Figure 1: Ultrasound, photoacoustic image of DiR and DiR-loaded nanoparticles and photoacoustic spectrum of DiR. (A) DiR in different acetonitrile/water co-solvent shows different photoacoustic intensities. The spectrum is measured and DiR in 50% acetonitrile/water co-solvent shows the highest photoacoustic intensity. (B) The photoacoustic intensity of DiR-loaded nanoparticles at different concentrations (10, 0.1, 0.01, 0.001, 0.0001 µM) is measured.
This story shared by Mr. Chien-Ju Chen, UCSD, La Jolla, California, USA.
The survival rate of patients with ovarian cancer is over 90% in early stages but it can be rather lethal if patients are diagnosed with in late stages. However, the traditional screening method, CA125 test, of ovarian cancer is ineffective. Fortunately, the screening method of ultrasound-based techniques combined with CA125 tests is promising. It was demonstrated that the sensitivity and specificity were 89.4% and 99.8%, respectively, in the recent large scale trial of over 200,000 women. Nonetheless, the positive predictive value was still 43.3% because of poor contrast between tumor tissues and normal tissues in ultrasound imaging. Photoacoustic imaging utilizes laser irradiation of imaging agents to produce acoustic and ultimately high contrast images. Our research work is developing DiR-loaded lipid-polymer hybrid nanoparticles applied to molecular imaging and ovarian cancer diagnosis.
We are developing nanoparticle-based photoacoustic imaging agents using nanoprecipitation method. We further modify these nanoparticles with folates and enable these nanoparticle-based imaging agents could actively target to the over-expressed folate receptors on ovarian cancer cells. In our preliminary studies, the photoacoustic intensity of DiR-loaded nanoparticles was measured in phantoms on our self-made sample holders. We obtained 3D images and photoacoustic spectrum of our DiR-loaded nanoparticles via Vevo LAZR system and LZ250 transducer. The ultrasound combined with photoacoustic image of DiR and the spectrum is shown in Figure 1 (A). Figure 1 (B) demonstrates the photoacoustic image of DiR-loaded nanoparticles.
Recently, we have validated the active targeting capability of our folate-modified nanoparticles with DiR on HeLa and A549 cell models. We believe this our nanoparticle-based photoacoustic imaging agents can enhance the contrast and achieve advances in sensitivity and specificity of ovarian cancer diagnosis that are needed in population-wide studies.