N25 - Copper-based Biodegradable Photoluminescent Nanoparticles for Imaging & Drug Delivery

Introduction: : Peripheral artery disease (PAD), a condition affecting around 200M people worldwide, can be diagnosed and tracked using photoacoustic imaging (PAI). This non-invasive technique allows real-time high contrast vascular imaging by using near infrared laser light to generate sound waves from the tissue. However, its ability for deeper visualization is limited by reduced light penetration, low resolution, and optical scattering. Plasmonic nanoparticles (PNPs) can improve PAI by providing stronger and consistent signals to increase image resolution at higher depths. Copper (Cu) PNPs are ideal for sensing and imaging applications because of their tunable localized surface plasmon resonance, which enhances light absorption and scattering. Furthermore, they also exhibit advantageous catalytic activity, electrical and thermal conductivity, and antimicrobial properties. In previous research, we used aniline tetramer doped biodegradable photoluminescent polymers (BPLP-ATs) to develop fluorescent and photoacoustic erythropoietin (EPO) loaded theranostic nanoparticles (NPs) aimed at diagnosing and treating PAD. In this work, we modified our BPLP-ATs by adding Cu nitrite (BPLP-AT Cu), cupric oxide (BPLP-AT CuO), or cysteine-cupric oxide (BPLP-Cys CuO) to extend their plasmonic characteristics to provide stronger signals, deeper tissue penetration, and better high-resolution imaging. Then we combined these polymers with hydrophilic drug models EPO and bovine serum albumin (BSA) to formulate theranostic NPs. Next, we characterized the physicochemical, biocompatibility, drug loading, drug release, and photoacoustic properties of these nanoparticles.

Materials and

Methods: : NPs encapsulating hydrophilic drugs were prepared using a double emulsion method. Size, zeta potential, and morphology were determined with dynamic light scattering (DLS), phase analysis light scattering (PALS), nanoparticle tracking analysis (NTA) and transmission electron microscope (TEM). Fourier transform infrared spectroscopy (FTIR) was performed to analyze chemical composition and NP stability was assessed by observing agglomeration and size change in saline, simulated body fluid (SBF), and 10% fetal bovine serum (FBS). NP degradation profile was measured by dialysis against PBS under continuous shaking at 37 °C. Drug loading efficiency was determined directly from NPs and drug release profile was assessed by dialysis using a Float-A-Lyzer G2 device. The cytocompatibility of NPs was evaluated on endothelial progenitor cells (EPCs), human umbilical endothelial cells (HUVECs), and adult human dermal fibroblasts (HDFa). The photoacoustic properties of NPs were analyzed in-vivo using multispectral optoacoustic tomography (MSOT). Anesthetized mice were injected into the left thigh with 10 mg NPs/50 µL saline. Control was 50 µL saline injected in the right thigh. Thereafter, an MSOT InVision 256-TF small animal imaging system (iThera, Munich, Germany) was utilized for photoacoustic imaging.

Results, Conclusions, and Discussions:: Theranostic nanoparticles with photoacoustic properties and cargo capacity for hydrophobic and hydrophilic drugs were synthesized and characterized. Results show BPLP-AT CuO NPs demonstrated better cytocompatibility with EPCs, HUVECs, and HDFa than BPLP-AT Cu and BPLP-Cys CuO NPs. In-vivo MSOT imaging studies revealed that the comparative MSOT mean intensity for BPLP-AT CuO NPs was 0.63 arbitrary units (a.u.), higher than the 0.42 a.u. for BPLP-AT Cu NPs and 0.30 a.u. for BPLP-Cys CuO NPs. Therefore, BPLP-AT CuO NPs confirmed their extraordinary theranostic potential of as photoacoustic imaging contrast agent and drug delivery vehicle to diagnose, monitor, and treat PAD.

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