TEMPERATURE AND pH RESPONSE,AND SWELLING BEHAVIOR OF POROUS ACRYLONITRILE-ACRYLIC ACID COPOLYMER HYDROGELS

Macroporous acrylonitrile-acrylic acid （AN-AA） copolymer hydrogels were synthesized by flee-radical solution polymerizations, using ammonium persulfate （APS）/N,N,N＇,N＇-tetramethylethylenediamine （TEMED） redox initiator system and alcohols porogens. The morphology, temperature and pH sensitive swelling behavior, and swelling kinetics of the resulting hydrogels were investigated. It was found that alcohol type and concentration had great influences on the pore structure and porosity of hydrogels. The pore size of hydrogel increases with the moderate increase of the length of alcohol alkyl chain. However, a further increase of alkyl length would result in the formation of cauliflower-like structure and the decrease of pore size. The porosity of hydrogels increases with the increase of porogen concentration in the polymerization medium. The hydrogels with macroporous structure swell or shrink much faster in response to the change of pH in comparison with the conventional hydrogel without macroporous structure. Furthermore, the response rate is closely related to the porosity of the hydrogels, which could be easily controlled by modulating the concentration of the porogen in the medium. The circular swelling behavior of hydrogels indicated the formation of a relaxing three-dimensional network.

Porous hydrogel arrays for hepatoma cell spheroid formation and drug resistance investigation

Drug resistance is one of the major obstacles in the drug therapy of cancers.Efforts in this area in pre-clinical research have focused on developing novel platforms to evaluate and decrease drug resistance.In this paper,inspired by the structure of hives where swarms live and breed,we propose porous hydrogel arrays with a uniform pore structure for the generation of hepatoma cell spheroids and the investigation of drug resistance.The porous hydrogel arrays were fabricated using polyeth-ylene glycol diacrylate(PEGDA)hydrogel to negatively replicate a well-designed template.Benefiting from the elaborate processing of the template,the prepared porous hydrogel arrays possessed a uniform pore structure.Due to their anti-adhesion properties and the excellent biocompatibility of the PEGDA hydrogel,the hepatoma cells could form well-defined and uni-form hepatoma cell spheroids in the porous hydrogel arrays.We found that the resistant hepatoma cell spheroids showed more significant Lenvatinib resistance and a migratory phenotype compared with a two-dimensional(2D)cell culture,which reveals the reason for the failure of most 2D cell-selected drugs for in vivo applications.These features give such porous hydrogel arrays promising application prospects in the investigation of tumor cell spheroid culture and in vitro drug resistance.

Preparation and characterization of the n-HA/PVA/CS porous composite hydrogel☆

In this paper,a new method combines chemical/physical crosslinking,and emulsification-foaming porogenic was adopted to prepare n-hydroxyapatite(n-HA)/polyvinyl alcohol(PVA)/chitosan(CS)porous composite hydrogel using artificial cornea scaffold materials.The fabricate conditions,including the type and amount of emulsification-foaming porogen,mixing time and speed etc.were researched.The results showed the optimal condition that the alkylphenol polyoxyethylene ether(OP)acted as emulsification-foaming porogen,with the ratio of WPVA/WOP as 3.75,and mixing 15 min with a stirring speed of 800 r·min-1.Additionally,the fabricated composite hydrogel scaffold materials possessed interconnected internal holes,a moisture content of above 65%,and tensile strength of above 6 MPa.In vitro cytotoxicity and acute systemic toxicity assay confirmed that the scaffolds did not show any cytotoxicity.The as-prepared hydrogel could be a promising candidate for artificial cornea scaffold material.

