Reprocessable and Multiple Shape Memory Thermosets with Reconfigurability.

Multiple shape memory thermosets for various engineering applications have been quickly developed in recent years, mainly due to their stable thermomechanical performance, environmental stability, excellent chemical, solvent resistance, etc. However, these thermosets are inherently non-recyclable due to their chemically crosslinked properties, and it is difficult to make the permanent shapes of these thermosets sophisticated and geometrically complex, which significantly restricts a great variety of engineering applications in the industry and technology fields, mainly due to the economic inefficiency and environmental impact. Here, a thermoset with recyclability, multiple shape memory effect (multi-SME), and permanent shape reconfiguration is reported. After recycling, it also exhibits excellent mechanical properties without sacrificing the excellent multi-SME, combined elasticity (shape memory), and solid state plasticity, which can be easily scaled up and generalized to a variety of dynamic covalent networks.

Reconfigurable and Reprocessable Thermoset Shape Memory Polymer with Synergetic Triple Dynamic Covalent Bonds.

Degradable shape memory polymers (SMPs), especially for polyurethane-based SMPs, have shown great potential for biomedical applications. How to reasonably fabricate SMPs with the ideal combination of degradability, shape reconfigurability, and reprocessability is a critical issue and remains a challenge for medical disposable materials. Herein, a shape memory poly(urethane-urea) with synergetic triple dynamic covalent bonds is reported via embedding polycaprolactone unit into poly(urethane-urea) with the hindered urea dynamic bond. The single polymer network is biodegradable, thermadapt, and reprocessable, without sacrificing the outstanding shape memory performance. Such a shape memory network with plasticity and reprocessability is expected to have significant and positive impact on the medical device industry.

Employment of Molecularly Imprinted Polymers to High-Throughput Screen nNOS-PSD-95 Interruptions: Structure and Dynamics Investigations on Monomer-Template Complexation.

Molecularly imprinted polymers (MIPs) are employed to screen nNOS-PSD-95 (neuronal nitric oxide synthase post-synaptic density protein-95) interruptions. 5-(3,5-Dichloro-2-hydroxybenzylamino)-2-hydroxybenzoic acid (ZL006; a potential drug candidate for the treatment of stroke, depression, and pain) is employed as a template. Four kinds of functional monomers (2-VP: 2-vinylpyridine; 4-VP: 4-vinylpyridine; MMA: methyl methacrylate; and MAAM: methacrylamide) are designed, and their complexation with ZL006 in various solvents (methanol, acetonitrile, toluene, chloroform) is investigated by molecular dynamics simulations and quantum mechanics calculations. Both 4-VP and MAAM have stronger interactions with ZL006 than those of 2-VP and MMA. The appropriate ratio of monomer to template is 3:1. Intermolecular hydrogen bonds play a dominant role in monomer-template complexation. Ideal solvents are toluene and chloroform, and the solvation effect on monomer-template complexation is revealed. Both molecular modeling and adsorption experiments demonstrate that as-synthesized ZL006-MIP with 4-VP as a monomer has better selectivity than that employing MAAM to screen for nNOS-PSD-95 interruptions.

Wireless Sensor System Based on Organohydrogel Ionic Skin for Physiological Activity Monitoring.

Supermolecular hydrogel ionic skin (i-skin) linked with smartphones has attracted widespread attention in physiological activity detection due to its good stability in complex scenarios. However, the low ionic conductivity, inferior mechanical properties, poor contact adhesion, and insufficient freeze resistance of most used hydrogels limit their practical application in flexible electronics. Herein, a novel multifunctional poly(vinyl alcohol)-based conductive organohydrogel (PCEL5.0%) with a supermolecular structure was constructed by innovatively employing sodium carboxymethyl cellulose (CMC-Na) as reinforcement material, ethylene glycol as antifreeze, and lithium chloride as a water retaining agent. Thanks to the synergistic effect of these components, the PCEL5.0% organohydrogel shows excellent performance in terms of ionic conductivity (1.61 S m-1), mechanical properties (tensile strength of 70.38 kPa and elongation at break of 537.84%), interfacial adhesion (1.06 kPa to pig skin), frost resistance (-50.4 °C), water retention (67.1% at 22% relative humidity), and remoldability. The resultant PCEL5.0%-based i-skin delivers satisfactory sensitivity (GF = 1.38) with fast response (348 ms) and high precision under different deformations and low temperature (-25 °C). Significantly, the wireless sensor system based on the PCEL5.0% organohydrogel i-skin can transmit signals from physiological activities and sign language to a smartphone by Bluetooth technology and dynamically displays the status of these movements. The organohydrogel i-skin shows great potential in diverse fields of physiological activity detection, human-computer interaction, and rehabilitation medicine.

