3D bioprinting of an electroactive and self-healing polysaccharide hydrogels.

Polysaccharide hydrogels including alginate, agarose, hyaluronic acid, and chitosan have been widely used as scaffolds in 3D bio-printing field. Konjac glucomannan (KGM) exhibits excellent properties of water solubility, biocompatibility, and biodegradability. Herein composite hydrogels were prepared via Schiff-base reaction between the aldehyde group of oxidized konjac glucomannan (OKGM) and the amino group of branched polyethyleneimine (PEI). The OKGM/PEI composite hydrogel displayed self-healing ability and pH sensitivity and showed shear thinning capability, which is suitable for 3D bio-printing technology. Furthermore, the OKGM/PEI electroactive composite hydrogel was obtained by adding carbon nanotubes (CNTs). Then the rheological behavior and morphology of OKGM/PEI electroactive hydrogels were thoroughly characterized. The conductivities of OKGM/PEI electroactive composite hydrogels increased with increasing the content of CNTs. The rheological behavior and 3D bio-printability of OKGM/PEI electroactive hydrogels were also tested. It was found that CNTs can also improve the bio-printability of OKGM/PEI electroactive hydrogels. Thus, the OKGM/PEI electroactive hydrogels could be employed as scaffolds for muscle and cardiac nerve tissue regeneration.

Preparation and Application of Conductive Polyaniline-Coated Thermally Expandable Microspheres.

The thermally expandable microspheres (TEMs) were prepared through suspension polymerization with acrylonitrile (AN), methyl methacrylate (MMA) and methyl acrylate (MA) as the main monomers. Simultaneously, iso-pentane, n-hexane, iso-octane and other low-boiling hydrocarbons were prepared as blowing agents under two conditions, including high-pressure nitrogen and atmospheric conditions. The above physical foaming microspheres have a core-shell structure and excellent foaming effects. A layer of polyaniline (PANI) was deposited on the surface of the prepared TEMs by emulsion polymerization to obtain conductive and heat-expandable microspheres. Afterwards, the foaming ink was prepared by mixing the conductive TEMs and water-based ink. Finally, a conductive three-dimensional picture was obtained by screen-printing technology. This paper specifically focuses on the effects of particle size, morphology and the thermal expansion properties of the microspheres. The present research methods expect to obtain microspheres with a high foaming ratio, uniform particle size and antistatic properties, which may be applied to physical foaming ink.

Redox-responsive theranostic nanoplatforms based on inorganic nanomaterials.

Spurred on by advances in materials chemistry and nanotechnology, scientists have developed many novel nanopreparations for cancer diagnosis and therapy. To treat complex malignant tumors effectively, multifunctional nanomedicines with targeting ability, imaging properties and controlled drug release behavior should be designed and exploited. The therapeutic efficiency of loaded drugs can be dramatically improved using redox-responsive nanoplatforms which can sense the differences in the redox status of tumor tissues and healthy ones. Redox-sensitive nanocarriers can be constructed from both organic and inorganic nanomaterials; however, at present, drug delivery nanovectors progressively lean towards inorganic nanomaterials because of their facile synthesis/modification and their unique physicochemical properties. In this review, we focus specifically on the preparation and application of redox-sensitive nanosystems based on mesoporous silica nanoparticles (MSNs), carbon nanomaterials, magnetic nanoparticles, gold nanomaterials and other inorganic nanomaterials. We discuss relevant examples of redox-sensitive nanosystems in each category. Finally, we discuss current challenges and future strategies from the aspect of material design and practical application.

3D Printing of Aniline Tetramer-Grafted-Polyethylenimine and Pluronic F127 Composites for Electroactive Scaffolds.

Electroactive hydrogel scaffolds are fabricated by the 3D-printing technique using composites of 30% Pluronic F127 and aniline tetramer-grafted-polyethylenimine (AT-PEI) copolymers with various contents from 2.5% to 10%. The synthesized AT-PEI copolymers can self-assemble into nanoparticles with the diameter of ≈50 nm and display excellent electroactivity due to AT conjugation. The copolymers are then homogeneously distributed into 30% Pluronic F127 solution by virtue of the thermosensitivity of F127, denoted as F/AT-PEI composites. Macroscopic photographs of latticed scaffolds elucidate their excellent printability of F/AT-PEI hydrogels for the 3D-printing technique. The conductivities of the printed F/AT-PEI scaffolds are all higher than 2.0 × 10-3 S cm-1 , which are significantly improved compared with that of F127 scaffold with only 0.94 × 10-3 S cm-1 . Thus, the F/AT-PEI scaffolds can be considered as candidates for application in electrical stimulation of tissue regeneration such as repair of muscle and cardiac nerve tissue.

