J Breast Cancer.  2014 Mar;17(1):18-24.

Microgel-Encapsulated Methylene Blue for the Treatment of Breast Cancer Cells by Photodynamic Therapy

• Khanal A
• Bui MP
• Seo SS

Abstract

PURPOSE
Photodynamic therapy (PDT) is gaining increasing recognition for breast cancer treatment because it offers local selectivity and reduced toxic side effects compared to radiotherapy and chemotherapy. In PDT, photosensitizer drugs are loaded in different nanomaterials and used in combination with light exposure. However, the most representative issue with PDT is the difficulty of nanomaterials to encapsulate anticancer drugs at high doses, which results in low efficacy of the PDT treatment. Here, we proposed the development of the poly(N-isopropylacrylamide) (PNIPAM) microgel for the encapsulation of methylene blue, an anticancer drug, for its use as breast cancer treatment in MCF-7 cell line.
METHODS
We developed biocompatible microgels based on nonfunctionalized PNIPAM and its corresponding anionically functionalized PNIPAM and polyacrylic acid (PNIPAM-co-PAA) microgel. Methylene blue was used as the photosensitizer drug because of its ability to generate toxic reactive oxygen species upon exposure to light at 664 nm. Core PNIPAM and core/shell PNIPAM-co-PAA microgels were synthesized and characterized using ultraviolet-visible spectroscopy and dynamic light scattering. The effect of methylene blue was evaluated using the MCF-7 cell line.
RESULTS
Loading of methylene blue in core PNIPAM microgel was higher than that in the core/shell PNIPAM-co-PAA microgel, indicating that electrostatic interactions did not play an important role in loading a cationic drug. This behavior is probably due to the skin layer inhibiting the high uptake of drugs in the PNIPAM-co-PAA microgel. Core PNIPAM microgel effectively retained the cationic drug (i.e., methylene blue) for several hours compared to core/shell PNIPAM-co-PAA and enhanced its photodynamic efficacy in vitro more than that of free methylene blue.
CONCLUSION
Our results showed that the employment of core PNIPAM and core/shell PNIPAM-co-PAA microgels enhanced the encapsulation of methylene blue. Core PNIPAM microgel released the drug more slowly than did core/shell PNIPAM-co-PAA, and it effectively inhibited the growth of MCF-7 cells.

Keyword

Breast neoplasms; Methylene blue; Photochemotherapy; Poly(N-isopropylacrylamide)

MeSH Terms

Breast Neoplasms*
Breast*
Drug Therapy
Employment
MCF-7 Cells
Methylene Blue*
Nanostructures
Photochemotherapy*
Radiotherapy
Reactive Oxygen Species
Skin
Spectrum Analysis
Methylene Blue
Reactive Oxygen Species

Figure

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  Figure 1 Dependence of hydrodynamic radius of nonfunctionalized poly(N-isopropylacrylamide) on temperature in 10 mM phosphate buffer (▓) and deionized (DI) water (▒) at pH 7.4.

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  Figure 2 Dependence of hydrodynamic radius of poly(N-isopropylacrylamide) and polyacrylic acid microgel in phosphate buffer pH 7.4 (▓) and pH 3 (▒).

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  Figure 3 Release of methylene blue from functionalized of poly(N-isopropylacrylamide) and polyacrylic acid microgel at 37℃ (▓) and 25℃ (▒) in phosphate buffer, pH 7.4.

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  Figure 4 Release of methylene blue from non-functionalized of poly(N-isopropylacrylamide) and polyacrylic acid microgel at 37℃ (▓) and 25℃ (▒) in phosphate buffer, pH 7.4.

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  Figure 5 Comparison of methylene blue release from nonfunctionalized poly(N-isopropylacrylamide) (PNIPAM) (▓) and functionalized PNIPAM and polyacrylic acid (PNIPAM-co-PAA) (▴) microgel at 37℃.

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  Figure 6 Cell viability of MCF-7 against free methylene blue (MB), loaded MB in nonfunctionalized poly(N-isopropylacrylamide) (PNIPAM). The concentration of MB is 0.6 µM.

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  Figure 7 Cell viability of MCF-7 against free methylene blue (MB), loaded MB in nonfunctionalized poly(N-isopropylacrylamide) (PNIPAM). The concentration of MB is 25 µM.

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