Table 7.

Biomedical studies performed on different biofilm platforms to evaluate the initial adhesion, as well as the biofilm formation and treatment under the defined shear conditions.

Platform	Field	Biofilm Stage	Study Aim	Hydrodynamics	Assay Time	Surface Material	Organisms	Concluding Remarks	References
Modified Robbins device	General medical devices	Biofilm formation	Effect of flow rate variation on mass transfer and biofilm development	Flow rates of 374 and 242 L h−1, corresponding to shear stresses between 0.183 and 0.511 Pa	9 days	Polyvinyl chloride	Escherichia coli	Biofilm formation was favored at the lowest flow rate because shear stress effects were more important than mass transfer limitations. This flow cell system generates wall shear stresses that are similar to those found in some biomedical settings.	[111]
	Urinary devices	Biofilm formation	Evaluation of the potential of antiadhesive coatings when immobilized onto medical-grade polyurethane	Flow rate of 53 mL s−1, corresponding to 15 s−1	48 h	Polyurethane Polyurethane coated with CyanoCoating through a polydopamine layer application, or O2- plasma, N2-plasma, and O3 activation	Escherichia coli	When the coating was produced via O3 activation, CyanoCoating was able to decrease the biofilm biovolume by 88% and the surface coverage by 95%, compared to the uncoated surface.	[50]
			Investigation of the role of uncommon bacteria on the Escherichia coli microbial consortium	Flow rate of 300 mL min−1, corresponding to 15 s−1	72 h	Silicone rubber	Escherichia coli Delftia tsuruhatensis	E. coli and D. tsuruhatensis were able to form single- and dual-species biofilms. Both bacteria tend to co-aggregate and cooperate over time, persisting in a stable microbial community.	[128]
			Development of new functional coatings using magnetron co-sputtering to deposit triple TiO2/SiO2/Ag nanocomposite thin films	Flow rate of 53 mL s−1, corresponding to 15 s−1	48 h	Glass TiO2/SiO2 coated glass with different Ag contents (0 to 19.8 at %)	Escherichia coli	Biofilm formation was reduced down to 92% compared to a control glass surface. The coatings are promising candidates for antimicrobial protection of urinary tract devices for at least 48 h, suggesting benefits over longer periods.	[49]
Flow chamber	General medical devices	Adhesion	Assessment of interactions of bacteria with specific biomaterial surface chemistries under flow conditions	50, 500, 1000, and 2000 s−1	2 h	Glass Glass with alkyl silane monolayers	Staphylococcus epidermidis	The increase in the ionic strength enhanced adhesion to the different surfaces, in accordance with the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, under low shear rates. The increase in the shear rate restricted the predictability of the theory.	[129]
			Effect of shear stress on bacterial adhesion to biomedical materials	Flow rates of 2 and 4 mL s−1, corresponding to shear stresses of 0.01 and 0.022 Pa	0.5 h	Glass Polydimethylsiloxane Poly(L-lactic acid)	Escherichia coli	Similar adhesion rates were obtained on glass and polydimethylsiloxane. The highest adhesion rates were obtained on glass and polydimethylsiloxane, and the lowest on poly(L-lactic acid).	[40,53]
			Effect of fluid composition and shear conditions on bacterial adhesion to an antifouling peptide-coated surface	Flow rates of 2 and 4 mL s−1, corresponding to 15 and 30 s−1	0.5 h	Glass Peptide-coated glass Poly(L-lactic acid)	Escherichia coli	Adhesion reductions of 40–50% were attained at a shear rate of 15 s−1 on the peptide-coated surfaces compared with glass. The performance of the peptide-based antifouling coating was superior to poly(L-lactic acid).	[57]
			Effect of shear stress on bacterial adhesion to antifouling polymer brushes	Flow rates of 2 and 4 mL s−1, corresponding to 0.010 and 0.024 Pa	0.5 h	Glass Poly[N-(2-hydroxypropyl) methacrylamide] brush Poly[oligo(ethyleneglycol) methyl ether methacrylate] brush	Escherichia coli	Both polymer brushes reduced the initial adhesion up to 90% when compared to glass.	[56]
