**1.3 Lipid nanoparticles**

*Nanoemulsions - Properties, Fabrications and Applications*

(O/W) nanoemulsions [16], encapsulation of hydrophilic drugs [17], enhanced bioavailability of drugs [18], and increased antimicrobial activity of essential oil [19]. **Figure 3** shows an enhanced inhibition level against *Escherichia coli* of garlic essential oil nanoemulsions (GEON) as compared to garlic essential oil [19]. The study by Katata-Seru et al. further revealed an easy and effective Taguchi method for optimizing GEON and as a potential alternative to antimicrobial broiler growth promoters. There are various types of nanoemulsions and the most common ones are O/W type, water-in-oil (W/O) type, and bi-continuous type, for example, water-in-oilin-water (W/O/W) type. A number of different preparation techniques for nanoemulsions have been investigated intensively using low and high energy. Low energy includes spontaneous emulsification and phase inversion temperature, while highenergy such as microfluidics, high-pressure homogenizers, or ultrasound equipment methods are used. The food-grade nanoemulsions have generated a huge interest using processing operations such as homogenization and mixing and shearing and homogenization [7, 20]. Recently, Öztürk evaluated various studies on enhanced bioavailability of vitamins A, D, and E encapsulated in O/W nanoemulsions and their factors affecting their stability [16]. Emulsion systems for encapsulation of vitamin E showed that nanoemulsion formulation improved the emulsion stability with an average particle size of 277 nm when compared to the standard emulsion [20]. Although it appears that significant research on nanoemulsions is on the rise, Öztürk highlighted a need for more in vivo bioavailability studies of the foods fortified with

*Photographic evidence of the antimicrobial inhibition of (A) garlic essential oil and (B) garlic essential oil* 

lipophilic vitamins as their studies are few owing to the higher costs.

Polymeric nanoparticles (NPs) are solid carriers capable to adsorb, disperse, entrap, and attach active ingredients to its matrices with the size of smaller than 1 μm. They are produced from preformed polymers by emulsion solvent evaporation, salting out, dialysis, nanoprecipitation, and supercritical fluid (SCF) technology. The NPs have displayed fairly good stability, higher loading efficiency, and controlled release of bioactive compounds as compared to emulsion, micelles, and

**34**

**Figure 3.**

*nanoemulsions [19].*

**1.2 Polymeric nanoparticles**

Lipid nanoparticles were developed as an alternative to traditional nanosystems such as polymeric particles and liposomes. Lipid nanoparticles can be defined as colloidal particles composed of lipids stabilized by surfactants that are solid at ambient temperature with sizes varying between 40 and 1000 nm [24, 25]. The first lipid nanoparticle to be produced was solid lipid nanoparticles as depicted in **Figure 4**. SLN is made from solid lipid only. The second generation of lipid nanoparticles was developed a few years later called nanostructured lipid nanoparticles (NLC). NLC is made from a blend of solid and liquid (oil) lipids [26]. The addition of oil in NLC formulation is meant to distort the formation of perfectly structured lipid crystals found in SLN, thus creating more room with uptake capacity for the encapsulated active. This was first shown by Jenning and Gohla, when they increased the loading capacity of retinol (vitamin A) from 1 to 5% by using NLC [27].

Lipid particles can be produced using various methods such as high-pressure homogenization, microemulsion, emulsion solvent evaporation, emulsificationsolvent diffusion, solvent displacement, phase inversion, ultrasonication, and membrane contractor technique [24]. However, of these techniques, only a few have been applied to prepare lipid nanoparticles with vitamins. Vitamins are sensitive

#### **Figure 4.**

*Models for the structure solid lipid nanoparticles and nanostructured lipid carriers that can be obtained under different conditions determined by the nature of the components and their relative solubility [25].*

bioactives, and thus care should be taken to employ techniques that will retain their activity during formulation. The most widely used techniques to prepare lipid nanoparticles with vitamins are the emulsion solvent evaporation method, highpressure homogenization, and microemulsions.

