DEVELOPMENT OF SOLID LIPID NANOPARTICLES OF A WATER SOLUBLE DRUG

Page4813 Indo American Journal of Pharmaceutical Research, 2016 ISSN NO: 2231-6876 DEVELOPMENT OF SOLID LIPID NANOPARTICLES OF A WATER SOLUBLE DRUG Akkshata Parab*, Amrita Bajaj Department of Pharmaceutics, SVKM s Dr. Bhanuben Nanavati College of Pharmacy, Vile Parle (West), Mumbai - 400 056, India. ARTICLE INFO Article history Received 23/02/2016 Available online 31/03/2016 Keywords Solid Lipid Nanoparticles, Solvent Evaporation, High Pressure Homogenization. ABSTRACT This study was done to optimize and evaluate Tramadol hydrochloride loaded Solid Lipid Nanoparticles by using particle size and zeta potential analysis, Differential scanning calorimetry and Scanning electron microscopy. Tramadol hydrochloride was obtained as a gift sample from Indeus Life Sciences. Precirol ATO 5 and Compritol 888 ATO was obtained from Gattefosse Ltd. Stearic acid, Glyceryl mono stearate self emulsifying, chloroform, ethanol, isopropyl alcohol, Tween80, Poloxamer 188 were also used for the formulation of solid lipid nanoparticles (SLN). Attempts were made to optimize SLN by Solvent evaporation method. The solid lipid nanoparticles were successfully formulated which were in the size range of 300-400nm with zeta potential between -20 to -30mV. The SLN exhibited circular structure with better encapsulation efficiency. Compatibility between the drug and excipients was confirmed by Differential scanning calorimetry. Solid lipid nanoparticles of Tramadol hydrochloride with sufficient drug content can be a promising approach in context to formulation of topical gels and creams. Corresponding author Akkshata Parab Department of Pharmaceutics, SVKM s Dr. Bhanuben Nanavati College of Pharmacy, Vile Parle (West), Mumbai - 400 056, India. akkshataparab@gmail.com Please cite this article in press as Akkshata Parab et al. Development of Solid Lipid Nanoparticles of A Water Soluble Drug. Indo American Journal of Pharmaceutical Research.2016:6(03). Copy right 2016 This is an Open Access article distributed under the terms of the Indo American journal of Pharmaceutical Research, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Page4814 INTRODUCTION During the last few decade lipids have gained large interest as carriers for the delivery of both, poorly water soluble as well as water soluble drugs. The availability of novel lipid excipients with acceptable regulatory and safety profiles coupled with their ability to enhance oral bioavailability has helped in the development of lipid based formulations as a means for drug delivery [1]. The absorption of drug from lipid based nanoformulations depends on various factors, including particle size, degree of emulsification, rate of dispersion and potential precipitation of drug upon dispersion. Generally, most lipid drug delivery systems used as solid lipid nanocarriers have high stability, possibility of incorporating both hydrophilic and hydrophobic substances, high carrier capacity and feasibility of variable routes of administration, including oral, parenteral, topical and pulmonary routes [2]. Solid Lipid Nanoparticles (SLN) are sub-micron colloidal carriers composed of physiological lipids, dispersed in water or in an aqueous surfactant solution [3]. The most important benefit of these carriers is their low risk of toxicity. Small size (50-1000nm) of lipid particles ensures close contact with stratum corneum, and may enhance dermal penetration of drug. SLN have distinct occlusive properties due to the formation of an intact film on the skin surface upon drying, which decreases transepidermal water loss and favors the drug penetrating through the stratum corneum. Besides the nonspecific occlusion effect, the enhanced drug penetration might be related with SLN themselves, the highly specific surface area of nanometer sized SLN facilitates the contact of encapsulated drug with stratum corneum. The nanometer sized particles