International Journal of Pharmaceutics (v.383, #1-2)
Editorial Board (iii).
Solid self-emulsifying nitrendipine pellets: Preparation and in vitro/in vivo evaluation by Zhiyuan Wang; Jin Sun; Yongjun Wang; Xiaohong Liu; Yanhua Liu; Qiang Fu; Ping Meng; Zhonggui He (1-6).
Objective of this study is to develop and evaluate the new solid self-emulsifying (SE) pellets of poorly soluble nitrendipine (NTD). These pellets were prepared via extrusion/spheronization technique, using liquid SEDDS (NTD, Miglyol® 812, Cremophor® RH 40, Tween 80, and Transcutol® P), adsorbents (silicon dioxide and crospovidone), microcrystalline cellulose and lactose. The resulting SE pellets with 30% liquid SEDDS exhibited uniform size (800–1000 μm) and round shape, droplet size distribution following self-emulsification was nearly same to the liquid SEDDS (72 ± 16 nm and 64 ± 12 nm). The in vitro release was similar for the two SE formulations (over 80% within 30 min), both significantly higher than the conventional tablets (only 35% within 30 min). The oral bioavailability was evaluated for the SE pellets, liquid SEDDS and conventional tablets in fasted beagle dogs. AUC of NTD from the SE pellets showed 1.6-fold greater than the conventional tablets and no significant difference compared with the liquid SEDDS. In conclusion, our studies illustrated that extrusion/spheronization technique could be a useful large-scale producing method to prepare the solid SE pellets from liquid SEDDS, which can improve oral absorption of NTD, nearly equivalent to the liquid SEDDS, but better in the formulation stability, drugs leakage and precipitation, etc.
Keywords: Solid self-emulsifying drug delivery systems; Pellets; Extrusion/spheronization; Nitrendipine; Oral bioavailability;
Effect of liposome size on peritoneal retention and organ distribution after intraperitoneal injection in mice by N. Mirahmadi; M.H. Babaei; A.M. Vali; S. Dadashzadeh (7-13).
Peritoneal carcinomatosis is a serious concern when treating digestive or ovarian tumors. Treatment with systemic chemotherapy suffers from poor penetration of cytotoxic agents into the peritoneal cavity and is not quite effective. Local delivery of drugs, especially as controlled-release delivery systems like liposomes, could provide sustained and higher drug levels and reduce systemic toxicity.In order to investigate the effect of liposome size on peritoneal retention, liposomes composed of distearoylphosphatidylcholine and cholesterol (DSPC/CHOL, molar ratio 2:1) were prepared at four sizes of 100, 400, 1000 and 3000 nm. Subsequently, these liposomes were labeled with 99mTc complex of hexamethylpropyleneamineoxime (99mTc-HMPAO) and injected into mouse peritoneum. Then, mice were sacrificed at eight different time points and the percentage of injected radiolabel in the peritoneal cavity and the organ distribution in terms of percentage injected dose/gram tissue (%ID/g) were obtained.Results showed that the free label (99mTc-HMPAO) was cleared very rapidly from the cavity so that after 5 min and 7 h only 6.89 ± 2.51% and 0.91 ± 0.51% of the injected dose was recovered, respectively. However, for the liposomal formulations, this recovery value ranged from 8.47 ± 1.62% to 29.99 ± 12.06% at 7 h. Peritoneal retention of the vesicles was increased with their size, and the highest retention rate was obtained with 1000 nm liposomes with an AUC value 15.51 times that of 99mTc-HMPAO. In blood, as expected, 100 nm liposomes showed much higher levels because of their greater stability. Their greater blood concentration also caused increased levels in the heart and kidneys, although their organ to blood AUC ratio was the lowest.Overall, among the different sized neutral liposomes investigated, the 1000 nm vesicles seemed to be the most optimal, achieving a greater peritoneal level and retention.
Keywords: Liposomes; Size; 99mTc-HMPAO; Peritoneal retention; Peritoneal carcinomatosis;
Analysis of skin penetration of phytosphingosine by fluorescence detection and influence of the thermotropic behaviour of DPPC liposomes by Amra Hasanovic; Sonja Hoeller; Claudia Valenta (14-17).
Phytosphingosine (PS) is a promising compound in skin formulations, considering its application in the treatment of acne and different inflammations as well as in the ‘anti age’ cosmetics. PS, as an active substance was incorporated in DPPC liposomes intended to standard diffusion experiments, where dermatomed porcine skin was mounted in FRANZ cells. The proved skin retention was about 5.5% (w/w) after 24 h and about 6.8% (w/w) after 48 h of the applied PS amount, whereas only about 0.05% (w/w) and about 0.07% (w/w) PS, respectively, could be observed in the acceptor medium. To increase analytical sensitivity PS was derivatised by o-phtalaldehyde (OPA) reagent and analysed by HPLC with fluorescence detection. The higher amount of PS within the skin symbolised an interaction with lipid structures in skin. Further evaluation of this interaction was accomplished by applying microDSC studies of PS with DPPC as a model membrane. For this purpose liposomes were prepared by increasing PS content. The characteristic endothermic peak observed for the single system was shifted to a slightly higher temperature and broadened as the mole fraction of PS increased. This might be the effect of mixing of PS with DPPC. An addition of 10 mol% PS resulted in more than double sized particles pointing to a possible change in the liposomal shape.
Keywords: DPPC liposomes; Phytosphingosine; DSC; OPA-reagent;
Prediction of recrystallization behavior of troglitazone/polyvinylpyrrolidone solid dispersion by solid-state NMR by Atsutoshi Ito; Tomoyuki Watanabe; Shuichi Yada; Takeshi Hamaura; Hiroaki Nakagami; Kenjirou Higashi; Kunikazu Moribe; Keiji Yamamoto (18-23).
The purpose of this study was to elaborate the relationship between the 13C CP/MAS NMR spectra and the recrystallization behavior during the storage of troglitazone solid dispersions. The solid dispersions were prepared by either the solvent method or by co-grinding. The recrystallization behavior under storage conditions at 40 °C/94% RH was evaluated by the Kolmogorov–Johnson–Mehl–Avrami (KJMA) equation. Solid dispersions prepared by the solvent method or by prolonged grinding brought about inhibition of the nucleation and the nuclei growth at the same time. No differences in the PXRD profiles were found in the samples prepared by the co-grinding and solvent methods, however, 13C CP/MAS NMR showed significant differences in the spectra. The correlation coefficients using partial least square regression analysis between the PXRD profiles and the apparent nuclei-growth constant or induction period to nucleation were 0.1305 or 0.6350, respectively. In contrast, those between the 13C CP/MAS NMR spectra and the constant or the period were 0.9916 or 0.9838, respectively. The 13C CP/MAS NMR spectra had good correlation with the recrystallization kinetic parameters evaluated by the KJMA equation. Consequently, solid-state NMR was judged to be a useful tool for the prediction of the recrystallization behavior of solid dispersions.
Keywords: Solid dispersion; Physical stability; Solid-state NMR; Recrystallization; Partial least squares regression;
Caco-2 cell monolayers as a tool to study simultaneous phase II metabolism and metabolite efflux of indomethacin, paracetamol and 1-naphthol by Sanna Siissalo; Laura Laine; Ari Tolonen; Ann M. Kaukonen; Moshe Finel; Jouni Hirvonen (24-29).
