Squeezing hydrogels for controlled oral drug delivery

Gutowska, Anna; Bark, Jong Seok; Kwon, Ick Chan; Bae, You Han; Cha, Yong-Jun; Kim, Sung Wan

doi:10.1016/s0168-3659(97)00041-2

Cited by 175 publications

(94 citation statements)

References 18 publications

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“…26,27 In the alkaline solution, COO À ions and H + ions were dissociated, and then the gel swelled because of H + ion diffusion and electrostatic repulsion. 25,26 The shape change of the gel was caused by the electrostatic repulsion between carboxylate anions in the hydrogels.…”

Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

“…In the case of calcium alginate gels, the Ca 2+ ions, which were used for cross-linking, and H 3 O + ions, which were generated in the alginate gels, moved toward the cathode, 26,27,30 and the water from the outside entered into the alginate gels. Therefore, the calcium alginate gel near the anode decreased in size, and the calcium alginate gel near the cathode increased in size.…”

Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

“…The shrinkage of the hydrogels under applied voltage was due to electroosmosis and electrophoresis. 26,27,30 In the case of using the 100 mM CaCl 2 solution instead of distilled water, Figure 9 shows the volume alteration ratio of the composite gels with electrical stimulus over time. The volume of the gels before applying the voltage was defined as 100%, and the volume alteration ratio of composite gels after applying the voltage was calculated.…”

Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

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Evaluation of the stimulus response of hydroxyapatite/ calcium alginate composite gels

Obara

Yamauchi

Tsubokawa

2010

Polym J

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Stimuli-responsive gels have been actively studied and applied to a variety of devices such as drug carriers, artificial muscles and actuators. In this research study, calcium alginate gels containing hydroxyapatite were prepared in one step by adding a diammonium hydrogenphosphate-1% alginate solution to a calcium chloride solution and evaluated for pH dependence and electrochemical properties as stimuli-responsive gels. When the composite gel was immersed in a solution of pH 2-10 or subjected to an applied voltage, the composite gel with a high content of hydroxyapatite tended to maintain its volume. The composite gels immersed in a pH indicator solution changed color with an applied voltage. As a result, it was revealed that alteration of the pH of composite gels occurred by electro-osmosis and electrophoresis. Swelling and shrinking of the composite gels were controlled by the external stimuli of pH, voltage and the content of hydroxyapatite; therefore, it is proposed that composite gels would be good bone-filling material having the function of drug carriers.

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Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

Section: Evaluation Of the Stimulus Response S Obara Et Almentioning

confidence: 99%

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Evaluation of the stimulus response of hydroxyapatite/ calcium alginate composite gels

Obara

Yamauchi

Tsubokawa

2010

Polym J

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“…Insulin by virtue of its action reduces blood glucose level and consequently gluconic acid level also gets decreased and system turns to the deswelling mode thereby decreasing the insulin release. Examples of the pH sensitive polymers include N, N-dimethylaminoethyl methacrylate, chitosan, polyol etc [62,63].…”

Section: Chemical Stimuli Induced Pulsatile Systems I Glucose-responmentioning

confidence: 99%

Recent trends in pulsatile drug delivery systems - A review.

Sharma¹,

Srikanth²,

Uhumwangho³

et al. 2010

Int j Drug delivery

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The purpose of writing this review on pulsatile drug delivery systems (PDDS) is to compile the recent literatures with special focus on the different types and approaches involved in the development of the formulation. PDDS are gaining importance in the field of pharmaceutical technology as these systems deliver the right dose at specific time at a specific site. Some of the disease conditions wherein PDDS are promising include duodenal ulcer, cardiovascular diseases, arthritis, asthma, diabetes, neurological disorder, cancer, hypertension and hypercholesterolemia. PDDS can be classified into time controlled systems wherein the drug release is controlled primarily by the delivery system, stimuli induced PDDS in which release is controlled by the stimuli, such as the pH or enzymes present in the intestinal tract or enzymes present in the drug delivery system and externally regulated system where release is programmed by external stimuli like magnetism, ultrasound, electrical effect and irradiation. This review also summarizes some current PDDS already available in the market. These systems are useful to several problems encountered during the development of a pharmaceutical dosage form.

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“…To mimic this special feature of enzymes, we designed a polymer gel consisting of two species of monomers, each having a specific role. The major component allows the gel to reversibly swell and shrink in response to changes in environmental parameters such as temperature and solvent (1)(2)(3)(4)(5)(6)(7)(8)(9). On swelling and shrinking, the local density of the hydrophobic moiety changes and the affinity to substrate molecules is altered accordingly.…”

mentioning

confidence: 99%

Gel catalysts that switch on and off

Wang

Kuroda

Enoki

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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We report development of a polymer gel with a catalytic activity that can be switched on and off when the solvent composition is changed. The gel consists of two species of monomers. The major component, N-isopropylacrylamide, makes the gel swell and shrink in response to a change in composition of ethanol͞water mixtures. The minor component, vinylimidazole, which is capable of catalysis, is copolymerized into the gel network. The reaction rate for catalytic hydrolysis of p-nitrophenyl caprylate was small when the gel was swollen. In contrast, when the gel was shrunken, the reaction rate increased 5 times. The activity changes discontinuously as a function of solvent composition, thus the catalysis can be switched on and off by an infinitesimal change in solvent composition. The kinetics of catalysis by the gel in the shrunken state is well described by the Michaelis-Menten formula, indicating that the absorption of the substrate by the hydrophobic environment created by the N-isopropylacrylamide polymer in the shrunken gel is responsible for enhancement of catalytic activity. In the swollen state, the rate vs. active site concentration is linear, indicating that the substrate absorption is not a primary factor determining the kinetics. Catalytic activity of the gel is studied for substrates with various alkyl chain lengths; of those studied the switching effect is most pronounced for p-nitrophenyl caprylate.N atural enzymes catalyze chemical reactions, and equally importantly, regulate them by reversibly and repeatedly switching on and off the catalytic activities. To mimic this special feature of enzymes, we designed a polymer gel consisting of two species of monomers, each having a specific role. The major component allows the gel to reversibly swell and shrink in response to changes in environmental parameters such as temperature and solvent (1-9). On swelling and shrinking, the local density of the hydrophobic moiety changes and the affinity to substrate molecules is altered accordingly. The minor component capable of catalysis of substrate decomposition is copolymerized with the responsive monomers into the gel network. The catalytic activity of the gel is expected to be switched on and off as the substrate is reversibly bound and released during the cycle of gel swelling and shrinking. Materials and MethodsTo demonstrate the feasibility of the idea, we chose hydrolysis of p-nitrophenyl esters with different alkyl chain lengths as the chemical reaction to examine (Fig. 1a). This reaction is known to be catalyzed by 4(5)-vinylimidazole (10). We, therefore, used it as the minor catalytic monomer component of the gel (Fig. 1b). As the major component, we chose the widely used hydrophobic monomer N-isopropylacrylamide (NIPA). The substrate and gel monomer components were selected because (i) the substrate and one of the hydrolysis products, p-nitrophenol, were easily detected by using UV spectroscopy; (ii) the NIPA gel underwent a discontinuous swelling͞shrinking transition in response to changes in environmen...

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Squeezing hydrogels for controlled oral drug delivery

Cited by 175 publications

References 18 publications

Evaluation of the stimulus response of hydroxyapatite/ calcium alginate composite gels

Evaluation of the stimulus response of hydroxyapatite/ calcium alginate composite gels

Recent trends in pulsatile drug delivery systems - A review.

Gel catalysts that switch on and off

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