European Journal of Pharmaceutics and Biopharmaceutics (v.67, #1)
Anticancer activity of cisplatin-loaded PLGA-mPEG nanoparticles on LNCaP prostate cancer cells
by Evangelos C. Gryparis; Maria Hatziapostolou; Evangelia Papadimitriou; Konstantinos Avgoustakis (pp. 1-8).
The in vitro anticancer activity of cisplatin-loaded PLGA-mPEG nanoparticles on human prostate cancer LNCaP cells was investigated. The uptake of the PLGA-mPEG nanoparticles by the LNCaP cells was also studied. Blank PLGA-mPEG nanoparticles exhibited low cytotoxicity, which increased with increasing PLGA/PEG ratio in the PLGA-mPEG copolymer used to prepare the nanoparticles, possibly due to the increased cell uptake observed with increasing PLGA/PEG ratio. PLGA-mPEG nanoparticles loaded with cisplatin exerted in vitro anticancer activity against LNCaP cells that was comparable to the activity of free (non-entrapped in nanoparticles) cisplatin. Little differences in the in vitro anticancer activity of the different nanoparticle compositions were found, which may result from the differences observed between the different nanoparticles compositions in the uptake by the LNCaP cells and in the leakage of cisplatin from the nanoparticles during incubation with the cells. Visual evidence of nanoparticles’ uptake by the LNCaP cells was obtained with nanoparticles labeled with PLGA(4165)-PyrBu(274) or dextran-rhodamine B isothiocyanate using fluorescence microscopy. Moreover, in some cases fluorescence around or inside cell nuclei was observed, which, if verified by further studies, would indicate that PLGA-PEG nanoparticles might prove to be useful in site-specific delivery of drugs whose site of pharmacological activity is cell nucleus.
Keywords: Poly(lactide-co-glycolide)-methoxy-poly(ethylene glycol); Nanoparticles; PLGA-mPEG; Cisplatin; Cytotoxicity; LNCaP cells; Anticancer activity; PLGA-PEG
Preparation and antitumor characteristics of PLA/(PEG-PPG-PEG) nanoparticles loaded with camptothecin
by Ryotaro Kunii; Hiraku Onishi; Yoshiharu Machida (pp. 9-17).
Camptothecin (CPT)-loaded nanoparticles were prepared using poly(dl-lactic acid) (PLA) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PEG-PPG-PEG), and examined for particle characteristics, in vitro release, pharmacokinetics and efficacy. The preparative condition, in which the ratio of PLA/PEG-PPG-PEG/CPT was 35/35/4 (w/w/w) and organic solvent (dichloromethane) was evaporated from the emulsion at 18°C, gave the nanoparticles with the diameter of approximately 230nm, fairly high drug content (ca. 1.6% (w/w)) and stable entrapment of the drug, which were used for in vivo studies. After i.v. administration to normal rats, the nanoparticles showed slightly smaller AUC but much larger MRT as compared with CPT solution, and delivered the drug greatly to the surrounding tissues, in particular to the liver. When antitumor effect was examined by i.v. administration to mice bearing sarcoma 180 (S-180) solid tumor, the nanoparticles showed a significant suppression of tumor growth without body weight loss, and their effect was better than that of CPT solution. The PLA/PEG-PPG-PEG nanoparticles were considered potentially useful to enhance the efficacy of CPT, to which the high drug retention in the body and gradual drug release appeared to be importantly related.
Keywords: PLA/(PEG-PPG-PEG) nanoparticles; Camptothecin; In vitro release; Pharmacokinetics; Antitumor effect
Dexamethasone-loaded nanoparticle-coated microparticles: Correlation between in vitro drug release and drug transport across Caco-2 cell monolayers
by R.C.R. Beck; A.R. Pohlmann; C. Hoffmeister; M.R. Gallas; E. Collnot; U.F. Schaefer; S.S. Guterres; C.M. Lehr (pp. 18-30).
This work reports the preparation of dexamethasone in nanoparticle-coated microparticles and the study of the influence of such microencapsulation on drug absorption across Caco-2 cell monolayers. Nanoparticle-coated microparticles were prepared by spray-drying using nanocapsules (NC) or nanospheres (NS) in aqueous suspensions as coating material. Drug contents ranged from 64 to 134mgg−1, yields between 49% and 67% and moisture content below 2.0%. SEM and AFM analysis demonstrated that the nanoparticle-coated microparticles (20–53μm) show nanostructures on their surface with a similar diameter compared to the aqueous suspensions. The type of nanocoating material had a significant influence on the drug release profile and on the drug permeation across Caco-2 cells: NC-coated microparticles led to a prolonged release and slower transport across Caco-2 cell monolayers, while the NS-coated microparticles showed a faster release and Caco-2 transport compared to uncoated microparticles. The correlation between the amount of drug permeated and the drug released (%) suggests that the drug absorption from such a delivery system is controlled mainly by the release rate rather than by epithelial permeability. Caco-2 transport studies appear to be a useful characterization tool for the development of microparticulate oral controlled release systems.
Keywords: Caco-2 cells; Dexamethasone; Microparticles; Nanoparticles; Spray-drying
Optimization of iron oxide nanoparticles encapsulation within poly(d,l-lactide-co-glycolide) sub-micron particles
by Lazare Ngaboni Okassa; Hervé Marchais; Laurence Douziech-Eyrolles; Katel Hervé; Simone Cohen-Jonathan; Emilie Munnier; Martin Soucé; Claude Linassier; Pierre Dubois; Igor Chourpa (pp. 31-38).
This work describes a method for preparation of sub-micron poly(d,l-lactide-co-glycolide) (PLGA) particles loaded with magnetite/maghemite nanoparticles to be used as magnetically-controlled drug delivery systems. The methodology of simple emulsion/evaporation technique has been optimized to provide greater iron oxide loading rates. The surface of iron oxide nanoparticles was coated with oleic acid (OA) for better compatibility with organic phase containing the polymer. To increase their loading into polymeric sub-micron particles, we added dried iron oxide nanoparticles in variable ferrite/polymer ratio of 1:1; 1:1.5 and 1:2 w/w. Composition and surface properties of obtained composite sub-micron particles have been studied in comparison with those of ferrite-free PLGA sub-micron particles. Presence of magnetite/maghemite was qualitatively confirmed by characteristic bands in the FT-IR spectra of composite sub-micron particles. Quantification of the incorporated iron was achieved by AAS. The highest incorporation rates of ferrite (up to 13.5% w/w) were observed with initial ferrite/polymer ratio of 1:1 w/w. TEM images indicate that the composite sub-micron particles are nearly spherical. According to laser granulometry data, average hydrodynamic diameter of the composite sub-micron particles is close to 280nm, independently of ferrite presence. Electrophoretic properties (zeta potential) were very similar for both composite and ferrite-free PLGA sub-micron particles, thus indicating that the polymeric coating should mask the surface of ferrite nanoparticles buried inside. Finally, composite sub-micron particles exhibit superparamagnetic property.
Keywords: Oleic acid-coated magnetite nanoparticles; PLGA; Composite sub-micron particles; Emulsion–evaporation technique; Magnetic carrier technology
Nanoparticle layers controlling drug release from emulsions
by Spomenka Simovic; Clive A. Prestidge (pp. 39-47).