The human intestinal cell line, Caco-2, was used to study compounds – indomethacin, paracetamol and 1-naphthol – that undergo intestinal phase II metabolism followed by apical and/or basolateral efflux of the metabolites and/or parent compounds. The interplay was studied during permeability experiments across fully differentiated Caco-2 cell monolayers. The parent compounds and their glucuronide and/or sulfate metabolites were detected by LC–MS/MS. Conjugation of the model compounds and effluxes of their metabolites were observed. The efflux of indomethacin glucuronide was apical, but complementary basolateral efflux was observed at the highest indomethacin concentration (500 μM), probably due to apical saturation. Paracetamol glucuronide was not formed in these experiments, but apical and basolateral effluxes of paracetamol sulfate were observed. A typical bell-shaped inhibition curve was observed for the formation of 1-naphthol glucuronides, indicating substrate or product inhibition of the UGT enzyme(s) at higher 1-naphthol concentrations (200 μM and 500 μM). Based on these results, the fully differentiated Caco-2 cell monolayers can be applied as a platform for qualitative in vitro studies, where phase II metabolism and efflux activities are ongoing simultaneously.
Keywords: Caco-2 cells; Efflux; Phase II metabolism; Glucuronidation; Sulfation; In vitro method;
A novel gastric-resident osmotic pump tablet: In vitro and in vivo evaluation by Jin Guan; Liying Zhou; Shufang Nie; Tingxu Yan; Xin Tang; Weisan Pan (30-36).
A novel famotidine gastric-resident osmotic pump tablet was developed. Pharmaceutical iron powder was used as a gas-formation and density-increasing agent. Central composite design-response surface methodology was used to investigate the influence of factors, i.e., polyethylene oxide (Mw 1,000,000) content, NaCl content, iron powder content and weight gain, on the responses including ultimate cumulative release and correlation coefficient of drug release profile. A second-order polynomial equation was fitted to the data and actual response values are in good accordance with the predicted ones. The optimized formulation displays a complete drug delivery and zero-order release rate. Gamma scintigraphy was selected as the method to monitor in vivo gastric residence time of the 99mTc-labeled system in Beagle dogs. It was observed that the system can retain in stomach for an extended period of 7 h after administration compared with conventional tablets. The present investigation suggests that water-insoluble drug can be delivered from single-layer osmotic pump tablets completely due to the push power of the hydrogen gas generated by the reaction of the iron and gastric fluid. And iron powder can increase the system density which is over 2.5 g cm−3, making the system resident in stomach to prolong the drug delivery time in absorption zone.
Keywords: Gastric-resident osmotic pump tablet; Pharmaceutical iron powder; Central composite design; Gamma scintigraphy; Famotidine;
Comparison of anti-tumor efficacy of paclitaxel delivered in nano- and microparticles by Sudhir S. Chakravarthi; Sinjan De; Donald W. Miller; Dennis H. Robinson (37-44).
This research compares the anti-tumor efficacy of paclitaxel delivered intratumorally in PLGA nanoparticles, microparticles, or the commercial Paclitaxel Injection®. The hypothesis of the research is that larger PLGA microparticles adhere to mucus on the cell surface, release paclitaxel locally, and enhance cellular association of paclitaxel. PLGA-paclitaxel particles of mean diameters 315 nm, 1 μm, and 10 μm were prepared and their drug content, in vitro release, and cellular association of paclitaxel into 4T1 cells quantified. These particles were injected intratumorally into tumor xenografts, and the tumor volumes monitored over 13 days. Mean tumor volumes of the groups that received placebo and the 315 nm nanoparticles increased 2 and 1.5 times, respectively. Tumor growth was arrested in groups that received 1 μm and 10 μm microparticles. Additional cell culture studies were performed to test the hypothesis. The size-dependent increase in cellular concentration of paclitaxel was independent of duration of incubation of PLGA particles with 4T1 cells, and was enhanced 1.5 times by coating the particles or 4T1 cells with mucin. These particles were not internalized by clathrin-mediated endocytosis or macropinocytosis. In conclusion, PLGA microparticles sustained drug release, increased cellular concentration, and enhanced anti-tumor efficacy of paclitaxel compared to nanoparticles and Paclitaxel Injection®.
Keywords: PLGA; Paclitaxel; Cellular association; Nanoparticles; Microparticles;
A new bioerodible system for sustained local drug delivery based on hydrolytically activated in situ macromolecular association by Yan Li; Ping I. Lee (45-52).
To prolong the duration of polymer erosion over existing approaches for sustained local drug delivery, we investigated a new bioerodible system based on hydrolytically activated in situ formation of interpolymer complexes in binary blends of high MW poly(vinyl methyl ether-co-maleic anhydride) (PVMMA) and poly(ethylene oxide) (PEO). In an aqueous environment of use, the hydrophobic PVMMA component of the blend undergoes hydrolysis converting the anhydride to free carboxylic acid groups which in turn form in situ intermolecular complexes with the PEO component of the blend. The formation of such hydrogen-bonded complexes with a condensed structure at the blend surface helps to retard the further progression of polymer erosion and drug release. The effects of PVMMA/PEO composition on blend morphology, polymer erosion and drug release were evaluated with the aid of fluorescence labeled PVMMA. The results show a decrease in miscibility in PVMMA/PEO blend with increasing PEO content. At low PEO contents (below 40%), the in vitro rate of release of a model drug metronidazole decreases with increasing PEO content, resulting in extended release duration over several days. On the other hand, excessive phase separation at PEO contents above 40% gives rise to higher rate and shorter duration of drug release.
Keywords: Sustained drug delivery; Poly(vinyl methyl ether-co-maleic anhydride); Poly(ethylene oxide); In situ macromolecular association; Bioerodible polymers;
Hydrogels of N-isopropylacrylamide copolymers with controlled release of a model protein by Nikola Milašinović; Melina Kalagasidis Krušić; Zorica Knežević-Jugović; Jovanka Filipović (53-61).
Temperature- and pH-sensitive hydrogels, based on N-isopropylacrylamide (NiPAAm) and itaconic acid (IA), were synthesized by free radical crosslinking copolymerization in the presence of lipase from Candida rugosa. The samples were characterized for their sensitivity to the changes of external conditions and the ability to control the release of a hydrophilic model protein, lipase. These hydrogels were highly responsive to temperature and pH, at constant ionic strength. Parameters, such as the crosslinking degree and non-ionic/ionic (NiPAAm/IA) ratio, were found to impact the hydrogel structure, mechanical properties, morphology and swelling kinetics at different pH and temperatures. The hydrogels demonstrated protein loading efficiency as high as 95 wt%. Release studies of a hydrophilic model protein at a physiological temperature of 37 °C were performed at different pH values. High dependence of lipase release kinetics on hydrogel structure and the environmental pH was found, showing generally low release rates, lower in acidic media (pH 2.20) and higher at higher pHs (6.80). Lipase activity was retained even after treatment conditions that would provoke denaturation of the enzyme if it was not protected in the gel. The obtained hydrogels were found suitable for releasing therapeutic proteins in a controlled manner at specific sites in gastrointestinal tract.
Keywords: N-Isopropylacrylamide; Itaconic acid; Environment-sensitive hydrogels; Candida rugosa lipase; Controlled protein release; Release kinetics;
Magnesium stearate increases salbutamol sulphate dispersion: What is the mechanism? by Tracy Tay; Shyamal Das; Peter Stewart (62-69).