can make close contact with superficial junctions of corneocyte clusters and furrows between corneocyte islands, which may favor accumulation for several hours allowing for sustained drug diffusion through the skin [4]. High shear homogenization, Hot homogenization, Cold homogenization, Ultrasonication or high speed homogenization, [5] Micro emulsion based SLN preparations, Supercritical fluid, Solvent emulsification/evaporation, Double emulsion method, Spray drying method are the various methods to prepare SLN [6]. This research was done since till date there are no marketed formulations available for topical administration of Tramadol hydrochloride, an opioid analgesic drug [7]. Tramadol hydrochloride exists only as an injectable and oral formulation, which possess various side effects and hence topical formulations may present good commercial potential. Solvent evaporation technique: The lipid phase (solid lipids viz. Precirol ATO 5/ Compritol 888 ATO/ Stearic acid/ GMS in different proportions) was dissolved in suitable solvent (chloroform/ ethanol/ isopropyl alcohol). The aqueous phase consisted of the accurately weighed quantity of drug dissolved in double distilled water and varied concentrations of hydrophilic surfactants (Tween80/ Poloxamer 188) were added to it [8]. Then, the organic phase was injected drop-wise in the aqueous phase under an over head stirrer agitated at a uniform speed for one and a half hour followed by addition of cold water (causing lipid recrystallization) to the dispersion and continued stirring for another half an hour. The dispersion was then subjected to High Pressure Homogenization (HPH) at 10,000 psi (10 cycles) for size reduction of the formed SLN. SLN dispersion containing 0.5% and 1% w/v drug were prepared and evaluated. Optimization of Tramadol hydrochloride loaded Solid Lipid Nanoparticles (SLN): Screening of Solvents: Chloroform, ethanol, Isopropyl Alcohol were evaluated for their ability to dissolve the lipid in sufficient concentrations in order to facilitate formation of SLN. 0.02 g of each lipid i.e Stearic acid, Glyceryl Monostearate, Precirol ATO 5 and Compritol 888 were put in 5 ml of each of the solvents stated above and was vigorously shaken and observed for clarity (i.e solubility of the lipid in the solvent). The results are given in Table 1.7. Screening of various lipids: Lipids like Stearic acid, Glyceryl Monostearate SE, Precirol ATO 5 and Compritol 888 ATO were explored for their capacity to form Solid lipid nanoparticles with the drug. Combinations of two lipids were screened at various ratios. Table 1.1: Formulations F1, F2, F3 prepared by using Precirol ATO 5 + GMS-SE at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F1 F2 F3 DRUG 0.5 0.5 0.5 COMPRITOL 888 ATO - - - PRECIROL ATO 5 0.5 0.5 1 STEARIC ACID - - - GMS-SE 0.5 1 0.5 TWEEN 80 1.0 1.0 1.0 POLOXAMER 188 - - - CHLOROFORM 25 25 25

Page4815 Table 1.2: Formulations F4, F5, F6 prepared by using Stearic acid + GMS-SE at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F4 F5 F6 DRUG 0.5 0.5 0.5 COMPRITOL 888 ATO - - - PRECIROL ATO 5 - - - STEARIC ACID 0.5 0.5 1 GMS-SE 0.5 1 0.5 TWEEN 80 1.0 1.0 1.0 POLOXAMER 188 - - - CHLOROFORM 25 25 25 Table 1.3: Formulations F7, F8, F9 prepared by using Precirol ATO 5 + Compritol 888 ATO at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F7 F8 F9 DRUG 0.5 0.5 0.5 COMPRITOL 888 ATO 0.5 1 0.5 PRECIROL ATO 5 0.5 0.5 1 STEARIC ACID - - - GMS-SE - - - TWEEN 80 1.0 1.0 1.0 POLOXAMER 188 - - - CHLOROFORM 25 25 25 Lipids were selected depending on assessment of colloidal appearance, entrapment efficiency and particle size of the SLN formulations. The results are given in Table 1.8 to 1.10. Screening of surfactants: Tween 80 and Poloxamer 188 were screened for their surfactant properties in order to obtain a nano sized system of solid lipid Nanoparticles with high drug loading. Different concentrations of the surfactants were explored. Table 1.4: