(615c) Folate-Targeted Semiconducting Polymeric Patchy Particles: Potential Tool for Photoacoustic Imaging and Drug Delivery

Introduction: Ovarian cancer is the eighth most common cancer in women and the most lethal gynecologic malignancy. The staging of ovarian cancer is critical, as it affects both the prognosis and the treatment of the patient. In the clinical setting, Ultrasound (US) and Computed Tomography (CT) are the most common imaging modalities for diagnoses ovarian cancer. Although CT provides high accuracy for ovarian cancer staging of up to 94%; it offers poor soft tissue contrast which could resulting poor sensitivity and specificity in screening; whilst US lacks tissue specificity. Other techniques such as MR and nuclear imaging are expensive and not accessible in some communities. Photoacoustic Imaging (PAI) is a non-invasive imaging technique that combines high optical sensitivity and high US spatial resolution. Here, we report the design and synthesis of folate-targeted Semiconducting Polymeric Patchy Nanoparticles (SPPNPs). These particles consist of poly (lactic-co-glycolic acid) (PLGA), a biocompatible, biodegradable and FDA-approved polymer, lipid-polymer functional groups (LPFGs), and a semiconducting polymer. Imaging performance was conducted and in vitro experiments, using SKOV3 ovarian cancer cells, were performed.

Materials and Methods: We synthesized SPPNPs by a modified single emulsion method developed in-house. We characterized the SPPNPs’ internal structure using the Transmission Electron and Focused-Ion-Beam microscopes. The stability of nanoparticles was performed with the dynamic light scattering technique. We used Nuclear Magnetic Resonance, Thin Layer Chromatography and Matrix-Assisted Laser Desorption/Ionization to demonstrate successful surface functionalization of the nanoparticles with the targeting moiety, folic acid. Uptake in ovarian cancer cells (SKOV3) was assessed by Flow Cytometry, and cell viability was determined by cell titer glow assay. Multi-Spectral Optoacoustic Tomography (MSOT) imaging was carried out in vivo.

 Results: The particle characterization shows that SPPNPs have an average size of 210±10 nm. They are highly stable in aqueous solution and human serum. SPPNPs have unique patch-core-shell structural features: hollow core and a patchy surface made of single lipid-polymer based patches. Both the patches and particle’s surface are functionalized folic acid molecules to bind specifically to folate receptors that are overexpressed in SKOV3 cells. SPPNPs emit a PA from 670 nm to 950 nm wavelength, which is in the range of the clinical imaging window. We assessed the SPPNPs’ targeting ability by assessing their cellular uptake at different time points (i.e., 2, 24 and 48 hrs.). We found that SPPNPs are avidly taken by SKOV3, and the longer the incubation time, the higher the cellular uptake. The in vitro cell viability studies showed high percentage of cell viability of SPPNP at different doses indicating no toxicity induced by these particles at the cellular level. In vitro drug release studies at various pH showed that 98% of the drug is released over a period of 30 days. Furthermore, we assessed the imaging capability of SPPNPs by evaluating their photoacoustic performance. The photoacoustic results showed that SPPNP emit a high PA signal at a low dose that is comparable to gold nanorods, standard photoacoustic contrast agents.

Conclusions: These preliminary data demonstrate PAI imaging capabilities of SPPNPs and in vitro data show no toxicity to cells. Effective drug release was also demonstrated in vitro. Future studies will focus on in vivo performance of SPPNPs in a tumor model of ovarian cancer.