The objective was to understand the mechanism of enhancement in salbutamol sulphate (SS) respiratory deposition through addition of magnesium stearate (MgSt). The mixing of MgSt with micronized SS occurred using a Turbula mixer (101 rpm), whilst varying mixing time and MgSt concentration and size. Deposition of SS was determined by a twin-stage impinger. Particle size distributions were obtained using the Malvern Mastersizer 2000. Morphology was examined by scanning electron microscopy and surface energy determined using inverse gas chromatography. Mixing of SS with increasing concentrations of MgSt improved dispersion (FPF of 3.3% using 1% w/w MgSt, 4.5% using 5% w/w MgSt and 7.8% using 10% w/w MgSt compared with 1.4% of pure SS for 20 mg doses) when mixed for 0.5 h; SS dispersion improved further after 3.5 h of mixing. In addition to the action of the MgSt in coating SS particles, a greater understanding of the function of MgSt particles in acting as micro-carriers and in changing the mixture structure through incorporation into agglomerates has been achieved. The mechanistic understanding of improvement in drug deposition using MgSt will allow more directed strategies to be employed in designing powder formulations for inhalation.
Keywords: Respiratory delivery; Magnesium stearate; Force control agents; Mechanisms of dispersion; Surface energy;
Prediction of drug particle size and content uniformity in low-dose solid dosage forms by Chien-Yueh Huang; M. Sherry Ku (70-80).
Drug particle size distribution has a profound impact to the content uniformity in low-dose solid drug products. We derived theoretically the skewness of potency distribution as a function of particle size distribution and target dose. It was demonstrated that both skewness and coefficient of variation diverge simultaneously with inverse square root of the target dose. This scaling relation was observed in recent experiment and was verified by Monte Carlo (MC) simulation, which was employed for the first time to solve for the full potency distribution from a random retrieving model. When tested against the criteria from USP 〈905〉 uniformity of dosage units, MC simulation showed a striking anisotropic distribution of the data. This suggests a full-scale consideration of the potency distribution is necessary for evaluating the impacts from particle size distribution and the dose, as compared against the normality assumption used before. A nomograph of the median particle size and the dose that meets a 99% pass rate was constructed for the specification of particle size or the lowest dose limit. Furthermore, we showed quantitatively the lowest dose limit can be drastically reduced if a cut-off size is imposed by removing oversized particles.
Keywords: Content uniformity; Particle size; Low-dose drugs; Monte Carlo; Mixing; Blending; Poisson distribution;
Optimization of PLG microspheres for tailored drug release by N.S. Berchane; F.F. Jebrail; M.J. Andrews (81-88).
Here we explore the opportunity to design and then produce tailored release of therapeutic drugs from microcapsules. By use of “building blocks,” formed from well characterized microcapsule populations, an inverse design algorithm has been developed that provides an optimal (in a least squares sense) combination of building blocks to achieve a desired release history. Previously we have reported experiments and a well validated mathematical model for computing drug release histories from PLG microcapsules, and these form the backbone of the present optimization algorithm. To expand our available basis for finding useful optimal solutions, we also report work to validate the mathematical model for two different molecular weights. Thus, our building blocks comprise populations that differ by microsphere mean diameter, polydispersity, and polymer molecular weight, giving three separate parameters that effect drug release rate, and from which we build a foundation for our tailored release. Here we have taken a basis of six different microcapsule release systems, from which we build a tailored release history using constrained optimization to fit a prescribed release profile. Comparison of predicted release with measurements from the tailored microcapsule populations was found to produce excellent results, with correlation coefficients greater than 0.98. By way of demonstration, a triple pulse design is described that illustrates the power of the method.
Keywords: Controlled release; Poly(lactide-co-glycolide); Non-uniform microspheres; Tailored release; Constrained optimization;
Chemical enhancer solubility in human stratum corneum lipids and enhancer mechanism of action on stratum corneum lipid domain by Sarah A. Ibrahim; S. Kevin Li (89-98).
Previously, chemical enhancer-induced permeation enhancement on human stratum corneum (SC) lipoidal pathway at enhancer thermodynamic activities approaching unity in the absence of cosolvents (defined as Emax) was determined and hypothesized to be related to the enhancer solubilities in the SC lipid domain. The objectives of the present study were to (a) quantify enhancer uptake into SC lipid domain at saturation, (b) elucidate enhancer mechanism(s) of action, and (c) study the SC lipid phase behavior at Emax. It was concluded that direct quantification of enhancer uptake into SC lipid domain using intact SC was complicated. Therefore a liposomal model of extracted human SC lipids was used. In the liposome study, enhancer uptake into extracted human SC lipid liposomes (EHSCLL) was shown to correlate with Emax. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC) were used to evaluate lipid phase alterations in enhancer-treated intact SC. IR spectra demonstrated an increase in the lipid domain fluidity and DSC thermograms indicated a decrease in the phase transition temperature with increasing Emax. These results suggest that the enhancer mechanism of action is through enhancer intercalation into SC intercellular lipids and subsequent lipid lamellae fluidization related to enhancer lipid concentration.
Keywords: Chemical enhancers; Transdermal; Extracted human stratum corneum lipids; DSC and ATR-FTIR;
Dosage form design and in vitro/in vivo evaluation of cevimeline extended-release tablet formulations by Shinichiro Tajiri; Taro Kanamaru; Kamada Makoto; Tsutomu Konno; Hiroaki Nakagami (99-105).
The objective of the present work is to develop an extended-release dosage form of cevimeline. Two types of extended-release tablets (simple matrix tablets and press-coated tablets) were prepared and their potential as extended-release dosage forms were assessed. Simple matrix tablets have a large amount of hydroxypropylcellulose as a rate-controlling polymer and the matrix is homogeneous throughout the tablet. The press-coated tablets consisted of a matrix core tablet, which was completely surrounded by an outer shell containing a large amount of hydroxypropylcellulose. The simple matrix tablets could not sustain the release of cevimeline effectively. In contrast, the press-coated tablets showed a slower dissolution rate compared with simple matrix tablets and the release curve was nearly linear. The dissolution of cevimeline from the press-coated tablets was not markedly affected by the pH of the dissolution medium or by a paddle rotating speed over the range of 50–200 rpm. Furthermore, cevimeline was constantly released from the press-coated tablets in the gastrointestinal tract and the steady-state plasma drug levels were maintained in beagle dogs. These results suggested that the designed PC tablets have a potential for extended-release dosage forms.
Keywords: Extended-release tablets; Cevimeline; Press-coated tablets; Hydroxypropylcellulose;
Propranolol–magnesium aluminum silicate complex dispersions and particles: Characterization and factors influencing drug release by Sarasit Rojtanatanya; Thaned Pongjanyakul (106-115).
In this study, complexation of magnesium aluminum silicate (MAS) and propranolol HCl (PPN) in the form of dispersions and solid particles was investigated. PPN–MAS dispersions at different pHs were prepared and characterized. The physicochemical properties and in vitro drug release of the complexes were also examined. Incorporation of PPN into MAS dispersions at various pHs caused the formation of PPN–MAS flocculates with a different particle size, zeta potential and amount of PPN adsorbed. The PPN–MAS complexes prepared at various pHs were formed via cation exchange, hydrogen bonding and water bridging mechanisms, which were revealed by FTIR and solid-state 29Si NMR spectroscopy. This led to the intercalation of PPN molecules into the silicate layers of MAS. In vitro drug release studies demonstrated that the kinetic release of PPN can be described using the particle diffusion controlled mechanism, suggesting that drug release was controlled by diffusion of the drug in aqueous channels in the particle matrix of the complexes. The PPN–MAS complexes provided a sustained-release of PPN after an initial burst release in acidic medium and pH 6.8 phosphate buffer when compared with the physical mixture and pure PPN powder. This was due to a slow diffusion of drug that was intercalated in the inside of the particle matrix. The preparation pH of the complexes did not influence the release of PPN; the important factors affecting drug release were particle size, percentage of drug loaded in the complexes and the type of release medium. This finding suggests that the PPN–MAS complexes obtained in this study are strong candidates for use as drug carriers in oral modified-release dosage forms.