Wearable pressure sensors based on antibacterial and porous chitosan hydrogels for full-range human motion detection

Wearable pressure sensors made from conductive hydrogels hold significant potential in health monitoring.However,limited pressure range(Pa to hundreds of kPa)and inadequate antibacterial properties restrict their practical applications in diagnostic and health evaluation.Herein,a wearable high-performance pressure sensor was assembled using a facilely prepared porous chitosan-based hydrogel,which was constructed from commercial phenolphthalein particles as a sacrificial template.The relationship between the porosity of hydrogels and sensing performance of sensors was systematically explored.Herein,the wearable pressure sensor,featuring an optimized porosity of hydrogels,exhibits an ultrawide sensing capacity from 4.83 Pa to 250 k Pa(range-to-limit ratio of 51,760)and high sensitivity throughout high pressure ranges(0.7 kPa~(-1),120–250 kPa).The presence of chitosan endows these hydrogels with outstanding antibacterial performance against E.coli and S.aureus,making them ideal candidates for use in wearable electronics.These features allow for a practical approach to monitor full-range human motion using a single device with a simple structure.

Full-thickness osteochondral defect repair using a biodegradable bilayered scaffold of porous zinc and chondroitin sulfate hydrogel

The regeneration of osteochondral tissue necessitates the re-establishment of a gradient owing to the unique characteristics and healing potential of the chondral and osseous phases.As the self-healing capacity of hyaline cartilage is limited,timely mechanical support during neo-cartilage formation is crucial to achieving optimal repair efficacy.In this study,we devised a biodegradable bilayered scaffold,comprising chondroitin sulfate(CS)hydrogel to regenerate chondral tissue and a porous pure zinc(Zn)scaffold for regeneration of the underlying bone as mechanical support for the cartilage layer.The photocured CS hydrogel possessed a compressive strength of 82 kPa,while the porous pure Zn scaffold exhibited a yield strength of 11 MPa and a stiffness of 0.8 GPa.Such mechanical properties are similar to values reported for cancellous bone.In vitro biological experiments demonstrated that the bilayered scaffold displayed favorable cytocompatibility and promoted chondrogenic and osteogenic differentiation of bone marrow stem cells.Upon implantation,the scaffold facilitated the simultaneous regeneration of bone and cartilage tissue in a porcine model,resulting in(i)a smoother cartilage surface,(ii)more hyaline-like cartilage,and(iii)a superior integration into the adjacent host tissue.Our bilayered scaffold exhibits significant potential for clinical application in osteochondral regeneration.

A double-network porous hydrogel based on high internal phase emulsions as a vehicle for potassium sucrose octasulfate delivery accelerates diabetic wound healing

Diabetic wounds are a difficult medical challenge.Excessive secretion of matrix metalloproteinase-9(MMP-9)in diabetic wounds further degrades the extracellular matrix and growth factors and causes severe vascular damage,which seriously hinders diabetic wound healing.To solve these issues,a double-network porous hydrogel composed of poly(methyl methacrylate-co-acrylamide)(p(MMA-co-AM))and polyvinyl alcohol(PVA)was constructed by the high internal phase emulsion(HIPE)technique for the delivery of potassium sucrose octasulfate(PSO),a drug that can inhibit MMPs,increase angiogenesis and improve microcirculation.The hydrogel possessed a typical polyHIPE hierarchical microstructure with interconnected porous morphologies,high porosity,high specific surface area,excellent mechanical properties and suitable swelling properties.Meanwhile,the p(MMA-co-AM)/PVA@PSO hydrogel showed high drug-loading performance and effective PSO release.In addition,both in vitro and in vivo studies showed that the p(MMA-co-AM)/PVA@PSO hydrogel had good biocompatibility and significantly accelerated diabetic wound healing by inhibiting excessive MMP-9 in diabetic wounds,increasing growth factor secretion,improving vascularization,increasing collagen deposition and promoting re-epithelialization.Therefore,this study provided a reliable therapeutic strategy for diabetic wound healing,some theoretical basis and new insights for the rational design and preparation of wound hydrogel dressings with high porosity,high drug-loading performance and excellent mechanical properties.

