Instantaneous enteric nano-encapsulation of omeprazole: Pharmaceutical and pharmacological evaluation

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    International Journal of Pharmaceutics xxx (2014) xxxxxx

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    IJP 14015 18

    Contents lists available at ScienceDirect

    International Journa

    journal homepage: www.elsEnteric nanocapsulesOmeprazoleHydroxypropyl methylcellulose phthalateIn vivo antiulcer activity

    optimized formulation. The highest desirability value was 0.7463 for formula E3 (containing 200 mghydroxypropyl methylcellulose phthalate (HPMCP)). The stability of omeprazole was reected by theabsence of the exothermal peak when the drug was encapsulated as detected by differential scanningcalorimetry (DSC) thermograms. In vitro drug release study conrmed the USP specications required tomeet the key formulation characteristics of gastro-resistance. In vivo pharmacological assessmentshowed that the optimized nanocapsules were able to protect rat stomach against ulcer formationcompared to the aqueous suspension of the drug which showed less signicant protection.

    2014 Published by Elsevier B.V.

    1. Introduction

    Research in nanotechnology has powerfully increased in thelast decades. Many colloidal carriers, such as liposomes(Gregoriadis, 1995), niosomes (Rajera et al., 2011), nanoemulsions(Tiwari and Amiji, 2006) and nanoparticles (Agnihotri et al., 2004)have been extensively investigated for drug delivery.

    The main advantages of nanoparticles are biocompatibility andbiodegradability, control of the drug release, increase of drugselectivity and effectiveness, improvement of drug bioavailabilityand decrease of drug toxicity and the ability to target specictissues (Malam et al., 2009). Polymeric nanoparticles are namednanocapsules, when they contain a polymeric wall and an oil core(Jager et al., 2007), where the core acts as a liquid reservoir forseveral molecules or drugs, and the wall as a protective membrane.They have special use for encapsulating and delivering hydropho-bic drugs (Sanchez-Moreno et al., 2012). The versatility of thesenanocapsules for an efcient encapsulation in their oily core ofseveral anti-cancer drugs has been previously demonstrated(Beduneau et al., 2007).

    Omeprazole, a substituted benzimidazole, is a powerfulinhibitor of gastric acid secretion in man probably without adirect effect on pepsin secretion (Festen et al., 1986). It acts by non-competitive inhibition of parietal cell H+/K+-ATPase (Felleniuset al., 1981). Omeprazole has a half-life of less than 1 h and isalmost entirely cleared from plasma within 34 h. Omeprazole ismetabolized in the liver. The two major plasma metabolites aresulphone and hydroxyomeprazole, neither of which contributes tothe antisecretory activity (Cederberg et al., 1989). Omeprazoleseems to be well absorbed from the gastrointestinal tract (GIT).However, its oral bioavailability in humans is about 4050% due toa marked rst-pass metabolism before entering the systemiccirculation (Watanabe et al., 1994). Omeprazole is widely used indoses of 2080 mg in treatment of duodenal and gastric ulcers,reux oesophagitis and in the ZollingerEllison Syndrome (Clissoldand Campoli-Richards, 1986; Watanabe et al., 1994).

    Omeprazole is sensitive to heat, humidity, light, and organicsolvents (Turkoglu et al., 2004). It degrades rapidly in acidsolutions (Quercia et al., 1997). To prevent acid degradation instomach, the drug is formulated as enteric-coated formulationssuch as enteric coated granules (Andersson et al., 1991) andenteric-coated tablets and capsules (Thomson et al., 1997).Differences in the quality of the granules coating are a potentiallimiting factor of the in vivo performance of the tested

    * Corresponding author. Tel.: +20 225311260/22835173; fax: +20 223628426.E-mail address: ihabrasmy@gmail.com (E.R. Bendas).

    http://dx.doi.org/10.1016/j.ijpharm.2014.04.0300378-5173/ 2014 Published by Elsevier B.V.Pharmaceutical nanotechology

    Instantaneous enteric nano-encapsulatiPharmaceutical and pharmacological ev

    Ehab R. Bendas *, Aly A. AbdelbaryDepartment of Pharmaceutics, Faculty of Pharmacy, Cairo University, Kasr El-Ainy Street,

    A R T I C L E I N F O

    Article history:Received 11 February 2014Received in revised form 10 April 2014Accepted 14 April 2014Available online xxx

    Keywords:

    A B S T R A C T

    Recently, great attention hpromising applications as coating technique basedinnovative enteric nanocaand amount of the entericand encapsulation efcien2131 factorial design wPlease cite this article in press as: Bendas, E.R., Abdelbary, A.A., Instantanepharmacological evaluation, Int J Pharmaceut (2014), http://dx.doi.org/1 of omeprazole:uation

