After the stamp is removed its pattern is revealed in the pattern of blood vessels below. Image: Micro and Nanotechnology Laboratory
Researchers have developed a bandage that stimulates and directs blood
vessel growth on the surface of a wound. The bandage, called a “microvascular
stamp,” contains living cells that deliver growth factors to damaged tissues in
a defined pattern. After a week, the pattern of the stamp “is written in blood
vessels,” the researchers report.
A paper describing the new approach will appear in Advanced Materials.
“Any kind of tissue you want to rebuild, including bone,
muscle or skin, is highly vascularized,” says University of Illinois chemical
and biomolecular engineering professor Hyunjoon Kong, a co-principal
investigator on the study with electrical and computer engineering professor Rashid
Bashir. “But one of the big challenges in recreating vascular networks is how we
can control the growth and spacing of new blood vessels.”
“The ability to pattern functional blood vessels at this
scale in living tissue has not been demonstrated before,” Bashir says. “We can
now write features in blood vessels.”
Other laboratories have embedded growth factors in materials
applied to wounds in an effort to direct blood vessel growth. The new approach
is the first to incorporate live cells in a stamp. These cells release growth
factors in a more sustained, targeted manner than other methods, Kong says.
The stamp is nearly 1-cm across and is built of layers of a
hydrogel made of polyethylene glycol (an FDA-approved polymer used in laxatives
and pharmaceuticals) and methacrylic alginate (an edible, Jell-O-like
The stamp is porous, allowing small molecules to leak
through, and contains channels of various sizes to direct the flow of larger
molecules, such as growth factors.
The researchers tested the stamp on the surface of a chicken
embryo. After a week the stamp was removed, revealing a network of new blood
vessels that mirrored the pattern of the channels in the stamp.
“This is a first demonstration that the blood vessels are
controlled by the biomaterials,” Kong says.
The researchers see many potential applications for the new
stamp, from directing the growth of blood vessels around a blocked artery, to
increasing the vascularization of tissues with poor blood flow, to “normalizing” blood vessels that feed a tumor to improve the delivery of
anti-cancer drugs. Enhancing the growth of new blood vessels in a coordinated
pattern after surgery may also reduce recovery time and lessen the amount of scar
tissue, the researchers say.
In another study published earlier this year, the team
developed a biodegradable material that supports living cells. Future research
will test whether the new material also can be used a stamp.