Applied Clay Science 80–81 (2013) 85–92

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Research paper

Clay–polymer nanocomposites as a novel drug carrier: Synthesis,characterization and controlled release study ofPropranolol Hydrochloride

Seema, Monika Datta ⁎Analytical Research Laboratory, Department of Chemistry, University of Delhi, Delhi 110007, India

⁎ Corresponding author. Tel.: +91 9811487825; fax:E-mail address: monikadatta_chem@yahoo.co.in (M

0169-1317/$ – see front matter © 2013 Elsevier B.V. Allhttp://dx.doi.org/10.1016/j.clay.2013.06.009

a b s t r a c t

a r t i c l e i n f o

Article history:Received 25 May 2012Received in revised form 17 May 2013Accepted 1 June 2013Available online 10 July 2013

Keywords:Clay–polymer nanocomposites,MontmorilloniteControlled drug deliveryAntihypertensive drug

Short half life of Propranolol Hydrochloride (PPN), an antihypertensive drug is a prime requirement to devel-op a formulation which could extend the release of PPN in the human body and also eliminate daily multipledosage of PPN. In this study, a system of PPN loaded Montmorillonite–Poly lactic-co-glycolic acid (Mt–PLGA)nanocomposites has been developed. PPN incorporated PLGA nanoparticles have been compared withMt–PPN–PLGA nanocomposites. Mtwas used as sustained release carrier for PPNwith addition of biodegradablepolymer PLGA by preparing Mt–PPN–PLGA nanocomposites by double emulsion solvent evaporation method.The drug encapsulation efficiency and drug loading capacity of synthesized products were estimated withHPLC including suitable analytical techniques to confirm the formation of clay–polymer nanocomposites(CPN). The release profile of encapsulated PPN in CPN shows pH dependent release in simulated gastrointes-tinal fluid for a period of 8 h. This study suggests that the methodologies used are suitable for the synthesis ofMt based PLGA nanocomposites with high drug encapsulation efficiency and controlled drug release charac-teristics and indicates that the Mt–PPN–PLGA nanocomposites are supposed to be better oral controlled drugdelivery system, for a highly hydrophilic low molecular weight antihypertensive drug PPN to minimize thedrug dosing frequency and hence improving the patient compliance.

© 2013 Elsevier B.V. All rights reserved.

1. Introduction

Drug delivery systems have been of great interest for the past fewdecades to realize the effective and controlled drug delivery and min-imize the side effects in the field of pharmaceutics. Oral controlleddrug delivery system is an essential part of the development of newmedicines. The carriers used for control drug release were mainly bio-degradable polymers (Langer et al., 1999) and porous inorganic ma-trix (Suresh et al., 2010; Aguzzi et al., 2007).

In recent years, drug intercalated smectite, especiallyMontmorillonite(Mt) pharmaceutical grade claymineral has attracted great interest of re-searchers (Joshi et al., 2009a,b).Mt has large specific surface area, exhibitsgood adsorption ability, cation exchange capacity, and drug-carrying ca-pability. Mt is hydrophilic and highly dispersible inwater and can accom-modate various protonated and hydrophilic organic molecules along the(001) planeswhich can be released in controlledmanner by replacementwith other kind of cations in the releasemedia (Bergaya et al., 2006; Chenet al., 2010; Iliescu et al., 2011). Therefore theMt is suggested to be a gooddelivery carrier of the hydrophilic drugs.Mt is a potent detoxifierwith ex-cellent adsorbent properties due to its high aspect ratio. It can adsorb ex-cess water from feces and thus act as anti-diarrhoeic. Mt can also provide

+91 11 27666605.. Datta).

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mucoadhesive capability for the nanoparticles to cross the gastrointesti-nal barrier (Dong and Feng, 2005; Feng et al., 2009). It has also beenused as a controlled release system. Mt has been proved to be nontoxicby hematological, biochemical and histopathological analyses in ratmodels (Lee et al., 2005). Mt is utilized as a sustained release carrierfor various therapeutic molecules, such as 5 Fluorouracil (Lin et al.,2002), sertraline (Nunes et al., 2007), vitamin B1 (Joshi et al., 2009a,b),promethazine chloride (Seki and Kadir, 2006) and buspiron hydrochlo-ride (Joshi et al., 2010).

