Cryogenic formation-structure-property relationships of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) cryogels

Fabrication of superporous cryogels with amidoxime chelation sites and customizable 3D printing for targeted palladium recovery from secondary resources

Recovering precious metals such as palladium from secondary resources faces significant challenges, including the scarcity of efficient adsorbents capable of withstanding harsh acidic conditions and needing materials with high selectivity, mechanical stability, and scalability. In response to these challenges, we developed highly porous cryogels functionalized with sulfonic and amidoxime groups, achieving a unique combination of hydrophilicity, flexibility, and selectivity for Pd(II) ions. Using a redox cryopolymerization method, these cryogels attained a gel fraction of 100 % and a maximum adsorption capacity of 425.3 mg g-1 at 318 K, as the Langmuir isotherm model fitted. This work also combined 3D printing technology with cryopolymerization to create a highly selective, high mechanical strength and customizable shape adsorption material, overcoming traditional adsorption materials' limitations in acid conditions. This innovative combination fills the gap in selective palladium recovery in customizable super macroporous materials, offering a sustainable solution for precious metal recovery and setting a foundation for broader applications in adsorption separation.

A long-term storable gel-laden chip composite built in a multi-well plate enablingin situcell encapsulation for high-throughput liver model

Hydrogels are widely used as scaffold materials for constructingin vitrothree-dimensional microphysiological systems. However, their high sensitivity to various external cues hinders the development of hydrogel-laden, microscale, and high-throughput chips. Here, we have developed a long-term storable gel-laden chip composite built in a multi-well plate, which enablesin situcell encapsulation and facilitates high-throughput analysis. Through optimized chemical crosslinking and freeze-drying method (C/FD), we have achieved a high-quality of gel-laden chip composite with excellent transparency, uniform porosity, and appropriate swelling and mechanical characteristics. Besides collagen, decellularized extracellular matrix with tissue-specific biochemical compound has been applied as chip composite. As a ready-to-use platform,in situcell encapsulation within the gel has been achieved through capillary force generated during gel reswelling. The liver-mimetic chip composite, comprising HepG2 cells or primary hepatocytes, has demonstrated favorable hepatic functionality and high sensitivity in drug testing. The developed fabrication process with improved stability of gels and storability allows chip composites to be stored at a wide range of temperatures for up to 28 d without any deformation, demonstrating off-the-shelf products. Consequently, this provides an exceptionally simple and long-term storable platform that can be utilized for an efficient tissue-specific modeling and various biomedical applications.

Cryogelation reactions and cryogels: principles and challenges

Cryogelation is a powerful technique for producing macroporous hydrogels called cryogels. Although cryogelation reactions and cryogels were discovered more than 70 years ago, they attracted significant interest only in the last 20 years mainly due to their extraordinary properties compared to the classical hydrogels such as a high toughness, almost complete squeezability, a mechanically stable porous structure with honeycomb arrangement, poroelasticity, and fast responsivity against external stimuli. In this mini review, general properties of cryogelation systems including the cryoconcentration phenomenon responsible for the unique properties of the cryogels are discussed. The squeezability and poroelasticity of cryogels comparable to those seen with articular cartilage are also discussed. Cryogelation reactions conducted within the pores of preformed cryogels and some novel cryogels with attractive properties are then discussed in the last section.

Designing Silk-Based Cryogels for Biomedical Applications

There is a need to develop the next generation of medical products that require biomaterials with improved properties. The versatility of various gels has pushed them to the forefront of biomaterials research. Cryogels, a type of gel scaffold made by controlled crosslinking under subzero or freezing temperatures, have great potential to address many current challenges. Unlike their hydrogel counterparts, which are also able to hold large amounts of biologically relevant fluids such as water, cryogels are often characterized by highly dense and crosslinked polymer walls, macroporous structures, and often improved properties. Recently, one biomaterial that has garnered a lot of interest for cryogel fabrication is silk and its derivatives. In this review, we provide a brief overview of silk-based biomaterials and how cryogelation can be used for novel scaffold design. We discuss how various parameters and fabrication strategies can be used to tune the properties of silk-based biomaterials. Finally, we discuss specific biomedical applications of silk-based biomaterials. Ultimately, we aim to demonstrate how the latest advances in silk-based cryogel scaffolds can be used to address challenges in numerous bioengineering disciplines.

