Interactions in Aqueous Mixtures of Cationic Hydroxyethyl Cellulose and Different Anionic Bile Salts.

It is known that the reduction of blood cholesterol can be accomplished through foods containing a large number of dietary fibers; this process is partially related to the binding of bile salt to fibers. To gain new insights into the interactions between dietary fibers and bile salts, this study investigates the interactions between cationic hydroxyethyl cellulose (catHEC) and sodium deoxycholate (NaDC) or sodium cholate (NaC), which have a similar structure. Turbidity measurements reveal strong interactions between catHEC and NaDC, and under some conditions, macroscopic phase separation occurs. In contrast, the interactions with NaC are weak. At a catHEC concentration of 2 wt %, incipient phase separation is approached at concentrations of NaC and NaDC of 32.5 and 19.3 mM, respectively. The rheological results show strong interactions and a prominent viscosification effect for the catHEC/NaDC system but only moderate interactions for the catHEC/NaC system. Both cryogenic transmission electron microscopy and small-angle X-ray scattering results display fundamental structural differences between the two systems, which may explain the stronger interactions in the presence of NaDC. The surmise is that the extended structures formed in the presence of NaDC can easily form connections and entanglements in the network.

Design of novel polyurethane-based ionene nanocarriers for cancer therapy: Synthesis, in-vitro, and in-vivo studies.

New strategies for constructing versatile nanocarriers are needed for cancer therapy to overcome the multiple challenges of targeted delivery. This work explores the advantages of polyurethane with main-chain quaternary ammonium salt moieties (ionene) as a novel carrier for targeted drug delivery. We have developed a novel cationic soybean oil-based polyurethane ionene nanocarrier (CPUI) that can act as an effective anticancer agent and efficiently deliver the anticancer drug 5-fluorouracil (5FU). We also report a potential anticancer drug delivery system targeting the folate receptor. In vitro experiments with blank CPUI carriers on the 4T1 (mouse breast cancer cell line) and the NIH-3T3 (mouse fibroblast cell line) revealed high cytotoxicity for the cancer cells but only low cytotoxicity for the normal fibroblast cells. The CPUI nanoparticles were readily loaded with 5FU (5FU-CPUI) in water using electrostatic interactions between the cationic quaternary ammonium groups of ionene and the anionic 5FU. The in vivo study in mice with tumors showed that the blank CPUI carriers significantly inhibited tumor growth, even more than the free drug (5FU). The inhibitory effect on tumor growth was slightly enhanced when the carriers were loaded with 5FU. The prepared nanoparticles had a high loading capacity of 41.8 %. Further enhancement of the inhibitory effect was observed when folic acid (FA) was added as a targeting moiety to the system via ion exchange with the bromine counterion of the quaternary ammonium moieties. The results suggest that the efficacy of FA-CPUI-5FU nanoparticles as vehicles for drug delivery can be enhanced via folate receptor (FR) mediated endocytosis in 4T1 cells and these novel nanocarriers may provide a potential platform for effective targeted drug delivery to tumor tissue and breast cancer therapy in the clinic.

Structural and Rheological Properties of Temperature-Responsive Amphiphilic Triblock Copolymers in Aqueous Media.

Thermoresponsive amphiphilic biodegradable block copolymers of the type poly(ε-caprolactone-co-lactide)-poly(ethylene glycol)-poly(ε-caprolactone-co-lactide) (PCLA-PEGm-PCLA) have great potential for various biomedical applications. In the present study, we have surveyed the effects of PEG spacer length (m = 1000 and 1500), temperature, and polymer concentration on the self-assembling process to form supramolecular structures in aqueous solutions of the PCLA-PEGm-PCLA copolymer. This copolymer has a lower critical solution temperature, and the cloud point depends on both concentration and PEG length. Thermoreversible hydrogels are formed in the semidilute regime; the gel windows in the phase diagrams can be tuned by the concentration and length of the PEG spacer. The rheological properties of both dilute and semidilute samples were characterized; especially the sol-to-gel transition was examined. Small-angle neutron scattering (SANS) experiments reveal fundamental structural differences between the two copolymers for both dilute and semidilute samples. The intensity profiles for the copolymer with the long PEG spacer could be described by a spherical core-shell model over a broad temperature domain, whereas the copolymer with the short hydrophilic spacer forms rod-like species over an extended temperature range. This finding is supported by cryo-TEM images. At temperatures approaching macroscopic phase separation, both copolymers seem to assume extended rod-like structures.

