Good vibrations: light triggered drug release in living systems

Researchers from the University of California, San Diego, have developed a new way to release substances from polymeric capsules in living cells using near-infrared (NIR) light.

The major use for this technique is the targeted application of drugs in a viable system. However, corresponding author Associate Professor Adah Almutairi, believes this method could have a variety of industrial, medical and scientific uses, including “any technological application requiring that chemistry be controlled in time and in space, such as in catalysis or self-repairing materials or light-activated sunscreens or pesticide dosing.”

The targeted release of drugs is an increasing area of interest for many biomedical researchers and a number of methods have been developed to try and achieve it. In biological systems, the use of NIR-light as a trigger is particularly attractive because it can penetrate deeply into living tissue with low attenuation.

Previous methods for using NIR light in living systems suffer from a number of drawbacks. Too much heat generation and the use of toxic compounds can cause tissue damage. The need for high powered lasers and the use of designer, light-sensitive polymers can also make some strategies very expensive.

The multidisciplinary team, including Dr Roberto Malinow and Dr Kim Dore from the Department of Neuroscience, have developed a new approach that elegantly overcomes these major problems.

The technique, described in the journal ACS Nano, uses hydrated polymer particles that are irradiated with NIR light at a wavelength of 980 nm. At this wavelength, the optical energy excites the water molecules and converts it to heat. This heat causes the water molecules to vibrate with more energy altering the physical properties of the polymer to change in such a way that it releases its payload (e.g. a drug).

The polymer traps water in confined domains, so much less energy is needed to heat it up; imagine the difference between heating a glass of water compared to a whole bath. It also means that the overall heat of the particle is not significantly increased. Additionally, there is no need for toxic compounds and the particles can be made from already available polymers. The laser can also have lower power continuous output making it cheaper.

Other benefits of this technique include the application of multiple doses by simply turning the laser on and off, and control of the rate of release by adding different amounts of energy to the system.

Possible applications include self-healing capsules, on demand delivery of cues for cell proliferation, differentiation and migration and light-triggered drug delivery in vitro and in vivo tissues.

Further work on using different absorption wavelengths of water and advances in creating better polymer particles should help increase the efficiency and efficacy of this technique.

Paper Reference:

Viger ML, Sheng W, Doré K, Alhasan AH, Carling CJ, Lux J, de Garcia Lux C, Grossman M, Malinow R, and Almutairi A Near-Infrared-Induced Heating of Confined Water in Polymeric Particles for Efficient Payload Release ACS Nano 8:5 4815-4826 (2014) doi: 10.1021/nn500702g