[en] The surface of polytetrafluoroethylene (PTFE)-fiberglass composite film was modified with polydopamine (PDA) in order to improve hydrophilic properties and hence to expand its perspective usage for biomedical and blood-contacting applications. Scanning electron microscopy, atomic force microscopy, energy dispersive spectrometer and fourier transform infrared spectra were employed to analyse the surface morphology and the chemical structures of the modified PTFE-fiberglass composite films. Hydrophilic property of PTFE-fiberglass composite films was investigated by using water contact angle measurement. The effect of treatment time on the surface morphology and hydrophilicity of PTFE-fiberglass composite films was investigated. The results showed that a dense layer of PDA was formed on PTFE-fiberglass composite films, the water contact angle decreased gradually with the increase in modification time. Moreover, the fastness of PDA layers deposited on the PTFE-fiberglass composite films was studied by using UV/VIS/NIR spectrometer. It was revealed that the PDA layer was stable in distilled water, 0.1 M hydrochloric acid solution and alcohol, but had a poor resistance to 0.1 M sodium hydroxide solution.

[en] Fabric surface coating is deemed as the major route to fabricate functional fabrics, and interface stability is a critical factor affecting the performance of fabric. Here, electrophoretic deposition (EPD) is employed for fast and facile modification of hydrophobic polyamide fabric with graphene oxide (GO) nanosheets embedded in polymeric networks. For better grafting, polyethyleneimine is utilized to modify the surface of the fabric substrate, endowing more polar groups and resulting in reasonable interface properties of graphene oxide and fabric substrate. GO nanosheets are uniformly deposited on modified fabric via EPD method and then reduced by green hot-press processing. The modified fabric shows excellent electrical conductivity (electrical conductivity > 3.3 S/m), thermal conductivity (0.521 W/m·K), and UV protection performance (UPF > 500, UVA < 0.2%). Meanwhile, the contact angle test of fabric reveals that the addition of graphene significantly improved the hydrophobicity of the fabric.

[en] To obtain magnetorheological elastomers (MREs) with improved mechanical properties and exhibiting an enhanced magnetorheological (MR) effect, bio-inspired dopamine modification has been used to improve the functionality at the surface of carbonyl iron (CI) particles. Various techniques including x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to confirm that a polydopamine (PDA) layer of about 27.5 nm had been successfully deposited on the surface of the carbonyl iron particles prior to their inclusion in the MRE composites. The magnetic properties of PDA modified CI particles were shown to be almost the same as those for untreated CI particles. With the introduction of a PDA layer to the surfaces of the particles, both the tensile strength and the elongation at break of the MREs were improved. Furthermore, the MRE composites filled with PDA-coated CI particles exhibited lower zero-field storage moduli but higher magnetic field induced storage moduli when magnetization saturation was reached. The absolute and relative MR effect for the MREs reached 0.68 ± 0.002 MPa and 294% respectively, which were higher than those of MREs with pristine CI particles whose absolute and relative MR effect were 0.57 ± 0.02 MPa and 187% respectively. The findings of this work provide insights into enhanced fabrication of MREs with both improved mechanical properties and magneto-induced performance. (paper)

[en] Fiber constructed yarns are the elementary building blocks for the generation of implantable biotextiles, and there are always needs for designing and developing new types of yarns to improve the properties of biotextile implants. In the present study, we aim to develop novel nanofiber yarns (NYs) by combining nanostructure that more closely mimic the extracellular matrix fibrils of native tissues with biodegradability, strong mechanical properties and great textile processibility. A novel electrospinning system which integrates yarn formation with hot drawing process was developed to fabricate poly(L-lactic acid) (PLLA) NYs. Compared to the PLLA NYs without hot drawing, the thermally drawn PLLA NYs presented superbly-orientated fibrous structure and notably enhanced crystallinity. Importantly, they possessed admirable mechanical performances, which matched and even exceeded the commercial PLLA microfiber yarns (MYs). The thermally drawn PLLA NYs were also demonstrated to notably promote the adhesion, alignment, proliferation, and tenogenic differentiation of human adipose derived mesenchymal stem cells (hADMSCs) compared to the PLLA NYs without hot drawing. The thermally drawn PLLA NYs were further processed into various nanofibrous tissue scaffolds with defined structures and adjustable mechanical and biological properties using textile braiding and weaving technologies, demonstrating the feasibility and versatility of thermally drawn PLLA NYs for textile-forming utilization. The hADMSCs cultured on PLLA NY-based textiles presented enhanced attachment and proliferation capacities than those cultured on PLLA MY-based textiles. This work presents a facile technique to manufacture high performance PLLA NYs, which opens up opportunities to generate advanced nanostructured biotextiles for surgical implant applications. (paper)