Chondroitin Sulfate-Based Cryogels for Biomedical Applications

Cryogels attained from natural materials offer exceptional properties in applications such as tissue engineering. Moreover, Halloysite Nanotubes (HNT) at 1:0.5 weight ratio were embedded into CS cryogels to render additional biomedical properties. The hemolysis index of CS cryogel and CS:HNT cryogels was calculated as 0.77 ± 0.41 and 0.81 ± 0.24 and defined as non-hemolytic materials. However, the blood coagulation indices of CS cryogel and CS:HNT cryogels were determined as 76 ± 2% and 68 ± 3%, suggesting a mild blood clotting capability. The maximum% swelling capacity of CS cryogel was measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, at pH 1.0, pH 7.4 and pH 9.0, respectively, which were reduced to 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, for CS:HNT cryogel. It was found that CS cryogels can hydrolytically be degraded 41 ± 1% (by wt) in 16-day incubation, whereas the CS:HNT cryogels degraded by 30 ± 1 wt %. There is no chelation for HNT and 67.5 ± 1% Cu(II) chelation for linear CS was measured. On the other hand, the CS cryogel and CS:HNT cryogel revealed Cu(II) chelating capabilities of 60.1 ± 12.5%, and 43.2 ± 17.5%, respectively, from 0.1 mg/mL Cu(II) ion stock solution. Additionally, at 0.5 mg/mL CS, CS:HNT, and HNT, the Fe(II) chelation capacity of 99.7 ± 0.6, 86.2 ± 4.7% and only 11.9 ± 4.5% were measured, respectively, while no Fe(II) was chelated by linear CS chelated Fe(II). As the adjustable and controllable swelling properties of cryogels are important parameters in biomedical applications, the swelling properties of CS cryogels, at different solution pHs, e.g., at the solution pHs of 1.0, 7.4 and 9.0, were measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, respectively, and the maximum selling% values of CS:HNT cryogels were determined as 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, at the same conditions. Alpha glucosidase enzyme interactions were investigated and found that CS-based cryogels can stimulate this enzyme at any CS formulation.

Single-, Double-, and Triple-Network Macroporous Rubbers as a Passive Sampler

Over the past decades, large quantities of organic compounds including polycyclic aromatic hydrocarbons (PAHs) entering aquatic systems create acutely toxic effects and chronic abnormalities in aquatic organisms. Passive sampling is an effective technique to detect organic compounds at very low concentrations in water by accumulating them in their structure to a measurable concentration level. Polymeric passive samplers reported so far have a nonporous structure, and hence, the absorption of organic compounds into the passive sampler is governed by their slow diffusion process. We present here novel macroporous rubber sorbents as monophasic passive samplers with tunable pore morphologies, extraordinary mechanical properties, and high sorption rates and capacities for PAHs. Sorbent materials based on single-network (SN), double-network (DN), and triple-network (TN) butyl rubber were prepared via the cryogelation technique from butyl rubber solutions in benzene as the solvent at -18 °C using a sulfur monochloride cross-linker. To obtain macroporous rubbers with DN and TN structures, the reactions were conducted in the macropores of SN and DN rubber networks, respectively. The porous morphology and the mechanical behavior of the rubbers can be tuned by adjusting the weight ratio w_R of the network components. The rubbers exhibit two generations of pores, namely, large and small pores with diameters 40-240 and 14-54 μm, respectively. The sizes of both large and small pores decrease and approach each other as w_R is increased. Four PAH compounds, namely, naphthalene, phenanthrene, fluoranthene, and pyrene with two to four aromatic rings, dissolved in filtered seawater with a salinity of 22 ppt were used to highlight the correlations between the properties of macroporous rubbers and their absorption rates and capacities. Nonporous silicone rubber reported before as a passive sampler has the lowest absorption rate and capacity as compared to the macroporous rubbers. The SN rubber absorbs most rapidly PAHs because of its largest porosity, whereas the TN rubber with the smallest pores exhibits the highest sorption capacity.