MATERIALS SCIENCE and TECHNOLOGY Edited by Evvy Kartini et.al. THE INFLUENCE OF OILS AND SURFACTANTS ON THE FORMATION OF SELF-NANOEMULSIFYING DRUG DELIVERY SYSTEMS (SNEDDS) CONTAINING THERAPEUTIC PROTEIN Heni Rachmawati, Dita Herawati Rasaputri, Raphael Aswin Susilowidodo, Sasanti Tarini Darijanto, Yeyet Cahyati Sumirtapura School of Pharmacy, Bandung Institute of Technology, Ganesha 10, Bandung, Indonesia e-mail: h_rachmawati@fa.itb.ac.id ABSTRACT Emulsion is a mixture of two or more immiscible liquids (usually oil and water) that one liquid is dispersed (the dispersed phase) in the other (the continuous phase) with addition of emulsifying agent to stabilize the system. While, nanoemulsion is thermodynamically stable system with the droplet size usually less than 100 nm. Surfactant as the one of emulsifying agents is the important material to form emulsion system and nanoemulsion as well. Aim of this study is to observe the influence of oils, surfactants, co-surfactant, and ratio of drug, oil, surfactant, and co-surfactant in the formation of self-nanoemulsifying drug delivery system (SNEDDS). In this study, oil-in-water (o/w) nanoemulsion was prepared to encapsulate Bovine Serum Albumin (BSA), i.e. a highly hydrophilic macromolecule. Parameters determining the successful of SNEDDS construction were droplets size, distribution size that is represented by polydispersity index, entrapment efficiency, and physical stability. Size and distribution size of SNEDDS were determined by photon correlation spectroscopy (PCS). Entrapment efficiency of protein in the SNEDDS was measured by colorimetry using Bradford method. Results showed that SNEDDS was formed with composition of glyceryl mono oleate 10%, cremophor RH40 80%, PEG 400 10%, and solid dispersion of BSA- SoyPC (1:3) i.e equals to 0.01% BSA in SNEDDS. This formulation resulted droplet size in mean diameter of 469.2±20.1 nm, polydispersity index (PI) 0.265±0.012, and zeta-potential - 0.92±0.11 mv. More than 90% of BSA was entrapped in the SNEDDS. Overall we concluded that BSA-containing SNEDDS has been constructed. Critical factors including oils, surfactants, co-surfactant, and ratio of drug, oil, surfactant, and co-surfactant influenced the characteristics of SNEDDS. BSA-containing SNEDDS showed neutral system with droplet size in range of nanometer with the entrapment efficiency more than 90%. Keywords : nanoemulsion, SNEDDS, bovine serum albumin (BSA) INTRODUCTION Emulsion is a thermodynamically unstable system consisting of at least two immiscible liquid phases (usually oil and water), that one liquid is dispersed as globules (the dispersed phase) in the other (the continuous phase), stabilized by the presence of an emulsifying agent. While, nanoemulsion is thermodynamically stable system with the droplet size usually less than 100 nm. Surfactant (surface-active agent) as emulsifying agents is the most important material to form both emulsion and nanoemulsion. It is adsorbed at oil-water interfaces to form monomolecular films and reduce interfacial tension leading to stabilization.
