Understanding dendritic polymer–hydrocarbon interactions for oil dispersion

Geitner, Nicholas K.; Bhattacharya, Priyanka; Steele, Muriel; Chen, Ran; Ladner, David A.; Ke, Pu Chun

doi:10.1039/c2ra21602g

Cited by 16 publications

(30 citation statements)

References 30 publications

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“…Given their hosting capabilities, we have previously proposed PAMAM polymers as oil dispersants 11 and showed that cationic PAMAM dendrimers are capable of hosting both polyaromatic and linear hydrocarbons in water. 11 Conventionally, lipid-like oil dispersants have been in use since at least the 1960s 12 and also during the large scale Deepwater Horizon disaster of 2010.…”

Section: Introductionmentioning

confidence: 99%

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Structure–Function Relationship of PAMAM Dendrimers as Robust Oil Dispersants

Geitner

Wang

Andorfer

et al. 2014

Environ. Sci. Technol.

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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 pK a 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.

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Section: Introductionmentioning

confidence: 99%

“…11 Conventionally, lipid-like oil dispersants have been in use since at least the 1960s 12 and also during the large scale Deepwater Horizon disaster of 2010. However, concerns over the potential toxicity of conventional oil dispersants have been recently raised.…”

Section: Introductionmentioning

confidence: 99%

Structure–Function Relationship of PAMAM Dendrimers as Robust Oil Dispersants

Geitner

Wang

Andorfer

et al. 2014

Environ. Sci. Technol.

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“…Our previous experimental study indicated that G4 PAMAM dendrimers dispersed linear and aromatic hydrocarbons quite differently, as evidenced in measurements of hydrodynamic size, 20 loading capacity, and stability 18 of the resulting complexes formed between the dendrimer and the hydrocarbons. Based on simulations of single dendrimers interacting with single and multiple hydrocarbons, we revealed a cooperativity in both C16 and PN dispersion by dendrimers.…”

Section: Resultsmentioning

confidence: 99%

“…We have previously proposed and verified in lab--scale studies that cationic PAMAM dendrimers can act as efficient oil dispersants 20 for both polyaromatic and linear hydrocarbons, two key components of crude oil. In our previous experiment, linear hexadecane (C16) and polyaromatic phenanthrene (PN) were used as model hydrocarbons, both of which were hydrophobic while their size difference was negligible relative to that of a G4--PAMAM dendrimer.…”

Section: Introductionmentioning

confidence: 98%

“…3 In addition to drug delivery, the hosting capability of dendrimers can also be utilized in environmental applications such as water purification, desalination, and pollution remediation. [20][21][22] Commercially available oil dispersants including Corexit have been in use for treating oil spills worldwide. 23,24 However, the potential toxicity of oil dispersants has recently become a great concern, particularly after their large--scale deployment in the 2010 Deepwater Horizon Spill.…”

Section: Introductionmentioning

confidence: 99%

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Deviation from the Unimolecular Micelle Paradigm of PAMAM Dendrimers Induced by Strong Interligand Interactions

et al. 2015

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PAMAM (polyamidoamine) dendrimers have been recently exploited as efficient and biocompatible unimolecular micelles for oil spill remediation utilizing their robust encapsulation capability. However, experimental evidence suggested contrasting dispersion mechanisms of PAMAM exist toward different types of hydrocarbon ligands, including linear and polyaromatic oil molecules. Specifically, the dispersion of linear hydrocarbons by PAMAM was found to violate the unimolecular micelle convention by forming molecular complexes orders of magnitude larger than a single PAMAM. It is therefore essential to re--examine the dispersion mechanisms of PAMAM toward different types of ligands in order to facilitate dendrimer applications in environmental remediation, catalysis and nanomedicine. Here we applied atomistic discrete molecular dynamics simulations to study generation--four (G4) PAMAM dendrimers dispersing hexadecane (C16) and phenanthrene (PN), two representative linear and polyaromatic hydrocarbons in crude oil. We observed a strong cooperativity in the binding of both C16 and PN to PAMAM dendrimers, especially with C16. Simulations of multiple PAMAM molecules interacting with many hydrocarbons illustrated that phenanthrene bound to individual dendrimers to render a unimolecular micelle, while multiple C16 molecules formed a large droplet enclosed and stabilized by multiple PAMAM dendrimers to assemble into a multi--molecular micelle. Our analysis revealed that such deviation of the PAMAM--ligand architecture from the conventional unimolecular micelle paradigm arose from strong inter--ligand interactions between linear hydrocarbons. Keywords

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Impact of dispersant on early life stages of the water flea Daphnia magna and the eastern oyster Crassostrea virginica

Salehi¹,

Rodríguez

Boettcher

et al. 2017

J of Applied Toxicology

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In response to the 2010 Deepwater Horizon oil spill, over 1 million gallons of dispersant were applied in Gulf of Mexico offshore waters; Corexit 9500 was the most applied dispersant. The impact on organisms in nearshore and freshwaters has received little scrutiny. Acute 48 h toxicity of Corexit 9500 and a new hyperbranched polyethylenimine (HPEI) dispersant-like compound were evaluated for the freshwater indicator organism, Daphnia magna and for larval and early spat stages of the Eastern oyster, Crassostrea virginica. For D. magna, Corexit 9500 demonstrated toxicity (EC of 0.14 [0.13, 0.15] ppm) similar to the 10-kDa HPEI (EC of 0.16 [0.12, 0.19] ppm). HPEI toxicity increased as a function of molecular weight (1.2 to 750 kDa). The 10 kDa size HPEI was further investigated because it dispersed crude oil with equal effectiveness as Corexit. For Corexit, 100% oyster mortality was detected for the ≤0.2-mm size classes and mortality >50% for the 0.3- and 0.7-mm size classes at the two greatest concentrations (25 and 50 ppm). HPEI (10 kDa) exhibited low mortality rates (<30%) for all concentrations for all oyster size classes except the 0.1-mm class. Although mortality rates for this size class were up to 60%, mortality was still less than the mortality caused by Corexit 9500. The low toxicity of HPEI polymers for C. virginica in comparison with Corexit 9500 suggests that HPEI polymers warrant further study.

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Understanding dendritic polymer–hydrocarbon interactions for oil dispersion

Cited by 16 publications

References 30 publications

Structure–Function Relationship of PAMAM Dendrimers as Robust Oil Dispersants

Structure–Function Relationship of PAMAM Dendrimers as Robust Oil Dispersants

Deviation from the Unimolecular Micelle Paradigm of PAMAM Dendrimers Induced by Strong Interligand Interactions

Impact of dispersant on early life stages of the water flea Daphnia magna and the eastern oyster Crassostrea virginica

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