Keywords: Propranolol; Magnesium aluminum silicate; Complexes; Drug release; Molecular interaction;
In vitro assessment of liposomal neridronate on MDA-MB-231 human breast cancer cells by Imène Chebbi; Evelyne Migianu-Griffoni; Odile Sainte-Catherine; Marc Lecouvey; Olivier Seksek (116-122).
Bisphosphonates have been used for decades in the standard therapy of bone-related diseases, including bone metastasis of various malignancies, and they might as well be toxic on early cancer cells themselves. In order to allow a better delivery of neridronate (a N-containing bisphosphonate with relatively poor activity), liposomes were evaluated in vitro on cancer cell lines (MDA-MB-231, U87-MG and Caco2). After chemical synthesis, this water-soluble molecule was encapsulated into liposomes containing DOPC:DOPG:Chol (72:27:1 molar ratio). The influence of neridronate (free or liposomal) on cell viability or proliferation after treatment was evaluated using the MTT method, as well as cell migration and invasion assays; these techniques showed a drastic improvement of the action of neridronate on MDA-MB-231 cells with an EC50 50 times lower when neridronate was encapsulated. Internalization of liposomes was followed by flow cytometry and fluorescence microscopy, demonstrating internalization via the endocytic pathway. Furthermore, since overexpression of matrix metalloproteinases (particularly MMP-2 and MMP-9) has been correlated to poor prognosis in many cancer types, detection of MMP expression is a satisfactory indication of the therapy efficiency and was then performed on treated cells. On MDA-MB-231 cells, MPPs expression was also significantly reduced by neridronate while entrapped in liposomes.
Keywords: Bisphosphonates; Neridronate; Liposome; Human breast cancer cells;
Drug release from PLGA-based microparticles: Effects of the “microparticle:bulk fluid” ratio by D. Klose; F. Siepmann; J.F. Willart; M. Descamps; J. Siepmann (123-131).
The aim of this study was to better understand the importance of the “microparticle mass:bulk fluid volume” ratio during in vitro drug release measurements from PLGA microparticles. Initially porous/non-porous, ibuprofen/lidocaine/propranolol HCl-loaded systems were exposed to phosphate buffer pH 7.4 in agitated test tubes, varying the microparticle concentration from 5:1 to 20:1 mg:mL. Interestingly, drug release was virtually unaffected by the “microparticle mass:bulk fluid volume” ratio in the case of initially porous, ibuprofen-loaded microparticles, exhibiting complete drug release within about 1 week. Optical microscopy, SEM, DSC and pH measurements of the bulk fluid revealed no major impact of the microparticle concentration on the systems’ properties within the first couple of days. However, a more rapid and pronounced decrease in the pH of the release medium occurred after 10–14 d at elevated “microparticle mass:bulk fluid volume” ratios. This resulted in an accelerated: (i) decrease in the glass transition temperature, (ii) microparticle agglomeration, and (iii) increase in the internal and external microparticle porosity. Importantly, this phenomenon did not significantly affect drug release from initially porous, lidocaine-loaded microparticles, exhibiting complete release within about 18 d. In contrast, drug release became significantly faster at higher “microparticle mass:bulk fluid volume” ratios in the case of initially non-porous, lidocaine-loaded microparticles and initially porous, propranolol HCl-loaded systems, exhibiting complete release after 1 and 2 months, respectively. Thus, depending on the type of system, the “microparticle mass:bulk fluid volume” ratio may or may not affect the observed release kinetics in vitro. This should be carefully taken into account when defining the experimental conditions for drug release measurements from this type of advanced drug delivery systems.
Keywords: PLGA; Microparticle; Controlled release; In vitro release; Release conditions;
Study of gel-forming properties of sucrose esters for thermosensitive drug delivery systems by Angéla Szűts; Mária Budai-Szűcs; István Erős; Naoya Otomo; Piroska Szabó-Révész (132-137).
Sucrose esters (SEs) are non-toxic, biodegradable, non-ionic surfactants. They have a wide range of hydrophilic–lipophilic balance values (1–16) and are usually applied as surfactants, or as solubility or penetration enhancers. The aims of this work were to study the gelling behaviour of SEs and the effects of this property on drug release. The gelling characteristics of two different SEs (P1670 and S970) were investigated by rheological measurements, and compared with each other. The effects of the gel-forming SEs on model drug (paracetamol) release were evaluated by in vitro drug release studies. The kinetics of the dissolution process were studied by analysing the dissolution data through the use of various kinetic equations. The results revealed that the gelling of the SEs is temperature- and concentration-dependent. The examined sucrose stearate (S970) has a stronger gel structure than that of sucrose palmitate (P1670) and this behaviour has a significant effect on the drug release. The analysis of the dissolution kinetic data in this study revealed that the dissolution follows the Korsmeyer–Peppas (paracetamol–P1670) or Higuchi (paracetamol–S970) equations.
Keywords: Controlled release; Dissolution kinetics; Gelling characteristics; Sucrose esters; Thermosensitive;
Study of critical points of drugs with different solubilities in hydrophilic matrices by Inmaculada Fuertes; Isidoro Caraballo; Antonia Miranda; Mónica Millán (138-146).
Hydrophilic matrices are one of the most popular controlled release systems in the World. It is well known that drug solubility increases the osmotic stress in hydrophilic matrices, resulting in higher swelling through the creation of microcavities and influencing the release rate. Drug solubility also affects the drug release mechanism, favouring the diffusion against the erosion mechanism. Nevertheless it has not been studied whether this can modify the critical points of the hydrophilic matrices.The objective of the present work is to estimate the excipient percolation threshold in HPMC K4M hydrophilic matrices containing acetaminophen, theophiline and ranitidine·HCl, and to study the influence of the drug solubility on the excipient percolation threshold.Dissolution assays were performed using the paddle method. Water uptake was examined using the modified Enslin apparatus. In order to estimate the excipient percolation threshold, the behaviour of the kinetic parameters versus the excipient volume fraction plus initial porosity, was studied.The excipient percolation thresholds were situated between 24.8–25.8, 14.7–18.4 and around 31.2% (v/v) HPMC in theophiline, ranitidine·HCl and acetaminophen matrices, respectively.On the other hand, using these and some previously reported values no relation has been found between drug solubility and excipient percolation threshold in hydrophilic matrices.
Keywords: Solubility; HPMC; Swelling matrices; Hydrophilic matrices; Percolation theory; Percolation threshold;
Enhancement of solubility and dissolution of Coenzyme Q10 using solid dispersion formulation by Pushp R. Nepal; Hyo-Kyung Han; Hoo-Kyun Choi (147-153).