Materials Science and Technology Nanoemulsions have been widely studied to increase the bioavailability of waterinsoluble drugs by improving drug solubility, protecting against harsh environment, increasing specific surface area of droplets as well as inducing permeability [1]. Nanoemulsions have also been previously studied as a delivery system for hydrophilic drugs such as protein. Oral delivery of protein/peptide usually results in poor bioavailability. Two major reasons of this result are low permeation of the protein due to large size and high hydrophilicity, and extensive degradation in harsh environment of gastrointestinal tract. In this study, we provide a novel approach to improve both protein absorption and stability. We proposed o/w (oil in water) self-nanoemulsifying drug delivery system (SNEDDS) to encapsulate bovine serum albumin as a protein model. This system does not use high energy, so that protein degradation/denaturation does not occur during the preparation. SNEDDS are defined as isotropic mixtures of natural or synthetic oils, solid or liquid surfactants, or alternatively, one or more hydrophilic solvents and co-solvents/surfactants that have a unique ability of forming fine oil-in-water (o/w) nanoemulsions upon mild agitation followed by dilution in aqueous media, such as GI fluids. SNEDDS spread readily in the GI tract, and the digestive motility of the stomach and the intestine provide the agitation necessary for self-emulsification [2]. The successful formation of SNEDDS can be characterized by droplets size, distribution size represented by polydispersity index, entrapment efficiency, and physical stability. Our present study reports SNEDDS as a new strategy in the formulation technology to encapsulate bovine serum albumin (BSA). EXPERIMENTAL METHOD Material Bovine serum albumin (BSA), oleic acid, glyceryl mono oleate (GMO), polysorbate- 20, polysorbate-80, cremophor RH40, cremophor EL, polyethylene glycol-400 (PEG-400), ethanol 95%, hydrogenated soy phosphatidyl choline (SoyPC) were donated from Bintang Toedjoe, Indonesia. Bradford s reagent was purchased from Biorad. Construction of SNEDDS SNEDDS are an oil solution consisted of oil, surfactant and cosurfactant spontaneously forming nanoemulsion when mixed with water. Two oils, four non-ionic surfactants and one cosurfactant were used in this study for the construction of SNEDDS prototypes (Table 1). Oil/surfactant/cosurfactant (each of 1 g) was put in a breaker, set up with gentle magnetic stirring (100 rpm), and added drop wise of de-ionized water (5 ml). Nanoemulsion must be as a clear and transparent liquid. Various factors influencing SNEDDS characterization are presented in Table 2. Table 1: Characteristic of SNEDDS forming materials Component Name Chemical name HLB value oils Oleic acid Octadecenoic acid 1 Peceol Glyceryl mono oleate 3 Surfactants Cremophor EL Polyoxy ethylene 35 castor oil 12-14 Cremophor RH40 Polyoxy ethylene 40 hydrogenated castor oil 14-16 Polysorbate-80 Polyoxyethylene 20 sorbitan mono oleate 15 Polysorbate-20 Polyoxyethylene 20 sorbitan mono laurate 15 Cosurfactant PEG 400 Polyethylene glycol 400-248
The Influence of Oils and Surfactants on The Formation Table 2: Factors influencing SNEDDS characteristics Value Parameters 1 2 3 Surfactant-cosurfactant ratio 8:1 7:2 7:1 Concentration of oil 1 1 2 Preparation of solid dispersion of BSA Aqueous dispersion of SoyPC in phosphate buffer saline (PBS) was mixed with BSA solution in PBS at the weight ratio 3:1 (SoyPC:BSA). Then this mixture was lyophilized at a condensation temperature of -80 C. The resultant freeze-dried powder was the solid dispersion of BSA. Preparation of BSA-loaded SNEDDS BSA was loaded into SNEDDS by dissolving the solid dispersion of BSA into SNEDDS prototype. Fixed amount of BSA solid dispersion (1 mg) was added to 10 g of SNEDDS prototype. The mixture was stirred for 2 h and then placed in the sonicator (Branson, Model 5510) maintained at 25 C for 60 min. If a clear oily solution was obtained, it indicated that the BSA solid dispersion