RAFT一步法制备温度和pH双重响应的多孔智能水凝胶及其性能

通过可逆加成-断裂链转移聚合法(RAFT)一步反应成功合成了温度和pH双重敏感的聚乙二醇甲基丙烯酸酯(OEGMA)-co-丙烯酸梳形/多孔智能水凝胶。采用扫描电镜(SEM)对水凝胶结构进行表征,结果表明,随着加入的致孔剂聚乙二醇(PEG)分子量越大、加入量越多,所得多孔水凝胶的孔径就越大、孔的数目就越多。对水凝胶进行溶胀测试,结果表明,在RAFT试剂的调控下所得凝胶的结构更均匀,因此所得凝胶的溶胀性能较好;经PEG致孔后的水凝胶,其溶胀程度和响应速率相对于致孔前都有所提高;此外OEGMA侧链PEG的长度和交联剂中间链段的长度都对凝胶的溶胀性能有显著的影响。

Hydrogel-based composites beyond the porous architectures for electromagnetic interference shielding

With the rapid development of the electronic industry and wireless communication technology,electromagnetic interference(EMI)or pollution has been increasingly serious.This not only severely endangers the normal operation of electronic equipment but also threatens human health.Therefore,it is urgent to develop high-performance EMI shielding materials.The advent of hydrogel-based materials has given EMI shields a novel option.Hydrogels combined with conductive functional materials have good mechanical flexibility,fatigue durability,and even high stretchability,which are beneficial for a wide range of applications,especially in EMI shielding and some flexible functional devices.Herein,the current progress of hydrogel-based EMI shields was reviewed,in the meanwhile,some novel studies about pore structure design that we believe will help advance the development of hydrogel-based EMI shielding materials were also included.In the outlook,we suggested some promising development directions for the hydrogel-based EMI shields,by which we hope to provide a reference for designing hydrogels with excellent EMI shielding performance and multifunctionalities.

Stimuli-Responsive Polypeptide-Based Supramolecular Hydrogels Mediated by Ca^2+ Ion Cross-Linking

Background and Originality Content Hydrogels,which retain a large amount of water,possess tunable porous three-dimensional nanostructure.They are known to resemble human tissue that can offer many advantages in biomedical applications such as tissue engineering,drug delivery and surgical dressings.1141 Stimuli-responsive hydrogels,referred as smart hydrogels can rapidly respond in a controlled manner to external stimuli,such as temperature,pH,light,etc.[s]In particular,the thermal-responsive hydrogels exhibit sol-to-gel phase transi­tion upon heating up to lower critical gelation temperatures(CGTs).

Capillary shrinkage of graphene oxide hydrogels

Conventional carbon materials cannot combine high density and high porosity,which are required in many applications,typically for energy storage under a limited space.A novel highly dense yet porous carbon has previously been produced from a three-dimensional(3D)reduced graphene oxide(r-GO)hydrogel by evaporation-induced drying.Here the mechanism of such a network shrinkage in r-GO hydrogel is specifically illustrated by the use of water and 1,4-dioxane,which have a sole difference in surface tension.As a result,the surface tension of the evaporating solvent determines the capillary forces in the nanochannels,which causes shrinkage of the r-GO network.More promisingly,the selection of a solvent with a known surface tension can precisely tune the microstructure associated with the density and porosity of the resulting porous carbon,rendering the porous carbon materials great potential in practical devices with high volumetric performance.

Porous tantalum-composited gelatin nanoparticles hydrogel integrated with mesenchymal stem cell-derived endothelial cells to construct vascularized tissue in vivo

