Lysine grafted poly(lactic acid): An intrinsically antimicrobial polymer

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Infectious Disease Research

Background:

• Healthcare-associated infections are a significant problem, often stemming from contaminated medical devices.
• Conventional plastics like poly(lactic acid) (PLA) lack inherent antimicrobial properties, necessitating material innovation.
• Developing effective antimicrobial surfaces is crucial for enhancing patient safety in healthcare settings.

Purpose of the Study:

• To impart antimicrobial activity to poly(lactic acid) (PLA) for biomedical applications.
• To chemically modify PLA by maleation and subsequent l-lysine grafting.
• To evaluate the antimicrobial efficacy, cytotoxicity, and mechanical properties of the modified PLA.

Main Methods:

• Poly(lactic acid) was modified through maleation followed by l-lysine grafting.
• Chemical structure modifications were verified using Fourier-transform infrared (FTIR) spectroscopy and proton nuclear magnetic resonance (¹H NMR) analysis.
• Antimicrobial activity was assessed against *Escherichia coli* and *Staphylococcus aureus*, and cytotoxicity was evaluated using L929 mouse cells.

Main Results:

• Chemical modifications were successfully confirmed, indicating successful l-lysine grafting onto PLA.
• The modified PLA exhibited significant antimicrobial activity, inhibiting approximately 99% of *Staphylococcus aureus* growth upon contact.
• Cytotoxicity tests using L929 mouse cells showed no adverse effects, confirming the material's safety for eukaryotic cells.
• Thermal analysis and tensile tests demonstrated improved processability and maintained mechanical properties of the modified PLA (PLA-g-Lys).

Conclusions:

• The novel PLA derivative (PLA-g-Lys) possesses potent antimicrobial properties against *Staphylococcus aureus* without compromising biocompatibility.
• The modified PLA shows promise for manufacturing biomedical devices with reduced risk of healthcare-associated infections.
• This material represents a significant advancement in developing safer and more effective medical device components.