Abstract
Porphyrins, especially the 5,10,15,20-tetrakis(4-N-methylpyridyl) porphyrin (TMPyP), are well-accepted as photosensitizers due to strong absorption from visible to near-infrared region, good singlet oxygen quantum yields as well as chemical versatility, all of which can be further modulated through planned supramolecular strategies. In this study, we report the construction of supramolecular nanorods of TMPyP dye/drug with captisol [sulfobutylether-β-cyclodextrin (SBE7βCD)] macrocycle through host-guest interaction. The availability of four cationic N-methylpyridyl groups favors multiple binding interaction with the captisol host, building an extended supramolecular assembly of captisol and TMPyP. In addition to the spectroscopic characterizations for the assembly formation, the same has been pictured in SEM and FM images as nanorods of ~10 μm in length or more. Complexation of TMPyP has brought out beneficial features over the uncomplexed TMPyP dye; enhanced singlet oxygen yield, improved photostability, and better photosensitizing effect, all supportive of efficient photodynamic therapy activity. The Captisol:TMPyP complex displayed enhanced antibacterial activity toward E. coli under white light irradiation as compared to TMPyP alone. Cell viability studies performed in lung carcinoma A549 cells with light irradiation documented increased cytotoxicity of the complex toward the cancer cells whereas reduced dark toxicity is observed toward normal CHO cells. All these synergistic effects of supramolecular nanorods of Captisol-TMPyP complex make the system an effective photosensitizer and a superior antibacterial and antitumor agent.
Highlights
IntroductionThe specific criteria for a good photosensitizer is that it should show strong absorption with a high extinction coefficient in the red/near infrared region of the electromagnetic spectrum (600–850 nm) and should have longer excited state lifetime, high photostability, high singlet oxygen quantum yield and low dark toxicity (Lovell et al, 2010)
The specific criteria for a good photosensitizer is that it should show strong absorption with a high extinction coefficient in the red/near infrared region of the electromagnetic spectrum (600–850 nm) and should have longer excited state lifetime, high photostability, high singlet oxygen quantum yield and low dark toxicity (Lovell et al, 2010). Porphyrins and their derivatives comprise of several properties, such as absorption in the wavelength range 350–800 nm, phototoxic upon light irradiation and singlet oxygen generation, low dark toxicity which render them preferential candidates as photosensitizers (Vermathen et al, 2013)
The aggregation-induced/intramolecular charge transfer fluorescence self-quenching of TMPyP is largely suppressed in their aggregates by the bulky captisol host that are non-covalently attached on the porphyrin aromatic rings
Summary
The specific criteria for a good photosensitizer is that it should show strong absorption with a high extinction coefficient in the red/near infrared region of the electromagnetic spectrum (600–850 nm) and should have longer excited state lifetime, high photostability, high singlet oxygen quantum yield and low dark toxicity (Lovell et al, 2010) Porphyrins and their derivatives comprise of several properties, such as absorption in the wavelength range 350–800 nm, phototoxic upon light irradiation and singlet oxygen generation, low dark toxicity which render them preferential candidates as photosensitizers (Vermathen et al, 2013). We have shown efficient interaction of TMPyP with single-strand DNA homopolymers, whereas, (dG) DNA significantly quenches the fluorescence intensity of porphyrin through photo-induced electron transfer from dG to TMPyP (Dutta Choudhury et al, 2014)
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