August 15, 2017

What if one day, we could teach our bodies to self-heal like a lizards tail, and make severe injury or disease no more threatening than a paper cut?

Or heal tissues by coaxing cells to multiply, repair or replace damaged regions in loved ones whose lives have been ravaged by stroke, Alzheimers or Parkinsons disease?

Such is the vision, promise and excitement in the burgeoning field of regenerative medicine, now a major ASU initiative to boost 21st-century medical research discoveries.

ASU Biodesign Institute researcher Nick Stephanopoulos is one of several rising stars in regenerative medicine. In 2015, Stephanopoulos, along with Alex Green and Jeremy Mills, were recruited to the Biodesign Institutes Center for Molecular Design and Biomimetics (CMDB), directed by Hao Yan, a world-recognized leader in nanotechnology.

One of the things that that attracted me most to the ASU and the Biodesign CMDB was Haos vision to build a group of researchers that use biological molecules and design principles to make new materials that can mimic, and one day surpass, the most complex functions of biology, Stephanopoulos said.

I have always been fascinated by using biological building blocks like proteins, peptides and DNA to construct self-assembled structures, devices and materials, and the interdisciplinary and highly collaborative team in the CMDB is the ideal place to put this vision into practice.

Yans research center uses DNA and other basic building blocks to build their nanotechnology structures only at a scale 1,000 times smaller than the width of a human hair.

Theyve already used nanotechnology to build containers to specially deliver drugs to tissues, build robots to navigate a maze or nanowires for electronics.

To build a manufacturing industry at that tiny scale, their bricks and mortar use a colorful assortment of molecular Legos. Just combine the ingredients, and these building blocks can self-assemble in a seemingly infinite number of ways only limited by the laws of chemistry and physics and the creative imaginations of these budding nano-architects.

The goal of the Center for Molecular Design and Biomimetics is to usenatures design rulesas an inspiration in advancing biomedical, energy and electronics innovation throughself-assembling moleculesto create intelligent materials for better component control and for synthesis intohigher-order systems, said Yan, who also holds the Milton Glick Chair in Chemistry and Biochemistry.

Prior to joining ASU, Stephanopoulos trained with experts in biological nanomaterials, obtaining his doctorate with the University of California Berkeleys Matthew Francis, and completed postdoctoral studies with Samuel Stupp at Northwestern University. At Northwestern, he was part of a team that developed a new category of quilt-like, self-assembling peptide and peptide-DNA biomaterials for regenerative medicine, with an emphasis in neural tissue engineering.

Weve learned from nature many of the rules behind materials that can self-assemble. Some of the most elegant complex and adaptable examples of self-assembly are found in biological systems, Stephanopoulos said.

Because they are built from the ground-up using molecules found in nature, these materials are also biocompatible and biodegradable, opening up brand-new vistas for regenerative medicine.

Stephanopoulos tool kit includes using proteins, peptides, lipids and nucleic acids like DNA that have a rich biological lexicon of self-assembly.

DNA possesses great potential for the construction of self-assembled biomaterials due to its highly programmable nature; any two strands of DNA can be coaxed to assemble to make nanoscale constructs and devices with exquisite precision and complexity, Stephanopoulos said.

During his time at Northwestern, Stephanopoulos worked on a number of projects and developed proof-of-concept technologies for spinal cord injury, bone regeneration and nanomaterials to guide stem cell differentiation.

Now, more recently, in a new studyin Nature Communications, Stephanopoulos and his colleague Ronit Freeman in the Stupp laboratory successfully demonstrated the ability to dynamically control the environment around stem cells, to guide their behavior in new and powerful ways.

In the new technology, materials are first chemically decorated with different strands of DNA, each with a unique code for a different signal to cells.

To activate signals within the cells, soluble molecules containing complementary DNA strands are coupled to short protein fragments, called peptides, and added to the material to create DNA double helices displaying the signal.

By adding a few drops of the DNA-peptide mixture, the material effectively gives a green light to stem cells to reproduce and generate more cells. In order to dynamically tune the signal presentation, the surface is exposed to a soluble single-stranded DNA molecule designed to grab the signal-containing strand of the duplex and form a new DNA double helix, displacing the old signal from the surface.

This new duplex can then be washed away, turning the signal off. To turn the signal back on, all that is needed is to now introduce a new copy of single-stranded DNA bearing a signal that will reattach to the materials surface.

One of the findings of this work is the possibility of using the synthetic material to signal neural stem cells to proliferate, then at a specific time selected by the scientist, trigger their differentiation into neurons for a while, before returning the stem cells to a proliferative state on demand.

One potential use of the new technology to manipulate cells could help cure a patient with neurodegenerative conditions like Parkinsons disease.

More:
Restoring loss: Bio-inspired materials give boost to regenerative medicine - Arizona State University