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Controlled release

About: Controlled release is a(n) research topic. Over the lifetime, 20521 publication(s) have been published within this topic receiving 563480 citation(s).

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Journal ArticleDOI
Abstract: The simple exponential relation Mt/M∞ = ktn is introduced to describe the general solute release behavior of controlled release polymeric devices, where Mt/M∞ is the fractional solute release, t is the release time, k is a constant, and n is the diffusional exponent characteristic of the release mechanism. It is shown that this equation can adequately describe the release of drugs or other solutes from slabs, spheres, cylinders and discs (tablets), regardless of the release mechanism. It is shown that in cases of pure Fickian release the exponent n has the limiting values of 0.50, 0.45 and 0.43 for release from slabs, cylinders and spheres, respectively. For tablets, and depending on the aspect ratio, i.e., the ratio of diameter to thickness, the Fickian diffusion mechanism is described by 0.43

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2,892 citations


Journal ArticleDOI
TL;DR: An MCM-41 type mesoporous silica nanosphere-based controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN Mesoporous framework.

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Abstract: An MCM-41 type mesoporous silica nanosphere-based (MSN) controlled-release delivery system has been synthesized and characterized using surface-derivatized cadmium sulfide (CdS) nanocrystals as chemically removable caps to encapsulate several pharmaceutical drug molecules and neurotransmitters inside the organically functionalized MSN mesoporous framework. We studied the stimuli-responsive release profiles of vancomycin- and adenosine triphosphate (ATP)-loaded MSN delivery systems by using disulfide bond-reducing molecules, such as dithiothreitol (DTT) and mercaptoethanol (ME), as release triggers. The biocompatibility and delivery efficiency of the MSN system with neuroglial cells (astrocytes) in vitro were demonstrated. In contrast to many current delivery systems, the molecules of interest were encapsulated inside the porous framework of the MSN not by adsorption or sol−gel types of entrapment but by capping the openings of the mesoporous channels with size-defined CdS nanoparticles to physically block...

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1,537 citations


Journal ArticleDOI
TL;DR: By selection of the type of alginate and coating agent, the pore size, degradation rate, and ultimately release kinetics can be controlled.

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Abstract: There are a variety of both natural and synthetic polymeric systems that have been investigated for the controlled release of proteins. Many of the procedures employed to incorporate proteins into a polymeric matrix can be harsh and often cause denaturation of the active agent. Alginate, a naturally occurring biopolymer extracted from brown algae (kelp), has several unique properties that have enabled it to be used as a matrix for the entrapment and/or delivery of a variety of biological agents. Alginate polymers are a family of linear unbranched polysaccharides which contain varying amounts of 1,4'-linked beta-D-mannuronic acid and alpha-L-guluronic acid residues. The residues may vary widely in composition and sequence and are arranged in a pattern of blocks along the chain. Alginate can be ionically crosslinked by the addition of divalent cations in aqueous solution. The relatively mild gelation process has enabled not only proteins, but cells and DNA to be incorporated into alginate matrices with retention of full biological activity. Furthermore, by selection of the type of alginate and coating agent, the pore size, degradation rate, and ultimately release kinetics can be controlled. Gels of different morphologies can be prepared including large block matrices, large beads (>1 mm in diameter) and microbeads (<0.2 mm in diameter). In situ gelling systems have also been made by the application of alginate to the cornea, or on the surfaces of wounds. Alginate is a bioadhesive polymer which can be advantageous for the site specific delivery to mucosal tissues. All of these properties, in addition to the nonimmunogenicity of alginate, have led to an increased use of this polymer as a protein delivery system. This review will discuss the chemistry of alginate, its gelation mechanisms, and the physical properties of alginate gels. Emphasis will be placed on applications in which biomolecules have been incorporated into and released from alginate systems.

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1,512 citations


Journal ArticleDOI
TL;DR: Recent research progress on the design of functional MSN materials with various mechanisms of controlled release, along with the ability to achieve zero release in the absence of stimuli, and the introduction of new characteristics to enable the use of nonselective molecules as screens for the construction of highly selective sensor systems are reviewed.

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Abstract: Recent advancements in morphology control and surface functionalization of mesoporous silica nanoparticles (MSNs) have enhanced the biocompatibility of these materials with high surface areas and pore volumes. Several recent reports have demonstrated that the MSNs can be efficiently internalized by animal and plant cells. The functionalization of MSNs with organic moieties or other nanostructures brings controlled release and molecular recognition capabilities to these mesoporous materials for drug/gene delivery and sensing applications, respectively. Herein, we review recent research progress on the design of functional MSN materials with various mechanisms of controlled release, along with the ability to achieve zero release in the absence of stimuli, and the introduction of new characteristics to enable the use of nonselective molecules as screens for the construction of highly selective sensor systems.

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1,506 citations


Journal ArticleDOI
TL;DR: This review highlights the use of hydrogels (a class of polymeric systems) in controlled drug delivery, and their application in stimuli- responsive, especially pH-responsive, drug release.

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Abstract: Hydrogels are one of the upcoming classes of polymer-based controlled-release drug delivery systems. Besides exhibiting swelling-controlled drug release, hydrogels also show stimuli-responsive changes in their structural network and hence, the drug release. Because of large variations in physiological pH at various body sites in normal as well as pathological conditions, pH-responsive polymeric networks have been extensively studied. This review highlights the use of hydrogels (a class of polymeric systems) in controlled drug delivery, and their application in stimuli-responsive, especially pH-responsive, drug release.

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1,453 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202228
2021933
2020997
20191,043
20181,062
20171,131

Top Attributes

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Topic's top 5 most impactful authors

Robert Langer

106 papers, 12.6K citations

Tejraj M. Aminabhavi

62 papers, 4K citations

Juergen Siepmann

44 papers, 2.6K citations

Nicholas A. Peppas

26 papers, 7K citations

Florence Siepmann

24 papers, 1K citations