The influence of interfacial layers of silica nanoparticles on the release kinetics of a model lipophilic drug (di-butyl-phthalate (DBP)) from polydimethylsiloxane droplets in water is reported. The nanoparticle layers are formed by self-assembly from solution and their structure is controlled by nanoparticle hydrophobicity and the solution conditions. For DBP loading levels resulting in released concentrations below the solubility limit, release is rapid from uncoated droplets whereas significant sustained release is facilitated by rigid interfacial layers of hydrophobic silica nanoparticles. Activation energies for release are in the range 580–630kJmol−1, which is ten times greater than for barriers introduced by typical polymeric stabilisers. In contrast, at higher DBP loading levels (total concentration greater than the solubility level), both hydrophilic and hydrophobic nanoparticle layers increase the rate and extent of dissolution compared with uncoated droplets and pure DBP solutions. Nanoparticle layers are shown to significantly influence the release kinetics of lipophilic drugs from oil in water emulsions: either sustained or enhanced release properties can be introduced depending on the nanoparticle layer type and drug loading level. Thus, nanoparticle layers may be engineered to facilitate a range of release behaviours and offer great potential in the delivery of poorly soluble drugs.
Keywords: Emulsions; Nanoparticles; Encapsulation; Drug release
Solid lipid nanodispersions containing mixed lipid core and a polar heterolipid: Characterization
by A.A. Attama; B.C. Schicke; T. Paepenmüller; C.C. Müller-Goymann (pp. 48-57).
This paper describes the characterization of solid lipid nanodispersions (SLN) prepared with a 1:1 mixture of theobroma oil and goat fat as the main lipid matrix and Phospholipon 90G® (P90G) as a stabilizer heterolipid, using polysorbate 80 as the mobile surfactant, with a view to applying the SLN in drug delivery. The 1:1 lipid mixture and P90G constituting the lipid matrix was first homogeneously prepared by fusion. Thereafter, the SLN were formulated with a gradient of polysorbate 80 and constant lipid matrix concentration by melt-high pressure homogenisation. The SLN were characterized by time-resolved particle size analysis, zeta potential and osmotic pressure measurements, differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). Transmission electron microscopy (TEM) and isothermal heat conduction microcalorimetry (IMC) which monitors the in situ crystallization were also carried out on the SLN containing P90G and 1.0 % w/w of polysorbate 80. The results obtained in these studies were compared with SLN prepared with theobroma oil with and without phospholipid. Particle size analysis of SLN indicated reduction in size with increase in concentration of mobile surfactant and was in the lower nanometer range after 3 months except SLN prepared without P90G or polysorbate 80. The lipid nanoparticles had negative potentials after 3 months. WAXD and DSC studies revealed low crystalline SLN after 3 months of storage except in WAXD of SLN formulated with 1.0 % w/w polysorbate 80. TEM micrograph of the SLN containing 1.0 % w/w polysorbate 80 revealed discrete particles whose sizes were in consonance with the static light scattering measurement. In situ crystallization studies in IMC revealed delayed crystallization of the SLN with 1.0 % w/w polysorbate 80. Results indicate lipid mixtures produced SLN with lower crystallinity and higher particle sizes compared with SLN prepared with theobroma oil alone with or without P90G, and would lead to higher drug incorporation efficiency when used in formulation of actives. Mixtures of theobroma oil and goat fat would be suitable for the preparation of nanostructured lipid carriers. SLN of theobroma oil containing phospholipid could prove to be a good ocular or parenteral drug delivery system considering the low particle size, particle size stability and in vivo tolerability of the component lipids. SLN prepared with lipid admixture, which had higher increase in d90% on storage are suitable for preparation of topical and transdermal products.
Keywords: Mixed lipid; Theobroma oil; Phospholipon 90G; ®; Solid lipid nanoparticles; Nanostructured lipid carriers; Characterization; Drug delivery
Serum-resistant lipopolyplexes for gene delivery to liver tumour cells
by Leire García; Maria Buñuales; Nejat Düzgüneş; Conchita Tros de Ilarduya (pp. 58-66).
In this study, an efficient non-viral gene transfer system has been developed by employing polyethylenimine (PEI 800, 25 and 22kDa) and DOTAP and cholesterol (Chol) as lipids (lipopolyplex), at three different lipid/DNA molar ratios (2/1, 5/1 and 17/1) by using five different protocols of formulation. Condensation assays revealed that PEI of 800, 25 and 22kDa were very effective in condensing plasmid DNA, leading to a complete condensation at N/P ratios above 4. Addition of DOTAP/Chol liposomes did not further condense DNA. Increasing the molar ratio lipid/DNA in the complex resulted in higher positive values of the ζ-potential, while the particle size increased in some protocols, but not in others. High molecular weight PEI (800kDa) used in the formulation of lipopolyplexes lead to a bigger particle size, compared to that obtained with smaller PEI species, whether branched (25kDa) or linear (22kDa). These vectors were also highly effective in protecting DNA from attack by DNAse I. Transfection activity was maximal by using protocols 3 and 4 and a lipid/DNA molar ratio of 17/1. These complexes showed high efficiency in gene delivery of DNA to liver cancer cells, even in the presence of high concentration of serum (60% FBS). On the other hand, complexes formed with linear PEI (22kDa) were more effective than lipopolyplexes containing branched PEI (800 or 25kDa). The complexes resulted to be much more efficient than conventional lipoplexes (cationic lipid and DNA) and polyplexes (cationic polymer and DNA). The same behaviour was observed for complexes prepared in the presence of the therapeutic gene pCMVIL-12. Toxicity assays revealed a viability higher than 80% in all cases, independently of the protocol, molar ratio (lipid/DNA), molecular weight and type of PEI.
Keywords: Gene delivery; Cationic liposomes; Polyethylenimine; Lipopolyplexes; Non-viral vectors; Cancer gene therapy
A study of the formulation design of acoustically active lipospheres as carriers for drug delivery
by Jia-You Fang; Chi-Feng Hung; Mei-Hui Liao; Chih-Chen Chien (pp. 67-75).
Acoustically active lipospheres (AALs) were prepared using perfluorocarbons and coconut oil as the cores of inner phase. These AALs were stabilized using coconut oil and phospholipid coatings. A lipophilic antioxidant, resveratrol, was the model drug loaded into the AALs. AALs with various percentages of perfluorocarbons and oil were prepared to examine their physicochemical and drug release properties. Co-emulsifiers such as Brij 98 and Pluronic F68 (PF68) were also incorporated into AALs for evaluation. AALs with high resveratrol encapsulation rates (∼90%) were prepared, with a mean droplet size of 250–350nm. The AALs produced with perfluorohexane as the core material had larger particle sizes than those with perfluoropentane. Resveratrol in these systems exhibited retarded drug release in both the presence and absence of plasma in vitro; the formulations with high oil and perfluorocarbon percentages showed the lowest drug release rates. The addition of PF68 slightly but significantly reduced resveratrol delivery from the AALs. Ultrasound treatment of 1MHz produced an increase in the drug release from the systems, illustrating the drug-targeting effect of the combination of AALs and ultrasound.
