共查询到20条相似文献,搜索用时 15 毫秒
1.
S. Partap A. Muthutantri I. U. Rehman G. R. Davis J. A. Darr 《Journal of Materials Science》2007,42(10):3502-3507
Controlled porosity alginate hydrogel monoliths were synthesised by simultaneous micelle templating (MT) and an internal gelation
reaction. In water, the self assembling surfactant, cetyltrimethylammonium bromide (CTAB) formed non-spherical micelles that
were used as a template for pore formation. The porous microstructure was assessed by mercury intrusion porosimetry (MIP),
helium pycnometry, X-ray microtomography (XMT) and scanning electron microscopy (SEM), respectively. The MT hydrogels displayed
relatively monodisperse pore size distributions (with pore sizes ranging from 32.5 μm to 164.0 μm), high total pore volumes
(4.5–20.3 cm3/g) and high degrees of porosity (83–97%). Some control over pore size distributions was achieved by varying the surfactant
concentration; higher surfactant concentrations, led to smaller pores with lower total pore volumes. Uniaxial compression
testing revealed that hydrogels made via MT are stable in cell culture media for 28 days. Fourier transform infrared (FTIR)
spectroscopy data, suggested that all surfactant could be removed from the final product by washing with ethanol and water,
making these hydrogels potentially suitable for tissue engineering (TE) applications. 相似文献
2.
In this study, an investigation is carried out on the influence of varying clay contents (25–43%), pH values (2–11 buffer solutions), heat treatment, temperatures (25–60 °C) and ionic strengths (saline solution, 10?7–0.1 M) on the water absorbency of polyacrylamide (PAAm)/laponite nanocomposite (NC) hydrogels in the absence of polyelectrolyte. For the influence of pH value on swelling behaviors, a maximum swelling ratio occurs at pH 11. Heat treatment of the hydrogels significantly improved the swelling capacity and created an obvious pH sensitive area (pH 3–4). The swelling capacity of the hydrogels was enhanced by increasing the temperature of the absorbing media. The results of swelling at different ionic strengths also indicate that the ionic strength can considerably weaken the swelling abilities of the NC hydrogels. 相似文献
3.
Mrcia Regina de Moura Fauze Ahmad Aouada Silvia Luciana Favaro Eduardo Radovanovic Adley Forti Rubira Edvani C. Muniz 《Materials science & engineering. C, Materials for biological applications》2009,29(8):2319-2325
The synthesis of thermosensitive Interpenetrating Polymer Network (IPN) hydrogels and the release of Bovine Serum Albumin (BSA) from the hydrogels were reported. The hydrogels, constituted of poly(N-isopropyl acrylamide) PNIPAAm network interpenetrated in alginate–Ca2+ network, were synthesized in a two-stepped process. In the first step, PNIPAAm network was synthesized from an aqueous solution containing N-isopropyl acrylamide (NIPAAm) monomers and N,N′-methylene-bis-acrylamide (MBAAm) co-monomers, and sodium alginate (SA) (1 or 2% w/v). The concentration of NIPAAm monomers in the hydrogel-forming solution was always 2.5, 5.0 or 10.0% (w/v). In the second step, alginate–Ca2+ networks were formed by immersion of the membrane, obtained on the first step, in a 1.0% (w/v) aqueous calcium chloride. The IPN hydrogels were characterized as a function of temperature (from 25 to 45 °C) through the following measurements: drop water contact angle (DWCA), compression elastic modulus (E) and cross-linking density (νe). The morphology was investigated using scanning electronic microscopy (SEM). In vitro release of BSA from the hydrogels was monitored by UV–Vis spectroscopy at 22 °C and 37 °C. DWCA results showed a decrease in the hydrogel hydrophilicity when the temperature and/or the PNIPAAm amount on hydrogels were increased. PNIPAAm-loader hydrogels are more compacted and presented elevated rigidity, mainly above 35 °C. This trend was attributed to the collapsing of PNIPAAm chains as the hydrogels were warmed above its Lower Critical Solution Temperature (LCST), which in aqueous solution is ca. 32–33 °C. The amount of BSA released from the alginate–Ca2+/PNIPAAm hydrogels changes inversely to both amount of PNIPAAm and temperature. The transport of BSA from the hydrogels was evaluated through a conventional model. In the lesser-compacted hydrogels the release occurs mostly by diffusion. In the more compacted ones the chain relaxation contributes to the BSA release. Thus, the alginate–Ca2+/PNIPAAm IPN-typed matrixes may be considered as smart hydrogels for the release of BSA, because the amount and rate of BSA released may be tailored by both the NIPAAm concentration in the hydrogel-forming solution and the control of temperature of hydrogel. 相似文献
4.
