International Journal of Pharmaceutics (v.412, #1-2)
Editorial Board (iii).
Strategies for bringing drug delivery tools into discovery by Elizabeth Kwong; John Higgins; Allen C. Templeton (1-7).
The past decade has yielded a significant body of literature discussing approaches for development and discovery collaboration in the pharmaceutical industry. As a result, collaborations between discovery groups and development scientists have increased considerably. The productivity of pharma companies to deliver new drugs to the market, however, has not increased and development costs continue to rise. Inability to predict clinical and toxicological response underlies the high attrition rate of leads at every step of drug development. A partial solution to this high attrition rate could be provided by better preclinical pharmacokinetics measurements that inform PD response based on key pathways that drive disease progression and therapeutic response. A critical link between these key pharmacology, pharmacokinetics and toxicology studies is the formulation. The challenges in pre-clinical formulation development include limited availability of compounds, rapid turn-around requirements and the frequent un-optimized physical properties of the lead compounds. Despite these challenges, this paper illustrates some successes resulting from close collaboration between formulation scientists and discovery teams. This close collaboration has resulted in development of formulations that meet biopharmaceutical needs from early stage preclinical in vivo model development through toxicity testing and development risk assessment of pre-clinical drug candidates.
Keywords: Drug delivery tool in discovery; In vivo model development; Nanoparticles; Alternate route of administration; Mechanism-based toxicity; Target delivery;
Leucine enhances aerosol performance of Naringin dry powder and its activity on cystic fibrosis airway epithelial cells by Lucia Prota; Antonietta Santoro; Maurizio Bifulco; Rita P. Aquino; Teresa Mencherini; Paola Russo (8-19).
The effect of different amino acids (AAs) on the aerosol performance of N spray-dried powders was studied. Morphology, size distribution, density, dissolution rate were evaluated and correlated to process parameters. The aerosol performance was analyzed by both Single Stage Glass Impinger and Andersen Cascade Impactor. Results indicated that powders containing 5% (w/w) of leucine, proline or histidine and dried from 3:7 ethanol/water feeds showed very satisfying aerodynamic properties with fine particle fraction > 60%. Both neat N (raw and spray-dried) and N-leu1 dry-powder showing good aerodynamic properties were tested in cystic fibrosis (CF) and normal bronchial epithelial cells. Cell proliferation and expression levels of the key enzymes of the NF-κB and MAPK/ERK pathways, overactivated in CF cell lines, were evaluated. N-leu1 was able to significantly inhibit the expression levels of IKKα, IKKβ, as well as of the direct NF-κB inhibitor, IκBα. In addition N-Leu1 inhibited phosphorylation of ERK1/2 kinase and did not reduce cell proliferation as observed for the neat raw drug. Leucine co-spray-dried with the drug improved both aerodynamic properties and in vitro pharmacological activity of Naringin. The optimized N-Leu formulation as dry powder is potentially able to reduce hyperinflammatory status associated to CF.
Keywords: Naringin; Leucine; Turbospin®; Cystic Fibrosis; airway epithelial cells; NF-κB; ERK 1/2 inhibition;
Application of quartz crystal microbalance to study the impact of pH and ionic strength on protein–silicone oil interactions by Nitin Dixit; Kevin M. Maloney; Devendra S. Kalonia (20-27).
The effect of solution pH and ionic strength on the interactions between a model protein and silicone oil was investigated using quartz crystal microbalance. At low ionic strength, electrostatic forces mainly govern the adsorption of protein to the silicone oil/water interface while at higher ionic strength, hydrophobic interactions dominate the overall protein adsorption.In this study, we have used quartz crystal microbalance (QCM) to quantitate the adsorption of a protein on silicone oil coated surfaces as a function of protein concentration, pH and ionic strength using a 5 MHz quartz crystal. Protein adsorption isotherms were generated at different solution pH and ionic strengths. Surface saturation concentrations were selected from adsorption isotherms and used to generate adsorption profiles from pH 3.0 to 9.0, and at ionic strengths of 10 mM and 150 mM. At low ionic strength (10 mM) and pH 5.0 (close to the isoelectric point of the protein), maximum adsorption of protein to the silicone oil surface was observed. At higher ionic strength (150 mM), no significant pH influence on adsorption was observed. QCM could be used as a reliable technique to study the binding of proteins to silicone oil coated surfaces.
