Temperature- and pH- Sensitive Hydrogels for Controlled Release of Antithrombotic Agents

1993 ◽  
Vol 331 ◽  
Author(s):  
Christopher S. Brazel ◽  
Nicholas A. Peppas
Keyword(s):  
Controlled Release ◽  
Methacrylic Acid ◽  
Blood Clot ◽  
Polymer Network ◽  
Temperature Sensitive ◽  
Kinetic Experiment ◽  
Temperature Changes ◽  
Thermally Responsive ◽  
Swelling Characteristics ◽  
Swelling Studies

AbstractPolymeric hydrogels capable of reversible swelling with changes in environmental temperature and pH were synthesized and studied as matrix systems capable of controlled release of antithrombotic drugs to the site of a blood clot. Monomers N-isopropylacrylamide (NIPAAm) and methacrylic acid (MAA) were chosen for the temperature- and pHdependent swelling characteristics of their polymers, respectively. Equilibrium swelling studies were performed as functions of pH and of temperature, and kinetic swelling studies were performed on the thermally responsive gels as a function of time after the gel was subjected to a step-change in temperature. Experimental results indicate that P(NIPAAmco- MAA) hydrogels can be synthesized so that they are either pH- or temperaturesensitive, depending upon the composition of the network. The pure PNIPAAm gels showed a lower critical solubility temperature (LCST) of around 32°C, below which the gel was in its swollen state, and above which the gel collapsed. As the amount of methacrylic acid in the gels was increased, the degree of swelling in deionized water decreased and the temperature sensitivity was lost. The hydrogels containing MAA displayed a transition in swelling behavior between pH 4 and 6. The mesh sizes of the hydrogel networks were calculated from the results of the swelling studies by Flory-Rehner theory. A kinetic experiment on the temperature-sensitive pure PNIPAAm hydrogel showed that the polymer network collapsed rapidly upon temperature changes across the LCST.

scholarly journals Smart Hydrogel Bilayers Prepared by Irradiation

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1753
Author(s):  
Weixian Huo ◽  
Heng An ◽  
Shuquan Chang ◽  
Shengsheng Yang ◽  
Yin Huang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Gamma Radiation ◽  
Antibacterial Properties ◽  
Cross Linking ◽  
Temperature Sensitive ◽  
Temperature Changes ◽  
Smart Hydrogel ◽  
Isopropyl Acrylamide ◽  
Hydrogel Synthesis ◽  
Potential Applications

Environment-responsive hydrogel actuators have attracted tremendous attention due to their intriguing properties. Gamma radiation has been considered as a green cross-linking process for hydrogel synthesis, as toxic cross-linking agents and initiators were not required. In this work, chitosan/agar/P(N-isopropyl acrylamide-co-acrylamide) (CS/agar/P(NIPAM-co-AM)) and CS/agar/Montmorillonite (MMT)/PNIPAM temperature-sensitive hydrogel bilayers were synthesized via gamma radiation at room temperature. The mechanical properties and temperature sensitivity of hydrogels under different agar content and irradiation doses were explored. The enhancement of the mechanical properties of the composite hydrogel can be attributed to the presence of agar and MMT. Due to the different temperature sensitivities provided by the two layers of hydrogel, they can move autonomously and act as a flexible gripper as the temperature changes. Thanks to the antibacterial properties of the hydrogel, their storage time and service life may be improved. The as prepared hydrogel bilayers have potential applications in control devices, soft robots, artificial muscles and other fields.

Green pH- and magnetic-responsive hybrid hydrogels based on poly(methacrylic acid) and Eucalyptus wood nanocellulose for controlled release of ibuprofen

Cellulose ◽  
2021 ◽  
Author(s):  
Maja D. Markovic ◽  
Sanja I. Seslija ◽  
Vukasin Dj. Ugrinovic ◽  
Matjaz Kunaver ◽  
Vesna V. Panic ◽  
...  
Keyword(s):  
Controlled Release ◽  
Methacrylic Acid ◽  
Hybrid Hydrogels ◽  
Eucalyptus Wood

Controlled release by using poly(methacrylic acid-g-ethylene glycol) hydrogels

1991 ◽  
Vol 16 (1-2) ◽  
pp. 203-214 ◽  
Author(s):  
Nikolaos A. Peppas ◽  
John Klier
Keyword(s):  
Controlled Release ◽  
Ethylene Glycol ◽  
Methacrylic Acid

scholarly journals Human Erythrocyte-Like Transformation of Synthetic Polymer Vesicles

