhibited the migration of all three cancer cell types but not HUVEC. The mechanism involves a suppression of cytoskeletal F-actin filament arrangement into filopodia and lamellipodia through downregulation of Rac1 but not RhoA. The FAK–PI3K signaling pathway was also affected by the peptide. Western blot analysis revealed a downregulation of FAK, but not of PI3K, after 24 h incubation of SK-OV-3 cells with the SV-peptide. Metalloproteinase-2 (MMP-2) was also downregulated by the SV-peptide. Finally, the viability of cancer cell lines (SK-OV-3 and A549) decreased in the presence of the SV-peptide after 48 h. Transmission electron microscopy of the SV-peptide-exposed cancer cultures showed extensive vacuolization, swollen mitochondria, and rough endoplasmic reticulum. Thus, the SV-peptide has some certain application prospects in the tumor therapy.

A study of the initial adhesive force of cells on silk fibroin-based materials using micropipette aspiration

Abstract With the development of biomaterials, more attention is paid to the adhesion characteristics between cells and materials. It is necessary to study the adhesive force with a suitable method. Silk fibroin (SF) is widely investigated in biomedical application due to its novel biocompatibility and mechanical properties. In this article, the micropipette aspiration method and measurement pattern of uniform cells in round shape (UCR) was used to study the initial adhesive force of three types of cells on pure silk fibroin films (SFFs). We also compared the adhesive forces of modified SFFs with that of pure SFFs. The results of adhesive force in the initial adhesive stage were in concordance with the results of MTT assay and microscope observation, which were confirmed by the above three cell lines and four kinds of SFFs. The results indicated UCR was an efficient and quantitative measurement pattern in initial adhesion stage. This article also provides a useful method in identifying initial cell-materials interactions.

Rapid room-temperature preparation of MoO3−x quantum dots by ultraviolet irradiation for photothermal treatment and glucose detection

Oxygen deficient molybdenum oxide (MoO3−x) spurred intense scientific interest in biomedical research owing to the strong localized surface plasmon resonance (LSPR) effect in NIR region. Although a considerable number of methods have been used to prepare MoO3−x nanomaterials, most of them are limited by long reaction time, low yield and poor water solubility of the products. Herein, a novel ultraviolet irradiation method was developed to synthesize MoO3−x quantum dots (QDs) within 30 min, which rendered excellent water solubility and low cytotoxicity. The as-prepared MoO3−x QDs exhibited a relatively narrow size distribution with an average diameter of 5.63 nm, which was confirmed by transmission electron microscopy. Moreover, an intense LSPR effect in NIR regions was verified by UV-vis spectroscopy. Thus, the materials were used in photothermal ablation of cancer and glucose detection, showing high photothermal conversion efficiency and good sensitivity.

Effect of hydroxyapatite fillers on the mechanical properties and osteogenesis capacity of bio-based polyurethane composite scaffolds

A newly designed hydroxyapatite-polyurethane (HA-PU) composite scaffold was prepared by polymerizing glyceride of castor oil (GCO) with isophorone diisocyanate (IPDI) and HA as fillers. The aim of this study was to determine the effect of HA fillers on the mechanical properties and osteogenesis capacity of the composite scaffolds. The physical and biological properties of the scaffold were evaluated by SEM observation, mechanical testing, cell culture and animal experiments. The results showed that HA fillers enhanced the mechanical properties of PU composite scaffolds such as compressive strength and elastic modulus. The mechanical properties of the scaffolds were seen to increase with increase in HA loading. The compressive strength of composite scaffold with 0 wt%, 20 wt%, 40 wt% of HA was 0.6 ± 0.1 MPa, 2.1 ± 0.1 MPa, and 4.6 ± 0.3 MPa, respectively. In vitro biodegradation studies of scaffolds were carried out. The results showed that all of the scaffolds were susceptible to cholesterol esterase (CE) -catalyzed degradation. HA-PU composite scaffolds exhibited a high affinity to osteoblastic cells and were good template for cell growth and proliferation. When implanted in bone defects of rats, PU scaffolds incorporated HA were biocompatible with the tissue host and had no immune rejection. Moreover, the higher the loading of HA in the composite scaffold, the better chances of osteogenesis. It confirmed that the prepared HA-PU composite scaffolds can be promising candidate for bone repair and bone tissue engineering.

