Characterization of phthalocyanine functionalized quantum dots by dynamic light scattering, laser Doppler, and capillary electrophoresis

Abstract

In this work, we characterized different phtalocyanine-capped core/shell/shell quantum dots (QDs) in terms of stability, ζ-potential, and size at various pH and ionic strengths, by means of capillary electrophoresis (CE), and compared these results to the ones obtained by laser Doppler electrophoresis (LDE) and dynamic light scattering (DLS). The effect of the phthalocyanine metallic center (Zn, Al, or In), the number (one or four), and nature of substituents (carboxyphenoxy- or sulfonated-) of functionalization on the phthalocyanine physicochemical properties were evaluated. Whereas QDs capped with zinc mono-carboxyphenoxy-phtalocyanine (ZnMCPPc-QDs) remained aggregated in the whole analyzed pH range, even at low ionic strength, QDs capped with zinc tetracarboxyphenoxy phtalocyanine (ZnTPPc-QDs) were easily dispersed in buffers at pH equal to or higher than 7.4. QDs capped with aluminum tetrasulfonated phthalocyanine (AlTSPPc-QDs) and indium tetracarboxyphenoxy phthalocyanines (InTCPPc-QDs) were stable in aqueous suspension only at pH higher than 9.0 due to the presence of functional groups bound to the metallic center of the phthalocyanine. The ζ-potential values determined by CE for all the samples decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiological relevant solutions and thereby, its usefulness for improving their design and applications for photodynamic therapy. Graphical Abstract Schematic illustration of the phthalocyanine capped QDs nanoconjugates and the capillary electrophoresis methods applied for size and ζ-potential characterization.

Taylor dispersion analysis of metallic‐based nanoparticles – A short review

“…In this case, TDA gave lower standard deviation value than DLS, as QDs aggregates strongly impact the latter, but also because alteration of the refractive index is due to the fluorescence properties of the NPs and by the incident laser light absorption (Table 2, for Ref. [25]). In this situation, TDA with CE apparatus clearly presents the advantage of filling the inherent inconveniences originated from the DLS methodology, while working in physiologically relevant condition.…”

“…Finally, Ramírez‐García et al. worked on the characterisation of functionalised QDs, using TDA to measure the apparent equivalent sphere diameter of the metallic‐based NPs, with coupling to either UV–visible and/or fluorescence detectors [25]. Frontal mode was used with adequate equations from previously mentioned paper [23], with mathematical models being very well‐fitted to the Taylorgram.…”

“…Dynamic light scattering (DLS) hydrodynamic diameter as a function of the Taylor dispersion analysis (TDA) measurements reported from various papers; some nanoparticles (NPs) may be constituted of aggregates[10,22,23,25,2,26,27]. d H,DLS and d H,TDA refer to d H measured by DLS and TDA, respectively.…”