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Micropatterning of hydrogel has brought innovative outcomes in fundamental and applied material sciences. Previous approaches have mainly been dedicated to fabricate arrays of bulk hydrogel beads, which have inherent challenges including loading ability, scalability, specificity and versatility. Here we present a methodology to create hollow microcapsule arrays from sessile microdroplets. The difference in wettability between hydrophilic and hydrophobic surfaces enables self-partitioning of liquid into microdroplet arrays, serving as microreservoirs to load complementarily-functionalized host-guest polymers, cucurbit[8]uril-threaded highly-branched polyrotaxanes (HBP-CB[8]) and naphthyl-functionalized hydroxyethyl cellulose (HEC-Np). The interfacial dynamic complexation between positively-charged HBP-CB[8] and HECNp occurred in the presence of negatively-charged surfactants, resulting in condensed supramolecular hydrogel skins. The hydrogel microcapsules were uniform in size, and were developed to encapsulate target cargos in a robust and well-defined manner. Moreover, the microcapsule substrates were further used for surface enhanced Raman spectroscopy (SERS) sensing upon loading of gold nanoparticles. This facile assembly of microcapsule arrays has potential applications in controlled cargo delivery, bio-sensing, high throughput analysis and sorting.

RAD51 is a recombinase involved in the homologous recombination of double-strand breaks in DNA. RAD51 forms oligomers by binding to another molecule of RAD51 via an ‘FxxA’ motif, and the same recognition sequence is similarly utilised to bind BRCA2. We have tabulated the effects of mutation of this sequence, across a variety of experimental methods and from relevant mutations observed in the clinic. We use mutants of a tetrapeptide sequence to probe the binding interaction, using both isothermal titration calorimetry and X-ray crystallography. Where possible, comparison between our tetrapeptide mutational study and the previously reported mutations is made, discrepancies are discussed and the importance of secondary structure in interpreting alanine scanning and mutational data of this nature is considered.

Protein-protein interactions are difficult therapeutic targets, and inhibiting pathologically relevant interactions without disrupting other essential ones presents an additional challenge. Herein we report how this might be achieved for the potential anticancer target, the TPX2-importin-α interaction. Importin-α is a nuclear transport protein that regulates the spindle assembly protein TPX2. It has two binding sites--major and minor-to which partners bind. Most nuclear transport cargoes use the major site, whereas TPX2 binds principally to the minor site. Fragment-based approaches were used to identify small molecules that bind importin-α, and crystallographic studies identified a lead series that was observed to bind specifically to the minor site, representing the first ligands specific for this site. Structure-guided synthesis informed the elaboration of these fragments to explore the source of ligand selectivity between the minor and major sites. These ligands are starting points for the development of inhibitors of this protein-protein interaction.

Gold nanoparticles coated with a poly(N-isopropylacrylamide) (pNIPAM) shell undergo reversible dis/assembly below and above the critical temperature of 32°C. Loading these particles into microdroplets at high density creates light-driven artificial chromatophores. Triggering the nanoparticle assembly gives dramatic color changes from nanoparticle localization at the base of the droplets, resembling zebrafish melanophores. These reversible chromatophore states can be switched by both bulk and optical heating, explored here in individual microdroplets and in large cm^2 areas of close-packed droplets. Illuminating chromatophores off-center with a tightly focused beam results in droplet locomotion via two separate mechanisms, Marangoni interfacial shear and gas bubble propulsion, depending on optical power.