Capillary electrophoresis of polycationic poly(amidoamine) dendrimers

Abstract

Generation 2 to generation 5 poly(amidoamine) (PAMAM) dendrimers having different terminal functionalities were analyzed by capillary electrophoresis (CE). Polyacrylamide gel electrophoresis was also used to assess the composition of the individual generations for comparison with the CE results. Separation of PAMAMs can be accomplished by either using uncoated silica or silanized silica capillaries, although reproducibility is poor using the uncoated silica capillary. To improve run-to-run reproducibility, silanized capillary was used and various internal standards were also tested. Relative and normalized migration times of primary amine terminated PAMAM dendrimers were then determined using 2,3-diaminopyridine (2,3-DAP) as an internal standard. Using silanized capillaries and internal standards, the relative and normalized migration times are fully reproducible and comparable between runs. Apparent dimensionless electrophoretic mobilities were determined and the results were compared to theoretical calculations. It is concluded that for PAMAMs a complex separation mechanism has to be considered in CE, where the movement of the ions is due to the electric field, but the separation is rather the consequence of the adsorption/desorption equilibria on the capillary wall ("electrokinetic capillary chromatography"). The described method may be used for quality control and may serve as an effective technique to analyze polycationic PAMAM dendrimers and their derivatives with different surface modifications.

Electrophoretic mobility and molecular distribution studies of poly(amidoamine) dendrimers of defined charges

“…Rinsing and flushing were performed at room temperature under syringe-induced vacuum. We have previously compared the CE performance using both bare fused-silica capillary and silanized capillary [19]. We show that for polycationic PAMAM dendrimers, the separation reproducibility is significantly improved using silanized capillary because dendrimer adsorption onto the capillary are significantly decreased.…”

“…Polycationic E5 PAMAMs were dissolved in pH 2.5 phosphate buffer and the sample solutions were adjusted to pH 2.5 using 0.1 M phosphoric acid to give a concentration of 1 mg/mL. All polycationic dendrimer samples contained 0.05 mg/mL 2,3-diaminopyridine (2,3-DAP) as an internal standard to normalize the migration times of polycationic E5 PAMAMs (E5.NH 2 , E5.25Ac, E5.50Ac, E5.75Ac, and E5.100Ac) [19]. The normalization is necessary because the absolute migration times of polycationic PAMAMs often change due to their dynamic adsorption/desorption onto capillary surface during separation, while the migration time ratio between PAMAMs and internal standands are always constant in different runs.…”

“…For the characterization of polycationic E5 dendrimers, silanized capillaries [19] (id 100 mm) with total length of 78.5 cm and effective length of 70 cm were employed. For the silanization of capillary, briefly, the bare fused-silica capillary was pretreated by rinsing with a 1.0 M NaOH solution for 30 min to activate the hydroxyl groups on the silica surface, followed by an aqueous wash with water for 30 min, then with methanol for 30 min, and subsequently with THF for 20 min.…”

Capillary Electrophoresis in Nanotechnologies versus Nanotechnologies in Capillary Electrophoresis

“…Microfluidic format used in nanoparticle separation was reviewed by Salafi et al [42]. More focused review article about CE analysis of poly(amidoamine) dendrimeric structures was prepared by Shi et al [43]. Paper summarizing the application of separation techniques (including CE) of gold nanoparticles [44,45] and QDs [46,47] analysis are also accessible.…”

Tumour and dendrimers: a review on drug delivery aspects

“…(Erichmann et al 2000;Jain & Khopade 2001;Shi et al 2005). Dendrimers could prove to be efficient archers in the battle against cancer.…”