This study aimed to develop a stable solid dispersion of Coenzyme Q10 (CoQ10) with high aqueous solubility and dissolution rate. Among various carriers screened, poloxamer 407 was most effective to form a superior solid dispersion of CoQ10 having significantly enhanced solubility. Particularly, solid dispersion of CoQ10 with poloxamer 407 in the weight ratio of 1:5 prepared by melting method enhanced the solubility of CoQ10 to the greatest extent. However, it exhibited poor stability and hence Aerosil® 200 (colloidal silicon dioxide) was incorporated into the solid dispersion as an adsorbent to inhibit the recrystallization process. The solid dispersion of CoQ10, poloxamer 407 and Aerosil® 200 in the weight ratio of 1:5:6 exhibited improved stability with no significant change in solubility during the 1-month stability test. Moreover, the solid dispersion formulation containing Aerosil® 200 significantly enhanced the extent of drug release (approx. 75% release) as well as the dissolution rate of CoQ10. In conclusion, the present study has developed the stable solid dispersion formulation of CoQ10 with poloxamer 407 and Aerosil® 200 for the enhanced solubility and dissolution of CoQ10, which could also offer some additional advantages including ease of preparation, good flowability and cost-effectiveness.
Keywords: Solid dispersion; Melting method; Coenzyme Q10; Poloxamer 407; Aerosil® 200;
Fluorescence spectroscopy of small peptides interacting with microheterogeneous micelles by Ana Paula Romani; Cassia Alessandra Marquezin; Amando Siuiti Ito (154-156).
Many peptides containing tryptophan have therapeutic uses and can be studied by their fluorescent properties. The biological activity of these peptides involves interactions with many cellular components and micelles can function as carriers inside organisms. We report results from the interaction of small peptides containing tryptophan with several microheterogeneous systems: sodium dodecyl sulphate (SDS) micelles; sodium dodecyl sulphate–poly(ethylene oxide) (SDS–PEO) aggregates; and neutral polymeric micelles. We observed that specific parameters, such as wavelength of maximum emission and fluorescence anisotropy, could be used to ascertain the occurrence of interactions. Affinity constants were determined from changes in the intensity of emission while structural modifications in rotameric conformations were verified from time-resolved measurements. Information about the location and diffusion of peptides in the microheterogeneous systems were obtained from tryptophan emission quenching experiments using N-alkylpyridinium ions. The results show the importance of electrostatic and hydrophobic effects, and of the ionization state of charged residues, in the presence of anionic and amphiphilic SDS in the microheterogeneous systems. Conformational stability of peptides is best preserved in the interaction with the neutral polymeric micelles.
Keywords: Colloidal carrier; Polymeric micelle; Polymer-surfactant; Tryptophan peptides; Fluorescence; Alkylpyridinium;
Noninvasive delivery of siRNA into the epidermis by iontophoresis using an atopic dermatitis-like model rat by K. Kigasawa; K. Kajimoto; S. Hama; A. Saito; K. Kanamura; K. Kogure (157-160).
Topical application of siRNA to the skin should be an effective treatment for serious skin disorders, such as atopic dermatitis. However, it is difficult to introduce hydrophilic macromolecules, including siRNA, into the skin by conventional methods. For efficient delivery of siRNA, we examined an iontophoretic technique, since it is suitable for the delivery of charged molecules. Naked siRNA effectively accumulated in the epidermis (and not in the dermis) after iontophoretic delivery. In contrast, siRNA did not penetrate tape-stripped skin by passive diffusion. In a rat model of atopic dermatitis, skin was sensitized with ovalbumin to stimulate IL-10 mRNA expression as observed in skin lesions. Iontophoretic delivery of anti-IL-10 siRNA significantly reduced (73%) the level of IL-10 mRNA. In conclusion, we successfully delivered naked siRNA into the epidermis and concomitantly suppressed the expression of an endogenous immuno-regulatory cytokine.
Keywords: SiRNA; Transdermal delivery; Iontophoresis; Interleukin-10;
Effects of extrusion process parameters on the dissolution behavior of indomethacin in Eudragit® E PO solid dispersions by Huiju Liu; Peng Wang; Xueyan Zhang; Fei Shen; Costas G. Gogos (161-169).
This work studied the dissolution of indomethacin (INM) into polymer excipient Eudragit® E PO (E PO) melt at temperatures lower than the melting point of INM using a laboratory-size, twin-screw counter-rotating batch internal mixer. The effects of three process parameters – set mixer temperature, screw rotating speed and residence time – were systematically studied. Scanning electron microscopy (SEM), optical microscopy (OM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were employed to investigate the evolution of INM's dissolution into the molten excipient. Differential scanning calorimetry (DSC) was used to quantitatively study the melting enthalpy evolution of the drug. The results showed that the dissolution rate increased with increasing the mixer set temperature, or the screw rotating speed. It was concluded that the dissolution of the drug in the polymer melt is a convective diffusion process, and that laminar distributive mixing can significantly enhance the dissolution rate. More importantly, the time needed for the drug to dissolve inside the molten polymer and the typical residence time for an extrusion process fall in the same range.
Keywords: Solid dispersion; Indomethacin; Eudragit® E PO; Batch mixer; Dissolution; Mixing;
Self-nanoemulsifying drug delivery system (SNEDDS) for oral delivery of Zedoary essential oil: Formulation and bioavailability studies by Yi Zhao; Changguang Wang; Albert H.L. Chow; Ke Ren; Tao Gong; Zhirong Zhang; Ying Zheng (170-177).
The aim of the present study was to develop a self-nanoemulsifying drug delivery system (SNEDDS) for the oral delivery of Zedoary turmeric oil (ZTO), an essential oil extracted from the dry rhizome of Curcuma zedoaria. Pseudo-ternary phase diagrams were constructed to identify the efficient self-emulsification regions. ZTO could serve as a partial oil phase with the aid of the second oil phase to enhance drug loading. Increasing the surfactant concentration reduced the droplet size but increased the emulsification time, while the reverse effect was observed by increasing the co-surfactant concentration. Based on the emulsification time, droplet size and zeta potential after dispersion into aqueous phase, an optimized formulation consisting of ZTO, ethyl oleate, Tween 80, transcutol P (30.8:7.7:40.5:21, w/w) and loaded with 30% drug was prepared. Upon mixing with water, the formulation was rapidly dispersed into fine droplets with a mean size of 68.3 ± 1.6 nm and ξ-potential of −41.2 ± 1.3 mV. The active components remained stable in the optimized SNEDDS stored at 25 °C for at least 12 months. Following oral administration of ZTO-SNEDDS in rats, both AUC and C max of germacrone (GM), a representative bioactive marker of ZTO, increased by 1.7-fold and 2.5-fold respectively compared with the unformulated ZTO.
Keywords: Self-nanoemulsifying; Essential oil; Zedoary turmeric oil; Pseudo-ternary phase diagram; Formulation; Bioavailability;
In vivo and in vitro anti-cancer activities and enhanced cellular uptakes of EGF fragment decorated doxorubicin nano-aggregates by Shinyoung Park; Hyuk Sang Yoo (178-185).
