Separation, characterization and identification of microplastics and nanoplastics in the environment.

Gold nanoparticles (AuNPs) have found broad applications in chemical and biological sensing, catalysis, biomolecular imaging, in vitro diagnostics, cancer therapy, and many other areas. Dynamic light scattering (DLS) is an analytical tool used routinely for nanoparticle size measurement and analysis. Due to its relatively low cost and ease of operation in comparison to other more sophisticated techniques, DLS is the primary choice of instrumentation for analyzing the size and size distribution of nanoparticle suspensions. However, many DLS users are unfamiliar with the principles behind the DLS measurement and are unware of some of the intrinsic limitations as well as the unique capabilities of this technique. The lack of sufficient understanding of DLS often leads to inappropriate experimental design and misinterpretation of the data. In this study, we performed DLS analyses on a series of citrate-stabilized AuNPs with diameters ranging from 10 to 100 nm. Our study shows that the measured hydrodynamic di...

Techniques for Accurate Sizing of Gold Nanoparticles Using Dynamic Light Scattering with Particular Application to Chemical and Biological Sensing Based on Aggregate Formation.

In recent years, scientists have created artificial microscopic and nanoscopic self-propelling particles, often referred to as nano- or microswimmers, capable of mimicking biological locomotion and taxis. This active diffusion enables the engineering of complex operations that so far have not been possible at the micro- and nanoscale. One of the most promising tasks is the ability to engineer nanocarriers that can autonomously navigate within tissues and organs, accessing nearly every site of the human body guided by endogenous chemical gradients. We report a fully synthetic, organic, nanoscopic system that exhibits attractive chemotaxis driven by enzymatic conversion of glucose. We achieve this by encapsulating glucose oxidase alone or in combination with catalase into nanoscopic and biocompatible asymmetric polymer vesicles (known as polymersomes). We show that these vesicles self-propel in response to an external gradient of glucose by inducing a slip velocity on their surface, which makes them move in an extremely sensitive way toward higher-concentration regions. We finally demonstrate that the chemotactic behavior of these nanoswimmers, in combination with LRP-1 (low-density lipoprotein receptor-related protein 1) targeting, enables a fourfold increase in penetration to the brain compared to nonchemotactic systems.

Chemotactic synthetic vesicles: Design and applications in blood-brain barrier crossing

Expanded use of engineered nanoparticles (ENPs) in consumer products increases the potential for environmental release and unintended biological exposures. As a result, measurement techniques are needed to accurately quantify ENP size, mass, and particle number distributions in biological matrices. This work combines single particle inductively coupled plasma mass spectrometry (spICPMS) with tissue extraction to quantify and characterize metallic ENPs in environmentally relevant biological tissues for the first time. ENPs were extracted from tissues via alkaline digestion using tetramethylammonium hydroxide (TMAH). Method development was performed using ground beef and was verified in Daphnia magna and Lumbriculus variegatus . ENPs investigated include 100 and 60 nm Au and Ag stabilized by polyvynylpyrrolidone (PVP). Mass- and number-based recovery of spiked Au and Ag ENPs was high (83-121%) from all tissues tested. Additional experiments suggested ENP mixtures (60 and 100 nm Ag ENPs) could be extracted and quantitatively analyzed. Biological exposures were also conducted to verify the applicability of the method for aquatic organisms. Size distributions and particle number concentrations were determined for ENPs extracted from D. magna exposed to 98 μg/L 100 nm Au and 4.8 μg/L 100 nm Ag ENPs. The D. magna nanoparticulate body burden for Au ENP uptake was 613 ± 230 μg/kgww, while the measured nanoparticulate body burden for D. magna exposed to Ag ENPs was 59 ± 52 μg/kgww. Notably, the particle size distributions determined from D. magna tissues suggested minimal shifts in the size distributions of ENPs accumulated, as compared to the exposure media.

Extraction and analysis of silver and gold nanoparticles from biological tissues using single particle inductively coupled plasma mass spectrometry.

Antibody-Gold Nanoparticle Bioconjugates for Biosensors: Synthesis, Characterization and Selected Applications.

Protein-conjugated gold nanoparticles (AuNPs) have been extensively explored for the development of many novel protein assays. In this article, we demonstrate that nanoparticle tracking analysis (NTA) can be used as a rapid and simple analytical tool to monitor bioconjugation and to study protein-protein interactions. The adsorption of protein A onto gold nanoparticles was analyzed using NTA. The conjugation resulted in a measurable increase in hydrodynamic radius that correlated with protein A concentration, allowing conditions for complete conjugation to be elucidated. NTA was then used to investigate the binding of mouse IgG to protein A-conjugated AuNPs and the K(a) was measured as 2.00 × 10(7) M(-1). Furthermore, an assay for the detection of mouse IgG was developed using NTA to detect the binding to antibody-AuNP conjugates. This assay provided a detection limit of 3.2 ng mL(-1); however, the formation of aggregates resulting from the use of a polyclonal antibody and multiple binding sites on the antigen prevented the determination of binding affinity for this antibody-antigen system. To measure the binding affinity for this antibody-antigen system the IgG antigen was conjugated to the AuNPs and NTA was used to monitor the binding of the antibody. In this configuration aggregation of conjugates was not detected and a binding affinity constant of 2.80 × 10(8) M(-1) was measured. NTA results obtained in this work were validated by comparison to DLS. This work represents the first evaluation of NTA as an analytical tool for characterizing AuNP bioconjugates, investigating protein-protein binding, and detecting low levels of antigen in a bioassay.

Monitoring gold nanoparticle conjugation and analysis of biomolecular binding with nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS)

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Monitoring gold nanoparticle conjugation and analysis of biomolecular binding with nanoparticle tracking analysis (NTA) and dynamic light scattering (DLS)