[en] Compared with traditional methods for preparing dielectric elastomer (DE) films, electrohydrodynamic (EHD) 3D printing displays many advantages, notably full automation, computer control and flexible design. It also confers high printing resolution, high preparation efficiency with minimal probability of nozzle clogging. In this article, EHD 3D printing was employed to fabricate silicone rubber (SR) based DE films. In order to increase their dielectric constant, high dielectric copper phthalocyanine (CuPc) particles were added into the SR ink. Optimal printing conditions were determined by analyzing the effects of printing voltage and ink properties on the formation of liquid cone and the printed line width. The SR/CuPc composite film with 3 wt% CuPc particles (SR/CuPc-3) exhibits a high dielectric constant of 5.52, with a large actuated area strain of 23.7% under an electric field of 39.4 V μm⁻¹. Furthermore, under 100 cycles of electric field loading, SR/CuPc-3 demonstrate excellent electromechanical stability, indicating that EHD 3D printing holds a considerable potential for fabricating high-performance DE films in an efficacious manner. (paper)

[en] Highlights: • Design and development of PPDO/SF wavy nanofibrous scaffolds (WNSs). • PPDO/SF WNSs resembled the fibril scale and wavy ultra-structure of native tendon ECM. • PPDO/SF WNSs presented nonlinear mechanical properties, better mimicking the native tendon mechanics. • PPDO/SF WNSs promoted the cell adhesion, proliferation, and phenotypic maintenance of human tenocytes. • A combination of growth factor induction and mechanical stimulation enhanced the tenogenic differentiation of hADMSCs on the PPDO/SF WNSs. The development of tendon-biomimetic nanofibrous scaffolds with mesenchymal stem cells may represent a promising strategy to improve the unsatisfactory outcomes of traditional treatments in tendon repair. In the present study, the nanofibrous scaffolds comprised of poly(p-dioxanone) (PPDO) and silk fibroin (SF) composites were fabricated by using electrospinning technique and subsequent thermal ethanol treatment. The PPDO/SF composite scaffolds presented parallel fiber arrangement with crimped features and nonlinear mechanical properties, which mimic the structure-function relationship of native tendon tissue mechanics. We demonstrated that the fiber crimp degree and mechanical properties of as-prepared PPDO/SF wavy nanofibrous scaffolds (WNSs) could be tunable by adjusting the mass ratio of PPDO/SF. The biological tests revealed that the addition of SF obviously promoted the cell adhesion, proliferation, and phenotypic maintenance of human tenocytes on the WNSs. A preliminary study on the subcutaneous implantation showed that the PPDO/SF WNSs notably decreased the inflammatory response compared with pure PPDO WNSs. More importantly, a combination of growth factor induction and mechanical stimulation was found to notably enhance the tenogenic differentiation of human adipose derived mesenchymal stem cells on the PPDO/SF WNSs by upregulating the expressions of tendon-associated protein and gene markers. Overall, this study demonstrated that our PPDO/SF WNSs could provide a beneficial microenvironment for various cell activities, making them an attractive candidate for tendon tissue engineering research.

[en] In this work, photosensitive alginate and cellulose-based hydrogels with interpenetrating polymer networks were successfully prepared from alginate, TEMPO-oxidized cellulose nanofibers (TEMPO-CNFs) and polyacrylamide, crosslinked by both Fe³⁺ and N,N′-methylenebis-acrylamide. The obtained hydrogels showed a clear relationship between the mechanical properties and the content of the TEMPO-CNFs. The results indicated that the mechanical properties of crosslinked hydrogels were enhanced with the mass ratio of TEMPO-CNFs and alginate increased from 1/2 to 2. Moreover, the crosslinked ionic alginate and cellulose-based hydrogels with various TEMPO-CNFs contents exhibited an interconnected porous morphology with an average pore size of ca. 130 µm, and demonstrated an increased cumulative release amount of BSA drugs under the ultraviolet irradiation. This study demonstrated that the as-prepared photoresponsive hydrogels would have a potential application as local drug release systems for wound dressings.