Propranolol Hydrochloride [(2RS)-1-(1-Methylethyl) amino-3-(naphthalen-1-yloxy) propan-2-ol monohydrochloride] an antihyper-tensive drug is a nonselective, beta-adrenergic receptor-blocking agent(Dollery, 1991). It is a white crystalline solid, highly soluble in water.The dose of Propranolol Hydrochloride (PPN) ranges from 40 to80 mg/day. Due to shorter half life (3.9 h) the drug has to be adminis-trated 2 or 3 times daily so as to maintain adequate plasma levels ofthe drug (Chaturvedi et al., 2010). Thus, the development of controlledrelease dosage forms would clearly be advantageous (Sahoo et al.,2008). Sanghavi et al. (1998), prepared matrix tablets of PPN usinghydroxypropyl methylcellulose which exhibited first order releasekinetics. Velasco-De-Paola et al., 1999, described dissolution kinetics ofcontrolled release tablets containing PPN prepared using eudragit. Someother researchers have also formulated oral controlled release products ofPPN by various techniques (Gil et al., 2006; Mohammadi-Samani et al.,

Fig. 1. Schematic representation of clay–polymer–drug nanocomposite synthesis.

86 Seema, M. Datta / Applied Clay Science 80–81 (2013) 85–92

2000; Paker-Leggs and Neau, 2009; Patel et al., 2010; Patra et al., 2007).However, many researchers in the development of PPN sustained releasedosage forms were met with problems, such as the difficulty to controlthe release of the drug due to the high aqueous solubility of PPN.Sánchez-Martin et al. (1981) and Rojtanatanya and Pongjanyakul(2010) have reported the interaction of PPN with Mt and magnesium-aluminium-silicate mineral (MAS, a mixture of Mt and saponite) respec-tively. PPN can intercalate into the interlayer space of MAS and theobtained complexes showed control of the release of PPN.

However no report has been available in the literature for thecombination of a biodegradable polymer Poly lactic-co-glycolic acid(PLGA) and Mt for controlled release of PPN. In this study we havetried to obtain the synergism of biodegradable and biocompatible poly-merwhich has already beenwidely explored for controlled drug releaseproperties, with pharmaceutical grade Mt to produce the oral and con-trolled drug delivery formulations for PPN. Being a highly hydrophilicdrug molecule, it is very difficult to encapsulate a high amount of PPNwithin the hydrophobic polymer matrix. Therefore, in the presentstudy a modified double emulsion solvent evaporation technique hasbeen developed to entrap a substantial amount of drug in the synthe-sized formulations.

PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites wereprepared by w/o/w double emulsion/solvent evaporation method byusing biodegradable polymer PLGA andnon-ionic Pluronic F68 (a triblockco-polymer selected as an emulsifier and stabilizing agent for the forma-tion of PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites).

The synthesized products were characterized for interlayer structuralchanges in the solid by XRD, surfacemorphology and particle size by SEMand TEMwith EDX, physical status of the drug andMt by thermal studiesand drug loading by HPLC technique. The drug release profile of the syn-thesized PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocompositeswas investigated in simulated gastrointestinal fluid. The Mt–PPN–PLGAnanocomposites obtained were intercalated and partially exfoliated innature, spherical in shape with about 50–300 nm in size, the favorablesize range for intestinal mucosal membrane uptake. DSC results clear-ly indicate the degradation of the drug encased within synthesizedPPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites. The drugrelease profile of Mt–PPN–PLGA nanocomposites shows up to 14% ofthe drugwas released in simulated gastric fluidwhereas in simulated in-testinal fluid it shows up to 72% of drug release in a period 8 h. Thus wecan suggest that Mt–PLGA nanocomposites can be used as a potentialdrug carrier for the controlled drug delivery of the lowmolecular weightcationic hydrophilic drugs like PPN.