Keywords: Acoustically active lipospheres; Resveratrol; Perfluorocarbons; Drug delivery; Formulation design
Reduced hepatic toxicity, enhanced cellular uptake and altered pharmacokinetics of stavudine loaded galactosylated liposomes
by Minakshi Garg; Tathagata Dutta; Narendra Kumar Jain (pp. 76-85).
The aim of the present investigation was to reduce the hepatic toxicity, enhance the cellular uptake and alter the pharmacokinetics of stavudine using galactosylated liposomes. β-d-1-Thiogalactopyranoside residues were covalently coupled with dimyristoyl phosphatidylethanolamine, which was then used to form liposomes. The galactosylated liposomal system was assessed for in vitro ligand-specific activity. The drug release from liposomes was studied by dialysis method. Ex vivo cellular uptake study was performed using liver parenchymal cells harvested from male albino rats. Changes in hematological parameters, hepatic enzymes, hepatomegaly, plasma and tissue distribution of the formulations (free stavudine solution, uncoated liposomal and galactosylated liposomes) were determined using albino rats. Percent cumulative drug release in 24h was low (34.8±2.6%). Enhanced hepatic cellular d4T uptake (27.96±2.41pg d4T/million cells) was seen in case of galactosylated liposomal d4T. Galactosylated liposomes maintained a significant level of d4T in tissues rich in galactose specific receptors and had a prolonged residence (11.44±1.25h) in the body resulting in enhanced half-life of d4T (23.07±1.25h). This formulation did not show either hematological or hepatic toxicity. Galactosylation of liposomes alter the biodistribution of encapsulated drug thereby delivering the drug to cells bearing galactose specific receptors.
Keywords: Galactosylated liposomes; Stavudine; Hepatic toxicity; Ricinus communis; lectin; Pharmacokinetics
Development, characterization and in vivo evaluation of benzocaine-loaded liposomes
by Paola Mura; Francesca Maestrelli; Maria Luisa González-Rodríguez; Ilaria Michelacci; Carla Ghelardini; Antonio M. Rabasco (pp. 86-95).
This study reports the development and in vivo evaluation of a liposomal formulation of the local anaesthetic benzocaine. Multi-lamellar (MLV) and small uni-lamellar (SUV) vesicles entrapping benzocaine were prepared using 50:50 w/w phosphatidylcholine–cholesterol as lipophilic phase and 50:50 v/v ethanol–water as hydrophilic phase. Liposome size, Zeta-potential, encapsulation efficiency and skin penetration properties were determined. Drug permeation from liposomal dispersions, as such or formulated in Carbopol gel, was evaluated through artificial lipophilic membranes and excised abdominal rat skin, whereas in vivo anaesthetic effect was tested on rabbits. Interestingly, addition of the drug into the hydrophilic phase, rather than into the lipophilic one, during liposome preparation enabled an improvement of the MLV’s entrapment efficiency from 29.7% to 82.3%. On the other hand, sonication conditions to obtain SUV influenced size and polydispersity index of the vesicles and reduced the entrapment efficiency by about 30%. All liposomal-benzocaine formulations showed sustained release properties and a more intense anaesthetic effect than plain drug. Permeation experiments from drug solutions in gel containing the same amount of ethanol as in the liposomal formulations made it possible to exclude a possible enhancer effect of this solvent, at least when not used in liposomal formulations. MLV with the drug added into the hydrophilic phase gave the most effective formulation, showing a permeability coefficient value 2.5 times higher than that of the plain drug and allowing a significant improvement ( P<0.01) not only of intensity but also of duration of anaesthetic effect of benzocaine. These results suggest that a suitably developed liposomal formulation of benzocaine can be of actual value for improving its clinical effectiveness in topical anaesthesia.
Keywords: Benzocaine; Liposome; Skin permeation; In vivo; anaesthetic effect
The effect of different lipid based formulations on the oral absorption of lipophilic drugs: The ability of in vitro lipolysis and consecutive ex vivo intestinal permeability data to predict in vivo bioavailability in rats
by Arik Dahan; Amnon Hoffman (pp. 96-105).
The purpose of this study was to investigate the impact of different lipid based formulations of lipophilic drugs on in vitro solubilization and intestinal ex vivo permeability processes. Thereafter, to evaluate the ability of these in vitro and ex vivo results to predict the corresponding in vivo oral bioavailability data. The dissolution of dexamethasone and griseofulvin in long (LCT), medium (MCT) and short (SCT) chain triglyceride formulations was tested in a dynamic in vitro lipolysis model. Following the completion of the lipolysis, the permeability through the gut wall was tested in an ex vivo side-by-side diffusion chamber model. The absolute oral bioavailability of the drugs from the tested formulations was investigated in rats. The dynamic in vitro lipolysis experiments indicated an equivalent performance of the different formulations for dexamethasone, and a performance rank order of MCT>LCT>SCT>H2O for griseofulvin. In the subsequent ex vivo permeability studies, the SCT formulation caused enhanced permeation with doubled permeability coefficient for both drugs. The in vivo bioavailability of both drugs correlated well with the in vitro data, i.e., LCT=MCT=SCT for dexamethasone and MCT>LCT>SCT>H2O for griseofulvin, despite the significant augmented intestinal permeability produced by the SCT formulation. In conclusion, the in vitro lipolysis model was found to be useful in the intelligent optimization of oral lipid formulations for lipophilic drugs, even in the case where the intestinal permeability is enhanced by the formulation. The SCT vehicle showed to be a potential permeability enhancer; however, for class 2 compounds, the permeability does not correlate with in vivo bioavailability.
Keywords: Lipophilic drugs; Lipid based formulations; Bioavailability; Intestinal absorption; In vitro; lipolysis; Ex vivo; Ussing chamber; Intestinal permeability
Determination of ibuprofen solubility in wax: A comparison of microscopic, thermal and release rate techniques
by Gbolahan Samuel Oladiran; Hannah Katharine Batchelor (pp. 106-111).
The solubility of ibuprofen in Witepsol H15, a semi-solid wax matrix, was determined using microscopy, Higuchi release rates and HyperDSC (high speed differential scanning calorimetry); solubility values of 15–20%, 18.6% and 12.7% w/w resulted from the three techniques, respectively. Microscopy was useful in additionally examining crystal size, shape and homogeneity. Release rate experiments showed that release from these formulations followed Higuchi kinetics with an inflection in release rate constant at the drug loading corresponding to drug solubility. HyperDSC not only measured solubility but also determined the melting point of the formulation. The results from these three techniques correlated well, suggesting that the simpler techniques of microscopy or HyperDSC are appropriate to determine the solubility in semi-solid pharmaceutical formulations.
Keywords: HyperDSC; Ibuprofen; Witepsol; Solubility; Higuchi release rate
Performance comparison of a co-crystal of carbamazepine with marketed product
by Magali B. Hickey; Matthew L. Peterson; Lisa A. Scoppettuolo; Sherry L. Morrisette; Anna Vetter; Hector Guzmán; Julius F. Remenar; Zhong Zhang; Mark D. Tawa; Sean Haley; Michael J. Zaworotko; Örn Almarsson (pp. 112-119).
