Development and Characterization of Drug-Loaded Self-Solidnano-Emulsified Drug Delivery System for Treatment of Diabetes

Embelin and gliclazide administration to diabetic rats cause a highly significantdecline in the blood glycated hemoglobin, serum glucose and nitric oxide activity with a concomitant increase in the serum insulin level. The aim of present work was the development and characterization of self-solid nano-emulsified drug delivery system (SNEDDS) formulation of embelin in combination with gliclazide for the determination of antidiabetic effect in Wistar rats. In this connection, we prepared SNEDDS by using an oil: surfactant mixture ratio of [Capmul® MCM: Kolliphor® HS 15: PEG 400(2:1)] and encapsulated the drug combination in this system. The in-vitro characterization of optimized liquid SNEDDS containing 40% surfactant mixture and 60% oil) was performed and the SNEDDS were found to have particle size of 159.9nm, polydispersity index of 0.289 and zeta potential of -34.35mV. Percentage cumulative release from this formulation was 94.26±3.80% for gliclazide and 90.63±3.67% for embelin in phosphate buffer (pH 7.4) compared to 39.09±1.38% and 34.29±1.20% from plain drug suspension. The embelin (30mg/kg)+gliclazide (10mg/kg) loaded SNEDDS was found to be effective in reversing streptozotocin-induced hyperglycemia as compared to pure drugs in Wistar rats. article history Received: 23 February 18 Accepted: 9 April 18

that the drugs (e.g., embelin and gliclazide), when administrated into diabetic rats caused a highly significant decline in the blood glycated hemoglobin.In addition to this, the serum glucose levels, and nitric oxide activity, with a concomitant increased the serum insulin level 1-2 .Also, the diabetic mellitus has been treated orally with herbal remedies based on traditional medicines like EmbeliaribesBurm (Myrsinaceae) 3 .In this connection, the Gandhi et al., isolated embelin from EmbeliaribesBurm being a fruit extract and evaluated it for its potential role to regulate insulin resistance, altering b-cell dysfunction and modulating key markers involved in insulin sensitivity and glucose transport.High-fat diet and streptozotocin, (40 mg/kg) were used to induced type 2 diabetes in rats 4 .Other researchers have reported the antidiabetic, antidyslipidemic and antioxidant activity of EmbliaribesBurm in streptozotocininduced diabetic rats, using gliclazide as the positive control drug 5 .The gliclazide is a second generation sulphonylurea which acts as a hypoglycemic agent.It stimulates bcells of the islet of Langerhans in the pancreas to release insulin.It also enhances peripheral insulin sensitivity.Overall, it potentiates insulin release and improves insulin dynamics.It is a lipophilic (log P=2.6) in nature and water-insoluble moiety belonging to Class II Drug (i.e., low solubility and high permeability) 6 .
It is estimated that 40% of active drug substances are poorly water-soluble in nature.For the improvement of bioavailability of these drugs with such attributes presents one of the greatest challenges in drug formulations.Technological strategies like solid dispersions, cyclodextrin complex formation, and/ or micronization are commonly used strategies 7 .Recently, nanotechnology 8-9 has gained much attention and these strategies can be used to deliver drugs in these formulations via different delivery systems like nanofibers 10 , nanoparticles 11 , nanorods 12 , and nanoemulsions 13 .Nanoemulsions in the form of self nano-emulsifying drug delivery system (SNEDDS) has gained much attention for enhancement of oral bioavailability with reduced dosage 14 .The SNEDDS are ideally isotropic mixtures of oils, surfactants, and co-surfactant/cosolvents, which when introduced into aqueous phase emulsifies spontaneously to produce fine oil-in-water emulsions (or micro-emulsions/nanoemulsion) upon gentle and mild agitation 15 .Currently, SNEDDS are developed and formulated using surfactants having hydrophile-lipophile balance value less than 12 16 .Furthermore, the oral delivery of solid dosage form of lipophilic drug compounds is usually hindered due to their high lipophilicity and low water solubility.Therefore, the oral route is the most preferred and desirable strategy for chronic drug therapy.Tremendous potent lipophilic drugs exhibit low oral bioavailability, low absorption, and low efficacy after in-vivo administration due to their poor aqueous solubility.When a least amount of the administered dose reaches the pharmacological site of action, the remainder later on causes toxicity and sideeffects due to undesirable biodistribution.As far as biopharmaceutics classification system is concerned, only 34% of drugs belong to class I, while as remaining drugs belong to class II-IV (17% to class II, 39% to class III and 10% to class IV), respectively 17 .
