Preparation of poly(N-isopropylacrylamide) emulsion gels and their drug release behaviors

Tokuyama, Hideaki; Kato, Yoshitaka

doi:10.1016/j.colsurfb.2008.08.003

Cited by 40 publications

(25 citation statements)

References 18 publications

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“…The release of drugs by thermal cycling was performed for most of thermoresponsive hydrogels at temperatures far below and above the LCST of the linear polymer (i.e., 25 and 40ºC) [26,27]. The reason is to be sure that these temperatures are also situated below and above the VPTT of the hydrogel, which in fact, is not known.…”

Section: Drug Loading and Release Studiesmentioning

confidence: 99%

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

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Abstract. One of the most subtle problem in the characterization of thermoresponsive polymers is the evaluation of the relationship between the lower critical solution temperature (LCST) of the linear polymer and the volume phase transition temperature (VPTT) of the corresponding hydrogel. Here, the LCST and the onset temperature of linear poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) has been determined under pseudo-physiological conditions by cloud point (CP) measurements and by microcalorimetric analysis. The LCSTs, as well as the onset temperatures, determined by the CP method, decrease with increasing the concentration of the polymer solution. On the contrary, microcalorimetric analyses give almost the same values for LCSTs and the onset temperatures regardless of polymer concentration. The VPTT of the hydrogel, determined by the blue dextran method, was found to be closely similar to the LCST of the concentrated polymer solution (10%, w/v), determined by the CP method. In fact, the hydrogel could be considered as a concentrated polymer solution whose concentration could be related to the amount of water retained by the hydrogel. Hydrogel microspheres have been also reported to release diclofenac, a drug model system, in a pulsating way at temperatures slightly below and above the VPTT.

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Section: Drug Loading and Release Studiesmentioning

confidence: 99%

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

View full text Add to dashboard Cite

show abstract

“…Cross-linked hydrogel materials have been used in many applications such as separation membranes, biosensors, valves, artificial muscle [15], [16], drug delivery devices [17], super-adsorbent nano-composites [18] and actuators for optics and fluidics UBC a place of mind fil THE UNIVERSITY OF BRITISH COLUMBIA [19]. Hydrogels are very soft and wet material with low sliding friction [20] and high solute permeability [21].…”

Section: Introductionmentioning

confidence: 99%

Transparent and conformal 'piezoionic' touch sensor

Sarwar

Dobashi

Glitz³

et al. 2015

SPIE Proceedings

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A polyurethane hydrogel based touch sensor with high transparency and conformability is demonstrated. Polyurethane hydrogels swollen with various electrolytes were compressed at a pressure of 30 kPa, simulating a fingertap on a conventional touch screen device. Unlike ionic polymer metal composite and conducting polymer trilayer sensors, where electrodes render the sensors opaque and relatively rigid, the electrodes used in this work are metal wires or strips, separated from each other by regions of transparent film, enabling transparency and compliance. The voltages and currents observed when the perturbation is above one electrode are on the order of 10(-2) V and 10(-7) A, relative to a second electrode that is approximately 1 cm away. The sign of voltage and current signals detected from perturbations made between electrodes is determined by relative proximity to each electrode, and the magnitude appears to decrease with increasing distance from the electrodes. These observations suggest that it may be possible to discriminate the location of touch based on signals transmitted to the edges of an ionically conductive film. A model to describe the inhomogeneous ionic distribution and predict the resultant voltage and current is presented to qualitatively explain the sensing, based on the Donnan potential. ABSTRACTA polyurethane hydrogel based touch sensor with high transparency and conformability is demonstrated. Polyurethane hydrogels swollen with various electrolytes were compressed at a pressure of 30 kPa, simulating a fingertap on a conventional touch screen device. Unlike ionic polymer metal composite and conducting polymer trilayer sensors, where electrodes render the sensors opaque and relatively rigid, the electrodes used in this work are metal wires or strips, separated from each other by regions of transparent film, enabling transparency and compliance. The voltages and currents observed when the perturbation is above one electrode are on the order of 10 -2 V and 10 -7 A, relative to a second electrode that is approximately 1 cm away. The sign of voltage and current signals detected from perturbations made between electrodes is determined by relative proximity to each electrode, and the magnitude appears to decrease with increasing distance from the electrodes. These observations suggest that it may be possible to discriminate the location of touch based on signals transmitted to the edges of an ionically conductive film. A model to describe the inhomogeneous ionic distribution and predict the resultant voltage and current is presented to qualitatively explain the sensing, based on the Donnan potential.

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“…In recent years, temperature sensitive self-assembled amphiphilic and double-hydrophilic polymeric micelles have been extensively investigated for their potential applications in gene transfection, drug delivery systems, chemosensors/biosensors, cell adhesion, protein-ligand recognition and molecular separation [1][2][3][4][5][6][7][8][9][10][11]. Hydrophilic-hydrophilic copolymers (also called doublehydrophilic copolymers; DHCs) comprise combinations of two or more water-soluble monomers that have different chemical properties.…”

Section: Introductionmentioning

confidence: 99%

Fabrication and aggregation of thermoresponsive glucose-functionalized double hydrophilic copolymers

Lou

Zhang

Williams

et al. 2013

Colloids and Surfaces B: Biointerfaces

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Preparation of poly(N-isopropylacrylamide) emulsion gels and their drug release behaviors

Cited by 40 publications

References 18 publications

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Transparent and conformal 'piezoionic' touch sensor

Fabrication and aggregation of thermoresponsive glucose-functionalized double hydrophilic copolymers

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