Nano-engineering represents promising approach for vaccine delivery

Key Points

Chapel Hill, N.C. - Nano-engineering represents a promising approach for vaccine delivery, an expert says.

Immunonano-engineering capitalizes on the properties of matter on the nanoscale to design products that deliver drugs or prevent bacteria growth, or to generate new classes of drugs, says Adnan Nasir, M.D., clinical assistant professor of dermatology, University of North Carolina, Chapel Hill, N.C. "The Holy Grail of nanodrug delivery is to be able to make any formulation of drug that you're able to deliver to any tissue or cell with any desired pharmacokinetics and activity," he says.

Nanoparticle dimensions are "smaller than a cell, bigger than an atom," Dr. Nasir says. In the United States, nano-engineering encompasses molecules smaller than 1 micron (1,000 nm), versus 100 nm in Europe. The human body functions like a low-temperature physics lab, because the reactions that occur in the body at room temperature under physiologic conditions would require high temperatures or pressure outside the body.

Matter behavior

Matter also behaves differently at nanoscale than at macro scale, Dr. Nasir says. For example, a water strider beetle can walk on water not only because its nonpolar legs repel water, but also because its legs are covered in fine, hairlike projections.

"That fine structure causes the nonpolar leg to be even more nonpolar, or superhydrophobic. Nano-engineering is not just about making something small; it's about designing it precisely so that it has the functionality you desire," he says.

In immunology applications, "We can make synthetic materials that look like pollen or red blood cells, but on the nanoscale. If they are configured to be antigens, they elicit different immune responses based solely on their shape, not their size," Dr. Nasir says. Many features can be incorporated into a single nanoparticle, such that one can control electric charge, polarity and tissue targeting, creating a multifunctional nanoparticle.

In creams and emollients, "You can formulate a lipid nanoparticle that has a drug uniformly dispersed in it, or the drug only on the inside or outside of the particle. Doing this also allows you to control the release kinetics - if the drug is exclusively inside the particle, it may be released more slowly," Dr. Nasir says. Smaller particles tend to occlude skin better, so using nanoparticles could help manufacturers improve barrier creams, perhaps with added antibacterial or other properties.

For applications such as treating inflammation or delivering local chemotherapy, Dr. Nasir says temperature-sensitive nanoparticles can release drugs once tissue reaches a target temperature. Heat can be delivered externally or may be part of the calor associated with inflammation, he says.

Aptamers, ablation

One subject dermatologists will hear more about in coming years is aptamers - self-assembling RNA molecules that are selected for affinity, Dr. Nasir says. "In the synthesis of aptamers, we create random oligonucleotides containing either DNA or RNA and select them for their affinity for binding a desired material. They have been made to bind unique proteins, peptides, drugs, vitamins and inorganic compounds."

Aptamers may be used as drugs or antibody-mimicking drugs for therapy. "Currently, they're used for tests to detect analytes based on their binding affinity," Dr. Nasir says.

Photothermal ablation therapy represents another method of nanodrug delivery. "You can tune the frequency of light that a nanoparticle of gold will absorb by engineering it to a desired size and thickness," Dr. Nasir says. If one shines light at the resonant frequency of the nanoparticle, the nanoparticle heats up. Heat, coupled with targeting, allows colloidal gold nanoparticles to treat malignancies.

"The gold nanoparticles are added to cancer cells. Then, light that the frequency of the gold particle responds to is used to heat the particle and kill the cell," he says.

Typically, such applications use light in the near-infrared (800 nm) range because it penetrates 2 cm to 3 cm into skin and leaves nearby tissues undisturbed. "Near-infrared light is already being used in other medical applications such as pulse oximetry," Dr. Nasir says.