Versatile Preparation of Nonspherical Multiple Hydrogel Core PAM/PEG Emulsions and Hierarchical Hydrogel Microarchitectures

The preparation of nonspherical materials composed of separated multicomponents by droplet‐based microfluidics remains a challenge. Based on polymerization‐induced phase separation and droplet coalescence in microfluidics, we prepared emulsions of variously shaped PAM/PEG core/shell droplets and hydrogels composed of two separated components, which show flexible and transformable hierarchical structures and microarchitectures. We find that AM/PEG aqueous droplets form a core/shell structure after polymerization resulting from phase separation. Thus multicore/shell droplets are easily produced by coalescence of core/shell structures. By changing the polymerization temperature and the flow rate, the morphology of the multicore droplets and the hydrogel can be easily adjusted. The hydrogels exhibit apparent anisotropy and different protein release rates depending on their structures. The preparation technique is simple and versatile and the resulting hydrogels have potential applications in many fields.     

A Novel Gelatin–Carbon Nanotubes Hybrid Hydrogel

This letter focuses on the first result of the preparation and the swelling behavior of a novel hybrid gelatin hydrogel with carbon nanotubes. A novel hybrid gelatin hydrogel with carbon nanotubes was synthesized by a physical mixing method. The structure of the novel hydrogel obtained was characterized by SEM. Besides, the swelling behavior of the synthesized hydrogel was measured at two different temperatures. The results indicate that carbon nanotubes added could maintain the stability of the hybrid hydrogel without cross‐linking at 37 °C. This suggests that the hybrid gelatin hydrogel with carbon nanotubes could be used in biomedical field. Besides, its application in protein separation is discussed.

SEM image of the gelatin‐MWNTs hybrid gel at 10 000 × magnification.     

Investigation of Metal Ion Removal Selectivity Properties of the Modified Polyacrylamide Hydrogels Prepared by Transamidation and Hofmann Reactions

Modified crosslinked polyacrylamides having different functional groups prepared by transamidation reaction in aqueous and non‐aqueous medium and by Hofmann reaction were used as chelating agents for removal of Cu(II), Cd(II) and Pb(II) ions from aqueous solutions at different pH values. Under non‐competitive conditions, polymers adsorbed different amounts of metal ions, depending on their functional groups and swelling abilities. The metal ion adsorption capacities of polymers changed between 0.11–1.71 mmol/g polymer. Under competitive conditions, while the polymers having mainly secondary amine groups were highly selective for Cu(II) ions (99.4%), those having mainly secondary amide and carboxylate groups have shown high selectivity towards Pb(II) ions (99.5%). The selectivity towards Cu(II) ion decreased and Pb(II) ion selectivity increased by the decrease of the pH of the solutions. The high initial adsorption rate (<10 min) suggests that the adsorption occurs mainly on the polymer surface. A regeneration procedure by treatment with dilute HCl solution showed that the modified polymers could be used several times without loss of their adsorption capacities.     

A Novel Highly Resilient Nanocomposite Hydrogel with Low Hysteresis and Ultrahigh Elongation

Summary: A series of high clay content Laponite XLS/polyacrylamide (PAAm) nanocomposite hydrogels (S‐M gels) with excellent resilience, low elastic hysteresis, and ultrahigh elongation, have been successfully synthesized. Based on our results, it is concluded that the mechanical properties of nanocomposite hydrogels probably depend to a great extent on the hydrophilicity and flexibility of the macromolecules. Moreover, it is found that the transparency during the in‐situ polymerization of S‐M gels does not change, which is quite different from clay/poly(N‐isopropylacrylamide) nanocomposite hydrogels.

Formation of nanocomposite hydrogels using Clay‐S by in‐situ polymerization.     

Novel Phosphorescent Hydrogels Based on an IrIII Metal Complex

Novel phosphorescent hydrogels have been explored by immobilizing an Ir^III metal complex into the matrices of hydrogels. FTIR spectra demonstrate that the Ir^III–PNaAMPS hydrogel is achieved by irreversible incorporation of positively charged [Ir(ppy)₂(dmbpy)]Cl (ppy = 2‐phenylpyrine, dmbpy = 4,4′‐dimethyl‐2,2′‐bipyridine) into negatively charged poly(2‐acrylamido‐2‐methylpropane sulfonic acid sodium) (PNaAMPS) hydrogel via electrostatic interaction. The photoluminescent spectra indicate that the Ir^III–PNaAMPS hydrogel exhibits stable phosphorescence. In vitro cultivation of human retinal pigment epithelial cells demonstrates the cytocompatibility of the Ir^III–PNaAMPS hydrogel. This work herein represents a facile pathway for fabrication of phosphorescent hydrogels.     

