title: Mutually-Reactive, Fluorogenic Hydrocyanine/Quinone Reporter Pairs for In-Solution Biosensing via Nanodroplet Association.
abstract: Mutually reactive, fluorogenic molecules are presented as a simple and novel technique for in-solution biosensing. The hypothesis behind this work was that aggregating droplets into close proximity would cause rapid mixing of their contents. To take advantage of this effect, a novel pair of fluorogenic redox molecules were designed to remain in lipid-stabilized oil droplets but mix once aggregated. First, the hydrophobic cyanine dye 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (DiI) was reduced with sodium borohydride to form a nonfluorescent analog (HDiI). Hydrophobic quinone derivatives were then screened as oxidizing agents, and it was found that p-fluoranil oxidized nonfluorescent HDiI back to fluorescent DiI. Next, HDiI and p-fluoranil were loaded into NEOBEE oil nanodroplets of average diameter 600 nm that were stabilized by a monolayer of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-polyethylene glycol (PEG), and DSPE-PEG-biotin. Addition of streptavidin caused aggregation of droplets and the appearance of red fluorescent aggregates within 30 min. Next, Nanoparticle Tracking Analysis was used to record the fluorescence of the droplets and their aggregates. By integrating the fluorescence emission of the tracked droplets, streptavidin could be detected down to 100 fM. Finally, the droplets were reformulated to sense for vascular endothelial growth factor (VEGF), a biomarker for tumor metastasis. Using anti-VEGF aptamers attached to DSPE-PEG incorporated into the nanodroplet monolayer, VEGF could also be detected down to 100 fM.
authors.affiliation: Department of Mechanical Engineering, University of Colorado Boulder , Boulder, Colorado 80309, United States.
authors.forename: Rajarshi
authors.initials: R
authors.lastname: Chattaraj
authors.affiliation: Department of Chemical and Biological Engineering. University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors.forename: Praveena
authors.initials: P
authors.lastname: Mohan
authors.affiliation: Department of Chemical and Biological Engineering. University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors.forename: Clare M
authors.initials: CM
authors.lastname: Livingston
authors.affiliation: Department of Chemical and Biological Engineering. University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors.forename: Jeremy D
authors.initials: JD
authors.lastname: Besmer
authors.affiliation: Department of Chemical and Biological Engineering. University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors.forename: Kaushlendra
authors.initials: K
authors.lastname: Kumar
authors.affiliation: Department of Chemical and Biological Engineering. University of Colorado Boulder , Boulder, Colorado 80303, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Goodwin
mesh_terms: D052157:Aptamers, Nucleotide / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D019921:Biotinylation; D005456:Fluorescent Dyes / Q000737:chemistry*; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry*; D011485:Protein Binding; D011809:Quinones / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence; D019809:Streptavidin / Q000032:analysis; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D052157:Aptamers, Nucleotide; D005456:Fluorescent Dyes; D011809:Quinones; D012996:Solutions; D042461:Vascular Endothelial Growth Factor A; D019809:Streptavidin
keywords: biomedical applications; colloids; self-assembly; sensors/biosensors; stimuli-responsive materials; vascular endothelial growth factor