Amphiphilic BODIPY-Hydroporphyrin Energy Transfer Arrays with Broadly Tunable Absorption and Deep Red/Near-Infrared Emission in Aqueous Micelles

Abstract

BODIPY-hydroporphyrin energy transfer arrays allow for development of family of fluorophores featuring a common excitation band at 500 nm, tunable excitation band in deep red/near-infrared window, and tunable emission. Their biomedical applications are contingent upon retaining their optical properties in aqueous environment. Amphiphilic arrays containing PEG-substituted BODIPY and chlorins or bacteriochlorins were prepared and their optical and fluorescence properties were determined in organic solvents and aqueous surfactants. The first series of arrays contains BODIPYs with PEG substituents attached to the boron, whereas in the second series, PEG substituents are attached to the aryl at the meso positions of BODIPY. For both series of arrays, excitation of BODIPY at 500 nm results in an efficient energy transfer to and bright emission of hydroporphyrin in deep-red (640–660 nm) or near-infrared (740–760 nm) spectral windows. In aqueous non-ionic surfactants (Triton X-100 and Tween 20) arrays from the second series exhibit significant quenching of fluorescence, whereas properties of arrays from the first series are comparable to those observed in polar organic solvents. Reported arrays possess large effective Stokes shift (115 – 260 nm), multiple excitation wavelengths, and narrow, tunable deep-red/near-IR fluorescence in aqueous surfactants, and are promising candidates for a variety of biomedical-related applications.

Chlorophyll-Inspired Red-Region Fluorophores: Building Block Synthesis and Studies in Aqueous Media

“…Free base chlorins H 2 C10-PEG 6 , H 2 C12-PEG 6 , and H 2 C15-PEG 6 as well as zinc chlorins ZnC12-PEG 6 and ZnC15-PEG 6 each bear a single carboxylic acid and a tri-PEGylated aryl group attached to the chlorin 10-position. This work extends prior research in preparing PEGylated chlorins [ 15 ]; alternative approaches for installation of PEG groups in hydroporphyrins-containing arrays have been described recently by Meares et al [ 16 ]. Each PEG group consists of six ethyleneoxy units and is terminated with a methyl group.…”

BODIPY–Bacteriochlorin Energy Transfer Arrays: Toward Near-IR Emitters with Broadly Tunable, Multiple Absorption Bands

“…20 Highly efficient (> 0.90 in non-polar solvent, > 0.80 in polar solvents) energy transfer from BODIPY to hydroporphyrin was observed for each array, so that excitation of BODIPY moiety results in nearly exclusive emission of hydroporphyrin unit. Such arrays constitute a platform for development of fluorophores with a common excitation wavelength at 500 nm, and tunable, huge Stokes’ shift > 150 nm.…”

“…chlorins 19 and bacteriochlorins. 17,20 In particular, bacteriochlorins absorb strongly at 350–380 nm ( B bands), and pass 700 nm ( Q y band), and moderately between 500–550 nm ( Q x band). 21–23 Bacteriochlorins also have a relatively intensive emission band in near-IR (>700 nm) 22,23 which is exceptionally narrow (with full-width-at-half-of-maximum FWHM ~20–25 nm), and which maximum position can be broadly tuned (700–800 nm) by relatively simple structural modifications.…”

Amphiphilic Near-IR-Emitting 3,5-Bis(2-Pyrrolylethenyl)BODIPY Derivatives: Synthesis, Characterization, and Comparison with Other (Hetero)Arylethenyl-Substituted BODIPYs

“…[19][20][21][22][23] Previously, we have examined a series of amphiphilic energy transfer arrays, which utilized hydrophilic BODIPY derivatives for in vivo medicinal imaging. 24,25 We also examined BODIPY with (2,4,6-trialcoxyaryl)ethenyl substituents (2, Chart 1), which absorbs at 668 nm and functions as an excellent energy donor for bacteriochlorins. 26 However, this absorption and emission maxima are sub-optimal for in vivo application, therefore we envisioned, that 2-pyrrolylethenyl substituents should provide a desirable batochromic shift, and nitrogen on pyrrole moiety should provide a convenient synthetic handle to attach hydrophilic group.…”