### *1.3.1 Emulsion solvent evaporation method*

This method is based on the dispersion of a solution of the lipid components in an aqueous surfactant solution. The lipids and the lipophilic bioactive are commonly dissolved in an organic solvent such as dichloromethane, cyclohexane, ethyl acetate, or chloroform. When the nanoemulsion is formed, the solvent is extracted or evaporated, and the droplets start to solidify until solid lipid nanoparticles encompassing the active are formed. The solvent can be evaporated by agitation, rotary evaporation, or spray-drying [28]. The emulsion solvent evaporation method offers a great advantage for encapsulating actives that are highly sensitive to heat such as vitamins as no thermal stress is needed [29].

## *1.3.2 High-pressure homogenization*

This technique involves the preparation of a pre-emulsion, which is then passed under high pressure (100–2000 bar) through a homogenizer valve. The pre-emulsion generally composes a lipid phase and an aqueous phase containing a surfactant. The fluid is accelerated in a very short distance in the homogenizer, reaching a high speed. The lipid substances are then divided into small droplets by the shear stress forces. This technique may produce particles with low encapsulation efficiency for hydrophilic substances due to the drug migrating to the external aqueous phase during particle formation. However, lipophilic actives can be encapsulated at high dosage [30, 31]. The technique is also ideal for the production of large quantities of sterile particles, which is an advantage for nutraceuticals [26].

#### *1.3.3 Microemulsions*

Microemulsions are clear, thermodynamically stable, and isotropic liquid mixtures of oil, water, and surfactant and almost always co-surfactant as well. The droplet size in the dispersed phase of the microemulsion is less than 100 nm. The droplets are formed by the drastic cooling of a microemulsion mixture to solidify the droplets and create particles loaded with the bioactive. The preparation of microemulsions does not require much energy to form and is thus recommended for actives that are highly sensitive to shear forces or thermal stress as is the case with most vitamins [29]. Other advantages of microemulsions include the use of bioactive compatible ingredients and the enhanced stability of formulations, as they are thermodynamically stable [32].

After preparation, lipid nanoparticles can be stored as nanosuspensions in the medium they were formed, or dry particles can be obtained using either freezedrying or spray-drying [25]. In some instances, aggregation of particles may occur due to the drying process. In these instances, an adequate amount of cryoprotectant can be added to prevent or minimize aggregation of the particles [30].

#### *1.3.4 Lipid nanoparticles for the delivery of vitamins*

There has been an increasing awareness of maintaining personal health by balanced nutrition and the intake of nutraceutical supplements. Due to the challenges faced with the stability of nutraceuticals, lipid formulations have been sought to

**37**

*Nanoformulated Delivery Systems of Essential Nutraceuticals and Their Applications*

enhance the stability of these bioactives. Lipid nanoparticles are highly recommended for the delivery of vitamins firstly due to their physical stability, secondly due to their ability to protect actives from environmental factors such as oxidation, hydrolysis, and possibly enzymatic degradation in the gastrointestinal tract, and thirdly due to their cost-effective production at large scale, for example, high-

Following the study by Jenning and Gohla, liposoluble vitamins A, D, E, and K as well as their derivatives have been presented as good candidates for encapsulation using lipid systems due to their low bioavailability and relative instability [33]. With the aim of increasing the intestinal absorption of vitamin K, vitamin K1 was encapsulated in SLN and demonstrated stability for more than 2 days in simulated gastric and intestinal fluids. The encapsulation also increased storage stability of vitamin K1 up to 4 months at 25°C [34]. Vitamin A in the form of all trans-retinol suffers degradation reactions that are characteristic of conjugated double bonds resulting in loss of its bioactivity. The vitamin was encapsulated in SLN and demonstrated an enhancement of retinol stability, photostability, and preservation of its antioxidant activity [35]. The lipophilicity, chemical instability, and poor skin penetration of vitamin E have limit its effectiveness as an antioxidant and photoprotectant used in various pharmaceutical and cosmetic products [25]. Various lipid formulations with vitamin E were developed, and the results obtained showed the possibility to enhance chemical stability and physical stability of Vitamin E in a cream [36]. In other formulations, Tween 80 was mixed with various lipids and surfactants to produce particles with the ability to protect vitamin E against photodegradation [37, 38]. Ying and Misran produced a thermoresponsive gel

for topical application that could control the release of vitamin E [39].

as the properties of the drug incorporated into the core [43].