SNEDDS have also attracted interest because they can improve the bioavailability of compounds that fall into class II (compounds are poorly water soluble and highly permeable) of the biopharmaceutics classification system.An additional advantage of SNEDDS over simple oily solutions is that they provide the large interfacial area for partitioning of the drug.For drugs subject to dissolution rate limited absorption, SNEDDS may offer an improvisation in both the rate of absorption and reproducibility of plasma concentration profiles 18 .SNEDDS are usually formulated as the liquid and/or in liquid forms or they are encapsulated in soft gelatin capsules 19 .However, to enhance the physical stability on longterm storage and to minimize the disadvantages associated with liquid SNEDDS such as incompatibility problems with capsule shells 19 , low drug portability, drug leakage and precipitation, liquid SNEDDS can further be formulated into solid SNEDDS.

Materials and methods
Embelin was purchased from Indofine chemical company, Inc, USA.Gliclazide sample was kindly gifted by Ranbaxy laboratories Gurgaon.Capmul ® MCM was the generous gift of Abitec Corporation, NEUSILIN ® UFL2 was provided by Fuji Chemicals-Gangwal Chemicals, Mumbai, India.Castor oil, olive oil, Propylene glycol, PEG 400, Tween 20, Tween 60, Tween 80were purchased from HimediaPvt. Ltd.Mumbai,India.Oleic acid and coconut oil were purchased from LobaChemiePvt. Ltd.Mumbai, India.Cremophor EL, Avicel ® PH-200,Kolliphor ® HS15 were purchased from Sigma Aldrich, USA.Hydrochloric acid, potassium chloride, potassium dihydrogenphosphate, disodium hydrogen phosphate, sodium chloride,sodium hydroxide, Lactose monohydrate were purchased from Central drug house, Pvt.Ltd, New Delhi, India.Sodium Starch glycolate and aerosil ® fumed silca were purchased from Ind. Swift Laboratories Pvt.Ltd, Himachal Pradesh, India.All chemicals were of analytical grade and directly used without any further purification.
Pseudo-ternary phase diagram was prepared by using chemix software 5 trial version having the triangular format which has three coordinates (Figure 1).Each coordinate represents one component of emulsion system viz.(1) Oil phase (2) Surfactantcosurfactant SA-Cos ratio phase and (3) Aqueous phase.Each coordinate represents 0 to 100% concentration for each phaseat the increment of 10%.Further, water titration method was used to construct pseudoternary phase diagrams, because this method is easy and scalable.In this study, blank (without drugs) SNEDDS were prepared to find the area of the particular component system.The surfactant was blended with co-surfactant in fixed weight ratios of (1:1, 2:1, 3:1, and 4:1) based on earlier reports 20 .Aliquots of each surfactant and co-surfactant mixture (Smix) were then mixed with oil at ambient temperature.For each phase diagram, the ratio of oil to the Smix was varied as (9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9(v/v)).The water was added in a drop wise manner to each oil-Smix mixture under vigorous stirring conditions.After the equilibrium was achieved, the samples were visually checked and determined as being clear emulsions and/or as gels.Preparation of optimize dembelin and gliclazide loaded liquid SNEDDS were prepared by using the ratio of oil-Smix and pseudo-ternary phase diagram was constructed according to the procedure mentioned elsewhere 20 .Briefly, the embelin and gliclazide were dissolved in surfactant followed by addition of co-surfactant and oil in a beaker.The resultant mixtures were continuously agitated by magnetic stirrer at 400-800rpm and heated at 40°C to obtain a homogenous solution.Different batches of SNEDDS containing embelin and gliclazide were prepared and optimization was done on the basis of emulsification time, particle size, polydispersity index, and zeta potential.while zeta potential is based on the electrophoresis and electrical conductivity of the sample.The morphology of the SNEDDS was observed using transmission electron microscope (TEM) attached to a mega view II digital camera (H 7500, Hitachi, Tokyo, Japan).A drop of sample diluted with water was placed on a copper grid and the excess was drawn off using filter paper.For staining the nanoparticles, 1% of phosphotungstic acid was dropped on freshly nanoparticle loaded TEM copper grid.Further on, this TEM grid was dried in vacuum for future analyses.
