AbstractNanoparticulate contrast agents for molecular imaging have attracted widespread interest for diagnostic applications with high resolution in medicine. Here we introduce polymer-based multifunctional nanoparticles exhibiting a near infrared (NIR) absorption in the range of the Nd:YAG laser wavelength of 1064 nm as a novel resorbable photoacoustic contrast system and report about their biological evaluation.
Submicron sized spherical nanoparticles with a high encapsulation efficiency> 87% were achieved by incorporation of NIR dyes (IR5 / IR26) in poly[(rac-lactide)-co-glycolide] (PLGA) with 50 mol% glycolide content via a specific spray drying process in good yield> 75%. By subsequent application of a centrifugation protocol two different size fractions with a diameter in the range of 445 to 540 nm and 253 to 305 nm were obtained, which were further used for investigation of photoacoustic properties and cytotoxic effects. The prepared PLGA nanoparticles exhibited photoacoustic properties using a Nd:YAG laser-based system. After exposure of particle concentrations up to 10 mg ml-1 for two days no effects on viability, mitochondrial activity and proliferation and cell death of human hepatocarcinoma cells (HepG2) and monkey kidney cells (Vero) were observed.
The excellent photoacoustic properties in combination with the positive biological results qualify the dye-loaded PLGA particles as promising candidates for a resorbable photoacoustic contrast system.