Yajie Xie

An environmentally friendly preparation and characterization of waterborne polyurethane hydrogels by polyvinyl alcohol physical cross-linking to improve water absorption

In this study, waterborne polyurethane hydrogels were successfully synthesized with a waterborne polyurethane solution (WPU) and poly(vinyl alcohol) (PVA), which acted as a cross-linking agent in a freezing–thawing method. The average diameter of WPU, as determined by dynamic light scattering, was around 41.3 nm. The structure and morphology of the polyurethane composite hydrogel were characterized by means of FTIR, SEM and TGA, which confirmed that WPU and PVA formed a homogeneous miscible system through hydrogen bonds. The FTIR analysis showed that with the increasing WPU content, a large number of hydroxyl groups were provided for hydrogen bonding with the carbonyl group of WPU, resulting in strong hydrogen bonding interactions. From SEM, the number of surface pores of the PU/PVA composite hydrogels increased with increasing WPU content. With the increasing WPU content, the tensile strength of the PU/PVA composite hydrogels decreased. 70% PU/PVA prepared gave the best water absorption of 16.33 g g−1 in distilled water. The PU/PVA hydrogels had three stages of water absorption, namely, a fast adsorption phase, a slow adsorption phase and an equilibrium adsorption phase. The waterborne polyurethane hydrogel prepared from an environmentally friendly synthetic method was shown to be a promising new candidate as a wound dressing material.

Preparation of a carboxymethylated bacterial cellulose/polyaniline composite gel membrane and its characterization

Bacterial cellulose (BC) was modified by carboxymethylation (CM) to get carboxymethylation bacterial cellulose (CM-BC) with different degrees of substitution (DS). Then the novel conductive CM-BC/PANI nanocomposite membranes were successfully synthesized in situ by oxidative polymerization of aniline using CM-BC as the template. The influence of carboxymethylation on the structure, morphology, electrical/proton conductivity and mechanical property of the CM-BC/PANI composites has been investigated. The CM-BC/PANI networks display a combination of hybrid electronic/proton conductivity and better mechanical property compared to that of BC/PANI. The electrical conductivity can reach 1.69 × 10−2 S cm−1 when the DS is 0.146 with carboxymethylation for 13 hours. In addition, the proton conductivity of CM-BC/PANI shows an obvious improvement in comparison to that of BC/PANI, which could reach 2.86 × 10−4 S cm−1. The CM-BC/PANI composite membranes exhibit certain flexibility and good mechanical properties with a tensile strength of 0.23 MPa.

A novel microporous oxidized bacterial cellulose/arginine composite and its effect on behavior of fibroblast/endothelial cell

The bacterial cellulose (BC) has been reported widely. Although there are many methods to modify BC, such as the oxidized BC, which is biodegradable and can be used as wound dressing. However, the nanostructure of BC makes it difficult to be oxidized. Importantly, high oxidation degree makes the content of aldehyde high, which make the cell biocompatibility poor. Herein, we fabricated a novel bio-composite based on microporous oxidized BC (MOBC) and in-situ grafted with Arg. The micropores can increase the contact area between BC and oxidizing agent and the reaction between MOBC and Arg, which will enhance the biocompatibility. The roughness and surface energy of MOBC/68.68%Arg are 1.5 and 1.16 times than that of BC respectively. We applied a microfluidic chip to evaluate the cell migration. Comparing with BC, MOBC/Arg promoted proliferation, migration and expression of Collagen-I of fibroblasts and endothelial cells. It prospects the MOBC/Arg can be used as wound dressing.

The gelation process and protein absorption property of injectable SA-CMBC hydrogel used for procoagulant material

Carboxymethylated bacterial cellulose (CMBC) was composited with sodium alginate (SA) to obtain SA-CMBC hydrogel, cross-linked by calcium ion, which was generated from the hydrolyzing of calcium carbonate with the addition of glucono-delta-lactone (GDL). The addition of CMBC could regulate the properties of SA-CMBC hydrogel, such as gelation time, mechanical property, protein absorption and procoagulant property. The addition of CMBC shortened the gelation time, the shortest of which reached to 4.9 min, and increased the mechanical property, the best of which reached to 0.118 MPa. The hydrogel with 25% weight fraction of CMBC showed the best protein absorption property. The procoagulant activity of the SA-CMBC hydrogel was investigated by activated partial thromboplastin time (APTT) and prothrombin time (PT), and hydrogel with 20% weight fraction of CMBC showed the best procoagulant property.