			Evaluate the antiadhesive activity of carbon nanotube composites	Flow rate of 2 mL s−1, corresponding to 15 s−1	0.5 h	Polydimethylsiloxane Carbon nanotube/polydimethylsiloxane composites	Escherichia coli	The introduction of carbon nanotubes composites in the polydimethylsiloxane matrix yielded less bacterial adhesion than the polydimethylsiloxane alone. Less adhesion was obtained on the composites with pristine rather than functionalized carbon nanotubes. Incorporation of higher amounts of carbon nanotubes in polymer composites can affect bacterial adhesion by more than 40%. Composites enabling a 60% reduction in cell adhesion were obtained by carbon nanotube treatment by ball-milling.	[23,130]
	Devices and implants	Adhesion	Prevention of microbial adhesion to silicone rubber using polyacrylamide brush coatings	Flow rate of 0.025 mL s−1, corresponding to 10 s−1	4 h	Silicone wafers Silicone rubber Polyacrylamide brushes	Staphylococcus aureus Streptococcus salivarius Escherichia coli Candida albicans	A high reduction (52–92%) in microbial adhesion to the polyacrylamide brushes was observed compared to untreated silicon surfaces. The polymer brush did not cause surface deterioration and discouraged microbial adhesion, even after 1-month of exposure to physiological fluids.	[131,132]
	Implanted medical devices	Adhesion	Study of adhesion of bacterial and yeast strains to a poly(ethylene oxide) brush covalently attached to the glass	Flow rate of 0.025 mL s−1, corresponding to 10 s−1	4 h	Glass Poly(ethylene oxide) brushes on glass	Staphylococcus epidermidis Staphylococcus aureus Streptococcus salivarius Escherichia coli Pseudomonas aeruginosa Candida albicans Candida tropicalis	The poly(ethylene oxide) brush yielded more than 98% reduction in bacterial adhesion, although for the more hydrophobic P. aeruginosa a smaller reduction was observed. For yeast species, adhesion suppression was less effective than for the bacteria.	[133]
			Evaluation of the role of surface free energy on bacterial adhesion to plasma-modified films	50 and 200 s−1	2.5 h	Polyethylene terephthalate Plasma treated polyethylene terephthalate	Staphylococcus epidermidis	Plasma treatments reduced bacterial adhesion, in comparison to the untreated polymer. The ageing effect and the subsequent decrease in the surface free energy seemed to favor bacterial adhesion and aggregation. The increase in the shear rate restricted the predictability of the thermodynamic models.	[134]
		Adhesion and biofilm formation	Evaluation of the effectiveness of different formulations of a biomedical-grade polyetherurethane at inhibiting bacterial colonization under flow conditions	2.03 Pa	Adhesion: 2, 4 and 6 h Biofilm: 8, 20 and 24 h	Polyetherurethane Polyetherurethane with triglyme Polyetherurethane with poly(butyl methyacrylate) barrier membrane releasing ciprofloxacin	Pseudomonas aeruginosa	The rate of adherent cell accumulation was zero for the polyetherurethane with a poly(butyl methyacrylate) barrier membrane releasing ciprofloxacin.	[135]
	Surgical, catheters, and haemodialysis devices	Adhesion	Evaluation of the adhesion behavior of bacterial strains to hydrophilic and hydrophobic surfaces using theoretical predictions	Flow rate of 0.025 mL s−1, corresponding to 6 s−1	2 h	Glass Indium tin oxide-coated glass	Pseudomonas stutzeri Staphylococcus epidermidis	P. stutzeri has a much better adhesion rate than S. epidermidis for both material surfaces. Both bacterial strains adhered better to the hydrophobic indium tin oxide-coated glass than to the hydrophilic glass.	[136]
	Orthopedic implants	Adhesion	Study the bacterial adhesion to polymers that show promise as orthopedic materials	Flow rate of 1 mL min−1, corresponding to a shear rate of 1.9 s−1	1 h	Poly(orthoester) Poly(L-lactic acid) Poly(ether ether ketone) Polysulfone Polyethylene	Staphylococcus epidermidis Pseudomonas aeruginosa Escherichia coli	Tryptic soy broth decreased adhesion to polymers, when compared to phosphate-buffered saline. The estimated values of the free energy of adhesion correlated with the amount of adherent P. aeruginosa. There was 50% more adhesion of E. coli and P. aeruginosa on poly(orthoester) and poly(L-lactic acid) pre-exposed to hyaluronic acid. P. aeruginosa was the most adherent strain, while S. epidermidis was the least adherent strain.	[137]