Doxorubicin nano-aggregate was prepared for the purpose of epidermal growth factor receptor targeted anti-cancer therapy. An epidermal growth factor fragment composed of 11 amino acids was conjugated to an amino terminal of bi-functional poly(ethylene glycol) and doxorubicin was subsequently conjugated to the other carboxyl terminal of the conjugate. A mixture of the conjugate, free doxorubicin, and triethylamine spontaneously formed nano-sized aggregates in aqueous phase, which was confirmed by transmission electron microscopy and dynamic light scattering. A549 cells incubated with doxorubicin nano-aggregates with the epidermal growth factor fragment showed increased endocytic uptakes of the aggregates compared to unmodified aggregates. Pre-blocking of the epidermal growth factor receptor on the cell significantly decreased a degree of the cellular uptakes. Cytotoxicity of the nano-aggregates was significantly increased when epidermal growth factor fragments were decorated on the surface of doxorubicin nano-aggregates, which was confirmed by a live/dead cell assay and a MTT-based cytotoxicity assay. When doxorubicin nano-aggregates were administered to model animals bearing human lung carcinoma, the epidermal growth factor fragment significantly strengthened in vivo anti-cancer effects of doxorubicin nano-aggregates compared to native doxorubicin or unmodified nano-aggregates. Thus, doxorubicin nano-aggregates decorated with an epidermal growth factor fragment is expected to be a potent anti-cancer agent aiming to tumor tissue over-expressing epidermal growth factor receptors.
Keywords: Nano-aggregates; Doxorubicin; EGF; Endocytosis;
Enhancement of doxorubicin concentration in the M5076 ovarian sarcoma cells by cucurbitacin E co-treatment by Yasuyuki Sadzuka; Haruna Hatakeyama; Takashi Sonobe (186-191).
Cucurbitacin E increases the doxorubicin (DOX) level in M5076 ovarian sarcoma via suppressed DOX efflux in vitro. An increase in DOX induced antitumor activity by cucurbitacin E in vivo has been reported previously. This paper attempts to clarify the mechanism of cucurbitacin E induced increments in the antitumor activity of DOX. MK-571, a multidrug resistance associated protein (MRP) inhibitor, significantly suppressed DOX efflux from M5076 ovarian sarcoma cells. The combination of cucurbitacin E with MK-571 also inhibited DOX efflux, whereas the efficacy was the same in each treatment. Namely, the inhibition of DOX efflux by cucurbitacin E was expected to be related to MRP. In contrast, it appeared that the effect of cucurbitacin E on DOX permeability did not relate to P-gp. The cucurbitacin E co-treatment significantly increased DOX concentration in the tumor within a short time after DOX administration, whereas the same treatment decreased the DOX concentration in normal tissues. The different effects of cucurbitacin E between tumor and normal tissues was speculated to be related to differences in DOX transport system on cell membrane. In DOX therapy, cucurbitacin E co-treatment was expected to increase DOX induced antitumor activity without an increase in adverse reactions due to DOX.
Keywords: Cucurbitacin E; Doxorubicin; MRP; Biochemical modulation; Permeability;
Combination antitumor effects of micelle-loaded anticancer drugs in a CT-26 murine colorectal carcinoma model by Hee Sam Na; Yeun Keun Lim; Young-Il Jeong; Hyun Sook Lee; You Jin Lim; Mi Sun Kang; Chong-Su Cho; Hyun Chul Lee (192-200).
Experiments were designed to evaluate the in vitro cytotoxic interactions of anticancer drugs in combination, evaluate synergistic activity in vivo and utilize micelle-forming polymeric drugs as drug carriers in a murine cancer model. Antitumor effects of 5-fluorouracil, cisplatin, CPT-11, oxaliplatin, etoposide, mitomycin-C, doxorubicin and paclitaxel were evaluated by determination of in vitro cytotoxicity to CT-26 colorectal tumor cells or in vivo following a subcutaneous transplant in BALB/c mice. Single agent and combination in vivo studies were also performed using drug-loaded polymeric micelles composed of poly(γ-benzyl l-glutamate) and poly(ethylene oxide) (GEG) or poly(l-lactide)/poly(ethylene glycol) (LE) diblock copolymer. After 3 days exposure, the mean IC50 (μg/mL) for 5-fluorouracil, cisplatin, CPT-11, oxaliplatin, etoposide, mitomycin-C, doxorubicin and paclitaxel were 0.95, 2.01, 4.47, 3.34, 3.5, 1.96, 1.8 and 2.1, respectively. When tumor cells were exposed to doxorubicin concurrently with etoposide or paclitaxel, evidence of synergy was observed in CT-26 cells in vitro. Doxorubicin and paclitaxel loaded into GEG or LE copolymers at a high concentration (19.5 and 16.7 wt%, respectively) were almost completely released (83.2% and 93.7%, respectively) by day 3. When tumor-bearing mice were treated in combination with doxorubicin–paclitaxel or doxorubicin–etoposide, substantial antitumor activity was evident compared with single therapy. These data suggest that in vitro cytotoxicity of anticancer drugs is related to in vivo results, and chemotherapy using micelle-loaded anticancer drugs represents a promising potential as a carrier system in modulating drug delivery.
Keywords: Combination therapy; Synergistic effect; Polymeric micelle; Doxorubicin; Paclitaxel;
Development of a positively charged prednicarbate nanoemulsion by Yücel Baspinar; Cornelia M. Keck; Hans-Hubert Borchert (201-208).
A physically and chemically stable positively charged prednicarbate nanoemulsion was developed as a carrier system for the treatment of atopic dermatitis. Phytosphingosine was used to obtain the positive charge and also because of its supportive properties for the restoration of damaged skin. As production method high pressure homogenization was employed. The optimal concentrations of phytosphingosine, the oil phase, and the emulsifiers were investigated. The production was optimized by investigating the influence of homogenization cycles, homogenization pressure, production temperature and type of homogenizer with respect to particle size, physical stability of the emulsions and chemical stability of prednicarbate. From the results the best formulation and the most appropriate production parameters were identified. In addition it could be shown that during high pressure homogenization the drug is relocated from the inner oil phase of the emulsion towards the stabilizer layer, which could be shown by an increase in chemical stability of prednicarbate. The efficiency of incorporation is influenced by the energy input during homogenization (e.g. number of homogenization cycles) but also by the production temperature. It was found that the nanoemulsions should be produced at elevated temperatures, with low homogenization pressures but higher numbers of homogenization cycles (e.g. 300 bar and 10 cycles). The results prove that the efficiency of high pressure homogenization should not only be judged by investigating the particle size and the physical stability of the emulsions alone, but also by assessing the chemical stability of the incorporated drug.
Keywords: Atopic dermatitis; Positively charged nanoemulsions; Phytosphingosine; Prednicarbate; High pressure homogenization; Chemical stability;
Development of a binary lipid nanoparticles formulation of itraconazole for parenteral administration and controlled release by Jin-Ki Kim; Jeong-Sook Park; Chong-Kook Kim (209-215).
The principal aim of this study was to develop an intravenous formulation of itraconazole (ITZ) using lipid nanoparticles based on binary mixture of liquid and solid lipids. Lipid nanoparticles were developed to provide the controlled release of ITZ as well as to improve the solubility of ITZ. Lipid nanoparticles were prepared with tristearin as a solid lipid, triolein as a liquid lipid, and a surfactant mixture of eggPC, Tween 80 and DSPE-PEG2000. ITZ was incorporated at the concentration of 20 mg/g. Lipid nanoparticles were manufactured by high-pressure homogenization method. The particle size and polydispersity index (PI) of lipid nanoparticles were below 280 nm and 0.2, respectively. Zeta potentials and incorporation efficiencies of lipid nanoparticles were around −30 mV and above 80%, respectively. Lipid nanoparticles containing 1% of liquid lipid showed the smallest particles size and the highest incorporation efficiency. Results from SEM, DSC and PXRD revealed that ITZ in lipid nanoparticles exists in an amorphous state. Release rates were increased as the amount of liquid lipid in lipid core increased, demonstrating that the release of ITZ from lipid nanoparticles could be controlled by modulation of the amount of liquid lipid in lipid core. Pharmacokinetic studies were performed after intravenous administration of lipid nanoparticles in rats at the dose of 5 mg/kg. The plasma concentration of ITZ was prolonged after intravenous administration of lipid nanoparticles. It is concluded that binary lipid nanoparticles could control the release and pharmacokinetic parameters of ITZ.