Mishra RK Datt M Pal K Banthia AK 《Journal of materials science. Materials in medicine》2008,19(6):2275-2280
In the current studies attempts were made to prepare hydrogels by chemical modification of pectin with ethanolamine (EA) in
different proportions. Chemically modified pectin products were crosslinked with glutaraldehyde reagent for preparing hydrogels.
The hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR), organic elemental analysis, X-ray diffraction
studies (XRD), swelling studies, biocompatibility and hemocompatibility studies. Mechanical properties of the prepared hydrogels
were evaluated by tensile test. The hydrogels were loaded with salicylic acid (used as a model drug) and drug release studies
were done in a modified Franz’s diffusion cell. FTIR spectroscopy indicated the presence of primary and secondary amide absorption
bands. XRD studies indicated increase in crystallinity in the hydrogels as compared to unmodified pectin. The degree of amidation
(D
A) and molar and mass reaction yields (Y
M and Y
N) was calculated based on the results of organic elemental analysis. The hydrogels showed good water holding properties and
were found to be compatible with B-16 melanoma cells & human blood. 相似文献
5.
Sema Ekici 《Journal of Materials Science》2011,46(9):2843-2850
Poly(N-isopropyl acrylamide) (PNIPAm)–carboxymethyl cellulose (CMC) full interpenetrating polymeric networks (IPNs), based on PNIPAm
and CMC, were prepared and investigated for adsorption of biomolecules utilizing a model protein, bovine serum albumin (BSA).
N-isopropyl acrylamide monomers were polymerized in the presence of a natural polymer, e.g., carboxymethyl cellulose sodium
salt. N,N′-methylenebisacrylamide (CL) was used to crosslink PNIPAm and CMC chains and IPN formed simultaneously. Spectroscopic and
thermal characterization of the hydrogels were done with IR spectroscopy and thermogravimetric analysis. The swelling properties
of PNIPAm and PNIPAm–CMC hydrogels were investigated as functions of the medium pH, temperature, ionic strength, and BSA.
It was observed that the adsorption of protein molecules onto the hydrogels was mainly dependent on temperature and pH of
the environment during the experiments. The maximum adsorption capacity (X) was observed at pH 4.7 which is the isoelectric point of BSA and at 40 °C for both hydrogels; and introducing CMC to PNIPAm
increased the protein adsorption of the hydrogel. Adsorbed amounts of BSA were 26.70 mg g−1 (4 °C) and 38.70 mg g−1 (40 °C) for PNIPAm–CMC full IPN hydrogels. Adsorbed BSA (up to 80%) was eluted in the elution medium containing 0.1 mol dm−3 NaSCN at pH 8.0. Synthesized cylindrically shaped PNIPAm–CMC full IPN hydrogels can be used for adsorption studies related
to the removal of proteins in pH- and temperature-sensitive biotechnological areas. 相似文献
6.
Psyllium polysaccharide is a bulk laxative and has been used for the treatment of constipation which is responsible for the
diverticulitis. Ciprofloxacin is an antibiotic used for the microorganism infested in the diverticula. Hence, the functionalization
of psyllium with polyvinyl alcohol (PVA) and poly(acrylamide) [poly(AAm)] will develop the drug delivery system (DDS) with
potential for dual action for the treatment of diverticulitis, that is, by treating the constipation due to laxative action
of psyllium and release of ciprofloxacin from DDS in controlled manner. The optimum conditions for the synthesis of hydrogels
have been obtained as 42.21 × 10−2 mol/L of AAm, 3% (w/v) of PVA, 32.43 × 10−3 mol/L of N,N′-methylenebisacrylamide (NN-MBA), 17.53 × 10−3 mol/L ammonium persulfate, and 1 g of psyllium. The characterization of the hydrogels has been carried out by SEMs, EDAX,
FTIR, and swelling studies. Swelling and drug release studies have also been carried out to determine the mechanism of swelling
of hydrogels and drug release from the drug loaded hydrogels. The release of the drug from the hydrogels occurred through
Fickian diffusion mechanism in pH 2.2 and pH 7.4 buffer. 相似文献
7.
