Lin Jin

Fabrication, mechanical properties, and biocompatibility of reduced graphene oxide-reinforced nanofiber mats

Fibrous functional scaffolds that could mimic the natural growth environment of cells and govern cell-specific behaviors are crucial for meeting the requirements of tissue engineering. Graphene-based materials, which is an important one of them have captured tremendous interests of researchers. However, few research about graphene nanofibers with excellent electrical and mechanical properties have been fabricated and found to have real applications. In this study, we reported a novel PAN-reduced graphene oxide reinforced composite nanofiber mats (rGO–NFMs), which were fabricated by the electrospinning process combined with chemical reduction. SEM, FTIR and XRD revealed that rGO–NFMs were successfully produced. These rGO–NFMs displayed superior mechanical properties (tensile strain and tensile stress are 18.5% and 1.38 MPa, respectively). The cell proliferation and morphology of adipose-derived stem cells (ADSCs as model cells) cultured on the rGO–NFMs were tested with a 7 days culture period. Cellular test results showed that rGO–NFMs exhibited excellent biocompatibility, cells on the nanofibers formed stable cell–fiber constructs, and the rate of cell proliferation was similar to that of tissue culture plates (TCPs) and PAN nanofibers mats (PAN–NFMs). This study demonstrated that rGO–NFMs may be a good choice for application in tissue engineering, particularly cell culture scaffolds for electrical stimulation.

Multi-color luminescence of uniform CdWO4 nanorods through Eu3+ ion doping

Uniform Eu3+ doped CdWO4 nanorods were prepared via a simple hydrothermal method and characterized by X-ray diffraction, transmission electron microscopy, photoluminescence (PL) spectroscopy and PL lifetime measurements. The results indicate that the obtained Eu3+ doped CdWO4 nanorods have monoclinic phase structure, and the phase structure can be retained at Eu3+ doping concentrations of 0.4–4.0%. The diameter of nanorods decreases from 27 to 15 nm with an increase in the doping concentrations, and the morphology becomes irregular at the Eu3+ doping concentration of 6.5%. Under the excitation of ultraviolet light, the relative intensities of blue-green emission ascribed to WO42− and red emission from Eu3+ can be tuned through doping Eu3+ ions into the CdWO4 nanorods and thus altering the energy transfer between WO42− and Eu3+. Hence, the multi-color luminescence in the same host at a single excited wavelength can be realized simply by altering the doping concentration of Eu3+. These luminescent nanomaterials may have potential applications in displays, light sources, bio-imaging and so on.

Fabrication, Characterization, and Biocompatibility of Polymer Cored Reduced Graphene Oxide Nanofibers

Graphene nanofibers have shown a promising potential across a wide spectrum of areas, including biology, energy, and the environment. However, fabrication of graphene nanofibers remains a challenging issue due to the broad size distribution and extremely poor solubility of graphene. Herein, we report a facile yet efficient approach for fabricating a novel class of polymer core-reduced graphene oxide shell nanofiber mat (RGO-CSNFM) by direct heat-driven self-assembly of graphene oxide sheets onto the surface of electrospun polymeric nanofibers without any requirement of surface treatment. Thus-prepared RGO-CSNFM demonstrated excellent mechanical, electrical, and biocompatible properties. RGO-CSNFM also promoted a higher cell anchorage and proliferation of human bone marrow mesenchymal stem cells (hMSCs) compared to the free-standing RGO film without the nanoscale fibrous structure. Further, cell viability of hMSCs was comparable to that on the tissue culture plates (TCPs) with a distinctive healthy morphology, indicating that the nanoscale fibrous architecture plays a critically constructive role in supporting cellular activities. In addition, the RGO-CSNFM exhibited excellent electrical conductivity, making them an ideal candidate for conductive cell culture, biosensing, and tissue engineering applications. These findings could provide a new benchmark for preparing well-defined graphene-based nanomaterial configurations and interfaces for biomedical applications.

