A scanning electron micrograph shows an array of silver-coated microneedles with antimicrobial properties.

By incorporating antimicrobial properties into microneedles, researchers at the University of North Carolina–North Carolina State University Joint Department of Biomedical Engineering hope to allay fears about infection.
 

According to a North Carolina State University release, the use of microneedles results in less pain, less tissue damage, and reduced skin inflammation for patients. However, there is concern that the pores created by microneedles in the epidermis could allow pathogenic microorganisms to enter a patient’s body.
 

To eliminate this risk of infection, scientists are experimenting with the use of a combination of two-photon polymerization, a laser-based rapid prototyping technique, and polydimethylsiloxane micromolding. According to Roger Narayan, PhD, a professor in the joint biomedical engineering department, the processes can be used to prepare both degradable microneedles and microneedles that are used for permanent and semipermanent devices such as glucose monitors.
 

For their project, the researchers employed two-photon polymerization to fabricate a master structure of a microneedle array made out of organically modified ceramic material. Then, a micromolding process was used to replicate the array. In the final step, the scientists used a high-energy pulsed excimer laser to vaporize high-purity silver and create thin silver films on the microneedle arrays.
 

A scanning electron micrograph shows an array of biodegradable polyethylene glycol–based microneedles with antimicrobial properties.

Narayan says pulsed laser deposition is an ideal way to add antimicrobial properties because “it enables low-porosity, high-density films of antimicrobial materials to be deposited on microneedles. Deposition of antimicrobial films can be performed at room temperature, enabling antimicrobial microneedles to be prepared out of a wide variety of materials.”
When testing the arrays, the team discovered that the silver films on the microneedle arrays prevented microbial growth and did not negatively affect skin cell growth. “Silver exhibits what is commonly referred to as a ‘broad spectrum’ of activity against microorganisms as well as antiinflammatory activity,” Narayan says.
 

The team also experimented with degradable microneedles, which can be used for single-use drug-delivery applications. For this application, the scientists integrated an antimicrobial agent directly into the material used to make the microneedle. When the microneedle dissolves, it releases the antimicrobial agent that guards against infection.
 

The researchers have support from the National Science Foundation, the National Institutes of Health, and the Department of Defense. Narayan says they plan to start in vivo studies of the microneedle design in the near future. He expects their project to trigger greater use of the microneedles in outpatient treatments and technologies. “For example, microneedles could be used as a relatively pain-free and user-friendly alternative to conventional needles in diabetes treatment. They may also figure into new technologies pertaining to the delivery of anticancer drugs,” he says.
 

Contributors to the project include Nancy Monteiro-Riviere, PhD, professor of investigative dermatology and toxicology at the Center for Chemical Toxicology Research and Pharmacokinetics at North Carolina State University, as well as researchers from North Dakota State University, Laser Zentrum Hannover, and other institutions.