Biological agent detection has captured the attention of many researchers over the last few years. The present research explores the possibility of directly measuring the diffusion coefficients of sub-micron particles as a means of pathogen detection. At a constant temperature, the diffusion coefficient is simply a function of the drag on the particle. If the particles are functionalized with antibodies against a specific analyte and introduced into a sample containing that analyte, binding of the analyte with the particles will increase the particles' hydrodynamic drag. This results in a decrease in diffusion, which is measured by a particle tracking algorithm. The reduction in diffusion is correlated with the amount of analyte present. Sensitivity to experimental conditions is also explored and it is shown that alternate methods like optical traps provide an even better technique for biological agent detection.
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