Lesný P Prádný M Jendelová P Michálek J Vacík J Syková E 《Journal of materials science. Materials in medicine》2006,17(9):829-833
The growth of bone marrow stromal cells was assessed in vitro in macroporous hydrogels based on 2-hydro- xyethyl methacrylate (HEMA) copolymers with different electric charges. Copolymers
of HEMA with sodium methacrylate (MA−) carried a negative electric charge, copolymers of HEMA with [2-(methacryloyloxy)ethyl] trimethylammonium chloride (MOETA−) carried a positive electric charge and terpolymers of HEMA, MA− and MOETA+ carried both, positive and negative electric charges. The charges in the polyelectrolyte complexes were shielded by counter-ions.
The hydrogels had similar porosities, based on a comparison of their diffusion parameters for small cations as measured by
the real-time tetramethylammonium iontophoretic method of diffusion analysis. The cell growth was studied in the peripheral
and central regions of the hydrogels at 2 hours and 2, 7, 14 and 28 days after cell seeding. Image analysis revealed the highest
cellular density in the HEMA-MOETA+ copolymers; most of the cells were present in the peripheral region of the hydrogels. A lower density of cells but no difference
between the peripheral and central regions was observed in the HEMA-MA− copolymers and in polyelectrolyte complexes. This study showed that positively charged functional groups promote the adhesion
of cells. 相似文献
8.
Demet Kaya Aktaş Gülşen Akın Evingür Önder Pekcan 《Journal of Materials Science》2007,42(20):8481-8488
Steady-state fluorescence (SSF) technique was employed for studying swelling of polyacrylamide (PAAm) hydrogels. Disc-shaped
gels were prepared by free-radical crosslinking copolymerization of acrylamide (AAm) with N, N′- methylenebis (acrylamide) (BIS) as crosslinker in the presence of ammonium persulfate (APS) as an initiator. Pyranine was
introduced as a fluorescence probe. Fluorescence intensity of pyranine was measured during in situ swelling process at various
temperatures and it was observed that fluorescence intensity values decreased as swelling is proceeded. Li–Tanaka equation
was used to determine the swelling time constants, τc and cooperative diffusion coefficients, D
c from intensity, weight and volume variations during the swelling processes. It is observed that swelling time constants,
τc decreased and diffusion coefficients, D
c increased as the swelling temperature is increased. The swelling activation energies, ΔE were measured from the intensity, weight and volume variations and found to be 10.7, 32.2 and 64.1 kJ mol−1, respectively. 相似文献
9.
Nanocomposites of polyfuran (PF) and polythiophene (PTP) with montmorillonite clay (MMT) were prepared and modified by loading
of polyaniline (PANI) and polypyrrole (PPY) moieties via polymerization of aniline (ANI) and pyrrole (PY) in aqueous dispersions
of PF-MMT and PTP-MMT nanocomposites. Formation of PANI and PPY and their subsequent incorporation in the PF-MMT and PTP-MMT
composites was confirmed by FTIR absorption studies. X-ray diffraction (XRD) patterns of PANI and PPY modified PF-MMT and
PTP-MMT composites showed that PF-MMT and PTP-MMT intercalates were still present in the modified composites. Scanning electron
microscopic analysis revealed distinctive morphological patterns of the various composite particles. The dc conductivity values
of PANI and PPY modified PF-MMT and PTP-MMT composites were in the order of 10−2 S/cm in either system – a value much improved compared to the same for both of the unmodified PF-MMT (10−7 S/cm) and PTP-MMT (10−5 S/cm) nanocomposites respectively. 相似文献
10.