The carbamazepine: saccharin co-crystal (1) was studied in terms of a series of attributes, including suitability for multi-gram scale-up, propensity for crystal polymorphism, physical stability, in vitro dissolution and oral bioavailability, with the goal of comparing1 with the marketed form of carbamazepine (Tegretol®). Preparation of1 was achieved on a 30g scale with a conventional cooling crystallization process from alcohol solution without seeding. The compound is not overtly polymorphic. This finding is in contrast to the form diversity of pure carbamazepine, which has four known polymorphs and a host of solvates, including a dihydrate, which is the stable form in the presence of water. Physical and chemical stability of the co-crystal is also shown to be quantitatively similar to the pure drug in the marketed product (Tegretol®). Finally, comparison of oral bioavailability of1 with Tegretol® tablets in dogs shows the co-crystal to be a viable alternative to the anhydrous polymorph in formulated solid oral products. The balance of properties and performance of1 as a model co-crystal is discussed.
Keywords: Polymorphs; Pharmaceutical; Co-crystal; Saccharin; Dihydrate; Dissolution; Stability; Bioavailability
Optimisation of polyherbal gels for vaginal drug delivery by Box-Behnken statistical design
by Shruti Chopra; Sanjay K. Motwani; Zeenat Iqbal; Sushma Talegaonkar; Farhan J. Ahmad; Roop K. Khar (pp. 120-131).
The present research work aimed at development and optimisation of mucoadhesive polyherbal gels (MPG) for vaginal drug delivery. As the rheological and mucoadhesive properties of the gels correlate well to each other the prepared MPGs were optimised for maximum mucoadhesion using a relationship between the storage modulus ( G′) and Gel Index (GI), by employing a 3-factor, 3-level Box-Behnken statistical design. Independent variables studied were the polymer concentration ( X1), honey concentration ( X2) and aerosil concentration ( X3). Aerosil has been investigated for the first time to improve the consistency of gels. The dependent variables studied were the elastic modulus, G′( Y1), gel index ( Y2), and maximum detachment force ( Y3) with applied constraints of 500⩽ Y1⩽700 and 4⩽ Y2⩽5. Response surface plots were drawn, statistical validity of the polynomials was established and optimised formulations was selected by feasibility and grid search. Three types of Carbopol studied were Carbopol 934P, Carbopol 974P and Polycarbophil. In vitro release studies were carried out for the optimised formulations and the data were fitted to release kinetics equations. Validation of the optimisation study with 8 confirmatory runs indicated high degree of prognostic ability of response surface methodology. Gels showed a gradual sustained release by a non-Fickian diffusion process. Incorporation of aerosil to gels was found to improve the rheological and mucoadhesion properties by about 50–54% and 7–11%, respectively. The Box-Behnken design facilitated the optimisation of polyherbal gel formulations for enhanced vaginal drug delivery by optimum mucoadhesion and longer retention.
Keywords: Optimisation; Box-Behnken design; Formulation; Polyherbal gels; Mucoadhesion
Mucoadhesive properties of various pectins on gastrointestinal mucosa: An in vitro evaluation using texture analyzer
by Nartaya Thirawong; Jurairat Nunthanid; Satit Puttipipatkhachorn; Pornsak Sriamornsak (pp. 132-140).
Mucoadhesive performance of various pectins with different degrees of esterification and molecular weights was examined with porcine gastrointestinal (GI) mucosa, i.e. buccal, stomach, small intestine and large intestine, using a texture analyzer equipped with mucoadhesive platform. The instrumental parameters and test conditions such as pre-hydration time of pectin disc, contact time, contact force, test speed of probe withdrawal, GI tissue and test medium were also studied. Two parameters derived from texture analysis, namely maximum detachment force ( Fmax) and work of adhesion ( Wad), were used as parameters for comparison of mucoadhesive performance. The results indicated that degree of hydration of pectin disc affected the mucoadhesive properties. The mucoadhesion of pectin increased with the increased contact time and contact force, but not by the increased probe withdrawal speed. Tissue from different parts of GI tract and test medium also influenced the mucoadhesion. Pectins showed a stronger mucoadhesion on large intestinal mucosa than on small intestinal mucosa. The mucoadhesive properties of pectins on gastric mucosa depended on pH of the medium; a higher Fmax and Wad in a pH 4.8 medium than a pH 1.2 medium was revealed. Additionally, pectin showed a significantly higher mucoadhesion than carbomer934P in most of the GI mucosa tested. The results also demonstrated that the mucoadhesive performance of pectins largely depended on their characteristics, i.e. higher degree of esterification and molecular weight gave a stronger mucoadhesion. These findings suggest that pectin can be used as a mucoadhesive carrier for GI-mucoadhesive drug delivery systems.
Keywords: Pectin; Mucoadhesion; Mucoadhesive properties; Texture analyzer; Detachment force; Work of adhesion; Gastrointestinal tract
Cetyl palmitate-based NLC for topical delivery of Coenzyme Q10 – Development, physicochemical characterization and in vitro release studies
by Veerawat Teeranachaideekul; Eliana B. Souto; Varaporn B. Junyaprasert; Rainer H. Müller (pp. 141-148).
In the present study, nanostructured lipid carriers (NLC) composed of cetyl palmitate with various amounts of caprylic/capric triacylglycerols (as liquid lipid) were prepared and Coenzyme Q10 (Q10) has been incorporated in such carriers due to its high lipophilic character. A nanoemulsion composed solely of liquid lipid was prepared for comparison studies. By photon correlation spectroscopy a mean particle size in the range of 180–240nm with a narrow polydispersity index (PI) lower than 0.2 was obtained for all developed formulations. The entrapment efficiency was 100% in all cases. The increase of oil loading did not affect the mean particle size of NLC formulations. NLC and nanoemulsion, stabilized by the same emulsifier, showed zeta potential values in the range −40/−50mV providing a good physical stability of the formulations. Scanning electron microscopy studies revealed NLC of disc-like shape. With respect to lipid polymorphism, a decrease in the ordered structure of NLC was observed with the increase of both oil and Q10 loadings, allowing therefore high accommodation for Q10 within the NLC. Using static Franz diffusion cells, the in vitro release studies demonstrated that Q10-loaded NLC possessed a biphasic release pattern, in comparison to Q10-loaded nanoemulsions comprising similar composition of which a nearly constant release was observed. The NLC release patterns were defined by an initial fast release in comparison to the release of NE followed by a prolonged release, which was dependent on the oil content.
Keywords: Nanostructured lipid carriers; NLC; Coenzyme Q; 10; Cetyl palmitate; In vitro; release
Reversible effects of permeation enhancers on human skin
by L. Kang; A.L. Poh; S.K. Fan; P.C. Ho; Y.W. Chan; S.Y. Chan (pp. 149-155).
