Water Soluble Usnic Acid-Polyacrylamide Complexes with Enhanced Antimicrobial Activity against Staphylococcus epidermidis

Iolanda Francolini,Antonella Piozzi,Lucio D'Ilario,Vincenzo Taresco,Andrea Martinelli,Fernanda Crisante

doi:10.3390/ijms14047356

Iolanda Francolini, Antonella Piozzi + Show 4 more

Open Access

https://doi.org/10.3390/ijms14047356

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Abstract

Usnic acid, a potent antimicrobial and anticancer agent, poorly soluble in water, was complexed to novel antimicrobial polyacrylamides by establishment of strong acidic-base interactions. Thermal and spectroscopic analysis evidenced a molecular dispersion of the drug in the polymers and a complete drug/polymer miscibility for all the tested compositions. The polymer/drug complexes promptly dissolved in water and possessed a greater antimicrobial activity against Staphylococcus epidermidis than both the free drug and the polymer alone. The best results were obtained with the complex based on the lowest molecular weight polymer and containing a low drug content. Such a complex showed a larger inhibition zone of bacterial growth and a lower minimum inhibitory concentration (MIC) with respect to usnic acid alone. This improved killing effect is presumably due to the reduced size of the complexes that allows an efficient cellular uptake of the antimicrobial complexes. The killing effect extent seems to be not significantly dependent on usnic acid content in the samples.

Highlights

Drug oral bioavailability can be reduced by several physiological factors, such as metabolic degradation prior to absorption, poor absorption from gastrointestinal tract or first-pass metabolism [1]
Usnic acid was recently shown to be able to prevent biofilm formation by Staphylococcus spp. when incorporated in polyurethanes [6,7] or in bone cements [8]. This drug is under investigation for the prevention of medical device-related infections as an antimicrobial agent to be adsorbed on the surface of medical devices as an alternative to conventional antibiotics [9]
Antimicrobial polymers offer the promise for enhancing the efficacy of existing antimicrobial agents by increasing their efficiency and selectivity [24]

Summary

Introduction

Drug oral bioavailability can be reduced by several physiological factors, such as metabolic degradation prior to absorption, poor absorption from gastrointestinal tract or first-pass metabolism [1]. One of the most extensively studied lichen derivates, is known to possess several interesting biological properties [2] It has a good antimicrobial activity against planktonic. Usnic acid was recently shown to be able to prevent biofilm formation by Staphylococcus spp. when incorporated in polyurethanes [6,7] or in bone cements [8]. This drug is under investigation for the prevention of medical device-related infections as an antimicrobial agent to be adsorbed on the surface of medical devices as an alternative to conventional antibiotics [9]

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