title: Quantification of Free Polyelectrolytes Present in Colloidal Suspension, Revealing a Source of Toxic Responses for Polyelectrolyte-Wrapped Gold Nanoparticles.
abstract: Polyelectrolyte (PE) wrapping of colloidal nanoparticles (NPs) is a standard method to control NP surface chemistry and charge. Because excess polyelectrolytes are usually employed in the surface modification process, it is critical to evaluate different purification strategies to obtain a clean final product and thus avoid ambiguities in the source of effects on biological systems. In this work, 4 nm diameter gold nanoparticles (AuNPs) were wrapped with 15 kDa poly(allylamine hydrochloride) (PAH), and three purification strategies were applied: (a) diafiltration or either (b) one round or (c) two rounds of centrifugation. The bacterial toxicity of each of these three PAH-AuNP samples was evaluated for the bacterium Shewanella oneidensis MR-1 and is quantitatively correlated with the amount of unbound PAH molecules in the AuNP suspensions, as judged by X-ray photoelectron spectroscopy, nuclear magnetic resonance experiments and quantification using fluorescent assay. Dialysis experiments show that, for a 15 kDa polyelectrolyte, a 50 kDa dialysis membrane is not sufficient to remove all PAH polymers. Together, these data showcase the importance of choosing a proper postsynthesis purification method for polyelectrolyte-wrapped NPs and reveal that apparent toxicity results may be due to unintended free wrapping agents such as polyelectrolytes.
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Tian A
authors.initials: TA
authors.lastname: Qiu
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Marco D
authors.initials: MD
authors.lastname: Torelli
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Ariane M
authors.initials: AM
authors.lastname: Vartanian
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Nathan B
authors.initials: NB
authors.lastname: Rackstraw
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Joseph T
authors.identifier: 0000-0001-5827-8513
authors.initials: JT
authors.lastname: Buchman
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Jacob
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Catherine J
authors.identifier: 0000-0001-7066-5575
authors.initials: CJ
authors.lastname: Murphy
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison , 1101 University Avenue, Madison, Wisconsin 53706, United States.
authors.forename: Robert J
authors.identifier: 0000-0003-3821-9625
authors.initials: RJ
authors.lastname: Hamers
authors.affiliation: Department of Chemistry, University of Minnesota , 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States.
authors.forename: Christy L
authors.identifier: 0000-0002-5420-5867
authors.initials: CL
authors.lastname: Haynes
mesh_terms: D002498:Centrifugation; D003102:Colloids / Q000737:chemistry*; D005374:Filtration / Q000379:methods; D005453:Fluorescence; D006046:Gold / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D056951:Photoelectron Spectroscopy; D011073:Polyamines / Q000032:analysis / Q000737:chemistry*; D000071228:Polyelectrolytes / Q000032:analysis* / Q000302:isolation & purification; D020592:Shewanella / Q000187:drug effects*; D018675:Toxicity Tests / Q000379:methods
chemical_list: D003102:Colloids; D008567:Membranes, Artificial; D011073:Polyamines; D000071228:Polyelectrolytes; C063994:polyallylamine; D006046:Gold