# Rare-earth cerium-coordinated ICG nanoprobe for tumor hypoxia relief and intensified photodynamic therapy

## TL;DR

Researchers developed cerium-coordinated ICG nanoparticles to improve photodynamic therapy by boosting ROS production and reducing tumor hypoxia, leading to effective cancer cell death.

## Contribution

A simple, rapid method to create cerium-coordinated ICG nanoparticles that enhance PDT through dual catalytic activity and improved ROS generation.

## Key findings

- CINPs significantly enhance ICG stability and promote efficient reactive oxygen species (ROS) generation.
- Ce4+ catalyzes H2O2 decomposition to alleviate tumor hypoxia and depletes GSH to weaken antioxidant defenses.
- In hepatocellular carcinoma models, CINPs induce mitochondrial dysfunction, lipid peroxidation, and DNA damage, suppressing tumor growth.

## Abstract

Photodynamic therapy (PDT) utilizing organic photosensitizers like indocyanine green (ICG) faces several intrinsic limitations. These challenges include a propensity to aggregate, insufficient stability, and low intersystem crossing (ISC) efficiency that yields inadequate reactive oxygen species (ROS). Furthermore, the tumor microenvironment imposes additional restrictions on its efficacy. To address these challenges, we implemented a cetyltrimethylammonium bromide (CTAB)–templated metal coordination approach and rationally designed cerium(IV)-coordinated, self-assembled ICG nanoparticles (CINPs). Cooperative coordination between Ce4+ and ICG, combined with hydrophobic interactions, significantly enhances ICG stability. It also optimizes the energy gap between the lowest singlet excited state (S1) and the lowest triplet state (T1), thereby promoting ISC and equipping the system with robust ROS-generating capacity. Moreover, Ce4+ exhibits dual catalytic activity, on the one hand catalyzing the decomposition of endogenous hydrogen peroxide (H2O2) to generate oxygen and alleviate tumor hypoxia, and on the other hand oxidizing and depleting intracellular glutathione (GSH) to weaken antioxidant defenses. In a hepatocellular carcinoma model, CINPs harnessed efficient ROS production to induce mitochondrial dysfunction, lipid peroxidation (LPO), and DNA strand breaks, which collectively activated multiple cell death pathways and significantly suppressed tumor growth. Unlike nanoplatforms that require elaborate designs, complex compositions, and fine chemical synthesis, the nanoparticles developed here are assembled from a small set of reliable, clinically established materials and can be rapidly formed through a simple process in less than 30 min. Despite the streamlined preparation, CINPs effectively remodel the tumor microenvironment, induce vigorous ROS generation during treatment, and achieve potent antitumor activity via oxidative stress-related mechanisms across multiple pathways, highlighting strong translational potential and broad prospects for clinical application.

Photodynamic therapy (PDT) with indocyanine green (ICG) is limited by aggregation, poor stability, low ROS production, and TME constraints. We developed Ce4+-coordinated ICG nanoparticles (CINPs) via a simple CTAB-templated strategy within less than 30 min. Ce4+ enhances ICG stability, facilitates the generation of ISC and ROS, decomposes H2O2 to alleviate hypoxia, and depletes GSH. In hepatocellular carcinoma, CINPs induce multi-pathway cell death via ROS, thereby suppressing tumor growth.Image 1