Thymol-loaded lipid nanovectors from the marine microalga Nannochloropsis sp. as potential antibacterial agents

The massive use of traditional pesticides represents a worldwide problem that can no longer be postponed, due to the serious impact that these agrochemicals display on the environment. Possible strategies to lower their use include the development of natural antimicrobial agents and the improvement of their delivery efficacy. In this study, nanovectors composed of lipids extracted from the marine microalga Nannochloropsis sp. were fabricated, structurally characterized, and loaded with thymol. These nanovectors were tested as antibacterial agents against the plant pathogen Xanthomonas campestris pv. vesicatoria. The mean size of the nanoparticles was below 150 nm, with a polydispersity index ranging from 0.12 and 0.33 and a slightly negative surface charge (-4.74 to -1.19 mV). Their "backbone" was mainly made of neutral lipids, representing 76% of the lipid fraction. Concerning the loading ratio, more than 70% of thymol was uploaded into the carriers. In vitro tests showed marked bactericidal effect of the thymol-delivering nanovectors at the concentration of 250 ppm. Similar results were obtained from standard liposomes made of purified soybean phosphatidylcholine, thus encouraging further investigation on the potentialities of this algae-derived nanoformulation as novel drug delivery system.