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Evaluation of four new carbocyanine dyes for photodynamic therapy with lasers
G S Lipshutz1, D J Castro, R E Saxton
1Division of Head and Neck Surgery, University of California, Los Angeles, School of Medicine 90024.
Abstract:
The search for improved photosensitizers for laser phototherapy of malignancies has led to the examination of a new group of carbocyanine dyes as effective fluorochromes. In this study, four carbocyanine dyes with different absorption maxima of 483 nm [DiOC6(3)], 545.5 nm (DiIC5(3)], 556.6 nm [DiSC5(3)], and 651.0 nm [DiSC3(5)] were tested in vitro. The kinetics of uptake and toxicity of these four dyes were assessed for P3 human squamous cell carcinoma, HT29 colon carcinoma, M26 melanoma, and TE671 fibrosarcoma cell lines at 15, 30, 45, 60, and 180 minutes after exposure with each dye. After sensitization with DiOC6(3), the P3 and M26 cell lines were also tested for phototherapy by treatment with 488-nm light from an argon laser. The results showed that these four carbocyanine dyes had rapid and significant uptake by the carcinoma cell lines with no toxicity at concentrations < 0.1 micrograms/mL. Nontoxic DiOC6(3) levels in sensitized tumor cells after laser phototherapy resulted in approximately 85% inhibition of P3 and approximately 95% inhibition of M26 cell lines by MTT assays. The results suggest that these carbocyanine dyes can be used for tumor photosensitization and wavelength-matched laser photodynamic therapy. Further in vivo studies will be necessary to define the clinical potential of carbocyanine dyes as tumor-targeting agents for phototherapy of cancer.
Insights
New carbocyanine dyes show promise as photosensitizers for cancer laser phototherapy. These dyes are rapidly absorbed by tumor cells with no toxicity, leading to significant cancer cell inhibition after laser treatment.
Area of Science:
- Photodynamic Therapy
- Carcinogenesis
- Biomedical Optics
Background:
- The development of effective photosensitizers is crucial for advancing laser phototherapy in cancer treatment.
- Carbocyanine dyes are being investigated as potential fluorochromes for this application.
Purpose of the Study:
- To evaluate the in vitro uptake kinetics and toxicity of four carbocyanine dyes with varying absorption maxima.
- To assess the efficacy of DiOC6(3) for laser phototherapy in specific cancer cell lines.
Main Methods:
- Four carbocyanine dyes (DiOC6(3), DiIC5(3), DiSC5(3), DiSC3(5)) were tested on human squamous cell carcinoma (P3), colon carcinoma (HT29), melanoma (M26), and fibrosarcoma (TE671) cell lines.
- Uptake and toxicity were measured at multiple time points.
- Sensitized P3 and M26 cells were treated with 488-nm argon laser light, and cell viability was assessed using MTT assays.
Main Results:
- Carbocyanine dyes exhibited rapid and significant uptake by carcinoma cell lines without toxicity at concentrations below 0.1 µg/mL.
- Laser phototherapy with DiOC6(3) resulted in approximately 85% inhibition of P3 cells and 95% inhibition of M26 cells.
- MTT assays confirmed the significant cytotoxic effect post-treatment.
Conclusions:
- Carbocyanine dyes are effective for tumor photosensitization and wavelength-matched laser photodynamic therapy.
- Further in vivo studies are warranted to explore their clinical potential as tumor-targeting agents in cancer therapy.