Page 13 - Bioencapsulation_Innovations_2015_11
P. 13
November 2015
Pinto, F., De Barros, D.P.C., Fonseca, L.P. – Instituto Superior Técnico, Universidade de Lisboa, Portugal
The use of natural ingredients is high- ly pursued, particularly in cosmetics, with an ongoing search for developing efficient products with broad biolo- gical relevance (Niculae et al., 2013). Vegetable or natural oils exhibit great interest as raw materials in all sectors of industry, due to their well-known beneficial health effects. They present inherent antioxidant, anti-carcinoge- nic and anti-inflammatory activities which are maintained or can be en- hanced once encapsulated at nanos- cale (Badea et al., 2015). Solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), nanoemulsions (NEs) and nanocapsules (NCs), have been used to incorporate and deliver active molecules in cosmetic pro- ducts (Montenegro, 2014). NLCs are composed of a mixture of solid lipids and oils that is stabilized by an outer layer of surfactants and which allows the formation of an overall amorphous nanostructured with many imperfec- tions within its matrix, providing NLCs a higher drug capacity and a lesser de- gree of drug expulsion during storage (Zheng et al., 2013). These lipid sys- tems are safe and biodegradable car- riers due to their generally recognized as safe (GRAS) ingredients. Moreover, the NLCs present several advantages as improved drug loading capacity and less drug expulsion during storage, enhanced permeation, low production
cost and are easy to scale up (Pinto et al., 2014).
The main subject under scope of this work is to develop safe and effective lipid nanocarriers based on natural ingredients that can be incorporated in cosmetic formulations to successfully deliver active ingredients. The present study aimed to evaluate the influence of vegetable oils in different propor- tions and the effect of the fatty acid chain length of solid lipids on struc- ture and on physicochemical proper- ties of NLCs. Contributions of the solid and liquid lipids to the particle distri- bution were analyzed by dynamic light scattering (DLS).
Solid lipids: capric acid, C10 (≥98%); lauric acid, C12 (≥98%); myristic acid, C14 (Sigma Grade, ≥99%); palmitic acid, C16 (≥99%) and stearic acid, C18 (≥95%) were purchased from Sigma- Aldrich (St. Louis, MO, USA). Liquid oils: Sunflower oil (SF), (Fula, Portu- gal) and olive oil (OV), (Gallo, Portugal) were food grade commercial products; sweet almond oil (SA), (Well’s, Portu- gal) cosmetic grade; coconut oil (CO), with analytical grade (Supelco, USA). Tween 80 (polyoxyethylene sorbitan monooleate) was obtained from Merck (Darmstadt, Germany). The aqueous phase of miniemulsions was prepared with Milli-Q water.
Preparation of NLCs
The vegetable oil-NLCs were prepared by the miniemulsions methodology with an ultrasonication step. The aqueous phase consisted in 2,5% (wt%) of surfactant (Tween 80) in Milli-Q wa- ter and the lipid phase, 5% (wt%), consisted in a
blend of a solid lipid with a vegetable oil. The lipid phase was heated to 70oC until the solid and liquid lipids were blended and melted to form a uniform and clear oil phase. This phase was af- ter added to the aqueous at the same temperature and both phases were mixed by the aid of magnetic stirring for 30 min. The pre-miniemulsion was then fully homogenized with a probe- type sonicator (Sonopuls - Ultrasonic homogenizer, Bandelin, Germany) for 5 min. The resultant nanoemulsion was subsequently cooled to room tem- perature and stored.
Characterization of particle size, PDI and surface charge
Particle size, which yields the hydrody- namic diameter, Rd (intensity weighted mean diameter) and polydispersity in- dex (PDI) were determined by dynamic light scattering (DLS), using a Malvern Zetasizer Nano ZS (Malvern Instru- ments, UK). Prior to measurements, all samples were diluted using Milli-Q water to produce an adequate scatte- ring intensity. All measurements were performed at 25°C and data was given as average of three individual mea- surements. Each measurement was performed in triplicate at 25°C. The zeta potential (ZP) reflects the electric charge on the particle surface and in- dicates the physical stability of colloi- dal systems and it was measured with the same equipment by using electro- phoretic light scattering technique.
Effect of oil content and com- position on NLCs size and phy- sical stability
In this study, NLCs were prepared with capric acid (C10) as solid lipid and with
50 0
0,350 0,300 0,250 0,200 0,150 0,100 0,050 0,000
SF OV CO SA Z.average (d.nm) PDI
Figure 1 – Mean particle size and PDI data of NLC
Figure 1 – Mean particle size and PDI data of NLC formulations
formulations based on particle size measurements.
based on particle size measurements. Influence of oil content and
Influence of oil content and composition on NLCs made
composition on NLCs made from capric acid (C10) as solid lipid.
from capric acid (C10) as solid lipid.
80:20 60:40 40:60 20:80 0:100 80:20 60:40 40:60 20:80 0:100 80:20 60:40 40:60 20:80 0:100 80:20 60:40 40:60 20:80 0:100

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