Graphene-coated surface plasmon resonance interfaces for studying the interactions between bacteria and surfaces

Current research on bacterial adhesion often focuses on surface interactions and adhesin specificity. Prior studies have identified that fimbriae and adhesins are key in targeting host glycan structures. However, the electrostatic and chemical interplay during adhesion remains poorly understood. Established methods for studying adhesion include atomic force microscopy and flow cytometry. These approaches, while informative, lack the specificity for real-time monitoring of surface interactions. This gap motivated the development of SPR interfaces modified with graphene oxide. The need for a system that can track adhesion strength in real-time led to the use of electrophoretic deposition techniques. No prior work had resolved the dynamic range of adhesion across multiple bacterial strains. This gap motivated the design of a simplified SPR platform with tunable surface chemistries.

The study aimed to develop a simplified SPR platform to measure adhesion strength of diverse E. coli strains. The motivation arose from the need to understand how different adhesins interact with modified surfaces. The researchers focused on three clinical isolates with distinct adhesin structures. Each isolate was selected based on its known fimbrial adhesin expression. The goal was to correlate adhesin specificity with surface modification chemistry. The SPR platform was designed to allow real-time monitoring of adhesion events. The study also aimed to test whether surface modifications could mimic host cell interactions. This approach could help in understanding pathogenic adhesion mechanisms.

The researchers used electrophoretic deposition to coat gold SPR interfaces with reduced graphene oxide. The rGO films were then modified with PEI, PSS, mannose, and lactose. Surface modifications were achieved through π-stacking and electrostatic interactions. Each modification was applied via immersion in aqueous solutions. The SPR setup enabled real-time tracking of bacterial adhesion dynamics. Three E. coli isolates were tested: UTI89, att25, and 107/86. Each isolate expresses a different fimbrial adhesin. The adhesion strength was measured across a wide concentration range.

The UTI89 isolate showed strongest adhesion to PEI- and mannose-modified surfaces. This strain expresses the FimH adhesin, which binds to mannose. The att25 isolate disintegrated lactose-modified surfaces. This strain's F17a-G adhesin targets N-acetylglucosamine. The 107/86 isolate interacted strongly with PSS-modified rGO. This adhesin, FedF, binds to ABH blood group antigens. The SPR response was linear between 1 × 10² and 1 × 10⁹ cfu/mL. These results suggest that surface chemistry influences adhesion strength. The SPR platform successfully differentiated between adhesin-specific interactions.

The SPR platform demonstrated that surface modifications can influence bacterial adhesion. The results suggest that adhesin specificity correlates with surface chemistry. PEI and mannose surfaces attracted UTI89, while lactose surfaces repelled att25. The PSS-modified surface strongly interacted with 107/86. These findings align with the known adhesin structures of each isolate. The linear SPR response indicates reliable detection across a wide concentration range. The study supports the use of SPR for real-time adhesion monitoring. The platform may help in understanding host-pathogen interactions at surfaces.