The relative brightness of PEG lipid-conjugated polymer nanoparticles as fluid-phase markers in live cells

TitleThe relative brightness of PEG lipid-conjugated polymer nanoparticles as fluid-phase markers in live cells
Publication TypeJournal Article
Year of Publication2012
AuthorsFernando, L. P., Kandel P. K., Ackroyd P. C., and Christensen K. A.
JournalAnal Bioanal Chem
Volume404
Pagination3003-14
Date PublishedDec
ISBN Number1618-2650 (Electronic)<br/>1618-2642 (Linking)
Accession Number23052882
Keywords*Quantum Dots, Animals, Cell Line, Cell Survival, Dextrans/analysis/chemistry, Fluorenes/analysis/*chemistry, fluorescence, Fluorescent Dyes/analysis/*chemistry, Macrophages/*cytology, Mice, Microscopy, Fluorescence, Nanoparticles/analysis/*chemistry, Pinocytosis, Polyethylene Glycols/analysis/*chemistry, Polymers/analysis/*chemistry
Abstract

While conjugated polymer nanoparticles (CPNs) have been widely touted as ultra-bright labels for biological imaging, no direct comparative measurements of their intracellular brightness have been reported. Simple in vitro comparisons are not definitive since fluorophore brightness in vitro may not correspond with intracellular brightness. We have compared the fluorescence brightness of J774A.1 cells loaded with 24 nm methoxy-capped 2,000 M(r) polyethylene glycol lipid PFBT nanoparticles (PEG lipid-PFBT CPNs) to cells loaded with carboxy-functionalized quantum dots (Qdots) or a dextran-linked small molecule organic dye, Alexa Fluor 488 dextran (AF488-dex). Under conditions likely to be used for biological imaging or flow cytometry, these CPNs are 175x brighter than Qdots and 1,400x brighter than AF488-dex in cells. Evaluation of the minimum incubation concentration required for detection of nanoparticle fluorescence with a commercial flow cytometer indicated that the limit of detection for PEG lipid-PFBT CPNs was 19 pM (86 ppb), substantially lower than values obtained for Qdots (980 pM) or AF488-dex (11.2 nM). Investigation of the mechanism of cellular uptake of the three fluid-phase labels indicates that these particles are passively taken into macrophage cells via macropinocytosis without interaction with cell surface receptors, and ultimately localize in lysosomes. In addition, no cytotoxicity could be observed at any of the CPN concentrations tested. Together, these data suggest that these CPNs are appropriate and attractive candidates as fluid-phase markers with significantly greater fluorescence brightness than existing dyes or nanoparticles. We expect that these CPNs will find application in both imaging and flow cytometry.

Short TitleThe relative brightness of PEG lipid-conjugated polymer nanoparticles as fluid-phase markers in live cells