Novel Structural Changes during Temperature-Induced Self-Assembling and Gelation of PLGA-PEG-PLGA Triblock Copolymer in Aqueous Solutions.

The thermoresponsive amphiphilic block copolymer poly(d,l-lactic acid-co-glycolic acid)-block-poly(ethylene glycol)-block-poly(d,l-lactic acid-co-glycolic acid) (PLGA-PEGn -PLGA), which exhibits a reversible temperature-induced sol-gel transition at higher polymer concentrations in aqueous solution has attached a great deal of interest because of its potential in biomedical applications. In the present work, the length of the hydrophobic PLGA blocks is kept constant, whereas the length of the hydrophilic PEG block is altered and this variation has a pronounced impact on the phase behavior of the aqueous samples and the structure of the polymer. A short PEG block promotes gelation at a low temperature, whereas a longer PEG block shifts the gelation point to higher temperature. By using a combination of turbidity, rheology, and small angle neutron scattering (SANS) methods, the authors have revealed dramatic temperature effects. In dilute solution, the SANS experiments expose asymmetric ellipsoid structures for the copolymer with the short PEG-spacer, whereas spherical core-shell structure is observed for the polymer with long PEG-spacer. In the semidilute concentration regime, SANS measurements disclose similar profiles for the two copolymers. In a broad temperature interval, the transition from spherical core-shell micelles to cylindrical structure and packing of cylinders is observed.

Characterization of omega-3 tablets.

Omega-3 nutraceuticals are extensively used as health supplements worldwide. Various administration forms for delivery of omega-3 are available. However, the niche omega-3 tablets have so far remained unexplored. In this work tablets containing 25-40% (w/w) omega-3 oil as triglycerides or ethyl esters were prepared utilizing a direct compaction grade powder with ß-cyclodextrin as encapsulating agent. It was found that powders with up to 35% (w/w) triglyceride oil and 30% (w/w) ethyl ester oil, respectively, can be directly compressed into tablets of excellent quality. Physical properties of omega-3 containing powders and tablets are described. The powder X-ray diffractograms of the powders and crushed tablets show evidence of the formation of new crystalline phases not present in ß-cyclodextrin. In addition, (1)H NMR data suggest that the ethyl esters form inclusion complexes with ß-cyclodextrin. Compaction of other, commercially available, omega-3 powders was performed as a comparison and deemed unsuccessful.

Characterization of oligosaccharide-functionalized hyperbranched poly(ethylene imine) and their complexes with retinol in aqueous solution.

Structure, internal density distribution, and size of hyperbranched poly(ethylene imine) (PEI) functionalized with various amounts of maltose (PEI-Mal) in phosphate buffer were studied by small angle X-ray scattering (SAXS) and dynamic light scattering (DLS). The value of pH was varied in the range from 3 to 9. Virtually no effect of pH on the nanostructure was found in this interval. The SAXS results revealed a broad segmental radial density distribution, i.e. a "fluffy" globular structure rather than a distinct core-shell structure with a high-density compact core and a low-density corona. This suggests that the maltose units are rather evenly distributed both in the interior and on the surface of the species with a PEI-core of molar mass of 25,000g/mol. The DLS measurements showed that the overall size of the PEI-Mal derivatives increased as the number of maltose units in the PEI-Mal structures rises. The interaction of the hydrophobic model drug retinol with PEI or PEI-Mal derivatives was also investigated. The UV-visible spectroscopy results disclosed that the solubility of retinol in the phosphate buffer is very poor and it takes a very long time to solubilize retinol. Moreover, retinol induces aggregation of dendritic glycopolymers where the growth of aggregates occurs continuously over several days and then remains virtually constant.

Compactible powders of omega-3 and ß-cyclodextrin.

