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].