β-Cyclodextrin as a photosensitizer carrier: effect on photophysical properties and chemical reactivity of squaraine dyes

Arun, Kalliat T. ; Jayaram, Dhanya T. ; Avirah, Rekha R. ; Ramaiah, Danaboyina (2011) β-Cyclodextrin as a photosensitizer carrier: effect on photophysical properties and chemical reactivity of squaraine dyes The Journal of Physical Chemistry B, 115 (21). pp. 7122-7128. ISSN 1089-5647

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Official URL: http://pubs.acs.org/doi/abs/10.1021/jp201784b

Related URL: http://dx.doi.org/10.1021/jp201784b

Abstract

With the objective of understanding the utility of β-cyclodextrin (β-CD) as a carrier system, we have investigated its interactions with a few near-infrared absorbing squaraine dyes (i.e., 1a,b and 2a,b) through absorption and steady-state and time-resolved fluorescence techniques. The addition of β-CD to the phloroglucinol dyes 1a,b resulted in a significant bathochromic shift in absorption, together with a ca. 1.5-2.5-fold enhancement in fluorescence intensity, whereas for the aniline-based dyes 2a,b, a hypsochromic shift in the absorption and a ca. 5-12-fold fluorescence enhancement were observed in a 10% (v/v) ethanol/water mixture. Benesi-Hildebrand analysis showed that both the dyes 1a,b and 2a,b form 2:1 stoichiometric complexes with β-CD. The complex formation was confirmed by competitive binding analysis employing adamantyl-1-carboxylic acid (ACA) and adamantyl-1-ammonium chloride (ADAC). The displacement of the dyes 1a,b and 2a,b from the [dye-β-CD] complex by ADAC and ACA unambiguously establishes the encapsulation of these dyes in the hydrophobic nanocavity of β-CD. Uniquely, the formation of the inclusion complexes with β-CD provides unusual protection from nucleophilic attack by aminothiols such as cysteine and glutathione for dyes 1a,b, whereas negligible protection was observed for dyes 2a,b. These results demonstrate the substituent-dependent encapsulation of potentially useful squaraine dyes in β-CD, thereby indicating its potential as a carrier system for the squaraine dyes 1a,b useful in photodynamic therapy.

Item Type:Article
Source:Copyright of this article belongs to American Chemical Society.
ID Code:63625
Deposited On:29 Sep 2011 06:35
Last Modified:29 Sep 2011 06:35

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