was soluble in that particular SNEDDS prototype system. Figure 1: Schematic diagram of BSA-loaded SNEDDS preparation. Characterization of BSA-loaded SNEDDS a. Droplets size, distribution size and zeta-potential The droplet size of BSA-loaded SNEDDS nanoemulsion and distribution size were determined using a photon correlation spectroscopy (Delsa TM Nano C Particle Analyzer, Beckman Coulter). One g BSA-loaded SNEDDS was dispersed in 5 ml deionized water and measured. Zeta-potential was determined using electrophoretic light scattering (Delsa TM Nano C Particle Analyzer, Beckman Coulter) b. Entrapment efficiency The entrapment efficiency of BSA was studied by precipitating 1 g SNEDDS with 2% TCA solution in water (4 ml). Precipitated was washed with 2% TCA solution three times, and then dissolved in 1 ml water. Twenty µl BSA solution was added into 1 ml Bradford s reagent, incubated 5 min, subsequently the absorbance was measured using 249
Materials Science and Technology spectrophotometer visible at 595 nm. Entrapment efficiency of BSA in SNEDDS was calculated by formula below. BSA added in SNEDDS free BSA % entrapment efficiency 100% BSA added in SNEDDS c. Physical stability The physical stability of BSA-loaded SNEDDS was studied by accelerated stability testing during 7 days at 40±2 C/75±5% RH and measured each day for formula A. Parameters evaluated were droplets size, distribution size and zeta-potential. RESULTS AND DISCUSSION Influence of oils, surfactants and cosurfactant on construction of SNEDDS Self-microemulsification has been shown to be specific to the nature of oil, nature of surfactants and cosurfactant, surfactant and cosurfactant concentration, and that only very specific combination of these ingredients could result in efficient self-microemulsification[1]. On optimizing formulation, the most appropriate ratio of oil:surfactant:cosurfactant was 1:8:1. It suggests that there is a relationship between the droplet size and the concentration of the surfactant. Increasing the surfactant concentration leads to droplets build up with smaller mean size. Stabilization of the oil droplets as a result of the localization of the surfactant molecules at the oil-water interface may explain this phenomenon [2]. Upon dilution in water, two surfactants i.e. Cremophor RH40 and polysorbate-20, played role in the formation of transparent emulsions in combination with PEG-400 as cosurfactant and Peceol as an oil phase. While, oleic acid showed contrast performance in which turbid emulsion was formed when used as oil phase. Transparent emulsion indicated that SNEDDS is successfully constructed. Visual characterization of SNEDDS prototypes is shown in figure 2. 250 (a) (b) (c) (d) Figure 2: Visual characterization of SNEDDS prototypes. (a) peceol: Cremophor RH40: PEG400 (1:8:1); (b) peceol: polysorbate-20: PEG400 (1:8:1); (c) oleic acid: Cremophor RH40: PEG400 (1:8:1); (d) oleic acid:polysorbate-20:peg400 (1:8:1). a and b exhibits clear-stable system. Both oleic acid and peceol are unsaturated long chain fatty acid containing carbon chain length of 18 and 21, respectively. Peceol has HLB (hydrophilic-lipophilic balance) value greater than oleic acid. It seems that oils with higher HLB value are better to form SNEDDS. This explains why peceol produced successful SNEDDS formulation than oleic acid [1]. In general, the surfactant for SNEDDS should be very hydrophilic with HLB value in the range of 15-21[1]. The higher the HLB is, the easier to dissolve in water. Cremophor RH40 and polysorbate-20 are capable to form SNEDDS in combination with peceol. By
