Nanoparticle-mediated synergistic drug combination for treating bone metastasis

Optimizing Oxygen-Production Kinetics of Manganese Dioxide Nanoparticles Improves Hypoxia Reversal and Survival in Mice with Bone Metastases

Persistent hypoxia in bone metastases induces an immunosuppressive environment, limiting the effectiveness of immunotherapies. To address chronic hypoxia, we have developed manganese dioxide (MnO2) nanoparticles with tunable oxygen production kinetics for sustained oxygenation in bone metastases lesions. Using polyethylene glycol (PEG)-stabilized MnO2 or poly(lactic[50]-co-glycolic[50] acid) (50:50 PLGA), poly(lactic[75]-co-glycolic[25] acid) (75:25 PLGA), and polylactic acid (PLA)-encapsulated MnO2 NPs, we demonstrate that polymer hydrophobicity attenuates burst oxygen production and enables tunable oxygen production kinetics. The PEG-MnO2 NPs resulted in rapid hypoxia reduction in spheroids, which was rapidly attenuated, while the PLA-MnO2 NPs exhibited delayed hypoxia control in cancer spheroids. The 50:50 PLGA-MnO2 NPs exhibited the best short- and long-term control of hypoxia in cancer spheroids, resulting in sustained regulation of the expression of HIF-1α and immunosuppressive genes. The sustained control of hypoxia by the 50:50 PLGA-MnO2 NPs enhanced the cytotoxicity of natural killer cells against cancer spheroids. In vivo, 50:50 PLGA-MnO2 showed greater accumulation in the long bones and pelvis, common sites for bone metastases. The NPs decreased hypoxia in bone metastases and decreased regulatory T cell levels, resulting in enhanced survival of mice with established bone metastases.

Dual-Targeting Biomimetic Semiconducting Polymer Nanocomposites for Amplified Theranostics of Bone Metastasis

Bone metastasis is a type of metastatic tumors that involves the spreads of malignant tumor cells into skeleton, and its diagnosis and treatment remain a big challenge due to the unique tumor microenvironment. We herein develop osteoclast and tumor cell dual-targeting biomimetic semiconducting polymer nanocomposites (SPFeNOC ) for amplified theranostics of bone metastasis. SPFeNOC contain semiconducting polymer and iron oxide (Fe3 O4 ) nanoparticles inside core and surface camouflaged hybrid membrane of cancer cells and osteoclasts. The hybrid membrane camouflage enables their targeting to both metastatic tumor cells and osteoclasts in bone metastasis through homologous targeting mechanism, thus achieving an enhanced nanoparticle accumulation in tumors. The semiconducting polymer mediates near-infrared (NIR) fluorescence imaging and sonodynamic therapy (SDT), and Fe3 O4 nanoparticles are used for magnetic resonance (MR) imaging and chemodynamic therapy (CDT). Because both cancer cells and osteoclasts are killed synchronously via the combinational action of SDT and CDT, the vicious cycle in bone metastasis is broken to realize high antitumor efficacy. Therefore, 4T1 breast cancer-based bone metastasis can be effectively detected and cured by using SPFeNOC as dual-targeting theranostic nanoagents. This study provides an unusual biomimetic nanoplatform that simultaneously targets osteoclasts and cancer cells for amplified theranostics of bone metastasis.

Catalytic antioxidant nanoparticles mitigate secondary injury progression and promote functional recovery in spinal cord injury model

Traumatic spinal cord injury exacerbates disability with time due to secondary injury cascade triggered largely by overproduction of reactive oxygen species (ROS) at the lesion site, causing oxidative stress. This study explored nanoparticles containing antioxidant enzymes (antioxidant NPs) to neutralize excess ROS at the lesion site and its impact. When tested in a rat contusion model of spinal cord injury, a single dose of antioxidant NPs, administered intravenously three hours after injury, effectively restored the redox balance at the lesion site, interrupting the secondary injury progression. This led to reduced spinal cord tissue inflammation, apoptosis, cavitation, and inhibition of syringomyelia. Moreover, the treatment reduced scar tissue forming collagen at the lesion site, protected axons from demyelination, and stimulated lesion healing, with further analysis indicating the formation of immature neurons. The ultimate effect of the treatment was improved motor and sensory functions and rapid post-injury weight loss recovery. Histological analysis revealed activated microglia in the spinal cord displaying rod-shaped anti-inflammatory and regenerative phenotype in treated animals, contrasting with amoeboid inflammatory and degenerative phenotype in untreated control. Overall data suggest that restoring redox balance at the lesion site shifts the dynamics in the injured spinal cord microenvironment from degenerative to regenerative, potentially by promoting endogenous repair mechanisms. Antioxidant NPs show promise to be developed as an early therapeutic intervention in stabilizing injured spinal cord for enhanced recovery.