Keywords: Itraconazole; Controlled release; Lipid nanoparticles; Binary mixture;
The influence of polymer architecture on the protective effect of novel comb shaped amphiphilic poly(allylamine) against in vitro enzymatic degradation of insulin—Towards oral insulin delivery by C.J. Thompson; L. Tetley; W.P. Cheng (216-227).
Nanocomplexes formed between amphiphilic poly(allylamine) (PAA) and insulin were prepared, characterised and the impact of polymer architecture on the protection of insulin against three enzymes was investigated. PAA previously modified with either cetyl or cholesteryl pendant groups at two levels of hydrophobic grafting and its quaternised derivatives were used to produce polymer–insulin nanocomplexes. Transmittance study, differential scanning calorimetry, hydrodynamic size and zeta potential measurement were conducted and the morphology of the complexes were visualised using transmission electron microscopy. All polymers were found to have an optimal polymer to insulin ratio of 0.4:1 mg mL−1 with particle size ranging from 88 to 154 nm. Polymer architecture has an impact on the morphology of the complexes produced but has little influence on the complexation efficiency (CE). Almost all polymers were unable to produce complexes with a CE of above 50%. Most polymers demonstrated an ability to reduce insulin degradation by trypsin while the polymer architecture plays a pivotal role against α-chymotrypsin and pepsin degradation. Quaternised cholesteryl polymers were able to significantly limit insulin degradation by α-chymotrypsin while cetyl polymers were particularly effective against pepsin degradation. These results indicated that a combination of polymers might be required to enhance protection against all three proteolytic enzymes for efficacious oral delivery of insulin.
Keywords: Oral delivery; Proteins and peptides; Polymeric micelles; Nanocomplexes; Enzymatic degradation; Amphiphilic polymers;
Transfection efficiencies of PAMAM dendrimers correlate inversely with their hydrophobicity by Antos Shakhbazau; Iauhenia Isayenka; Nikolai Kartel; Natalya Goncharova; Ihar Seviaryn; Svetlana Kosmacheva; Mihail Potapnev; Dzmitry Shcharbin; Maria Bryszewska (228-235).
Dendriplexes were characterized by ethidium bromide intercalation assay and their transfection efficiency was studied using HEK 293 cells and human mesenchymal stem cells. PAMAM G4 showed a higher transfection efficiency than PAMAM G3–G6, G4-OH, G4-25% or G4-50% dendrimers. Substitution of OH groups for the NH2 surface groups rendered the dendrimer unable to form dendriplexes and to transfect cells. Partial (25%) substitution of CH3 groups for the NH2 groups markedly impaired transfection; 50% substitution decreased the ability of PAMAM G4 to transfect threefold. It was concluded that increased hydrophobicity decreased the ability of dendrimers to transfect. PAMAM G4-50% is highly hydrophobic and forms micelles in solution, which can transfect pGFP. The results of ethidium bromide intercalation assays, ANS fluorescence studies and transfection efficiencies of PAMAM dendrimers were correlated. Subsequently, we constructed a neurotrophin-encoding plasmid and studied its delivery to mesenchymal stem cells using PAMAM G4 dendrimer and Lipofectamine 2000. Lipofectamine 2000 was a more effective carrier (18.5%) than PAMAM G4 dendrimer (1.2%).
Keywords: Dendrimer; Gene delivery; Transfection; Dendriplex; Ethidium bromide intercalation assay; ANS fluorescence;
Determination of poly(ɛ-caprolactone) solubility parameters: Application to solvent substitution in a microencapsulation process by C. Bordes; V. Fréville; E. Ruffin; P. Marote; J.Y. Gauvrit; S. Briançon; P. Lantéri (236-243).
The evolution of regulation on chemical substances (i.e. REACH regulation) calls for the progressive substitution of toxic chemicals in formulations when suitable alternatives have been identified. In this context, the method of Hansen solubility parameters was applied to identify an alternative solvent less toxic than methylene chloride used in a microencapsulation process. During the process based on a multiple emulsion (W/O/W) with solvent evaporation/extraction method, the solvent has to dissolve a polymer, poly(ɛ-caprolactone) (PCL), which forms a polymeric matrix encapsulating or entrapping a therapeutic protein as the solvent is extracted. Therefore the three partial solubility parameters of PCL have been determined by a group contribution method, swelling experiments and turbidimetric titration. The results obtained allowed us to find a solvent, anisole, able to solubilize PCL and to form a multiple emulsion with aqueous solutions. A feasibility test was conducted under standard operating conditions and allowed the production of PCL microspheres.
Keywords: Hansen solubility parameters; Solvent substitution; Poly(ɛ-caprolactone); Microencapsulation; Anisole;
The initial release of cisplatin from poly(lactide-co-glycolide) microspheres by Yan Sim Lee; John P. Lowe; Ed Gilby; Semali Perera; Sean P. Rigby (244-254).
PLGA microspheres loaded with cisplatin were produced using a single emulsion method. A semi-empirical model, with bi-exponential terms, was found to give a better fit to the drug release profiles compared to a mono-exponential model. This model suggests that there are two separate fractions of drug present in the depot. A fraction of the drug is located near/at the surface of the depot, and is readily released during immersion in buffer. A second fraction of drug is entrapped deeper within the depot and is subsequently released. It was also found that the initial release of cisplatin from PLGA microsphere is highly diffusion-controlled and the classical Higuchi model provides a good fit. From studies of water diffusion using PFG-NMR, results suggested that 50:50 PLGA microsphere was most susceptible to swelling and this might have promoted the faster initial drug release. Results from NMR cryoporometry also indicated that the developed PLGA microspheres could have “ink-bottle” pores.
Keywords: PLGA microspheres; In vitro cisplatin release; PFG-NMR; NMR cryoporometry;
Practical application to time indicator of a novel white film formed by interaction of calcium salts with hydroxypropyl methylcellulose by Sumihiro Shiraishi; Yukoh Sakata; Hiroyuki Yamaguchi (255-263).
We have found that a cast film forms a white film when an aqueous solution comprising hydroxypropyl methylcellulose (HPMC) and calcium salts such as calcium lactate pentahydrate (CLP) and calcium chloride (CaCl2) is used. In contrast, the obtained white film was transformed into a transparent film by the addition of purified water. The transformation time for the change from the white film to the transparent film was dependent on film thickness. The relationship between the transformation time and the film thickness was significantly correlated, and it was found that the white film could be adaptable as time indicator. The formation of a white film comprising HPMC and calcium salts was strongly dependent on temperature conditions. The objective of the present study is to investigate the mechanism of the formation of this white film because of the interaction between HPMC and calcium salts. The DSC and XRPD results indicate that the calcium salts affect the HPMC polymer phase in the cast film comprising HPMC and calcium salts. By carrying out attenuated total reflection Fourier transform infrared (ATR FT-IR) analysis, we found that the white film could be formed by the calcium salts affecting the region associated with the C–O–C, C–O, and CH3 stretching of the HPMC polymer phase.