Smart DNA Hydrogel Integrated Nanochannels with High Ion Flux and Adjustable Selective Ionic Transport

Nanochannels based on smart DNA hydrogels as stimulus‐responsive architecture are presented for the first time. In contrast to other responsive molecules existing in the nanochannel in monolayer configurations, the DNA hydrogels are three‐dimensional networks with space negative charges, the ion flux and rectification ratio are significantly enhanced. Upon cyclic treatment with K⁺ ions and crown ether, the DNA hydrogel states could be reversibly switched between less stiff and stiff networks, providing the gating mechanism of the nanochannel. Based on the architecture of DNA hydrogels and pH stimulus, cation or anion transport direction could be precisely controlled and multiple gating features are achieved. Meanwhile, G‐quadruplex DNA in the hydrogels might be replaced by other stimulus‐responsive DNA molecules, peptides, or proteins, and thus this work opens a new route for improving the functionalities of nanochannel by intelligent hydrogels.     

Preparation of Magnetic MIL-68(Ga) Metal–Organic Framework and Heavy Metal Ion Removal Application

A magnetic metal–organic framework nanocomposite (magnetic MIL-68(Ga)) was synthesized through a “one pot” reaction and used for heavy metal ion removal. The morphology and elemental properties of the nanocomposite were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), as well as zeta potential. Moreover, the factors affecting the adsorption capacity of the nanocomposite, including time, pH, metal ion type and concentration, were studied. It was found that the adsorption capacity of magnetic MIL-68(Ga) for Pb²⁺ and Cu²⁺ was 220 and 130 mg/g, respectively. Notably, the magnetic adsorbents could be separated easily using an external magnetic field, regenerated by ethylenediaminetetraacetic acid disodium salt (EDTA-Na₂) and reused three times, in favor of practical application. This study provides a reference for the rapid separation and purification of heavy metal ions from wastewater.     

Bioprinting Using Mechanically Robust Core–Shell Cell‐Laden Hydrogel Strands

The strand material in extrusion‐based bioprinting determines the microenvironments of the embedded cells and the initial mechanical properties of the constructs. One unmet challenge is the combination of optimal biological and mechanical properties in bioprinted constructs. Here, a novel bioprinting method that utilizes core–shell cell‐laden strands with a mechanically robust shell and an extracellular matrix‐like core has been developed. Cells encapsulated in the strands demonstrate high cell viability and tissue‐like functions during cultivation. This process of bioprinting using core–shell strands with optimal biochemical and biomechanical properties represents a new strategy for fabricating functional human tissues and organs.

     

Metal Ion Incorporated VPO Phases as Novel Catalysts

Vanadium phosphates function as catalysts for the selective oxidation of hydrocarbons with their activity being strongly dependent on their structure. Consequently, attempts have been made to synthesise novel phases in the VPO system through metal ion incorporation and evaluate the catalytic activity of these phases. It is shown that the incorporation of palladium or platinum leads to novel phases which vary according to the method of syntheses. The incorporated metal ions are catalytically active both for oxidation and reduction reactions with the activity varying according to the mode of incorporation. These phases constitute a novel class of compounds in which oxidation centres are substituted or dispersed within a VPO oxidation catalyst.     

手性药物的毛细管电泳拆分

以氧氟沙星、扑尔敏、特布它林和普萘洛尔为手性药物,分别采用羟丙基-β环糊精(HP--βCD)、羟丙基-β-环糊精结合羧甲基-β-环糊精(HP--βCD/CM--βCD)作手性拆分试剂,考察环糊精浓度和pH对手性选择性的影响。结果发现环糊精提供手性相互作用,而pH强烈地影响这种相互作用。以HP--βCD/CM-β-CD组成的双环糊精系统能更好地优化手性选择性,而通过调节pH可以获得需要的分离选择性、迁移次序。     

Ultrafiltration of Polymer-Metal Complexes for Metal Ion Removal from Wastewaters

Summary: A case-study using macromolecular metal complexes is described. The results of a process named Polymer Assisted Ultrafiltration (PAUF) for ion removal from various types of waters is reported. The water soluble polymers such as polyetilenimine (PEI), polyacrylic acid (PAA), polyacrylic acid sodium salt (PAASS) and poly(dimethylamine–co–epichlorohydrin–co–ethylenediamine) (PDEHED) as chelating agents, the Cu²⁺ as model ion and five ultrafiltration membranes have been used. The complexing agents were previously tested to establish the binding capacity and the best operating conditions for the process. Among the tested polymers the PEI appeared the most interesting one because its binding mechanism does not involve a counter ion release. It was tested in the simulation of wastewaters treatment containing the Cu²⁺ ion chelated with citric acid; this is a problem of interest in the recycling of water from soil washing operations. The polyethylenimine quantitatively bound the copper-citrate chelate at pH 5.5 and the three component complex was separated by UF membranes producing a permeate with very low metal concentration. The polymer regeneration was carried out with good results by operating with the diafiltration method. The copper ion present in the diafiltration permeate in a form chelated with citric acid was recovered by oxidising the citrate in a membrane photoreactor. The positive results of the described case-study show that Macromolecule-Metal Complexes play a key role for running effectively and selectively the PAUF process for removing metal ions from various type of waters.     

