Fig 1.
The optical diffusometric platform.
(A) Schematic of the optical diffusometry. (B) The relationship of Brownian motion and the particle size change due to the bacterium-particle binding. The corresponding diffusivity values are derived from the cross-correlation algorithm. A large particle diameter results in a narrow correlation peak.
Fig 2.
Conceptual diagram of the computational procedure of the cross-correlation algorithm for a series of particle images.
The particle images were analyzed by spatially cross-correlation algorithm and summed up in the correlation domain to achieve an ensemble average.
Fig 3.
(A) Optical microscopic image of a single P. aeruginosa bacterium (arrow head) attaching to a 2-μm antibody-conjugated particle (arrow). The scale bar is 5 μm. (B) SEM images of a single P. aeruginosa bacterium attaching to a 2-μm antibody-conjugated particle and the close-up of the coarse surface of the functionalized particle. The scale bar is 1 μm. (C) Efficacy and specificity of particles with different surface modifications attached to P. aeruginosa. In the annotation, none (control) means non-modified, NH2 means amine-modified, COOH means carboxylate-modified, Anti-PA means anti-P. aeruginosa polyclonal antibody, Anti-SA means anti-S. aureus polyclonal antibody, and # means no observation.
Fig 4.
Influences of P. aeruginosa on Brownian motion of particles.
(A) A series of images showing the conjugation of functionalized particles and different numbers of P. aeruginosa (yellow arrow head). The scale bar is 2 μm. (B) Mean diffusivity values of single particles attached with or without live P. aeruginosa. (C) Diffusivity values of single particles attached with different numbers of dead P. aeruginosa. (D) Diffusivity values of populations of particles decline with the increased bacterium density. P means particles, LB means live bacteria, DB means dead bacteria, number before DB means the number of bacteria or the ratio of bacteria to particles, S is the slope of regression line of particles with bacteria, and Sp is the slope of regression line of particles without bacteria.
Fig 5.
Simulation of the variation in the Brownian motion with different particle sizes and bacterium densities.
The symbol P means particles, DB means dead bacteria, S is the slope of regression line of particles with bacteria, and Sp is the slope of regression line of particles without bacteria. Exp. 1. denotes the data from Fig 4C. Exp. 2. denotes the data from Fig 4D.
Fig 6.
The AST evaluation of P. aeruginosa in response to gentamicin.
(A) Microscopic images of bacteria-binding particles during bacterial growth with or without gentamicin (2 μg/mL). The scale bar is 2 μm. (B) Temporal diffusivity changes of populations of particles attached with bacteria in the presence or absence of gentamicin (0.02, 0.5, and 2 μg/mL). S is the slope of regression line and S0 is the regression line slope of particles measured at 0 min. Values at the same time point not sharing a common letter are significantly different (P < 0.05).