以“豆腐的制作”畅谈胶体知识与水凝胶的前沿应用

通过深入挖掘“豆腐的制作”工艺中渗透的科学知识,介绍了如何充分提取大豆蛋白质、如何将生豆浆转变为豆腐等内容,主要呈现了豆腐制作过程中体现的蛋白质性质、胶体的稳定性及凝固剂促使大豆蛋白聚沉原理等知识,并对豆腐产品的结构特点进行适当延伸,进而介绍水凝胶的发展与前沿应用。加深学生对所学知识的理解,拓展视野,培养学生热爱生活的态度及科研乐趣。     

Ultrasonic-assisted synthesis of polyacrylamide/bentonite hydrogel nanocomposite for the sequestration of lead and cadmium from aqueous phase: Equilibrium,kinetics and thermodynamic studies

Clay-hydrogel nanocomposites are suitable material for mitigating the pollution/environmental impact because of their high adsorption capacity. In this study, the synthesis of polyacrylamide/bentonite hydrogel nanocomposite was assisted by ultrasound through successful incorporation of nanobentonite as filler and cross-linker into polyacrylamide framework. The adsorbent was characterized by FTIR, XRD, BET, SEM-EDX, and TEM in order to observe structural changes and sorption interactions. The effect of adsorbent dose, contact time, initial metal ion concentration and pH on the sequestration of Pb²⁺ and Cd²⁺ was analyzed. The adsorbent removed more than 95% Pb²⁺ and Cd²⁺ within first 20 min, which corresponds to relatively high pseudo-first order rate constant, k₁ (0.240 for Pb²⁺ and 0.253 1/min for Cd²⁺) and pseudo-second order rate constant, k₂ (0.031 for Pb²⁺ and 0.033 g/mg/min for Cd²⁺). The isotherm and kinetics modeling data were best described by Freundlich isotherm over the entire concentration range and pseudo-second order rate equation, respectively. The thermodynamic studies implied spontaneous and endothermic nature of adsorption process. The maximum adsorption capacity (138.33 for Pb²⁺ and 200.41 mg/g for Cd²⁺) determined using Langmuir model along with a good regeneration potential depicts that polyacrylamide/bentonite hydrogel nanocomposite could be used effectively for Pb²⁺ and Cd²⁺ uptake from aqueous solution.     

Determination of glucosamine and its derivatives released from photocrosslinked gelatin hydrogels using HPLC

A simple, accurate and validated reverse‐phase high‐performance liquid chromatography (HPLC)/UV method is developed for the determination of glucosamine hydrochloride (GlcN), N‐acetyl‐glucosamine (NAG) and N‐acryloyl‐glucosamine (AGA) released from photocrosslinked gelatin hydrogels. The HPLC separation was achieved on a Shimadzu InertSustain amino column (250 × 4.6 mm, 5 µm particle size) at room temperature using a mobile phase of acetonitrile–phosphate buffer (75:25, v/v, pH 6.0) at a flow rate of 1.0 mL/min and UV detection of 194 nm. The method was validated for specificity, linearity, limit of detection and quantification, accuracy, precision, extraction recovery and solution stability. The calibration curves were with excellent linearity, with correlation coefficients (R²) >0.999 for all three drugs. The intra‐ and inter‐day variation was <3.10% and the relative error was between ?1.43 and 1.78%. The extraction recovery results ranged from 94.62 to 99.33%, demonstrating the absence of matrix effect. The sample and standard solutions were stable for more than 2 months. The method was successfully used for the analysis of released properties of drugs physically encapsulated and chemically crosslinked in the gelatin hydrogels. Copyright © 2015 John Wiley & Sons, Ltd.     

Stimuli-Sensitive Self-Assembled Tubules Based on Lysine-Derived Surfactants for Delivery of Antimicrobial Proteins

Drug delivery vectors based on amphiphiles have important features such as versatile physicochemical properties and stimuli-responsiveness. Amino acid-based surfactants are especially promising amphiphiles due to their enhanced biocompatibility compared to conventional surfactants. They can self-organize into micelles, vesicles and complex hierarchical structures, such as fibers, twisted and coiled ribbons, and tubules. In this work, we investigated the self-assembly and drug loading properties of a family of novel anionic double-tailed lysine-derived surfactants, with variable degree of tail length mismatch, designated as mLys10 and 10Lysn, where m and n are the number of carbon atoms in the tails. These surfactants form tubular aggregates with assorted morphologies in water that undergo gelation due to dense entanglement, as evidenced by light and electron microscopy. Lysozyme (LZM), an enzyme with antimicrobial properties, was selected as model protein for loading. After the characterization of the interfacial properties and phase behavior of the amphiphiles, the LZM-loading ability of the tubules was investigated, under varying experimental conditions, to assess the efficiency of the aggregates as pH- and temperature-sensitive nanocarriers. Further, the toxicological profile of the surfactants per se and surfactant/LZM hydrogels was obtained, using human skin fibroblasts (BJ-5ta cell line). Overall, the results show that the tubule-based hydrogels exhibit very interesting properties for the transport and controlled release of molecules of therapeutic interest.     

