[Combination of hyaluronidase and pH-responsive, IR780-loaded photosensitive micelle enhanced anticancer effect in...

Objectives: To investigate the enhancement of tumor penetration and photodynamic therapy (PDT) efficacy in triple-negative breast cancer by hyaluronidase (HAase) using a novel pH-responsive IR780-loaded photosensitive micelle. Methods: The pH-responsive IR780-loaded photosensitive micelles were prepared using the nanoprecipitation method, and their morphology, size, and encapsulation efficiency were characterized. The in vitro stability and pH-responsive drug release of the micelles were also evaluated. The cytotoxicity of the micelles on triple-negative breast cancer cells (MDA-MB-231) was assessed using a cell counting kit. A nude mouse breast cancer model was established, and HAase was injected intratumorally 24 hours before intravenous injection of the photosensitive micelles. The effect of HAase on the biodistribution and tumor uptake of the micelles was detected using small animal in vivo imaging. CD31 and HIF-1α immunofluorescence staining were performed to investigate the mechanism of HAase-enhanced tumor penetration. The body weight and tumor volume of the mice were measured, and necrosis and apoptosis of tumor tissues were assessed using HE staining and TUNEL staining, respectively. Results: Transmission electron microscopy showed that the micelles had a uniform particle size of approximately 60-70 nm, with a hydrated particle size of (98.03±0.22) nm. The IR780 encapsulation efficiency was 74.15%, with a drug loading content of 2.07%. After 7 days at 4 ℃, there was no significant change in hydrated particle size (P=0.062). The 24-hour release rates of the micelles in PBS at pH 7.4 and 6.5 were (2.41±0.21)% and (43.69±2.09)%, respectively, showing a significant difference (P＜0.000 1). The cytotoxicity assay revealed that the cell viability in the micelles group without light exposure was significantly higer than that in the micelles group under light exposure [(97.00±5.38)% vs. (53.27±9.00)%, P=0.000 2]. The micelles were able to target and accumulate in the tumor tissue, and this accumulation increased significantly with HAase treatment. CD31 and HIF-1α immunofluorescence staining indicated that the CD31 signal was enhanced [(0.27±0.05)% vs. (4.57±0.27)%, P＜0.000 1] and the HIF-1α signal was reduced [(5.14±0.38)% vs. (0.08±0.04)%, P＜0.000 1] in the HAase-treated group compared to that in the micelle-only group. After 11 days of treatment with HAase combined with photosensitive micelles, there was no statistically significant difference in mouse body weight (P＞0.05). However, the tumor volume inhibition rate in the HAase-micelle-mediated PDT group was significantly higher than that in the micelle-mediated PDT group [(87.66±6.37)% vs. (25.34±12.63)%, P=0.002]. Histological staining showed a significant increase in tumor cell necrosis and apoptosis in the HAase-micelle-mediated PDT group. Conclusion: HAase enhances the deep tumor penetration and targeted accumulation of pH-responsive IR780-loaded photosensitive micelles, significantly improves the efficacy of photodynamic therapy in triple-negative breast cancer.