This study evaluated the performance of two antifouling polymer brushes - poly(MeOEGMA) and poly(HPMA) - in reducing initial adhesion of Escherichia coli under different shear stress conditions mimicking locations in the human body. Assays using a parallel plate flow chamber showed the brushes reduced E. coli adhesion by up to 90% compared to glass. Importantly, this high reduction was maintained across the tested shear stress range of 0.005-0.056 Pa, indicating the brushes did not collapse under these conditions.

1. Alves Pa*, Lopez-Mila Bb, Riedel Tb, Dittrich Bc, Rodriguez-Emmenegger Cc, Mergulhão Fa
aLEPABE - Laboratory for Process Engineering, Environment, Biotechnology and Energy, Faculty of Engineering, University of Porto, Porto, Portugal
bDepartment of Chemistry and Physics of Surfaces and Biointerfaces, Institute of Macromolecular Chemistry ASCR, v.v.i., Heyrovsky Sq. 2, 16206 Prague, Czech Republic
cDWI - Leibniz Institute for Interactive Materials and Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Forckenbeckstraße 50, 52074 Aachen, Germany
* up201510029@fe.up.pt
COSTAMiCIMeeting,7March2019,Riga,Latvia
ABSTRACT
In this work, two antifouling polymer brushes were tested at
different shear stress conditions to evaluate their performance
in reducing the initial adhesion of Escherichia coli.
Assays were performed using a parallel plate flow chamber and
a shear stress range between 0.005 and 0.056 Pa, previously
determined by numerical simulation. These shear stress values
are found in different locations in the human body where
biomedical devices are placed.
The poly(MeOEGMA) and poly(HPMA) brushes were
characterized and it was shown that they can reduce initial
adhesion up to 90% when compared to glass. Importantly, the
performance of these surfaces was not affected by the shear
stress, which is an indication that they do not collapse under this
shear stress range.
Effect of shear stress on the reduction of bacterial adhesion to
antifouling polymers
REFERENCE
Lopez-Mila, B., Alves, P., Riedel, T., Dittrich, B., Mergulhão, F., & Rodriguez-Emmenegger, C. (2018). Effect of
shear stress on the reduction of bacterial adhesion to antifouling polymers. Bioinspiration & biomimetics, 13(6),
065001.
This work was financially supported by: project UID/EQU/00511/2019 - Laboratory for Process Engineering, Environment, Biotechnology
and Energy – LEPABE funded by national funds through FCT/MCTES (PIDDAC), and project “LEPABE-2-ECO-INNOVATION” –
NORTE‐01‐0145‐FEDER‐000005, funded by Norte Portugal Regional Operational Programme (NORTE 2020), under PORTUGAL 2020
Partnership Agreement, through the European Regional Development Fund (ERDF). The research was funded by the Deutsche
Forschungsgemeinschaft (DFG, German Research Foundation) via Schwerpunktprogramm “Auf dem Weg zur implantierbaren Lunge”
(SPP 2014). PA acknowledges the receipt of a Ph.D. Grant from the Portuguese Foundation from Science and Technology (FCT)
(PD/BD/114317/2016). Support from the EU COST Actions iPROMEDAI (TD1305), ENBA (CA15216) and AMiCI (CA15114) is
acknowledged.
ACKNOWLEDGMENTS:
CONCLUSIONS
✓ The polymer brushes can reduce bacterial adhesion over a relevant range of
shear stresses that can be found in several locations of our body.
✓ The extent of the reduction in initial adhesion suggests that these surfaces can
potentially be used in the development of biomedical devices with increased
antifouling performance.
RESULTS
MATERIALS AND METHODS
E. coli JM109(DE3)
Glycerol stock
Culture medium
Inoculation overnight at 37 ºC with orbital agitation
(160 rpm)
a. Harvest cells by centrifugation at
3202 g;
b. Suspend the cells in citrate buffer
(CB) to obtain 7.6 x 107 cells.mL-1.
2 Bacteria & Culture conditions
*different shear stresses to match the hydrodynamic conditions existing in
several locations in the human body (range between 0.005 and 0.056 Pa).
Time
30 min
Analysis
Real-time monitoring
Image analysis
ImageJ software
Adhesion analysis4
Surfaces & Physical characterization1
poly(HPMA) poly(MeOEGMA)
glassglass
Contact angle
measurements
Free energy of
adhesion
Flow system
Centrifugal
pumps
Valve*
Flow cell
Microscope
Bacterial
suspension in CB
37 ºC
3
Table I. The hydrophobicity (∆𝐺 𝑇𝑂𝑇) of surfaces tested, bacteria and the energy of adhesion (∆𝐺 𝐴𝑑ℎ).
Surfaces ∆𝑮 𝑻𝑶𝑻 (mJ.m-2) ∆𝑮 𝑨𝒅𝒉(mJ.m-2)
glass 35.6 73.0
poly(HPMA) 45.5 80.0
poly(MeOEGMA) 6.3 58.5
Escherichia coli JM109(DE3) 121.9 n/a
Figure 1. Adhesion of E. coli on glass (■), poly(HPMA) (●) and poly(MeOEGMA) (▲) brushes, at different flow rates: 1 mL·s−1, 2 mL·s−1,
4 mL·s−1, 6 mL·s−1 and 8 mL·s−1.
Figure 2. Average reduction in E. coli adhesion on poly(HPMA) ( ) and poly(MeOEGMA) brushes (▼) relative to glass (used as control)
for the different flow rates and average wall shear stress determined by computational fluid dynamics (●).
4 mL·s-1
1 mL·s-1
2 mL·s-1
6 mL·s-1
8 mL·s-1
Time (min)
Time (min) Time (min)
Time (min)Time (min)
1
2
The brushes displayed a similar
behavior despite the differences in
their chemical composition and
surface energy.
poly(HPMA)
poly(MeOEMA)
glass
The reduced adhesion with increasing
flow rate suggests that bacteria interact
weakly with the brushes and can be
removed by shear.
A clear correlation between surface
hydrophobicity or the calculated energy
of adhesion and bacterial adhesion could
not be found.
All the surfaces tested are
hydrophilic, as ∆𝐺 𝑇𝑂𝑇> 0.
Remarkably, brushes of
poly(HPMA) were more
hydrophilic (higher ∆𝐺 𝑇𝑂𝑇 )
than poly(MeOEGMA).
The polymer brushes can reduce
initial adhesion up to 90% when
compared to glass.
Depositcells(103cells·cm-2)
Depositcells(103cells·cm-2)Depositcells(103cells·cm-2)
Depositcells(103cells·cm-2)Depositcells(103cells·cm-2)
▪ The polymer brushes were directly grafted from a self-assembled
monolayer via surface-initiated atom transfer radical
polymerization (SI-ATRP):
Thickness ~30nm