Application of a Self-Disinfecting Surface for Hemodialysis

  • Katie Christensen |
  • Sierra Flores |
  • Ivy Hansen |
  • Cody Paraso |
  • Andrea Peterson |
  • Dr. David Britt |
  • Dr. Luis Bastarrachea |
  • Mike Henrie

Background

The Biological Engineering Department at Utah State University (USU) is collaborating with Fresenius Medical Care (FMC) to develop a novel method of bacterial reduction for hemodialysis systems.

In the United States, approximately 34% of reported hemodialysis hospitalizations have been due to infections [1]. The water inlet line was identified as an area with potential to introduce bacteria into the system.

Figure 1. Hemodialysis system schematic. The water inlet for fresh dialysate formation is where a self-disinfecting surface may be beneficial to patient health and decrease system bacterial load.

Research Goals and Significance

The purpose of this research is to decrease the bacterial load in a hemodialysis system by placing self-disinfecting polyethylenimine (PEI)-coated microbeads in the system’s water inlet line.

  • Optimize disinfecting performance of coated microbeads
  • Investigate the potential of PEI leaching
  • Analyze the economic feasibility of implementation
  • Investigate if microbeads negatively affect system performance
  • Investigate biocompatibility

Methodlogy and Results

optimize disinfecting performance of coated microbeads

Antimicrobial Activity
Antimicrobial activity was assessed using a common gram-negative contaminant, Pseudomonas aeruginosa, and a small-size standard test strain, Brevundimonas diminuta [3]. Cells were grown in nutrient broth, washed with sterile water, and suspended in 0.05 g/L, 0.1 g/L, and 0.15 g/L liquid PEI solutions.

Figure 2. Resultant growth of bacterial cells exposed to PEI. Horizontal lines indicate target 3-log reduction for each strain.

PEI Leaching
A bicinchoninic acid (BCA) assay was used to measure absorbance values of PEI solutions being run through the Diasafe filter. Resulting absorbance values indicate the filter reduced PEI concentrations of 100 to 500 mg/L by 46.4% to 72.4%.

Investigate the potential of PEI leaching

Microbeads
Microbeads were purchased commercially and characterized by analyzing average diameter and surface charge using DLS and Zeta Potential. Dynabeads were exposed to PEI, centrifuged, resuspended, and the resulting surface charge was determined (Table 1).

Table 1. Average diameter and surface charge of commercial microbeads before and after addition of PEI [4]. Zeta potential was taken at a pH between 5.1 and 5.4.

Conclusions

  • PEI achieved 3-log (99.9%) reduction of bacteria at concentrations between 0.05 and 0.15 g/L and can therefore be considered an effective antimicrobial agent in solution
  • PEI was successfully bound to Dynabeads
  • The Diasafe filter was successful in reducing a portion of the PEI passing through in solution

Ongoing and Future Work

  • Test bacterial reduction by PEI-coated microbeads
  • Assess whether immobilization of PEI on beads eliminates PEI crossing the Diasafe filter
  • Determine mass of beads and PEI needed for 3-log bacterial reduction in a hemodialysis system
  • Investigate if microbeads negatively affect system performance
  • Investigate biocompatibility