# Liposomal Encapsulation Reduces the Cytotoxic Effects of Gramicidin S in Monolayer and Spheroid Fibroblast Cultures

## TL;DR

Liposomal encapsulation reduces the harmful effects of gramicidin S on fibroblast cells in both 2D and 3D cultures.

## Contribution

This study demonstrates that liposomal encapsulation significantly mitigates gramicidin S cytotoxicity and validates 3D spheroids as a better toxicity model.

## Key findings

- Liposomal GS preserved 80.3–82.2% cell viability at 75 µg/mL, compared to 0.5% with free GS.
- Spheroid cultures showed higher resistance to GS toxicity, with liposomal GS preserving viability above 84.8%.
- Liposomal encapsulation likely reduces toxicity by limiting direct membrane disruption.

## Abstract

Background/Objectives: Gramicidin S (GS) is a cyclic antimicrobial peptide with strong antibacterial activity but significant cytotoxicity toward mammalian cells. This study evaluated GS-induced cytotoxicity in L929 fibroblast cells using both traditional 2D monolayer cultures and more physiologically relevant 3D spheroid models, and assessed whether liposomal encapsulation could mitigate toxicity and improve biocompatibility. Methods: L929 cells were cultured in monolayers and spheroids and treated with free GS or GS encapsulated in liposomes of varying lipid compositions. Cell viability and morphology were evaluated after 24 h of exposure using standard cytotoxicity assays. Results: Control liposomes, regardless of tested lipid type or concentration, showed no adverse effects on cell morphology or viability. Free GS caused pronounced, dose-dependent cytotoxicity in monolayers, decreasing viability to 11.0 ± 1.9% and 0.5 ± 1.1% at 50 and 75 µg/mL, respectively. By contrast, encapsulation in liposomes significantly reduced toxicity (p < 0.05), preserving 80.3–82.2% viability at 75 µg/mL depending on formulation, corresponding to protection factors exceeding 160-fold (80.3% vs. 0.5%). Spheroid cultures showed slightly higher resistance to GS; free GS reduced viability to 2.9%, while liposomal GS preserved it above 84.8%, depending on lipid composition. Conclusions: Liposomal encapsulation effectively reduces GS-induced cytotoxicity, likely by limiting direct membrane disruption. Moreover, spheroid models provide a more physiologically relevant and predictive platform for toxicity testing, while the results support nanoliposomes as a practical delivery strategy to enhance the safety of antimicrobial peptides during preclinical development.