Papers by Keyword: Hydrogel

Abstract: Graphene, a typical two-dimensional planar monolayer of sp²carbon atoms, has attracted significant attention due to its outstanding physical and chemical properties. Nowadays, many graphene-based composites have been synthesized. Among them, graphene hydrogels (including graphene oxide hydrogel and reduced graphene oxide hydrogel) as a kind of graphene-based composites have a wide application prospect. In this paper, the progresses of graphene-based hydrogels are reviewed, and the prospects for the development of graphene-based hydrogels are also discussed.

Abstract: The double-layered PVA/nanohydroxyapatite (nHA)-poly (vinyl alcohol)(PVA)-sodium alginate (SA) porous composite scaffolds used as synthetic articular cartilage were prepared by the freeze-thawing method, gas foaming method and crosslink method of Ca²⁺ ion, i.e., upper PVA layer for the cartilage substitute and underlying SA30 porous hydrogels for bone bonding. The microstructure and morphology of composite hydrogels were characterized using scanning electronic microscopy (SEM).It had high porosity and uniform pores. The content of HA in SA30 matrix were tested by Energy-dispersive X-ray spectroscopy (EDS). The biological properties of the composite hydrogels had been evaluated by co-culture and MTT. All results indicate that the PVA/SA30 hydrogels has good potential for repairing or replacing articular cartilage.

Abstract: The uniformly cross-linked gellan gum hydrogel with sodium montmorillonite (Na-MMT), organo-montmorillonite (CTAB-MMT) and Cloisite 15A were successfully prepared. The compression performances of the hydrogels were investigated. The results show that the GG hydrogels containing Cloisite 15A required smallest volume to achieve optimum compression stress, modulus and compression strain at 5% (w/w) compared to both Na-MMT and CTAB-MMT at 10% (w/w), respectively. The decrease in compression performances of gellan gum hydrogel at higher concentration containing those clays could be due to agglomeration process which created the entangled structure and bring up the brittleness of hydrogel properties. Overall, the presence of the clays significantly improved the mechanical performances of gellan gum hydrogels which beneficial to be used in tissue engineering.

Abstract: The work is aimed to investigate the suitability of poly (γ-glutamic acid) (γ-PGA) for the hydrophilic finishing of polyester fiber. γ-PGA hydrogel was successfully synthesized by a simple mixture process in the aqueous solution. A novel hydrophilic finishing agent was prepared by γ-PGA hydrogel. The rheology behavior study indicated that γ-PGA solution and hydrophilic finishing agent performed pseudoplastic fluid and approximately Newtonian behavior, respectively. The particle diameter determined that particles in hydrophilic finishing agent reached micro-nanograde. Furthermore, polyester fiber was treated with γ-PGA solution and hydrophilic finishing agent. Moisture regain was evaluated as a key performance, results shown the hydrophilicity of polyester fiber was greatly enhanced by γ-PGA finishing.

Abstract: The cellulose-based hydrogel was successfully prepared from rayon fiber residue obtained from the fiber manufacturing industry. By chemical means, the hydrogel was simply prepared at an ambient temperature by mixing rayon with carboxymethyl cellulose (CMC) in NaOH/urea solution with epichlorohydrin (ECH) as a crosslinking agent. Rayon cellulose was used for stabilizing of hydrogel structure, providing a dimensional stability to the hydrogel whereas CMC acted as a porogen, widening the pore size within the hydrogel structure while swelling in water. With increasing CMC content, the percent water uptake of the hydrogel was increased but the structural stability was impaired. The prepared rayon cellulose/CMC hydrogel could take up more than 200% water within 60 minutes with an appropriate rayon cellulose-to-CMC ratio of 1:1 providing an ultimate balance between percent water uptake and the structural stability of the hydrogel. Its percent water uptake was as high as 285% to its initial dry weight.