Formulations F10, F11, F12 prepared by using Tween 80 in different concentrations, where Precirol ATO 5 + Compritol 888 ATO (1:1), and drug (0.5%) were kept constant. F10 F11 F12 DRUG 0.5 0.5 0.5 COMPRITOL 888 ATO 0.5 0.5 0.5 PRECIROL ATO 5 0.5 0.5 0.5 STEARIC ACID - - - GMS-SE - - - TWEEN 80 0.5 1.0 1.25 POLOXAMER 188 - - - CHLOROFORM 25 25 25 Table 1.5: Formulations F13, F14, F15 prepared by using Poloxamer 188 in different concentrations, where Precirol ATO 5 + Compritol 888 ATO (1:1), and drug (0.5%) were kept constant. F13 F14 F15 DRUG 0.5 0.5 0.5 COMPRITOL 888 ATO 0.5 0.5 0.5 PRECIROL ATO 5 0.5 0.5 0.5 STEARIC ACID - - - GMS-SE - - - TWEEN 80 - - - POLOXAMER 188 0.5 1.0 1.25 CHLOROFORM 25 25 25

Page4816 The optimum concentration of one of the surfactant was selected on assessment of colloidal appearance, entrapment efficiency and particle size of the SLN formulations. The results are given in Table 1.11 and 1.12. Screening different concentrations of drug: Tramadol hydrochloride was also varied in concentrations (0.5% w/w and 1% w/w) and evaluated for SLN formation. Table 1.6: Formulation F16 and F17 prepared by loading different concentrations of drug, where Precirol ATO 5 + Compritol 888 ATO (1:1) and Tween (1%) were kept constant. F16 F17 DRUG 0.5 1.0 COMPRITOL 888 ATO 0.5 0.5 PRECIROL ATO 5 0.5 0.5 STEARIC ACID - - GMS-SE - - TWEEN 80 1 1 POLOXAMER 188 - - CHLOROFORM 25 25 The optimum drug concentration was selected on assessment of colloidal appearance, entrapment efficiency and particle size of the SLN formulations. The results are given in Table 1.13. The optimized formula for SLN is given in Table 1.14. Evaluation of the optimized SLN: 1. Particle size and zeta potential measurements: The average particle size and zeta potential of SLN was determined by dynamic light scattering instrument (Malvern Zetasizer, UK). Light scattering was monitored at 25 C at a scattering angle of 90. A solid state laser diode was used as light source. The sample of optimized SLN was suitably diluted with distilled water and filtered through 0.22 μm membrane filter to eliminate multi-scattering phenomena. The diluted sample was then placed in quartz couvette and subjected to particle size and zeta potential analysis. The results are given in Fig 1.5 and 1.6. 2. Morphology Studies: The morphology of the lipid particles in the SLN formulations was visualized with the Scanning Electron Microscope (SEM). The results are given in Fig 1.4. 3. Drug content: Tramadol hydrochloride content in SLN dispersion was measured by dissolving known quantity of SLN dispersion in solvent (methanol) and recording the absorbance at 272 nm using UV/VIS Spectrophotometer. 4. Compatibility Studies of Drug and Excipients by DSC: Thermal analysis of Tramadol hydrochloride and Tramadol hydrochloride loaded SLN was carried out employing Differential Scanning Calorimeter. Samples were accurately weighed into aluminium pans and sealed. All samples were run at a heating rate of 10 C/min over a temperature range 25-400 C in atmosphere of nitrogen and thermograms were obtained. The results are given in Fig. 1.1 to 1.3. RESULTS Formulation of Tramadol hydrochloride loaded Solid Lipid Nanoparticles (SLN): Screening of Solvents: Chloroform, ethanol and Isopropyl Alcohol were evaluated for their ability to dissolve the lipid in sufficient concentrations in order to facilitate formation of SLN. Table 1.7: Observations for lipid solubility at room temperature. Lipids Ethanol Isopropyl Alcohol Chloroform Glyceryl Mono stearate Insoluble Insoluble Soluble Stearic acid Soluble Soluble Soluble Precirol ATO 5 Practically Insoluble Insoluble Freely Soluble Compritol 888 ATO Practically Insoluble Insoluble Soluble Solubility studies showed the drug was freely soluble in water and methanol and soluble in chloroform, while all the lipids were soluble in chloroform at room temperature. Hence, chloroform was selected as the solvent for preparation of SLN.

