August 14, 2025Open Access

Unveiling Theranostics: Nanocomplex-Assisted Photodynamic Eradication of Aggressive Cancer Cells and Modulation of Tumor-Associated Macrophages

ABAusteja ButkuteVilnius University EKEvelina KazlauskėVilnius Gediminas Technical University AMAgata MlynskaVilnius Gediminas Technical University

Key Points

The nanocomplex-assisted photodynamic therapy achieves effective targeting of aggressive cancer cells, while also modulating immune responses.
Therapeutic efficacy was consistent across colorectal cancer cell lines, demonstrating robust photodynamic activity and potential against variation in drug sensitivity.
Using both chlorin e6 and quantum dots, the approach enables selective switching between diagnostic and therapeutic modes under two distinct light sources.
The findings suggest potential therapeutic strategies by targeting both tumor cells and the immunosuppressive tumor microenvironment, particularly through macrophage modulation.

Abstract

Photodynamic therapy (PDT) is a promising tool that utilizes photosensitizers (PS) for two functions: cancer imaging by fluorescence (diagnostics), and treatment by the generation of reactive oxygen species (therapy). Despite its theranostic approach, the efficacy of PDT is often hampered by limited penetration of light into tissues, tumor heterogeneity, and the immunosuppressive tumor microenvironment (TME). Moreover, diagnostics and treatment are activated simultaneously, without the possibility of switching between two processes. We used photosensitizer chlorin e6 (Ce6) and luminescent quantum dots (QDs) to create a theranostic nanocomplex. Two different light sources were used (980 nm or 650 nm light) to activate either the photoluminescence of quantum dots (QDs) or the generation of singlet oxygen by Ce6. Four distinct CRC cell lines were utilized to represent tumor heterogeneity. The therapeutic efficacy of nanocomplex was assessed in CRC and tumor-associated macrophages (TAMs), a key component of the immunosuppressive TME. Immunomodulatory effects were explored by exposing resident and recruited TAM models to a conditioned medium from PDT-treated CRC cells, followed by gene expression analysis. Spectral characterization of the QDs-Ce6 nanocomplex demonstrated selective switching between diagnostic and therapeutic modes. Two-photon absorption was activated in QDs by 980 nm laser, thus broadening its excitation capabilities into the infrared region. The nanocomplex accumulated efficiently and uniformly across all CRC cell lines, regardless of their aggressiveness or drug sensitivity. The effect of nanocomplex-assisted PDT was the same among CRC cell lines, contrasting with the variable sensitivity to 5-fluorouracil. Additionally, the PDT caused M2 macrophages to lose their pro-tumor characteristics while potentiating their ability to present antigens. Additionally, M0 macrophages displayed a reduction in immunosuppressive signaling. The QDs-Ce6 nanocomplex exhibits robust photodynamic cytotoxicity and immunomodulatory potential. These findings highlight the potential of nanocomplex for targeting the aggressive type of tumor cells and the TAM.

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