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Theranostics 2021; 11(4):1953-1969. doi:10.7150/thno.52997 This issue Cite

Research Paper

Increased photodynamic therapy sensitization in tumors using a nitric oxide-based nanoplatform with ATP-production blocking capability

Qinyanqiu Xiang¹, Bin Qiao¹, Yuanli Luo¹, Jin Cao¹, Kui Fan², Xinghua Hu³, Lan Hao¹, Yang Cao¹, Qunxia Zhang^1✉, Zhigang Wang^1✉

1. Institute of Ultrasound Imaging, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China.
2. Department of Nephrology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China.
3. Department of Neurosurgery, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, P. R. China.

✉ Corresponding authors: Zhigang Wang, E-mail: 303507cqmu.edu.cn; Qunxia Zhang, E-mail: 300771cqmu.edu.cn.

Abstract

Photodynamic therapy (PDT) efficacy in cancer cells is affected by sub-physiological hypoxia caused by dysregulated and “chaotic” tumor microvasculature. However, current traditional O₂-replenishing strategies are undergoing their own intrinsic deficiencies. In addition, resistance mechanisms activated during PDT also lead the present situation far from satisfactory.

Methods: We propose a nitric oxide (NO)-based theranostic nanoplatform by using biocompatible poly-lactic-co-glycolic acid nanoparticles (PLGA NPs) as carriers, in which the outer polymeric layer embeds chlorin e6 (Ce6) and incorporates L-Arginine (L-Arg). This nanoplatform (L-Arg@Ce6@P NPs) can reduce hyperactive O₂ metabolism of tumor cells by NO-mediated mitochondrial respiration inhibition, which should raise endogenous O₂ tension to counteract hypoxia. Furthermore, NO can also hinder oxidative phosphorylation (OXPHOS) which should cause intracellular adenosine triphosphate (ATP) depletion, inhibiting tumor cells proliferation and turning cells more sensitive to PDT.

Results: When the L-Arg@Ce6@P NPs accumulate in solid tumors by the enhanced permeability and retention (EPR) effect, locally released L-Arg is oxidized by the abundant H₂O₂ to produce NO. In vitro experiments suggest that NO can retard hypoactive O₂ metabolism and save intracellular O₂ for enhancing PDT efficacy under NIR light irradiation. Also, lower intracellular ATP hinders proliferation of DNA, improving PDT sensitization. PDT phototherapeutic efficacy increased by combining these two complementary strategies in vitro/in vivo.

Conclusion: We show that this NO-based nanoplatform can be potentially used to alleviate hypoxia and sensitize tumor cells to amplify the efficacy of phototherapy guided by photoacoustic (PA) imaging.

Keywords: photodynamic therapy, hypoxia relief, mitochondrial respiration, adenosine triphosphate, nitric oxide

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