**Olive Oil-Based Delivery of Photosensitizers for Bacterial Eradication**

Faina Nakonechny1,2, Yeshayahu Nitzan2 and Marina Nisnevitch1 *1Department of Chemical Engineering, Biotechnology and Materials,* 

*Ariel University Center of Samaria, Ariel, 2The Mina and Everard Goodman Faculty of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel*

**1. Introduction** 

470 Olive Oil – Constituents, Quality, Health Properties and Bioconversions

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property of marine lipase from *Bacillus pumilus* B106 associated with South China Sea sponge *Halichondria rugosa*. *World Journal Microbiology Biotechnology*, Vol.25, Olive oil is a natural product of *Olea europaea*. It contains triacylglycerols of unsaturated and saturated fatty acids as well as free acids and numerous other biologically active components. Modern pharmaceutical industries are turning to natural herbal sources in order to find effective, low allergenic and non-irritating components that can be used in drug delivery systems or as recipients for both hydrophobic and hydrophilic active agents. Combining hydrophobic compounds with olive oil components is not problematic at all. However, this is quite different for hydrophilic compounds. One possible way for overcoming this problem is by mechanochemical treatment. This method has become widespread for preparing powdered solid materials in a large variety of compositions and involves the use of a conventional high-energy ball mill to initiate chemical reactions and structural changes of materials in solid-phase processes. Mechanochemical activation appears to be an environmentally friendly method, since it does not require organic solvents (Grigorieva et al., 2004; Margetić, 2005; Lugovskoy et al., 2008; Lugovskoy et al., 2009). It was shown that the mechanochemical method enabled some olive oil components to covalently attach to talc or to titanium dioxide - the solid ingredients of creams, ointments and powders (Nisnevitch et al., 2011). The remaining components were deeply absorbed by solid phases. New solid-phase composite materials which combined useful properties of various components with a different nature were thus created. Talc combined with olive oil exhibited good antioxidant properties scavenging ca. 40% of free radicals. Olive oil phenols with one or two hydroxyl groups, such as hydroxytyrosol, caffeic acid, photocatechuic acid, syringic acid, derivatives of elenolic acid, derivatives of oleuropein, tyrosol and some others are among the olive oil components responsible for its *in vitro* antioxidative activity (Papadopoulos & Boskou 1991; Briante et al., 2001; Lesage-Meessen et al., 2001; Tovar et al., 2001; Vissers et al., 2004). These compounds retain their antioxidant properties when combined with talc by a mechanochemical method. Furthermore, the possibility of combining water-soluble ascorbic acid (vitamin C) with olive oil on a talc or titanium dioxide support using mechanochemical activation has been reported (Nisnevitch et al., 2011). These triple mixtures (support-olive oil-ascorbic acid) scavenged free radicals instantly and totally due to the presence of ascorbic acid, which is a well-known effective

Olive Oil-Based Delivery of Photosensitizers for Bacterial Eradication 473

encapsulated in the inner space of unilamellar ones, and hydrophobic compounds can be

% in Virgin Olive Oil (Hatzakis et al., 2008)

12.3-19.7 11.2-19.4

cerols

% in EPC (Ternes, 2002; Sigma aldrich. com)

Triacylgly- lipids.com)

4.6-11.0 2.7-12.0 13-19 -

0.08-0.53 0.11-0.47 0-0.2 -

Phospho -lipids

% in DPPC (northern

27-33 100

13-15 -

incorporated into the lipid bilayers (Chrai et al., 2002).

Fatty acid Structure

Linoleic acid

Palmitic acid

Stearic acid

α-Linolenic acid

Fig. 1. Structure of a triacylglycerol. R – various residues of fatty acids.

Table 1. Main virgin olive oil, egg phosphatidylcholine and dipalmitoyl

phosphatidylcholine fatty acids. (Nichols & Sanderson, 2002; oliveoilsource.com)

Liposomes can be exploited as carriers for controlled drug delivery and targeting to cells. Liposome formulations of drugs have several advantages over the use of drugs in their free form: liposomes guarantee delivery of a highly concentrated drug, liposomes protect the drugs from degradation during the delivery process, liposomes are applicable for polar as well as for nonpolar drugs, and ingredients of the liposomes themselves are nontoxic and biodegradable (Chrai et al., 2002). Liposome components participate in drug delivery, but not in drug function, such that liposomes actually play the role of excipients (Chen, 2008). Additional ingredients can be incorporated into the phospholipid bilayer in order to impart needed properties to liposomes, as indicated by the following examples: negatively charged phosphatidylinositol or positively charged stearylamine can be incorporated into the phospholipid bilayer in order to obtain charged liposomes (Robinson et al., 2001); addition of cholesterol provides rigidity to the liposome structure (New, 1994). The latter example is

Oleic acid 72.0-81.6 72.5-82.9 26-31 -

antioxidant (Cathcart, 1985). The scavenging ability in the triple mixtures after mechanochemical treatment was as good as that of the double mixtures of ascorbic acid with the supports. Mechanochemical inclusion of ascorbic acid into composites of olive oil with talc or olive oil with titanium dioxide successfully combined hydrophobic and hydrophilic components and provided high antioxidant properties to the entire system despite the covalent bonding between the components (Nisnevitch et al, 2011).

New olive oil-based composite materials exhibit pronounced bactericidal properties. The antimicrobial activity of the mechanochemically treated triple mixtures which were pressed into pellets was examined against the Gram-positive *S. aureus* and the Gram-negative *E. coli* bacteria. Samples containing ascorbic acid on a titanium dioxide support were more effective against both bacteria than a talc support, probably because of weaker bonding of ascorbic acid to titanium dioxide than to talc, which contributed to better diffusion of the ascorbic acid out of the pellets. Gram-positive *S. aureus* was more sensitive to all the ascorbic acid-containing samples than the Gram-negative *E. coli*, but *E. coli* responded to addition of olive oil into both talc-ascorbic acid and titanium dioxide-olive oil mixtures. In the latter case, the inhibitory activity of the triple composites was higher than that of double ascorbic acid-support composites. The antimicrobial activity of all the ascorbic acid-containing samples depended on the ascorbic acid content in the pellets. Olive oil, olive fruit and olive leaf extracts are known to exhibit a broad antimicrobial, antimycoplasmal and antifungal spectrum due to the presence of long chain unsaturated aldehydes, phenolic glycoside oleuropein and several other phenol compounds (Fleming et al. ,1973; Kubo et al., 1995; Bisignano et al., 2001; Furneri et al., 2002; Medina et al., 2007; Covas et al., 2009; Kampa et al., 2009). Mechanochemical combination of natural antimicrobial agents from olive oil with ascorbic acid, which is a strong bacterial suppressor, enabled the production of highly active solid-phase antibacterial composites.

Hydrophilic and hydrophobic components can also be combined by encapsulating hydrophilic constituents in lipid vesicles called liposomes. Such lipid-based formulations are actually possible carriers for both hydrophobic and hydrophilic active components and can be applied as drug delivery systems. Liposome formulations possess enhanced abilities to penetrate the skin, thus improving the delivery process. Lipid-based drug administration can increase treatment efficiency in cases of skin infections and inflammations caused by bacterial invasion.
