Diffusion NMR Study of Generation-Five PAMAM Dendrimer Materials

Abstract

Commercial generation-five poly(amidoamine) dendrimer material (G5c) was fractionated into its major structural components. Monomeric G5 (G5m; 21–30 kDa) was isolated to compare its functional properties to the G5c material. Diffusion-ordered nuclear magnetic resonance spectroscopy was employed to measure the self-diffusion coefficients and corresponding hydrodynamic radii of G5m and other G5c components as a function of dendrimer size (i.e., molecular weight) and tertiary structure (i.e., generational or oligomeric nature). It was found that the hydrodynamic radius (RH) scales with approximate numbers of atoms in the trailing generations, G5m, and oligomeric material at a rate of RH ∝ N0.35, in good agreement with previous reports of RH scaling for PAMAM dendrimer with generation. G5c materials can be thought of as a heterogeneous mixture of dendrimers ranging in size from trailing generation two to tetramers of G5, approximately the same in size as a G7 dendrimer, with G5m comprising ∼65% of the material. The radius of hydration for G5m was measured to be 3.1 ± 0.1 nm at pH 7.4. The 10% swelling in response to a drop in pH observed for the G5c material was not observed for isolated G5m; however, the isolated G5–G5 dimers had an increase of 44% in RH, indicating that the G5c pH response results from the increase in RH of the oligomeric fraction upon protonation. Finally, the data allow for an experimental test of the “slip” and “stick” boundary models of the Stokes–Einstein equation for PAMAM dendrimer in water.

AB3-loaded and tumor-targeted unimolecular micelles for medullary thyroid cancer treatment

“…The pH-dependent drug release behavior could be possibly due to the fact that the hydrophobic core of the micelle, within which AB3 was encapsulated, was made of PVL, a member of the polyester family, which can be hydrolyzed faster under acidic conditions, thereby leading to a faster drug release 43–46 . Swelling of the PAMAM in an acidic condition due to the protonation of the 62 tertiary amine groups in an acidic condition could be another possible reason 47–49 .…”

Calculation of Conformational Properties and Rouse Relaxation Times of PAMAM‐EDA Dendrimers under Different pH Conditions

“…Dotted lines: Stokes–Einstein; solid line: Kirkwood–Riseman; dashed line: Kirkwood. Red squares and triangle: experimental data in neutral solutions. Green circle: experimental result for protonated dendrimer .…”

Incorporating 131I into a PAMAM (G5.0) dendrimer-conjugate: design of a theranostic nanosensor for medullary thyroid carcinoma

“…24-26 PAMAM dendrimers have gained much interest because their surface can be controlled through precisely dened chemical modications, [27][28][29] whereas their interior can be used to bind drugs, metal cations, and nanoparticles. If targeting groups with specic binding ability to tumours, such as polypeptides, carbohydrates, folic acid, etc.…”