2. Materials and methods

2.1. Materials

MtKSF, PLGA50:50 (molecularweight 40–75,000), Pluronic F-68 anddrug PPN (purity >98%) were ordered from Sigma Aldrich St. LouiseUSA. HCl, KCl, NaOH, potassium dihydrogen phosphate of analyticalgrade for simulated gastric fluid HCl (pH 1.2) and simulated intestinalfluid (PBS, pH 7.4) preparation were ordered from MERCK (Germany).HPLC grade methanol and water were used for drug estimation byHPLC technique. All other reagents whether specified or not were of an-alytical grade. Double distilled water was used throughout the experi-mental work.

2.1.1. Synthesis of PPN–PLGA nanoparticlesIn this study, the water/oil/water (w/o/w) double emulsion solvent

evaporationmethod has been selected to encapsulate highly hydrophilicdrug PPN in the nanoparticles. PPN–PLGA nanoparticles were synthe-sized in two steps. First, PPN was dissolved in water and emulsified ina solution ofmethylene chloride containing PLGAundermagnetic stirringfollowed by sonication. In the second step, the primaryw/o emulsionwasemulsified in the external aqueous phase of Pluronic F68 (0.2%, w/v) to

form aw/o/w-emulsion. Themiddle organic phase separated the internalwater droplets from each other aswell as from the external aqueous con-tinuous phase. After solvent evaporation the PPN–PLGA nanoparticleswere isolated by centrifugation and washed with double distilled waterbefore freeze-drying.

2.1.2. Synthesis of PPN–PLGA–MMT nanocompositesThe synthesis ofMt–PPN–PLGA nanocomposites involved the emulsi-

fication of first w/o emulsion in Pluronic F-68 andMt aqueous dispersion(Fig. 1) followed by the same procedure as discussed in Section 2.1.1.

2.2. Characterizations

Powder X-ray diffraction (PXRD) measurements of samples wereperformed on a powder X-ray diffractometer (XPERT PRO Pananlytical,model (PW3040160, Netherland) the measurement conditions were aCu K α radiation, generated at 40 kV and 30 mA as X-ray source 2–40°(2θ) and step angle 0.01°/s. The differential scanning calorimetric studieswere conducted on a DSC instrument (DSC Q200 V23.10 Build 79). Thesamples were purged with dry nitrogen at a flow rate of 10 ml/minand the temperature was raised at 10 °C/min. The effect of Mt contenton thermal stability of the Mt–PPN–PLGA nanocomposites was assessedby the thermogravimetric analyzer (TGA 2050 Thermal gravimetricAnalyzer). The surface morphology and particle size of the synthesizedproducts were examined with the Scanning Electron Microscope (ZeissEVO 40) and high resolution transmission electron microscope (TECNAIG2 T30, U-TWIN) with an accelerating voltage of 300 kV.

2.3. Estimation of drug loading and encapsulation efficiency with highpressure liquid chromatography (HPLC technique)

2.3.1. HPLC apparatus and conditionsThe HPLC system consisted of a Shimadzu Model DGU 20 A5 HPLC

pump, a Shimadzu-M20A Diode Array Detector, Shimadzu column oven

Table 1Formulations of PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites.

S.No. PPN(mg)

Mt(mg)

P-F68(mg)

PLGA(mg)

Composite(mg)

A amount of PPN in thecomposite

mg D.L. (%) E.E. (%)

PPN-01 20 – 50 50 27.16 2.389 08.6 11.69PPN-02 20 – 50 100 79.97 2.23 02.82 12.16PPN-03 20 20 50 50 30.57 3.540 11.4 17.69PPN-04 40 20 50 50 40.00 14.072 35.17 35.17PPN-05 60 20 50 50 76.48 46.385 60.69 77.30

Fig. 2. XRD patterns of a — pristine Mt, b —Mt–PPN–PLGA nanocomposites (PPN-03), c —Mt–PPN–PLGA nanocomposites (PPN-04), d — Mt–PPN–PLGA nanocomposites (PPN-05),and e— pure PPN.