Novel Electronic–Ionic Hybrid Conductive Composites for Multifunctional Flexible Bioelectrode Based on in Situ Synthesis of Poly(dopamine) on Bacterial Cellulose

With the rapid development of the wearable detector and medical devices, flexible biosensing materials have received more and more attention. In this work, a novel flexible and conductive biocompatible composite with electronic and ionic bioconductive ability was demonstrated to fabricate a new flexible bioelectrode used for electrophysiological signal detection. This composite was prepared by the in situ self-polymerization of dopamine on the nanofiber of bacterial cellulose (BC) under the neutral pH condition. By using this method, poly(dopamine) (PDA) could form a uniform and continuous wrapped layer on the BC nanofiber that can prevent the aggregation of PDA caused by rapid polymerization under the conventional alkaline condition. In addition, a fabricated film with a special structure is suitable for the transportation of electrons and ions existing in it. Moreover, the flexible conductive film (FCF) reveals an extremely tensile strength, which is 2 times higher than the pure BC in addition to a high electric conductivity, which reaches a value of 10-3 S/cm with a high PDA content. Furthermore, the result of electrocardiogram signal testing shows that the antibacterial property of the FCF bioelectrode has an excellent stability, which is comparable to or better than the commercially available electrode. The BC/PDA-FCF provides a platform for the creation of flexible conductive biomaterials for wearable response devices.

Effects of graphene on the structure, properties, electro-response behaviors of GO/PAA composite hydrogels and influence of electro-mechanical coupling on BMSC differentiation

Electro-responsive Graphene oxide-poly(acrylic acid) (GO-PAA) nanocomposite hydrogels with different concentrations of GO were successfully fabricated via in situ polymerization. The covalently crosslinked PAA network is intertwined with GO sheets by the bridging of hydrogen-bond interactions thus resulting in an integrated and stable hydrogel network. The swelling, mechanical and conductivity properties of the hydrogel are impacted as a result. The influences of different factors on the electro-response behavior of the hydrogels were deeply explored. Because of electrostatic double layer of the GO, the response properties of hydrogels in different voltage, pH, and ionic strength improved significantly. Meanwhile, with the addition of GO, the response performance of hydrogel in biological applications was greatly expanded. Furthermore, GO-PAA hydrogel shows a good compatibility with bone marrow-derived mesenchymal stem cells (BMSCs). The electro-mechanical coupling of the hydrogel can change the morphology of the adhesive cells, and regulate the cytoskeleton of the cell under the condition of electrical stimulation, which can further promote the differentiation of neural stem cells. This electro-responsive hydrogel could be widely used in many fields of biomedical application such as artificial muscle and tissue engineering scaffold.

In situ synthesis of bacterial cellulose/copper nanoparticles composite membranes with long-term antibacterial property

Abstract Bacterial cellulose (BC), with unique structure and properties, has attracted much attention in the biomedical field, especially in using as wound dressing. However, pure BC lacks the antimicrobial activity, which limits its application in wound healing. To solve this problem, copper nanoparticles (Cu NPs) loaded BC membranes were fabricated by using in situ chemical reduction method. The morphology and chemical composition of the composite membranes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA). The results showed that Cu NPs evenly distributed and anchored in the three-dimensional (3-D) nanofiber network of BC through physical bonding. Traces of Cu2O were observed on the membranes probably because the Cu2+ was incompletely reduced. The Cu NPs loaded BC membranes showed efficient long-term antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) even after immersion in deionized water for up to 90 days. The composite membranes kept sustained release of copper ion, which may contribute to the long-term antibacterial activity. Furthermore, with controlled Cu concentration, BC/Cu membranes did not show obvious cytotoxicity to normal human dermal fibroblasts (NHDF). In all, the present results reveal that BC/Cu membranes with efficient antibacterial activity are promising to be used as wound dressings.

The effects of two biocompatible plasticizers on the performance of dry bacterial cellulose membrane: a comparative study

AbstractBacterial cellulose (BC) has unique properties and is widely applied as wound dressings. Dry BC membranes have better stability and longer storage time, but are poor in gas permeability and water absorption. To solve the problems with dry BC, we prepared two different plasticized dry BC membranes using two biocompatible plasticizers with different molecular weight and hydroxyl content, namely glycerol (G) and polyethylene glycol (PEG). The different effects of the two plasticizers on the structure and performance of dry BC were systematically compared and analyzed. The plasticized dry BC membranes were characterized with Fourier transform infrared spectroscopy, scanning electron microscopy, thermo-gravimetry, etc. The elongation at break for BC/2%G and BC/2%PEG were 8.1 and 12.5 times that of dry BC, respectively. BC/2%G had a water absorption of 4560%, and a water retention rate of 2468%, and those for BC/2%PEG were 4690% and 1972%, respectively. The highly porous structure of the plasticized dry BC membranes effectively enhanced the water vapor transmission rate of the membranes. The different effects of the two plasticizers can be ascribed to the differences in molecule size, hydroxyl content, hydrogen bond interaction, etc. The plasticized dry BC membranes showed excellent resistance to bacteria, which were 99.8% for BC/G and 99.9% for BC/PEG. The performance of the two plasticized dry BC membranes can be tuned to adapt to different applications. Graphical Abstract