2021 ◽  
Author(s):  
Eri Yoshida
Keyword(s):  
Methacrylic Acid ◽  
Human Erythrocyte ◽  
Bilayer Membrane ◽  
Synthetic Polymer ◽  
Butyl Methacrylate ◽  
Temperature Changes ◽  
Polymer Vesicles ◽  
Membrane Perforation ◽  
Response To Temperature ◽  
Spherical Vesicles

Abstract This paper describes that synthetic polymer vesicles undergo a human erythrocyte-like transformation in response to temperature changes. The normally biconcave discoid erythrocytes, i.e., the discocytes, are transformed into various shapes by their environmental stresses. Field emission scanning electron microscopy (FE-SEM) demonstrates that the spherical vesicles consisting of poly(methacrylic acid)-block-poly(n-butyl methacrylate-random-methacrylic acid), PMAA-b-P(BMA-r-MAA), transform into echinocyte-like crenate vesicles due to expansion by the component copolymers in being freed from the vesicle surface when heated in an aqueous methanol solution. An increase in the vesicle concentration transforms the spherical vesicles into stomatocyte-like cup-shaped vesicles via the membrane perforation or double invaginations followed by membrane coupling and fusion. Light scattering studies reveal the reversibility and repeatability of the transformations. These findings indicate that the erythrocyte transformations are attributed to the inherent property of the bilayer membrane. The polymer vesicles are helpful for a better understanding of the biomembrane.

scholarly journals Hydrogel-Silver Nanoparticle Composites for Biomedical Applications

2020 ◽  
Vol 65 (5) ◽  
pp. 446
Author(s):  
O. Nadtoka ◽  
N. Kutsevol ◽  
T. Bezugla ◽  
P. Virych ◽  
A. Naumenko
Keyword(s):  
Silver Nanoparticle ◽  
Biomedical Applications ◽  
Polymer Network ◽  
Cross Linking ◽  
Polyacrylamide Hydrogels ◽  
Photochemical Generation ◽  
Vis Spectroscopy ◽  
Swelling Capacity ◽  
Swelling Studies ◽  
Nanoparticle Composites

Polyacrylamide and dextran-graft-polyacrylamide hydrogels are prepared and used as nanoreactors and networks for the synthesis of silver nanoparticles (AgNPs). Photochemical generation of AgNPs is carried out under UV-irradiation of Ag+ ions in swollen hydrogels of different cross-linking densities. The obtained hydrogels and hydrogel/AgNPs composites are characterized by TEM, FTIR, and UV–Vis spectroscopy. Swelling studies have shown a relationship between the structure of the hydrogels and their ability to swell. It is shown that the presence of AgNPs in the polymer network leads to a decrease of the swelling capacity. An increase in the cross-linking density leads to an expansion of the AgNPs size distribution for both types of hydrogels. All synthesized hydrogel-silver nanoparticle composites have shown a high activity in the growth retardation of Staphylococcus aureus microorganisms.

Synthesis and characterization of interpenetrating polymer network based on sodium alginate and methacrylic acid and potential application for immobilization of TiO2 nanoparticles

2015 ◽  
Vol 55 (11) ◽  
pp. 2511-2518 ◽  
Author(s):  
Marija Lučić Škorić ◽  
Nedeljko Milosavljević ◽  
Maja Radetić ◽  
Zoran Šaponjić ◽  
Marija Radoičić ◽  
...  
Keyword(s):  
Tio2 Nanoparticles ◽  
Sodium Alginate ◽  
Methacrylic Acid ◽  
Potential Application ◽  
Polymer Network ◽  
Interpenetrating Polymer Network ◽  
Synthesis And Characterization

Encapsulation and In Vitro Controlled Release of Doxycycline in Temperature-Sensitive Hydrogel Composed of Polyethyleneglycol–polypeptide (L-Alanine-co-L-Aspartate)

2021 ◽  
Vol 49 ◽  
pp. 119-129
Author(s):  
Shamo Zokhrab Tapdiqov
Keyword(s):  
Controlled Release ◽  
Correlation Coefficients ◽  
Zero Order ◽  
Temperature Sensitive ◽  
Poly Ethylene Glycol ◽  
Drug Delivery Carrier ◽  
Ft Ir ◽  
Poly Ethylene ◽  
Potential Use

