Angiogenesis is the name given to the process by which new blood vessels form throughout the body. It is vital for growth and development and plays a major role in processes like wound healing, rheumatoid diseases and in pregnancy. It is also involved in tumour growth and metastasis.

Angiogenesis starts when specific molecules that bind to angiogenic receptors on cells activate endothelial cells. This activation leads to the endothelial cells proliferating – in a sort of cascade – and then assembling to form new vascular structures. The process is activated (via pro-angiogenic factors) by signals that regulate new vessel growth or inhibited (via anti-angiogenic ones).

Although angiogenic drugs can be used to increase or reduce blood capillary growth in certain diseases, most of these treatments are only effective for a short time. And more often than not, the drugs need to be administered in large quantities – something that can lead to side effects and even toxicity.

Peptide-coated particles

Nanoparticles could come into their own here says a team led by Antonios Kanaras and Timothy Millar at Southampton. Nanoparticles are efficient drug-carrying and delivery vehicles since they are able to encapsulate large quantities of therapeutic molecules. What is more, their surfaces can be functionalized with different receptor molecules (usually antibodies) to target specific diseases in the body.

Kanaras and Millar’s team looked at how three types of peptide-coated gold nanoparticles can activate or inhibit blood vessel growth in vitro. The first peptide (that the researchers called P1) binds to the “vascular endothelial growth factor” receptor and promotes so-called signal cascade activating genes; the third peptide (P3) binds to the neurophilin-1 receptor and blocks blood capillary formation; and the second (P2) is a control because it does not interact with either of these receptors but simply enters cells.

“We found that the ‘activating” nanoparticles accelerate angiogenesis by a factor of two while the ‘inhibiting’ ones significantly prevent angiogenesis,” Kanaras told Stimulating angiogenesis can be useful in situations in which vascular growth is desirable, he said, such as in wound healing, but inhibiting angiogenesis will be important for slowing down tumour growth, or stopping it altogether.

Such studies are critical for understanding how nanoparticles can affect blood vessel growth and will open up new directions in angiogenic treatment using gold nanoparticles as a platform for drug development, he added.

“Manipulating tumour angiogenesis is certainly the next big step in this research,” he stated. “It is well known that cancer cells need angiogenesis to grow. Will it really be possible for us to stop angiogenesis near a tumour site using functionalized nanoparticles? And how efficient could such a strategy be? These are the questions that our research group is currently focusing on.”

The present work is detailed in ACS Nano.