Lignin-Based Infection-Resistant Biomaterials

  • Zili Ji

Student thesis: Masters ThesisMaster of Philosophy


This research is an initial attempt to incorporate lignin as a leaching antibacterial substance within biomedical materials to reduce device-associated infections. Lignin-loaded poly(2-hydroxyethyl methacrylate)-co-poly(methacrylic acid) hydrogels were synthesised, while tetracycline hydrochloride (TET) was also loaded into the polymers for comparison. Synthesised hydrogels were validated with suitable drug releasing and loading abilities, desirable pH-sensitive characteristics as well as surface properties, and improved thermal stabilities.

After verifying the antimicrobial abilities of lignin, materials have been tested under both normal and infected urine conditions against urinary pathogens S. aureus (Gram-positive) and P. mirabilis (Gram-negative) to investigate their ability to reduce catheter associated urinary tract infections. Lignin-loaded copolymers demonstrated similar antibacterial properties to TET-loaded copolymers by significantly decreasing relative bacterial adherence and reducing the planktonic cell density to below the LOD when incubated with S. aureus. Lignin-loaded hydrogels were more effective in inhibiting the growth of S. aureus compared to P. mirabilis in adherence tests, while lignin-loaded copolymers showed mixed results after incubation with P. mirabilis. Generated results of microbiological studies revealed the potential of lignin-loaded polymers for use as urinary catheter coating materials due to their anti-bacterial properties.

Lignin-loaded hydrogels have shown intrinsic desirable characteristics, antibacterial properties, and great potential to be considered as promising candidates for use as anti-infective coating materials with limited possibility of leading to bacterial resistance.
Date of AwardDec 2022
Original languageEnglish
Awarding Institution
  • Queen's University Belfast
SupervisorEneko Larrañeta (Supervisor), Louise Carson (Supervisor), Colin McCoy (Supervisor) & Nicola Irwin (Supervisor)


  • Antimicrobial polymers
  • lignin

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