Improvement of the Antimicrobial Activity of Oregano Oil by Encapsulation in Chitosan—Alginate Nanoparticles

Abstract

Oregano oil (OrO) possesses well-pronounced antimicrobial properties but its application is limited due to low water solubility and possible instability. The aim of this study was to evaluate the possibility to incorporate OrO in an aqueous dispersion of chitosan—alginate nanoparticles and how this will affect its antimicrobial activity. The encapsulation of OrO was performed by emulsification and consequent electrostatic gelation of both polysaccharides. OrO-loaded nanoparticles (OrO-NP) have small size (320 nm) and negative charge (−25 mV). The data from FTIR spectroscopy and XRD analyses reveal successful encapsulation of the oil into the nanoparticles. The results of thermogravimetry suggest improved thermal stability of the encapsulated oil. The minimal inhibitory concentrations of OrO-NP determined on a panel of Gram-positive and Gram-negative pathogens (ISO 20776-1:2006) are 4–32-fold lower than those of OrO. OrO-NP inhibit the respiratory activity of the bacteria (MTT assay) to a lower extent than OrO; however, the minimal bactericidal concentrations still remain significantly lower. OrO-NP exhibit significantly lower in vitro cytotoxicity than pure OrO on the HaCaT cell line as determined by ISO 10993-5:2009. The irritation test (ISO 10993-10) shows no signs of irritation or edema on the application site. In conclusion, the nanodelivery system of oregano oil possesses strong antimicrobial activity and is promising for development of food additives.

Applications of Chitosan-Alginate-Based Nanoparticles—An Up-to-Date Review

“…Other preparation techniques include, but are not limited to, sonication [69,70], electrospraying [71], electrostatic gelation [72][73][74], extrusion of polymer dispersions [75], selfassembly of polysaccharides [65], and microfluidic methods [76,77].…”

“…For instance, Yoncheva et al [74] have incorporated oregano oil into chitosan-alginate NPs and tested them against eight microbial strains. These small-sized (320 nm) and negatively charged (−25 mV) particles have shown promising results against Gram-positive and Gram-negative bacteria, while in vitro cytotoxicity tests on human keratinocytes and in vivo skin irritation tests proved the safety profile of these nanosystems.…”

“…Another example is offered by Yoncheva et al [74], who have designed chitosanalginate nanoparticles encapsulated with oregano oil. The scientists reported a considerably enhanced antimetabolic activity than for the pure oil in several strains, recommending this nanoformulation as a food additive with antimicrobial activity.…”

Application of chitosan/alginate nanoparticle in oral drug delivery systems: prospects and challenges

“…Ionic gel method for CANPs has many advantages, such as the protocol are simple and fast, and easy to reach high encapsulation rate. Nevertheless, this method does not allow for a narrow particle size distribution, which will indirectly affect the drug loading capacity (Li et al., 2019 ).There are also other methods for CANPs preparation, including emulsification (Mao et al., 2016 ; Kyzioł et al., 2017 ; Khorshidian et al., 2019 ; Yue et al., 2020 ), electrostatic gelation (Aluani et al., 2017 ; Yoncheva et al., 2021 ), extrusion coagulation (ALQuadeib et al., 2020 ), co-precipitation (Yu et al., 2019 ), etcs. These methods are more complex than ionic gel method, while the control of particle size and distribution are more rigorous.…”

Immobilization Systems of Antimicrobial Peptide Ib−M1 in Polymeric Nanoparticles Based on Alginate and Chitosan

“…Additionally, they have reactive functional groups that allow for the conjugation of peptides and proteins. [ 5 , 6 , 7 , 8 , 9 , 10 ].…”