Aminiemulsion (also known asnanoemulsion) is a particular type ofemulsion which is obtained byultrasonicating a mixture comprising twoimmiscible liquid phases (for example, oil and water), one or moresurfactants and, possibly, one or more co-surfactants (typical examples arehexadecane orcetyl alcohol). They usually havenanodroplets with uniform size distribution (20–500 nm) and are also known as sub-micron, mini-, and ultra-fine grain emulsions.[1]
Schematic illustration of nanoemulsion structure, including the biphasic systems (O/W or W/O), in which an appropriate volume of the internal oil phase is disseminated in the bulk aqueous solution or vice versa; and the multiple systems (W/O/W or O/W/O), within a single system, the inner water phase is dispersed in an oil phase, which is then dispersed in a bulk aqueous phase or vice versa.[2]
Selection of ingredients: The first step in creating a nanoemulsion is to select the ingredients, which include the oil, water, and emulsifying agent. The type and proportions of these ingredients will affect the stability and properties of the final emulsion.[3]
Preparation of oil and aqueous phases: The oil and water phases are separately prepared, with any desired ingredients, such as surfactants or flavoring agents, added at this step.
Mixing oil and emulsifier with stirrer: Next, the oil and water phases are mixed in the presence of an emulsifying agent, typically using a high-shear mixing device such as ahomogenizer or a high-pressure homogenizer.[4]
Aging and stabilization: Theemulsion is typically aged at room temperature to allow the droplets to stabilize, after which it can be cooled or heated as required.[4]
Optimizing and characterization: The droplet size and stability are then optimized by adjusting the ingredients and process parameters, such as temperature, pH, and mixing conditions. The nanoemulsion is also sterilized by filtration with 0.22μm. Several methods, such as DLS, TEM, and SEM, can characterize the final nanoemulsion's properties.[5]
Mini-emulsion: emulsion in which the particles of thedispersed phase have diameters in the range from approximately 50 nm to 1 μm.
Note 1: Mini-emulsions are usually stabilized against diffusion degradation (Ostwald ripening (ref.[6] )) by a compound insoluble in thecontinuous phase.
Note 2: The dispersed phase contains mixed stabilizers, e.g., an ionic surfactant, such as sodium dodecyl sulfate (n-dodecyl sulfate sodium) and a short aliphatic chain alcohol ("co-surfactant") for colloidal stability, or a water-insoluble compound, such as a hydrocarbon ("co-stabilizer" frequently and improperly called a "co-surfactant") limiting diffusion degradation. Mini-emulsions are usually stable for at least several days.[7]
Mini-emulsion polymerization: Polymerization of a mini-emulsion of monomer in which all of the polymerization occurs within preexisting monomer particles without the formation of new particles.[8]
There are two general types of methods for preparing miniemulsions:
High-energy methods - For the high-energy methods, the shearing proceeds usually via exposure to high powerultrasound[9][10][11] of the mixture or with a high-pressurehomogenizer, which are high-shearing processes.
Low-energy methods - For the low-energy methods, the water-in-oil emulsion is usually prepared and then transformed into an oil-in-water miniemulsion by changing either composition or temperature. The water-in-oil emulsion is diluted dropwise with water to an inversion point or gradually cooled to aphase inversion temperature. The emulsion inversion point and phase inversion temperature cause a significant decrease in theinterfacial tension between two liquids, thereby generating very tiny oil droplets dispersed in the water.[12]
Miniemulsions are kinetically stable but thermodynamically unstable.[13] Oil and water are incompatible in nature, and the interface between them is not favored. Therefore, given a sufficient amount of time, the oil and water in miniemulsions separate again. Various mechanisms such as gravitational separation,flocculation,coalescence, andOstwald ripening result in instability.[14] In an ideal miniemulsion system,coalescence andOstwald ripening are suppressed thanks to the presence of the surfactant and co-surfactant.[9] With the addition ofsurfactants, stabledroplets are then obtained, which have typically a size between 50 and 500 nm.[15][16]
Asterile filter is a device used to remove microorganisms and other contaminants from a liquid or gas, making it sterile.[17][18] Sterile filters are commonly used in the medical, pharmaceutical, and biotech industries to ensure that the products produced are free of bacteria and other harmful organisms.