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CTO-10AS governed by a LC Solution software. The detector wavelengthwas set at 289 nm. Separation was achieved by low pressure gradi-ent elution by modifying the reported literature (El-Saharty, 2003)onmobile phase (40:60 ratio v/v) delivered at a flow rate of 1.0 ml/minat ambient temperature through a C18 analytical column Luna 5μ(250 × 4.6 mm i.d., 5 μm particle size).

2.3.2. Stock solutions and standardsStock solutions of PPN were prepared by dissolving 2.50 mg PPN

in 25 ml HPLC water, resulting in a solutions containing 100 μg/ml.This solution was diluted to give working standard solutions in concen-tration range of 0.5 to 50 μg/ml. Standards were prepared with the fol-lowing concentrations of 0.5, 1, 2, 4, 6, 8, 10, 15, 20, 25, 30 and 50 μg/mlfor PPN.

2.3.3. Preparation of sample solutionsSupernatants recovered after centrifugation of the synthesized

samples were used for the estimation of unloaded drug resulting inindirect estimation of drug encapsulation efficiency. 200 μl of super-natant was diluted up to 10 ml in a standard volumetric flask, filteredby 0.22 μm milipore filters. The filtered solutions were injected toHPLC.

The HPLC studies indicate that the calibration curve for known PPNsolutions was linear in the concentration range of 0.5 to 100.0 μg/ml inwater with a correlation coefficient of 0.99.

2.4. In vitro drug release studies

In vitro drug release studies of PPN were conducted in a constanttemperature bath with the dialysis bag technique (Joshi et al., 2009a,b).Buffer solution of pH 1.2 (simulated gastric fluid) was prepared bymixing 250 ml of 0.2 M HCL and 147 ml of 0.2 M KCL. Phosphate buffersolution (PBS) of pH 7.4 (simulated intestinal fluid) was prepared bymixing 250 ml of 0.1 MKH2PO4 and 195.5 ml of 0.1 MNaOH. In vitro re-lease studies were carried out in simulated intestinal fluid at pH 7.4 andsimulated gastric fluid at pH 1.2 using the dialysis bag technique. Dialysissacs were overnight equilibrated with the dissolution medium prior toexperiments. Weighed amount of the synthesized products was takenin 5 ml of buffer solution in the dialysis bag. The dialysis bag was dippedinto the receptor compartment containing 100 ml dissolution medium,whichwas stirred at 100 rpm at 37 ± 0.5 °C. The receptor compartmentwas closed to prevent the evaporation losses from the dissolution medi-um. The stirring speed was kept at 100 rpm. 5 ml of the sample waswithdrawn at regular time intervals and the same volume was replacedwith a fresh dissolution medium. Samples were analyzed for drugPPN content by UV spectrophotometer at λmax = 289 nm.

3. Results and discussion

In the series of experiment, the concentration of stabilizing agentPluronic F-68 was kept constant (0.2% wt/v) as per the reported crit-ical micelle concentration (Schmolka, 1977). In the case of PPN–PLGAnanoparticles PPN-01, the amount of drug encapsulated was found tobe about 12% (Table 1) and with further increase in polymer content(50 mg) the encapsulation efficiency was found to increase by about0.5%. Therefore, in order to avoid the presence of excess non-emulsifiedpolymer the amount of PLGA was fixed at 50 mg for all formulations. Ithas also beenobserved that in the case ofMt–PPN–PLGAnanocomposites,the maximum amount of drug (PPN-05) retained was 77%. Variations inthe composition of drug polymer–clay nanocomposites were furtherstudied in detail.

