Light-Responsive Nanocomposite Scaffolds for Controlled Delivery of Prodigiosin for 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 compounds, such as prodigiosin, which kill cancer cells through oxidative stress, provide a sustainable way of developing anticancer drugs. Recent efforts focus on developing controlled delivery approaches to effectively kill TNBC cells with minimal side effects. Prior work demonstrates the anticancer effects of prodigiosin towards triple-negative breast cancer. However, tuning drug release on demand is critical to accelerating TNBC tumor killing and suppressing tumor recurrence, but it remains a challenge. Magnetite (iron oxide) nanoparticles exhibit surface plasmon resonance upon interacting with laser light, leading to heat generation, which can make surrounding polymers more porous. We hypothesize that incorporating magnetite nanoparticles into polymer scaffolds can lead to photothermal regulation of drug release. In this work, we present a chemo-photothermal approach for the controlled delivery of prodigiosin for TNBC treatment that utilizes a light-responsive nanocomposite scaffold made of poly(lactic-co-glycolic acid) (PLGA), polycaprolactone (PCL), and magnetite nanoparticles.

Materials and

Methods: : Prodigiosin was extracted from Serratia marcescens using our established protocols. A blend of PLGA/PCL solution was prepared in dichloromethane, and prodigiosin (PGS) was added at a concentration of 5 mg/ml. Magnetite nanoparticles with different volume fractions (0%, 1%, 5%, and 10%) were added to the mixture, and scaffolds were produced by casting the resulting mixture into molds containing sodium chloride particles (106-150 μm size range), followed by salt leaching using deionized water. The physicochemical properties of the scaffolds were characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The photothermal profiles of the scaffolds were determined through irradiation with near-infrared laser beams (λ = 810 nm) at 1.0 W/cm2, and the temperature changes were detected using an infrared thermal camera. The drug release profiles were obtained under simulated physiological conditions (PBS, pH 7.4, 37°C) with/without laser treatment. We evaluated the effects of photothermal-induced drug release and hyperthermia (41-44°C) on TNBC cell (MDA-MB-231) viability (alamar blue assay) and determined the mechanism of cell death (flow cytometry). Finally, a chicken tissue phantom was used to simulate potential in vivo laser-tissue interactions.

Results, Conclusions, and Discussions:: This work aimed to develop a nanocomposite scaffold that responds to NIR laser beams and photothermally triggers drug release on demand to kill TNBC cancer cells. SEM micrographs show that the scaffolds were porous with non-uniform pore structures, with no significant morphological differences observed between the scaffolds, suggesting that the incorporation of magnetite nanoparticles did not influence the scaffold structure. Thermal analysis revealed that the presence of magnetite nanoparticles reduced the decomposition temperature in both types of porous scaffolds, although characteristic peaks remained consistent. Upon irradiation with a near-infrared laser beam at a power density of 1.0 W/cm2, the laser interacted with the magnetite nanoparticles within the scaffold to induce heating through the surface plasmon resonance effect, leading to a rise in temperature over 20 min and rapid cooling upon laser light withdrawal (Figure 1A). The photothermal response of the scaffolds resulted in enhanced release of prodigiosin from the scaffolds containing 5% and 10% magnetite nanoparticles over 70 days (Figure 2). Increasing the magnetite proportion resulted in higher laser-induced heating, which led to greater drug release and resulted in increased TNBC cell death after 72 hours. Flow cytometry results revealed that cell death was predominantly through necrosis without laser treatment, and apoptosis when exposed to laser irradiation (Figure 3). When the scaffolds were buried 8 mm deep in a chicken tissue phantom (Figure 1C-H), the NIR laser light (3.0 W/cm2) penetrated the soft tissue and interacted with the magnetite nanoparticles to induce heating, as shown in Figure 1B. This suggests that the scaffolds could be implanted in resected breast tumor regions within the penetration depths of NIR laser light. The light-responsive scaffolds we developed in this work can be used to tune prodigiosin 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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