Page4817 Screening of various lipids: According to literature survey, combinations of solid lipids have been found more efficient than using a single lipid. So, combination of two different lipids were tried to formulate the solid lipid nanoparticles. Various trials were conducted using combination and ratios of lipids such as Precirol ATO 5, Glyceryl monostearate-self emulsifying (GMS-SE), Compritol 888 ATO and Stearic acid. Table 1.8: Evaluation of F1, F2, F3 prepared by using Precirol ATO 5 + GMS-SE at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F1 F2 F3 APPEARANCE Turbid Too viscous Turbid ENTRAPMENT EFFICIENCY (%) 12.40 _ 15.10 PARTICLE SIZE (IN MICRONS) _ Table 1.9: Evaluation of F4, F5, F6 prepared by using Stearic acid + GMS-SE at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F4 F5 F6 APPEARANCE Separation of the two phases Too viscous Too viscous and yellowish ENTRAPMENT EFFICIENCY (%) _ PARTICLE SIZE (IN MICRONS) _ Table 1.10: Evaluation of F7, F8, F9 prepared by using Precirol ATO 5 + Compritol 888 ATO at different ratios, where Tween 80 (1%) and drug (0.5%) were kept constant. F7 F8 F9 APPEARANCE Colloidal dispersion with a bluish tinge Colloidal dispersion Colloidal dispersion ENTRAPMENT EFFICIENCY (%) 59.41 42.11 37.28 PARTICLE SIZE (IN MICRONS) 1.2 1.4 1.5 Formulations F1, F2 and F3 consisting of Precirol ATO 5 and GMS-SE showed turbidity and SLN obtained were highly viscous which was not desirable. Also, entrapment efficiency was too low. Hence, this combination was not selected. Formulation F4, F5 and F6 consisting of Stearic acid and GMS-SE did not form SLN since separation of the lipid and aqueous phase was observed. Formulation F7, F8 and F9 consisting of Precirol ATO 5 and Compritol 888 ATO showed good SLN formulations as colloidal dispersions were obtained. Out of the three formulations, formulation F7 (ratio 1:1 of the lipids) showed the highest entrapment efficiency i.e. 59.41% and uniform particle size of 1.1 1.3 microns was obtained in Motic microscope. Thus, on the basis of colloidal appearance, entrapment efficiency and particle size, formulation F7 consisting of Precirol ATO 5 and Compritol 888 ATO in the ratio of 1:1 was selected. Evaluation of formulations for selection of suitable surfactant Formulation of SLN requires suitable surfactant to reduce the interfacial tension between the lipid and aqueous phase. Thus, surfactants like Tween 80 and Poloxamer 188 in different concentrations were screened for selection of a suitable one. Table 1.11: Evaluation of F10, F11, F12 prepared by using Tween 80 in different concentrations, where Precirol ATO 5 + Compritol 888 ATO (1:1), and drug (0.5%) were kept constant. F10 (0.5%) F11 (1%) F12 (1.25%) APPEARANCE Separation of the two phases Colloidal dispersion Colloidal dispersion ENTRAPMENT EFFICIENCY (%) _ 64.45 58.92 PARTICLE SIZE (IN MICRONS) _ 1.1 1.3

Page4818 Table 1.12: Evaluation of F13, F14, F15 prepared by using Poloxamer 188 in different concentrations, where Precirol ATO 5 + Compritol 888 ATO (1:1), and drug (0.5%) were kept constant. F13 (0.5%) F14 (1%) F15 (1.25%) APPEARANCE Separation of the two phases Separation of the two phases Colloidal dispersion ENTRAPMENT EFFICIENCY (%) 32.12 PARTICLE SIZE (IN MICRONS) 2.1 Formulation F10 having Tween 80 in the concentration of 0.5% w/v was not able to form SLN as separation of the lipid and aqueous phase was observed. It indicated that 0.5% w/v concentration of surfactant was insufficient to reduce the interfacial tension to form SLN. Formulation F11 and F12 having Tween 80 in the concentration of 1 and 1.25% w/v formed colloidal dispersion as desired. Out of the two formulations, F11 having 1% w/v of Tween 80 gave higher entrapment efficiency i.e. 64.45% than F12. Formulation F13 and F14 having Poloxamer 188 in the concentration of 0.5 and 1% w/v was not able to form SLN as separation of the lipid and aqueous phase was observed. Formulation F15 having Poloxamer 188 in the concentration of 1.25% w/v formed colloidal dispersion as desired but entrapment efficiency was low. Thus, on the basis of colloidal appearance, entrapment efficiency and particle size, formulation F11 consisting Tween 80 in the concentration