The image was magnified and focused on a layer of photographic film (Figure 2).The melting point of the drug was determined using Differential Scanning Calorimetry (DSC) to determine glass transitions, crystallinity, melting point, purity of materials, phase transitions, polymorphism, etc.The plain embelin, plain gliclazide and drug-loaded SNEDDS were first weighed in a crucible, crimped and fitted in the instrument (DSC 1 STAR system; Mettler Toledo-USA).The desired gas (i.e., nitrogen) was then purged and samples analyzed using the software.
The DSC measurement was done with a sample weight of 3-5mg and the samples were heated from 0 to 250°C with a scanning speed of 10°C/min.The DSC thermographs of the drugs and SNEDDS are shown in (Figure 3-5).The optimized drug-loaded SNEDDS formulations were subjected to stability study for a period of two months at room temperature and in refrigeration conditions.After two months of storage, samples withdrawn were reconstituted into nano emulsion and were subjected to test for drug content, particle size, and zetapotential.The drug release studies were conducted using liquid SNEDDS (equivalent to 3mg gliclazide and 9mg embelin) filled in size '00' hard gelatin capsules.
The in-vitro release profiles were studied using USP Dissolution Test apparatus II at 37°C with a rotation speed of 50rpm in 500ml phosphate buffer.The aliquots containing 1ml of samples were withdrawn at predetermined time intervals (i.e., after 1hrs) and filtered through 0.45μm filter.The withdrawn volume was replenished immediately with the same volume of fresh medium in order to maintain sink conditions.The amount of embelin and gliclazide released in the dissolution medium was determined using UV Spectrophotometerat 226.98 and 292.75nm.The blank SNEDDS (without drug) was processed similarly and used as a reference to avoid interference from the formulation components if any.The mean of at least three determinations was used to calculate the drug release 21  The development of diabetes was confirmed after 1 week of streptozotocin injection, the animals with fasting blood glucose level more than 200mg/dl were selected for the present study 23 .The animals were divided into six groups (n=6) and single dose of each prepared combination was administered orally.The blood samples were withdrawn from the tail after 1hrs of the study.Drug treatment was started after one week of streptozotoc in administration.The animals were fasted overnight before starting the experiment.The rats were randomly assigned to five different groups (n=6).The control and diabetic control groupreceived saline solution; standard groups received pureembelin at a dose of 30mg/kg/day and gliclazide at a dose of 10mg/kg/day in suspension form via oral canula.Furthermore, the treated groups received embelin (30mg/kg/day)+gliclazide (10mg/ kg/day) loaded SNEDDS formulations.The blood was withdrawn from the tail vein and estimated for blood serum glucose level, serum cholesterol level, and serum triglyceride levels as per the approved methods.The statistical analysis involving two groups was evaluated by means of two-way ANOVA followed by Bonferroni post-test whereas two-way ANOVA followed by Tukey post-test was used for column analysis and P values (P<0.001 and P<0.05) were considered to be significant.

Result and discussions
Self-emulsifying systems form a fine oil-water emulsion with only gentle agitation, upon their introduction into aqueous media.Surfactant and co-surfactant get preferentially adsorbed at the interface, reducing the interfacial energy as well as providing a mechanical barrier to coalescence.The decrease in the free-energy required for the emulsion formation consequently improves the thermodynamic stability of the emulsion formulation 24 .Therefore, the selection of oil or surfactant, and the mixing ratio of oil to Smixplaysa significant role in the formation of the emulsion.Screening of surfactant: co-surfactant ratio was done on the basis of pseudoternary phase diagram using water titration method.In this regard, the (Figure 1) shows the screening of different ratios of surfactant: co-surfactant and pseudoternary phase diagrams prepared for different ratios of surfactant and cosurfactantS: CoS(i.e., from 1:1, 1:2, 1:3 and 1:4).