	Urinary devices	Adhesion	Examination of the ability of probiotic strains to displace adhering cells from hydrophobic and hydrophilic substrata	15 s−1	4.5 h	Glass Fluorinated ethylene propylene	Enterococcus faecalis	Ent. faecalis was displaced by lactobacilli (31%) and streptococci (74%) from fluorinated ethylene propylene in buffer, and that displacement by lactobacilli was even more effective on glass in urine (54%). The passage of an air–liquid interface impacted adhesion, especially when the surface had been challenged with lactobacilli (up to 100%) or streptococci (up to 94%).	[138]
			Potential of biosurfactant layer to inhibit adhesion of uropathogens	Flow rate of 0.034 mL s−1, corresponding to 15 s−1	4 h	Glass Silicone rubber coated with different concentrations of a biosurfactant	Enterococcus faecalis	Biosurfactant layers inhibited the initial deposition rates (> 30%) and adhesion numbers (≈ 70–100%) in a dose-related way.For urine experiments, biosurfactant coatings caused higher adhesion reductions.	[122]
			Effect of supplementation on human urine and uropathogen adhesion	Flow rate of 0.034 mL s−1, corresponding to 15 s−1	4 h	Silicone rubber	Escherichia coli Enterococcus faecalis Staphylococcus epidermidis Pseudomonas aeruginosa Candida albicans	Cranberry and ascorbic acid supplementation can provide a degree of protection against adhesion and colonization of biomaterials by some uropathogens.	[139]
			Effect of combined surface chemistry and topography on bacterial adhesion	Flow rates of 2 and 4 mL s−1, corresponding to 0.010 and 0.024 Pa	0.5 h	Smooth polydimethylsiloxane Smooth polydimethylsiloxane with peptide coating Micropatterned polydimethylsiloxane Micropatterned polydimethylsiloxane with peptide coating	Escherichia coli	The highest adhesion was obtained on the smooth polydimethylsiloxane, whereas the micropatterned polydimethylsiloxane coated with peptide totally inhibited adhesion. The peptide addition to the smooth surface reduced the adhesion by 43–58%, while the micropatterned surface reduced the adhesion by 99%.	[21]
		Biofilm formation	Impact of temperature and surface on the biofilm-forming capacity of uropathogens	Flow rate of 4 × 10−3 mL s−1, corresponding to 33 s−1	20–24 h	Silicone Silicone coated with plasma polymerized vinylpyrrolidone	Escherichia coli	Temperature had a considerable influence upon the adhesion and biofilm-forming capacity of some of the isolates, and the influence of surface chemistry also depended on the temperature.	[140]
			Effect of applying different current densities to platinum electrodes as a possible catheter coating material	Flow rate of 3333 mL s−1, corresponding to 200 s−1	6 days	Platinum electrodes	Proteus mirabilis	By applying alternating microcurrent densities, a self-regenerative surface is produced, which removed the conditioning film and reduced bacterial adherence, growth, and survival.	[141]
		Biofilm formation and treatment	Potential of using a polymer brush on the prevention of biofilm formation and susceptibility	Flow rate of 2 mL s−1, corresponding to 15 s−1	Biofilm: 24 h Treatment: 8 h	Glass Polydimethylsiloxane Poly[oligo(ethyleneglycol) methyl ether methacrylate] brush	Escherichia coli	The polymer brush reduced the surface area and the number of total adhered cells by 57%. The antibiotic treatment potentiated cell death and removal (88%). The polymer brush has the potential to prevent biofilm growth and in eradicating biofilms developed in urinary devices.	[59]
			Effect of using a polymer brush on biofilm cell composition and architecture	Flow rate of 2 mL s−1, corresponding to 15 s−1	Biofilm: 24 h Treatment: 8 h	Glass Polydimethylsiloxane Poly[N-(2-hydroxypropyl) methacrylamide] brush	Escherichia coli	Initial adhesion and surface coverage decreased on the polymer brush. Viable but nonculturable cells were completely removed from the brush. The polymer brush may reduce biofilm growth and antibiotic resistance in urinary catheters.	[58]