3.1. Effect of PPN content on drug loading and encapsulation efficiency

The drug loading and extent of drug encapsulation inMt–PPN–PLGAas function of PPN content were studied, The amount of PPN

encapsulated in the Mt–PPN–PLGA nanocomposites increases from 18to 35% in a linear manner (Table 1) with increase in drug to Mt ratiofrom 1:1 to 2:1, however with further increase in drug to Mt ratio upto 3:1, an increase in encapsulation efficiency up to 77.30% wasobtained. This excessive increase of encapsulation may be attributedto the cationic nature of PPN in the nanocomposites, which could en-hance the interaction of PPN with negatively charged Mt and polymerresulting in high encapsulation efficiency. The increase in drug loadingcan be attributed to the increase in final yield obtainedwhich is directlyinvolved in the calculation of drug loading percentage as per Eq. (1).

Drug loading%¼ Drug amount within the nanoparticles=Total weight of nanoparticlesð Þ X 100…

ð1Þ

Encapsulation efficiency%¼ Drug amount within the nanoparticles=initial drug amountð Þ X 100…

ð2Þ

Fig. 3. Diagrammatic representation of I — intercalated, II — partially exfoliated, and III — exfoliated Mt layers.

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3.2. XRD studies

The physical status of Mt and PPN in the synthesizedMt–PPN–PLGAnanocomposites was investigated with the help of XRD. The XRD pat-tern of pristine Mt shows characteristic diffraction peak at 2θ value of6.4° corresponding to 001 plane with d spacing of 13.6 A° (Fig. 2a). Inthe case of Mt–PPN–PLGA nanocomposites, PPN–03 (1:1 drug to clayratio) an increase in intensity of the 001 plane along with the shift inthe 2θ value, from 6.4° to 4.04°, was observed (Fig. 2b), the hump inthe background from 2θ values of 12° to 28° is due to the presence ofa polymer within the Mt–PPN–PLGA nanocomposites. According toBragg's law, a shift in 2θ value fromhigher diffraction angle to lower dif-fraction angle is indicative of an increase in d spacing i.e., from 13.6 A°to 21.4 A° (Joshi et al., 2009a,b; Liu et al., 2006; Lin et al., 2002) andan increase of 8 A° has been attributed to the intercalation of polymer–drug moiety (Fig. 3, case-I) and is further supported by the HRTEMimage (Fig. 7b) by the presence of expanded and uniformly spaced Mtlayers in the PPN-03Mt–PPN–PLGA nanocomposites. However, presenceof aminor component of a population cannot be ruled out because of thebroad nature of 001 reflection at 2θ value of 4.04°.

With the increase in drug to Mt ratio from 1:1 to 2:1 in the case of(PPN–04) and 3:1 in the case of (PPN-05), exfoliation of Mt layers

Fig. 4. TGA curves of, a — Pure Mt, b — PPN–PLGA nanoparticles (PPN-01), c — Mt–PPN–PLGA nanocomposites (PPN-03), and d — Mt–PPN–PLGA nanocomposites (PPN-05).

(Paul andRobeson, 2008) is being proposed (Fig. 2c & d). This is also sup-ported by the substantial suppression of 001 reflection at 2θ value of 4.5°and corresponding increase in the intensity of broad hump between 2θvalues of 12°–28°, which is indicative of the release of polymericmaterialfrom the interlayer gallery (Fig. 3, cases II and III). This fact is further sup-ported by the presence of exfoliated Mt layers in the HRTEM image ofPPN-05 Mt–PPN–PLGA nanocomposites (Fig. 7c).

Excessive amount of polymer–drug moiety within the interlayerscan no longer hold the Mt platelets together. Increase in drug en-capsulation efficiency from 18% (PPN-03) to 35% (PPN-04) and77% (PPN-05) can be attributed to the change in the nature of Mt–PPN–PLGA nanocomposite from intercalation of the drug polymermoie-ty (to a small extent) to adsorption of the exfoliated negatively chargedMt platelets on the drug–polymermoiety. The extent of drug encapsula-tion seems to be proportional to the extent of exfoliation in the case ofPPN-04 and PPN-05.

Further increase in drug content in the Mt–PPN–PLGAnanocomposites did not show further enhancement in the encapsulationefficiency indicating complete saturation of negative sites onMt platelets.

