Aggregation, Dissolution, and Stability of Quantum Dots in Marine Environments: Importance of Extracellular Polymeric Substances

Abstract

There is an increasing concern that a considerable fraction of engineered nanoparticles (ENs), including quantum dots (QDs), will eventually find their way into the marine environment and have negative impacts on plankton. As ENs enter the ocean, they will encounter extracellular polymeric substances (EPS) from microbial sources before directly interacting with plankton cells. In this study, EPS harvested from four phytoplankton species, Amphora sp., Dunaliella tertiolecta, Phaeocystis globosa, and Thalassiosira pseudonana, were examined for potential interactions with CdSe nonfunctionalized and functionalized (carboxyl- and amine-) QDs in artificial seawater. Our results show that EPS do not reduce the solubility of QDs but rather decrease their stability. The degradation rate of QDs was positively correlated to the protein composition of EPS (defined by the ratio of protein/carbohydrate). Two approaches showed significant inhibition to the degradation of carboxyl-functionalized QDs: (1) the presence of an antioxidant, such as N-acetyl cysteine, and (2) absence of light. Owing to the complexity in evaluating integrated effects of QDs intrinsic properties and the external environmental factors that control the stability of QDs, conclusions must be based on a careful consideration of all these factors when attempting to evaluate the bioavailability of QDs and other ENs in the marine environments.

Aggregation, Dissolution, and Transformation of Copper Nanoparticles in Natural Waters

“…3 Additionally, several copper nanomaterials including Cu 2 O and CuO have been shown to possess photocatalytic properties, 4−6 which may pose greater hazard to organisms if suspended in photic surface waters than if sedimented into aphotic sediments. Size, 7 coating, 8 solubility, 9 and photoactivity 10,11 have all been implicated as playing roles in ENM toxicity and are all affected by water chemistry. Aggregate size (and consequently, sedimentation rate) is influenced by ionic strength (IS) and pH via charge regulation, 12,13 whereby the effective repulsive surface charge of the ENMs is decreased through ionic shielding and surface de/protonation.…”

Heteroaggregation of nanoparticles with biocolloids and geocolloids

“…The importance of NOM on the aggregation behavior of nanoparticles has led to many studies. However, due to the complex composition of NOM, most of the studies consider a specific composition of NOM, such as fulvic acid [43] or humic acid, and more recently, microbial EPS [58,[87][88][89]. In addition, although a number of studies have provided a clear understanding of the role of NOM in a homoaggregation system [14,80,90], there are very few studies that address the role of NOM in heteroaggregation [91].…”

Effects and Implications of Trophic Transfer and Accumulation of CeO2 Nanoparticles in a Marine Mussel

“…24 EPS protein and carbohydrate content was measured using the modified Lowry Protein Assay Kit (Pierce, 23240, U.S.) and the anthrone method, 25 respectively. 2.4.…”