Now's the time to dust off the Halloween decorations and adorn the house with all sorts of spooky things, including the classic polyester spider webs. ACS Nano have created their own version of fake spider silk, but it contains proteins and heals wounds rather than spreading ghosts in corridors. The artificial silk is so strong it can be woven into bandages that help treat joint injuries and skin wounds in mice.
Spider silk is one of the strongest substances on Earth, technically stronger than steel for a material of this size. However, it is difficult to obtain – spiders are highly territorial (and cannibalistic!), so they should not reproduce like silkworms, which has forced scientists to turn to artificial alternatives. Teaching microorganisms to produce spider silk proteins through genetic engineering is one such option, but this has proven challenging as the proteins tend to clump together, reducing silk yield. So, Bingbing Gao and his colleagues wanted to modify the natural protein sequence to design an easily spinnable, yet stable, spider silk using microorganisms.
The team first used these microorganisms to make silk proteins, while also adding additional peptides. The new peptides, following patterns found in the protein sequence of amyloid polypeptides, help the artificial silk proteins form an ordered structure when folded and prevent them from sticking together in solution, increasing their yield. Then, using an array of tiny, hollow needles attached to the nozzle of a 3D printer, the researchers stretched the protein solution into thin threads in the air and woven them together into a thicker fiber. This setup acts like a giant artificial spider spinning its web.
They then woven their artificial silk fibers into prototype wound dressings, which they applied to mice with chronic wounds caused by osteoarthritis (a degenerative disease of the joints) and diabetes. Drug treatments were easily added to the dressings, and the team found that these modified dressings enhanced wound healing better than conventional bandages. Compared to a control group with neutral dressings, mice with osteoarthritis showed decreased inflammation and repair of tissue structure after 2 weeks of treatment, while diabetic mice with skin wounds treated with similar dressings demonstrated significant wound healing after 16 days of treatment. The new silk bandages are biocompatible and biodegradable, and the researchers say they are promising for future applications in medicine.
The authors acknowledge funding from the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Postgraduate Research and Practice Innovation Program of Jiangsu Province, the Nanjing Tech University Teaching Reform Project, the Discipline Fund of Nanjing Tech University School of Pharmaceutical Sciences, and the Promotion Program for Outstanding Doctoral Dissertations of Nanjing Tech University.