Keywords: Silicone oil/water interface; Interfacial adsorption; Aggregation; Quartz crystal microbalance; Hydrophobicity; Protein;
Suspension pellet layering using PVA–PEG graft copolymer as a new binder by L. Suhrenbrock; G. Radtke; K. Knop; P. Kleinebudde (28-36).
Flow characteristics and binding properties of Kollicoat® IR solutions are promising for an application in suspension layering processes to obtain drug loaded pellets. This study is based on the results of three experimental designs. Within the first one, a suitable binder concentration in suspensions with 35–45% solids was determined. The required binder level was high with 20% in the layer, but led to good and robust process performance with a yield between 92.6% and 97.6%. Since the polymer succeeded to immobilize particles on the starter surface, the second set of experiments observed whether Kollicoat® IR was able to layer coarser drug particles with only 8% or 30% of the drug mass below ten microns. Large particle size is a generally known limitation for effective suspension layering. It was shown, that Kollicoat® IR was suited to bind 98.5% of the coarsest drug quality on the surface. Additionally these coarse particles acted like a separating agent and kept the pellets from sticking to each other. The third experimental design observed the influence of particle size and viscosity changes. All suspensions had a suitable viscosity with maximum of 120 mPa s. A viscosity change, due to solids in the suspension, did not influence the process performance. The product properties were investigated. The pellets were spherical and size distribution of the pellets was excellent. However the structure was porous, due to the sterical arrangement of the drug particles, although the polymer concentration in the layer was high with a polymer to drug ratio of 1:4.
Keywords: Pellet suspension layering; Binder; Poly(vinyl alcohol)–poly(ethylene glycol) graft copolymer; Kollicoat® IR; Drug particle size; Viscosity;
Penetration enhancer containing vesicles as carriers for dermal delivery of tretinoin by Maria Manconi; Chiara Sinico; Carla Caddeo; Amparo Ofelia Vila; Donatella Valenti; Anna Maria Fadda (37-46).
The ability of a recently developed novel class of liposomes to promote dermal delivery of tretinoin (TRA) was evaluated. New penetration enhancer-containing vesicles (PEVs) were prepared adding to conventional phosphatidylcholine vesicles (control liposomes) different hydrophilic penetration enhancers: Oramix® NS10 (OrNS10), Labrasol® (Lab), Transcutol® P (Trc), and propylene glycol (PG). Vesicles were characterized by morphology, size distribution, zeta potential, incorporation efficiency, stability, rheological behaviour, and deformability. Small, negatively charged, non-deformable, multilamellar vesicles were obtained. Rheological studies showed that PEVs had fluidity higher than conventional liposomes.The influence of the obtained PEVs on (trans)dermal delivery of tretinoin was studied by ex vivo diffusion experiments through new born pig skin using formulations having the drug both inside and outside the vesicles, having TRA only inside, in comparison with non-incorporated drug dispersions of the same composition used to produce the studied vesicles. Main result of these experiments was an improved cutaneous drug accumulation and a reduced transdermal TRA delivery (except for PG-PEVs). TRA deposition provided by PEVs was higher for dialysed than for non-dialysed vesicles. Further, the accumulation increased in the order: control liposomes < PG-PEVs < Trc-PEVs ≤ Or-PEVs < Lab-PEVs. SEM analysis of the skin gave evidence of PEVs’ ability to strongly interact with the intercellular lipids causing an enlargement of this region.
Keywords: Liposomes; Tretinoin; Penetration enhancers; Skin permeation; Rheology; SEM;
Experimental study on infusion devices containing polyvinyl chloride: To what extent are they di(2-ethylhexyl)phthalate-free? by Stéphanie Genay; Chiara Luciani; Bertrand Décaudin; Nicolas Kambia; Thierry Dine; Nathalie Azaroual; Piera Di Martino; Christine Barthélémy; Pascal Odou (47-51).
