Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 10, Issue 3, Pages 2275-2281Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.7b12145
Keywords
antifouling atomic force microscopy; hydrogel; poly(ethylene glycol); Escherichia coli; Staphylococcus aureus
Funding
- National Research Service Award from the National Institutes of Health [T32 GM008515]
- Professor James M. Douglas Career Development Faculty Award
- Armstrong Fund for Science
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [T32GM008515] Funding Source: NIH RePORTER
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Despite lacking visual, auditory, and olfactory, perception, bacteria sense and attach to surfaces. Many factors, including the chemistry, topography, and, mechanical properties of a surface, are known to alter bacterial attachment, and in this study, using a library of nine protein-resistant poly(ethylene glycol) (PEG) hydrogels immobilized on glass slides, we demonstrate that the thickness: or amount of polymer concentration also matters. Hydrated atomic force microscopy and rheological measurements corroborated that thin (15 mu m), medium (40 mu m), and thick (150 mu m) PEG hydrogels possessed Young's moduli in three distinct regimes, soft (20 kPa), intermediate (300 kPa), and stiff (1000 kPa). The attachment of two diverse bacteria, flagellated Gram-negative Escherichia coli and nonmotile Gram-positive Staphylococcus aureus was assessed after a 24 h incubation on the nine PEG hydrogels. On the thickest PEG hydrogels (150 mu m), E. coli and S. aureus attachment increased with increasing hydrogel stiffness. However, when the hydrogel's thickness was reduced to 15 mu m, a substantially greater adhesion of E. coli and S. aureus was observed. Twelve times fewer S. aureus and eight times fewer E. coli adhered to thin -soft hydrogels than;to thick-soft,hydrogels. Although a full mechanism to explain this behavior is beyond the scope of this article, we suggest that because the Young's moduli of thin -soft and thick -soft hydrogels were statistically equivalent, potentially, the very stiff underlying glass slide was causing the thin -soft hydrogels to feel stiffer to the bacteria. These findings suggest a key takeaway design rule; to optimize fouling-resistance, hydrogel coatings should be thick and soft.
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