Omega-3 fatty acids are used in both nutraceuticals and pharmaceuticals in the form of triglycerides and ethyl esters. Administration forms available for omega-3 include bulk oil, soft gel capsules, emulsions and some powder compositions. Cyclodextrins are substances well known for their ability to encapsulate lipophilic molecules. In the present work, powders loaded with omega-3 oil, ranging from 10 to 40% (w/w), have been prepared by vacuum drying, freeze drying or spray granulation of aqueous mixtures of omega-3 oil and ß-cyclodextrin. The powders were found to be partially crystalline by powder X-ray diffraction and to contain crystalline phases not present in pure ß-cyclodextrin, indicating true complexation. The compactibility of the powders has been explored, revealing that a dry and compactible powder can be prepared from various omega-3 oils and ß-cyclodextrin. Spray granulation was found to be the superior drying method for the preparation of compactible powders.

The influence of polysorbate 80 on the radiochemical synthesis of a PET tracer in the FASTlab.

PURPOSE: The aim of current study was to investigate the influence of a common non-ionic surfactant, polysorbate 80 (PS80), on radioactive labelling process of a novel PET tracer, [(18)F]Flutemetamol. METHODS: Ferrous oxidation-xylenol orange (FOX) assay, in addition to UV/VIS and (1)H NMR spectroscopies were applied to characterise the composition of the PS80 solution after storage. Multivariate Curve Resolution (MCR) and PLS analysis was used to establish correlation between quality of the PS80 solution and the RCP obtained after labelling. RESULTS: The levels of unsaturated fatty acid moieties of PS80 were negatively correlated to RCP of [(18)F]Flutemetamol after synthesis. This explains the slight increase in RCP when stored PS80 solutions were applied in the synthesis. The mechanism behind this observation is suggested to be related to radiation induced radical formation in the unsaturated fatty acids, which subsequently causes instability of the PET tracer. UV/VIS spectroscopy was demonstrated to have the ability as a possible control tool for quality assurance of the studied radioactive labelling process. CONCLUSIONS: The presence of unsaturated fatty acid moieties in PS80 was found to be one of the most important factors responsible for the reduction in RCP of [(18)F]Flutemetamol after synthesis.

Sustained release of naltrexone from poly(n-isopropylacrylamide) microgels.

The release of the opioid antagonist naltrexone from neutral poly(N-isopropylacrylamide) (PNIPAAM) microgels and negatively charged PNIPAAM microgels containing acrylic acid groups (PNIPAAM-co-PAA) has been studied at various microgel and drug concentrations. The release curves were found to be well represented by the Weibull equation. The release rates were observed to be dependent on the microgel concentration. At most conditions, the release from the charged microgels was slower than for the neutral microgels. In addition, the charged microgels exhibited a release lag time, which was dependent on the microgel concentration. No significant lag time could be observed for the neutral microgels. Increasing the naltrexone concentration did not significantly affect the release rates from the neutral microgels, but the release from the charged microgels became faster. The microgels did not exhibit any significant cytotoxic effect on HeLa cells at the tested concentrations.

Classification of structurally related commercial contrast media by near infrared spectroscopy.

Near infrared spectroscopy (NIRS) is a non-destructive measurement technique with broad application in pharmaceutical industry. Correct identification of pharmaceutical ingredients is an important task for quality control. Failure in this step can result in several adverse consequences, varied from economic loss to negative impact on patient safety. We have compared different methods in classification of a set of commercially available structurally related contrast media, Iodixanol (Visipaque(®)), Iohexol (Omnipaque(®)), Caldiamide Sodium and Gadodiamide (Omniscan(®)), by using NIR spectroscopy. The performance of classification models developed by soft independent modelling of class analogy (SIMCA), partial least squares discriminant analysis (PLS-DA) and Main and Interactions of Individual Principal Components Regression (MIPCR) were compared. Different variable selection methods were applied to optimize the classification models. Models developed by backward variable elimination partial least squares regression (BVE-PLS) and MIPCR were found to be most effective for classification of the set of contrast media. Below 1.5% of samples from the independent test set were not recognized by the BVE-PLS and MIPCR models, compared to up to 15% when models developed by other techniques were applied.

Thermoresponsive polymers as gene and drug delivery vectors: architecture and mechanism of action.