The ideal scaffold material of angiogenesis should have mechanical strength and provide appropriate physiological microporous structures to mimic the extracellular matrix environment.In this study,we constructed an integrated three-dimensional scaffold material using porous tantalum(pTa),gelatin nanoparticles(GNPs)hydrogel,and seeded with bone marrow mesenchymal stem cells(BMSCs)-derived endothelial cells(ECs)for vascular tissue engineering.The characteristics and biocompatibility of pTa and GNPs hydrogel were evaluated by mechanical testing,scanning electron microscopy,cell counting kit,and live-cell assay.The BMSCs-derived ECs were identified by flow cytometry and angiogenesis assay.BMSCs-derived ECs were seeded on the pTa-GNPs hydrogel scaffold and implanted subcutaneously in nude mice.Four weeks after the operation,the scaffold material was evaluated by histomorphology.The superior biocompatible ability of pTa-GNPs hydrogel scaffold was observed.Our in vivo results suggested that 28 days after implantation,the formation of the stable capillary-like network in scaffold material could be promoted significantly.The novel,integrated pTa-GNPs hydrogel scaffold is biocompatible with the host,and exhibits biomechanical and angiogenic properties.Moreover,combined with BMSCs-derived ECs,it could construct vascular engineered tissue in vivo.This study may provide a basis for applying pTa in bone regeneration and autologous BMSCs in tissue-engineered vascular grafts.

Hydrogel-derived nitrogen-doped porous carbon framework with vanadium nitride decoration for supercapacitors with superior cycling performance

Transition metal nitrides(TMNs)and their composites with carbon materials hold tremendous potential for supercapacitor(SC)electrodes because of their excellent electronic conductivity and electrochemical activity.However,realizing cycling stable TMN/carbon-based supercapacitors with economically viable and environmentally-friendly approaches remains a significant challenge.Significantly,polyacrylamide(PAM)hydrogel,as a water-soluble linear polymer electrolyte,is expected to be a remarkable candidate precursor for preparing N-doped porous carbon(NPC)due to the high contents of carbon and nitrogen elements.In this study,vanadium nitride(VN)embedded in PAM hydrogel-derived NPC was fabricated successfully via an ammonia-free process.The VN/NPC delivers a high specific capacitance of 198.3 F g^(−1)at a current density of 1 A g^(−1),with a remarkable cycling stability of 107%after 16,000 cycles.The electrochemical performances of VN/NPC compared to bare VN nanoparticles are strongly improved due to the composite structure.Additionally,the VN/NPC-based solid-state symmetric device delivers an excellent energy density of 21.97µWh cm^(−2)at a power density of 0.5 mW cm^(−2),and an outstanding cycling durability of 90.9%after 18,000 cycles.This work paves the way to design metal nitride/porous carbon materials,which also opens up unique horizons for the recovery of hydrogel electrolyte.

Sub-nanopores-containing N,O-codoped porous carbon from molecular-scale networked polymer hydrogel for solid-state supercapacitor

A template-free carbonization-activation route is developed to fabricate sub-nanopore-containing porous carbon by using a novel polypyrrole(PPy)hydrogel as a precursor.This design of PPy hydrogel precursor containing molecular-scale grids(diameter~2.0 nm)allows for homogeneous N,O-codoping into the porous carbon scaffold during the pyrolysis process.A subsequent activation step produces activated porous carbons(APCs)with tailored pore structures,which renders the APCs abundant subnanopores on their surface to increase the specific capacitance as extra capacitance sites.Coupled with large specific surface area and abundant heteroatoms,the optimized APC4/1 displays excellent specific capacitance of 379 F/g for liquid-state supercapacitor and 230 F/g for solid-state supercapacitor.The solid-state supercapacitor shows a high energy density of 22.99 Wh/kg at power density of 420 W/kg,which is higher than most reported porous carbon materials and satisfy the urgent requirements of elementary power source for electric vehicles.Moreover,this method can be easily modified to fabricate sub-nanopore-containing porous carbons with preferred structures and compositions for many applications.

