Search results for "hydrogels"

Energy Consumption for the Desalination of Salt Water Using Polyelectrolyte Hydrogels as the Separation Agent

2017

The energy consumption for a novel desalination approach using charged hydrogels under externally applied pressure is experimentally measured and calculated. The salt separation is based on a partial rejection of mobile salt ions caused by the fixed charges inside the polyelectrolyte network. Self-synthesized and commercial poly(acrylic acid) hydrogels are used to study the desalination performance in reference to sodium chloride solutions within the concentration range of 0.1–35 g L−1. The influence of various synthetic parameters, such as the degree of crosslinking (DC) and the size and shape of the particles, is investigated. Furthermore, the effect of process parameters including the am…

Micro- to Nanoscale Bio-Hybrid Hydrogels Engineered by Ionizing Radiation

2021

Bio-hybrid hydrogels consist of a water-swollen hydrophilic polymer network encapsulating or conjugating single biomolecules, or larger and more complex biological constructs like whole cells. By modulating at least one dimension of the hydrogel system at the micro- or nanoscale, the activity of the biological component can be extremely upgraded with clear advantages for the development of therapeutic or diagnostic micro- and nano-devices. Gamma or e-beam irradiation of polymers allow a good control of the chemistry at the micro-/nanoscale with minimal recourse to toxic reactants and solvents. Another potential advantage is to obtain simultaneous sterilization when the absorbed doses are wi…

Equivalences between refractive index and equilibrium water content of conventional and silicone hydrogel soft contact lenses from automated and manu…

2007

PURPOSE: The purpose of the present study was to develop mathematical relationships that allow obtaining equilibrium water content and refractive index of conventional and silicone hydrogel soft contact lenses from refractive index measures obtained with automated refractometry or equilibrium water content measures derived from manual refractometry, respectively. METHODS: Twelve HEMA-based hydrogels of different hydration and four siloxane-based polymers were assayed. A manual refractometer and a digital refractometer were used. Polynomial models obtained from the sucrose curves of equilibrium water content against refractive index and vice-versa were used either considering the whole range…

Microscopic observations of superficial ultrastructure of unworn siloxane-hydrogel contact lenses by cryo-scanning electron microscopy

2006

The purpose of this study was to analyze three commercial siloxane-hydrogel contact lens materials, lotrafilcon A, balafilcon A, and galyfilcon A, by cryogenic scanning electron microscopy (cryoSEM). The fully hydrated lenses were frozen in slush liquid nitrogen and qualitatively observed in a cryogenic scanning electron microscope. The superficial ultrastructure of the siloxane-hydrogels was observed at the areas where the lens fractured during sample cryogenic preparation. There are qualitative differences among the three examined materials in the complex polymer network structure existing between the outer layer and the underlying polymer. CryoSEM, although destructive, is a useful tool …

Transformation of vaterite nanoparticles to hydroxycarbonate apatite in a hydrogel scaffold: relevance to bone formation.

2020

Biomimetic materials have been gaining increasing importance for use as bone biomaterials, because they may provide regenerative alternatives for the use of autologous tissues for bone regeneration. We demonstrate a promising alternative for the use of biomimetic materials based on a biodegradable PEG hydrogel loaded with vaterite nanoparticles as mineral storage. Vaterite, the least stable CaCO3 polymorph, is stable enough to ensure the presence of a potential ion buffer for bone regeneration, but still has sufficient reactivity for the transformation from CaCO3 to hydroxyapatite (HA). A combination of powder X-ray diffraction (PXRD), electron microscopy, and Fourier-transform infrared (FT…

First bisphosphonate hydrogelators: potential composers of biocompatible gels

2020

Recently, investigation of hydrogels has gained ever increasing attention mostly because of their biomedical and pharmaceutical properties, and novel hydrogelators are constantly studied to find functional applications. Bisphosphonates (BPs) are well-known compounds applicable in different fields but are mostly used in clinics as drugs for bone-related diseases. In this study, a novel class of BP-hydrogelators together with a BP-organogelator was found, and the gelating abilities of the compounds were studied. Several techniques to analyze the structure and the properties of the formed gels were used, including solid state 13C and 31P CPMAS and solution state NMR spectroscopy, IR spectrosco…

Hybrid supramolecular gels of Fmoc-F/halloysite nanotubes: Systems for sustained release of camptothecin

2017

Supramolecular gel hybrids obtained by self-assembly of Fmoc-L-phenylalanine (Fmoc-F) in the presence of functionalized halloysite nanotubes (f-HNT) were obtained in biocompatible solvents and employed as carriers for the delivery of camptothecin (CPT) molecules. The synthesis of the new f-HNT material as well as its characterization are described. The properties of the hybrid hydrogels and organogels were analyzed by several techniques. The presence of small amounts of f-HNT allows good dispersion of the tubes and the subsequent formation of homogeneous gels. The experimental results show that f-HNT functions only as an additive in the hybrid gels and does not demonstrate gelator behavior.…

Attachement and spreading of fibroblasts on an RGD peptide-modified injectable hyaluronan hydrogel

2004

Hyaluronan (HA) hydrogels resist attachment and spreading of fibroblasts and most other mammalian cell types. A thiol-modified HA (3,3'-dithiobis(propanoic dihydrazide) [HA-DTPH]) was modified with peptides containing the Arg-Gly-Asp (RGD) sequence and then crosslinked with polyethylene glycol (PEG) diacrylate (PEGDA) to create a biomaterial that supported cell attachment, spreading, and proliferation. The hydrogels were evaluated in vitro and in vivo in three assay systems. First, the behavior of human and murine fibroblasts on the surface of the hydrogels was evaluated. The concentration and structure of the RGD peptides and the length of the PEG spacer influenced cell attachment and spre…

Porous gelatin cryogels as cell delivery tool in tissue engineering.

2007

Sepiolite-Hydrogels: Synthesis by Ultrasound Irradiation and Their Use for the Preparation of Functional Clay-Based Nanoarchitectured Materials.

2021

International audience; Sepiolite and palygorskite fibrous clay minerals are 1D silicates featuring unique textural and structural characteristics useful in diverse applications, and in particular as rheological additives. Here we report on the ability of grinded sepiolite to generate highly viscous and stable hydrogels by sonomechanical irradiation (ultrasounds). Adequate drying of such hydrogels leads to low-density xerogels that show extensive fiber disaggregation compared to the starting sepiolite-whose fibers are agglomerated as bundles. Upon re-dispersion in water under high-speed shear, these xerogels show comparable rheological properties to commercially available defibrillated sepi…