Biological Super Glue of Mussels Synthesized for Cancer Drug Delivery

When it comes to sticking power under wet conditions, marine mussels are hard to beat. They can adhere to virtually all inorganic and organic surfaces, sustaining their tenacious bonds in saltwater, including turbulent tidal environments.

Messersmith, a professor of biomedical engineering at Northwestern's McCormick School of Engineering and Applied Science, is creating new materials that mimic mussel adhesive proteins for three medical applications: sealants for fetal membrane repair, self-setting antibacterial hydrogels, and polymers for cancer drug delivery and thermal destruction of cancer cells.

"Mussel adhesion is a remarkable process involving secretion of liquid protein glue that hardens rapidly into a solid, water-resistant adhesive," Messersmith said. "Several aspects of this process inspire our development of synthetic materials for practical applications. An unusually compelling opportunity for translation of mussel-adhesion concepts is in the repair or reconstruction of tissues in the human body, where water is ubiquitous and its presence represents a challenge for achieving desired outcomes."

One of Messersmith's polymer designs for cancer drug delivery forms pH-sensitive drug delivery vehicles that are stable and inactive in the bloodstream but are activated in the acidic tumor environment, which liberates the drug. A second design involves modifying the surface of gold nanorods with a mussel-inspired polymer coating, which helps the nanorods target cancer cells. Once at the target, the nanorods are irradiated with near-infrared light to produce highly localized heating that thermally destroys cancer cells.

"Certainly spider silk is the darling of the biomaterials world because of its high strength. But the spotlight is getting brighter for mussels because they make strong, tough, durable attachments that can set underwater," Emily Carrington, a University of Washington professor of biology said.

"What biologists can contribute to the materials science arena is an appreciation of biodiversity," she said. "Mussels live in all kinds of habitats. Some species are experts at gluing onto sea grass, some to other shells, some even adhere in the harsh conditions of hydrothermal vents. They each may have different genes that code for different proteins so the adhesive will be a little different and worth exploring."

Mussels form attachments to rocks, fellow mussels and other surfaces with what's called the byssus, a mass of golden-colored threads or filaments. Although each strand is only three to 10 times the width of a human hair, the threads are extraordinarily strong and stretchy, she says.