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Hydrogels

Notes

From *09/30/2014 through 2/7/2012

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Gels

Hydrogel Applications

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Notes

1. “Hydrogel (also called aquagel) is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. Hydrogels are highly absorbent (they can contain over 99.9% water) natural or synthetic polymers. Hydrogels also possess a degree of flexibility very similar to natural tissue, due to their significant water content. Common uses for hydrogels include

 currently used as scaffolds in tissue engineering. When used as scaffolds, hydrogels may contain human cells to repair tissue.

 hydrogel-coated wells have been used for cell culture[2]

 environmentally sensitive hydrogels which are also known as 'Smart Gels' or 'Intelligent Gels'. These hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change.

 as sustained-release drug delivery systems.

 provide absorption, desloughing and debriding of necrotic and fibrotic tissue.

 hydrogels that are responsive to specific molecules, such as glucose or antigens, can be used as biosensors, as well as in DDS.

 used in disposable diapers where they absorb urine, or in sanitary napkins

 contact lenses (silicone hydrogels, polyacrylamides)

 EEG and ECG medical electrodes using hydrogels composed of cross-linked polymers (polyethylene oxide, polyAMPS and polyvinylpyrrolidone)

 water gel explosives

 rectal drug delivery and diagnosis

Other, less common uses include

 breast implants

 now used in glue.

 granules for holding soil moisture in arid areas

 dressings for healing of burn or other hard-to-heal wounds. Wound gels are excellent for helping to create or maintain a moist environment.

 reservoirs in topical drug delivery; particularly ionic drugs, delivered by iontophoresis (see ion exchange resin)

Common ingredients are e.g. polyvinyl alcohol, sodium polyacrylate, acrylate polymers and copolymers with an abundance of hydrophilic groups.

Natural hydrogel materials are being investigated for tissue engineering; these materials include agarose, methylcellulose, hyaluronan, and other naturally derived polymers.”

(Wikipedia, Hydrogels, 5/1/2012)

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2. “Hydrogels are typically water-containing gels (i.e. shape-stable, easily deformable, disperse systems rich in liquids and gases and comprising at least two components which usually consists of a colloidally divided solid having long or highly branched particles and a liquid (usually water) as a dispersion medium) based on hydrophilic but water-insoluble polymers, in the form of three-dimensional networks. These networks swell up in water to an equilibrium volume while substantially retaining their shape. Network formation takes place predominantly via chemical linking of the individual chains of polymer, but is also possible physically through electrostatic, hydrophobic or dipole-dipole interactions between individual segments of the polymer chains. Desired properties for the hydrogels can be specifically set via the choice of monomers used for polymer construction, the type of crosslinking and the crosslink density. Hydrogels are typically based on poly(meth)acrylic acids, poly(meth)acrylates, polyurethanes, polyvinylpyrrolidone or polyvinyl alcohol. They are generally highly compatible with living tissues and therefore are often used as biomaterials, and particularly in the biomedical and pharmaceutical sector.”

[Kohler et al, US Patent 8,133,509 (3/13/2012)]

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3. Hydrogels are hydrophilic polymeric networks which can absorb and retain large amounts of water.  Hydrogels are useful in controlled release systems for drug delivery (Kumar, 2002), tissue repair, tissue engineering and as surgical sealants and adhesives. Although great progress in medical applications of hydrogels has been made, it remains challenging to develop cross-linking methods that satisfy the demanding biological and handling requirements for medical treatment. Accordingly, there is a long-felt, unmet need for biocompatible hydrogels capable of deployment by minimally invasive methods and solidification under physiological conditions.

Messersmith, Hu and Su of Northwestern University developed biocompatible macromonomers, hydrogels, using a thioester readily reacts with a N-terminal thiol (cysteine) through transesterification and rearrangement to form an amide bond through a five-member ring intermediate. (Chemical Ligation)

8,841,408  (9/23/2014
Macromonomers and hydrogel systems using native chemical ligation, and their methods of preparation

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These pages list the links as they are found.  Some will abstracted and added to Maro Topics. (RDC 2/7/2012)

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Roger D. Corneliussen
Editor
www.maropolymeronline.com

Maro Polymer Links
Tel: 610 363 9920
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E-Mail: cornelrd@bee.net  

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Copyright 2012 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
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* Date of latest addition; date of first entry is 5/1/2012.

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