This study outlines a systematic approach for investigating a desired characteristic of chemicals used to facilitate the permeation of drugs across the skin that is, the reversibility of the permeation enhancement effect. This implies that the vital skin barrier function is restored and not permanently impaired after the application of these enhancers. The reversible effects of two terpene enhancers, ( R)-(−)-carvone and eucarvone, on excised human skin were evaluated by in vitro permeation and extraction studies on normal (untreated) and enhancer-pretreated epidermis, respectively. For the permeation studies on normal epidermis, the donor solutions were the model drug, haloperidol (HP, 3mg/ml), in propylene glycol (PG) with or without 5% (w/v) enhancer and for the extraction studies using epidermis pretreated with enhancer, a solution of HP (3mg/ml) in PG was used. The solubilities of the enhancers in 0.03% lactic acid (receptor solution) and of HP in PG (donor solution) were determined to demonstrate that the sink and saturated conditions were maintained in the respective compartments of the flow-through cells throughout the in vitro experiments. ( R)-(−)-Carvone cleared out of the skin faster than eucarvone. This could be due to the 4-fold higher skin permeability of ( R)-(−)-carvone compared to that of eucarvone. The amount of HP deposited in the epidermis was much lower in the eucarvone-pretreated epidermis than that pretreated with ( R)-(−)-carvone. The permeation profile of HP across the enhancer-pretreated skin was 4-fold greater than in the vehicle alone (control), but similar to that across untreated skin with enhancer present in the donor solution, indicating that permeation across the enhancer-pretreated skin did not change. The enhancing effects of both terpenes on the skin were found to be reversible and the permeability of the skin was left intact after the passage of the drug in the vehicle with these enhancers.
Keywords: Skin permeation; Chemical enhancer; Reversibility; Transdermal drug delivery; Haloperidol; Terpene
Probing the skin permeation of eicosapentaenoic acid and ketoprofen
by Christopher P. Thomas; Charles M. Heard (pp. 156-165).
Unexpected enhancement of the topical delivery of eicosapentaenoic acid (EPA) across porcine skin was observed previously when fish oil was co-formulated with ketoprofen. In the current work depth profile analysis was used to probe the epidermal conversion of EPA to its 15-hydroxy metabolite in the presence and absence of ketoprofen. Freshly excised full-thickness porcine skin in Franz diffusion cells was dosed (both infinite and finite) with simple formulations based on fish oil as source of EPA. After 24h the skin was subjected to tape stripping and depth profiles were constructed. Typical depth profiles were obtained, with an inverse relationship between depth and permeant concentration. 15-HEPE was generated in the skin when Hepes-modified Hanks’ balanced salt solution was used, but none was detected when a cetrimide receptor phase was used, highlighting the importance of maintaining skin viability in such exercises. Ketoprofen had a direct influence on the metabolism of EPA and resulting in conversion to its 15-LOX metabolite 15-HEPE. However, this link appears to be only part of the solution of EPA enhancement however, as even in non-viable skin ketoprofen had an enhancing affect.
Keywords: EPA; Metabolism; Skin; Ketoprofen; 15-HEPE; Fish oil
Effect of HLB of additives on the properties and drug release from the glyceryl monooleate matrices
by Manish H. Shah; Anant Paradkar (pp. 166-174).
Glyceryl monooleate (GMO) is an amphiphilic surfactant, which as such can solubilize hydrophilic, lipophilic and amphiphilic drug molecules in its different polarity regions. Addition of additives with different polarities in GMO leads to change in phase behavior and related properties of GMO. Effect of the additives with different hydrophilic lipophilic balance (HLB; 1.5, 3, 4, 5, 7, 10 and 11) in GMO matrices on its phase transformation, rheological properties, mechanical properties, wetting and release behavior was investigated. Polarizing light microscopy showed that the GMO matrices incorporated with lower HLB additive (1.5, 3, 4 and 5) form cubic phase at higher rate while lamellar phase was prominent for matrices with additive of HLB 7, 10 and 11. The diametrical crushing strength and viscosity was decreased with increased HLB of additive. Lower HLB additives enhanced contact angle as compared to plain matrices and high HLB additives induced change in solid–liquid interface from hydrophobic to hydrophilic leading to decline in contact angle. Percent swelling of matrices was increased linearly with increase in HLB of additives. Tensiometric method was used for determination of bioadhesive strength of hydrated matrices and it was observed that matrices with additives of HLB 10 presented highest bioadhesion due to higher rate of hydration and formation of lamellar phase. As the HLB of additives in matrix increased, release was shifted from anomalous (non-Fickian) diffusion and/or partially erosion-controlled release to Fickian diffusion. Initial lag was observed for drug released from matrices with additive of HLB 1.5, 3, 4 and 5. Thus incorporation of the additives of different HLB changed molecular packing, which significantly affected drug release pattern.
Keywords: Glyceryl monooleate; Glyceryl mono-stearate; Phase transformation; Diametrical crushing strength; Contact angle; Rheological behavior
Preparation and characterization of free mixed-film of pectin/chitosan/Eudragit® RS intended for sigmoidal drug delivery
by Alireza Ghaffari; Kian Navaee; Mahvash Oskoui; Khosrow Bayati; Morteza Rafiee-Tehrani (pp. 175-186).
Polyelectrolyte complex (PEC) film between pectin as an anionic polyelectrolyte and chitosan as a cationic species was prepared by blending two polymer solutions at weight ratio of 2:1 and then solvent casting method. Besides pectin/chitosan PEC film, Eudragit® RS, pectin/Eudragit® RS and pectin/chitosan/Eudragit® RS films were also prepared by aforementioned method. In mixed-film formulations, a fixed weight ratio of 1:5 of pectin or pectin/chitosan complex to Eudragit® RS was used. Characterizations of pectin/chitosan interaction in solution were investigated by turbidity and viscosity measurement and in the solid state by Fourier transform infrared (FTIR) spectroscopy, wide angle X-ray diffraction (WAXRD) and thermogravimetric analysis (TGA). It was observed that the swelling profile of pectin/chitosan film was pH-dependent and its swelling ratio in phosphate buffer solution (PBS) pH 7.4 was about 2.5-fold higher than that of PBS pH 6.0. Formulation containing only pectin/chitosan could not protect free film from high swelling in the aqueous media, therefore, Eudragit® RS as a water-insoluble polymer must be included in the mixed-film. The formation of PEC between pectin and chitosan resulted in a decrease in the crystallinity and thermal stability caused by the interactions between polyions. Drug permeation or diffusion studies were carried out using Plexiglas diffusion cell consisting of donor and acceptor compartments. Theophylline was selected as a model drug to measure permeability coefficient. Drug permeation through pectin/chitosan/Eudragit® RS showed a sigmoidal pattern; whereas drug diffusion through pectin/Eudragit® RS and Eudragit® RS films followed a linear characteristic. The drug permeation through the ternary mixed-film showed a burst release upon exposure to PBS pH 6.0. This mixed-film formulation showed the potential for sigmoidal drug delivery with an initial, controllable slow release followed by a burst release immediately after the change in pH. The burst drug permeation might possibly be due to change in film’s porosity.
Keywords: Chitosan; Eudragit; ®; RS; Mixed-film; Pectin; Polyelectrolyte complex; Sigmoidal drug delivery
Modulating drug release and matrix erosion of alginate matrix capsules by microenvironmental interaction with calcium ion
by Thaned Pongjanyakul; Satit Puttipipatkhachorn (pp. 187-195).
