Prof. Michael J. Sailor, UC San Diego
“Micro- and Nanoparticles of Porous Silicon as in-vivo Diagnostic and Therapeutic
Agents”
The unique combinations of material properties that can be achieved with nanomaterials
provide new opportunities in medicine. This presentation will describe self-destructing
inorganic nanoparticles and microparticles based on a non-toxic porous silicon scaffold.
The material allows a modular approach to the design of imaging or therapeutic agents,
which includes features such as: intrinsic photoluminescence; singlet oxygen
sensitization; capacity for a wide range of payloads such as magnetic nanoparticles,
large proteins, or oligonucleotides; tunable degradation rates; and large external surface
to provide multivalent targeting. Porous silicon is a nanostructured material prepared by
oxidation of single crystal silicon in the presence of HF (Figure 1). The electrochemical
preparation conditions allow the precise tuning of pore diameter and pore wall
thickness, which impact both the degradation and drug release properties. Luminescent
nanoparticles constructed from silicon offer a non-toxic alternative to Cd-based quantum
dots, and porous silicon nanoparticles have been shown to be biodegradable and to
safely image tumors and organs in live animals. The addition of a targeting ligand that
selectively interacts with tissues can improve the efficacy of imaging or drug delivery.
These effects can be further enhanced if the nanoparticle contains more than one copy
of the targeting ligand, enabling multivalent interactions with the targeted tissue. The
use of the magnetic, photoluminescence, and reflective optical characteristics of porous
silicon particles for in-vitro and in-vivo sensing and imaging will be highlighted.
Figure 1. Preparation of micron- and nanometer-size porous Si particles by ultrasonic
fracture. At the right is a porous Si nanoparticle containing iron oxide nanoparticle
inclusions. Scale bar is 50 nm.