Characterization of freestanding photoresist films for biological and MEMS applications

Photoresists are light-sensitive resins used in a variety of technological applications. In most applications, however, photoresists are generally used as sacrificial layers or a structural layer that remains on the fabrication substrate. Thin layers of patterned 1002F photoresist were fabricated and released to form a freestanding film. Films of thickness in the range of 4.5–250 μm were patterned with through-holes to a resolution of 5 μm and an aspect ratio of up to 6:1. Photoresist films could be reliably released from the substrate after a 12-hour immersion in water. The Young’s modulus of a 50 μm-thick film was 1.43 ± 0.20 GPa. Use of the films as stencils for patterning sputtered metal onto a surface was demonstrated. These 1002F stencils were used multiple times without deterioration in feature quality. Furthermore, the films provided biocompatible, transparent surfaces of low autofluorescence on which cells could be grown. Culture of cells on a film with an isolated small pore enabled a single cell to be accessed through the underlying channel and loaded with exogenous molecules independently of nearby cells. Thus 1002F photoresist was patterned into thin, flexible, free-standing films that will have numerous applications in the biological and MEMS fields

A comparative evaluation of socratic versus didactic tutoring

While the effectiveness of one-on-one human tutoring has been well established, a great deal of controversy surrounds the issue of which features of tutorial dialogue separate effective uses of dialogue in tutoring from those that are less effective. In this paper we present a formal comparison of Socratic versus Didactic style tutoring that argues in favor of the Socratic tutoring style

Selective single cell isolation for genomics using microraft arrays

Genomic methods are used increasingly to interrogate the individual cells that compose specific tissues. However, current methods for single cell isolation struggle to phenotypically differentiate specific cells in a heterogeneous population and rely primarily on the use of fluorescent markers. Many cellular phenotypes of interest are too complex to be measured by this approach, making it difficult to connect genotype and phenotype at the level of individual cells. Here we demonstrate that microraft arrays, which are arrays containing thousands of individual cell culture sites, can be used to select single cells based on a variety of phenotypes, such as cell surface markers, cell proliferation and drug response. We then show that a common genomic procedure, RNA-seq, can be readily adapted to the single cells isolated from these rafts. We show that data generated using microrafts and our modified RNA-seq protocol compared favorably with the Fluidigm C1. We then used microraft arrays to select pancreatic cancer cells that proliferate in spite of cytotoxic drug treatment. Our single cell RNA-seq data identified several expected and novel gene expression changes associated with early drug resistance

Transferable neuronal mini-cultures to accelerate screening in primary and induced pluripotent stem cell-derived neurons

The effort and cost of obtaining neurons for large-scale screens has limited drug discovery in neuroscience. To overcome these obstacles, we fabricated arrays of releasable polystyrene micro-rafts to generate thousands of uniform, mobile neuron mini-cultures. These mini-cultures sustain synaptically-active neurons which can be easily transferred, thus increasing screening throughput by >30-fold. Compared to conventional methods, micro-raft cultures exhibited significantly improved neuronal viability and sample-to-sample consistency. We validated the screening utility of these mini-cultures for both mouse neurons and human induced pluripotent stem cell-derived neurons by successfully detecting disease-related defects in synaptic transmission and identifying candidate small molecule therapeutics. This affordable high-throughput approach has the potential to transform drug discovery in neuroscience

Acetate as a model for aspartate-based CXCR4 chemokine receptor binding of cobalt and nickel complexes of cross-bridged tetraazamacrocycles

A number of disease states including WHIM syndrome, HIV infection and cancer have been linked to the chemokine receptor CXCR4. High-affinity CXCR4 antagonist transition metal complexes of configurationally restricted bis-tetraazamacrocyclic ligands have been identified in previous studies. Recently synthesised and structurally characterised Co2+/Co3+ and Ni2+ acetate complexes of mono-macrocycle cross-bridged ligands have been used to mimic their known coordination interaction with the aspartate side chains on binding to CXCR4. Here, X-ray crystal structures for three Co2+/Co3+ acetate complexes and five Ni2+ acetate complexes are presented and demonstrate flexibility in the mode of binding to the acetate ligand concomitantly with the requisite cis-V-configured cross-bridged tetraazamacrocyle. Complexes of the smaller Co3+ metal ion exclusively bind acetate by chelating both oxygens of acetate. Larger Co2+ and Ni2+ metal ions in cross-bridged tetraazamacrocycles show a clear tendency to coordinate acetate in a monodentate fashion with a coordinated water molecule completing the octahedral coordination sphere. However, in unbridged tetraazamacrocycle acetate structures reported in the literature, the coordination preference is to chelate both acetate oxygens. We conclude that the short ethylene cross-bridge restricts the equatorial bulk of the macrocycle, prompting the metal ion to fill the equator with the larger monodentate acetate plus water ligand set. In unbridged ligand examples, the flexible macrocycle expands equatorially and generally only allows chelation of the sterically smaller acetate alone. These results provide insight for generation of optimised bis-macrocyclic CXCR4 antagonists utilising cobalt and nickel ions

Cellular shape reinforces niche to stem cell signaling in the small intestine

Peer reviewe

Assessing the automaticity of moral processing: Efficient coding of moral information during narrative comprehension

A long-standing theoretical debate concerns the involvement of principled reasoning versus relatively automatic intuitive-emotional processing in moral cognition. To address this, we investigated whether the mental models formed during story comprehension contain a moral dimension and whether this process is affected by cognitive load. A total of 72 participants read stories about fictional characters in a range of moral situations, such as a husband being tempted to commit adultery. Each story concluded with a “moral” or “immoral” target sentence. Consistent with a framework of efficient extraction of moral information, participants took significantly longer to read immoral than moral target sentences. Moreover, the magnitude of this effect was not compromised by cognitive load. Our findings provide evidence of efficient coding of moral dimensions during narrative comprehension and demonstrate that this process does not require cognitively intense forms of principled reasoning