The use of medical devices containing highly criticized phthalates including di(2-ethylhexyl) phthalate (DEHP) has been challenged by European directive 2007/47/CE, put into effect in March 2010. New plasticizers are now being used to soften PVC in medical devices: trioctyltrimellitate (TOTM), di-isononyl-cyclohexan-1,2-dicarboxilate (DINCH) and di(2-ethylhexyl) terephthalate (DEHT). To quantify DEHP in nine DEHP-free medical devices made of PVC softened by alternative plasticizers, high performance liquid chromatography analysis with ultraviolet detection at 220 nm wavelength was achieved. An NMR spectroscopy was performed to confirm DEHP presence. Only two medical devices out of the nine tested were truly without DEHP. One of them showed traces of DEHP exceeding the threshold contamination of 0.1% in plastic mass set by REACH regulations. TOTM plasticizer is still incriminated when polyvinyl-chloride (PVC) is contaminated with DEHP. Manufacturers must verify the purity of their raw material, not only on PVC, but also on other soft plastics entering into the composition of medical infusion devices. The clinical consequences of exposure to certain levels of DEHP have not been evaluated. A solution could be to use alternative PVC-free materials.
Keywords: Plasticizers; Di(2-ethylhexyl) phthalate; Trioctyl trimellitate; Di-(2-ethylhexyl) terephthalate; Di-isononyl-cyclohexan-1,2-dicarboxilate;
Biodegradable and temperature-responsive polyurethanes for adriamycin delivery by Xianke Sun; Hui Gao; Guolin Wu; Yinong Wang; Yunge Fan; Jianbiao Ma (52-58).
To develop biodegradable polymers with temperature-sensitivity, a series of polyurethanes consisting of poly (ethylene glycol) (PEG) and l-lysine ester diisocyanate (LDI) were synthesized, and the structure and molecule weight of the polymers were examined by 1H NMR, FT-IR, gel permeation chromatography (GPC). The solution properties of the copolymers were studied by turbidity measurement and size measurement. Polyurethanes could form nanoparticles by sonication in water. No temperature-sensitivity was observed with the polyurethane nanoparticles composed of PEG1000 and PEG1500. On the contrary, LDI-PEG600 exhibited a reversible temperature-responsive behavior in aqueous solution. The transition temperature (T c) of LDI-PEG600 with methyl ester of LDI was higher than that of LDI-PEG600 with butyl ester side chain. The polymers were then used to encapsulate adriamycin (ADR) by the dialyzing method from dimethylformamide solution against water. ADR could be successfully encapsulated into the polyurethane nanoparticles. The ratio of ADR release from polymeric nanoparticles increased sharply above the T c, while the release was suppressed below the T c.
Keywords: Polyurethanes; PEG; Lysine; pH-responsive; Adriamycin; Delivery;
Preparation of microspheres containing low solubility drug compound by electrohydrodynamic spraying by Adam Bohr; Jakob Kristensen; Eleanor Stride; Mark Dyas; Mohan Edirisinghe (59-67).
Micro- and nanoparticle formulations are widely used to improve the bioavailability of low solubility drugs. In this study, electrospraying is introduced as a method for producing drug-loaded microspheres at ambient conditions. PLGA microspheres containing celecoxib, a low solubility drug, were prepared with the objective of producing near-monodisperse microspheres with the drug in a stable amorphous form. We found that it is possible to produce near-monodisperse celecoxib-loaded PLGA microspheres at different polymer:drug ratios. The microspheres produced were in the size range 1–5 μm depending on the polymer:drug ratio and had smooth surfaces. Thermal analysis further indicates that celecoxib is present in an amorphous form inside the microspheres. Drug dissolution studies showed an initial burst release followed by a period of sustained release with the dissolution curve depending on the polymer:drug ratio. Electrospraying is thus a promising method for producing amorphous microspheres of low solubility drugs such as celecoxib. The microsphere properties may be further optimized to achieve an appropriate dissolution profile with the aim of increasing oral bioavailability of low solubility drugs.
Keywords: Microsphere; Electrospraying; Low solubility; Celecoxib; PLGA; Particle engineering;
Simultaneous controlled vitamin release from multiparticulates: Theory and experiment by T. Seidenberger; J. Siepmann; H. Bley; K. Maeder; F. Siepmann (68-76).
