## 5 Drug Delivery Systems
### Nanoemulsions  
Emulsions are formed by the dispersion of two immiscible phases: one phase (dispersed phase) is spread as droplets into another phase (continuous phase) [72]. Emulsions are created using various carrier materials like alginate, gum Arabic, lipids like soybean oil, or surfactant solutions like Surfynol, Tween, Span, Brij, or lecithin. Due to the low-cost carrier materials, producing EO emulsions is relatively cheap; they can be produced in larger quantities and are generally safe for organisms [72; 80]. Current studies have demonstrated their improved antimicrobial and cytotoxic effects compared to pure EOs [81; 82; 83]. This can stem from the fact that their properties enable them to disperse better, especially in food matrices [83].  
[PERSON] et al. [84] described a two-step emulsification and dry spraying technique that enabled them to cover a textile surface with an EO, which was proven to reduce its volatility and irritation potential. At the same time, they showed poor loading capacity, their water solubility is quite low, and they have been shown to undergo lipid oxidation. It may be important medically since lipid oxidation can induce an inflammatory response, whose effect in medical applications is unknown so far [80].  
A number of studies on the biological effects of nanoemulsions loaded with EOs/EOCs and their medical application can be found in the available literature. For example, [PERSON] et al. [85] showed that nanoemulsion of cinnamon EO could be effectively used against colistin-resistant _Klebsiella pneumoniae_. Aside from improved antibacterial activity, this study noted the significant downregulation of the _mcr-1_ gene expression, a fact that can be crucial in combating colistin resistance. What is more, [PERSON] et al. [86] used sophorolipids for nanoemulsion stabilization, which, when loaded with eugenol, showed excellent antimicrobial properties against _E. coli_ and _B. cereus_. In turn, [PERSON] et al. [87] conducted an animal trial on mice that used nanoemulsion loaded with cinnamon EO in the treatment of _Candida_ vaginitiis. Aside from antifungal properties, the formula also showed anti-inflammatory action by curbing the inflammatory cytokines. The results of this study are important to this topic as pure cinnamon EO cannot be readily used due to its hydrophobicity, hence the crucial role of the drug delivery system. Moreover, antifungal properties against various pathogenic species were also demonstrated in the case of the nanoemulsion loaded with clove EO [88]. Another example of research can be found in the work of [PERSON] et al. [89], who conducted tests for a possible burn-wound dressing consisting of nanoemulsion loaded with _Lavandula angustifolia_ EO. Their study showed mitigation of inflammation in the in vitro model. It is also worth emphasizing that the authors did not conduct an antimicrobial assay; as such, it is unknown whether the concentrations determined as safe would also exhibit potential to prevent skin sepsis. However, such an application may not be out of the scope, as [PERSON] and [PERSON] [90] showed that nanoemulsion loaded with eucalyptus, olive Eos, and tridosan could be topical antiseptic.