Encapsulation hydrophobic molecules

CeramiSphere technology is not limited to the encapsulation of small water-soluble molecules. It is also used to encapsulate hydrophobic molecules such as essential oils, flavours, vitamins, proteins (including enzymes) and many other biomolecules (such as DNA). 

The particular three-dimensional CD structure with its hydrophilic surface and apolar cavity, impacts water solubility and the ability to partially or totally encapsulate hydrophobic molecules of appropriated size and shape in aqueous solution as well as in solid-state through the formation of a reversible host-guest complex (Fig. 2.3) [2]. 

Release of DNA in vivo takes place due to the increased acidic conditions inside living cells that result in the destabilization of the ORMOSIL-DNA complex. SiCVbased nanoparticles, in fact, do not release encapsulated biomolecules because of the strong hydrogen bonding between the biomolecule s polar centres and the silanols at the cage surface (as ORMOSIL-entrapped hydrophobic molecules are not leached in aqueous systems due to strong hydrophobic interactions).17... 

In addition to the hydrophobic interaction mentioned above to encapsulate guest molecules, other types of nonspecific interactions have also been explored to enhance binding. For example, block copolymer micelles based on PEO as hydrophilic segments and poly(/3-benzyl L-aspartate) as hydrophobic blocks have used to encapsulate doxombicin. The encapsulation efficiency of doxombicin, an aromatic anticancer drug molecule, has been found to be significantly higher. This observation has been attributed to the tt-tt interaction between the anthracycUne moiety of doxorubicin and the benzyl group of poly(/3-benzyl L-aspartate) (Cammas-Marion et al. 1999). 

An alternative candidate for a cell membrane is one composed of mostly hydrophobic molecules that would spontaneously aggregate if suspended in water. It is important that the molecule is not entirely hydrophobic, like hexane or benzene, as some part of it must be solvated if it is to aggregate with others to form a structure capable of encapsulating other species. Candidates for this type of molecule are the lipids and related compounds. The formation of protocells by lipids has been discussed previously as part of the Lipid World hypothesis. In the context of compartmentalization it is important to consider how such an aggregate could evolve. 

The encapsulation of a fluorescent pyrenyl derivative, l-(4,6-dichloro-l,3,5-triazin-2-yl)pyrene (pyrene-R), has provided direct evidence for the release of a hydrophobic molecule from the metalla-cage [ (p v C6 A Me)Ru 6(p-dhbq)3 (tpt)2]6+> following uptake into cancer cells [61]. The fluorescence of pyrene-R has allowed monitoring of cellular uptake and accumulation, as well as an estimation of the efficiency of the [pyrene-Rc (/tPr C6H4Me)Ru 6((i-dhbq)3(tpt)2]6+ system to transport and release its cargo (Fig. 17). 

The ability of micelles to enhance photoionization yields of hydrophobic molecules was demonstrated in the early 1970s. Thus, the photoionization yields of pyrene [59], phenothiazine [60] and tetramethylbenzidine [61] cations increased when these molecules were encapsulated in anionic micelles. The effect was attributed to efficient escape of electrons from the geminate charge-separated species formed within the micelle, which is accelerated by the anionic interface. The negative micellar surface imposes an electrostatic barrier between the cations, which remain with the micelle, and the aqueous electron in the bulk water phase, thus increasing the lifetimes of the photoredox products. 

Qin et al. [229] produced a thermo-responsive PEO-fe-PNIPAM block copolymer that forms vesicles above the LCST of 32°C. The PEO-b-PNIPAm vesicles are shown to be stable at body temperature and to encapsulate both hydrophilic drugs (e.g., Doxorubicin) and hydrophobic molecules into their membranes (e.g., PKH 26). Temperature-controlled quick release of both types of compounds below 32°C was possible. 

Liposomes aid in formulation because they are powerful in solubilizing nonwater-soluble compounds, enhancing their bioavailability. Furthermore, liposomes entrap hydrophilic molecules into their interior, and hydrophobic molecules into their lipophilic membrane, encapsulating various nutritional molecules. The first example of liposomes in foods is human milk, which has been... 

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