We present an optical approach for intracellular delivery of molecules contained within oxidation-sensitive polymersomes. The photosensitizer ethyl eosin is associated with the polymersome membrane to oxidatively increase the hydrophilicity of the hydrophobic block under optical excitation. This optofluidic interaction induces rapid polymersome rupture and payload release via the reorganization of the aggregate structure into smaller diameter vesicles and micelles. When the particles are endocytosed by phagocytes, such as RAW macrophages and dendritic cells, the polymersomes' payload escapes the endosome and is released in the cell cytosol within a few seconds of illumination. The released payload is rapidly distributed throughout the cytosol within milliseconds. The presented optofluidic method enables fast delivery and distribution throughout the cytosol of individual cells, comparable to photochemical internalization, but a factor of 100 faster than similar carrier mediated delivery methods (e.g., liposomes, polymersomes, or nanoparticles). Due to the ability to simultaneously induce payload delivery and endosomal escape, this approach can find applications in detailed characterizations of intra- and intercellular processes. As an example in quantitative cell biology, a peptide antigen was delivered in dendritic cells and MHC I presentation kinetics were measured at the single cell and single complex level.

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Single cell investigations have enabled unexpected discoveries, such as the existence of biological noise and phenotypic switching in infection, metabolism and treatment. Herein, we review methods that enable such single cell investigations specific to metabolism and bioenergetics. Firstly, we discuss how to isolate and immobilize individuals from a cell suspension, including both permanent and reversible approaches. We also highlight specific advances in microbiology for its implications in metabolic engineering. Methods for probing single cell physiology and metabolism are subsequently reviewed. The primary focus therein is on dynamic and high-content profiling strategies based on label-free and fluorescence microspectroscopy and microscopy. Non-dynamic approaches, such as mass spectrometry and nuclear magnetic resonance, are also briefly discussed.

We report the demonstration of a compact, all-solid-state polymer laser system comprising of a Gallium Nitride (GaN) semiconductor diode laser as the pump source. The polymer laser was configured as a surface emitting, distributed Bragg reflector laser (DBR), based on a novel energy transfer blend of Coumarin 102 and the conjugated polymer poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene). In this configuration, diode pumping was possible both due to the improved quality of the resonators and the improved harvesting of the diode laser light.

We demonstrate an optofluidic evanescent laser based on a solid circular distributed feedback grating with the dye solution acting as the cladding layer. The laser mode is confined within the grating and experiences optical gain via the interaction between its evanescent component with the dye solution. Above a pump energy of 9.5 J / pulse, the laser exhibited single mode operation at 571 nm. Stable, narrow-linewidth emission was observed for a wide range of fluid refractive indices, even for those lower than of polydimethylsiloxane. We attribute this property to the evanescent coupling of the laser mode with the fluidic gain. 8 In all aforementioned structures, the guided mode is confined inside the fluid gain medium and thus the refractive index of the solution determines the emission wavelength. Although this enables the tuning of the lasing wavelength by fluidic mixing, in practice stable and single mode operation require high control of the refractive index of the fluid and moderate flow rates across the waveguides. In addition, due to the relatively high index of polydimethylsiloxane ͑PDMS͒ ͑n PDMS = 1.4218͒, several buffers cannot be directly employed for waveguiding in PDMS based optofluidic lasers.To overcome this, evanescent field dye lasers have been proposed in the past.9,10 In these lasers, the liquid gain medium surrounds a solid waveguide and is optically excited. The excited chromophores in the near-field of the waveguide are evanescently coupled to the laser mode providing the optical gain. To date, several evanescent optofluidic dye lasers have been demonstrated, primarily based on whispering gallery mode resonators such as infilled silica capillaries or fibers embedded in dye solutions.11-13 These structures are usually characterized by multimode emission spectra. More recently, evanescent lasers operating in the telecommunication wavelength range have found applications in the field of silicon photonics.14 In this letter, we demonstrate an optofluidic evanescent dye laser, exhibiting single mode operation. It comprises of a solid second order circular distributed feedback ͑DFB͒ grating and a PDMS chamber filled with dye solution. The thin layer of the solution serves as the cladding and covers the entire surface of the solid DFB cavity. Due to the high modal confinement in the solid core, the mode selection and lasing wavelength are primarily determined by the solid DFB cavity. In comparison to liquid core dye lasers, 7 stable and single mode operation can be achieved for a wide range of refractive indices of the dye solution.In Fig. 1, a cross-sectional schematic of the circular DFB resonator is illustrated. It is made of the negative photoresist SU-8 ͑refractive index n SU-8 = 1.59͒ patterned on top of silicon dioxide layer ͑n SiO 2 = 1.46͒ on a silicon substrate. The PDMS ͑n PDMS = 1.4128͒ forms a microfluidic chamber which envelops the entire surface of the solid DFB cavity. By infilling the dye solution into the PDMS chamber, a thin layer of liquid gain medium is formed on top of the gra...

