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Despite best efforts at controlling nanoparticle (NP) surface chemistries, the environment surrounding nanomaterials is always changing and can impart a permanent chemical memory. We present a set of preparation and measurement methods to be used as the foundation for studying the surface chemical memory of engineered NP aggregates. We attempt to bridge the gap between controlled lab studies and real-world NP samples, specifically TiO(2), by using well-characterized and consistently synthesized NPs, controllably producing NP aggregates with precision drop-on-demand inkjet printing for subsequent chemical measurements, monitoring the physical morphology of the NP aggregate depositions with scanning electron microscopy (SEM), acquiring "surface-to-bulk" mass spectra of the NP aggregate surfaces with time-of-flight secondary ion mass spectrometry (ToF-SIMS), and developing a data analysis scheme to interpret chemical signatures more accurately from thousands of data files. We present differences in mass spectral peak ratios for bare TiO(2) NPs compared to NPs mixed separately with natural organic matter (NOM) or pond water. The results suggest that subtle changes in the local environment can alter the surface chemistry of TiO(2) NPs, as monitored by Ti(+)/TiO(+) and Ti(+)/C(3)H(5)(+) peak ratios. The subtle changes in the absolute surface chemistry of NP aggregates vs. that of the subsurface are explored. It is envisioned that the methods developed herein can be adapted for monitoring the surface chemistries of a variety of engineered NPs obtained from diverse natural environments.

To improve liquid formulation stability, formulators employ various excipients designed to stabilize protein drugs, including buffers, salts, sugars, and surfactants. One of the roles of surfactants is to protect the protein drug from surface interactions that can destabilize the protein. Protein drug products formulated with surfactants usually contain either a polysorbate or poloxamer. Even in the presence of these surfactants, protein drug stability is often insufficient, particularly because of agitation-induced aggregation. FM1000 is one of a series of surfactants containing an alkyl chain, an amino acid, and a polyetheramine. The characterization of the dynamics of FM1000 at various water/hydrophobic interfaces was compared to Polysorbate 20, Polysorbate 80, and Poloxamer 188. FM1000 stabilizes an interface 1−2 orders of magnitude faster than all three of these surfactants, even in the presence of protein. The faster dynamics leads to improved stabilization of model protein biologic drugs IgG and abatacept against agitation-induced aggregation. These results provide mechanistic understanding of the key causes and drivers of protein aggregation.