External stimuli response on a novel chitosan hydrogel crosslinked with formaldehyde 总被引:1,自引:0,他引:1
Keeping in mind the significance of hydrogels as an external stimuli sensitive super absorbing material, some transparent
covalent hydrogels of chitosan were prepared by crosslinking with varying amounts of formaldehyde solution used as crosslinking
agent. The characteristics of hydrogels were investigated by Fourier transform infrared (FT-IR) spectroscopy and swelling
experiments. The effect of crosslinking agent on water absorbency has been investigated. The hydrogels exhibited a relatively
higher swelling ratio in the range of 2066–3306% and equilibrium water content (EWC) in the range of 95-38–97 06% at pH 7
and 35°C temperature. The influence of external stimuli such as pH, temperature, and ionic strength of the swelling media
on equilibrium swelling properties has been observed. Hydrogels showed a typical pH and temperature responsive behaviour such
as low pH and high temperature has maximum swelling while high pH and low temperature show minimum swelling. An increase in
the ionic strength of swelling media caused a continuous decrease in the swelling of hydrogels at both acidic and basic pH. 相似文献
11.
Fauze A. Aouada Márcia R. de Moura William J. Orts Luiz H. C. Mattoso 《Journal of Materials Science》2010,45(18):4977-4985
PAAm–MC hydrogels as a potential delivery vehicle for the controlled release of paraquat pesticide was investigated, as they
play an essential role to use hydrogels in controlled release technology. The release kinetics of paraquat was determined
using UV–Vis measurements. The release mechanism of paraquat from PAAm–MC hydrogels was investigated through a semi-empirical
model proposed by Ritger and Peppas. In general, the initial rate of paraquat release was fast, decreasing after several days,
hence indicating that paraquat on the surface (or close to) of hydrogels diffused rapidly after the initial swelling of the
gel. Later, the cumulative release occurred in a very controlled and sustained manner, with the paraquat concentration maintaining
constant from 15 to 46 days. The paraquat release capacity was dependent on the swelling of the matrix and the density of
the network chains. The curves obtained from Peppas’s model presented good linearity (R
2 ≥ 0.999), indicating that such model can be applicable to analyze the systems. The n values for the pesticide release from hydrogels indicate that paraquat release has Fickian and non-Fickian diffusion, depending
of hydrogel formulation. The values of k showed that the release of paraquat becomes slower when the MC and AAm concentration increases. Finally, to the best of our
knowledge, we report a hydrogel-based vehicle (first carrier) that is able to prolong the sustained release of paraquat pesticide
up to 45 days, which is essential for its application in controlled release systems. 相似文献
12.
The objective of this research is to explore the synthesis of a new family of water soluble polycationic copolymeric precursors
that could be photo-crosslinked into hydrogels. The in vitro control release of ovalbumin protein (OVA) from this family of
hydrogels was also studied to assess the biomedical potential of this new family polycationic hydrogels. A series of novel
poly(VCL–AETA) copolymer hydrogels was fabricated in an aqueous medium via photo-induced polymerization and crosslinking of
hydrophobic N-vinylcaprolactam (VCL) and hydrophilic [2-(acryloxy)ethyl]trimethylammonium chloride (AETA) monomers over a wide range of
VCL to AETA feed molar ratios of 2:1, 1:1, 1:2, 1:5. N,N′-methylene bisacrylamide (MBA) was used as a crosslinker. Ovalbumin (OVA), a model antigen, was preloaded into poly(VCL–AETA)
hydrogel precursors and its release profiles in pH 7.4 PBS at 37°C were investigated as a function of VCL to AETA monomer
feed ratios over a period of 4 weeks. The in vitro results showed that OVA initial burst and subsequent sustained releases
could be controlled by 3 material parameters: the hydrophobic VCL to hydrophilic AETA monomer feed ratios, crosslinking density
and hydrogel degradation rate. Thus, the hydrophobic-hydrophilic VCL–AETA hydrogel network for controlled OVA release could
offer advantages over organic solvent-based single component polymer system. However, these in vitro OVA release profiles
may change in an in vivo environment. 相似文献
13.
C. Yürdü S. Işçi C. Ünlü O. Atici Ö. I. Ece N. Güngör 《Bulletin of Materials Science》2005,28(6):623-628
In this study, the rheologic and colloidal characterizations of sodium montmorillonite (NaMMT) were examined. Hexadecylamine
(CH3(CH2)15NH2, HDA) was added to the bentonite water dispersion (2%, w/w) in different concentrations in the range 5.6 × 10−4−9.4 × 10−3 mmol/l. The rheological and electrokinetic behaviour of aqueous montmorillonite dispersions was investigated as a function
of solid content and HDA concentration. The basal spacings of the HDA/NaMMT composites were studied by X-ray diffraction.