The pure crystalline drug PPN shows intense peaks at 14.56°,17.32°, 22.84°, 23.47°, 31.19°, 32.30°, 35.05°, 36.23° and 37.58° andthe observation is in good agreement with the reported values in the lit-erature (Wang et al., 2002). Mt–PPN–PLGA nanocomposites reveal the

Fig. 5. DSC curves of, a— Pure PPN, b— PPN–PLGA nanoparticles (PPN-01), c—Mt–PPN–PLGA nanocomposites (PPN-03), and d — Mt–PPN–PLGA nanocomposites (PPN-05).

Fig. 6. SEM–EDX images of a — PPN–PLGA nanoparticles and b — Mt–PPN–PLGA nanocomposites.

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presence of crystalline PPN in the nanocomposites (Fig. 2), with increasein drug to Mt ratio, the appearance of characteristic peaks of PPN be-comes more evident.

3.3. TGA studies

TheMt showsweight loss of 10% from 30 to 140 °C and is attributedto the loss of adsorbed and interlayer water (Fig. 4a). In the case ofMt–PPN–PLGA nanocomposites (PPN-03) due to the replacementof surface and interlayer water by organic moiety no such weightloss was observed in this region. Hence, the stability was observedin this region.

In the case of Mt–PPN–PLGA nanocomposites (PPN-05) due to ex-foliation of Mt no such weight loss was observed. Hence, the stabilitywas observed in this region.

In the temperature range of 30 to 425 °C PPN-PLGA nanoparticles(PPN-01), Mt–PPN–PLGA nanocomposites (PPN-03) and (PPN-05) show100%, 43.2% and 89.6%weight loss respectively (Fig. 4). It could be clearlyunderstood that weight loss observed in the case of Mt–PPN–PLGA

nanocomposites (PPN-03 and PPN05) is because of the thermal degra-dation of PPN, PF68 and PLGA contents present in the formulation(Dong and Feng, 2005). Mt content in the nanocomposites (PPN-03)and (PPN-05) is about 56.8% and 10.4% respectively.

TheMt–PPN–PLGA nanocomposite (PPN-03) shows less weight lossas compared to theMt–PPN–PLGA nanocomposite (PPN-05) because inthe case of the intercalated sample (PPN-03) the polymer–drug moietyis present within the ordered lattice whereas in the case of PPN-05 thehigh weight loss is due to the complete degradation of polymer–drugmoiety which is out of the order lattice due to the exfoliation.

3.4. DSC studies

The appearance of small endothermic peak about 48–50 °C followedby a broad endothermic peak in the temperature region of 360 °C corre-sponds to the glass transition temperature (Mukherjee andVishwanatha, 2009) and thermal decomposition of the polymer PLGAin PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites indi-cates no change in the polymer chain structure.

Table 2SEM–EDX analysis report.

Element Series C norm (wt.%) C Atom (at.%) C error (%)

a, PPN–PLGA nanoparticlesCarbon K series 48.77 55.42 14.7Nitrogen K series 7.29 7.11 2.2Silicon K series 0.04 0.02 0.0Oxygen K series 43.90 37.45 13.2Total 100.0 100.0

b, Mt–PPN–PLGA nanocompositesCarbon K series 47.48 57.09 14.5Oxygen K series 45.31 40.90 13.9Silicon K series 1.34 0.69 0.1Aluminium K series 1.26 0.67 0.1Iron K series 0.42 0.42 0.1Gold K series 2.98 0.22 0.1Total 100.0 100.0

90 Seema, M. Datta / Applied Clay Science 80–81 (2013) 85–92

Pure PPN reveals a sharp endothermic peak at 166 ºC and a broadendothermic peak at 292 ºC followed by an exothermic peak at300 °C corresponding to the melting point and the decompositionof PPN (Rojtanatanya and Pongjanyakul, 2010). The short broad en-dothermic region in the temperature range of 276 °C to 296 °C hasbeen observed in the case of PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites prepared and is due to the decomposition

Fig. 7. TEM-EDX images of a — PPN–PLGA nanoparticles (PPN-01), b — Mt–PPN–PLG

of PPN encapsulated within the PPN–PLGA nanoparticles and Mt–PPN–PLGA nanoparticles and nanocomposites (Fig. 5).