The Influence of Oils and Surfactants on The Formation contrast, neither cremophor EL nor polysorbate-80 provided any SNEDDS prototype. These results indicate that HLB is important parameter determining the surfactant s ability to form SNEDDS. The structure of the surfactant also played an important role. Cremophor is polyethoxylated castor oil which is a mixture of ricinoleic acid, polyglycol ester, glycerol polyglycol ester, and polyglycol whereas polysorbate is a derivative of polyoxylated sorbitol and oleic acid. Cremophors have branched alkyl structure whereas polysorbate has linear chain alkyl structure. It was reported that alkyl chain structure of surfactant impact an effect on penetration of oil onto the curved surfactant film thus resulting in the self-nanoemulsion formation [1]. Cosurfactant helps the surfactant to form stable SNEDDS. It is amphiphilic with an affinity for both oil and aqueous phases and partitions to an appreciable extent into the surfactant interfacial monolayer present at the oil-water interface. Cosurfactant provides very low interfacial tension required for the stability and formation of nanoemulsion. In this present study, PEG400 was suitable as cosurfactant. Two formulas in Table 3 have the droplet size <50 nm and PI <0.5. It shows that SNEDDS (droplet size <50 nm) was formed with uniform size. The formula for further studied was formula A. One consideration is oral acceptance, in particular for the surfactant [2]. Cremophor RH40 is castor oil derivative. It manufactured from nature and widely used in oral pharmaceutical formulation. Table 3: Droplet size and polydispersity index (PI) of SNEDDS prototypes Formula oil phase Droplet size (nm) (mean±s.d., n=3) PI (mean±s.d., n=3) A Peceol:cremophor RH40:PEG400 (1:8:1) 21.4±5.8 0.245±0.177 B Peceol:polysorbate-20:PEG400 (1:8:1) 14.9±3.8 0.081±0.040 Entrapment efficiency of BSA in SNEDDS. In order to load BSA (a highly hydrophilic protein) into SNEDDS, a solid dispersion of BSA-SoyPC was prepared. Firstly, BSA was dispersed at the single-molecular level into an amphiphilic material such as SoyPC. The rationale is that SoyPC will cover BSA to form a micelle structure in the oil, dissolving in the oil phase [1]. Table 4 shows the influence of ratio BSA-SoyPC on the entrapment efficiency of BSA in formula A. Limit of quantification (LOQ) of Bradford method was 21.2 µg/ml, meaning that the amount of free BSA in aqueous phase us undetected. We therefore come up with the conclusion that > 90% of BSA was loaded in SNEDDS. Figure 3: Visual characterization of BSA-SoyPC solid dispersion-loaded SNEDDS of peceol:cremophor RH40:PEG400 (1:8:1). Ratio BSA- SoyPC Table 4: Influence of ratio BSA-SoyPC on entrapment efficiency of BSA in SNEDDS Amount of free BSA in aqueous phase (µg) (mean±s.d., n=3) Amount of BSA (µg) in 1 g SNEDDS prototype 1:3 7±4.1 93 93 1:4 22.8±12.98 77.2 77.2 Entrapment efficiency (%) 251
Materials Science and Technology Physical stability of BSA-loaded SNEDDS. Physical stability of BSA-loaded SNEDDS (formula A) is shown in figure 4. As shown, that droplet size of BSA-loaded SNEDDS is bigger (20 times) than corresponding placebo. (a) (b) (c) Figure 4: Physical stability of accelerated stability testing for 7 days at ambient condition. (a) droplet size; (b) polydispersity index; (c) zeta-potential. The zeta-potential of system is -0.92 mv to -6 mv (nearly neutral). Theoretically, the zeta-potential from 0 to +/- 5 mv indicates rapid coagulation or flocculation. However, the droplet size and distribution size remained unchanged after 7 days storage. This indicates that the system is stable. The low zeta-potential value indicates that the system is neutral due to of non-ionic surfactant at the surface of droplets. Non-ionic surfactant stabilizes the system through steric protection avoiding droplets aggregation during storage. CONCLUSION Oils, surfactant, cosurfactant, and the ratio of those three components influence the construction of stable SNEDDS. SNEDDS seems to be a potential carrier to deliver highly hydrophilic macromolecules such as protein, for oral route. REFERENCES [1]. S. V. R. Rao and J. Shao, Int. J. Pharm., 362, (2008) 2-9 [2]. A. U. Kyatanwar,, K. R. Jadhav, and V. J. Kadam, Journal of Pharmacy Research, 3(1), (2010) 75-83 [3]. E. I. Taha, Sci. Pharm, 77, (2009) 443-451 [4]. P. Gao, M. J. Witt, R. J. Haskell, K. M. Zamora, J. R. Shifflett, Pharmaceutical Development and Technology, 9(3), (2004) 301-309 [5]. F. S. Nielsen, et. al., J. Pharm. Sci., 96(4), (2007) 876-892 252