Information-Rich Photon Imaging of Cells

Cells and tissue are complex materials whose heterogeneity and dynamic changes are principally driven at the micron and sub-micron size scales, with underlying events ranging upwards from microsecond time scales, and measurement also based upon faster photo-electronic events of molecules (eg fluorescent and Raman emission from picosecond to nanosecond timescales). Advances in high energy physics and space research have made possible a fast photon imaging detector with >1000 channels each measuring individual photon arrivals to picosecond temporal sensitivity. We aim to develop and use this imaging detector to capture the high spatial and temporal complexity of cells and tissue. In particular, our objectives concern maximising the photon information available to unravel complex multi-component signals, including within background noise, below the visibility of present measurement and automated platforms, which underlie challenges in quantitative imaging and bioassays of live cells and tissue.

The Space Research Centre at the University of Leicester have developed an Image Charge approach to read photon detections from image intensifiers onto electrodes. A multi-layer ceramic substrate with silicon resistive layer will be developed with a small pore size multi-channel plate intensifier to provide high temporal sensitivity and spatial resolution. CERN have developed an ultra fast front-end preamplifier-discriminator chip (NINO) for a precision time Time-Of-Flight detector for the Large Hadron Collider (LHC). The performance of Image Charge can be matched by measurement of the induced charge footprints of photons by the NINO chip. A high channel density NINO readout will be scaled to 1024 (32 x 32) photon measurement channels each with <25 ps photon timing sensitivity. The University of Manchester have investigated non-stop processing of the photon train detected following laser pulses (delta) and continuous wave (CW) illumination. The non-linear distribution of the photon delay times indicates that only small bunches (typically 2-4 photons) are detected with delay times shorter than the recovery time of detectors. We expect that the proposed 1024 channel photon timing device would enable time-resolved spectroscopy from both delta- and CW illumination at multiple spatial locations. This would allow presently separate time-resolved (eg fluorescent lifetime, single molecule fluorescence, Raman) and new measurements to be performed using the same detector device. Given increased information, the ability to de-convolute multiple signals will be investigated using multi-exponential fitting algorithms developed for encryption, which have enabled free and bound fluor signals to be resolved. The imaging detector will be evaluated for multiplexed bioassays and multi-parametric imaging, collaborating with Gray Cancer Institute to benefit from advanced platforms for single cell cytometry and tissue bioimaging.