Effect of calcium gluconate (CG) content on release of dextromethorphan hydrobromide (DMP), model drug, from capsules containing low and medium viscosity grades of sodium alginate (SA) was investigated in different dissolution media. Matrix erosion of the SA matrix capsules in distilled water and pH 7.4 phosphate buffer was compared. Molecular interaction of SA with calcium ion in surface gel layer of the SA matrix capsules was examined using Fourier transform infrared spectroscopy and differential scanning calorimetry. In distilled water and pH 7.4 phosphate buffer, DMP release rate depended on the viscosity grade of SA, whereas a comparable DMP release rate was found in 0.1N HCl. Incorporation of CG into the SA matrix capsules caused a faster drug release in acidic medium because CG acted as a channeling agent in the hydrated insoluble gel matrix of alginic acid. Interaction of calcium ions with carboxyl groups of SA could be formed in surface gel layer of hydrated matrix capsules in distilled water. This led to a more rigid matrix gel structure that caused a slower drug release and matrix erosion. In contrast, the extent of this interaction in pH 7.4 phosphate buffer was less than that in distilled water because the common ion effect and high concentration of sodium ion retarded the hydration of SA and the binding of calcium ions with carboxyl groups of SA. Thus, a small change in drug release and matrix erosion was observed. This finding suggests that microenvironmental interaction between hydrated SA and calcium ion in distilled water could be created in the formulations prepared using low compression force. Moreover, incorporation of CG could moderate drug release and matrix erosion of the SA matrix capsules.
Keywords: Sodium alginate; Molecular interaction; Matrix erosion; Drug release; Capsules
Formulation and development of hydrodynamically balanced system for metformin: In vitro and in vivo evaluation
by Javed Ali; Shweta Arora; Alka Ahuja; Anil K. Babbar; Rakesh K. Sharma; Roop K. Khar; Sanjula Baboota (pp. 196-201).
The objective of the present study was to develop a hydrodynamically balanced system of metformin as a single unit floating capsule. Various grades of low-density polymers were used for the formulation of this system. They were prepared by physical blending of metformin and the polymers in varying ratios. The formulation was optimized on the basis of in vitro buoyancy and in vitro release in simulated fed state gastric fluid (citrate phosphate buffer pH 3.0). Effect of various release modifiers was studied to ensure the delivery of drug from the HBS capsules over a prolonged period. Capsules prepared with HPMC K4M and ethyl cellulose gave the best in vitro percentage release and were taken as the optimized formulation. By fitting the data into zero order, first order and Higuchi model it was concluded that the release followed zero order release, as the correlation coefficient ( R2 value) was higher for zero order release. It was concluded from R2 values for Higuchi model that drug release followed fickian diffusion mechanism. In vivo studies were carried out in rabbits to assess the buoyancy, as well as the pharmacokinetic parameters of the formulation using gamma scintigraphy. The formulation remained buoyant during 5h of study in rabbits. The comparative pharmacokinetic study was performed by administration of the optimized HBS capsules and immediate release capsules, both with radiolabeled metformin, using gamma counter. There was an increase in AUC in optimized HBS capsules of metformin when compared with immediate release formulation.
Keywords: Metformin; Hydrodynamically balanced system; Gastroretention; Gamma scintigraphy
Colonic delivery of compression coated nisin tablets using pectin/HPMC polymer mixture
by Timucin Ugurlu; Murat Turkoglu; Umran Soyogul Gurer; Burcak Gurbuz Akarsu (pp. 202-210).
Nisin containing pectin/HPMC compression coated tablets were prepared and their in vitro behavior tested for colonic delivery. Nisin is a 34-amino-acid residue long, heat stable peptide belonging to the group A lantibiotics with wide antimicrobial activity against Gram-positive bacteria. The invention can be useful for treating colonic infectious diseases such as by Clostridium difficile, and also by colonization of vancomycin-resistant enterococci. In this study, each 100mg core tablet of nisin was compression coated with 100% pectin, 90% pectin–10% HPMC, 85% pectin–15% HPMC, 80% pectin–20% HPMC, 75% pectin–25% HPMC, 100% HPMC at a coat weight of 400mg. The concentration and the activity of nisin were quantified using Well Diffusion Agar Assay. Drug release studies were carried out in pH 3.3 buffer solution. System degradation/erosion experiments were carried out in pH 1.2, 3.3, and 6.8 buffers using a pectinolytic enzyme. The biological activity and NMR studies were performed to assess the stability of nisin during the processing and after the in vitro tests. It was found that pectin alone was not sufficient to protect the nisin containing core tablets. At the end of the 6h 40% degradation was observed for 100% pectin tablets. HPMC addition required to control the solubility of pectin, a 5% increase in HPMC ratio in pectin/HPMC mixture provided a 2-h lag time for nisin release. Eighty percent pectin–20% HPMC appeared to be an optimum combination for further evaluation. Tablets maintained their integrity during the 6-h dissolution test, approximating the colon arrival times. Nisin was found to be active/stable during processing and after in vitro tests. Effect of polymer hydration on pectin degradation was found to be crucial for the enzyme activity. Sufficiently hydrated pectin degraded faster. The pectin/HPMC envelope was found to be a good delivery system for nisin to be delivered to the colon.
Keywords: Colonic delivery; Nisin; Pectin; HPMC; Compression coating; NMR; Well Diffusion Agar Assay
Swelling and erosion of pectin matrix tablets and their impact on drug release behavior
by Pornsak Sriamornsak; Nartaya Thirawong; Yossanun Weerapol; Jurairat Nunthanid; Srisagul Sungthongjeen (pp. 211-219).
The aim of this study was to investigate swelling and erosion behaviors of hydrophilic matrix tablets using pectin and their impact on drug release. The matrix tablets were prepared by direct compression using different types of pectin. Swelling and erosion studies of pectin matrix tablets were carried out in various media. The pectin matrix tablets formed a continuous gel layer while in contact with the aqueous medium undergoing a combination of swelling and erosion. The swelling action of pectin matrices was controlled by the rate of its hydration in the medium. Release studies showed that the swelling and erosion of matrices influenced the drug release. The extent of matrix swelling, erosion and diffusion of drug determined the kinetics as well as mechanism of drug release from pectin-based matrix tablets. The release data showed a good fit into the power law or the Korsmeyer–Peppas equation indicating the combined effect of diffusion and erosion mechanisms of drug release.
Keywords: Pectin; Swelling; Hydration; Erosion; Elastic modulus; Drug release; Matrix tablet
Development of directly compressible powders via co-spray drying
by Y. Gonnissen; J.P. Remon; C. Vervaet (pp. 220-226).
Continuous production of directly compressible powders was achieved by coprocessing acetaminophen and carbohydrates via spray drying. Binary and ternary powder mixtures containing drug substance and carbohydrates were prepared by co-spray drying and evaluated on spray drying processibility, powder hygroscopicity, flowability, and compactability. The influence of process parameters during spray drying on the compaction behaviour of drug/excipient mixtures was investigated via Heckel analysis. Erythritol, lactose, maltodextrin, and mannitol were efficient in co-spray drying with acetaminophen. However, lactose mixtures showed poor flowability. Spray dried mixtures containing mannitol and erythritol were characterised as non-hygroscopic, highly dense, and good flowing powders. Mannitol increased tablet tensile strength in contrast with the poor compactability of erythritol. Maltodextrin was selected for further experiments because it provided excellent tablet tensile strength. The use of erythritol, maltodextrin and mannitol in binary drug/excipient mixtures resulted in high process yields. Compacts of erythritol, mannitol, and maltodextrin were characterised by higher tablet tensile strength at higher spray drying temperatures due to the increased particle fragmentation of erythritol and mannitol mixtures and to the increased plastic deformation of maltodextrin formulations. A combination of erythritol, maltodextrin, and mannitol was selected for further formulation and process optimisation of co-spray dried powders for direct compression.