Keywords: HPMC; Calcium salts; Interaction; White film; Time indicator;
Pharmacokinetics, tissue distribution and safety of cinnarizine delivered in lipid emulsion by Shuai Shi; Hao Chen; Xia Lin; Xing Tang (264-270).
The aim of this study was to assess the potential of cinnarizine loaded in lipid emulsion to modify the pharmacokinetics, tissue distribution and safety of cinnarizine. The cinnarizine-loaded emulsion (CLE) which can remain stable over 18-month storage at 4 ± 2 °C was prepared by high-pressure homogenization. Nicomp™ 380 particle sizing system and HPLC were used to evaluate CLE in vitro, while UPLC/MS/MS for pharmacokinetic and tissue distribution study. The pharmacokinetics and tissue distributions of CLE were assessed by comparing with the solution form after intravenous administration to rats at a dose of 2 mg/kg. The CLE showed significant higher AUC and lower clearance and distribution volume than those of solution form. This helped cinnarizine to reach higher level in vessel, and circulate in the blood stream for a longer time resulting in better therapeutic effect. The tissue distribution exhibited significant lower uptake of CLE emulsion in lung and brain, indicating the advantage of CLE over the solution form in reducing drug precipitation in vivo and toxicity in CNS. Drug safety assessment studies including hemolysis test, intravenous stimulation and injection anaphylaxis revealed that the CLE was safe for intravenous injection.
Keywords: Cinnarizine; Lipid emulsion; Pharmacokinetics; Tissue distribution; Safety;
“Intelligent” nanoassembly for gene delivery: In vitro transfection and the possible mechanism by Zhenghong Xu; Lingli Chen; Zhiwen Zhang; Wangwen Gu; Yaping Li (271-276).
A new “intelligent” nanoassembly (INA), consisting of a condensed core of pDNA with protamine sulfate (PS) and a dioleoylphosphatidyl ethanolamine (DOPE)-based lipid envelope containing poly(ethylene glycol)-disulfide-DOPE (PSD), was designed and investigated. The in vitro release experiment was carried out in solution containing 10 mM of Glutathione, which reflected the redox potential of the intracellular environment. The experimental result indicated that PSD possessed a good ability of self-dePEGylation and could result in efficient release of content in the reductive environment. INAs showed higher transfection efficiency and much lower cytotoxicity compared with Lipofectamine™ 2000 on HEK 293 cells. Cellular uptake and subcellular localization, as well as the quantitation of nuclear transfer demonstrated that the superior transfection efficiency of INAs could result from both enhanced cellular uptake mediated by DOPE and efficient nuclear delivery mediated by PS. The biodistribution of INAs in nude mice bearing tumor implied that this PSD-based nanoassembly loading PS/DNA could be a promising gene delivery system for tumor therapy.
Keywords: DNA; Gene delivery; Nanoassembly; Poly(ethylene glycol)-disulfide-DOPE; Self-dePEGylation;
The effects of particle properties on nanoparticle drug retention and release in dynamic minoxidil foams by Yanjun Zhao; Marc B. Brown; Stuart. A. Jones (277-284).
Nanocarriers may act as useful tools to deliver therapeutic agents to the skin. However, balancing the drug–particle interactions; to ensure adequate drug loading, with the drug–vehicle interactions; to allow efficient drug release, presents a significant challenge using traditional semi-solid vehicles. The aim of this study was to determine how the physicochemical properties of nanoparticles influenced minoxidil release pre and post dose application when formulated as a simple aqueous suspension compared to dynamic hydrofluoroalkane (HFA) foams. Minoxidil loaded lipid nanoparticles (LN, 1.4 mg/ml, 50 nm) and polymeric nanoparticles with a lipid core (PN, 0.6 mg/ml, 260 nm) were produced and suspended in water to produce the aqueous suspensions. These aqueous suspensions were emulsified with HFA using pluronic surfactant to generate the foams. Approximately 60% of the minoxidil loaded into the PN and 80% of the minoxidil loaded into the LN was released into the external aqueous phase 24 h after production. Drug permeation was superior from the PN, i.e. it was the particle that retained the most drugs, irrespective of the formulation method. Premature drug release, i.e. during storage, resulted in the performance of the topical formulation being dictated by the thermodynamic activity of the solubilised drug not the particle properties.
Keywords: Drug release; Nanoparticles; Foam; Vehicle; Minoxidil; Permeation;
Fabrication of drug nanoparticles by evaporative precipitation of nanosuspension by M. Kakran; N.G. Sahoo; L. Li; Z. Judeh; Y. Wang; K. Chong; L. Loh (285-292).
Evaporative precipitation of nanosuspension (EPN) was used to fabricate nanoparticles of a poorly water-soluble antimalarial drug, artemisinin (ART), with the aim of enhancing its dissolution rate. We investigated the nanoparticle fabrication of ART via a full factorial experimental design considering the effects of drug concentration and solvent to antisolvent ratio on the physical, morphological and dissolution properties of ART. Characterization of the original ART powder and EPN prepared ART nanoparticles was carried out by scanning electron microscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dissolution tester. DSC and XRD studies suggested that the crystallinity of EPN prepared ART nanoparticles decreased with increasing drug concentration and ratio of solvent to antisolvent. The particle diameters of EPN prepared ART nanoparticles were found to be 100–360 nm. The dissolution of EPN prepared ART nanoparticles markedly increased as compared to the original ART powder. A percent dissolution surface-response model was used to elucidate the significant and direct relationships between drug concentration and solvent to antisolvent ratio on one hand and percent dissolution on the other hand. The best dissolution percent was found to be 75.9%, at the drug concentration of 15 mg/mL and solvent to antisolvent ratio (by volume) of 1:20.
Keywords: Malaria; Artemisinin; Crystallinity; Nanoparticles; Dissolution;
Influence of dendrimer generation and polyethylene glycol length on the biodistribution of PEGylated dendrimers by Chie Kojima; Celeste Regino; Yasuhito Umeda; Hisataka Kobayashi; Kenji Kono (293-296).
Dendrimers are a potential drug carrier. Because modification with polyethylene glycol (PEG) is known to improve the blood retention, PEGylated dendrimers have been studied as a useful drug carrier. In this study, three types of PEGylated l-lysine-bearing polyamidoamine dendrimers (PEG2k-Lys-PAMAM (G4), PEG5k-Lys-PAMAM (G4), PEG2k-Lys-PAMAM (G5)) were synthesized, which are composed of a dendrimer of different generations (generations 4 and 5) and PEG chains with different molecular weights (2k and 5k). An acetylated l-lysine-bearing dendrimer was also synthesized as a non-PEGylated dendrimer. Bifunctional diethylenetriaminepentaacetic acid (pSCN-benzyl-DTPA) was bound to the epsilon -amino group of lysine in a dendrimer, to be labeled with radioactive indium-111. These PEGylayed dendrimers showed longer blood retention and lower accumulation in other normal organs such as the kidneys than the non-PEGylated dendrimer. The PEGylated dendrimers with the higher generation and the longer PEG led the greater blood retention.
Keywords: Dendrimer; Polyethylene glycol; Biodistribution; Drug delivery; Radiolabel;