There are different types of filters which include:
Depth filters: These filters use a matrix of fibers, beads, or powders to trap particles and microorganisms.[20] Examples of depth filters include cellulose, glass fiber, anddiatomaceous earth.[citation needed]
Adsorptive filters: These filters use adsorbent materials, such asactivated carbon, or specialized resins or beads, to remove certain types of contaminants by chemicaladsorption.[21][22][23]
A nanogenizer, also known as a high-pressurehomogenizer or a microfluidizer, is a device used to create small droplets or particles by applying high pressure to a liquid mixture.[24] These devices can be used to produce nanoemulsions, as well as other types ofemulsions and suspensions.[25] They work by passing the mixture through a small orifice under high pressure, which causes the liquid to be sheared and broken into small droplets or particles. The size of the droplets or particles can be controlled by adjusting the pressure and the design of the orifice.[26]
Ananoparticle sizer, also known as a nanoparticle analyzer, is a device used to measure the size, size distribution, and concentration ofnanoparticles in a sample.[27][28] The size of nanoparticles is typically in the range of 1 to 100 nanometers (nm), and they are much smaller than the particles that can be measured with conventional particle sizeanalyzers.[29]
Miniemulsions have wide application in the synthesis of nanomaterials and in the pharmaceutical and food industries.[30][31] For example, miniemulsion-based processes are, therefore, particularly adapted for the generation ofnanomaterials. There is a fundamental difference between traditional emulsion polymerisation and a miniemulsion polymerisation. Particle formation in the former is a mixture of micellar andhomogeneous nucleation, particles formed via miniemulsion however are mainly formed by droplet nucleation. In the pharmaceutical industry, oil droplets act as tiny containers that carry water-insoluble drugs, and the water provides a mild environment that is compatible with the human body.[32][33] Moreover, nanoemulsions that carry drugs allow the drugs to crystallize in a controlled size with a good dissolution rate.[34][35] Finally, in the food industry, miniemulsions can not only be loaded with water-insoluble nutrients, such asbeta-carotene andcurcumin, but also improve the nutrients' digestibility.[12] Miniemulsions are also used in the creation of cannabinoid infused beverages and foods. Emulsifying cannabiniods has shown to increasebioavailability and digestion time.[36]
^Moghassemi, Saeid; Dadashzadeh, Arezoo; Azevedo, Ricardo Bentes; Amorim, Christiani A. (1 November 2022). "Nanoemulsion applications in photodynamic therapy".Journal of Controlled Release.351:164–173.doi:10.1016/j.jconrel.2022.09.035.ISSN0168-3659.PMID36165834.
^Moghassemi, Saeid; Dadashzadeh, Arezoo; Azevedo, Ricardo Bentes; Amorim, Christiani A. (1 November 2022). "Nanoemulsion applications in photodynamic therapy".Journal of Controlled Release.351:164–173.doi:10.1016/j.jconrel.2022.09.035.ISSN0168-3659.PMID36165834.
^Richard G. Jones; Edward S. Wilks; W. Val Metanomski; Jaroslav Kahovec; Michael Hess; Robert Stepto; Tatsuki Kitayama, eds. (2009).Compendium of Polymer Terminology and Nomenclature (IUPAC Recommendations 2008) ("The Purple Book"). RSC Publishing.ISBN978-1-84755-942-5.
^Peshkovsky A, Peshkovsky S, "Acoustic Cavitation Theory and Equipment Design Principles for Industrial Applications of High-Intensity Ultrasound", Physics Research and Technology, Nova Science Pub. Inc., October 31, 2010,ISBN1-61761-093-3
^Broniarz-Press, L.; Włodarczak, S.; Matuszak, M.; Ochowiak, M.; Idziak, R.; Sobiech, Ł.; Szulc, T.; Skrzypczak, G. (2016-04-01). "The effect of orifice shape and the injection pressure on enhancement of the atomization process for pressure-swirl atomizers".Crop Protection.82:65–74.Bibcode:2016CrPro..82...65B.doi:10.1016/j.cropro.2016.01.005.ISSN0261-2194.
^Aizpurua, Imanol; Barandiaran, Marı́a J. (1999-06-01). "Comparison between conventional emulsion and miniemulsion polymerization of vinyl acetate in a continuous stirred tank reactor".Polymer.40 (14):4105–4115.doi:10.1016/S0032-3861(98)00641-7.ISSN0032-3861.