Samples of cell membrane were non-destructively removed from individual, live cells using optical... more Samples of cell membrane were non-destructively removed from individual, live cells using optically trapped beads, and deposited into a supported lipid bilayer mounted on an S-layer protein-coated substrate.
We report a rapid hyperspectral fluorescence lifetime imaging (FLIM) instrument that exploits hig... more We report a rapid hyperspectral fluorescence lifetime imaging (FLIM) instrument that exploits high-speed FLIM technology in a line-scanning microscope. We demonstrate the acquisition of whole-field optically sectioned hyperspectral fluorescence lifetime image stacks (with 32 spectral bins) in less than 40 s and illustrate its application to unstained biological tissue.
We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution ... more We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution organization of the cell membrane during formation of the activating (cytolytic) natural killer (NK) cell immune synapse (IS). This approach revealed that the NK cell plasma membrane is convoluted into ruffles at the periphery, but not in the center of a mature cytolytic NK cell IS. Time-lapse imaging showed that the membrane ruffles formed at the initial point of contact between NK cells and target cells and then spread radialy across the intercellular contact as the size of the IS increased, becoming absent from the center of the mature synapse. Understanding the role of such extensive membrane ruffling in the assembly of cytolytic synapses is an intriguing new goal.
Recent years have seen significant progress in the development of microfabricated systems for use... more Recent years have seen significant progress in the development of microfabricated systems for use in the chemical and biological sciences. [1] Much of this development has been driven by a need to perform rapid measurements on small sample volumes in areas such as chemical synthesis, [2] DNA analysis, [3] drug discovery, [4] pharmaceutical screening, [5] proteomics, [6] and medical diagnostics. [7] It is well recognized that, when compared to macroscale instruments, microfluidic systems engender a number of distinct advantages with respect to speed, analytical throughput, reagent usage, process control, automation, and operational and configurational flexibility. Although all these advantages are directly facilitated by system downscaling (and the associated improvements in both mass and thermal transfer), the instantaneous-reaction volumes that characterize microfluidic systems typically range from a few picoliters to hundreds of nanoliters. This means that analyte detection and identification is a significant challenge and often defines the principal limitations of a microfluidic system. [8] Despite this problem, a variety of detection methods have been successfully transferred and integrated with microfluidic systems. [2]
We describe a novel method for quantitatively mapping fluidic temperature with high spatial resol... more We describe a novel method for quantitatively mapping fluidic temperature with high spatial resolution within microchannels using fluorescence lifetime imaging in an optically sectioning microscope. Unlike intensity-based measurements, this approach is independent of experimental parameters, such as dye concentration and excitation/detection efficiency, thereby facilitating quantitative temperature mapping. Micrometer spatial resolution of 3D temperature distributions is readily achieved with an optical sectioning approach based on two-photon excitation. We demonstrate this technique for mapping of temperature variations across a microfluidic chip under different heating profiles and for mapping of the 3D temperature distribution across a single microchannel under applied flow conditions. This technique allows optimization of the chip design for miniaturized processes, such as on-chip PCR, for which precise temperature control is important.
Samples of cell membrane were non-destructively removed from individual, live cells using optical... more Samples of cell membrane were non-destructively removed from individual, live cells using optically trapped beads, and deposited into a supported lipid bilayer mounted on an S-layer protein-coated substrate.
We report a rapid hyperspectral fluorescence lifetime imaging (FLIM) instrument that exploits hig... more We report a rapid hyperspectral fluorescence lifetime imaging (FLIM) instrument that exploits high-speed FLIM technology in a line-scanning microscope. We demonstrate the acquisition of whole-field optically sectioned hyperspectral fluorescence lifetime image stacks (with 32 spectral bins) in less than 40 s and illustrate its application to unstained biological tissue.
We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution ... more We have applied fluorescence imaging of two-photon linear dichroism to measure the subresolution organization of the cell membrane during formation of the activating (cytolytic) natural killer (NK) cell immune synapse (IS). This approach revealed that the NK cell plasma membrane is convoluted into ruffles at the periphery, but not in the center of a mature cytolytic NK cell IS. Time-lapse imaging showed that the membrane ruffles formed at the initial point of contact between NK cells and target cells and then spread radialy across the intercellular contact as the size of the IS increased, becoming absent from the center of the mature synapse. Understanding the role of such extensive membrane ruffling in the assembly of cytolytic synapses is an intriguing new goal.
Recent years have seen significant progress in the development of microfabricated systems for use... more Recent years have seen significant progress in the development of microfabricated systems for use in the chemical and biological sciences. [1] Much of this development has been driven by a need to perform rapid measurements on small sample volumes in areas such as chemical synthesis, [2] DNA analysis, [3] drug discovery, [4] pharmaceutical screening, [5] proteomics, [6] and medical diagnostics. [7] It is well recognized that, when compared to macroscale instruments, microfluidic systems engender a number of distinct advantages with respect to speed, analytical throughput, reagent usage, process control, automation, and operational and configurational flexibility. Although all these advantages are directly facilitated by system downscaling (and the associated improvements in both mass and thermal transfer), the instantaneous-reaction volumes that characterize microfluidic systems typically range from a few picoliters to hundreds of nanoliters. This means that analyte detection and identification is a significant challenge and often defines the principal limitations of a microfluidic system. [8] Despite this problem, a variety of detection methods have been successfully transferred and integrated with microfluidic systems. [2]
We describe a novel method for quantitatively mapping fluidic temperature with high spatial resol... more We describe a novel method for quantitatively mapping fluidic temperature with high spatial resolution within microchannels using fluorescence lifetime imaging in an optically sectioning microscope. Unlike intensity-based measurements, this approach is independent of experimental parameters, such as dye concentration and excitation/detection efficiency, thereby facilitating quantitative temperature mapping. Micrometer spatial resolution of 3D temperature distributions is readily achieved with an optical sectioning approach based on two-photon excitation. We demonstrate this technique for mapping of temperature variations across a microfluidic chip under different heating profiles and for mapping of the 3D temperature distribution across a single microchannel under applied flow conditions. This technique allows optimization of the chip design for miniaturized processes, such as on-chip PCR, for which precise temperature control is important.
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Papers by Neil Ma