Highly luminescent hydrogels synthesized by covalent grafting of lanthanide complexes onto PNIPAM via one-pot free radical polymerization

Highly luminescent PNIPAM–Ln(DPA)3 hydrogels have been synthesized by one-pot free radical polymerization in aqueous systems at room temperature. We firstly synthesized a bifunctional chelating ligand named as 4-vinylpyridine-2,6-dicarboxylic acid (4-VDPA), which contains two different moieties: (1) a pyridine-2,6-dicarboxylic acid (DPA) moiety that can sensitize the luminescence of Tb3+ and Eu3+ and (2) a reaction functional group that can be polymerized by free radical initiation. Therefore, the luminescent lanthanide complexes can be grafted onto the hydrogel matrix via one-pot free radical polymerization of [Ln(4-VDPA)3]3−, N-isopropylacrylamide (NIPAM) and N,N′-methylenebis(2-propenamide) (MBA). The results indicated that the final hydrogels possess bright luminescence, long luminescence lifetimes and high quantum efficiency. Moreover, the emission colors of the hydrogels can be tuned from red, reddish orange, orange-yellow, yellow, and green by varying the molar ratio of added Eu3+ to Tb3+.

Construction of pH-responsive and up-conversion luminescent NaYF4:Yb3+/Er3+@SiO2@PMAA nanocomposite for colon targeted drug delivery

Colon-targeted drug delivery system has attracted much interest because it can improve therapeutic efficacy and reduce the side effect in practical clinic. Herein, we constructed a multifunctional drug delivery system with colonic targeting and tracking by up-conversion (UC) luminescence based on core-shell structured NaYF4:Yb3+/Er3+@SiO2@PMAA nanocomposite. The resultant materials exhibited bright UC luminescence, pH-responsive property and excellent biocompatibility. The drug release behaviors in different pH environment were investigated using 5-aminosalicylic acid (5-ASA) as a model drug. The 5-ASA molecules release from NaYF4:Yb3+/Er3+@SiO2@PMAA nanocomposite exhibit a significant pH-responsive colon targeted property, i.e., a little amount of drug release in simulated gastric fluid (SGF, pHu2009=u20091.2) but a large amount of drug release in simulated colonic fluid (SCF, pHu2009=u20097.4) Moreover, the drug release process could be monitored by the change of UC emission intensity. These results implied that the multifunctional nanocomposite is a promising drug carrier for targeted release of 5-ASA in the colon.

pH-responsive poly (acrylic acid)-gated mesoporous silica and its application in oral colon targeted drug delivery for doxorubicin

Oral chemotherapy is the preferred route for cancer treatment because it can improve the efficacy and decrease the side effects. Unfortunately, most anticancer drugs suffered from their poor oral bioavailability. Herein, we construct a novel pH-triggered oral drug delivery system by capping of mesoporous silica SBA-15 with pH-responsive polymer poly (acrylic acid) (PAA) via a facile graft-onto strategy. The experiment results demonstrated that the PAA brushes were anchored on the pore outlets of mesoporous silica SBA-15, which can be acted as the gatekeeper to control the drug molecules transport in and out of the pore channels. The PAA capped mesoporous SBA-15 (PAA/SBA-15) exhibited a high drug loading capacity (785.7mg/g), excellent pH-sensitivity and good biocompatibility. In gastric environment (pH=2.0), the drug doxorubicin (DOX) molecules were encapsulated in the pore channels because the pore outlets were capped with collapsed PAA. In contrast, in colonic environment (pH=7.6), it exhibited a fast release because of the removal of capping. In addition, the water solubility of DOX in colonic environment was enhanced after DOX being loaded into the pores of PAA/SBA-15. This pH-triggered oral drug delivery system has promising applications for treatment of colon cancer and other colon diseases.

