The University of Massachusetts Amherst
University of Massachusetts Amherst

Search Google Appliance


GRASS - Graduate Student Seminar: Brandon Barajas (Schiffman Group)

(Connor Giles talk will be held at a later date)


Tuesday, October 4, 2022 - 11:30am


LGRT 201 & via Zoom (email for a link)


Brandon Barajas – Jessica Schiffman Research Group

Establishing the Mechanoselective Adhesion of Microorganisms to Biomaterials

The use of polymer-based medical devices, such as urinary tract catheters, has reduced material costs, improved quality of care, and increased device biocompatibility compared to metal-based devices. However, these polymer surfaces are susceptible to becoming surfaces on which a biofilm can develop. As their usage increases, more patients are at risk of developing fatal hospital-acquired infections that result from bacterial buildup on the polymer biomaterial. The overreliance on antibiotics to treat these infections has accelerated the development of antibiotic-resistant bacterial strains. Thus, we suggest the need to shift strategies towards infection prevention that focuses on decreasing the initial adhesion of bacteria to the polymer surface. Previous research suggests that the mechanics of a material, including stiffness, impact the adhesion of bacteria to polymeric materials. Work from the Schiffman group has shown that Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus demonstrated greater adhesion on stiff, hydrophilic poly(ethylene glycol) dimethacrylate (PEGDMA) and agar hydrogels. To decouple the role the hydrophilicity has on the adhesive behavior of the microorganisms, we next studied their attachment to hydrophobic polydimethylsiloxane (PDMS) gels with varying material properties. PDMS gels have been systematically synthesized by varying the ratio of base to curing agent during synthesis. The mechanical properties of these gels were characterized using rheology and we classified the gels made from a ratio of 5:1 base to curing agent as stiff, 10:1 gels as standard, and 40:1 gels as soft. Bacterial attachment to these gels was assessed using fluorescence microscopy after a 24 hour incubation period. Unlike previously displayed trends on PEGDMA hydrogels, my results demonstrated that both uropathogenic E. coli and S. aureus strains exhibit greater adhesive behavior on softer PDMS gels. Our next goal was to gain biological insights into which genes are involved in the process of adhesion. Collaborations with the Andrews group and their CRISPRi systems for gene repression have shown initial promise in successfully reducing bacterial adhesion associated to certain genetic targets and can be used on a genome wide scale to further identify other important biological components of bacterial adhesion.



Follow UMass Chemical Engineering: