Hydrogel control
ChemSci Pick of the Week
Stimuli-responsive hydrogels could help in the search for controlled methods of delivering cancer drugs.
Many of us will think of jelly as a favourite childhood party food, but it actually belongs to a class of materials with widespread scientific applications. Jelly is a hydrogel – a fascinating class of material that has many of the properties of a solid but is in fact mainly made up of liquid.
The structure of a hydrogel depends on a three-dimensional network of cross-linked polymers. The spaces in the network are filled with water, held in place by surface tension effects. Other common uses for hydrogels include in disposable nappies, contact lenses, breast implants and glue.
Some hydrogels are stimuli-responsive – that is they change their structure or properties in response to external stimuli such as light, magnetic fields, heat or changes in pH. These types of hydrogels are attracting growing interest for medical applications – including tissue engineering and controlled drug release.
Dr Itamar Willner and a team of scientists from China and Israel have developed a new class of hydrogel that alters its stiffness in response to light stimuli. This has a number of applications, some of which have been demonstrated in their latest paper.
The first application is as a capsule for delivering cancer drugs within the body. The gel is loaded with the drug, and when it is stiff the drug is retained in the structure. When, however the gel is less stiff the drug is able to leave the structure.
Dr Willner explains: "The triggered transition of the hydrogel yields the lower stiffness hydrogel that allows the release of the drug. By the application of a counter trigger (switching the light to another wavelength), the stiffer hydrogel is regenerated, and the release of the drug is inhibited. By the cyclic transition of the hydrogel between low stiffness and high stiffness, the release of the drug is switched 'ON' and 'OFF', thus allowing a dose-controlled drug treatment."
Being able to release drugs in a targeted, controlled way could help minimise the harmful side-effects of many cancer treatments.
The hydrogels can also 'self-heal', in response to external triggers, meaning that they could be used to repair wounds – acting as a glue to hold broken tissue together until is it able to knit back together.
This article is free to read in our open access, flagship journal Chemical Science: Itamar Willner et al., Chem. Sci., 2018, Advance Article. DOI: 10.1039/C8SC04292F. You can access all of our ChemSci Picks in this article collection.
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