Abstract
BackgroundLiposomes have the ability to enclose hydrophilic or lipophilic materials. Bioactive macromolecules become more stable when they are entrapped within liposomes resisting environmental changes, allowing maintenance of the antimicrobial molecules and increasing their effectiveness and constancy thus can be used for food preservation. The aim of this study was to screen food samples for microbial contamination and to examine the antimicrobial activity of selected six ready-made plant oils which were; clove, black seed, thyme, garlic, rosemary and green tea against the isolated microbes from food samples and other selected microbes. Also to examine the possible enhancement of the antibacterial property of clove oil and tetracycline versus Escherichia coli when they were encapsulated into distearoyl phosphatidylcholine (DSPC) liposomes as a nanoscale carriers. Results of the antimicrobial action measured by minimum inhibitory concentration revealed that all six oils had antimicrobial action when facing at least one of the tested microbes. However only clove oil could inhibit the growth of all tested microbes. Moreover encapsulation of clove oil into DSPC liposomes enhanced its antibacterial action by 10 times when examined to inhibit the growth of E. coli. Also the antibacterial activity of liposome encapsulated tetracycline was improved by 8 times. Results of characterization of formulated clove oil liposomes by measuring their Zeta potential and their sizes implying that clove oil might be enclosed within the hydrophobic portion of the two layers of the liposome. Analyzing data of Fourier Transform Infrared Spectroscopy showed that clove oil was detected in the interfacial area of the liposome. Analyzing results of Differential scanning calorimetry and measuring phase transitions suggested that liposomes encapsulating clove oil had a membrane fluidization effect.ConclusionSome plant oils like clove has antimicrobial activity which enhanced with liposomal encapsulation and thus reduces the needed concentration to give the desired actions.
Highlights
Liposomes have the ability to enclose hydrophilic or lipophilic materials
In the present study screening of 45 different food samples for microbial contamination revealed the presence of 17 E. coli isolates, 5 Salmonella isolates and one C. albicans isolate
In the present study clove loaded liposomes had higher negative zeta potential (− 117.5 ± 85.2 mV) which may be explained by the presence of hydroxyl (OH−) group on the clove surface liposomes that might be physically associated by the surface without upsetting the packing membrane suggesting that clove oil might be caught in the hydrophobic fraction of the liposomal bilayer
Summary
Bioactive macromolecules become more stable when they are entrapped within liposomes resisting environmental changes, allowing main‐ tenance of the antimicrobial molecules and increasing their effectiveness and constancy can be used for food preservation. Encapsulation of clove oil into DSPC liposomes enhanced its antibacterial action by 10 times when exam‐ ined to inhibit the growth of E. coli. Analyzing results of Differential scanning calorimetry and measuring phase transitions suggested that liposomes encapsulating clove oil had a membrane fluidization effect. The advantage of liposome entrapment is stabilizing the encapsulated bioactive macromolecules against various environmental and chemical traumatic factors as exposure to extreme pH and temperature, enzymatic digestion, presence of reactive chemicals and high ion concentration providing protection, keeping maintenance of the antimicrobial molecules and increasing their effectiveness, reliability and strength can be used for food preservation (da Silva Malheiros et al 2011). Very recently a study made by Hashemzadeh et al (2020) stated that one of the problems in using liposomes as drug carriers is their longterm instability
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