Thermadapt Shape Memory Polymers Enabling Spatially Regulated Plasticity.

Converting planar polymer films into sophisticated 3D structures with a facile and effective method is highly challenging yet desirable for device applications in the real world. Dynamic covalent polymer networks enable permanent shape transformations from 2D sheets to 3D structures, but either sophisticated molecular design or a complex fabrication method is required. Here, we report a shape memory polymer cross-linked by ester bonds, which can be activated upon heating after photoexposure to release the catalyst for the transesterification. The region that is activated via the bond exchange can be patterned due to the spatial-temporal selectivity of the photoexposure. Accordingly, the material presents a localized heterogeneity in stress relaxation upon stretching. The exposed and the unexposed regions show respectively plastic deformation and elastic recovery after removal of the external force, which finally make the 2D sheet transform into a 3D structure. The decoupling of the activated region (photoexposure) and activated condition (heating) enables facile chemical design and fabrication for 2D-to-3D shape morphing.

Reversal of pancreatic desmoplasia by re-educating stellate cells with a tumour microenvironment-activated nanosystem.

Pancreatic ductal adenocarcinoma is characterised by a dense desmoplastic stroma composed of stromal cells and extracellular matrix (ECM). This barrier severely impairs drug delivery and penetration. Activated pancreatic stellate cells (PSCs) play a key role in establishing this unique pathological obstacle, but also offer a potential target for anti-tumour therapy. Here, we construct a tumour microenvironment-responsive nanosystem, based on PEGylated polyethylenimine-coated gold nanoparticles, and utilise it to co-deliver all-trans retinoic acid (ATRA, an inducer of PSC quiescence) and siRNA targeting heat shock protein 47 (HSP47, a collagen-specific molecular chaperone) to re-educate PSCs. The nanosystem simultaneously induces PSC quiescence and inhibits ECM hyperplasia, thereby promoting drug delivery to pancreatic tumours and significantly enhancing the anti-tumour efficacy of chemotherapeutics. Our combination strategy to restore homoeostatic stromal function by targeting activated PSCs represents a promising approach to improving the efficacy of chemotherapy and other therapeutic modalities in a wide range of stroma-rich tumours.

Isolation and identification of bovine nasopharyngeal mucosal epithelial cells and establishment of cell models of acute infection by foot-and-mouth disease virus.

Foot-and-mouth disease (FMD) commonly occurs via the respiratory tract, and bovine nasopharyngeal mucosal epithelial cells are the primary infection cells in cattle. The aim of the present study was to isolate and culture epithelial cells from the bovine nasopharyngeal mucosa in vitro using a mechanical separation method. The cells were expanded, established in continuous cell culture, and used for immunofluorescence cytochemistry and establishment of infection models. We detected pan-cytokeratin markers of bovine nasopharyngeal mucosal epithelial cells by immunofluorescence. Bovine nasopharyngeal mucosal epithelial cells were then infected with foot-and-mouth disease virus (FMDV) serum type O. RT-PCR demonstrated the successful establishment of acute FMDV infection in the cell models. This infection model provides the basis for clarification of the interaction between FMDV and host bovine nasopharyngeal mucosal epithelial cells in vitro.

Precision design of nanomedicines to restore gemcitabine chemosensitivity for personalized pancreatic ductal adenocarcinoma treatment.

Low chemosensitivity considerably restricts the therapeutic efficacy of gemcitabine (GEM) in pancreatic cancer treatment. Using immunohistochemical evaluation, we investigated that decreased expression of human equilibrative nucleoside transporter-1 (hENT1, which is the major GEM transporter across cell membranes) and increased expression of ribonucleotide reductase subunit 2 (RRM2, which decreases the cytotoxicity of GEM) was associated with low GEM chemosensitivity. To solve these problems, we employed a nanomedicine-based formulation of cationic liposomes for co-delivery of GEM along with siRNA targeting RRM2. Due to the specific endocytic uptake mechanism of nanocarriers and gene-silencing effect of RRM2 siRNA, this nanomedicine formulation significantly increased GEM chemosensitivity in tumor models of genetically engineered Panc1 cells with low hENT1 or high RRM2 expression. Moreover, in a series of patient-derived cancer cells, we demonstrated that the therapeutic benefits of the nanomedicine formulations were associated with the expression levels of hENT1 and RRM2. In summary, we found that the essential factors of GEM chemosensitivity were the expression levels of hENT1 and RRM2, and synthesized nanoformulations can overcome these problems. This unique design of nanomedicine not only provides a universal platform to enhance chemosensitivity but also contributes to the precision design and personalized treatment in nanomedicine.