Light/pH Dual-Controlled Drug Release “Nanocontainer” Alleviates Tumor Hypoxia for Synergistic Enhanced Chemotherapy, Photodynamic Therapy, and Chemodynamic Therapy

Academic Background

In clinical cancer treatment, chemotherapy and radiotherapy have several limitations, such as drug resistance, incomplete treatment, and periodic recurrence. To overcome these drawbacks, researchers have developed various alternative strategies, including multimodal combination therapy, which can complement other therapies to improve the efficacy of tumor treatment. Photodynamic therapy (PDT) is a typical oxidative therapeutic strategy that utilizes a photo-activated photosensitizer along with ambient oxygen (O₂) to produce high levels of toxic reactive oxygen species (ROS) to kill cancer cells. Due to its noninvasive nature, rapid effect, and on-demand controllability, PDT has significant advantages in primary tumor treatment. However, the hypoxic tumor microenvironment limits the generation of sufficient ROS during PDT, thereby restricting its application in cancer treatment.

β-Lapachone (LPC) is a novel chemotherapeutic agent that inhibits tumor cell proliferation by directly interacting with topoisomerase 1. However, the ability of LPC to produce hydrogen peroxide (H₂O₂) depends on the oxygen content within the tumor. Tumor cells consume a large amount of oxygen to facilitate rapid cell proliferation, resulting in a long-term hypoxic microenvironment, which significantly limits the application of PDT and the antitumor effect of LPC. Therefore, improving the tumor’s hypoxic environment is a prerequisite to ensure the efficacy of combined treatment using PDT and chemotherapy.

Source of the Paper

This paper was co-authored by Shihe Liu, Xin Zhang, Zhimin Bai, and other researchers from multiple laboratories at Yanshan University, including the Hebei Key Laboratory of Applied Chemistry, the Hebei Key Laboratory of Nanobiotechnology, and others. The study was published online on October 19, 2024, in the journal Bio-design and Manufacturing, with the DOI 10.1007/s42242-024-00310-5.

Research Process

1. Design and Synthesis of the Nanodrug Delivery System

The researchers designed a light/pH dual-controlled drug delivery system based on a porous coordination network (PCN), named LPC@PCN@PDA/Fe³⁺-AS1411 (LPPFA). The system was constructed by loading β-lapachone (LPC) into the PCN (Mn) framework, coating its surface with polydopamine (PDA), and finally modifying it with the nucleic acid aptamer AS1411 and trivalent iron ions (Fe³⁺).

• Synthesis of PCN (Mn): PCN (Mn) was synthesized using the solvothermal method. Manganese chloride tetrahydrate (MnCl₂·4H₂O) and tetra(4-carboxyphenyl)porphyrin (TCPP) were dissolved in dimethylformamide (DMF), and acetic acid was added before reacting at 150°C for 12 hours to obtain a black precipitate.
• Loading of LPC: PCN (Mn) was mixed with LPC in ethanol, and the encapsulation efficiency and drug loading of LPC were determined by centrifugation and UV spectroscopy.
• Preparation of the PDA Coating: A PDA coating was formed on the surface of LPC@PCN through the oxidative polymerization of dopamine to prevent drug leakage during transportation.
• Modification with Fe³⁺ and AS1411: Fe³⁺ and AS1411 were sequentially modified onto the PDA surface through chelation and amide reactions to form the final LPPFA nanoparticles.

2. Characterization of Nanoparticles

The researchers characterized the morphology, size, and surface potential of the nanoparticles using transmission electron microscopy (TEM), dynamic light scattering (DLS), and UV-Vis spectroscopy. The results showed that the LPPFA nanoparticles had a uniform spherical structure with a size of approximately 160 nm, exhibiting good dispersibility and stability.

3. Evaluation of Photothermal Performance

The researchers evaluated the photothermal conversion performance of LPPFA. Under 808 nm near-infrared laser irradiation, the temperature of the LPPFA solution rapidly increased from 25°C to 52°C, demonstrating excellent photothermal conversion efficiency. Additionally, LPPFA maintained stable photothermal performance after multiple laser irradiations, indicating good photothermal stability.

4. Study of Drug Release Behavior

The researchers investigated the drug release behavior of LPPFA under different pH and laser irradiation conditions. The results showed that the release rate of LPC was significantly higher in an acidic environment (pH=5.5) than in a neutral environment (pH=7.4). Furthermore, 808 nm laser irradiation further promoted the release of LPC, indicating that LPPFA has pH- and light-dual-responsive drug release properties.

5. Evaluation of Photodynamic and Chemodynamic Performance

The researchers assessed the photodynamic and chemodynamic performance of LPPFA using the DPBF elimination method and the DCFH-DA fluorescent probe. The results showed that LPPFA could generate a large amount of ROS under 660 nm laser irradiation, and the presence of Fe³⁺ further enhanced ROS generation, indicating excellent photodynamic and chemodynamic therapeutic effects.

6. Cell Experiments

The researchers evaluated the inhibitory effect of LPPFA on tumor cells using CCK-8 assays, mitochondrial membrane potential detection, and apoptosis assays. The results showed that LPPFA significantly inhibited tumor cell proliferation and induced apoptosis under 808 nm and 660 nm laser irradiation.

7. Animal Experiments

The researchers evaluated the in vivo antitumor effect of LPPFA in a mouse cervical cancer model. The results showed that LPPFA significantly inhibited tumor growth under 808 nm and 660 nm laser irradiation, with no significant toxicity to the liver and kidney functions of the mice.

Main Results

1. Synthesis and Characterization of Nanoparticles: The LPPFA nanoparticles were successfully synthesized, and their morphology, size, and surface potential were thoroughly characterized.
2. Photothermal Performance: LPPFA exhibited excellent photothermal conversion efficiency and stability under 808 nm laser irradiation.
3. Drug Release Behavior: LPPFA achieved rapid release of LPC under acidic conditions and laser irradiation.
4. Photodynamic and Chemodynamic Performance: LPPFA generated a large amount of ROS under 660 nm laser irradiation, and the presence of Fe³⁺ further enhanced ROS generation.
5. Cell Experiments: LPPFA significantly inhibited tumor cell proliferation and induced apoptosis under 808 nm and 660 nm laser irradiation.
6. Animal Experiments: LPPFA significantly inhibited tumor growth under 808 nm and 660 nm laser irradiation, with no significant toxicity to the liver and kidney functions of the mice.

Conclusion

This study successfully developed a light/pH dual-responsive nanodrug delivery platform that effectively alleviates tumor hypoxia and achieves synergistic enhancement of PDT, CDT, and chemotherapy. The LPPFA nanoparticles exhibit excellent tumor targeting, photothermal conversion performance, and drug release properties, significantly inhibiting tumor growth with no significant toxicity to normal tissues. This research provides new insights for the development of intelligent multifunctional therapeutic nanoplatforms.

Research Highlights

1. Multimodal Combination Therapy: The LPPFA nanoparticles can simultaneously achieve synergistic effects of PDT, CDT, and chemotherapy, significantly enhancing antitumor efficacy.
2. Light/pH Dual-Responsiveness: The LPPFA nanoparticles enable rapid drug release under acidic conditions and laser irradiation, improving drug targeting and therapeutic effects.
3. Excellent Biocompatibility: The LPPFA nanoparticles exhibit no significant toxicity to normal tissues, demonstrating good biosafety.