Versatile photosensitizers for photodynamic therapy at infrared excitation

Abstract

A new type of photosensitizers used in photodynamic therapy, which is based on photon upconverting nanoparticles, is reported. These photosensitizers are excitable with infrared irradiation, which has several times larger tissue penetration depth than the currently available ones. They are brought close to the target cancer cells through antigen-antibody interaction with good specificity and versatility. The design is also flexible in that various photosensitive molecules can be potentially adopted into the design. Results from in vitro experiments demonstrate their promise of becoming the next generation photodynamic therapy drugs.

Figure 1

Schematic of the design of the versatile photosensitizer based on PUNPs. Dimensions not drawn to scale.

Figure 2

(a) Absorbance spectrum of Merocyanine 540. (b) Emission spectrum of PUNPs used in this study, excited by a 974 nm laser.

Figure 3

Emission spectrum of ADPA, excited at 374 nm. (b) Change of normalized intensity of ADPA’s emission peak at 402 nm over time, when the mixture containing ADPA and M-540-coated PUNPs was irradiated by a 974 nm laser. The line represents the fitting of the data points, using the listed equation with correlation coefficient R².

Figure 4

(a) MCF-7/AZ cells incubated with Trypan Blue and antibody-functionalized M-540-coated PUNPs modified with antibody on surface. (b) MCF-7/AZ cells in (a) after 974 nm laser irradiation for 36 minutes. (c) Optical image of MCF-7/AZ cells incubated with PI and M-540-coated PUNPs modified with antibody on surface. (d) Fluorescence image of MCF-7/AZ cells in (c) before 974 nm laser irradiation. (e) Fluorescence image of MCF-7/AZ cells in (c) after 974 nm laser irradiation for 43 minutes.