Previous studies of uptake and effects of nanoplastics by marine organisms have been conducted at what may be unrealistically high concentrations. This is a consequence of the analytical challenges in tracking plastic particles in organisms at environmentally relevant concentrations and highlights the need for new approaches. Here, we present pulse exposures of 14C-radiolabeled nanopolystyrene to a commercially important mollusk, Pecten maximus, at what have been predicted to be environmentally relevant concentrations (<15 μg L–1). Uptake was rapid and was greater for 24 nm than for 250 nm particles. After 6 h, autoradiography showed accumulation of 250 nm nanoplastics in the intestine, while 24 nm particles were dispersed throughout the whole-body, possibly indicating some translocation across epithelial membranes. However, depuration was also relatively rapid for both sizes; 24 nm particles were no longer detectable after 14 days, although some 250 nm particles were still detectable after 48 days. Particle size thus apparently influenced the biokinetics and suggests a need for chronic exposure studies. Modeling extrapolations indicated that it could take 300 days of continued environmental exposure for uptake to reach equilibrium in scallop body tissues although the concentrations would still below 2.7 mg g–1. Comparison with previous work in which scallops were exposed to nonplastic (silver) nanomaterials of similar size (20 nm), suggests that nanoparticle composition may also influence the uptake tissue distributions somewhat.

Microcantilevers functionalized with DNA incorporating a Hind III restriction endonuclease site were digested with Hind III to produce DNA with a single-stranded end on the cantilever surface. Ligase was then used to link a second DNA molecule with a compatible end to the DNA on the cantilever. Nanomechanical motion of the cantilever was monitored throughout the digestion and ligation. Fluorescently labeled DNA was used to confirm that ligation and digestion occurred. The DNA was attached to the silicon side because Hind III and DNA ligase both require dithiothreitol to retain their activity. We therefore avoided the possibility that thiolated DNA on the gold side of the cantilever would be displaced by thiol-containing compounds in solution. Our results show that any natural DNA containing a restriction endonuclease site could be digested and attached to a cantilever functionalized with a compatible DNA. Our results also show that the ligated DNA can be removed, regenerating the cantilever for future use.

Functionalized gold nanoparticles have been covalently bound to internal, modified sites on double-stranded DNA. Gold nanoparticles coated with mercaptosuccinic acid or thioctic acid were bound to amino-modified thymine bases on double-stranded DNA. Visible absorption spectra, gel electrophoresis, and atomic force microscopy were used to analyze the products. Thiol groups were added to one end of the gold/nanoparticle product, which was then attached to a gold surface. This method has the potential to allow controlled placement of particles with subnanometer precision and to allow attachment of the product to fixed contacts for nanodevice fabrication.

The electrostatic association between mercaptosuccinic acid-coated gold clusters, about 2 nm in diameter, and amine silane derivatized silicon was examined. Relatively good coverage takes place in the pH range between 5 and 6 that coincides with the dissociation of the acid coating on the gold clusters. The latter was established by IR spectroscopy taking advantage of the typical carboxylate vibrations that differ from the protonated species. The pKa value of the gold-bound acid was estimated to be 1.3 units higher than that on the free acid. Such displacements are anticipated for monolayers of bases or acids, but it is smaller in the spherical cluster than on flat surfaces. The microstructure of the films may be manipulated through control of pH, contact time, and the nature of the crystalline substrate.

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