Dual-Physical Cross-Linked Tough and Photoluminescent Hydrogels with Good Biocompatibility and Antibacterial Activity.

Development of novel photoluminescent hydrogels with toughness, biocompatibility, and antibiosis is important for the applications in biomedical field. Herein, novel tough photoluminescent lanthanide (Ln)-alginate/poly(vinyl alcohol) (PVA) hydrogels with the properties of biocompatibility and antibiosis have been facilely synthesized by introducing hydrogen bonds and coordination bonds into the interpenetrating networks of Na-alginate and PVA, via approaches of frozen-thawing and ion-exchanging. The resultant hydrogels exhibit high mechanical strength (0.6 MPa tensile strength, 5.0 tensile strain, 6.0 MPa compressive strength, and 900 kJ m-3 energy dissipation under 400% stretch), good photoluminescence as well as biocompatibility and antibacterial activity. The design strategy provides a new avenue for the fabrication of multifunctional photoluminescent hydrogels based on biocompatible polymers.

Exceptionally tough and notch-insensitive magnetic hydrogels.

Most existing magnetic hydrogels are weak and brittle. The development of strong and tough magnetic hydrogels would extend their applications into uncultivated areas, such as in actuators for soft machines and guided catheters for magnetic navigation systems, which is still a big challenge. Here a facile and versatile approach to fabricating highly stretchable, exceptionally tough and notch-insensitive magnetic hydrogels, Fe(3)O(4)@Fe-alginate/polyacrylamide (PAAm), is developed, by dispersing alginate-coated Fe(3)O(4) nanoparticles into the interpenetrating polymer networks of alginate and PAAm, with hybrid physical and chemical crosslinks. A cantilever bending beam actuator as well as a proof-of-concept magnetically guided hydrogel catheter is demonstrated. The method proposed in this work can be integrated into other strong and tough magnetic hydrogels for the development of novel hydrogel nanocomposites with both desirable functionality and superior mechanical properties.

Tough photoluminescent hydrogels doped with lanthanide.

Photoluminescent hydrogels have emerged as novel soft materials with potential applications in many fields. Although many photoluminescent hydrogels have been fabricated, their scope of usage has been severely limited by their poor mechanical performance. Here, a facile strategy is reported for preparing lanthanide (Ln)-alginate/polyacrylamide (PAAm) hydrogels with both high toughness and photoluminescence, which has been achieved by doping Ln(3+) ions (Ln = Eu, Tb, Eu/Tb) into alginate/PAAm hydrogel networks, where Ln(3+) ions serve as both photoluminescent emitters and physical cross-linkers. The resulting hydrogels exhibit versatile advantages including excellent mechanical properties (∼ MPa strength, ≈ 20 tensile strains, ≈ 10(4) kJ m(-3) energy dissipation), good photoluminescent performance, tunable emission color, excellent processability, and cytocompatibility. The developed tough photoluminescent hydrogels hold great promises for expanding the usage scope of hydrogels.

Self-healing gels based on constitutional dynamic chemistry and their potential applications.

As representative soft materials with widespread applications, gels with various functions have been developed. However, traditional gels are vulnerable to stress-induced formation of cracks. The propagation of these cracks may affect the integrity of network structures of gels, resulting in the loss of functionality and limiting the service life of the gels. To address this challenge, self-healing gels that can restore their functionalities and structures after damage have been developed as "smart" soft materials. In this paper, we present an overview of the current strategies for synthesizing self-healing gels based on the concept of constitutional dynamic chemistry, which involves molecular structures capable of establishing dynamic networks based upon physical interactions or chemical reactions. The characterization methods of self-healing gels and the key factors that affect self-healing properties are analyzed. We also illustrate the emerging applications of self-healing gels, with emphasis on their usage in industry (coatings, sealants) and biomedicine (tissue adhesives, agents for drug or cell delivery). We conclude with a perspective on challenges facing the field, along with prospects for future development.

Dextran-based self-healing hydrogels formed by reversible diels-alder reaction under physiological conditions.

A dextran-based self-healing hydrogel is prepared by reversible Diels-Alder reaction under physiological conditions. Cytocompatible fulvene-modified dextran as main polymer chains and dichloromaleic-acid-modified poly(ethylene glycol) as cross-linkers are used. Both macro- and microscopic observation as well as the rheological recovery test confirm the self-healing property of the dextran-l-poly(ethylene glycol) hydrogels ("l" means "linked-by"). In addition, scanning electrochemical microscopy is used to qualitatively and quantitatively in situ track the self-healing process of the hydrogel for the first time. It is found that the longitudinal depth of scratch on hydrogel surface almost completely healed at 37 °C after 7 h. This work represents a facile approach for fabrication of polysaccharide self-healing hydrogel, which can be potentially used in several biomedical fields.

Biocompatible Photoluminescent Silk Fibers with Stability and Durability.

Exploring photoluminescent silk fibers, possessing biocompatibility as well as stable and durable fluorescent properties, is a requirement for the development of novel photoluminescent biomaterials. Herein, we fabricate photoluminescent silk fibers, TPCA@SF, via modifying an organic fluorescent molecule (5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid, TPCA) onto silk fibers, along with using quaternary ammonium salt didodecyldimethylammonium bromide (DDAB) as a color-fixing agent. The hydrogen bonds and electrostatic association among silk fibers, TPCA and DDAB, ensure the stable modification. The facile and green fabrication process is achieved in water under mild conditions without using any toxic substances. The TPCA@SF manifests the combining features of high quantum yield, fluorescence water-fastness, antiphotobleaching, good mechanical property, and biocompatibility. The strategy holds great potential for exploring various biocompatible photoluminescent substances with stability and durability.

