Conquering the Hypoxia Limitation for Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) has aroused great research interest in recent years owing to its high spatiotemporal selectivity, minimal invasiveness, and low systemic toxicity. However, due to the hypoxic nature characteristic of many solid tumors, PDT is frequently limited in therapeutic effect. Moreover, the consumption of O2 during PDT may further aggravate the tumor hypoxic condition, which promotes tumor proliferation, metastasis, and invasion resulting in poor prognosis of treatment. Therefore, numerous efforts have been made to increase the O2 content in tumor with the goal of enhancing PDT efficacy. Herein, these strategies developed in past decade are comprehensively reviewed to alleviate tumor hypoxia, including 1) delivering exogenous O2 to tumor directly, 2) generating O2 in situ, 3) reducing tumor cellular O2 consumption by inhibiting respiration, 4) regulating the TME, (e.g., normalizing tumor vasculature or disrupting tumor extracellular matrix), and 5) inhibiting the hypoxia‐inducible factor 1 (HIF‐1) signaling pathway to relieve tumor hypoxia. Additionally, the O2‐independent Type‐I PDT is also discussed as an alternative strategy. By reviewing recent progress, it is hoped that this review will provide innovative perspectives in new nanomaterials designed to combat hypoxia and avoid the associated limitation of PDT.

Carbon Dots in Bioimaging, Biosensing and Therapeutics: A Comprehensive Review

“…Photodynamic Therapy PDT involves three key elements: A photosensitizer (PS), light and oxygen. [243][244][245] Firstly, the PS absorbs energy from light and transitions from the ground electronic state ( 0 PS) into the excited singlet state ( 1 PS*). The excited PS ( 1 PS*) then decays back to 0 PS via fluorescence, or instead 1 PS* can undergo an intersystem crossing (ISC) process to form a triplet state ( 3 PS*).…”

Emerging Prospects of Nanozymes for Antibacterial and Anticancer Applications

“…For example, photodynamic therapy (PDT) of cancer relies heavily on an ample supply of molecular oxygen in the tumor region. Therefore, the inherent hypoxia associated with most tumors severely hampers the efficacy of PDT [ 82 ]. Tumor hypoxia can be substantially relieved by the conversion of endogenous H 2 O 2 into molecular oxygen; however, the enzyme CAT, which promotes this conversion, is also poorly present in the TME.…”

Progress of Nanomaterials in Photodynamic Therapy Against Tumor

“…They can achieve high-efficiency delivery of PSs to tumor tissues through physicochemically optimized passive targeting, ligand-modified active targeting, and stimulus-responsive release ( Zhao et al, 2021 ). Attempts have been made to overcome the unfavorable tumor microenvironment through photocatalytic oxygen production, Fenton reaction, and combination with other chemical drugs ( Wan et al, 2021 ). In this review, we first describe the composition and tumor-promoting mechanisms of the tumor microenvironment, and then introduce metal NPs, nanoliposomes, mesoporous silica NPs, dendrimers, hydrogels, polymer micelles and these creative methods to solve the problems faced by tumor PDT.…”