The FTIR spectra were obtained from the modified bentonite products, which revealed the characteristic absorbances after treatment
with HDA. 相似文献
14.
G. Fu W.O. Soboyejo 《Materials science & engineering. C, Materials for biological applications》2010,30(1):8-13
Thermo-responsive hydrogels are capable of swelling changes to external temperature. A series of modified poly (N-isopropylacrylamide) (PNIPA) hydrogels was synthesized by free radical polymerization in aqueous solution. Acrylamide (AAm) was used to increase the lower critical solution temperature (LCST), while sodium alginate (SA) was used to improve the swelling performance of the hydrogels. Experiments show that 5.5% mass ratio of AAm increased the LCST by about 9 °C above that of conventional PNIPA. Also, SA significantly improved the equilibrium swelling ratio associate with temperature change. Trypan blue diffusion revealed significant differences in the fluid release obtained from hydrogels with modified LCST and swelling properties. The implications of the modified fluid release and swelling characteristics are also discussed for the device design of thermo-sensitive hydrogels for localized drug delivery. 相似文献
15.
This paper reports the preparation of highly concentrated aqueous hydroxyapatite (HA) suspensions for slip casting of dense
bone implants. The dispersing behaviour of HA powders in aqueous media was monitored by viscosity and zeta potential analyses
as a function of pH of the slurry. The rheological properties of concentrated aqueous hydroxyapatite suspensions have been
characterized with varying pH, NH4PAA concentration and solids loading. The intrinsic pH of the suspension was found suitable for slip casting. The optimum
dispersant concentration is 0.75 wt.% for 75 wt.% solid loading. A stable suspension with 75 wt.% solid was suitable for slip
casting with viscosity of 0.36 Pa s at 100 s−1. Finally, crack-free and dense microstructures have been obtained successfully with a grain size of 2–5 μm. 相似文献
16.
Michelle Feeney Maria Antonietta Casadei Pietro Matricardi 《Journal of materials science. Materials in medicine》2009,20(5):1081-1087
A carboxymethyl derivative of scleroglucan (Scl-CM) with a derivatization degree of 65 ± 5% was synthesized. The rheological
behaviour of this novel polymer was studied and compared with that of the starting polymer. We observed that the charged moieties
carried on the chains could prevent the triple helix formation of Scl. Scl-CM aqueous solutions behave like true polymer solutions
up to 1% w/v, whereas above this concentration a weak gel behaviour was observed. CaCl2 addition to aqueous Scl-CM solutions led to a physical gel formation; the hydrogel strength was related to polymer and CaCl2 concentrations. Temperature sweeps, registered at 1 Hz on hydrogels differing in CaCl2 concentration, evidenced a gel → sol transition in the range of 30–40°C, depending on the molar ratio between carboxylic
groups and Ca+2. In order to verify a possible use of these hydrogels as drug delivery systems, acyclovir was loaded into the network. Rheological
analysis evidenced that the loaded drug can affect the hydrogel elastic modulus. The release of acyclovir in phosphate buffer
was evaluated at different temperatures in order to assess the suitability of this novel drug delivery system in topical applications. 相似文献
17.
Xavier P. Morelle Widusha R. Illeperuma Kevin Tian Ruobing Bai Zhigang Suo Joost J. Vlassak 《Advanced materials (Deerfield Beach, Fla.)》2018,30(35)
Hydrogels consist of hydrophilic polymer networks dispersed in water. Many applications of hydrogels rely on their unique combination of solid‐like mechanical behavior and water‐like transport properties. If the temperature is lowered below 0 °C, however, hydrogels freeze and become rigid, brittle, and non‐conductive. Here, a general class of hydrogels that do not freeze at temperatures far below 0 °C, while retaining high stretchability and fracture toughness, is demonstrated. These hydrogels are synthesized by adding a suitable amount of an ionic compound to the hydrogel. The present study focuses on tough polyacrylamide‐alginate double network hydrogels equilibrated with aqueous solutions of calcium chloride. The resulting hydrogels can be cooled to temperatures as low as ?57 °C without freezing. In this temperature range, the hydrogels can still be stretched more than four times their initial length and have a fracture toughness of 5000 J m?2. It is anticipated that this new class of hydrogels will prove useful in developing new applications operating under a broad range of environmental and atmospheric conditions. 相似文献
18.
