Biomedical Engineering Blog

Biomedical Engineering

The Biomedical Engineering blog is the place for conversation and discussion about topics related to engineering principles of the medical field. Here, you'll find everything from discussions about emerging medical technologies to advances in medical research. The blog's owner, Chelsey H, is a graduate of Rensselaer Polytechnic Institute (RPI) with a degree in Biomedical Engineering.

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Sponge For Science

Posted November 28, 2012 11:45 AM by Chelsey H

You know those sponges that little kids use to finger paint? That's what a new drug delivery system developed by bioengineers at Harvard and Caltech looks like. The gel-based sponges can be molded into any shape (including stars and hearts) and injected into the body to deliver drugs or serve as a support structure for the surrounding tissue.

Medical sponges. Image Credit: Sidi Bencherif

The sponges are made primarily of alginate, a gel made from algae. Alginate is a salt of alginic acid which is extracted from marine kelp. It is commonly used in foam, cloth, and gauze for absorbent surgical dressings. Soluble alginates, such as those of sodium, potassium, or magnesium, form a viscous sol that is changed into a gel by a chemical reaction with compounds such as calcium sulfate. Previously, alginate in the gel state has been used to take dental impressions, but scientists have created a new sponge-like gel with a freezing process called cryogelation. Pure ice crystals form as the water in the alginate solution starts to freeze. This makes the surrounding gel more concentrated as it sets. Later on, the ice crystals melt, leaving behind a network of pores. The cryogelation process has been calibrated so that a strong and extremely compressible gel is formed.

The gel-based sponge can be molded into any shape and compressed to a fraction of its size. This means that the sponge can be delivered via injection with a small-bore needle. Once injected, the sponge resumes its original shape and can deliver the drug before safely degrading in the body.

The potential applications for this discovery are vast. The 3D structure could be used to influence the surrounding cells and promote tissue formation. If a tissue has been lost or is deficient, the sponge could provide bulking for the area, as well as the transplant of stem cells or immune cells for immotherapy. The sponge can hold large and small proteins for gradual release as the biocompatible matric starts to break down. The new sponge can flow to and fill in whatever space is available. The children sponges - see the confusion? Image Credit: Mega Brands

"Furthermore, the ability of these materials to reassume specific, pre-defined shapes after injection is likely to be useful in applications such as tissue patches where one desires a patch of a specific size and shape, and when one desires to fill a large defect site with multiple smaller objects. These could pack in such a manner to leave voids that enhance diffusional transport to and from the objects and the host, and promote vascularization around each object." says Bencherif, lead author and postdoctoral research associate at SEAA at the Wyss Institute of Harvard. Image Credit: Sidi Bencherif

The next step for this discovery is to perfect the degradation rate of the scaffold so that it breaks down at the same rate at which newly grown tissue replaces it. Harvard is filing the paperwork so this might be something we all see in the OR very soon.


Injectable sponge delivers drugs, cells, and structure

Injectable Sponges Can Expand Inside The Body To Deliver Drugs


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