Assembly of (l+d)-Tryptophan Derivatives Containing an Imidazole Group Selectively Forms a Rare Purple Ni2+-Hydrogel

Design of metal-selective hydrogels is attractive due to potential applications in materials and biological sciences. Although much progress has been made, assembly of both l - and d -amino acid derivatives was less explored for design of metallohydrogels. In this study, we synthesized a facile and small tryptophan derivative containing an imidazole ligand with both l - and d - configurations (denoted as l/d -ImW). Intriguingly, the assembly of (l+d) -ImW gelators was found to selectively form a Ni²⁺-hydrogel in aqueous medium at room temperature, which shows a rare purple color and exhibits excellent multi-responsiveness. In addition to insights into the gelation mechanism, this study provides a novel approach to the design of metallohydrogels, by the assembly of (l+d) -amino acid derivatives containing both aromatic rings and multiple metal coordination sites.     

Hydrogel‐coated polyurethane/urea shape memory polymer foams

Shape memory polymers (SMPs) are a class of responsive polymers that have attracted attention in designing biomedical devices because of their potential to improve minimally invasive surgeries. Use of porous SMPs in vascular grafts has been proposed because porosity aids in transfer of fluids through the graft and growth of vascular tissue. However, porosity also allows blood to leak through grafts so preclotting the materials is necessary. Here hydrogels have been synthesized from acrylic acid and N‐hydroxyethyl acrylamide and coated around a porous SMP produced from lactose functionalized polyurea‐urethanes. The biocompatibility of the polymers used to prepare the cross‐linked shape memory material is demonstrated using an in vitro cell assay. As expected, the hydrogel coating enhanced fluid uptake abilities without hindering the shape memory properties. These results indicate that hydrogels can be used in porous SMP materials without inhibiting the shape recovery of the material. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1389–1395     

Palladated halloysite hybridized with photo‐polymerized hydrogel in the presence of cyclodextrin: An efficient catalytic system benefiting from nanoreactor concept

Considering the excellent performance of halloysite as a catalyst support and in an attempt to benefit from the concept of nanoreactors in the catalysis, an innovative catalytic system has been designed, in which acrylamide and bis‐acrylamide were photo‐polymerized in the presence of palladated halloysite. The novel precipitation photo‐polymerization method avoided the formation of an extended polymeric network, but led to the formation of co‐polymer on the halloysite periphery. The co‐polymer exhibited good swellability in aqueous media and formed hydrogel. This hydrophilic environment around catalytic palladated halloysite can be considered as a nanoreactor that can concentrate the substrate and bring them into the vicinity of the palladated halloysite. This catalytic system was used for promoting hydrogenation of hydrophobic nitro arenes in aqueous media. To avoid immiscibility of hydrophobic substrates and hydrophilic nature of the nanoreactor, that emerged from swelling of hydrogel, β‐cyclodextrin (CD) was utilized as phase transfer agent. The results confirmed high catalytic activity of this catalytic system. Even highly hydrophobic substrates could tolerate hydrogenation under this protocol to furnish the corresponding product in high yield. Finally, the contribution of both CD and hydrogel to the catalysis was confirmed. Moreover, studying the recyclability of the catalyst as well as Pd leaching proved the high recyclability of the catalyst and low leaching of Pd nanoparticles.     

Preparation of colloidal crystal template for inverse opal hydrogels

Colloidal crystal template for inverse opal hydrogel is constructed by vertical deposition method using monodispersed silica nanospheres. By adjusting the concentration of monodispersed silica nanospheres, it is found that well-structured silica template with more than 20 layers is formed when the concentration of the silica is 3.5 wt%. To enhance its strength, the prepared template is put in an oven at 500 °C for 2 h. The surface of the template is divided into many blocks by cracks formed in the process of heat treatment. The number of blocks varies with the rising time of the temperature from 25 to 500 °C. Under the same magnification, blocks formed with the rising time of 150 min can be nearly 4 times more than the blocks with a rising time of 300 min or 500 min, which means the slow rising velocity of the temperature can lead to a better colloidal crystal template with fewer blocks.     

Antibacterial poly(ethylene glycol) hydrogels from combined epoxy‐amine and thiol‐ene click reaction

Antibacterial hydrogels containing quaternary ammonium (QA) groups were prepared via a facile thiol‐ene “click” reaction using multifunctional poly(ethylene glycol) (PEG). The multifunctional PEG polymers were prepared by an epoxy‐amine ring opening reaction. The chemical and physical properties of the hydrogels could be tuned with different crosslinking structures and crosslinking densities. The antibacterial hydrogel structures prepared from PEG Pendant QA were less well‐defined than those from PEG Chain‐End QA. Furthermore, functionalization of the PEG‐type hydrogels with QA groups produced strong antibacterial abilities against Staphylococcus aureus, and therefore has the potential to be used as an anti‐infective material for biomedical devices. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 656–667