Study on elution behavior of poly(amidoamine) dendrimers and their interaction with bovine serum albumin in asymmetrical flow field-flow fractionation

Abstract

Polyamidoamine (PAMAM) dendrimers have an amine surface and an ethylenediamine core and are of great interest in various applications such as in drug delivery. Physiochemical properties of PAMAM dendrimers vary with pH. At neutral to basic pH, PAMAM dendrimers are either weakly charged or uncharged and tend to adsorb on to the neutral packing material, making chromatographic separation of the dendrimers difficult. Asymmetrical flow field-flow fractionation (AsFlFFF) was tested as an alternative to the chromatographic techniques for separation of the PAMAM dendrimers. AsFlFFF provided generation-based separation of the dendrimers even at neutral and basic pH. The elution time increased gradually as the generation number (and thus the size) increased. Separation of impurities such as generational or missing-arm impurities and aggregates from the main population was also achieved. Electrostatic and hydrophobic interactions (e.g., repulsive elecrostatic interaction among the dendrimer molecules or attractive hydrophobic interaction between the dendrimer molecules and the membrane) may result in an inaccurate size measurement. Careful optimization of experimental conditions such as the flow rate, pH, and the salt concentration may be required to minimize the interactions with the membrane. AsFlFFF was also tested for a study on the interaction between the PAMAM dendrimers and proteins. AsFlFFF was able to show the growth in the size of bovine serum albumin (BSA) when BSA is mixed with increasing amounts of PAMAM dendrimers. Results suggest that, with proper optimization, AsFlFFF could become a useful tool for separation and characterization of large charged molecules such as PAMAM dendrimers.

Quantitative analysis of generation and branch defects in G5 poly(amidoamine) dendrimer

“…It has been speculated in the literature that the width of dendrimer peaks from flow-based separations is due to molecular weight distributions caused by structural defects [17,23], however to date no molecular weight measurements have been coupled to these techniques. Single, 3 s fractions were isolated from across the monomer and dimer HPLC peaks (Fig.…”

“…They observed differences in electrophoretic mobilities leading to fast migrating trailing generations, and slowly migrating impurities that were attributed to lower charges due to missing or looped arms, and high weight oligomers; however, this technique cannot explicitly distinguish between these structures, and no further complementary characterization was performed. Lee et al used field flow fractionation to do size dependent separation of G4–G9 at various pH conditions [17]. They observed the presence of high (dimers) and low (trailing and skeletal defects) molecular weights via changes in sample mobility, in all generations and conditions, but did not employ further techniques to study the materials.…”

Application of flow field-flow fractionation for the characterization of macromolecules of biological interest: a review

“…AsFlFFF provides a generation-based separation of these highly charged PAMAM dendrimers under acidic, neutral, or even basic conditions (see Fig. 7), as reported by Lee et al [75]. AsFlFFF size analysis under neutral conditions made it possible to study the interaction between bovine serum albumin and PAMAM dendrimers.…”

Local hydrodynamics of solvent near diffusing dendrimers: A test of the new Stokes–Einstein relation

“…It has been reported that the size of dendrimers is influenced by different pH values . We ignore this in the simple model of dendrimers without atom details, and so did the cited experimental size data of dendrimers which closely match the simulation data.…”