Antibacterial Effect of Thymol Loaded SBA-15 Nanorods Incorporated in PCL Electrospun Fibers.

Enrique Gámez,Silvia Irusta,Gracia Mendoza,Manuel Arruebo,Sara García-Salinas,Jorge Tascon,Nuria Navascues,Hellen Elizondo-Castillo

doi:10.3390/nano10040616

Abstract

For the effective management of infected chronic wounds, the incorporation of antimicrobial drugs into wound dressings can increase their local availability at the infection site. Mesoporous silicon dioxide SBA-15 is an excellent drug carrier with tunable drug release kinetics. In this work, synthesized SBA-15 loaded with the natural antimicrobial compound thymol (THY) was incorporated into polycaprolactone (PCL) electrospun nanofibers to obtain an advanced wound dressing. Rod-shaped particles with internal parallel channels oriented along the longitudinal axis (diameter: 138 ± 30 nm, length: 563 ± 100 nm) were loaded with 70.8 wt.% of THY. Fiber mats were prepared using these particles as nanofillers within polycaprolactone (PCL) electrospun fibers. The resulting mats contained 5.6 wt.% of THY and more than half of this loading was released in the first 7 h. This release would prevent an initial bacterial colonization and also inhibit or eliminate bacterial growth as in vitro shown against Staphylococcus aureus ATCC 25923. Minimal inhibitory concentration (MIC: 0.07 mg/mL) and minimal bactericidal concentration (MBC: 0.11 mg/mL) of released THY were lower than the amount of free THY required, demonstrating the benefit of drug encapsulation for a more efficient bactericidal capacity due to the direct contact between mats and bacteria.

Highlights

An ideal wound dressing should protect the wound from physical damage/mechanical tear, provide adequate gaseous and nutrient exchange, and absorb the excess of wound exudates [1]
Synthesized SBA-15 rods with mean diameter of 138 ± 30 nm and mean length of 563 ± 100 nm were loaded with 70.79 ± 5.21 wt.% of THY
The essential oil compound was located inside the silica porous structure according to XRD and nitrogen adsorption results but mostly on the interparticle spaces

Summary

Introduction

An ideal wound dressing should protect the wound from physical damage/mechanical tear, provide adequate gaseous and nutrient exchange, and absorb the excess of wound exudates [1]. The local delivery of antimicrobials can decrease the possibility of emergence of bacterial resistance, since several mutations are required to acquire resistance, and a homogeneous drug concentration hinders multiple mutation selection [5]. For the effective management of infected chronic wounds, a promising approach is the incorporation of antimicrobial drugs into a carrier that assures its availability at the site of the infection for long periods of time without having cytotoxicity against somatic cells. Mesoporous materials such as MCM-41, SBA-15 and MOF have been extensively used as drug carriers because of their exceptional and tailored sorption properties and sustained drug release ability [7]. Two-dimensional hexagonal structured SBA-15, one of the most important types of mesoporous silicas, has large pore sizes (5–30 nm), an ordered structure, and surface silanol groups that can facilitate intermolecular hydrogen bonding with different drugs promoting their bioavailability, which is especially important for highly hydrophobic drugs; in addition, pore-mouth functionalization can avoid a premature drug release by means of molecular gates [10]

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