On the basis of this pseudoternary phase diagram study, the optimized ratio of surfactant and cosurfactant i.e., Kolliphor ® HS15: PEG 400 was 2:1.The pseudoternary diagrams showed that with the increase in the surfactant concentration there is increase in the emulsifying region.The selection was totally on the basis of the region of emulsification i.e. more the emulsification region better will be the ratio.Selected ratio i.e. groups of Wistar rats (n=6).The optimization chart showed an increase in the ratio of the oil phase (Capmul ® MCM) resulted in a proportional increase in particle size, because of the simultaneous decrease in theS/CoS proportion.Increasing the S/S-Co ratio led to a decrease in mean droplet size.This could be attributed to an increased surfactant proportion relative to co-surfactant.It is well known that the addition of surfactants to the emulsion systems causes the interfacial film to stabilize and condense, while the addition of co-surfactant causes the film to expand, thus, the relative proportion of surfactant to co-surfactant has varied effects on the droplet size.
Similarly, there is a decrease in % transmittance value with increase in the concentration of the oil due to increase in globule size of the emulsion formed.
Negative zeta potential value of all the respected batches shows the presence of fatty acids in the oil phase.For oral emulsion preparations, dilatability is a very important parameter to confirm that the drug should not precipitate out on dilution in GIT.Formulation (F9) was the selected one on the basis of emulsification time, no precipitation, zeta-potential, transmittance and polydispersity index.
It is necessary to assess zeta potential of the SNEDDS as it can identify the charge of oil globules in the emulsion 25 .The increase in electrostatic repulsive forces between the globules prevents the coalescence of emulsion.On the contrary, a decrease in electrostatic repulsive forces can cause phase separation.The mean zeta potential of the emulsion obtained by diluting embelin loaded SNEDDS with distilled water was -34.35 mV.The charge on the oil globules is negative due to free fatty acid present in the oil phase 25 .The developed SNEDDS can be filled in hard gelatin capsules by commercial liquid filling equipments 26 .The morphology of the reconstituted EMB-gliclazide-SNEDDS formulation was observed using TEM (Figure 2).It reveals discrete, spherical oil globules less than 200nm in size, which was in accordance with the findings using Beckman coulter counter.As the oil globules were discrete and nonaggregated, we can state that the nanoemulsion was physically stable 27 .The melting point of gliclazide was found to be 173.3°C.The DSC of embelin exhibited two exothermic peaks at 84.80°C and 141.2°C resulting from loss of water and melting point peak.Figure 3 to5 shows the DSC results of embelin, gliclazide, and embelin-gliclazidepellets, as observed after centrifugation.The peak that was obtained in thermo gram gives the characteristic melting point of that molecule.From the Figure 5, it is clear that the SNEDDS of gliclazide and embelin all ingredients indicate no chemical interaction and/ or incompatibility between drugs and the other ingredients.However, it may be observed that peaks of embelin are missing for instance, peak at 84.80 o C, this may because water and other ingredients.The reduction in peak intensity of drugs is a consequence of less overall drug content present in SE pellets as compared to drugs alone 28 .
The optimized batch of SNEDDS formulation was kept for stability at refrigerated and ambient temperature.Stability study was designed to observe the resistance of nanoemulsion from coalescence and phase separation when a critical gravitational force is applied (7500 to 10,000 rpm for 10 minutes).This test also verifies the nature of the nanoemulsion, monophasic or biphasic system.No phase separation was observed by centrifugation even at 10,000 rpm for 10 minutes.

Conclusion
The optimized formulations of the embelin and gliclazide liquid SNEDDS was successfully developed in our study.The percent potency of embelin and gliclazide in liquid SNEDDS was significantly increased when compared to pure drugs.Thus, the present study proved the significant potentials of liquid SNEDDS in enhancing the dissolution rate and solubility of embelin and gliclazide.Embelin (30mg/ kg)+gliclazide (10mg/kg) loaded SNEDDS was selected as optimized formulation as it was found to be the most effective combination in reversing streptozotocin induced hyperglycaemia as compared to the pureembelin and gliclazide.The enhanced results of optimized formulation were produced because embelin and gliclazide administration to diabetic rats cause a highly significant decline in the blood glycatedhemoglobin, serum glucose levels, and nitric oxide activity.This can be attributed toa concomitant increase in the serum insulin level and regeneration of islet cells by embelin treatment.