Enhanced conductivity of rGO/Ag NPs composites for electrochemical immunoassay of prostate-specific antigen.

Electrode materials play a vital role in the development of electrochemical immunosensors (EIs), particularly of label-free EIs. In this study, composites containing reduced graphene oxide with silver nanoparticles (rGO/Ag NPs) were synthesized using binary reductants, i.e. hydrazine hydrate and sodium citrate. Due to the fact that graphene oxide (GO) was fully restored to rGO, and rGO stacking was effectively inhibited by insertion of small Ag NPs between the graphene sheets, the electrical conductivity of rGO/Ag NPs composites was significantly improved compared to rGO alone, with an enhancement factor of 346% at 40wt% of rGO. Moreover, the conducting path between rGO and Ag NPs formed because the structural defects in rGO were effectively repaired by decoration with Ag NPs. Subsequently, based on a screen-printed three-electrode system, a label-free EI for detecting prostate-specific antigen (PSA) was constructed using rGO/Ag NPs composites as a support material. The fabricated EIs demonstrated a wide linear response range (1.0-1000ng/ml), low detection limit (0.01ng/ml) and excellent specificity, reproducibility and stability. Thus, the proposed EIs based on rGO/Ag NPs composites can be easily extended for the ultrasensitive detection of different protein biomarkers.

A universal gene carrier platform for treatment of human prostatic carcinoma by p53 transfection.

Our previous work showed that a charge-reversal layer-by-layer nanosystem, PEI/PAH-Cit/AuNP-CS, effectively facilitates cellular uptake of siRNA and enhances the silencing efficacy of MDR1 siRNA. Here, the plasmid loading capacity of this vehicle was examined using EGFP-N1, and the plasmid release profile was determined in response to pH changes. The cytotoxicity of the EGFP-N1/PEI/PAH-Cit/AuNP-CS complex against HeLa and 293T cells was almost negligible. PEI/PAH-Cit/AuNP-CS efficaciously delivered the plasmids EGFP-N1 (encoding green fluorescent protein) and pGL3.0 (encoding luciferase) into 293T and HeLa cells, thus verifying the universality of PEI/PAH-Cit/AuNP-CS as a gene carrier. The results of an inverted fluorescence microscopy, flow cytometry (FCM) and western blotting methods demonstrated that PC-3 prostate cancer cells treated with EGFP-p53/PEI/PAH-Cit/AuNP-CS expressed higher levels of GFP than cells treated with EGFP-p53/PEI. Furthermore, PC-3 cells treated with EGFP-p53/PEI/PAH-Cit/AuNP-CS showed reduced cellular viability and increased nuclear fragmentation, consistent with elevated p53 expression. Propidium iodide (PI) flow cytometric assays were conducted to demonstrate that EGFP-p53/PEI/PAH-Cit/AuNP-CS elevated the level of apoptosis in PC-3 cells. Western blotting and caspase activation studies revealed that EGFP-p53/PEI/PAH-Cit/AuNP-CS complexes may induce PC-3 apoptosis via the mitochondria-mediated signaling pathway by up-regulation of Bax, down-regulation of Bcl-2, and activation of caspase-3.

[Preparation and study on the spectra of conductive nano-silver film].

The preparation and study on the spectra of conductive nano-silver film were done under mild conditions. The silver citrate emulsion coating on the surface of PET was reduced by ascorbic acid (Vc) aqueous solution to prepare a silver film. The morphology, crystal structure, surface roughness and conductivity of the silver film were measured by FTIR, UV-Vis spectrum, X-ray diffraction (XRD), scanning electron microscope, scanning probe microscope system and so on. It was found that the silver citrate emumsion has a homogenous particle distribution from 60 nm-150 nm. The UV-Vis spectrum of the silver film shows a peak at 430 nm, and the silver thin film was considered to have a typical nano-scale structure. By the comparison of the XRD patterns of the films treated and untreated with water, it was concluded that the further deoxidization of silver citrate could be accelerated by water. The crystal structure of the silver film was improved and the surface resistance of the silver film was decreased greatly. The effect of ethanol on the decrease in the resistance of the silver film is much less than that of water.

[Charge control and IR analysis of amine on diarylide yellow pigment PY14].

To study the reaction of amine with dairylide yellow pigment (PY14) used in electrophoretic display, especially the reaction mechanism between polyisobutylene imide (PIBI) and PY14, some amines were selected to react with PY14. At the same time, tetraethylene pentamine was treated with HCl. The zeta potential and IR of the above products were tested. Based on the zeta potential and IR frequency, the charge control intensities of different amines on PY14 were compared, and it is confirmed that the reaction of PY14 with amines is Lewis reaction, the charge control of secondary and primary amines with less steric obstacle is stronger. The PY14 zeta potential value reverse is due to the adsorption of bigger reverse ion.