Theranostic Applications of Near-Infrared Cyanine Dyes

Near-infrared cyanine dyes have emerged as versatile platforms for simultaneous diagnosis and treatment of disease, a concept known as theranostics. Their strong absorption in the NIR window allows deep tissue imaging with minimal background autofluorescence, while tailored chemical modifications confer water solubility, photostability and selective accumulation in pathological sites. By varying the polymethine chain length and incorporating functional groups such as halogens, quaternary ammoniums or pH-sensitive moieties, researchers have engineered agents that switch between fluorescence and heat or reactive oxygen species generation. These multifunctional probes enable real-time visualisation of tumour margins during surgery, targeted photothermal ablation of malignant cells and controlled photodynamic therapy. Advances in nanoparticle conjugation and protein labelling strategies further extend the utility of cyanine dyes to multimodal imaging platforms and organelle-specific delivery, paving the way for precision interventions across cancer and other diseases.

Research from Nature Portfolio

Recent studies have introduced a pH-responsive heptamethine cyanine probe that exhibits broad absorption between 820 and 950 nm and generates high levels of singlet oxygen upon irradiation around 850 nm. Protonation under acidic conditions found in tumour microenvironments enhances intramolecular charge transfer, triggering efficient photodynamic therapy against hepatocellular carcinoma cells while sparing normal tissues and demonstrating efficacy in deep-seated tumour models. Another key development is the integration of a heptamethine cyanine dye with iron oxide nanoparticles to yield a dual-modality agent for magnetic resonance imaging and NIR fluorescence. This construct shows preferential tumour accumulation, allows high-resolution anatomical and optical imaging, and, under NIR irradiation, elicits complete tumour regression in preclinical models through photothermal effects.

Theranostic Applications of Near-Infrared Cyanine Dyes publication trend

The graph below shows the total number of articles in theranostic applications of near-infrared cyanine dyes across all publications each year (not limited to Nature Index journals).

Technical terms

Theranostics: Integration of diagnostic imaging and therapy into a single platform to enable personalised treatment planning and monitoring.

Near-infrared (NIR): Electromagnetic spectrum region (750–1700 nm) offering deep tissue penetration and low autofluorescence for biomedical imaging.

Cyanine dye: A class of polymethine dyes featuring conjugated double bonds, tunable spectral properties and high molar extinction coefficients used in fluorescence imaging and therapy.

Photodynamic therapy (PDT): Treatment modality relying on light-activated photosensitisers to generate cytotoxic reactive oxygen species, primarily singlet oxygen, for targeted cell death.

Photothermal therapy (PTT): Intervention using light-absorbing agents to convert photon energy into heat, inducing hyperthermia and necrosis in pathological tissue.

Fluorescence quantum yield: Ratio of emitted to absorbed photons by a fluorophore, indicating its brightness and efficiency in imaging applications.

Singlet oxygen: Highly reactive form of molecular oxygen generated in PDT that induces oxidative damage to cellular components.

References

1. A mitochondrion-targeted cyanine agent for NIR-II fluorescence-guided surgery combined with intraoperative photothermal therapy to reduce prostate cancer recurrence. Journal of Nanobiotechnology (2024).
2. Near-Infrared Fluorescent pH Responsive Probe for Targeted Photodynamic Cancer Therapy. Scientific Reports (2020).
3. Near-Infrared Heptamethine Cyanine Based Iron Oxide Nanoparticles for Tumor Targeted Multimodal Imaging and Photothermal Therapy. Scientific Reports (2017).
4. Potential of Cyanine Derived Dyes in Photodynamic Therapy. Pharmaceutics (2021).
5. Site-Specific Labeling of Proteins with Near-IR Heptamethine Cyanine Dyes. Molecules (2018).