Preparation of porous semi-IPN temperature-sensitive hydrogel-supported nZVI and its application in the reduction of nitrophenol

Nanoscale zero-valent iron(n ZVI) particles supported on a porous, semi-interpenetrating(semi-IPN), temperature-sensitive composite hydrogel(PNIPAm-PHEMA). n ZVI@PNIPAmPHEMA, was successfully synthesized and characterized by FT-IR, SEM, EDS, XRD and the weighing method. The loading of nZVI was 0.1548 ± 0.0015 g/g and the particle size was30–100 nm. NZVI was uniformly dispersed on the pore walls inside the PNIPAm-PHEMA.Because of the well-dispersed n ZVI, the highly porous structure, and the synergistic effect of PNIPAm-PHEMA, nZVI@PNIPAm-PHEMA showed excellent reductive activity and wide p H applicability. 95% of 4-NP in 100 m L of 400 mg/L 4-NP solution with initial p H 3.0–9.0 could be completely reduced into 4-AP by about 0.0548 g of fresh supported n ZVI at 18–25 °C under stirring(110 r/min) within 45 min reaction time. A greater than 99% 4-NP degradation ratio was obtained when the initial p H was 5.0–9.0. The reduction of 4-NP by nZVI@PNIPAm-PHEMA was in agreement with the pseudo-first-order kinetics model with Kobsvalues of 0.0885–0.101 min-1.NZVI@PNIPAm-PHEMA was able to be recycled, and about 85% degradation ratio of 4-NP was obtained after its sixth reuse cycle. According to the temperature sensitivity of PNIPAmPHEMA, n ZVI@PNIPAm-PHEMA exhibited very good storage stability, and about 88.9%degradation ratio of 4-NP was obtained after its storage for 30 days. The hybrid reducer was highly efficient for the reduction of 2-NP, 3-NP, 2-chloro-4-nitrophenol and 2-chloro-4-nitrophenol. Our results suggest that PNIPAm-PHEMA could be a good potential carrier, with n ZVI@PNIPAm-PHEMA having potential value in the application of reductive degradation of nitrophenol pollutants.

Mechanical and Biotribological Properties of PVA/SB Triple-Network Hydrogel for Biomimetic Artificial Cartilage

Poly (vinyl alcohol) hydrogel has been perceived as a promising replacement for articular cartilage due to its superior water-absorption ability and excellent biocompatibility, but its mechanical properties are still insufficient. In this study, the poly (vinyl alcohol)/sodium tetraborate triple-network (PVA/SB TN) hydrogel was developed by repeated freeze–thaw method. Scanning electron microscopy images demonstrated that the structure of as-prepared hydrogels was three-dimensional porous network structure similar to that of natural articular cartilage. Compared to the pure PVA hydrogel, the mechanical performance of the PVA/SB TN hydrogels were improved by 116% and 461% in tensile and compressive strengths, respectively. This was mainly because that the complexation reaction between the PVA and SB strengthened the stability of the hydrogel network. Notably, the biotribological performance of PVA hydrogel has also been improved significantly. Even at high load, the friction coefficient of the PVA/SB TN hydrogel was both very low in calf serum or deionized water. This PVA/SB TN hydrogel with good mechanical property and low friction has high application potential in cartilage repair.

Tailored boron phosphate monolithic foam with multimodal hierarchically porous structure and its applications

The synthesis of multimodal hierarchically porous materials is of great challenge by facile approach.Herein,we assemble BPO_(4) hollow spheres into macroscopic foam materials with multimodal hierarchically porous structure by combining down-to-up process and Ostwald ripening effect.Tailored monolithic B_(2)O_(3)@BPO_(4) foams were obtained from a sticky hydrogel precursor by a one-step annealing process.The foam has the self-supporting frame of BPO_(4) hollow spheres with covering B_(2)O_(3) nanowires and shows excellent permeability and relatively high surface area due to hierarchical structure.The formation mechanism of monolithic B_(2)O_(3)@BPO_(4) foams mainly undergoes inflation,particle aggregation,and Ostwald ripening process.Monolithic foams exhibit superior catalytic activity in oxidation dehydrogenation of alkanes due to the sufficient exposure of active sites over the special frame structure.Furthermore,various monolithic functionalized BPO_(4) foam composites can be easily synthesized and exhibit superior performance in different applications including the oxidation of carbon monoxide,and the self-driven removal of organic pollutants.More interestingly,we also found the sticky hydrogel precursor possesses good heat shielding effect.This work provides a new insight for constructing multimodal hierarchically porous materials with the remaining superior property of nanoscale to cope with various challenges.