of 1% w/v was selected as the hydrophilic surfactant for the formulation of SLN. Selection of concentration of drug Optimum drug concentration is necessary for the required analgesic activity. Therefore, different concentrations i.e. 0.5% and 1% w/v were prepared, observed and evaluated. Table 1.13: Evaluation of F16 and F17 prepared by loading different concentrations of drug, where Precirol ATO 5 + Compritol 888 ATO (1:1) and Tween (1%) were kept constant. F16 F17 APPEARANCE Colloidal dispersion Precipitation of the drug ENTRAPMENT EFFICIENCY (%) 66.12 _ PARTICLE SIZE (IN MICRONS) 1.2 _ Formulation F17 consisting of 1% w/v of drug showed precipitation of the drug. Thus, it was concluded that 1% concentration of drug was too high. Formulation F16 consisting of 0.5% w/v of drug formed colloidal dispersion with uniform particle size of 1.2 microns as desired. The entrapment efficiency was 66.12% which was quite good. Thus, on the basis of colloidal appearance, entrapment efficiency and particle size, formulation F16 having 0.5%w/v of drug concentration was selected for SLN formulation and it was taken for further evaluation. Thus, the optimized formula for SLN formulation is: Table 1.14: Optimized formula for SLN. Sr. No. Qty (%w/w) 1 Tramadol hydrochloride 0.5% 2 Precirol ATO 5 0.5% 3 Compritol 888 ATO 0.5% 4 Tween 80 1% 5 Chloroform 25% 6 Purified water q.s. to 100ml Procedure for SLN formulation: The solid lipids, Precirol ATO 5 and Compritol 888 ATO (in the ratio of 1:1) were accurately weighed and dissolved in chloroform at room temperature by shaking manually. The aqueous phase included accurately weighed drug and Tween 80 dissolved in measured quantity of purified water.

Page4819 DSC mw DDSC mw/min DSC mw DDSC mw/min DSC mw DDSC mw/min The organic phase was injected dropwise into the aqueous phase under an over head stirrer with constant rotation at 500rpm for one and a half hour to form the primary emulsion. Measured quantity of chilled water was then added to the primary emulsion with constant stirring for another half an hour for recrystallization of the lipids to form SLN dispersion. This formed dispersion was then subjected to High Pressure Homogenization at 10,000 psi pressure and ten cycles. SLN dispersion was then evaluated for physicochemical parameters and in vitro diffusion studies. Results of evaluation of the optimized Solid Lipid Nanoparticles: Compatibility Studies of Drug and Excipients by DSC: Drug-excipients compatibility studies were investigated using Differential scanning calorimetry. In Differential Scanning Calorimetry, any drastic changes in the formulation with the thermal behavior of either the drug or the excipients are visualized. It is a thermodynamic technique where the sample and reference material are subjected to a controlled temperature programme and the difference in energy inputs between the sample and reference material is measured as a function of temperature. Both the sample and reference are maintained at the same temperature throughout the experiment. The temperature programme for DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. 50.00 40.00 30.00 20.00 10.00 0.00-10.00-20.00-30.00-40.00-50.00 186.0Cel -40.12mW 274.1Cel -35.63mW 50.0 100.0 150.0 Temp Cel 200.0 250.0 Fig.1.1: DSC graph of pure API. 25.00 60.00 20.00 15.00 40.00 10.00 20.00 5.00 0.00 0.00-5.00-10.00-20.00-15.00-40.00-20.00-25.00-30.00 50.0 100.0 110.5Cel -26.84mW 150.0 Temp Cel 200.0 250.0-60.00 50.0 100.0 108.9Cel -59.19mW 150.0 Temp Cel 200.0 250.0 Fig.1.2: DSC graph of blank formulation (Solid Lipid Nanoparticles) Fig.1.3: DSC graph of formulation (Solid Lipid Nanoparticles). It is indicated from thermograms that well characterized and recognizable endotherms appeared at the temperature of 186.0 C for Tramadol hydrochloride. DSC thermograms of the excipients used for formulation of SLN and blank SLN were far from the endotherm of Tramadol hydrochloride indicating that there is no interference between drug and excipients used in SLN based gel formulation. It is obvious from DSC thermograms that there is no significant shift in the endothermic peaks, hence it can be concluded that there is no interaction between drug and excipients.

