Side effects of chemotherapy are major problems associated with current cancer treatment. An effective way to minimize these side effects and improve the efficacy of cancer treatment is to deliver drugs specifically targeted to tumors. This can be achieved by encapsulating chemotherapy drugs inside nanoparticles that aggregate in tumors due to the enhanced permeability and retention effect.

In order to monitor the delivery of nanoparticle-drug conjugates, it is important to develop systems that can image the nanoparticles. Since two-photon fluorescent probes can lead to significant reduction of background fluorescence compared to single photon fluorescent probes, two-photon fluorescent nanoparticles were developed through the miniemulsion process, using a conjugated polymer—poly [2-(3-thienyl)ethanol butoxycarbonyl-methyl urethane])—and two surfactants—sodium dodecyl sulfate (SDS) and cetyl trimethylammonium bromide (CTAB).

Nanoparticle size decreased as surfactant concentration increased, and particle size remained constant for surfactant concentrations above the critical micellar concentration (CMC), which was 8.2 μM for SDS and 1 μM for CTAB. The average size of the nanoparticles with surfactants at CMC was 31.67 nm for SDS nanoparticles and 25.60 nm for CTAB nanoparticles. Both nanoparticle systems exhibited strong one-photon and two-photon fluorescent signals. Fluorescence microscopy demonstrated these nanoparticles were able to penetrate rat cardiomyocytes. The results suggest these nanoparticles may potentially be used for high-contrast cell imaging.