Our understanding of the biologic effects (including toxicity) of nanomaterials is incomplete. In vivo animal studies remain the gold standard; however, widespread testing remains impractical, and the development of in vitro assays that correlate with in vivo activity has proven challenging. Here, we demonstrate the feasibility of analyzing in vitro nanomaterial activity in a generalizable, systematic fashion. We assessed nanoparticle effects in a multidimensional manner, using multiple cell types and multiple assays that reflect different aspects of cellular physiology. Hierarchical clustering of these data identifies nanomaterials with similar patterns of biologic activity across a broad sampling of cellular contexts, as opposed to extrapolating from results of a single in vitro assay. We show that this approach yields robust and detailed structure-activity relationships. Furthermore, a subset of nanoparticles were tested in mice, and nanoparticles with similar activity profiles in vitro exert similar effects on monocyte number in vivo. These data suggest a strategy of multidimensional characterization of nanomaterials in vitro that can inform the design of novel nanomaterials and guide studies of in vivo activity.cluster analysis ͉ molecular imaging ͉ nanoparticles T he expanding use of nanomaterials has spurred interest in defining their biologic effects (1). Traditionally, the in vivo biologic and toxic effects of nanomaterials have been revealed via animal studies. For instance, single-wall carbon nanotubes cause pulmonary granulomas upon intratracheal instillation in rats and mice (2, 3). Although extremely informative, animal studies are costly and labor-intensive and thus ill-suited to systematically explore the sheer number of potential nanomaterial variables that can influence in vivo activity (including size, core material, coating, surface functionalization, and nanoscale and physicochemical properties). In vitro assays in cultured cells, although unlikely to substitute for animal studies, could help dissect structure-activity relationships and suggest nanomaterials likely to have favorable in vivo activity (4).Although numerous studies have used cultured cell models to examine nanomaterial toxicity, extrapolating from in vitro to in vivo activity remains challenging. In addition to the complexities of in vivo pharmacokinetics and bioavailability, cellular phenotypes (such as the repertoire of expressed proteins) can change significantly during in vitro cell culture (5); furthermore, nanomaterials may show significant in vitro toxicity in one cell-based assay but not others (6). Most commonly, these in vitro efforts have evaluated nanomaterials based on a single cell line and by using a limited number of phenotypes (often a single assay). This makes any conclusions critically dependent on the particular choice of cell model and assay and offers a relatively narrow view of the potentially pleiotropic ways in which a nanomaterial can modulate living systems.We sought to develop a generalizable systema...

Even as genetic studies identify alleles that influence human disease susceptibility, it remains challenging to understand their functional significance and how they contribute to disease phenotypes. Here, we describe an approach to translate discoveries from human genetics into functional and therapeutic hypotheses by relating human genetic variation to small-molecule sensitivities. We use small-molecule probes modulating a breadth of targets and processes to reveal disease allele-dependent sensitivities, using cells from multiple individuals with an extreme form of diabetes (maturity onset diabetes of the young type 1, caused by mutation in the orphan nuclear receptor HNF4α). This approach enabled the discovery of small molecules that show mechanistically revealing and therapeutically relevant interactions with HNF4α in both lymphoblasts and pancreatic β-cells, including compounds that physically interact with HNF4α. Compounds including US Food and Drug Administration–approved drugs were identified that favorably modulate a critical disease phenotype, insulin secretion from β-cells. This method may suggest therapeutic hypotheses for other nonblood disorders.