FEATURES & INNOVATIONS
Self-assembling biomimetic nanostructures
A new class of ultrasmall peptides with biomimetic properties paves the way to diverse biomedical applications.
T
he design of biological molecules that mimic living structures and tissue is emerging as one of the
most valuable strategies in bioengineer- ing. Such biomimetic molecules, coupled with increasingly accurate simulations of cellular growth and responses, are leading to a wide range of regenerative applications as well as the development of controlled drug delivery systems and biochips for pharmaceutical research and diagnosis. In a significant step forward in the field, Charlotte Hauser and co-workers at the A*STAR Institute of Bioengineering and Nanotechnology (IBN) have designed a new class of ultrasmall peptides capable of self-assembling into a variety of structures such as membranes, micelles, tubules and gels that are suitable for application in tis- sue engineering and regenerative medicine.
Bioengineering breakthrough
Te unique class of self-assembling pep- tides designed by the IBN research team consists of only 3 to 7 amino acids, in con- trast to conventional peptides that usually
require 16 to 32 amino acids. Each peptide molecule is characterized by a water-solu- ble ‘polar head’ and a water-insoluble ‘tail’, and this ampiphilic property enables the molecules to self-assemble spontaneously in water to form hydrogels — stiff, water- based gels held together by stable fibrous structures. Tese natural peptide-based hydrogels offer an attractive,
low-cost
alternative for the manufacture of biomi- metic materials, as they do not require the addition of enzymes or chemical agents during the process of formation. Using field-emission scanning electron
microscopy (FESEM), the researchers observed that the structure of the peptide- derived hydrogels is remarkably similar to collagen, the most abundant protein in mammals and the main component of connective tissue found in tendons, carti- lage, ligaments, bone, adipose tissue and lymphatic tissue.
New treatments for spinal disc damage
Te biocompatibility of the peptide-
Scanning electron microscopy image of the honeycomb-like structure of the peptide scaf- folds, which enable the hydrogels to contain large amounts of water
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derived hydrogels developed by Hauser and her co-workers have particularly promising applications in the development of new treatment options for cartilage repair and spinal disc replacement. “We are currently investigating the potential of our peptide scaffold for the treatment of degenerative disc disease,” says Hauser. “We hope to offer an injection therapy that would render invasive surgical treat- ment obsolete, to meet the clinical need for disc prostheses that could inhibit or repair early-stage disc damage.” Degenerative disc disease — a debili- tating condition caused by the erosion of
Scanning electron microscopy image of fibrous structures formed by self-assembly of ultrasmall peptides. These structures closely resemble collagen fibers.
a collagenous substance called nucleus pulposus in the middle of the spinal disc — currently affects approximately 85% of people by the age of 50. New cura- tive therapies afforded by next-generation bioengineering are therefore of particular interest
in orthopedics. Existing treat-
ments often involve implanting an arti- ficial disc made of metal or rigid plastic, but the design of biocompatible hydrogels that are capable of absorbing mechanical shock and providing flexibility by closely replicating the properties of a natural spinal disc could prove to be a much more effective treatment while at the same time being much less invasive. Hauser and her co-workers discovered that their peptide-derived hydrogels are heat-resistant up to 90°C and demon- strate tunable, high mechanical strength. Te stiffness of the hydrogels can also be tailored by altering the concentra- tion of the peptide, besides changing the ionic strength and pH. Te entrapment of large amounts of water, in some cases up to 99.9%, results in the formation of three-dimensional peptide scaffolds that resemble a porous honeycomb-like struc- ture. Te tunable mechanical properties of the hydrogels may lead to the development of biomaterials that could be more readily customized to individual patients.
Insights into degenerative diseases
In another study, Hauser and her co-work- ers discovered that the self-assembly of ultrasmall peptides mimics the formation
A*STAR RESEARCH OCTOBER 2011–MARCH 2012
© Nano Today
© 2011 PNAS
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