Search results for "Self-healing"
showing 10 items of 222 documents
CROSSLINKED HYALURONAN WITH A PROTEIN-LIKE POLYMER: NOVEL BIORESORBABLE FILMS FOR BIOMEDICAL APPLICATIONS
2007
In this work, novel hydrogel films based on hyaluronan (HA) chemically crosslinked with the alpha,beta-poly(N-2-hydroxyethyl) (2-aminoethylcarbamate)-D,L-aspartamide (PHEA-EDA) were produced by solution casting method. The goal was to exploit both the biological key role of HA in tissue repair and regeneration, and the versatility of a synthetic protein-like polymer as the PHEA-EDA, in order to obtain biomaterials with physicochemical and biological properties suitable for a clinical use. By varying the molar ratio between the PHEA-EDA amino groups and HA carboxyl groups, three different films were obtained and characterized. Particularly FTIR, swelling, hydrolysis, and enzymatic degradatio…
Naphthalimide imidazolium-based supramolecular hydrogels as bioimaging and theranostic soft materials
2020
1,8-Naphthalimide-based imidazolium salts differing for the alkyl chain length and the nature of the anion were synthesized and characterized to obtain fluorescent probes for bioimaging applications. First, their self-assembly behavior and gelling ability were investigated in water and water/dimethyl sulfoxide binary mixtures. Only salts having longer alkyl chains were able to give supramolecular hydrogels, whose properties were investigated by using a combined approach of fluorescence, resonance light scattering, and rheology measurements. Morphological information was obtained by scanning electron microscopy. In addition, conductive properties of organic salts in solution and gel state we…
Biological oxygen apparent transmissibility of hydrogel contact lenses with and without organosilicon moieties.
2003
The instrument oxygen transmissibility (IOT) of organosilicon hydrogels, measured by electrochemical procedures, is 5-10 times larger than that of conventional hydrogels. A method is described that allows the estimation of the oxygen tension at the lens-cornea interface for closed- and open-eyelids situations by combining the IOT of the hydrogels and corneal parameters such as corneal thickness, corneal permeability and oxygen flux across the cornea. From these results the biological oxygen apparent transmissibility (BOAT) is obtained, an important parameter which an multiplication with the pressure of oxygen on the external part of the lens gives the oxygen flux onto the cornea. Contact le…
Investigation of self-healing mechanism on galvanized steels cut edges by coupling SVET and numerical modeling
2008
Local cathodic inhibition has been observed on the cut-edge of galvanized steel immersed in 0.03 M NaCl solution using the scanning vibrating electrode technique. The current distribution results indicate that cathodic inhibition occurs in a limited spatial zone located between the cathodic sites on the steel and the anodic sites on the exposed zinc surface. The experimental current distributions are compared with the results of numerical simulations that show the specific diagnostic features for the detection of cathodic inhibition from scanning vibrating electrode technique (SVET) data so as to distinguish the zero current regions from experimental artifacts due to the lateral resolution …
An Inverse Thermogelling Bioink Based on an ABA-Type Poly(2-oxazoline) Amphiphile
2021
Hydrogels are key components in several biomedical research areas such as drug delivery, tissue engineering, and biofabrication. Here, a novel ABA-type triblock copolymer comprising poly(2-methyl-2-oxazoline) as the hydrophilic A blocks and poly(2-phenethyl-2-oxazoline) as the aromatic and hydrophobic B block is introduced. Above the critical micelle concentration, the polymer self-assembles into small spherical polymer micelles with a hydrodynamic radius of approx 8-8.5 nm. Interestingly, this specific combination of hydrophilic and hydrophobic aromatic moieties leads to rapid thermoresponsive inverse gelation at polymer concentrations above a critical gelation concentration (20 wt %) into…
Surface-Assisted Self-Assembly of a Hydrogel by Proton Diffusion
2018
International audience; Controlling supramolecular growth at solid surfaces is of great importance to expand the scope of supramolecular materials. Here we describe a dendritic benzene-1,3,5-tricarboxamide peptide conjugate whose assembly can be triggered by a pH jump. Stopped flow kinetics and mathematical modeling provide a quantitative understanding of the nucleation, elongation, and fragmentation behavior in solution. To assemble the molecule at a solid-liquid interface, we use proton diffusion from the bulk. The latter needs to be slower than the lag phase of nucleation in order to progressively grow a hydrogel outwards from the surface. Our method of surface-assisted self-assembly is …
Thermodynamic control over energy dissipation modes in dual-network hydrogels based on metal-ligand coordination.
2020
Modern polymeric hydrogels use reversible bonds to mimic biological functionalities. However, true biological materials benefit from several supramolecular elements and deliver multiple functions at the same time. To approach similar creation and control of multiple different functional elements in a synthetic soft material, we develop a model dual-network hydrogel in which multiple energy dissipating modes are formed by metal–ligand coordination and regulated by their association thermodynamics. This idea is realized by using linear and tetra-arm poly(ethylene glycol) (PEG) precursors with complementary reactive end groups. The former also carries terpyridine ligands on both ends, which fo…
Wavelength-Selective Softening of Hydrogel Networks.
2021
Photoresponsive hydrogels hold key potential in advanced biomedical applications including tissue engineering, regenerative medicine, and drug delivery, as well as intricately engineered functions such as biosensing, soft robotics, and bioelectronics. Herein, the wavelength-dependent degradation of bio-orthogonal poly(ethylene glycol) hydrogels is reported, using three selective activation levels. Specifically, three chromophores are exploited, that is, ortho-nitrobenzene, dimethyl aminobenzene, and bimane, each absorbing light at different wavelengths. By examining their photochemical action plots, the wavelength-dependent reactivity of the photocleavable moieties is determined. The wavele…
Near-Infrared Spectra of Water Confined in Silica Hydrogels in the Temperature Interval 365−5 K
2002
We have used a sol−gel technique to obtain optically transparent hydrogels in which water is trapped within a tridimensional disordered silica matrix. A suitable aging of these hydrogels enables to have transparent noncracking samples down to cryogenic temperatures. We report the optical absorption spectra, in the near-infrared region, of water trapped in our silica hydrogels, measured in the temperature range 365−5 K, and we compare them with the same spectra of liquid water, measured in the temperature range 365−263 K. The data show that it is possible to have noncrystallizing water even at 5 K: indeed, the overtone bands at ∼1.41 μm and at ∼1.155 μmtypical of “weakly bonded” water molec…
Porous structure of Purevision™ versus Focus® Night&Day™ and conventional hydrogel contact lenses
2002
The surface and bulk structures of hydrogel contact lenses that contain siloxane moieties, Purevision™ (balafilcon A) and Focus®Night&Day™ (lotrafilcon A), were investigated. Standard hydrogel lenses of low (Seequence®), medium (Acuvue®), and high water content (Precision UV®) were used as controls. All the lenses were dehydrated in a series of ethanol solutions of increased concentration, critical-point dried in CO2, and sputter coated with gold/palladium before they were examined by scanning electron microscopy. Of all lenses examined, only the balafilcon lenses presented, in addition to the polymer network porosity characteristic of all hydrogels, a macroporous structure that was observe…