As the biofilm matures, nutrient resources are consumed in large quantities, and toxic substances will continue to accumulate [
34,
35]. Therefore, to obtain more nutrients, the bacterial cells of the biofilm disperse from the biomaterial surface and migrate to other areas of the medical implant, thereby spreading the infection [
8,
16]. The dispersion mechanism in bacteria generally occurs in three stages: first, cells leave the microcolony; second, cells move to a new substrate; and third, cells attach to the new substrate and start a new biofilm formation process [
11,
36]. In fact, biofilm dispersion can be divided into active and passive modes [
37]. When bacteria experience environmental stresses such as antimicrobial pressure and nutrient deficiency, they will actively dissociate from the implanted surface [
38]. In the process of biofilm dispersion, some mechanisms are favorable for bacterial cell dispersion, such as the dissolution of EPSs [
8]. Nutrient deprivation in biofilms stimulates small molecules of the fatty acid DSF (cis-11-methyl-2-dodecenoic acid) to trigger autophosphorylation and induce the degradation of c-di-GMP, leading to the dissolution of EPSs, which releases some of the planktonic cells [
39,
40]. In addition, in the process of active dispersion, the expression of genes related to bacterial motility caused by flagellum synthesis is upregulated, while the expression of genes related to bacterial attachment is downregulated, thus facilitating bacterial detachment [
35].
Passive dispersion of biofilm depends on external factors, such as enzyme degradation of the biofilm matrix and shear forces [
37]. The microbial community within the biofilm produces different saccharolytic enzymes that digest the polysaccharides that stabilize the biofilm structure, helping to release the microbial surfaces to new colonization areas [
16,
31]. For example, in alginate, Pel and Psl polysaccharides are the skeleton components of the
P. aeruginosa biofilm supporting structure, which can help bacteria to absorb nutrients and communicate signals between cells [
41]. Alginate lyases have been shown to be used for the cleavage and subsequent separation of EPS substrates, while the extracellular polysaccharide hydrolases PelA and PslG induce biofilm dispersion and prevent biofilm formation [
16,
42,
43]. PelA was more effective in dispersing biofilms with Pel as the main extracellular polysaccharide, while PslG was most effective in removing biofilms formed with Psl as the main extracellular polysaccharide [
44]. Previously, our research group also overexpressed PelA and PslG enzymes in
P. aeruginosa engineered bacteria through synthetic biology, and lysed the engineered bacteria in active and passive ways to release two types of extracellular polysaccharide hydrolases, PelA and PslG, thus destroying cytoskeletal components Psl and Pel. The result was destruction of the
P. aeruginosa biofilm [
45]. In addition to enzymatic degradation of biofilm matrixes, physical means such as shear force are important factors for passive dispersion of biofilms [
46]. A sudden increase in shear forces causes the cells to be immediately released from the biofilm, resulting in the dispersion of the biofilm [
47]. For example, during the formation of
Streptococcus mutans biofilms, a 10-fold increase in shear forces resulted in an 85% reduction in the biomass of the biofilm [
48]. In addition, ultrasonic waves, laser-induced shock waves, and other technologies have been found to passively disperse biofilms [
37]. Ultrasonic treatment significantly reduced
E. coli and
S. aureus biofilms on a stainless steel surface [
49,
50]. Laser-induced shock waves destroyed biofilms grown on different types of medical devices by generating plasma, and although the shock waves themselves were not harmful to the bacteria, the biofilms exposed to the shock waves were more sensitive to antibiotics than those that were not exposed [
51]. To summarize, both active and passive methods can facilitate the dispersion of biofilm. However, once biofilm cells that were dispersed and settled on a new surface are stimulated by adverse conditions, the isolated microbial cells upregulate the expression of flagellar proteins to help them move quickly and return to a floating state on the surface. The bacteria then reform the biofilm in the right environment, causing continuous infection [
8,
52].