Abstract: Current studies showed that UV LED system is a green technology and highly efficient as compared to UV Mercury (UV Hg) system. In this study, the UV LED curing formulations of polyacrylamide (PAAm) hydrogels were developed. The formulations consisted of acrylamide (AAm) as a main monomer, N,N’-methylenebisacrylamide as a crosslinker and photoinitiator. UV LED emits monochromatic light sources only (365 nm or 385 nm). Thus, in order to developed formulation of UV LED curable hydrogels, a suitable water soluble photoinitiator (i.e. λ ~ 365 nm) has to be employed. A commercially available photoinitiator Oligo [2-hydroxy-2-methyl-1-[4-(1-methylvinyl) phenyl] propanone] under the trade name Chivacure 300 (λ ~ 330 nm) was chosen in the first formulations. However, due to limited solubility in water, addition of tetrahydrofuran (THF) at 9.5:0.5 ratio of water/THF was required for Chivacure 300. We also synthesized a photoinitiator based on 2,2-dimethoxy-2-phenyl acetophenone (DMPA) and methylated-β-cyclodextrin (MβCD) to be used in the second formulation. The complexation of DMPA and MβCD resulted in transparent and water-soluble supramolecular-structured photoinitiator (SSPI) (λ ~ 330 nm). Both formulations were irradiated using UV LED system (Hoenle AG, Germany, 365 nm) for 15 min. Synthesis of PAAm hydrogels with both photoinitiators has yielded almost complete conversion of hydrogels (> 80 %). Clearly, this study has revealed that enhanced formulation of UV LED curable hydrogels are due to appropriate choice of excellent water-solubility photoinitiators (Chivacure 300 and modified DMPA). We concluded that UV LED is an important tool for curing hydrogel formulations of various acrylate water-based monomers.

Abstract: This paper presents the development of silver nanoparticles entrapped starch-polyacrylic acid hydrogel by a one step facile strategy. Formation of silver nanoparticles was confirmed by TEM and SPRE. Hydrogen bond interaction present in the hydrogel network was manifested from the FTIR spectroscopy. Silver nanoparticles in the face centred cubic lattice were confirmed by XRD. Visco-elastic properties studied by rheological analysis showed storage modulus of ~1500 Pa and exhibited a high storage modulus than loss modulus revealing the formation of strong gels. Phase transition temperature was confirmed by DSC. Antimicrobial screening studies of these hybrid gel exhibited antimicrobial activity to E.coli and S.aureus suggesting its applications for gram + ve and gram - ve bacteria.

Abstract: The purpose of this research was to study water retention properties of superabsorbent hydrogel based on poly (acrylamide)/biofiller hydrogel and urea liquid fertilizer, by solution polymerization. Kenaf fiber (KF) was used as biofiller and the preparation of the poly (acrylamide)-grafted-kenaf fiber (PAAm-g-KF) hydrogel was carried out by polymerizing the monomer. Urea fertilizer was employed as polymerization media. N,N’-methylene bisacrylamide (MBA) was used as a crosslinker and ammonium persulfate (APS) as an initiator. Water retention of the hydrogel was studies in soil with three different samples (Controlled, PAAm Hydrogel, PAAm-g-KF). The PAAm-g-KF was also applied to agricultural field. The results show that PAAm-g-KF greatly improved water retention in the soil and agricultural field.

Abstract: In this article, the swelling behavior and swelling kinetic of poly (vinyl alcohol)/poly (γ-glutamic acid) hydrogel were investigated. It was found that the PGA/PVA hydrogels revealed the pH-sensitive property and exhibited a faster swelling at pH7.4. The study of swelling kinetics revealed that the swelling mechanism followed the non-Fickian diffusion mechanism.

Abstract: Various methods were developed to prepare hydrogels including photo-cross-linking, chemical cross-linking, enzymatic cross-linking, pH or temperature-induced gelation, ionic interaction, and hydrophobic interactions. Whereas silk fibroin gelation time was difficult to control by physical methods, the cross-linkers used in chemical technique were likely to reduce the cell biocompatibility. Sodium N-Lauroyl Sarcosinate (SNS), an amino acid-based surfactant, came into accelerate silk fibroin to form silk hydrogel. To monitor the gelation process and determine the gelation time, turbidity changes during gelation were measured by Synergy HT. Cylindrical gels have been measured with universal material experiment machine and KES for mechanical properties. Fibroblast (L929) cells were seeded on the surface of hydrogels to investigate the cell compatibility. The results show that the SNS/SF gelation time ranges from 20 min to 120 min, which is affected by environment temperature, the final concentrations of SF and SNS. Compared with pure silk fibroin hydrogels, the compression strength of SNS/SF gel is much stronger. SNS/SF gel has excellent compression-recovery performance in KES test as well. A logarithmic stable cell growth appears on the surface of SNS/SF hydrogels, which indicates that SNS/SF hydrogels have excellent cell compatibility. Therefore, the SNS/SF hydrogels have great potential in tissue repair for surgery.