The inherent physicochemical properties of engineered nanomaterials (ENMs) are known to control the sorption of proteins, but knowledge on how the release of ENMs to the environment prior to protein exposure affects this reaction is limited. In this study, time-resolved, in situ infrared spectroscopy was used to investigate the sorption of a model protein, bovine serum albumin (BSA), onto two different types of titanium dioxide (TiO 2 ) ENMs (catalytic-grade P90 and food-grade E171) in the presence and absence of a simple dissolved organic carbon molecule, oxalate. Infrared spectroscopy results showed that oxalate adsorbed to P90 through chemisorption interactions, but it adsorbed to E171 through physisorption interactions due to the presence of inherent surface-bound phosphates. Secondary structure and two-dimensional correlation spectroscopy analyses showed that BSA interacted with and unfolded on the surface of P90, but not E171, presumably due to the repulsive forces from the negatively charged phosphates on E171. When oxalate was pre-adsorbed to either P90 or E171, the unfolding of BSA occurred, but along different pathways. This suggests both the “outer” surface chemistry ( e.g. , oxalate layers) and the mechanism by which this layer is bound to the ENM play a significant role in the adsorption of proteins. Collectively, the results indicate the exposure of ENMs to natural and engineered environments prior to biological uptake affects the resulting protein corona formation, and thus the transport and bioactivity of ENMs.
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Following the microscopic pathway to adsorption through chemisorption and physisorption wells
Adsorption involves molecules colliding at the surface of a solid and losing their incidence energy by traversing a dynamical pathway to equilibrium. The interactions responsible for energy loss generally include both chemical bond formation (chemisorption) and nonbonding interactions (physisorption). In this work, we present experiments that revealed a quantitative energy landscape and the microscopic pathways underlying a molecule’s equilibration with a surface in a prototypical system: CO adsorption on Au(111). Although the minimum energy state was physisorbed, initial capture of the gas-phase molecule, dosed with an energetic molecular beam, was into a metastable chemisorption state. Subsequent thermal decay of the chemisorbed state led molecules to the physisorption minimum. We found, through detailed balance, that thermal adsorption into both binding states was important at all temperatures.
more » « less- Award ID(s):
- 1951328
- NSF-PAR ID:
- 10192927
- Publisher / Repository:
- American Association for the Advancement of Science (AAAS)
- Date Published:
- Journal Name:
- Science
- Volume:
- 369
- Issue:
- 6510
- ISSN:
- 0036-8075
- Page Range / eLocation ID:
- p. 1461-1465
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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