Thermally -responsive interpenetrating polymer network nanoparticles as intelligent therapeutic systems

Thermally-responsive interpenetrating polymer network (IPN) nanoparticles, composed of polyacrylamide, poly(acrylic acid), poly(methacrylic acid), poly(2-ethylacrylic acid), and poly(2-propylacrylic acid), were synthesized using a sequential inverse emulsion polymerization technique. These materials were shown to exhibit a positive sigmoidal swelling response upon heating in solution. The positive swelling response of these nanoparticles serves as an ideal on/off trigger for controlled release of an encapsulated agent and could be used as a platform technology in a variety of applications. Solid gold nanoparticles (diameter ∼ 40-50 nm) as well as gold nanoshells (diameter ∼ 200 nm) were also synthesized using standard citrate reduction and core-shell synthesis methods, respectively. These materials were shown to absorb light in the visible to near infrared region and converted that energy to heat locally. The prepared gold nanoparticles were then incorporated within the IPN polymer particles by in situ polymerization during the first step of the sequential inverse emulsion polymerization. These novel metal-polymer nanocomposite particles were then grafted with linear poly(ethylene glycol) polymer chains to increase their biocompatibility and mononuclear phagocytic recognition avoidance or stealth characteristics. Swelling and imaging of the complete nanocomposite system in solution with only laser light activation was then achieved, making these an ideal system for a non-invasive externally-triggered controlled drug delivery device.