Search

The field of biocatalysis is expanding owing to the increasing demand for efficient low-cost green chemical processes. However, a feasible strategy for achieving product separation, enzyme recovery, and high catalytic efficiency in biocatalysis remains elusive. Herein, we present thermoresponsive Pickering high internal phase emulsions (HIPEs) as controllable scaffolds for efficient biocatalysis; these HIPEs demonstrate a transition between emulsification and demulsification depending on temperature. Ultra-high-surface-area Pickering HIPEs were stabilized by Candida antarctica lipase B immobilized on starch particles modified with butyl glycidyl ether and glycidyl trimethyl ammonium chloride, thus simplifying the separation and reuse processes and significantly improving the catalytic efficiency. In addition, the switching temperature can be precisely tuned by adjusting the degree of substitution of the modified starches to meet the temperature demands of various enzymes. We believe that this system provides a green platform for various interfacial biocatalytic processes of industrial interest.

Green technologies, environmental protection, and sustainable development are some of the most important issues in today's world. Herein, a low-cost, environment-friendly, and sustainable strategy for fabricating a superwettable porous polymer sphere is reported for the treatment of various kinds of oil-in-water and water-in-oil emulsions. A thermoresponsive 2-hydroxy-3-butoxypropyl starch (HBPS) was synthesized as a representative natural material by simple chemical modification with butyl glycidyl ether, and was used as an effective stabilizer for Pickering emulsion formation. The state of the resulting emulsions could be switched by adjusting the temperature, with emulsification at low temperatures (lower than the lower critical solution temperature (LCST) of HBPS) and demulsification at high temperatures (higher than the LCST of HBPS). Based on this temperature-switchable emulsion system, a straightforward recyclable Pickering emulsion polymerization was designed and used for the fabrication of polymer spheres. A Pickering emulsion polymerization is an emulsion polymerization process in which the colloidal stability of the produced polymer dispersion is supported by solid particles. The distinct superwettability (superlipophilicity and under-oil superhydrophobicity), porosity, and small pore size of polymer spheres achieved resulted in an excellent performance in separating oil-in-water and water-in-oil emulsions with separation efficiencies over 99.9%. This work not only achieved a highly energy-efficient green recyclable Pickering emulsion polymerization system and provided a valuable strategy for the green synthesis process but also resulted in the fabrication of novel spheres with outstanding properties for separating various types of emulsions, with attractive prospects for advanced applications in separating complex emulsions, wastewater treatment, and environmental protection.

We developed tough, rapid-recovery composite hydrogels that are fabricated via core–shell microgel covalent bonding and Fe3+ dynamic metal coordination cross-linking. First, core–shell microgels are used as cross-linking agents and initiators to prepare homogeneous hydrogel networks with rapid recovery in the absence of an organic cross-linking agent. The toughness and recoverability of the composite hydrogels can be improved by adding the dynamic reversibility of ionic cross-linking. Owing to the synergistic effect of microgel covalent bonding, Fe3+ coordination cross-linking, and H-bond cross-linking, the multi-cross-linked composite hydrogels exhibit excellent toughness and a fast recovery rate. These characteristics demonstrate that the dynamic reversibility of the ionic cross-linking can significantly improve the toughness and recoverability of the hydrogels. In addition, the core–shell microgels play a key role in toughening the hydrogels and accelerating their recovery by transferring stress to grafted polymer chains and homogenizing the hydrogel network.

An in situ hydrogel based on oxidation cholesterol starch (OCS) and O-carboxymethyl chitosan (CMCT) that is completely devoid of potentially cytotoxic small molecule cross-linkers and does not require complex manoeuvres or catalysis has been formulated and characterized. The network structure was created by Schiff base formation. The mechanical properties, internal morphology and swelling ability of the injectable hydrogel were examined. Rheological measurements demonstrated that increasing the concentration of the monomer improved the storage modulus. SEM showed that the hydrogel possessed a well-defined porous structure. In addition, the Schiff base reaction was acid sensitive. Under acid conditions, the hydrogel could hydrolyse quickly compared with high pH conditions. Doxorubicin (DOX) was used as a model drug to investigate the control and release properties of the hydrogel. The cytotoxic potential of the hydrogel was determined using an in vitro viability assay with L929 cells as a model and the results revealed that the hydrogel was non-cytotoxic.

In this work, a physically cross-linked hydrogel (HA gels) with high mechanical strength is synthesized via micellar copolymerization of acrylamide (AAm) and an anionic surface active monomer (surfmer), sodium 9 or 10-acrylamidostearic acid (NaAAS) without any adscititious surfactant or chemical cross-linkers. SEM and DLS characterizations indicate that the surfmer formed multi-micellar aggregates with 80–90 nm diameters above its critical micelle concentration, and serve as a crosslinked-center to endow the obtained hydrogel a robust three-dimensional architecture. Compared with the chemically cross-linked hydrogel, HA gels exhibit unusual swelling–deswelling behavior in water and a pulsatile swelling–deswelling behavior is exhibited with alternating pH changes from 5 to 10 because the presence of carboxyl in the surfmer, demonstrating a smart characteristic of the hydrogel. Moreover, the presence of the surfmer greatly improve the mechanical properties of HA gels. A hydrogel containing 20% (mol/mol) surfmer shows a compression strength of 22.50 MPa at a strain of 90% and can be elongated to 13 times its original length. Furthermore, the HA gels show a significant hysteresis recovery after large deformation, underlying a serious energy-dissipation mechanism. This uncommon swelling behavior and mechanical properties of the HA gels result from its special characteristic of cross-linked units. A self-healing ability is expected for this physical hydrogel in future applications in biotechnology.

Two di-nuclear non-ionic MRI contrast agents, (Gd-DO3A)2-BMQX and (Gd-DO3A)2-BMP, have been designed and synthesized by fusing the DO3A units together with a quinoxalinyl or pyrazinyl moiety. They have improved longitudinal relaxivities of 5.23 and 5.16 mM Gd−1 s−1, respectively, at 20 MHz magnet, 37 °C and pH 7.0. In addition, they possess high thermodynamic stability and kinetic inertness. The cytotoxicity studies indicated that the toxicity of these two agents were low. All these properties satisfy the requirements for clinical applications.

A novel approach is presented for fabricating the thermo-responsive poly(N-isopropylacrylamide) hydrogels (TPHs) using starch-based nanospheres with derivable allyl groups as nanoscale crosslinkers. The obtained hydrogels possess an extremely high mechanical strength and a remarkably rapid shrinking time, which is much shorter than the time it will take for a conventional hydrogel (CH). Moreover, the effects of the crosslink density on the swelling, deswelling, and mechanical properties are also systematically studied. The results show that TPHs can sustain strength two hundred times more than the CH, and the characteristic time of deswelling is almost eight times shorter than that of CH. These excellent properties of the TPH gels can be attributed to their special microstructure and the even distribution of the starch-based nanospheres in the hydrogel network.