Preparation and characterization of porous hydroxyapatite/β-cyclodextrin-based polyurethane composite scaffolds for bone tissue engineering

In this study, novel porous scaffolds containing hydroxyapatite and β-cyclodextrin-based polyurethane were first successfully fabricated by polymerizing β-cyclodextrin with hexamethylene diisocyanate and hydroxyapatite in situ for bone tissue engineering. The physicochemical and mechanical properties as well as cytocompatibility of porous scaffolds were investigated. The results showed that polyurethane reinforced with hydroxyapatite composites had cancellous bone-like porous structure. The mechanical strength of the scaffolds increased with increasing the hydroxyapatite content in scaffolds. Synthesized scaffolds (PU1, PUHA1, PU2, and PUHA2) presented compressive strength values of 0.87 ± 0.24 MPa, 1.81 ± 0.10 MPa, 6.16 ± 0.89 MPa, and 12.95 ± 2.05 MPa, respectively. The pore size and porosity of these scaffolds were suitable for bone regeneration. Cytocompatibility of composite scaffolds was proven via favorable interactions with MC3T3-E1 cells. The addition of hydroxyapatite into CD-based polyurethane scaffolds improved cell attachment, well-spread morphology, and higher proliferation. The hydroxyapatite-polyurethane scaffolds have the potential to be applied in bone repair and regeneration.

Near-Ultraviolet to Near-Infrared Fluorescent Nitrogen-Doped Carbon Dots with Two-Photon and Piezochromic Luminescence

Carbon dots (CDs) have gained intensive interests owing to their unique structure and excellent optoelectronic performances. However, to acquire CDs with a broadband emission spectrum still remains an issue. In this work, nitrogen-doped CDs (N-CDs) with near-ultraviolet (NUV), visible, and near-infrared (NIR) emission were synthesized via one-pot solvothermal strategy, and the excitation-independent NUV and NIR emission and excitation-dependent visible emission were observed in the photoluminescence (PL) spectra of N-CDs. Moreover, the as-synthesized N-CDs displayed two-photon fluorescence emission. It is important to note that N-CDs also exhibited piezochromic luminescence with reversibility, in which the red- and blue-shifted PL with increasing applied pressure (0.07-5.18 GPa) and the red- and blue-shifted PL with releasing applied pressure (5.18 GPa to 1 atm) were developed for the first time. Combined with good hydrophilicity, high photobleaching resistance, and low toxicity, the piezochromic luminescence would greatly boost the valuable applications of N-CDs.

Aligned hydroxyapatite nano-crystal formation on a polyamide surface

Controlling the orientation of well-crystallized nano-hydroxyapatite (n-HA) remains a difficult task because of the complicated process of n-HA crystallization. In the present research, highly aligned n-HA arrays were fabricated on a polyamide matrix. The oriented n-HA crystals were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectric spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). The mechanism of how these structures form was explored. The results show that the oriented n-HA arrays are formed on a calcium treated polyamide matrix. The diameter of the n-HA columns is about 47.41 ± 3.02 nm. The n-HA crystals grow vertically with the substrate and the length of the crystals is 613.423 ± 61.57 nm. Osteoblast-like MG63 cells were cultured on the nano-crystals in order to demonstrate the biocompatibility of these oriented n-HA crystals. The MTT assay suggests that the oriented n-HA crystals could promote cell proliferation. The overall results indicate the promising potential of oriented n-HA crystals for bone regeneration.

The Influences of a Targeting Peptide on the Ovarian Cancer Cell Motility

Tumor metastasis is the major cause of death from ovarian cancer. Therefore, targeted therapy, which could prevent the ability of cells to metastasize to different organs, is an effective treatment for ovarian cancer at present. Previous study indicated that the peptide WSGPGVWGASVK (WSG) inhibited the adhesive ability of SK-OV-3 to extracellular matrix. For further study, we have investigated the effects of the peptide WSG on the ovarian cancer cell migration. Results showed that WSG peptide promoted the migration of SK-OV-3 and HUVEC cells through regulating the expression of talin and (p)-paxilin protein. Besides, WSG peptide inhibited the SK-OV-3 viability. The expression of human matrix metalloproteinase MMP-2 and MMP-9 of SK-OV-3 cells was inhibited. All these results suggested that peptide WSG might be used in ovarian cancer therapy.