The aim of this study was to simultaneously control the release of multiple vitamins exhibiting very different water-solubility and molecular weights from multiparticulates. Several types of sucrose esters and triglycerides were studied as matrix formers in granules prepared by wet granulation, melt granulation or compression and grinding. The vitamin release kinetics were measured in 0.1 N HCl, phosphate buffer pH 6.8 and water in a USP paddle apparatus. An appropriate analytical solution of Fick's second law of diffusion was used to better understand the underlying mass transport phenomena. Importantly, the release rates of nicotinamide, pyridoxine hydrochloride, riboflavin 5′-phosphate, riboflavin, thiamine chloride hydrochloride and thiamine nitrate can simultaneously be controlled from the investigated multiparticulates. Varying the total vitamin content, granule size, type of preparation technique and type of matrix former (Sucrose Stearate S370, Sucrose Stearate S1170, glycerol dibehenate, glycerol dipalmitostearate), desired vitamin release rates can be adjusted. Interestingly, diffusion seems to be the dominant mass transport mechanism in most cases. Thus, appropriate solutions of Fick's law can be used to quantitatively predict the effects of the systems’ composition and dimensions on the resulting vitamin release patterns. This knowledge can significantly help facilitating device optimization.
Keywords: Sucrose ester; Vitamin; Mathematical modeling; Diffusion; Release mechanism; Controlled release;
Dissolution from solid lipid extrudates containing release modifiers by Sinan Güres; Peter Kleinebudde (77-84).
The influence of different types of release modifiers on the dissolution from solid lipid extrudates was investigated. Diprophylline was extruded together with 45% tristearin and 5% (w/w) of a release modifier to suitable extrudates. Three groups of release modifiers were defined: Hydrocolloids, disintegrants and pore formers. All of the release modifier-containing extrudates showed a faster release compared to the reference extrudate, which contained 50% (w/w) of each, API and lipid. Increasing the amount of diprophylline in the binary mixture up to 55% (w/w) also increased its release rate. Compared to this new reference, not all of the release modifier-containing extrudates exhibited an increased dissolution rate. Within the group of pore formers, there was a great discrepancy concerning the dissolution rates. Extrudates containing polyethylene glycol (PEG) exhibited a much higher release rate compared with extrudates containing sodium chloride or mannitol. This behaviour was assumed to be based on the extrusion temperature of 65 °C at which PEG exists in the molten state. The hypothesis was tested using different PEGs and another solid lipid.
Keywords: Solid lipid extrusion; Dissolution; Polyethylene glycol; Pore former; Disintegrants; Hydrocolloids;
Assessment of fluidity of different invasomes by electron spin resonance and differential scanning calorimetry by Nina Dragicevic-Curic; Manfred Friedrich; Silvia Petersen; Dietrich Scheglmann; Dennis Douroumis; Winfried Plass; Alfred Fahr (85-94).
The aim of this study was to investigate the influence of membrane-softening components (terpenes/terpene mixtures, ethanol) on fluidity of phospholipid membranes in invasomes, which contain besides phosphatidylcholine and water, also ethanol and terpenes. Also mTHPC was incorporated into invasomes in order to study its molecular interaction with phospholipids in vesicular membranes. Fluidity of bilayers was investigated by electron spin resonance (ESR) using spin labels 5- and 16-doxyl stearic acid and by differential scanning calorimetry (DSC). Addition of 1% of a single terpene/terpene mixture led to significant fluidity increase around the C16 atom of phospholipid acyl chains comprising the vesicles. However, it was not possible to differentiate between the influences of single terpenes or terpene mixtures. Incorporation of mTHPC into the bilayer of vesicles decreased fluidity near the C16 atom of acyl chains, indicating its localization in the inner hydrophobic zone of bilayers. These results are in agreement with DSC measurements, which showed that terpenes increased fluidity of bilayers, while mTHPC decreased fluidity. Thus, invasomes represent vesicles with very high membrane fluidity. However, no direct correlation between fluidity of invasomes and their penetration enhancing ability was found, indicating that besides fluidity also other phenomena might be responsible for improved skin delivery of mTHPC.
