P16 - Core-Shell Microparticles for Chemo-Photothermal Triple-Negative Breast Cancer Therapy

Introduction: : Triple-negative breast cancer (TNBC) accounts for about 10-15% of all breast cancers, affecting approximately 13 in every 100,000 American females. It is challenging to treat due to the lack of estrogen, progesterone, and HER2 receptors, which are typically targeted for breast cancer treatment. Systemic chemotherapy methods lack specificity and are associated with toxic side effects. Natural bacterial products, such as pyocyanin isolated from Pseudomonas aeruginosa, which kill cancer cells through oxidative stress, provide a sustainable way of developing anticancer drugs. Prior work demonstrates the anticancer effects of pyocyanin on triple-negative breast cancer cells. Recent efforts focus on controlling drug delivery to effectively kill TNBC cells with minimal side effects. However, tuning drug release on demand is critical to accelerating TNBC tumor killing and suppressing tumor recurrence, but it remains a challenge. Gold nanoparticles exhibit surface plasmon resonance upon interacting with laser light, leading to heat generation, which can make surrounding polymers more porous. We hypothesize that photothermal regulation of drug release can be accomplished by incorporating gold nanoparticles into polymer microcarriers and leveraging the underlying laser-gold nanoparticle interactions. This work presents novel light-responsive core-shell microparticles for the controlled delivery of pyocyanin (Pc) for chemo-photothermal TNBC treatment. The core-shell microparticles comprise a PLGA-pyocyanin shell and a core containing gold nanoparticles (GNP).

Materials and

Methods: : Pyocyanin was extracted from Pseudomonas aeruginosa using our established protocol and purified using silica-gel column chromatography. PLGA solution was prepared in dichloromethane, and pyocyanin (Pc) was added at a 5 mg/ml concentration, followed by gold nanoparticles (GNP) at 10 wt.%. The gold nanoparticles and pyocyanin were encapsulated in PLGA microparticles using a single emulsion process to produce PLGA-Pc-GNP core-shell microparticles. The microparticles were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS). The photothermal profiles of the scaffolds were determined through irradiation with near-infrared (NIR) laser beams (λ = 810 nm) at 1.0 W/cm2, and the temperature changes were detected using an infrared thermal camera. Drug release profiles were obtained in PBS at 37°C (pH 7.4) with/without laser treatment to investigate the photothermal regulation of drug release. Finally, we evaluated the effects of photothermal-induced drug release and hyperthermia (41-44°C) on TNBC cell (MDA-MB-231 cell line) death using the alamar blue cell viability assay. Flow cytometry was used to determine the mechanism of cell death, while injury to cytoskeletal structures (actin and vinculin) was visualized using immunofluorescence staining and confocal microscopy.

Results, Conclusions, and Discussions:: This work aimed to develop novel core-shell microparticles comprising PLGA, pyocyanin, and gold nanoparticles that respond to NIR laser beams and photothermally trigger drug release on demand to kill TNBC cancer cells. SEM images showed that the core-shell microparticles were spherical (Fig. 1A) with a mean diameter of 1.14 ± 0.36 µm. DLS analysis yielded a hydrodynamic diameter of 8.37 ± 0.72 µm with a polydispersity index of 0.20 ± 0.10, indicating the swelling potential of the microparticles. The microparticles exhibited a zeta potential of -21.20 ± 0.55 mV, suggesting their relative stability in aqueous environments. TEM images revealed the presence of gold nanoparticles in the core of the microparticles (Fig. 1B & 1C), which confirmed our core-shell microparticle design. As a result, we irradiated the microparticles with a near-infrared laser beam (1.0 W/cm2), which penetrated and interacted with gold nanoparticles to induce heating through the surface plasmon resonance effect, leading to a ~10°C rise in temperature over 20 min and rapid cooling upon laser light withdrawal (Fig. 2A). The photothermal response of the core-shell microparticles resulted in enhanced pyocyanin release immediately during the 30-day drug release study (Fig. 2B), leading to increased TNBC cell death (Fig. 2C), as exhibited by the significant reduction in cell viability. Flow cytometry results revealed that cell death was predominantly through necrosis without laser treatment and apoptosis when exposed to laser irradiation (Figure 3). The pyocyanin released from the core-shell microparticles induced damage to actin and vinculin cytoskeletal structures, ultimately resulting in cell death. The light-responsive core-shell microparticles we developed in this work can be used to tune drug release to enhance drug-induced TNBC cell death. After the release of the drug payload, terminal hyperthermia (41-44°C) can be induced to kill residual TNBC cells. Ultimately, our multimodal chemo-photothermal approach has implications for effectively killing tumor and residual cells to treat TNBC and suppress tumor recurrence.

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