Squaraine‐Doped Functional Nanoprobes: Lipophilically Protected Near‐Infrared Fluorescence for Bioimaging

Abstract

Hydrophobically stabilized near‐IR fluorescence from self‐assembled nanoprobes composed of amphiphilic poly(maleic anhydride‐alt‐octadec‐1‐ene) (PMAO) and lipophilized squaraine dopants is reported. From comparative studies with varying lipophilicity of squaraine dyes as well as of nanoparticulate polymer matrices, it is found that dual protection by simultaneous lipophilization of the dye‐polymer pair greatly improves the chemical stability of labile squaraine dyes, to produce efficient NIR fluorescence in physiological aqueous milieux. The surface properties of negatively charged PMAO nanoparticles are readily modified by coating with an amine‐rich cationic glycol chitosan with biofunctionality. Efficient cellular imaging and in vivo sentinel lymph node mapping with size and surface‐controlled nanoprobes demonstrate that lipophilic dual protection of NIR fluorescence and the underlying functional nanoprobe approach hold great potential for bioimaging applications.

Fluorescent Polymer Nanoparticles Based on Dyes: Seeking Brighter Tools for Bioimaging

“…The same observations were made for the other dyes. Hydrophobically modified squaraine dyes were encapsulated in 30–40 nm NPs made with the amphiphilic polymer poly(maleic anhydride‐alt‐octadec‐1‐ene) (C18PMH) . At 0.5 wt% loading the dye showed a quantum yield of 25%.…”

“…Positively charged particles showed the highest cellular uptake and also the highest retention especially for NPs ≥ 100 nm. This is in agreement with other studies that showed, for example, higher cellular uptake of PMAO based NPs coated with the polycation chitosan . To improve internalization, fusogenic peptides were grafted to the particle surface, as for instance TAT peptides.…”

Polymethine Dyes in Hybrid Photovoltaics: Structure–Properties Relationships

“…Polymethine dyes were used for the first time in 1873 by Vogel1 to sensitize silver halide materials and, since the early 1920s, these compounds were historically applied in imaging and recording, photographic film development, bioimaging, and printing 2–5. Nowadays, this class of dyes still elicits much interest in different research fields, including ion and molecular sensors,6,7 nonlinear optics,8,9 photodynamic therapeutical applications (PDT),10–12 organic photovoltaics (OPV),13–15 and dye‐sensitized solar cells (DSCs) 16,17…”

Towards amorphous solution-processed small-molecule photovoltaic cells by design

“…[41][42][43][44] While squaraines typically yield lower conversion efficiencies than oligothiophene donors, their synthesis is typically more costefficient and requires fewer synthetic steps. Because the condensation of squaric acid with tertiary anilines typically give modest yields, 45 squarylium cyanine derivatives can be readily accessed by the condensation of squaric acid with 2,3,3-trimethylindolenine or 2-methylbenzothiazole derivatives in significantly higher yields. 46 For this reason, a symmetrical squarylium cyanine dye bearing 2-hydroxyethyl chains to allow further substitution was used to maximize synthetic efficiency.…”