Biocompatible, Free-Standing Film Composed of Bacterial Cellulose Nanofibers–Graphene Composite

In recent years, graphene films have been used in a series of wide applications in the biomedical area, because of several advantageous characteristics. Currently, these films are derived from graphene oxide (GO) via chemical or physical reduction methods, which results in a significant decrease in surface hydrophilicity, although the electrical property could be greatly improved, because of the reduction process. Hence, the comprehensive performance of the graphene films showed practical limitations in the biomedical field, because of incompatibility of highly hydrophobic surfaces to support cell adhesion and growth. In this work, we present a novel fabrication of bacterial cellulose nanofibers/reduced graphene oxide (BC-RGO) film, using a bacterial reduction method. Thus-prepared BC-RGO films maintained excellent hydrophilicity, while electrical properties were improved by bacterial reduction of GO films in culture. Human marrow mesenchymal stem cells (hMSCs) cultured on these surfaces showed improved cellular response with higher cell proliferation on the BC-RGO film, compared to free-standing reduced graphene oxide film without the nanoscale fibrous structure. Furthermore, the cellular adhesion and proliferation were even comparable to that on the tissue culture plate, indicating that the bacterial cellulose nanofibers play a critically contructive role in supporting cellular activities. The novel fabrication method greatly enhanced the biochemical activity of the cells on the surface, which could aid in realizing several potential applications of graphene film in biomedical area, such as tissue engineering, bacterial devices, etc.

Water-soluble luminescent hybrid aminoclay grafted with lanthanide complexes synthesized by a Michael-like addition reaction and its gas sensing application in PVP nanofiber

Aminoclay was used as a scaffold for lanthanide complexes and dye molecules for light harvesting applications. However, these syntheses are mainly based on a non-covalent electrostatic attraction between aminoclay and guest molecules. Herein, we develop a strategy to synthesize luminescent aminoclay by a Michael-like addition reaction between an amino-group of aminoclay and a Michael acceptor group. UV absorbance, photoluminescence, and phosphorescence spectra studies confirmed that luminescent lanthanide complexes were covalently grafted onto the amionclay. We found that the hybrid aminoclays (AC-Ln(DPA)n) exhibit favorable luminescent properties coupled with good water-solubility. Furthermore, the luminescent aminoclay can be incorporated into water-soluble polyvinylpyrrolidone (PVP) to obtain a highly luminescent, physically crosslinked nanofiber by electrospinning technology. Interestingly, an exposure of the nanofiber to HCl vapors can cause a significant quenching of Eu3+ luminescence, while a remarkable luminescence enhancement occurred upon exposure of the acid-treated nanofiber to Et3N vapors. Further studies indicated that this reversible luminescence change is due to the dissociation and recovery of Eu3+ complexes by HCl and Et3N vapors. The results present a promising gas sensing application based on developed hybrid luminescent materials.

Facile synthesis of carbon dots with superior sensing ability

Carbon dots (CDs) have various applications in biomedical and environmental field, such as bio-imaging, bio-sensing and heavy metal detection. In this study, a novel class of CDs were synthesized using a one-step hydrothermal method. The fabricated CDs displayed stable photoluminescence, good water solubility, and photo stability. Moreover, the functional groups (carboxylic acid moieties and hydroxyls) on the surface of the obtained CDs enable it with superior sensing ability (e.g., very low detectable concentration for Pb2+: 5xa0nmol/L). With superior detection sensitivity, excellent fluorescent properties and facile fabrication method, the as-obtained CDs can find practical applications as cost-effective and sensitive chemo-sensors in water and food safety field.

A water-soluble fluorescent hybrid material based on aminoclay and its bioimaging application

A water-soluble fluorescent hybrid material has been prepared by functionalization of aminoclay with a fluorescent dye (NDPA). UV-vis absorbance, FT-IR/fluorescent spectroscopy, SEM and TEM techniques were used to investigate its structural, fluorescence and morphological features. The results indicated that the organic fluorescent group can be covalently anchored onto aminoclay through the reaction of the amino-group, and the obtained AC–NDPA exhibited good water solubility and fluorescence properties, coupled with high dispersibility in aqueous solution. Further study found that AC–NDPA had low biotoxicity, and live cell imaging showed that AC–NDPA can be efficiently phagocytized by HeLa cells, bright blue emission can be observed in the cytoplasm and nucleus of HeLa cells by con-focal laser scanning microscopy. We expect that this work could reveal the potential for using the aminoclay based fluorescent material as an effective staining reagent for in vivo bioimaging.