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Water‐Soluble Germanium(0) Nanocrystals: Cell Recognition and Near‐Infrared Photothermal Conversion Properties
Author(s) -
Lambert Timothy N.,
Andrews Nicholas L.,
Gerung Henry,
Boyle Timothy J.,
Oliver Janet M.,
Wilson Bridget S.,
Han Sang M.
Publication year - 2007
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.200600529
Subject(s) - germanium , bovine serum albumin , transmission electron microscopy , photothermal therapy , materials science , x ray photoelectron spectroscopy , analytical chemistry (journal) , nanocrystal , nuclear chemistry , chemistry , nanotechnology , chemical engineering , chromatography , silicon , engineering , metallurgy
Abstract Surfactant‐passivated germanium nanocrystals (Ge(0) NCs) 3–5 nm in diameter were synthesized and encapsulated with functionalized phospholipids to yield water‐soluble Ge(0) NCs. Upon encapsulation, the NCs retained their cubic crystalline phase and displayed good resistance to oxidation, as determined by transmission electron microscopy and X‐ray photoelectron spectroscopy. As a test of their cell compatibility, the ability of carboxyfluorescein (CF)‐labeled dinitrophenyl (DNP)‐functionalized Ge(0) NCs to crosslink dinitrophenol‐specific immunoglobulin E antibodies on the surface of mast cells (RBL‐2H3) was examined in vitro. Treatment with a multivalent DNP antigen (i.e., DNP‐Ge(0) NCs or CF‐DNP‐Ge(0) NCs) caused crosslinking of FcεRI receptors and cellular responses, which were evaluated with morphological and colorimetric assays and live‐cell fluorescence microscopy. Incubation of RBL‐2H3 cells with Ge(0) NCs for ≈24 h gave less than a 2 % increase in cell death as compared to DNP‐functionalized bovine serum albumin. When irradiated with near‐infrared (NIR) radiation ( λ exc =770 nm, 1.1 W cm −2 ) from a continuous‐wave Ti:sapphire laser, the bulk‐solution temperature of a toluene solution containing 20 mg mL −1 Ge(0) NCs increased by ≈35 °C within 5 min. Phospholipid‐encapsulated water‐soluble Ge(0) NCs at concentrations of 1.0 mg mL −1 also displayed stable photothermal behavior under repetitive and prolonged NIR laser exposures in water, to yield a temperature increase of ≈20 °C within 5 min ( λ exc =770 nm, 0.9 W cm −2 ). The photothermal efficiency of water‐soluble Ge(0) NCs compares favorably with a recent report for Au nanoshells.