3.5. Scanning electron microscopic and EDX studies

PPN–PLGA nanoparticles (PPN-01) and Mt–PPN–PLGA nano-composites (PPN-03 to 05) appear to be 100–300 nm spherical parti-cles (inset Fig. 6), the former has a smooth surface and the latter has arough surface because of the presence of Mt nano platelets on thesurface which has been further confirmed by SEM–EDX studies(Fig. 6a & b, Table 2).

Due to the presence of carbon polymer chain and organic drugmoiety in case of PPN-01, high content of carbon, oxygen and nitrogenwas seen on the surface (Fig. 6, a) whereas, samples containing Mt,PPN-03 to 05, additional peaks of silicon, aluminium and iron confirmsthe presence of Mt nano platelets on the surface of the Mt–PPN–PLGAnanocomposites (Fig. 6b).

3.6. Transmission electron microscopic and EDX studies

PPN–PLGA nanoparticles (PPN-01) are spherical particles of50–200 nm in size (inset Fig. 7a). In the TEM micrograph of PPN03(Fig. 7b) uniformly spaced Mt layers are in support of intercalation(Table 3). In the TEM micrograph of PPN-05 (Fig. 7c), the presence ofexfoliated Mt layers is distinct. Both micrographs are also supportedby their corresponding XRD data.

A nanocomposites (PPN-03) and c — Mt–PPN–PLGA nanocomposites (PPN-05).

Fig. 8. Drug release profile of a — pure PPN, b — PPN–PLGA nanoparticles (PPN-01),c — intercalated Mt–PPN–PLGA nanocomposites (PPN-03) and d — exfoliated Mt–PPN–PLGA nanocomposites, (PPN-05) in simulated intestinal fluid (PBS, pH 7.4) at 37 °C.

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As has been observed in the case of SEM–EDX studies, the TEM–EDXstudies (Fig. 7a b and c; Table 3) also indicate the presence of high con-tent of carbon, oxygen and nitrogen in PPN-01 and additional peaks ofsilicon, aluminium and iron in samples PPN-03 and PPN-05 which con-firms the presence of Mt in the Mt–PPN–PLGA nanocomposites.

4. Drug release profile

PPN-01 and the samples containing Mt, PPN-03 & 05, have beenselected for the study of drug release kinetics, in simulated intestinalfluid PBS (pH 7.4) (Fig. 8). As per the XRD data, encapsulation of drughas been found in two kinds of Mt–PPN–PLGA nanocomposites inwhich the Mt particles were intercalated (PPN-03) and exfoliated(PPN-04 to PPN-05). In the latter category PPN-05 has been selectedbecause of its high yield, loading and encapsulation efficiency.

Release of pure drug (PPN) in simulated gastric (HCl, pH 1.2) andintestinal fluid (PBS, pH 7.4) was observed to be 86% (Fig. 9) and 89%(Fig. 8) over a period of 4 h respectively and in both the cases releasepattern was not in a controlled manner (~36% release per minute). WithPPN-01 only 28% of the encapsulated drug was released over a period of8 h whereas, the Mt–PPN–PLGA nanocomposites PPN-03 and PPN-05demonstrated a slow controlled cumulative drug release of 59% and72% in the PBS (pH 7.4) over a period of 8 h (Fig. 8). The increase in theamount of drug release with respect to the PPN-01 is related to the pres-ence of Mt platelets in the bulk and on the surface (further confirmed bySEM–EDX and TEM–EDX results). The presence of these platelets impartsporosity to the Mt–PPN–PLGA nanocomposites which results in higherease of passage through the Mt–PPN–PLGA nanocomposite because ofwhich the PPN-05 Mt–PPN–PLGA nanocomposites with higher extentof exfoliation also shows higher release of PPN in a controlled manneras represented by Fig. 10.

