Lysosomes are membrane-bound organelles responsible for the transport and degradation of intracellular and extracellular cargo. The intracellular motion of lysosomes is both diffusive and active, mediated by motor proteins moving lysosomes along microtubules. We sought to determine how lysosome diameter influences lysosome transport. We used osmotic swelling to double the diameter of lysosomes, creating a population of enlarged lysosomes. This allowed us to directly examine the intracellular transport of the same organelle as a function of diameter. Lysosome transport was measured using live cell fluorescence microscopy and single particle tracking. We find, as expected, the diffusive component of intracellular transport is decreased proportional to the increased lysosome diameter. Active transport of the enlarged lysosomes is not affected by the increased lysosome diameter.

Both natural and synthetic brominated furanones are known to inhibit biofilm formation by bacteria, but their toxicity to mammalian cells is often not reported. Here, we designed and synthesized a new class of brominated furanones (BBFs) that contained a bicyclic structure having one bromide group with well-defined regiochemistry. This class of molecules exhibited reduction in the toxicity to mammalian cells (human neuroblastoma SK-N-SH) and did not inhibit bacteria (Pseudomonas aeruginosa and Escherichia coli) growth, but retained the inhibitory activity towards biofilm formation of bacteria. In addition, all the BBFs inhibited the production of virulence factor elastase B in P. aeruginosa. To explore the effect of BBFs on quorum sensing, we used a reporter gene assay and found that 6-BBF and 7-BBF exhibited antagonistic activities for LasR protein in the lasI quorum sensing circuit, while 5-BBF showed agonistic activity for the rhlI quorum sensing circuit. This study suggests that structural variation of brominated furanones can be designed for targeted functions to control biofilm formation.

This work reports the resistance to protein adsorption and bacterial biofilm formation by chiral monolayers of polyol-terminated alkanethiols surrounding micrometer-sized patterns of methyl-terminated alkanethiols on gold films. We discover that patterned surfaces surrounded by chiral polyol monolayers can distinguish different stages of biofilm formation. After inoculation on the surfaces, bacteria first reversibly attached on the chiral polyol monolayers. Over time, the bacteria detached from the polyol surfaces, and attached on the hydrophobic micropatterns to form biofilms. Interestingly, while both enantiomers of gulitol- and mannonamide-terminated monolayer resisted adsorption of proteins (bovine serum albumin, lysozyme, and fibrinogen) and confined biofilms formed on the micropatterns, the monolayers formed by the racemic mixture of either pair of enantiomers exhibited stronger antifouling chemistry against both protein adsorption and biofilm formation than monolayers formed by one enantiomer alone. These results reveal the different chemistries that separate the different stages of biofilm formation, and the stereochemical influence on resisting biofoulings at a molecular-level.

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This work studies the phase separations between polymers and a small molecule in a common aqueous solution that do not have well-defined hydrophobic-hydrophilic separation. In addition to poly(acrylamide) (PAAm) and poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP) also promotes liquid crystal (LC) droplet formation by disodium cromoglycate (5'DSCG) solvated in water. In the presence of these polymers, the concentration of 5'DSCG needed for forming LC droplets is substantially lower than that needed for forming an LC phase by 5'DSCG alone. To define the concentration ranges that 5'DSCG molecules form liquid crystals (either as droplets or as an isotropic-LC mixture), we constructed ternary phase diagrams for 5'DSCG, water, and a polymer - PVA, PVP, or PAAm. We discovered that PAAm with high molecular weight promotes LC droplet formation by 5'DSCG more effectively than PAAm with low molecular weight. At the same weight percentage, long-chain PAAm can cause 5'DSCG to form LC droplets in water, whereas short-chain PAAm does not. Poly(vinyl pyrrolidone) (PVP), which has functional groups that are more dissimilar to 5'DSCG than PVA and PAAm, promotes LC droplet formation by 5'DSCG more effectively than either of the other two polymers. Additionally, small angle neutron scattering data revealed that the assembly structure of 5'DSCG promoted by the presence of PVA is similar to the thread structure formed by 5'DSCG alone. Together, these results reveal how noncovalent polymerization can be promoted by mixing thermodynamically incompatible molecules and elucidate the basic knowledge of nonamphiphilic colloidal science.