Keywords: Liposomes; Invasomes; Fluidity; Electron spin resonance; Differential scanning calorimetry; Temoporfin;
Weak bases and formation of a less soluble lauryl sulfate salt/complex in sodium lauryl sulfate (SLS) containing media by Shobha N. Bhattachar; Donald S. Risley; Pornpen Werawatganone; Aktham Aburub (95-98).
This work reports on the solubility of two weakly basic model compounds in media containing sodium lauryl sulfate (SLS). Results clearly show that the presence of SLS in the media (e.g. simulated gastric fluid or dissolution media) can result in an underestimation of solubility of some weak bases. We systematically study this phenomenon and provide evidence (chromatography and pXRD) for the first time that the decrease in solubility is likely due to formation of a less soluble salt/complex between the protonated form of the weak base and lauryl sulfate anion.
Keywords: Sodium lauryl sulfate; Solubility; Salt; Complex;
Enhanced bioavailability and retinal accumulation of lutein from self-emulsifying phospholipid suspension (SEPS) by Srinivasan Shanmugam; Jae-Hyun Park; Kyeong Soo Kim; Zong Zhu Piao; Chul Soon Yong; Han-Gon Choi; Jong Soo Woo (99-105).
Ability of any formulation to keep the drug in solubilized form in vivo is essential for bioavailability (BA) enhancement rather than the solubility of drug in the formulation vehicle/matrix itself. Besides, utilization of an excess amount of surfactants/co-surfactants to solubilize the drug in the lipid formulation poses potential pharmaceutical as well as health problems. To address this problem, self-emulsifying phospholipid suspension (SEPS) consisting of high amount of phospholipid (an endogenous lipid with efficient in vivo emulsification capability) and relatively low amount of surfactant/co-surfactant has been proposed to enhance the bioavailability (BA) of lutein. In this study, the ability of SEPS formulation to enhance the BA of lutein was assessed from three SEPS formulations with various amounts of phospholipid (SEPS-0, SEPS-I, and SEPS-II with 0 mg, 250 mg, and 500 mg of Phosal® 53 MCT, respectively) in beagle dogs following a single oral administration of lutein equivalent to 100 mg, and were compared with commercial formulation (CF). In addition, the retinal accumulation of lutein in Sprague Dawley (SD) rats’ eyes from SEPS-II formulation (lutein dose of 100 mg/kg/day) was investigated following single daily oral administration for a period of 14 days. CF and placebo (vegetable oil without lutein) were also administered for the same period of time and were compared with the SEPS-II formulation. In the relative BA study in beagle dogs, no significant differences were observed between the pharmacokinetic (PK) parameters of formulation SEPS-O and CF. However, the C max in comparison to CF was 3.70 folds and 11.76 folds higher for SEPS-I and SEPS-II, respectively. Relative BA compared to CF was 178.88% and 473.13% for SEPS-I and SEPS-II, respectively. The retinal lutein accumulation was 0.91 ± 0.31 ng/g, 3.45 ± 1.63 ng/g, and 14.72 ± 2.02 ng/g for placebo, CF, and SEPS-II, respectively. This enhancement was about 16.1 folds and 4.27 folds compared to placebo and CF, respectively. The relative BA study in dogs and retinal accumulation study in rats demonstrated the excellent ability of SEPS to enhance the BA of lutein. For this reason, SEPS containing lutein could be a promising lipid based delivery system for the prevention of ocular diseases.
Keywords: Lutein; Lipid based oral drug delivery; Self-emulsifying phospholipid suspension; Pharmacokinetics/bioavailability; Retinal accumulation;
A new peptide motif present in the protective antigen of anthrax toxin exerts its efficiency on the cellular uptake of liposomes and applications for a dual-ligand system by Golam Kibria; Hiroto Hatakeyama; Hideyoshi Harashima (106-114).