    11562, Egypt

    een paid to nanocapsules. The interest of these structures is due to theirg delivery systems. The objective of this study was to develop novel enteric

    instantaneous encapsulation of the acid-labile drug, omeprazole ines. Omeprazole enteric nanocapsules were formulated by varying the typeymer. The particle size (PS), polydispersity index (PDI), zeta potential (ZP)(EE) values of the prepared enteric nanocapsules were determined. A fullsed for planning and analysis of the experimental trials to select the

    l of Pharmaceutics

    ev ier .com/locate / i jpharmous enteric nano-encapsulation of omeprazole: Pharmaceutical and0.1016/j.ijpharm.2014.04.030

  • 49 fo50 pr51 po52 or53 on54 th55 va56 th57 ex58 (R59 as60 tic61 of62 an63 pa64 la65 th66 dr67

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    106Zetasizer Nano ZS-90 instrument (Malvern Instruments, Worces-107tershire, UK) after suitable dilution with distilled water. The108measurements were conducted in triplicate. The average size of109the nanoparticles was expressed as a median diameter (Dv50),110which is particle diameter at 50% cumulative volume. The111polydispersity index was also determined. The particles surface112charge was quantied as zeta potential (z) using a Zetasizer Nano113ZS-90 instrument (Malvern Instruments, Worcestershire, UK).114Measurements were also performed after suitable dilution with115distilled water and were conducted in triplicate.

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    2 E.R. Bendas, A.A. Abdelbary / International Journal of Pharmaceutics xxx (2014) xxxxxx

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    IJP 14015 18rmulations. It was found that omeprazole degradation is moreonounced in aqueous polymer dispersions than in organiclymer solutions (Riedel and Leopold, 2005). The inuence ofganic polymer solutions on the stability of omeprazole depends

    the amount of acidic groups in the polymeric structure, wherease inuence of aqueous polymer dispersions depends on the pHlue of the dispersion. However, there are several concerns overe use of organic solvents, which usually are toxic, ammable, andplosive in addition to, the ecological and the economic problemsafati et al., 2006). Also there are still some potential problemssociated with the use of the aqueous dispersions in pharmaceu-al coating, comprising microbial contamination, the instability

    the dispersions or the active ingredient, long processing timed adjusting optimal processing conditions. These criticalrameters can cause a non-uniformity of the applied coatingyer and up-scaling problems (Mehuys et al., 2005). To overcomee limitations of aqueous coating and to reduce process time, ay coating method was developed (Obara et al., 1999).The aim of this study was to develop novel enteric coatingchnique based on instantaneous encapsulation of the chemicallybile drug, omeprazole in innovative enteric nanocapsules andd optimal production parameters for a stable, highly concen-ated omeprazole formulation. Moreover, the pharmacologicalfects of the omeprazole enteric nanocapsules were evaluated by

    in vivo antiulcer study using Wistar male rats.

    Materials

    Omeprazole was kindly provided by Aventis Pharma, Cairo,ypt. Lecithin and Pluronic F68 were purchased from Sigmaemical Co. (St. Louis, MO, USA). Hydroxypropyl methylcellulosethalate (HPMCP) was purchased from Samsung Fine Chemicals. (Seoul, Korea). Polyvinyl acetate phthalate (PVAP) was obtainedm Colorcon (West Point, PA, USA). Miglyol1 812 was supplied bysol Germany GmbH (Germany). Sodium bicarbonate wastained from Wako Pure Chemical Industries, Ltd. (Osaka, Japan).solute ethanol, acetone and acetonitrile (HPLC grade) wererchased from Fisher Scientic Co. (Pittsburgh, PA, USA). All otheremicals were of analytical grade.

    Methods

    . Preparation of omeprazole enteric nanocapsules

    Omeprazole enteric nanocapsules were prepared according toe following procedures: 20 mg of omeprazole, 50 mg of lecithind different amounts of enteric polymers (HPMCP or PVAP) weressolved into a mixture of 2.5 mL of ethanol and 12.0 mL ofetone and then 315 mL of Miglyol1 812 was added. Immediatelyter that, this organic phase was poured into 25 mL of aqueouslution containing 62.5 mg of Pluronic F68 and 50.0 mg of sodiumcarbonate. Instantly upon addition of the organic phase into theueous solution, it turned milky. The milky mixture wasaporated under reduced pressure, in a rotary evaporatorotavapor, Type R 110, Bchi, Switzerland) at 45 C for 15 min

    a nal volume of 20 mL. The nanocapsules formulae containingMCP were coded (E1E3) while those containing PVAP wereded (E4E6).