Doxycycline was loaded with synthesized micelles composed of methyl Poly (ethylene glycol-block-poly (L-alanine–co–L-aspartate), or mPEG–Ala–Asp, and then characterized as a drug delivery carrier. The synthesis of the temperature-sensitive mPEG–Ala–Asp block copolymer was carried out by two-step ring-opening polymerization: firstly, the mPEG reacts with L-alanine N-carboxylic anhydride, and secondly the resulting mPEG–Ala reacts with benzyl aspartate N-carboxylic anhydride. The molecular structure of the copolymers obtained was determined by FT-IR and NMR spectroscopy methods and the micelles were characterized by SEM, TEM and DLS, respectively. The controlled release of Dox from hydrogel in the presence of PBS (8 to 9% by weight) lasts 6 to 7 days exhibiting stable release rates. The drug release mechanisms were studied: Higuchi and zero order models. The results and correlation coefficients applied to the Higuchi and zero-order models. The findings show the potential use of mPEG–Ala–Asp as an effective depot matrix to deliver anthracycline class drugs.

Temperature Sensitivity of Intracellular and Extracellular Soil Enzyme Activities

2021 ◽  
Author(s):  
Adetunji Alex Adekanmbi ◽  
Laurence Dale ◽  
Liz Shaw ◽  
Tom Sizmur
Keyword(s):  
Enzyme Activity ◽  
Soil Temperature ◽  
Temperature Sensitivity ◽  
Extracellular Enzymes ◽  
Extracellular Enzyme ◽  
Daily Maximum ◽  
Temperature Sensitive ◽  
Intracellular Enzyme ◽  
Temperature Changes ◽  
Som Decomposition

<p>Predicting the pattern of soil organic matter (SOM) decomposition as a feedback to climate change, via release of CO<sub>2</sub>, is extremely complex and has received much attention. However, investigations often do not differentiate between the extracellular and intracellular processes involved and work is needed to identify their relative temperature sensitivities. Samples were collected from a grassland soil at Sonning, UK with average daily maximum and minimum soil temperature of 15 °C and 5 °C. We measured potential activities of β-glucosidase (BG) and chitinase (NAG) (extracellular enzymes) and glucose-induced CO<sub>2 </sub>respiration (intracellular enzymes) at a range of assay temperatures (5 °C, 15 °C, 26 °C, 37<sup>  </sup>°C, and 45 °C). The temperature coefficient Q<sub>10</sub> (the increase in enzyme activity that occurs after a 10 °C increase in soil temperature) was calculated to assess the temperature sensitivity of intracellular and extracellular enzymes activities. Between 5 °C and 15 °C intracellular and extracellular enzyme activities had equal temperature sensitivity, but between 15 °C and 26°C intracellular enzyme activity was more temperature sensitive than extracellular enzyme activity and between 26 °C and 37 °C extracellular enzyme activity was more temperature sensitive than intracellular enzyme activity. This result implies that extracellular depolymerisation of higher molecular weight organic compounds is more sensitive to temperature changes at higher temperatures (e.g. changes to daily maximum summer temperature) but the intracellular respiration of the generated monomers is more sensitive to temperature changes at moderate temperatures (e.g. changes to daily mean summer temperature). We therefore conclude that the extracellular and intracellular steps of SOM mineralisation are not equally sensitive to changes in soil temperature. The finding is important because we have observed greater increases in average daily minimum temperatures than average daily mean or maximum temperatures due to increased cloud cover and sulphate aerosol emission. Accounting for this asymmetrical global warming may reduce the importance of extracellular depolymerisation and increase the importance of intracellular catalytic activities as the rate limiting step of SOM decomposition.</p>

Controlled release of insulin from pH/temperature-sensitive injectable pentablock copolymer hydrogel

2009 ◽  
Vol 137 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Dai Phu Huynh ◽  
Guang Jin Im ◽  
Su Young Chae ◽  
Kang Choon Lee ◽  
Doo Sung Lee
Keyword(s):  
Controlled Release ◽  
Temperature Sensitive ◽  
Copolymer Hydrogel ◽  
Pentablock Copolymer
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