A dilute fluorene copolymer produces enhanced optical amplification. High gain with 1000 times optical amplification and a long lifetime is achieve in only 1mm of the material, and exciton–exciton annihilation is suppressed.

The funders had changing over time in response to growth conditions. We characterized this phenomenon using bulk liquid culture experiments, colony growth tracking, flow cytometry, single-cell timelapse microscopy, transcriptomics, and genome resequencing. Finally, we used mathematical modeling to better understand the processes by which cells change phenotype, and found evidence for both stochastic, bidirectional phenotypic diversification and responsive, directed phenotypic shifts, depending on the growth substrate and the presence of toxin.

We report the demonstration of low order distributed feedback ͑DFB͒ optofluidic dye lasers with reduced threshold. The laser chips were realized in polydimethylsiloxane using replica molding with two masters. A comparison between first, second, and third order DFB dye lasers was performed, while the second order DFB dye laser exhibited the lowest pump threshold of 78 nJ/pulse. Compared to previous reports on higher order Bragg grating structures, the pump threshold in this work is approximately 30-fold lower than the state of the art due to the reduction in the cavity losses and the more efficient pumping configuration. © 2009 American Institute of Physics. ͓DOI: 10.1063/1.3079799͔In recent years, there has been rapid progress in developing optofluidic technology which has enabled a broad spectrum of novel optical toolboxes for integrated optics and lab-on-a-chip applications. [1][2][3] To this end, optically pumped microfluidic dye lasers are of particular interest, since they exhibit the advantages of laser emission, combined with cost-effective processing and a wide choice of emission wavelengths.Several resonator configurations have been demonstrated for microfluidic dye lasers such as the Fabry-Perot cavity, 4 microdroplet, 5 capillary tube, 6 and photonic crystal fiber, 7 while the distributed feedback ͑DFB͒ resonators were the more efficient ones which enable narrow linewidth single mode lasing operation and easy fabrication. 8,9 A DFB microfluidic dye laser was first demonstrated by Balslev and Kristensen 8 who used a 130th Brag grating in a multimode waveguide with a threshold of 20 J / pulse. Then a pure single mode optofluidic dye laser with significant lower pump threshold of 3.2 J / pulse was achieved by Li et al. 9 However, microfluidic dye lasers still rely on bulky pumping laser systems due to their high thresholds, thus placing a restriction on their practicality. Hence, further reduction in the lasing threshold is highly desirable especially for compact diode pumping, as recently demonstrated for solid state organic semiconductor lasers. 10 In this letter, we present low order liquid core DFB microfluidic dye lasers with reduced lasing threshold. Our strategy to lower the pump threshold was based on reducing the out of plane diffraction losses by employing low order diffraction gratings and increasing the pumping efficiency by a longitudinal pumping geometry. The threshold gain g th for a DFB laser can be expressed aswhere a is the propagation loss coefficient in the cavity due to optical scattering, absorption, and out of plane diffraction and a m is the loss coefficient due to the finite reflection from the grating, also referred to as mirror loss coefficient. 11 By decreasing the grating order, both propagation loss a and mirror loss a m can be decreased due to the reduced out of plane diffraction and enhanced in-plane coupling, respectively. By overcoming the previous technical limitation, 9 we developed a two-step replica molding process that allowed fabricating low order DFB structures wi...