Proceedings Article | 13 March 2024
Sijia Liu, Jonathan Lindsey, Masahiko Taniguchi
KEYWORDS: Fluorophores, Absorption, Fluorescence, Nanoparticles, Magnesium, Polymers, Quantum numbers, Design, Absorption spectrum, Solubility
Water-soluble chlorin–dextran conjugates with a range of chlorin / dextran loading have been prepared to investigate the change in brightness as a function of loading. A polydisperse amino-dextran (~110,000 Da) was employed that consists of ~600 dextran units and ~24 amino-dextran units (3.8% degree of substitution). A synthetic chlorin is substituted with a single-junction water-solubilization group (comprised of three short, monodisperse PEG groups attached at the 2,4,6- positions of an aryl group) at the 10-position, a bioconjugatable phenylpropanoic acid group at the 15-position, and a gemdimethyl group in the reduced ring characteristic of the chlorin chromophore. The synthetic chlorin employed herein is a bioinspired analogue of chlorophyll a, which itself is Nature’s preeminent advanced functional dye. Joining of the chlorin to the dextran was achieved by amide bond formation upon N-hydroxysuccinimidyl activation of the chlorin. Loading numbers of 2.1, 2.7, 6.8, and 7.5 chlorins per dextran were obtained. The chlorin–dextran conjugates in water showed absorption and fluorescence spectra essentially identical to those of the monomeric chlorin. Among the chlorin–dextran conjugates, the brightness (fluorescence quantum yield per dextran molecule) reached ~5-times that of the corresponding chlorin monomer. Taken together, the results show the utility of combining hydrophilic fluorophores with a hydrophilic scaffold for photosciences applications in aqueous solution, yet also highlight the need for improved scaffolds (e.g., structural regularity, functional group diversity, conformational rigidity, monodispersity, water-solubility, built-in chromophores for ratiometric analyses) for development of materials with higher performance.