Carbon dots with high fluorescence quantum yield: the fluorescence originates from organic fluorophores.

In this contribution, we have shown that the organic fluorophores, 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA) and 5-oxo-3,5-dihydro-2H-thiazolo [3,2-a] pyridine-7-carboxylic acid (TPCA), are the main ingredients and fluorescence origins of N,S-CDs via systematic analyses. It inspires us to deeply analyze and understand the fluorescence origins of carbon dots with high fluorescence quantum yields, which will expand their applications.

Tough Al-alginate/poly(N-isopropylacrylamide) hydrogel with tunable LCST for soft robotics.

Tough Al-alginate/poly(N-isopropylacrylamide) (PNIPAM) hydrogel has been synthesized by introducing an interpenetrating network with hybrid physically cross-linked alginate and chemically cross-linked PNIPAM. Varying the concentration of AlCl3 regulates the mechanical properties of the tough hydrogel and tunes its lower critical solution temperature (LCST) as well. The tough Al-alginate/PNIPAM exhibits 6.3 ± 0.3 MPa of compressive stress and 9.95 of uniaxial stretch. Tunability of LCST is also achieved in a wide range within 22.5-32 °C. A bending beam actuator and a four-arm gripper made of bilayer (Na-alginate/PNIPAM)/(Al-alginate/PNIPAM) hydrogel as prototype of all-hydrogel soft robotics are demonstrated. A finite element (FE) simulation model is developed to simulate the deformation of the soft robotics. The FE simulation not only reproduces the deformation process of performed experiments but also predicts more complicated devices that can be explored in the future. This work broadens the application of temperature-responsive PNIPAM-based hydrogels.

Dextran-based hydrogel formed by thiol-Michael addition reaction for 3D cell encapsulation.

Cell encapsulation in three-dimensional (3D) hydrogels can mimic native cell microenvironment and plays a major role in cell-based transplantation therapies. In this contribution, a novel in situ-forming hydrogel, Dex-l-DTT hydrogel ("l" means "linked-by"), by cross-linking glycidyl methacrylate derivatized dextran (Dex-GMA) and dithiothreitol (DTT) under physiological conditions, has been developed using thiol-Michael addition reaction. The mechanical properties, gelation process and degree of swelling of the hydrogel can be easily adjusted by changing the pH of phosphate buffer saline. The 3D cell encapsulation ability is demonstrated by encapsulating rat bone marrow mesenchymal stem cells (BMSCs) and NIH/3T3 fibroblasts into the in situ-forming hydrogel with maintained high viability. The BMSCs also maintain their differentiation potential after encapsulation. These results demonstrate that the Dex-l-DTT hydrogel holds great potential for biomedical field.

Quantitative Assessment of the Association between Genetic Variants in MicroRNAs and Colorectal Cancer Risk.

BACKGROUND: The associations between polymorphisms in microRNAs and the susceptibility of colorectal cancer (CRC) were inconsistent in previous studies. This study aims to quantify the strength of the correlation between the four common polymorphisms among microRNAs (hsa-mir-146a rs2910164, hsa-mir-149 rs2292832, hsa-mir-196a2 rs11614913, and hsa-mir-499 rs3746444) and CRC risk. METHODS: We searched PubMed, Web of Knowledge, and CNKI to find relevant studies. The combined odds ratio (OR) with 95% confidence interval (95% CI) was used to estimate the strength of the association in a fixed or random effect model. RESULTS: 15 studies involving 5,486 CRC patients and 7,184 controls were included. Meta-analyses showed that rs3746444 had association with CRC risk in Caucasians (OR = 0.57, 95% CI = 0.34-0.95). In the subgroup analysis, we found significant associations between rs2910164 and CRC in hospital based studies (OR = 1.24, 95% CI = 1.03-1.49). rs2292832 may be a high risk factor of CRC in population based studied (OR = 1.18, 95% CI = 1.08-1.38). CONCLUSION: This meta-analysis showed that rs2910164 and rs2292832 may increase the risk of CRC. However, rs11614913 polymorphism may reduce the risk of CRC. rs3746444 may have a decreased risk to CRC in Caucasians.

Highly stretchable and transparent ionogels as nonvolatile conductors for dielectric elastomer transducers.

Large deformation of soft materials is harnessed to provide functions in the nascent field of soft machines. This paper describes a new class of systems enabled by highly stretchable, transparent, stable ionogels. We synthesize an ionogel by polymerizing acrylic acid in ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim][EtSO4]). The ionogel exhibits desired attributes of adequate conductivity (0.22 S m(-1)), low elastic modulus (∼3 kPa), large rupturing stretch (∼4.6), and negligible hysteresis and degradation after cyclic stretches of large amplitude. Using the ionogel and a dielectric elastomer, we fabricate electromechanical transducers that achieve a voltage-induced areal strain of 140%. The ionogel is somewhat hygroscopic, but the transducers remain stable after a million cycles of excitation in a dry oven and in air. The transparency of the ionogels enable the transducers with conductors placed in the path of light, and the nonvolatility of the ionogels enable the transducers to be used in open air.

Strengthening alginate/polyacrylamide hydrogels using various multivalent cations.

We successfully synthesized a family of alginate/polyacrylamide hydrogels using various multivalent cations. These hydrogels exhibit exceptional mechanical properties. In particular, we discovered that the hydrogels cross-linked by trivalent cations are much stronger than those cross-linked by divalent cations. We demonstrate stretchability and toughness of the hydrogels by inflating a hydrogel sheet into a large balloon, and the elasticity by using a hydrogel block as a vibration isolator in a forced vibration test. The excellent mechanical properties of these hydrogels may open up applications for hydrogels.