Protective antigen (PA) is a nontoxic protein present in anthrax toxin. Domain 4 of PA (PA-D4) acts as a receptor binding site for tumor endothelial marker 8 (TEM8). In this study, KYND motif from PA-D4 was utilized as a ligand against TEM8. The efficiency of KYND motif on cellular association was assessed by evaluating the cellular uptake of PEGylated liposomes (PEG-LPs) in TEM8 positive and negative cells. The peptide was attached on the top of the PEG of PEG-LP. Compared to PEG-LP, KYND modified PEG-LP (KYND-PEG-LP) enhanced the cellular uptake to a greater extent in all cell lines. Based on the inhibition assay, no receptor involvement was observed in the cellular association of KYND-PEG-LP, suggesting that KYND motif functions as a cell penetrating peptide (CPP) which facilitated the internalization of PEG-LP via clathrin mediated endocytosis pathway. Further enhancement of cellular uptake was observed when KYND-PEG-LP was combined with octaarginine (R8) on the surface of lipid membrane as dual-CPP ligand formulation, however, when PEG-LP combined with only R8, only negligible enhancement was observed. These findings suggest that two CPP ligands act in a synergistic fashion; therefore the dual-CPP ligand based liposomal formulation can be assumed to be an effective delivery system.
Keywords: Anthrax toxin; Tumor endothelial marker 8; Liposomes; Cell penetrating peptide; Dual-ligand;
Novel NSAIDs ophthalmic formulation: Flurbiprofen axetil emulsion with low irritancy and improved anti-inflammation effect by Jinqiu Shen; Li Gan; Chunliu Zhu; Xinxin Zhang; Yang Dong; Min Jiang; Jiabi Zhu; Yong Gan (115-122).
The aim of this study was to design and formulate a novel low-irritant NSAIDs ophthalmic emulsion of flurbiprofen axetil (FBA), the prodrug of flurbiprofen (FB). FBA ophthalmic emulsion (FBA-EM) was prepared by high-pressure homogenization with caster oil as oil phase and tween 80 as emulsifying agent. Results from the stability evaluation suggested the protect effect of oil droplets on the stability of FBA. Compared with FBA-oil solution, the AUC 0 → 10 h of FB in aqueous humor administered in FBA-EMs exhibited 6.7-fold (F2), 4.5-fold (F3) and 4.6-fold (F4) increase. With the increment of oil content, the MRT also prolonged, which of FBA-EM F2–F4 were 5.14 ± 2.23, 5.73 ± 3.35 and 8.71 ± 0.94 h, respectively. No significant difference was found between the ocular bioavailability of FBA-EM F2 and 0.03% FB-Na eye drops. Ocular irritation evaluation revealed that FBA-EM F2 had better ocular biocompatibility than 0.03% FB-Na eye drops, even though the FBA concentration was up to 0.1%. Intraocular anti-inflammation effect evaluation showed that FBA-EM F2 had a quite good anti-inflammation effect. In conclusion, FBA-EM F2 with elevated FBA concentration to be 0.1% might represent a promising NSAIDs ophthalmic emulsion with low irritancy and improved anti-inflammation effect.
Keywords: Flurbiprofen axetil; Emulsion; Aqueous humor pharmacokinetics; Ocular irritation; Anti-inflammation; Uveitis;
Facilitated nanoscale delivery of insulin across intestinal membrane models by Camile B. Woitiski; Bruno Sarmento; Rui A. Carvalho; Ronald J. Neufeld; Francisco Veiga (123-131).