Peeling from strong adhesion is hard, and sometimes painful. Herein, an approach is described to achieve both strong adhesion and easy detachment. The latter is triggered, on‐demand, through an exposure to light of a certain frequency range. The principle of photodetachable adhesion is first demonstrated using two hydrogels as adherends. Each hydrogel has a covalent polymer network, but does not have functional groups for bonding, so that the two hydrogels by themselves adhere poorly. The two hydrogels, however, adhere strongly when an aqueous solution of polymer chains is spread on the surfaces of the hydrogels and is triggered to form a stitching polymer network in situ, in topological entanglement with the pre‐existing polymer networks of the two hydrogels. The two hydrogels detach easily when the stitching polymer network is so functionalized that it undergoes a gel–sol transition in response to a UV light. For example, two pieces of alginate–polyacrylamide hydrogels achieve adhesion energies about 1400 and 10 J m?2, respectively, before and after the UV radiation. Experiments are conducted to study the physics and chemistry of this strong and photodetachable adhesion, and to adhere and detach various materials, including hydrogels, elastomers, and inorganic solids. 相似文献
19.
Guilherme Ferreira Laercio Caetano Renata S. D. Castro Pedro Magalhães Padilha Gustavo Rocha Castro 《Clean Technologies and Environmental Policy》2011,13(2):397-402
This paper describes the synthesis, modification, and application of modified silica for the removal of lead ions from aqueous
medium. The modification reaction provided a reduction in surface are from 737 to 399 m2 g−1, which was attributed to the 4-amine-2-mercaptopyrimidine molecule attachment onto its surface. The characterization through
FTIR spectra demonstrated bands at 3347 cm−1 assigned to N–H stretching vibrations and the absence of thiol bands at 2600 e 2547 cm−1 at Si-mod spectrum is an indicative that the attachment occurred via SH groups. The linearization of adsorption isotherm
data through the modified Langmuir equation resulted in a maximum adsorption capacity of 2.9 μmol g−1. The material was applied in a continuous flow system in the preconcentration of water samples from Paraná River and the
results were in agreement with metal concentration determined directly through atomic absorption spectrometry with graphite
furnace. The method validation was performed through analysis of water standard reference material (1643e), which also presented
a 7.2-fold enrichment factor. 相似文献
20.
Samples of untreated ultra-high molecular weight polyethylene (UHMW-PE), UHMW-PE sterilized with γ-rays in nitrogen atmosphere
(conventional UHMW-PE, widely used for articulating surfaces in endoprostheses) and UHMW-PE, which has been crosslinked by
electron beam irradiation and annealed subsequently, were stabilized with α-tocopherol and aged in air at 120∘C as well as in 10% aqueous hydrogenperoxide with 0.04 mg/ml FeCl3 as catalyst at 50∘C. The oxidative degradation was monitored with the help of infrared spectroscopy (FTIR), differential scanning calorimetry
(DSC), solubility measurements and size exclusion chromatography (SEC) and were compared to unstabilized samples. When aged
in air at 120∘C, the crosslinked UHMW-PE showed a slightly slower increase of the carbonyl (CO)-number (according to DIN 53383) in FTIR
than conventional UHMW-PE. A stabilisation with 0.4% w/w α-tocopherol resulted in an increase of lifetime by a factor of approx.
40 for all samples. Ageing in 10% aqueous H2O2 at 50∘C yielded similar results for all three unstabilised samples. The addition of the natural antioxidant α-tocopherol led to
a prolongation of lifetime by a factor of approx. 2.5. A linear loss of α-tocopherol was detected during ageing. An increase
of crystallinity as well as lamella thickness during ageing was observed with the help of DSC. The two-phase structure of
crosslinked UHMW-PE with two melting endotherms at 114∘C and 137∘C was replaced very quickly by a single melting point at 130∘C. This effect was delayed with the stabilized samples. In the solubility and SEC measurements, a severe molecular degradation
and drop of molar mass of all materials could be observed after ageing in H2O2, leading to a complete destruction and, in case of crosslinked UHMW-PE, to a serious damage of the molecular network, respectively.
in partial fulfilment of a Ph.D. (Dr.mont.) thesis at the University of Leoben 相似文献