Page4820 Morphology: Scanning Electron Microscopy (SEM) is the most important technique for the study of nanostructures of SLN because it directly produces images at high resolution and it can capture any co-existent structure and nano-structural transitions. SEM image is indicative of morphology of the nanoparticles. Fig.1.4: SEM image of optimized SLN dispersion. The particles of optimized dispersions were spherical in shape and in the size range of 300 350 nm. Particle size: All the particles were in the range of 250 to 350 nm which indicated the suitability of formulation for topical drug delivery. Polydispersity index signifies the uniformity of particle size within the formulation. PDI is a measure of particle homogeneity. If PDI value is closer to 0, it indicates narrow size distribution of the particles. PDI of optimized dispersion was 0.39 which indicated prepared dispersion is monodisperse and will remain stable. Fig.1.5: Particle size graph of optimized SLN batch obtained in Malvern zetasizer. Zeta potential: Zeta potential is an important parameter for prediction of stability. Because of the presence of fatty acids in the structure of the excipients used, generally the surface charge of the particles is negative. Zeta potential of the formulations was -21.43 mv, indicating negative charge of the particles which prevents aggregration of the particles.

Page4821 Fig.1.6: Zeta potential graph of optimized SLN batch obtained in Malvern zetasizer. Entrapment efficiency: Entrapment efficiency of prepared SLN dispersions was found to be within 59.14±0.54% - 68.08±0.91% which indicates good drug loading capacity of the formulation. DISCUSSION In the present study, an attempt was made to formulate solid lipid nanoparticles of Tramadol hydrochloride, a highly water soluble drug which can be used further to prepare topical dosage forms such as gels. The SLN dispersion was prepared by solvent evaporation technique using Precirol ATO 5 and Compritol 888 ATO as lipid matrix. The prepared SLN dispersions were characterized for various parameters such as particle size and zeta potential and its result indicated narrow particle size distribution and steric stability. Entrapment efficiency results assured good loading capacity. Formulation was also characterized for Scanning Electron Microscopy to determine morphology of particles. Thus, it was seen that SLN of good drug content can be formulated and it can serve as a future prospective for site-specific topical delivery such as gels and creams. ACKNOWLEDGEMENTS I am thankful to Indeus Life Sciences Pvt Ltd. and Gattefosse Ltd. for providing me with gift samples of drugs and solid lipids respectively. My heartfelt thanks to R.C. Patel College of Pharmacy, Shirpur for carrying out particle size analysis; Bharati Vidyapeeth College of Pharmacy, Belapur for doing the DSC studies and Diya Labs, Airoli for carrying out the SEM studies. List of abbreviations: SLN : Solid Lipid Nanoparticles DSC : Differential Scanning Calorimetry SEM : Scanning Electron Microscopy PDI : Poly Dispersity Index API : Active Pharmaceutical Ingredient HPH : High Pressure Homogenization Conflict of interests: None.

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