    2. Characterization of enteric nanocapsules

    2.1. Particle size and zeta potentialThe particle size of omeprazole enteric nanocapsules waseasured by photon correlation spectroscopy (PCS) using aPlease cite this article in press as: Bendas, E.R., Abdelbary, A.A., Instantanpharmacological evaluation, Int J Pharmaceut (2014), http://dx.doi.org3.2.2. Drug encapsulation efciency (EE)The encapsulation efciency (EE) of omeprazole was deter-

    mined indirectly by calculating the difference between the totalamount of omeprazole added in the formulation and thatremaining in the aqueous medium after separating the entericnanocapsules by ultracentrifugation at 14,000 rpm for 1 h at 4 Cusing cooling ultracentrifuge (Model 8880, Centurion ScienticLtd., W. Sussex, UK). Omeprazole contents were determined by anaccurate validated HPLC method. Encapsulation efciency wascalculated using the equation:

    EE Drug content in nanocapsulesDrug amount used

    100 (1)

    3.3. HPLC determination of omeprazole

    An isocratic HPLC method was employed for the quanticationof omeprazole (Nataraj et al., 2012). A Thermo Separation HPLCsystem (Fremont, California) equipped with a P4000 pump unit, anAS3000 autosampler including an injection valve with a sampleloop of 50 mL volume, and a UV2000 detector was used. A ZorbaxExtend-C18 column (4.6 mm 250 mm) containing 3.5 mm sizeadsorbent as stationary phase (Agilent Technologies, Santa Clara,California) was used. The column was maintained at roomtemperature (25.0 2.0 C). The mobile phase consisted of amixture of phosphate buffer (pH 7.4) and acetonitrile (60:40 v/v).The ow rate and the UV detector were set at 1.0 mL/min and302 nm, respectively. Omeprazole was eluted at 6.3 min underthese conditions. An external calibration curve was established inthe range of 1070 mg/mL. The assay procedures were validated interms of linearity, precision, and accuracy.

    3.4. Optimization using statistical design

    For systematic optimization of enteric nanocapsules formulae,full factorial experimental design methodology was employedwith Design-Expert1 software (Version 7, Stat-Ease Inc., MN) toinvestigate the effect of formulation variables on enteric nano-capsules properties (Table 1). Two independent variables wereevaluated which were: type (X1) and amount (X2) of the polymer.The particle size (Y1: PS), polydispersity index (Y2: PDI), zetapotential (Y3: ZP) and encapsulation efciency (Y4: EE) were

    Table 1Full factorial design for optimization of the enteric nanocapsules formulae.

    Factors (independent variables) Levels

    X1: type of polymer HPMCP PVAPX2: amount of polymer (mg) 50 100 200

    Responses (dependent variables) ConstraintsY1: particle size (nm) MinimizeY2: polydispersity index MinimizeY3: zeta potential (mV) Maximize (least negativity)Y4: encapsulation efciency (%) Maximizeeous enteric nano-encapsulation of omeprazole: Pharmaceutical and/10.1016/j.ijpharm.2014.04.030

  • 151 selected as the dependent variables. Desirability was calculated for152 selection of the optimized formula which was subjected for further153 investigations.

    154 3.5. Freeze drying of enteric nanocapsules

    155 In order to study the in vitro dissolution and the physical156 characters of the optimized formulation, the omeprazole enteric157 nanocapsules formula (E3) was lyophilized after preparation. The158

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    196through 0.1 mm PTFE syringe lter (Whatman Inc., Clifton, NJ, USA)197and analyzed according to HPLC procedures described earlier.

    1983.9. In vivo antiulcer activity

    199The in vivo antiulcer activity of the optimized omeprazole200enteric nanocapsules formula (E3) was carried out using Wistar201male rats. The protocol for in vivo antiulcer activity was approved202by the ethical committee of Faculty of Pharmacy, Cairo University.203

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    E.R. Bendas, A.A. Abdelbary / International Journal of Pharmaceutics xxx (2014) xxxxxx 3

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    IJP 14015 18lyophilization was done after separation of the enteric nano-capsules by ultracentrifugation at 14,000 rpm for 1 h at 4 C. Theconditions applied during this step were: freezing for 12 h at20 C and sublimation at 15 C and 100 mbar for 12 h using aFlexi-DryTM MP Freeze Dryer (SP Scientic, Stone Ridge, NY), andnally the secondary drying was carried out at 25 C and 50 mbarfor 6 h.

    3.6. Transmission electron microscopy (TEM)

    The particle morphology of the optimized enteric nanocapsulesformula (E3) was examined using TEM (H-600, Hitachi, Japan). Thesample was dropped on coppergold carbon grid and allowed todry. The grid was then mounted in the instrument and photo-graphs were taken at different magnications (Thakkar et al.,2011).

    3.7. Differential scanning calorimetry (DSC)

    Thermograms of optimized omeprazole enteric nanocapsulesformula (E3), HPMCP, Pluronic F68, sodium bicarbonate andomeprazole were recorded on a DSC-60 (Shimadzu, Kyoto, Japan).Samples (5 mg) were placed in aluminum pans, and the lids werecrimped using a Shimadzu crimper. Thermal behavior of thesamples was investigated at a scanning rate of 10 C/min andcovering temperature range of 20300 C. The instrument wascalibrated with an indium standard.

    3.8. In vitro drug release

    Drug-release study was implemented to conrm the USPspecications required to meet the ke...

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