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

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.