Self-Assembly of Fluorescent Inclusion Complexes in Competitive Media Including the Interior of Living Cells

Abstract

Anthracene-containing tetralactam macrocycles are prepared and found to have an extremely high affinity for squaraine dyes in chloroform (log Ka = 5.2). Simply mixing the two components produces highly fluorescent, near-infrared inclusion complexes in quantitative yield. An X-ray crystal structure shows the expected hydrogen bonding between the squaraine oxygens and the macrocycle amide NH residues, and a high degree of cofacial aromatic stacking. The kinetics and thermodynamics of the assembly process are very sensitive to small structural changes in the binding partners. For example, a macrocycle containing two isophthalamide units associates with the squaraine dye in chloroform 400,000 times faster than an analogous macrocycle containing two 2,6-dicarboxamidopyridine units. Squaraine encapsulation also occurs in highly competitive media such as mixed aqueous/organic solutions, vesicle membranes, and the organelles within living cells. The highly fluorescent inclusion complexes possess emergent properties; that is, as compared to the building blocks, the complexes have improved chemical stabilities, red-shifted absorption/emission maxima, and different cell localization propensities. These are useful properties for new classes of near-infrared fluorescent imaging probes.

Preparation, characterization, and pharmacokinetics study of capsaicin via hydroxypropyl-beta-cyclodextrin encapsulation

“…The UV absorption spectrum demonstrated that clathration has occurred between HP-b-CD and CAP. In addition, a red shift was observed at the maximum absorption wavelength, which is the most common phenomenon in inclusion complex (Gassensmith et al, 2007;Zhou et al, 2009). The similar IR spectra (Figure 3) of HP-b-CD and inclusion complex indicate the formation of new phase between CAP and HPb-CD (Bernard et al, 2012), and the DSC-thermograms (Figure 4) demonstrated that a new phase which is different from the other three substances has been formed (Velasco et al, 2004).…”

Photoluminescent energy transfer from poly(phenyleneethynylene)s to near‐infrared emitting fluorophores

“…[71][72][73] Squaraines have also been utilized extensively for biological imaging. [74][75] The absorption and fluorescence maxima of fluorophores in spin-cast PMMA films and their extinction coefficients a at their absorption maxima. Second, the energy transfer between the conjugated polymer and the fluorophores was quantified by measuring the fractional quenching of donor emission (E exp ) as in Equation…”

“…This NIR-emitting compound is particularly intriguing, as the ester moiety can be readily functionalized [84][85] and utilized for biological applications such as protein labeling. 75 Similarly, NIR terrylene fluorophores function as efficient energy acceptors in thin film blends with polymer 1 (Figure 2K-M). Unsubstituted terrylene diimide 7a displays a 46-fold amplification of fluorescence from polymer excitation compared to direct fluorophore excitation, which is similar to the amplification observed for the substituted compounds 7b and 7c.…”

Photophysical Characterization and BSA Interaction of Direct Ring Carboxy Functionalized Symmetrical squaraine Dyes

“…The unique chemical and physical properties of squaraine dyes find their versatile applications in the area as NIR fluorescent probes, environmental sensors [6], molecular sensors [7][8], bio imaging and biochemical labelling [9][10] which have gathered huge attentions from the scientific community.…”