Methods to rapidly assess cell growth would be useful for many applications, including drug susceptibility testing, but current technologies have limited sensitivity or throughput. Here we present an approach to precisely and rapidly measure growth rates of many individual cells simultaneously. We flow cells in suspension through a microfluidic channel with 10–12 resonant mass sensors distributed along its length, weighing each cell repeatedly over the 4–20 min it spends in the channel. Because multiple cells traverse the channel at the same time, we obtain growth rates for >60 cells/h with a resolution of 0.2 pg/h for mammalian cells and 0.02 pg/h for bacteria. We measure the growth of single lymphocytic cells, mouse and human T cells, primary human leukemia cells, yeast, Escherichia coli and Enterococcus faecalis. Our system reveals subpopulations of cells with divergent growth kinetics and enables assessment of cellular responses to antibiotics and antimicrobial peptides within minutes.

Assays that can determine the response of tumor cells to cancer therapeutics could greatly aid the selection of drug regimens for individual patients. However, no functional assays are currently implemented clinically, and predictive genetic biomarkers are available for only a small fraction of cancer therapies. Here we demonstrate that the single-cell mass accumulation rate (MAR), profiled over many hours with a suspended microchannel resonator, accurately defines the drug sensitivity or resistance of glioblastoma multiforme (GBM) and B-cell acute lymphocytic leukemia (B-ALL) cells. MAR reveals heterogeneity in drug sensitivity not only between different tumors but also within individual tumors and tumor-derived cell lines. MAR measurement predicts drug response using samples as small as 25 μL of peripheral blood while maintaining cell viability and compatibility with downstream characterization. MAR measurement is a promising approach for directly assaying single-cell therapeutic responses and for identifying cellular subpopulations with phenotypic resistance within heterogeneous tumors.

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Multiple myeloma (MM) has benefited from significant advancements in treatment that have improved outcomes and reduced morbidity. However, the disease remains incurable and is characterized by high rates of drug resistance and relapse. Consequently, methods to select the most efficacious therapy are of great interest. Here we utilize a functional assay to assess the ex vivo drug sensitivity of single multiple myeloma cells based on measuring their mass accumulation rate (MAR). We show that MAR accurately and rapidly defines therapeutic susceptibility across human multiple myeloma cell lines to a gamut of standard-of-care therapies. Finally, we demonstrate that our MAR assay, without the need for extended culture ex vivo, correctly defines the response of nine patients to standard-of-care drugs according to their clinical diagnoses. This data highlights the MAR assay in both research and clinical applications as a promising tool for predicting therapeutic response using clinical samples.

The maintenance of invertebrate diversity within agricultural environments can enhance a number of agronomically important processes, such as nutrient cycling and biological pest control. However, few Australian studies have been undertaken which specifically address the effects of commercial management regimes on rice field biodiversity. In this study, we compared aquatic macroinvertebrate communities within Australian rice fields cultivated under three commercial management regimes: conventional-aerial (agrochemicals applied, aerially sown), conventional-drill (agrochemicals applied, directly drill-sown) and organic-drill (agrochemical-free, directly drill-sown). These comparisons were undertaken using a combination of community assessment approaches, including morphospecies richness, abundance, diversity and community composition. In general, greater biodiversity existed within macroinvertebrate communities that developed under organic management regimes than under conventional regimes (i.e., higher morphospecies richness and Shannon diversity). Although there were significant differences in several parameters across management regimes early in the rice-growing season, as the growing season progressed the invertebrate communities that developed in the different management regimes became more similar. Only community composition analyses showed significant differences late in the growing season, with functional differences across aquatic faunal assemblages suggested by increased predator abundance in communities sampled from the organic management regime. In order to improve biodiversity within these aquatic environments, management techniques need to be examined individually and the most disruptive processes identified. Alternative management procedures can then be developed that minimise biodiversity loss whilst still delivering required agronomic outcomes.

Here we use nuclear magnetic resonance to measure the solubility limit of several biologically relevant sterols in electroformed giant unilamellar vesicle membranes containing phosphatidylcholine (PC) lipids in ratios of 1:1:X DOPC:DPPC:sterol. We find solubility limits of cholesterol, lanosterol, ergosterol, stigmasterol, and β-sitosterol to be 65-70%, ~35%, 30-35%, 20-25%, and ~40%, respectively. The low solubilities of stigmasterol and β-sitosterol, which differ from cholesterol only in their alkyl tails, show that subtle differences in tail structure can strongly affect sterol solubility. Below the solubility limits, the fraction of sterol to PC-lipid in electroformed vesicles linearly reflects the fraction in the original stock solutions used in the electroformation process.

The impact of honeydew-seeking ants (Iridomyrmex rujoniger gp. spp.) on citrus canopy populations of the honeydew-producing soft scale insect, Coccus hesperidum, and the non-honeydew-producing armoured scale, Aonidiella aurantii, was evaluated during two seasons in southern New South Wales. Numbers of C . hesperidum and A . aurantii were substantially greater (3-12 times) in trees containing foraging ants than in trees from which ants were excluded. It is likely that I. rufoniger gp. spp. protects both scale species by disrupting the activity of natural enemies. Effective control of honeydew-seeking ants appears to be a prerequisite for biological control-based management of honeydewproducers in Australian citrus groves.

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