The Contrasting Recognition Behavior of β‐Cyclodextrin and Its Sulfobutylether Derivative towards 4′,6‐Diamidino‐2‐phenylindole

Abstract

The noncovalent interactions between 4', 6-diamidino-2-phenylindole (DAPI) and sulfobutylether β-cyclodextrin (SBE7β-CD) are evaluated by using photochemical measurements and compared with that of native β-CD. Contrasting recognition behavior and intriguing modulations in the photochemical behavior of DAPI were observed. In particular, a large enhancement in the fluorescence emission and excited-state lifetime were seen upon binding to SBE7β-CD, with the SBE7β-CD inclusion complex being approximately 1000 times stronger than that of β-CD. The ensuing fluorescence "turn on" was demonstrated to be responsive to chemical stimuli, such as metal ions and adamantylanmine (AD). Upon addition of Ca(2+)/AD, nearly quantitative dissociation of the complex was established to regenerate the free dye and result in fluorescence "turn off". The SO3(-) groups are believed to be critical for the strong and selective binding of the chromophore and the stimuli-responsive tuning. This is as an important design criterion for the optimization of host-guest properties through supramolecular association, which is relevant for drug-delivery applications.

Ultra‐Bright Rhodamines with Sulfobutylether‐β‐Cyclodextrin: A Viable Supramolecular Dye Laser in Aqueous Medium

“…[18] In an earlier work, we have established stimuli-responsive assembly of DAPI with SBE 7 bCD for on-off fluorescent switch and controlled drug delivery applications. [36] Of late, utilizing the recognition behavior of SBE 7 bCD towards insulin and lysozyme proteins, we have demonstrated the efficient inhibition and disintegration of amyloid fibrils from these proteins and shows promising for the treatment of amyloid related diseases. [37] However, the hostguest interaction studies of SBE 7 bCD with practical laser dyes and their technological applications are hardly explored.…”

“…The binding isotherms were constructed by plotting the optical density versus SBE 7 b-CD concentration (insets of Figure 1) and is fitted with a non-linear quadratic equation for 1 : 1 complex model (Method S1, in the Supporting Information). [5,36,38,38] The binding constant (K) value is estimated as (1.6 AE 0.1) 10 4 M À1 for the SBE 7 b-CD : RhB complex and (9.5 AE 1.3) 10 3 M À1 for the SBE 7 b-CD : Rh6G complex. The moderate binding constant values indicate the involvement of both iondipole and hydrophobic interactions between SBE 7 bCD and RhB/Rh6G.…”

“…Since, SBE 7 βCD contains the same βCD core with sulfobutyl ether chains at both the portals, it carries the extended hydrophobic nature along with the stretched cavity of SBE 7 βCD . Whereas, the hydrophilic portals containing SO 3 − bearing sulfobutyl ether chains show strong interaction towards cationic guests . Due to its high water solubility and nontoxic nature, it is used as excipients in drug formulation .…”

“…The solubility is much higher than the parent βCD and other cationic receptors with similar cavity dimension such as cucurbit[7]uril (CB7) . In an earlier work, we have established stimuli‐responsive assembly of DAPI with SBE 7 βCD for on‐off fluorescent switch and controlled drug delivery applications . Of late, utilizing the recognition behavior of SBE 7 βCD towards insulin and lysozyme proteins, we have demonstrated the efficient inhibition and disintegration of amyloid fibrils from these proteins and shows promising for the treatment of amyloid related diseases .…”

“…[34] Whereas, the hydrophilic portals containing SO 3 À bearing sulfobutyl ether chains show strong interaction towards cationic guests. [36] Due to its high water solubility and nontoxic nature, it is used as excipients in drug formulation. [35] The solubility is much higher than the parent bCD and other cationic receptors with similar cavity dimension such as cucurbit [7]uril (CB7).…”