(676d) Serum Effects on Nanoparticle-Mediated Photoporation for Enhanced Intracellular Drug Delivery

Intracellular delivery of therapeutic and diagnostic molecules is restricted by plasma membrane. Often, endocytic route is used to transport molecules inside cells, which can render these molecules inactive due to pH changes. Nanoparticle-mediated photoporation offers a physical route to create transient pores allowing uptake of foreign substances by cells. Through near-infrared laser irradiation, nanoparticles absorb and dissipate energy to the surroundings, thereby vaporizing water to create steam bubbles. The subsequent thermal and acoustic outputs are believed to be responsible for membrane poration. Typical in vitro experiments are conducted with DU145 prostate cancer cells, carbon black nanoparticles and fluorescent uptake markers in cell suspension media, kept inside a cylindrical glass cuvette irradiated with 1064 nm wavelength laser beam. Post irradiation, cells are stained with PI (propidium iodide) for viability loss measurement and subsequently washed to remove nanoparticles and excess staining molecules. Cells are then analyzed for uptake and viability loss using flow cytometer.

This process has been optimized for >90% of cells exhibiting intracellular uptake of low-molecular weight (less than 1 kDa) marker compounds without significant cell viability loss. Understanding how changes in cellular micro-environment affect delivery efficiency is important for practical translation of this platform technology. Therefore, this study is focused on understanding the role of serum during photoporation, and how that understanding can be used to increase intracellular delivery of macromolecules.

Experimental results reveal 75% less loss of cell viability during laser irradiation at high fluence when cells are suspended in media containing 10 (v/v)% serum. Similar effects are observed in media containing albumin (major protein component present in serum) as well as denatured serum proteins. Further experiments show that a few polymer additives also help preserve cell viability during photoporation and thus viability protection by serum appears to be attributed to physical interactions between serum components and cell membrane/suspension media and not to biological activity, for example, associated with serum proteins. The ability of cells to stay alive at high fluence may enable macromolecular delivery (greater than 10 kDa) which have applications in protein and gene therapy. Thus, future experiments will explore these avenues in addition to investigating the mechanism behind cell viability protection in presence of serum and polymer additives.

Reference:

1. Sengupta et al. Efficient Intracellular Delivery of Molecules with High Cell Viability Using Nanosecond-Pulsed Laser- Activated Carbon Nanoparticles. ACS Nano 2889–2899 (2014)