Soft-template synthesis of hierarchically porous structured polydimethylsiloxane toward flexible capacitive pressure sensor

Flexible pressure sensors play an important role in the field of monitoring, owing to their inherent safety and the fact that they are embedded at the material level. Capacitive pressure sensors have been proven to be quite versatile, with the ability to change the sensitivity and monitoring range by modifying the pore structure of the dielectric layer(elastic modulus). In this paper, capacitive pressure sensors are devised, comprising hierarchical porous polydimethylsiloxane. Due to the inherent hollow and hierarchical micropore structure, the capacitive pressure sensor allows operation at a wider pressure range(~1000 kPa) while maintaining sensitivity(6.33 MPa-1) in the range of 0–300 k Pa. Subsequently, the capacitance output model of the sensor is optimized, which provides an overall approximation of the experimental values for the sensor performance. Additionally, the signal response of the“break up the whole into parts”(by analysis of the whole sensor in parts) is simulated and outputted by the finite element analysis. The simplified analysis model provides a good understanding of the relationship between the local pressure and the signal response of the pressure sensor. For practical applications, seal monitoring and rubber wheel pressure array system are tested, and the proposed sensor shows sufficient potential for application in large deformation elastomer products.

多孔复合水凝胶负载角膜缘干细胞重建眼表

干细胞疗法是一种用于重建角膜缘干细胞缺乏症(LSCD)患者眼表的新技术.然而,目前报道的干细胞疗法治疗LSCD仅局限于二维(2D)培养体系,不能模拟干细胞在体内生存的原生微环境.本研究基于多孔明胶甲基丙烯酰(GelMA)/丝素蛋白甲基丙烯酸缩水甘油酯(SilMA),制备了一种可注射的光交联水凝胶用于负载角膜缘干细胞(LSCs)以重建眼表.多孔GelMA/SilMA水凝胶具有优异的透明度和良好的粘附性.更重要的是,该水凝胶保持了兔LSCs的活力,支持了兔LSCs的粘附,并促进了它们在体外3D培养环境中的迁移.蛋白质组学分析证实,多孔GelMA/SilMA水凝胶3D细胞培养体系能够保持LSCs的自我更新和分化能力.此外,组织学分析表明,负载LSCs的多孔GelMA/SilMA水凝胶能够有效的促进LSCD再上皮化.多孔水凝胶能够简化连续细胞培养的相关操作,以构建具有细胞均匀分布的眼表.这些发现为干细胞疗法和再生医学用于眼表重建提供了有价值的见解.

Highly stretchable double-network gel electrolytes integrated with textile electrodes for wearable thermo-electrochemical cells

Thermo-electrochemical cells(TECs)provide a new potential for self-powered devices by converting heat energy into electricity.However,challenges still remain in the fabrication of flexible and tough gel electrolytes and their compat-ibility with redox actives;otherwise,contact problems exist between electrolytes and electrodes during stretching or twisting.Here,a novel robust and neutral hydrogel with outstanding stretchability was developed via double-network of crosslinked carboxymethyl chitosan and polyacrylamide,which accommodated both n-type(Fe^(2+)/Fe^(3+))and p-type([Fe(CN)_(6)]^(3-)/[Fe(CN)_(6)]^(4-))redox couples and maintained stretchability(>300%)and recoverability(95%compression).Moreover,poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)textile elec-trodes with porous structure are integrated into gel electrolytes that avoid contact issues and effectively boost the P_(max) of n-and p-type thermocell by 76%and 26%,respectively.The optimized thermocell exhibits a quick current density response and is continually fully operational under deformations,which satisfies the working conditions of wearable devices.Multiple thermocells(four pairs)are effectively connected in alternating single n-and p-type cells in series and out-putted nearly 74.3 mV atΔT=10℃.The wearable device is manufactured into a soft-pack thermocells to successfully harvest human body heat and illuminate an LED,demonstrating the potential of the actual application of the thermocell devices.