Ionic Dependence of Gelatin Hydrogel Architecture Explored Using Small and Very Small Angle Neutron Scattering Technique

The hierarchical structure of gelatin hydrogels mimics a natural extracellular matrix and provides an optimized microenvironment for the growth of 3D structured tissue analogs. In the presence of metal ions, gelatin hydrogels exhibit various mechanical properties that are correlated with the molecular interactions and the hierarchical structure. The structure and structural response of gelatin hydrogels to variation of gelatin concentration, pH, or addition of metal ions are explored by small and very small angle neutron scattering over broad length scales. The measurements of the hydrogels reveal the existence of a two‐level structure of colloid‐like large clusters and a 3D cage‐like gel network. In the presence of Fe³⁺ ions the hydrogels show a highly dense and stiff network, while Ca²⁺ ions have an opposite effect. The results provide important structural insight for improvement of the design of gelatin based hydrogels and are therefore suitable for various applications.     

On-Demand Release of Urea From a Cellulosic Hydrogel Using a Sprinkler Based Irrigation (SBI) Model

In this work, epichlorohydrin (Ech) crosslinked cellulose hydrogels have been prepared and loaded with urea (Ur) for controlled release as a fertilizer. A detailed study of swelling behavior of these hydrogels and their urea releasing capacity has been carried out under various experimental conditions. The dynamic swelling and release data has been applied on various kinetic models. Finally, using a novel Sprinkler Based Irrigation (SBI) model, a model plant has been irrigated with water in the presence of urea-loaded hydrogel. It was found that plants, irrigated in the presence of urea-loaded hydrogel exhibited a better growth as compared to the control plant sample.     

Functionalization of MWNTs with Hyperbranched PEI for Highly Selective Isolation of BSA

Cationic hyperbranched BPEI was immobilized on the surface of MWNTs via electrostatic interactions between the positively charged protonated amines within the polymer and the carboxyl groups on the chemically oxidized MWNT surface. The functionalized BPEI‐MWNTs were characterized by FT‐IR, TGA, TEM and surface charge analysis, and it was used as a bio‐sorbent for the adsorption of proteins. CD spectra showed no conformational change of BSA during the adsorption/desorption process. A dynamic adsorption capacity of 167 mg · g^?1 for BSA was achieved. With a sample volume of 2.0 mL, an enrichment factor of 10 was obtained along with an adsorption efficiency of 100%, a recovery of 100%, a sampling frequency of 10 h^?1 and a RSD of 2.6% at 25 µg · mL^?1 BSA.

     

Microwave‐Assisted Hydrogel Synthesis: A New Method for Crosslinking Polymers in Aqueous Solutions

It has been found that hydrogels may be formed by microwave irradiation of aqueous solutions containing appropriate combinations of polymers. This new method of hydrogel synthesis yields sterile hydrogels without the use of monomers, eliminating the need for the removal of unreacted species from the final product. Results for two particularly successful combinations, poly(vinyl alcohol) with either poly(acrylic acid) or poly(methylvinylether‐alt‐maleic anhydride), are presented. Irradiation using temperatures of 100–150 °C was found to yield hydrogels with large equilibrium swelling degrees of 500–1000 g g⁻¹. Material leached from both types of hydrogel shows little cytotoxicity towards HT29 cells.     

A Novel Approach to Prepare Porous Poly(N‐isopropylacrylamide) Hydrogel with Superfast Shrinking Kinetics

In this study, the hydrophobic liquid template method was firstly used to prepare temperature sensitive, porous poly(N‐isopropylacrylamide) (PNIPAAm) hydrogel. During the radical polymerization, hydrophobic polydimethylsiloxane (PDMS) and surfactant sodium dodecyl sulfate (SDS) were used as liquid templates and stabilizer, respectively. After removal of the liquid templates, porous PNIPAAm hydrogel was obtained. This gel exhibited superfast shrinking properties when being transferred from below to above the lower critical solution temperature (LCST), which was ascribed to the interconnected porous structures.

     

Creating Complex Polyacrylamide Hydrogel Structures Using 3D Printing with Applications to Mechanobiology

Due to its favorable physical and chemical properties, including chemical inertness, low fouling by biological molecules, high porosity and permeability, optical transparency, and adjustable elasticity, polyacrylamide has found a wide range of biomedical and non‐biomedical applications. To further increase its versatility, this communication describes a simple method, using readily available reagents and equipment, for 3D printing polyacrylamide hydrogels at a resolution of 100–150 μm to create complex structures. As a demonstration of the application, the method is used for creating a lab‐on‐a‐chip cell culture surface with micropatterned stiffness, which then leads to the discovery of stiffness‐guided collective cell segregation distinct from durotaxis. The present technology is expected to unleash new applications such as the construction of biocompatible elastic medical devices and artificial organs.