96-well microplates	Biomedical scenarios	Biofilm formation	Evaluation of the combined effects of shear forces and nutrient levels on biofilm formation and definition of the operational conditions to be used to simulate relevant biomedical scenarios	Orbital shaking with 25 and 50 mm diameter incubators at 150 rpm (average shear rate of 23 and 46 s−1)	60 h	Polystyrene	Escherichia coli	Higher glucose concentrations enhanced E. coli adhesion in the first 24 h, but variations in peptone and yeast extract concentrations had no significant impact on biofilm formation. Numerical simulations indicate that 96-well microplates can be used to simulate a variety of biomedical scenarios if the operating conditions are carefully set.	[68]
Microfluidic device	General medical devices	Adhesion	Development of a fabrication method to produce a microfluidic device to test cell adhesion	0.01–1 Pa	0.5 h	Polyamide Polydimethylsiloxane Polyethylene oxide Poly(L-lactic acid) Polystyrene	Escherichia coli	Bacterial adhesion increased linearly over time. The evaluation performed with polydimethylsiloxane for shear stresses between 0.02 and 1 Pa showed that the lowered surface (inherent weakness of the fabrication method) did not influence adhesion.	[113]
			Study the initial cell adhesion dependence on local wall shear stress in a microchannel with intercalate zones of constrictions and expansions	0.2–10 Pa	0.5 h	Glass	Escherichia coli	Bacterial adhesion increased in locations with a sudden increase in shear stress.	[142]
			Examination of the role of surface properties on bacterial adhesion	0.002–0.042 Pa	n.d.	Smooth silicone Patterned silicone	Escherichia coli	Cell attachment was observed to be strongly dependent upon the topographical features. The highest attachment density was observed on smooth surfaces.	[114]
		Biofilm formation	Comparison of the biofilm-forming capacities of various Methicillin-resistant Staphylococcus aureus clones	0.05 Pa	18 h	Glass	Methicillin-resistant Staphylococcus aureus	From tested isolates, 51% successfully formed biofilms under shear flow. Differences in biofilm formation might also be due to the different adherent surfaces.	[143]
			Study of biofilm formation and host–pathogen interactions	0.05–1 Pa	24 h	Glass Eukaryotic cells (HRT-18)	Escherichia coli	Biofilm formation on glass was observed for most strains in M9 medium at 30 °C. HRT-18 cell monolayers enhanced E. coli binding and biofilm formation.	[144]
	Implanted medical device	Biofilm formation	Investigation of how environmental factors, such as surface geometry and chemistry, as well as fluid flow, affect biofilm development	0.02–1 Pa	16 h	Uncoated and human blood plasma-coated channels	Staphylococcus aureus	The flow was the major contributor to the shape of biofilm structures, whereas bacterial motility was less significant.	[115]
	Mammary environment	Biofilm formation	Evaluation of the effect of coagulase-negative staphylococci isolates with a weak- biofilm phenotype	0.05 Pa	24 h	Glass	Coagulase-negative staphylococci	Coagulase-negative staphylococci with a weak biofilm phenotype did not inhibit the growth of isolates with a strong-biofilm phenotype.	[145]
	Intravascular catheter	Biofilm formation	Investigation of flow as an environmental signal for biofilm formation	Flow rates of 1–10 mL h−1, corresponding to 0.065–1.14 Pa	24 h	Channels treated with octyl(tri-ethoxy)silane	Staphylococcus epidermidis	Fluid shear alone induced the formation of polysaccharide intracellular adhesin-positive biofilms and influenced the biofilm structure.	[116]
	Urinary devices	Adhesion	Development of microfluidic-based devices replicating the urodynamic field within different configurations of an occluded and stented ureter	Up to 0.175 Pa	1 h	Polydimethylsiloxane	Pseudomonas fluorescens	The unobstructed device showed no bacterial attachment, including in regions of low shear stress (<0.04 Pa). For the obstructed devices, the cavity region, and the nearby proximal side-hole (shear stresses of 0.131–0.175 Pa) exhibited greater levels of bacterial attachment (18%) compared to other regions of the model.	[63]

n.d.—not disclosed; D. tsuruhatensis—Delftia tsuruhatensis, Ent. faecalis—Enterococcus faecalis, E. coli—Escherichia coli, P. aeruginosa—Pseudomonas aeruginosa, P. stutzeri—Pseudomonas stutzeri, S. epidermidis—Staphylococcus epidermidis.