Cross-sections of intestinal mucosa of Wistar rats showing internalization of nanoencapsulated insulin observed by combination of FITC-insulin and RBITC-alginate nanoparticles in jejunum (scale bar 50 μm) (left) and in three-dimensional image (right).The effect of nanoparticulate delivery system on enhancing insulin permeation through intestinal membrane was evaluated in different intestinal epithelial models using cell cultures and excised intestinal tissues. Multilayered nanoparticles were formulated by encapsulating insulin within a core consisting of alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin. Insulin permeation through Caco-2 cell monolayer was enhanced 2.1-fold, facilitated by the nanoparticles compared with insulin alone, 3.7-fold through a mucus-secreting Caco-2/HT29 co-culture, and 3.9-fold through excised intestinal mucosa of Wistar rats. Correlation of Caco-2/HT29 co-culture cells with the animal-model intestinal membrane demonstrates that the mucus layer plays a significant role in determining the effectiveness of oral nanoformulations in delivering poorly absorbed drugs. Albumin was applied to the nanoparticles as outermost coat to protect insulin through shielding from proteolytic degradation. The effect of the albumin layering on insulin permeation was compared with albumin-free nanoparticles that mimic the result of albumin being enzymatically removed during gastric and intestinal transport. Results showed that albumin layering is important toward improving insulin transport across the intestinal membrane, possibly by stabilizing insulin in the intestinal conditions. Transcellular permeation was evidenced by internalization of independently labeled insulin and nanoparticles into enterocytes, in which insulin appeared to remain associated with the nanoparticles. Transcellular transport of insulin through rat intestinal mucosa may represent the predominant mechanism by which nanoparticles facilitate insulin permeation. Nanoformulations demonstrated biocompatibility with rat intestinal mucosa through determination of cell viability via monitoring of mitochondrial dehydrogenases. Insulin permeation facilitated by the biocompatible nanoparticles suggests a potential carrier system in delivering protein-based drugs by the oral route.
Keywords: Insulin; Nanoparticles; Permeation; Cell culture; Intestinal mucosa;
PEG liposomalization of paclitaxel improved its in vivo disposition and anti-tumor efficacy by Yuta Yoshizawa; Yusuke Kono; Ken-ichi Ogawara; Toshikiro Kimura; Kazutaka Higaki (132-141).
To find out potent paclitaxel (PTX) formulations for cancer chemotherapy, we formulated PTX in O/W emulsion and liposome selected as candidates of nanocarriers for PTX. Surface modification of these nanoparticles with polyethylene glycol (PEG) improved their in vivo behavior, but the effect of PEGylation on the pharmacokinetics of emulsion was not so remarkable and the release of PTX from emulsion was found to be very fast in blood circulation, indicating that emulsion would not be an adequate formulation for PTX. On the other hand, AUC of PEG liposome was 3.6 times higher than that of naked liposome after intravenous injection into normal rats due to the lower disposition into the reticuloendothelial system tissues such as liver and spleen. Since PEG liposome was able to stably encapsulate PTX in blood, AUC of PTX was also extensively enhanced after intravenous dosing of PTX-PEG liposome into normal rats. In the in vivo studies utilizing Colon-26 solid tumor-bearing mice, it was confirmed that PTX-PEG liposome delivered significantly larger amount of PTX to tumor tissue and provided more excellent anti-tumor effect than PTX-naked liposome. These results suggest that PEG liposome would serve as a potent PTX delivery vehicle for the future cancer chemotherapy.
Keywords: Paclitaxel; PEG emulsion; PEG liposome; EPR effect; Passive targeting;
Physicochemical characterization of drug-loaded rigid and elastic vesicles by Tomonobu Uchino; Fons Lefeber; Gert Gooris; Joke Bouwstra (142-147).
Ketorolac loaded rigid and elastic vesicles were prepared by sonication and the physicochemical properties of the drug loaded-vesicle formulations were examined. Rigid and elastic vesicles were prepared from the double chain surfactant sucrose-ester laurate (L-595) and the single chain surfactant octaoxyethylene-laurate ester (PEG-8-L). Sulfosuccinate (TR-70) was used as a negative charge inducer. Evaluation of the prepared vesicle was performed by dynamic light scattering, extrusion and by 1H NMR (T 2 relaxation studies). The vesicles mean size varied between 90 and 150 nm. The elasticity of the vesicles was enhanced with increasing PEG-8-L/L-595 ratio, while an increase in loading of ketorolac resulted in a reduction in vesicle elasticity. 1H NMR measurements showed that the molecular mobility of ketorolac was restricted, which indicates that ketorolac molecules were entrapped within the vesicle bilayers. The T 2 values of the aromatic protons of ketorolac increased gradually at higher PEG-8-L levels, indicating that ketorolac mobility increased in the vesicle bilayer. The chemical stability of ketorolac was dramatically improved in the vesicle formulation compared to a buffer solution. The strong interactions of ketorolac with the bilayers of the vesicles might be the explanation for this increased stability of ketorolac.
Keywords: Ketorolac; Vesicle; Elasticity; 1H NMR;