TY - JOUR
T1 - Structure-function relationship of PAMAM dendrimers as robust oil dispersants
AU - Geitner, Nicholas K.
AU - Wang, Bo
AU - Andorfer, Rachel E.
AU - Ladner, David A.
AU - Ke, Pu Chun
AU - Ding, Feng
PY - 2014/11/4
Y1 - 2014/11/4
N2 - PAMAM dendrimers have recently been investigated as efficient and biocompatible oil dispersants utilizing their encapsulation capacity; however, their high cationic charge density has been shown to be cytotoxic. It is therefore imperative to mitigate cationic charge-induced toxicity and understand the effects of such changes. Presented here is a synergistic experimental and computational approach to examine the effects of varying terminal surface charge on the capacity of dendrimers to disperse model liner, polycyclic aromatic, and hybrid hydrocarbons. Uncharged dendrimers collapse by forming intramolecular hydrogen bonds, which reduce the hosting capability. On the other hand, changing the surface charges from positive to negative greatly shifts the pKa of tertiary amines of the PAMAM dendrimer interior. As a result, the negatively charged dendrimers have a significant percentage of tertiary amines protonated, ∼30%. This unexpected change in the interior protonation state causes electrostatic interactions with the anionic terminal groups, leading to contraction and a marked decrease in hydrocarbon hosting capacity. The present work highlights the robust nature of dendrimer oil dispersion and also illuminates potentially unintended or unanticipated effects of varying dendrimer surface chemistry on their encapsulation or hosting efficacy, which is important for their environmental, industrial, and biomedical applications.
AB - PAMAM dendrimers have recently been investigated as efficient and biocompatible oil dispersants utilizing their encapsulation capacity; however, their high cationic charge density has been shown to be cytotoxic. It is therefore imperative to mitigate cationic charge-induced toxicity and understand the effects of such changes. Presented here is a synergistic experimental and computational approach to examine the effects of varying terminal surface charge on the capacity of dendrimers to disperse model liner, polycyclic aromatic, and hybrid hydrocarbons. Uncharged dendrimers collapse by forming intramolecular hydrogen bonds, which reduce the hosting capability. On the other hand, changing the surface charges from positive to negative greatly shifts the pKa of tertiary amines of the PAMAM dendrimer interior. As a result, the negatively charged dendrimers have a significant percentage of tertiary amines protonated, ∼30%. This unexpected change in the interior protonation state causes electrostatic interactions with the anionic terminal groups, leading to contraction and a marked decrease in hydrocarbon hosting capacity. The present work highlights the robust nature of dendrimer oil dispersion and also illuminates potentially unintended or unanticipated effects of varying dendrimer surface chemistry on their encapsulation or hosting efficacy, which is important for their environmental, industrial, and biomedical applications.
UR - http://www.scopus.com/inward/record.url?scp=84908582605&partnerID=8YFLogxK
U2 - 10.1021/es5038194
DO - 10.1021/es5038194
M3 - Article
C2 - 25279688
AN - SCOPUS:84908582605
SN - 0013-936X
VL - 48
SP - 12868
EP - 12875
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 21
ER -