Keywords: Coprocessing; Spray drying; Compression; Acetaminophen; Carbohydrates
Alginate-based pellets prepared by extrusion/spheronization: A preliminary study on the effect of additive in granulating liquid
by Pornsak Sriamornsak; Jurairat Nunthanid; Manee Luangtana-anan; Satit Puttipipatkhachorn (pp. 227-235).
The aim of this study was to investigate the possibility of producing alginate-based pellets by extrusion/spheronization and also to improve the formation of spherical alginate-based pellets by investigating the effect of additive in granulating liquid on characteristics and drug release from resulting pellets. Two types of sodium alginate (30%) were evaluated in combination with theophylline (20%), microcrystalline cellulose (50%) and different granulation liquids. The pellets were then prepared in a basket extruder, then spheronized and dried. The final products were characterized by morphological examination and drug release study. Different additives in the granulating liquid influenced the ability of the extruded mass to form pellets (the processability) with this technique. However, different sodium alginate types responded to shape modifications to a different extent. Long, dumbbell-shaped pellets were obtained with viscous granulating liquids. However, short, nearly spherical pellets were obtained with watery granulation liquid with calcium chloride that reduced the swelling ability of sodium alginate. Improvements in the pellet characteristics were also dependent on the sodium alginate type employed. Most of pellet formulations released about 75–85% drug within 60min and showed a good fit into both Higuchi and Korsmeyer–Peppas equations. Higher amount of 3% calcium chloride, as a granulating liquid, in the formulation showed higher mean dissolution time resulting from the cross-linking properties of calcium ions to the negative charges of alginate molecules.
Keywords: Alginate; Granulating liquid; Pellets; Extrusion; Basket extruder; Spheronization
Microstructural and drug release properties of oven-dried and of slowly or fast frozen freeze-dried MCC-Carbopol® pellets
by Ana Gómez-Carracedo; Consuelo Souto; Ramón Martínez-Pacheco; Angel Concheiro; José Luis Gómez-Amoza (pp. 236-245).
The influence of the procedure and conditions of drying (oven-drying and freeze-drying after slow or fast freezing) and of the CaCl2 concentration in the wetting liquid on the physical characteristics and drug release behaviour of microcrystalline cellulose (MCC)-carbopol 40:60 pellets containing theophylline or ketoprofen has been evaluated. The microstructural, morphological and mechanical properties can be modulated, to a large extent, through the control of the drying step and the CaCl2 proportion. The drying step determines the volumetric contraction of the pellets and, consequently, the porosity parameters. When freeze-drying is applied, the freezing conditions have a marked influence on total porosity and mean pore size of the pellets. Slowly frozen pellets present the lowest porosity but the pores are the greatest. Pore size appears as a critical factor for achieving controlled release; the greater the pores, the faster the entrance of water and, consequently, the drug release. Therefore, if freeze-drying is used to remove water from wet pellets, the control of the ice formation is essential to modulate the release profiles. The practical possibilities of such modulation are especially clear for a slightly-water soluble drug, such as ketoprofen.
Keywords: Extrusion-spheronization; Freeze-drying; Pellets; Modified release; Mercury porosimetry
Phase transformations of erythromycin A dihydrate during pelletisation and drying
by Meike Römer; Jyrki Heinämäki; Inna Miroshnyk; Niklas Sandler; Jukka Rantanen; Jouko Yliruusi (pp. 246-252).
An at-line process analytical approach was applied to better understand process-induced transformations of erythromycin dihydrate during pellet manufacture (extrusion–spheronisation and drying process). The pellets contained 50% (w/w) erythromycin dihydrate and 50% (w/w) microcrystalline cellulose, with purified water used as a granulating fluid. To characterise changes in solid-state properties during processing, near infrared (NIR) spectroscopy and X-ray powder diffraction (XRPD) were applied. Samples were taken after every processing step (blending, granulation, extrusion, and spheronisation) and at predetermined intervals during drying at 30 or 60°C. During pelletisation and drying at 30°C no changes occurred. Partial transformation to the dehydrated form was observed for the pellets dried at 60°C by NIR and XRPD. The variable temperature XRPD measurements of the wet pellets (from 25 to 200°C) also confirmed the change to erythromycin dehydrate at approximately 60°C.
Keywords: Processing induced transformation; Erythromycin; Dehydration; NIR; XRPD; Pelletisation; Drying
Formulation and evaluation of dried yeast tablets using different techniques
by Abdullah M. Al-Mohizea; Mahrous O. Ahmed; Fahad I. Al-jenoobi; Gamal M. Mahrous; Aly A. Abdel-Rahman (pp. 253-259).
The aim of this study was to prepare and evaluate dried yeast tablets using both direct compression and dry granulation techniques in comparison with the conventional wet granulation as well as commercial product. Wet granulation technique is not favorable for producing the yeast tablets due to the problems of color darkening and the reduction of the fermentation power of the yeast as a result of the early start of the fermentation process due to the presence of moisture. Twenty six formulae of dried yeast tablets were prepared and evaluated. Certain directly compressible vehicles were employed for preparing these tablets. The quality control tests (weight uniformity, friability, disintegration time and hardness) of the prepared dried yeast tablets were performed according to B.P. 1998 limits. All batches of the prepared tablets complied with the B.P. limits of weight uniformity. Moreover, small values of friability % (1% or less) were obtained for all batches of dried yeast tablets with acceptable hardness values, indicating good mechanical properties which can withstand handling. On the other hand, not all batches complied with the limit of disintegration test which may be attributed to various formulation component variables. Therefore, four disintegrating agents were investigated for their disintegrating effect. It was found that the method of preparation, whether it is direct compression, dry granulation or wet granulation, has an effect on disintegration time of these dried yeast tablets and short disintegration times were obtained for some of the formulae. The shortest disintegration time was obtained with those tablets prepared by direct compression among the other techniques. Therefore, the direct compression is considered the best technique for preparation of dried yeast tablets and the best formula (which showed shorter disintegration time and better organoleptic properties than the available commercial yeast tablets) was chosen. Drug content for dried yeast granular powder, and the chosen best prepared formula, was determined by gas chromatography (GC). It was found that this formula gave the same alcohol content produced by an equal amount of the dried yeast granular powder. This result in conjunction with weight uniformity indicated drug content uniformity of the prepared dried yeast tablets.
Keywords: Yeast; Direct compression; Wet granulation; Dry granulation; Formulation; Tablets
Thermal treating as a tool to produce plastic pellets based on Eudragit RS PO and RL PO aimed for tableting
by M.R. Abbaspour; F. Sadeghi; H. Afrasiabi Garekani (pp. 260-267).
