Scientists have developed a new technique that uses a patch embedded with microneedles to deliver cancer immunotherapy treatment directly to the site of melanoma skin cancer.
In animal studies, the technique more effectively targeted melanoma than other immunotherapy treatments, researchers said.
Melanoma treatments range from surgery to chemotherapy and radiation therapy. A promising new field of cancer treatment is cancer immunotherapy, which helps the body's own immune system fight off cancer, researchers said.
In the immune system, T cells are supposed to identify and kill cancer cells. T cells use specialised receptors to differentiate healthy cells from cancer cells.
However, cancer cells can trick T cells, by expressing a protein ligand that binds to a receptor on the T cells to prevent it from recognising and attacking the cancer cell.
Recently, cancer immunotherapy research has focused on using "anti-PD-1" (or programmed cell death) antibodies to prevent cancer cells from tricking T cells.
"However, this poses several challenges. First, the anti-PD-1 antibodies are usually injected into the bloodstream, so they cannot target the tumour site effectively," said Chao Wang, a postdoctoral researcher in the joint biomedical engineering programme at North Carolina State University (NC State) and the University of North Carolina at Chapel Hill (UNC-Chapel Hill).
"Second, the overdose of antibodies can cause side effects such as an autoimmune disorder," Wang said.
The researchers developed a patch that uses microneedles made from a biocompatible material to deliver anti-PD-1 antibodies locally to the skin tumour.
The anti-PD-1 antibodies are embedded in nanoparticles, along with glucose oxidase - an enzyme that produces acid when it comes into contact with glucose.
These nanoparticles are then loaded into microneedles, which are arrayed on the surface of a patch. When the patch is applied to a melanoma, blood enters the microneedles.
The glucose in the blood makes the glucose oxidase produce acid, which slowly breaks down the nanoparticles. As the nanoparticles degrade, the anti-PD-1 antibodies are released into the tumour.
"This technique creates a steady, sustained release of antibodies directly into the tumour site; it is an efficient approach with enhanced retention of anti-PD-1 antibodies in the tumour microenvironment," said Zhen Gu, assistant professor at NC State and UNC-Chapel Hill.
The researchers tested the technique in a mouse model. The microneedle patch was compared to treatment by injecting anti-PD-1 antibodies directly into the bloodstream and to injecting anti-PD-1 nanoparticles directly into the tumour.
"After 40 days, 40 per cent of the mice who were treated using the microneedle patch survived and had no detectable remaining melanoma - compared to a zero per cent survival rate for the control groups," said Yanqi Ye, a PhD student in Gu's lab.
