An official website of the United States government
Mitigating the attachment of microorganisms to polymer biomaterials is critical for preventing hospital-acquired infections. Two chemical strategies to mitigate fouling include fabricating fouling-resistant surfaces, which typically present hydrophilic polymers, such as polyethylene glycol (PEG), or creating fouling-release surfaces, which are generally hydrophobic featuring polydimethylsiloxane (PDMS). Despite the demonstrated promise of employing PEG or PDMS, amphiphilic PEG/PDMS copolymer materials remain understudied. Here, for the first time, we investigated if phase-separated amphiphilic copolymers confounded microbial adhesion. We used bottlebrush amphiphilic PEG/PDMS co-networks and homopolymer networks to study bacterial adhesion across a library of gels (ϕPEG = 0.00, 0.21, 0.40, 0.55, 0.80, and 1.00). Hydrated atomic force microscopy measurements revealed that most of the gels had low surface roughness, less than 5 nm, and an elastic modulus of ∼80 kPa. Interestingly, the surface roughness and elastic modulus of the ϕPEG = 0.40 gel were twice as high as those of the other gels due to the presence of crystalline domains, as confirmed using polarized optical microscopy on the hydrated gel. The interactions of these six well-characterized gels with bacteria were determined using Escherichia coli K12 MG1655 and Staphylococcus aureus SH1000. The attachment of both microbes decreased by at least 60% on all polymer gels versus the glass controls. S. aureus adhesion peaked on the ϕPEG = 0.40, likely due to its increased elastic modulus, consistent with previous literature demonstrating that modulus impacts microbial adhesion. These findings suggest that hydrophilic, hydrophobic, and amphiphilic biomaterials effectively resist the early attachment of Gram-negative and Gram-positive microorganisms, providing guidance for the design of next-generation antifouling surfaces.
more »
« less
Depletion forces drive reversible capture of live bacteria on non-adhesive surfaces
Because bacterial adhesion to surfaces is associated with infections and biofilm growth, it has been a longstanding goal to develop coatings that minimize biomolecular adsorption and eliminate bacteria adhesion. We demonstrate that, even on carefully-engineered non-bioadhesive coatings such as polyethylene glycol (PEG) layers that prevent biomolecule adsorption and cell adhesion, depletion interactions from non-adsorbing polymer in solution (such as 10 K PEG or 100 K PEO) can cause adhesion and retention of Escherichia coli cells, defeating the antifouling functionality of the coating. The cells are immobilized and remain viable on the timescale of the study, at least up to 45 minutes. When the polymer solution is replaced by buffer, cells rapidly escape from the surface, consistent with expectations for the reversibility of depletion attractions. The dissolved polymer additionally causes cells to aggregate in solution and aggregates rapidly dissociate to singlets upon tenfold dilution in buffer, also consistent with depletion. Hydrodynamic forces can substantially reduce the adhesion of aggregates on surfaces in conditions where single cells adhere via depletion. The findings reported here suggest that because bacteria thrive in polymer-rich environments both in vivo and in situ , depletion interactions may make it impossible to avoid bacterial retention on surfaces.
more »
« less
- Award ID(s):
- 1848065
- PAR ID:
- 10295075
- Date Published:
- Journal Name:
- Soft Matter
- Volume:
- 17
- Issue:
- 35
- ISSN:
- 1744-683X
- Page Range / eLocation ID:
- 8185 to 8194
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Bacteria can proliferate orthopedic implants, resulting in infection rates as high as 5%. A consistent problem across implantology is the development of surfaces which successfully promote the adhesion and propagation of healthy fibroblast and osteoblast cells while deterring formation of bacterial biofilms. Selecting surface configurations which favor cell adhesion will lead to decreased infection rates. Progress in identifying appropriate surface configurations is hindered by the lack of quantitative adhesion techniques capable of comparing adhesion of cells and biofilms directly. Recent advancements in adhesion techniques have allowed for quantitatively measured adhesion strengths of both bacterial biofilms and cell monolayers using the laser spallation technique. The quantified stress-based adhesion values allow surface and environmental factors that modulate both bacterial and cell adhesion to implant surfaces to be evaluated. During implantation, blood propagates wound sites completely coating implant surfaces. Quantitatively determining the impact of preconditioning layers that accumulate on the implant surface on cell adhesion is vital to predict implant behavior. Previous work has demonstrated that these preconditioning layers either negatively or neutrally impact bacterial adhesion to titanium implant surfaces. This study focuses on the impact that blood plasma and fibronectin coatings have on the adhesion of osteoblastic (MG 63) cells and fibroblasts to the same titanium surfaces. Adhesion results indicate that preconditioning layers and increased surface roughness positively impact cell adhesion. Incorporating the increased adhesion values for cell adhesion into the Adhesion Index demonstrates that increased surface roughness, coupled with natural wound healing preconditioning of surfaces, yields positive biocompatibility.more » « less
-
Adhesion of colloids and bacteria to various surfaces is important for a variety of environmental phenomena including microbial biofouling and contamination prevention. Under saturated conditions, both colloids and bacteria have the opportunity to attach to porous medium surfaces. Under water unsaturated conditions or in the presence of the air-water interface, besides the porous medium surfaces, colloids and bacteria can also attach to the air-water interface, including the air-water-solid threephase interface. The magnitudes of adhesion of colloids and bacteria are correlated to the interactions of the colloids and bacteria with the surfaces, which are a function of their surface physicochemical properties. In this review, adhesion theories are revisited and adhesion of colloids and bacteria to porous media and the air-water interface is discussed. The interaction forces are quantified using various theoretical models including the DLVO models and used to interpret related adhesion. The impact of surfactants on colloid and bacterial adhesion is also discussed. The review also includes the implementation of the adhesion theory in interpreting colloid and bacterial fate and transport in the subsurface soil.more » « less
-
Abstract Slippery surfaces (i.e., surfaces that display high liquid droplet mobility) are receiving significant attention due to their biofluidic applications. Non‐textured, all‐solid, slippery hydrophilic (SLIC) surfaces are an emerging class of rare and counter‐intuitive surfaces. In this work, the interactions of blood and bacteria with SLIC surfaces are investigated. The SLIC surfaces demonstrate significantly lower platelet and leukocyte adhesion (≈97.2% decrease in surface coverage), and correspondingly low platelet activation, as well as significantly lower bacterial adhesion (≈99.7% decrease in surface coverage of liveEscherichia Coliand ≈99.6% decrease in surface coverage of liveStaphylococcus Aureus) and proliferation compared to untreated silicon substrates, indicating their potential for practical biomedical applications. The study envisions that the SLIC surfaces will pave the path to improved biomedical devices with favorable blood and bacteria interactions.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1sm00631b
