Synthetic Soft Tissue Developed for Surgery

(Sasin Tipchai, Pixabay)

3 May 2019. Researchers developed a synthetic soft tissue for plastic and reconstructive surgery that in animal tests looks and performs more like real tissue. The team of surgeons, biomedical engineers, and materials scientists at Johns Hopkins University in Baltimore creating the material describe their findings in the 1 May issue of Science Translational Medicine (paid subscription required).

In addition, several of the authors also formed a spin-off company, LifeSprout Inc. in Baltimore, to commercialize their discoveries.

A Johns Hopkins team led by surgery professors Sashank Reddy and Justin Sacks, and biomaterials science professor Hai-Quan Mao are seeking better therapy options for patients encountering soft tissue loss, such as from cancer surgery to remove tumors and reconstructive surgery, to prevent scarring. Surgeons today can use soft tissue such as body fat from elsewhere in the patient’s body to fill in affected areas, or synthetic implants, neither of which, say the authors, are satisfactory.

“In order to reconstruct these defects,” says Sacks in a university statement, “we often move fat from one part of the body to another with a process called fat grafting. This is not always successful, as typically half of the grafted fat will die after it’s transplanted, and it’s often hard to predict how well these procedures will work out.” Reddy adds that for alternatives to fat grafting, “Currently our options are limited to implants, which are plagued by fibrosis and other problems, or ‘borrowing’ tissues from elsewhere in the body, which can cause deformity there as well.”

Mao’s lab at Johns Hopkins studies nanoscale materials for drug delivery and regenerative medicine. Together with Reddy and Sacks, Mao investigated gel materials that surgeons can fill in for tissue removed during surgery that work better than today’s implants and without surgically removing other tissue from the patient. The team discovered it would not be a simple task.

“Typically a gel-like material that’s porous enough for cells to spread inside,” notes Mao, ” is too soft to be able to hold its shape, and a material that is able to retain its shape when placed in the soft tissue defects is conversely too dense for cells to grow into. We really needed to synthesize a new material that is soft and porous yet resilient, almost like fat tissue or Jell-O.”

Their solution starts with a hydrogel, a water-based polymer with hyaluronic acid, a natural ingredient found in skin and other soft tissue. The Hopkins team then adds nanoscale fibers, where 1 nanometer equals 1 billionth of a meter, made of polycaprolactone, or PCL, a commercially-available, bio-compatible material used today in a variety medical applications. The nanoscale fibers create more of a matrix in the hydrogel making the material feel and act more like real human tissue. In addition, the PCL fibers bind to the hydrogel forming a composite material able to be move through a thin syringe needle for injections.

The researchers first tested the synthetic tissue in lab rats, injecting the material under the animals’ skin. The results show the composite material integrates with the rats’ natural tissue within 1 week, promoting regenerative enzymes and growth factor proteins, and after 12 weeks grows more blood vessels than 2 types of plain hydrogels. In rabbits, the team removed a cubic centimeter of tissue from the animals’ hind legs and injected the composite material in its place. The results show similar tissue and blood vessel regrowth as seen earlier in the rats.

Reddy, Sacks, Mao, and co-author Russell Martin founded LifeSprout Inc. in 2015 to take their injectable tissue discoveries to market. The company raised $1 million in seed capital in 2017, and another $6.5 million its first venture funding round in June 2018. In the following video, the authors tell more about the composite material and the company.

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