It is well understood that if a drug delivery system is able to retainhigh amount of drug in the stomach fluid, it would be able to release

Table 3TEM–EDX analysis report.

Element Weight% Atomic%

a — PPN–PLGA nanoparticles (PPN-01)C K 58.6 77.3N K 2.7 3.1O K 11.3 11.1F K 2.2 1.8Ca K 2.9 1.1Cu K 22.3 5.6Total 100.0 100.0

b — Mt–PPN–PLGA nanocomposites (PPN-03)C K 20.9 31.5N K 6.7 8.7O K 35.7 40.4Mg K 4.1 3.1Al K 4.0 2.7Si K 14.5 9.4K K 0.9 0.4Fe K 3.2 1.0Cu K 9.9 2.8Total 100.0 100.0

c — Mt–PPN–PLGA nanocomposites (PPN-05)C K 27.8 31.5N K 6.9 8.7O K 35.2 40.4Mg K 0.2 3.1Al K 6.2 2.7Si K 12.7 9.4K K 0.5 0.4Fe K 2.1 1.0Co K 0.3 0.1Cu K 11.1 3.0Total 100.0 100.0

more drug in the intestine (Chaturvedi et al., 2010) which is the desiredsite of drug absorption. In this study we found that over a period of 8 hin simulated gastric fluid (HCl, pH 1.2), PPN-01 andMt containing sam-ples PPN-03 and PPN-05 show 18%, 14% and 28% drug release respec-tively (Fig. 9). This low release of PPN from PPN-03 is probably relatedwith the stability of Mt in acidic media which prevents the release ofdrug in acidicmedia (Junping et al., 2006). In the case of the formulationPPN-05, collapse ofMt layered structurewas observedwhich comes outto be less effective in the acidic media as compared to the PPN-03.

The controlled behavior of PPN release could also be explained bythe barrier properties or hindrance in the path offered by high amountof Mt layers to release the drug in both the releasing media (Fig. 10).

5. Conclusion

In the present study an oral controlled drug delivery system forPPN loaded PLGA nanoparticles and Mt–PPN–PLGA nanocompositeswas developed by w/o/w double emulsion solvent evaporation tech-nique. About 77% entrapment efficiency and 72% release were achievedfor the highly hydrophilic drug, PPN. Two types of Mt–PPN–PLGA

Fig. 9. Drug release profile of a — pure PPN, b — PPN–PLGA nanoparticles (PPN-01),c — intercalated Mt–PPN–PLGA nanocomposites (PPN-03) and d — exfoliated Mt–PPN–PLGA nanocomposites, (PPN-05) in simulated gastric fluid (HCl, pH 1.2) at 37 °C.

Fig. 10. Diagrammatic representation of drug path within a — intercalated and b — exfoliated Mt–PPN–PLGA nanocomposites.

92 Seema, M. Datta / Applied Clay Science 80–81 (2013) 85–92

nanocomposites (intercalated and exfoliated Mt) were obtained. Thepresence of drug within the PPN–PLGA nanoparticles and Mt–PPN–PLGA nanocomposites nanoparticles and nanocomposites was also con-firmed by DSC data.

50–300 nm spherical PPN–PLGA nanoparticles and Mt–PPN–PLGAnanocomposites was obtained with the Mt platelets on the surface(confirms by SEM–EDX and TEM–EDX data). The drug release profileof PPN was found to be pH dependent, the presence of Mt plateletswithin the PPN–PLGA formulations results in controlled and higher %release of drug. Therefore, it can be said that the synthesized formula-tions have high potential as a controlled drug delivery system for PPN.

Disclosure

The authors report no conflicts of interest in this work.

Acknowledgments

We sincerely express our thanks to the director, USIC, Universityof Delhi for instrumentation facilities, Director, AIRF, JNU for providingSEM facilities and UGC/RGNF for providing financial assistance for thisresearch work under the project of sch/rgnf/srf/f-10/2007-08. The au-thors are thankful to Dr. R Nagarajan for his valuable suggestions re-garding the interpretation of XRD and TGA data.

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