A 32 full-factorial design was used for preparation of pellets using extrusion–spheronization technique. Independent variables were %ibuprofen (40, 60, 80) and %Eudragit RS PO/RL PO (0, 50, 100). In all formulations 3% w/w PVP K30 and 10% Avicel PH101 were also used. The pellets were cured in oven at 60°C for 24h. The evaluated responses were crushing strength or yield point, elastic modulus and mean dissolution time (MDT) of pellets. The cured pellets were also compressed at 15kN compaction force and then observed under scanning electron microscope.It was shown that the cured pellets containing 40% or 60% drug exhibited a plastic deformation without any fracture under mechanical tests. The curing process resulted in significant decrease in the elastic modulus of the pellets. The SEM of the compressed pellets were also confirmed the plastic behavior of these pellets. The transition of pellet behavior from brittle to plastic upon curing was due to shift of Eudragit structure from glassy to rubbery state which was supported by DSC studies. However pellets with 80% drug showed brittle properties even after curing due to presence of less amount of Eudragit in their structure. Increasing the ratio of Eudragit RS in the pellets decreased the yield point and elastic modulus of cured pellets containing 40% or 60% drug, indicating more plastic behavior of these pellets. This was attributed to lower Tg of Eudragit RS than Eudragit RL.The curing process also retarded drug release from pellets and increased MDT. Increasing the ratio of Eudragit RS in the pellets increased MDT in cured pellets containing 40% or 60% drug but had no effect in pellets with 80% drug.Overall the results of this study revealed that thermal treating is a proper tool to produce plastic ibuprofen pellets based on Eudragit RS PO and Eudragit RL PO.
Keywords: Pellet; Extrusion–spheronization; Ibuprofen; Eudragit RS PO; Eudragit RL PO; Curing; Mechanical properties
The determination of the mechanical strength of tablets of different shapes
by Peter N. Davies; Harry E.C. Worthington; Fridrun Podczeck; J. Michael Newton (pp. 268-276).
The aim of the study was to investigate the influence of the platen design, on the evaluation of the mechanical strength of tablets of different shapes in terms of the potential of ensuring reproducible failure mechanisms and deriving their tensile strength. Tablets which were circular, square or hexagonal in shape were prepared at a range of formation pressures each from microcrystalline cellulose (Avicel PH102), a direct compression anhydrous β-lactose (DCL 21) and dicalcium phosphate dihydrate (Emcompress) with a reciprocating single punch tablet machine. The mechanical strength of the tablets has been determined with a three-point bending test and by applying a diametral load across the edges of the tablets with platens of different designs. Many of the tablets tested in three-point bending did not fail in tension. However, with platens to which semi-circular rods of radius 3.0mm were attached and vertically aligned, a test procedure was provided with which a wide range of tablets tested failed in tension, i.e., split into two halves. Where this occurred it was possible to calculate the tensile strength from the breaking load. Although the value of the tensile strength obtained with such platens was generally lower than that obtained for circular tablets when flat platens were used, the ability to be able to use this new configuration for all the tablet shapes provided a practical system for a range of tablet shapes. The tablets of the three shapes tested here were found to have equivalent values for the tensile strength when formed at the same compaction pressure for the three materials tested.
Keywords: Diametral compression; Mechanical strength; Tensile failure; Platen design
Mechanical characterization of pharmaceutical solids: A comparison between rheological tests performed under static and dynamic porosity conditions
by Giulia Bonacucina; Marco Cespi; Monica Misici-Falzi; Giovanni F. Palmieri (pp. 277-283).
The aim of this work was to verify how and to what extent rheological tests, carried out under dynamic (Heckel) and static (creep, stress/strain) porosity conditions, may serve as a valuable complement to the classic Heckel tests in the characterization of viscoelastic and densification properties of solid materials for pharmaceutical use.Six different modified (pregelatinized) starches were compressed in a rotary tablet machine equipped to measure force and punch displacement. Tablets were obtained using flat-faced 6mm diameter punches at different compression pressures. Compression cycles performed at the maximal pressure of 200MPa were used to build the Heckel plots. Ejected tablets at the 10%, 20%, 30%, and 40% porosity levels were used for the stress/strain and creep tests.Parameters obtained with both types of tests were consistent with each other. In particular, among the six starches, lower viscosity values corresponded to lower P Y values, and lower elastic modulus values corresponded to lower elastic recovery of the tablet.Mechanical properties of materials can be better characterized if viscoelastic tests performed under dynamic porosity conditions (Heckel analysis) are supported by classical viscoelastic tests carried out under conditions of static porosity.
Keywords: Mechanical properties; Rheology; Viscosity; Elasticity; Retardation time; Compression
Functional characterization of cell lines for high-throughput screening of human neuromedin U receptor subtype 2 specific agonists using a luciferase reporter gene assay
by Xinping Li; Fuwen Shen; Yuwu Zhang; Jiang Zhu; Lu Huang; Qunfang Shi (pp. 284-292).
We developed a functional cell-based high-throughput screening (HTS) assay to identify modulators of the human neuromedin subtype 2 receptor. This assay utilized the signal transduction pathway of hNMU2R, which is positively coupled to adenylyl cyclase and downstream calcium signal pathways. We describe in detail a robust, sensitive, and functional assay for the hNMU2R G-protein-coupled receptor expressed in human embryonic kidney (HEK)-293 cells, whose activity was reflected by a luciferase reporter gene transcriptionally regulated by a 3-repeat serum response element (SRE)-3 repeat multiple response element (MRE)-3 repeat cyclic AMP (cAMP) response element (CRE)-VIP mini promoter. The HEK 293 clonal cell line, stably co-transfected with the 3×SRE/3×MRE/3×CRE/VIP mini promoter-driven luciferase and pCDNA3.1-NMU2R plasmid, was selected by active geneticin sulfate and their ability to express luciferase with a forskolin challenge following hNMU plus forskolin, known to activate intracellular signal transduction. Then the cell density, incubation time, dimethyl sulfoxide (DMSO) concentration used to screen the hNMU receptor subtype 2 specific agonist were optimized, and whether intrinsic luminescent substance of extracts isolated from traditional Chinese herbs disturbs luminescence of luciferase expressed in HEK293 cells was considered. The optimal incubation time was found to be between 8 and 9h, the cell density and DMSO concentrations were optimized from 3×104 to 6×104, and less than 2%, respectively. Our data show that hNMU2R luci-HEK293 cells and their assay exhibit a low background and ideal model for high-throughput screening. These results demonstrate that this reporter gene assay is useful for pharmacological analysis, and is amenable to HTS for human NMU2R agonists.
Keywords: NMU2 receptor; Reporter gene; Luciferase; G-protein-coupled receptor; Cell-based assay; Traditional Chinese herbs
Handling of computational in vitro/in vivo correlation problems by Microsoft Excel: V. Predictive absorbability models
by Frieder Langenbucher (pp. 293-299).
This paper discusses Excel applications related to the prediction of drug absorbability from physicochemical constants. PHDISSOC provides a generalized model for pH profiles of electrolytic dissociation, water solubility, and partition coefficient. SKMODEL predicts drug absorbability, based on a log–log plot of water solubility and O/W partitioning; augmented by additional features such as electrolytic dissociation, melting point, and the dose administered. GIABS presents a mechanistic model of g.i. drug absorption. BIODATCO presents a database compiling relevant drug data to be used for quantitative predictions.
Keywords: IVIVC; QSAR; Excel; Access; Absorption potential; Biopharmaceutics Classification System; BCS; Prediction; Solubility; Partitioning; Dissociation; pH profile; Database