Lawrence Berkeley National Laboratory

Microarrays of single macrophage cell based sensors were developed and demonstrated for real time bacterium detection by synchrotron FTIR microscopy. The cells were patterned on gold-SiO2 substrates via a surface engineering technique by which the gold electrodes were immobilized with fibronectin to mediate cell adhesion and the silicon oxide background were passivated with PEG to resist protein adsorption and cell adhesion. Cellular morphology and IR spectra of single, double, and triple cells on gold electrodes exposed to lipopolysaccharide (LPS) of different concentrations were compared to reveal the detection capabilities of these biosensors. The single-cell based sensors were found to generate the most significant IR wave number variation and thus provide the highest detection sensitivity. Changes in morphology and IR spectrum for single cells exposed to LPS were found to be time- and concentration-dependent and correlated with each other very well. FTIR spectra from single cell arrays of gold electrodes with surface area of 25 mu-m2, 100 mu-m2, and 400 mu-m2 were acquired using both synchrotron and conventional FTIR spectromicroscopes to study the sensitivity of detection. The results indicated that the developed single-cell platform can be used with conventional FTIR spectromicroscopy. This technique provides real-time, label-free, and rapid bacterial detection, and may allow for statistic and high throughput analyses, and portability.