Fig. 7 Classification of cell adhesion measurement techniques[117]
AFM is now commonly used to measure the adhesion of bacteria to
surfaces. The AFM developed by Binnig et al. [121]uses force-sensitive cantilevers to probe the interaction forces between
the needle tip and the character, thereby obtaining a microscopic
picture of the sample surface on the nanometre scale. Single-cell force
spectroscopy (SCFS) is a bacterial probe prepared by immobilizing a
single bacterium on a micro-cantilever, which can be used to measure the
interaction forces between bacteria and various surfaces and between
bacteria and bacteria as shown in Figure 8 [122].
First, individual cells are immobilized at the free end of a non-tilted
cantilever beam [123], and the process of
functionalizing the probe is achieved by attaching individual cells to
the AFM cantilever with agglutinin, ensuring that the surface of the
cell is not modified. The functionalized examination then comes into
contact with the character or another cell and the cantilever is pulled
back at a constant rate to separate the cell from its contact end, and
the deflection of the cantilever is detected using a laser beam focused
on the top of the cantilever and reflected a quadrant photodiode[124]. The cantilever beam deflection is
proportional to the force acting between the surface and the cell,
resulting in a force-distance curve [122]. AFM can
measure the adhesion of cells attached to the cantilever to the
substrate surface and the adhesion of cells immobilized on the substrate
to the cantilever [125].