A group of University of Illinois bioengineers have found a way to strongly adhere hydrogels to hydrophobic silicone substrates, an innovation that provides a valuable new tool for microscale biotechnology.

Microscale biotechnologies, including cell culture platforms and biochips, have important applications in genomics, tissue engineering, and many other areas of biology.  Silicone polymers are often used as a component material in these technologies because of their advantageous properties: silicones are inert, elastic, biocompatible, and easy to work with.

One major drawback of this type of material in biological applications is that surfaces formed by silicones are extremely hydrophobic.  These surfaces therefore prohibit easy flow of aqueous solutions and prevent the binding of some biomolecules, while promoting undesired binding of others.  Chemical modifications or coatings can be used to make the surfaces hydrophilic, but the results produced by these treatments are temporary.

The group worked to develop a method to permanently modify a silicone polymer surface. Kong’s group sought a way to “glue” an alginate hydrogel, a water-absorbing substance also used in food and medical industries, to a surface formed by polydimethylsiloxane (PDMS), a silicone polymer that is a common material in microscale biotechnologies.

The solution, developed by first author Chaenyung Cha, Kong, and others, was to develop a multi-step protocol to covalently link alginate, the polysaccharide that is also a component of the hydrogel, to a PDMS surface.  The resulting alginate-PDMS can then participate in a cross-linking reaction that forms an alginate hydrogel.  Tests performed as part of the study showed that the attachment of hydrogel to PDMS formed by this process is stable for several months, can tolerate bending and repeated stretching, and is not degraded by aqueous solutions.  The hydrogel is more hydrophilic than the surfaces produced by previously developed treatments, and its physical properties can be easily controlled by modifying the crosslinking reaction used in its formation.

The study also explored several practical applications of the hydrogel-PDMS surface.  Fibroblasts, a type of cells found in connective tissue, were first cultured on a hydrogel-PDMS surface, and then chronically exposed to repeated stretching. This type of manipulation would not be possible with less elastic cell culture substrates, and has value for researchers studying the effects of mechanical stress on living cells inside the body.

Another experiment showed that the hydrogel could be successfully and stably synthesized within the channels of a microfluidic device.  “This method will greatly advance quality of cell culture platforms and microfluidic devices.  It will further benefit design of novel drug delivery systems and cell transplantation devices,” Kong said.

This story is reprinted from material from The University of Illinois, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.