Dermal interstitial fluid (ISF) is an underutilized information-rich biofluid potentially useful in health status monitoring applications whose contents remain challenging to characterize. Here, we present a facile microneedle approach for dermal ISF extraction with minimal pain and no blistering for human subjects and rats. Extracted ISF volumes were sufficient for determining transcriptome, and proteome signatures. We noted similar profiles in ISF, serum, and plasma samples, suggesting that ISF can be a proxy for direct blood sampling. Dynamic changes in RNA-seq were recorded in ISF from induced hypoxia conditions. Finally, we report the first isolation and characterization, to our knowledge, of exosomes from dermal ISF. The ISF exosome concentration is 12–13 times more enriched when compared to plasma and serum and represents a previously unexplored biofluid for exosome isolation. This minimally invasive extraction approach can enable mechanistic studies of ISF and demonstrates the potential of ISF for real-time health monitoring applications.

As wearable fitness devices have gained commercial acceptance, interest in real-time monitoring of an individual's physiological status using noninvasive techniques has grown. Microneedles have been proposed as a minimally invasive technique for sampling the dermal interstitial fluid (ISF) for clinical monitoring and diagnosis, but little is known about its composition. In this study, a novel microneedle array was used to collect dermal ISF from three healthy human donors and compared with matching serum and plasma samples. Using a shotgun quantitative proteomic approach, 407 proteins were quantified with at least one unique peptide, and of those, 135 proteins were differently expressed at least 2-fold. Collectively, these proteins tended to originate from the cytoplasm, membrane bound vesicles, and extracellular vesicular exosomes. Proteomic analysis confirmed previously published work that indicates that ISF is highly similar to both plasma and serum. In this study, less than one percent of proteins were uniquely identified in ISF. Taken together, ISF could serve as a minimally invasive alternative for blood-derived fluids with potential for real-time monitoring applications.

An entirely solid-phase synthesis of daptomycin, a cyclic lipodepsipeptide antibiotic currently in clinical use, was achieved using a combination of α-azido and Fmoc amino acids. This methodology was applied to the synthesis of several daptomycin analogs, one of which did not contain kynurenine or the synthetically challenging amino acid (2S,3R)-methylglutamate yet exhibited an MIC approaching that of daptomycin.

To better understand how changes in cells in nasal secretions reflect changes in the nasal mucosa occurring during allergic reactions, we obtained nasal lavage and biopsy specimens from normal (n = 11) asymptomatic, seasonally allergic (n = 18), and perennially allergic (n = 18) subjects. Initial baseline lavages showed that perennially, and seasonally allergic subjects, out of their allergy seasons, had significantly higher numbers of eosinophils (p < 0.01) and neutrophils (p < 0.01) and total cell counts (p < 0.05) than normal subjects. Biopsy results showed that at baseline, seasonally allergic subjects had thicker mucosa (p < 0.01), greater numbers of intraepithelial mononuclear cells and total cells (p < 0.01), and greater numbers of subepithelial neutrophils (p < 0.001) than perennially allergic subjects. Twenty-four hours after antigen provocation, nasal lavage of allergic subjects showed an increase in the number of eosinophils (p < 0.05). Seasonally allergic subjects also had significant increases in numbers of intraepithelial mononuclear cells (p < 0.05) and total cells (p < 0.01), and in subepithelial eosinophils (p < 0.001) and mononuclear cells (p < 0.05), which were localized to the side challenged. Despite an influx in eosinophils, the epithelial layer was not changed from baseline. The data provide evidence that nasal secretions and the nasal mucosa represent two distinct cellular compartments.

Daptomycin and A54145 are homologous lipopeptide antibiotics that permeabilize the cell membranes of Gram-positive bacteria. Membrane permeabilization depends on the presence of both phosphatidylglycerol (PG) and calcium, and it involves the formation of oligomeric transmembrane pores that consist of approximately 6-8 subunits. We here show that each lipopeptide molecule binds two calcium ions in separable, successive steps. The first calcium ion causes the lipopeptide molecule to bind to the target membrane, and likely to form a loosely associated oligomer. Higher calcium concentrations induce binding of a second ion, which produces the more tightly associated and more deeply membrane-inserted final, functional form of the oligomer. Both calcium-dependent steps are accompanied by fluorescence signals that indicate transition of specific amino acid residues into less polar environments, suggestive of insertion into the target membrane. Our findings agree with the earlier observation that two of the four acidic amino acid residues in the daptomycin molecule are essential for antibacterial activity.