The intercell dynamics of T cells and dendritic cells in a lymph node-on-a-chip flow device.

T cells play a central role in immunity towards cancer and infectious diseases. T cell responses are initiated in the T cell zone of the lymph node (LN), where resident antigen-bearing dendritic cells (DCs) prime and activate antigen-specific T cells passing by. In the present study, we investigated the T cell : DC interaction in a microfluidic device to understand the intercellular dynamics and physiological conditions in the LN. We show random migration of antigen-specific T cells onto the antigen-presenting DC monolayer independent of the flow direction with a mean T cell : DC dwell time of 12.8 min and a mean velocity of 6 µm min(-1). Furthermore, we investigated the antigen specific vs. unspecific attachment and detachment of CD8(+) and CD4(+) T cells to DCs under varying shear stress. In our system, CD4(+) T cells showed long stable contacts with APCs, whereas CD8(+) T cells presented transient interactions with DCs. By varying the shear stress from 0.01 to 100 Dyn cm(-2), it was also evident that there was a much stronger attachment of antigen-specific than unspecific T cells to stationary DCs up to 1-12 Dyn cm(-2). The mechanical force of the cell : cell interaction associated with the pMHC-TCR match under controlled tangential shear force was estimated to be in the range of 0.25-4.8 nN. Finally, upon performing attachment & detachment tests, there was a steady accumulation of antigen specific CD8(+) T cells and CD4(+) T cells on DCs at low shear stresses, which were released at a stress of 12 Dyn cm(-2). This microphysiological model provides new possibilities to recreate a controlled mechanical force threshold of pMHC-TCR binding, allowing the investigation of intercellular signalling of immune synapses and therapeutic targets for immunotherapy.

Nanofiltering via integrated liquid core waveguides.

We demonstrate and describe how nanoporous liquid core waveguides can exclude scattering particles, making them an ideal integrated platform for analysis of turbid solutions. Milk with 0.5% fat showed an optical propagation loss of 0.05 dB/mm at 633 nm in nanoporous waveguides compared to the 10.6 dB/mm loss in standard cuvette measurements. To examine the nanofiltering effect, waveguides were infiltrated with solutions containing Rhodamine B molecules (1 nm) and 22 nm red fluorescing polystyrene beads. With fluorescence spectroscopy we show that 22 nm beads are excluded, while Rhodamine B molecules penetrate the waveguides. This is further confirmed by fluorescence microscopy, also revealing a homogenous distribution of Rhodamine in the waveguide volume.

UV patterned nanoporous solid-liquid core waveguides.

Nanoporous Solid-Liquid core waveguides were prepared by UV induced surface modification of hydrophobic nanoporous polymers. With this method, the index contrast (deltan = 0.20) is a result of selective water infiltration. The waveguide core is defined by UV light, rendering the exposed part of a nanoporous polymer block hydrophilic. A propagation loss of 0.62 dB/mm and a bend loss of 0.81 dB/90 degrees for bend radius as low as 1.75 mm was obtained in these multimode waveguides.