**1.5 Supercritical fluid technology**

Polymeric micelles are formed from block copolymers that have amphiphilic character. Amphiphilic polymers are copolymers composed of hydrophilic ("waterloving") and hydrophobic ("water-hating") parts [40]. They normally form spontaneously under certain concentrations and temperatures in a given media [41]. The concentration at which these micelles are formed is known as critical micelle concentration (CMC), while the temperature at which this micelle exists is called the critical micellization temperature (CMT) [41]. Hydrophobic blocks of amphiphilic polymers form the core of the micelle, while the hydrophilic blocks form the shell [42, 43]. They can be utilized as drug carriers, by incorporating the poorly soluble nonpolar substances within the micellar core and polar substances on the micellar shell (by adsorption); substances with intermediate polarity are distributed between the core and shell [41, 44]. These properties enable these systems to incorporate poorly water-soluble drugs in the micellar core by physical interaction or by chemical conjugation leading to higher solubility extents [43], to protect the drugs or sensitive substances from premature degradation and also reduce the toxicity of the drug [42]. When compared to conventional micelles, polymeric micelles have lower CMCs values and are more stable even at concentrations below CMC [41]. This behavior stems from the slower rate of dissociation that depends on the molecular weight and hydrophilic-hydrophobic balance of the polymer as well

The methods discussed in the preceding sections involve the use of organic solvents, which could impart residual moisture of organic solvents on the produced nanoparticles. Supercritical fluid technology, on the other hand, utilizes the CO2, which often

*DOI: http://dx.doi.org/10.5772/intechopen.86170*

pressure homogenization.

**1.4 Polymeric micelles**

### *Nanoformulated Delivery Systems of Essential Nutraceuticals and Their Applications DOI: http://dx.doi.org/10.5772/intechopen.86170*

enhance the stability of these bioactives. Lipid nanoparticles are highly recommended for the delivery of vitamins firstly due to their physical stability, secondly due to their ability to protect actives from environmental factors such as oxidation, hydrolysis, and possibly enzymatic degradation in the gastrointestinal tract, and thirdly due to their cost-effective production at large scale, for example, highpressure homogenization.

Following the study by Jenning and Gohla, liposoluble vitamins A, D, E, and K as well as their derivatives have been presented as good candidates for encapsulation using lipid systems due to their low bioavailability and relative instability [33]. With the aim of increasing the intestinal absorption of vitamin K, vitamin K1 was encapsulated in SLN and demonstrated stability for more than 2 days in simulated gastric and intestinal fluids. The encapsulation also increased storage stability of vitamin K1 up to 4 months at 25°C [34]. Vitamin A in the form of all trans-retinol suffers degradation reactions that are characteristic of conjugated double bonds resulting in loss of its bioactivity. The vitamin was encapsulated in SLN and demonstrated an enhancement of retinol stability, photostability, and preservation of its antioxidant activity [35]. The lipophilicity, chemical instability, and poor skin penetration of vitamin E have limit its effectiveness as an antioxidant and photoprotectant used in various pharmaceutical and cosmetic products [25]. Various lipid formulations with vitamin E were developed, and the results obtained showed the possibility to enhance chemical stability and physical stability of Vitamin E in a cream [36]. In other formulations, Tween 80 was mixed with various lipids and surfactants to produce particles with the ability to protect vitamin E against photodegradation [37, 38]. Ying and Misran produced a thermoresponsive gel for topical application that could control the release of vitamin E [39].
