TY - JOUR A1 - Hennig, Andreas A1 - Borcherding, H. A1 - Jäger, Christian A1 - Hatami, Soheil A1 - Würth, Christian A1 - Hoffmann, Angelika A1 - Hoffmann, Katrin A1 - Thiele, T. A1 - Schedler, U. A1 - Resch-Genger, Ute T1 - Scope and limitations of surface functional quantification methods: exploratory study with poly(acrylic acid)-grafted micro- and nanoparticles N2 - The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, 13C solid-state NMR, fluorophore labeling, a supramolecular assay based on high-affinity binding of cucurbit[7]uril, and two colorimetric assays based on toluidine blue and nickel complexation by pyrocatechol violet. The methods were thoroughly validated and compared with respect to reproducibility, sensitivity, and ease of use. The results demonstrate that only a small but constant fraction of the surface functional groups is accessible to covalent surface derivatization independently of the total number of surface functional groups, and different contributing factors are discussed that determine the number of probe molecules which can be bound to the polymer surface. The fluorophore labeling approach was modified to exclude artifacts due to fluorescence quenching, but absolute quantum yield measurements still indicate a major uncertainty in routine fluorescence-based surface group quantifications, which is directly relevant for biochemical assays and medical diagnostics. Comparison with results from protein labeling with streptavidin suggests a porous network of poly(acrylic acid) chains on the particle surface, which allows diffusion of small molecules (cutoff between 1.6 and 6.5 nm) into the network. KW - Polymers KW - Surface groups KW - Quantification KW - Fluorescence PY - 2012 U6 - https://doi.org/10.1021/ja302649g SN - 0002-7863 SN - 1520-5126 VL - 134 IS - 19 SP - 8268 EP - 8276 PB - American Chemical Society CY - Washington, DC AN - OPUS4-26002 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -