Scope and Limitations of Surface Functional Group Quantification Methods: Exploratory Study with Poly(acrylic acid)-Grafted Micro- and Nanoparticles

Abstract

The amount of grafted poly(acrylic acid) on poly(methyl methacrylate) micro- and nanoparticles was quantified by conductometry, (13)C 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.

Palladium-mediated bioorthogonal conjugation of dual-functionalised nanoparticles and their cellular delivery

“…Quantitative yields were not achieved presumably due to the distribution of the boronic acid groups between the particle's "surface" and "interior" with coupling to the latter increasingly more difficult due to the steric demands. 27 These yields are similar to the well established Cu-catalysed 35 click chemistry mediated conjugation. Recently, it was shown that the yield for surface modifications of azide-functionalised nanoparticles with alkyne modified fluorescein by Cu-catalysed click chemistry was dependent on the polymerisation process, surfactants used and accessible azide groups.…”

Hydroxy-Terminated Conjugated Polymer Nanoparticles Have Near-Unity Bright Fraction and Reveal Cholesterol-Dependence of IGF1R Nanodomains

“…29,30 Nanoparticles are conventionally functionalized through surface amines or carboxyls 29,31 but for QDs this surface charge promotes nonspecific interactions with biomolecules and cells. 29,32 For Pdots, these charged sites for attachment are generally linked to an amphiphilic PEG polymer 24 or a PEG–phospholipid coating.…”

Effect of immobilized collagen type IV on biological properties of endothelial cells for the enhanced endothelialization of synthetic vascular graft materials

“…The uptake amount of TBO in 5% (v/v) AAc with a 10 kGy irradiation dose was 20.32 ± 5.45 M/cm 2 , which was similar to that observed in a PLCL film experiment (16.83 ± 11.49 M/cm 2 ). According to the report that one TBO molecule can bind to 3.4 ± 0.2 carboxyl groups, the amount of carboxyl groups on the nanofibers that reacted with 5% (v/v) AAc at 10 kGy is approximately 11 M/cm 2 [32]. The stability of grafted AAc is shown in Fig.…”