INTRODUCTION: This topic is important as it allows for improved specificity in drug delivery, providing possibilities for reduced side effects, and thereby improved pharmacotherapy. As a wealth of different polymers and mechanisms of action has been suggested, a systematic overview of the field is of current importance. AREAS COVERED: This article presents an overview over a selection of thermoresponsive polymers suitable as excipients in systems for gene and drug delivery with particular emphasis on the influence of polymer structure, composition, molecular weight (MW) and architecture on the responsive mechanisms. Due to the immense number of reports on these increasingly popular materials, focus has been restricted to the use of micelle-forming polymers with a lower critical solution temperature, temperature-responsive hydrogels for drug delivery applications and temperature-sensitive polymers as non-viral vectors for polynucleotide delivery. Specific examples covered are poly-(N-isopropylacrylamide) (PNIPAAM), Pluronics and their derivatives. It is concluded that the studies constitute an excellent platform for development of thermoresponsive systems with improved gene and drug delivery properties. EXPERT OPINION: A thorough knowledge of factors important for loading efficiency and drug release is necessary to be able to develop optimal nano-carriers for the future. Other issues that are not fully understood is how small the carriers need to be, and which manufacturing procedures should be used.

Temperature-responsive cationic block copolymers as nanocarriers for gene delivery.

Cationic block copolymers have been regarded as promising alternatives to the use of viral vectors for gene delivery. In this work, poly(N-isopropylacrylamide)n-block-poly((3-acrylamidopropyl)trimethylammonium chloride)m (PNIPAAMn-b-PAMPTMA(+)m) block copolymers with n=48 or 65 and m=6, 10 or 20 were synthesized and evaluated in terms of their potential for in vitro transfection of HeLa cells. These block copolymers collapse above a phase transition temperature, allowing the entrapment of the DNA molecules they are adsorbed to. The transfection efficiency increased with polymer concentration and was higher in the presence of a long PNIPAAM block and for a short charged block. In general, increasing the length of the charged block decreased the transfection efficiency. Additionally, polymer-DNA complexes (polyplexes) formed at lower polymer/DNA charge ratios caused lower cell toxicity levels. All polymers were shown to efficiently protect the DNA, even when they were present at low concentrations. At 37°C, the polyplexes mostly formed structures with size ranging from 100 to 500nm. The results also showed that the thermoresponsive contraction of PNIPAAM causes the charged block segments to be pressed out to the surface. The formation of compact structures seems to be a key factor in achieving high transfection efficiency.

In vitro cytotoxicity of a thermoresponsive gel system combining ethyl(hydroxyethyl) cellulose and lysine-based surfactants.

The cytotoxicity of three lysine-derived surfactants with a gemini-like structure was evaluated on HeLa cells. The half maximal effective concentration (EC(50)) was estimated from the dose-response curves and the values indicated an increase in toxicity with the increase in alkyl chain length. The shorter chain length surfactant (C(6)) was shown to be less cytotoxic than sodium dodecyl sulfate (SDS), and all the lysine-derived surfactants were less toxic than the cationic cetyl trimethylammonium bromide (CTAB). The presence of ethyl (hydroxyethyl) cellulose (EHEC), shown previously to form thermoresponsive gels in combination with these surfactants, was found to contribute to a lower toxicity on HeLa cells. The conjecture is that the polymer-surfactant interactions in forming mixed micelles are the key contributors to the enhanced biocompatibility of the hydrogels. The most promising results were obtained in the presence of either the most hydrophilic surfactant or in the presence of the longest chain-length surfactant. For the latter, very low concentrations are needed to induce a sol-gel transition of EHEC semi-dilute solutions.

Thermoresponsive hydrogels with low toxicity from mixtures of ethyl(hydroxyethyl) cellulose and arginine-based surfactants.

Ethyl(hydroxyethyl) cellulose (EHEC) is known to form hydrogels in water at elevated temperatures in the presence of an ionic surfactant. In this paper, the potential use of arginine-based surfactants is explored considering the production of a low toxicity thermoresponsive hydrogel for pharmaceutical and biomedical applications. The interactions between EHEC and the monomeric surfactant N(α)-lauroyl-L-arginine methyl ester (LAM) and two gemini surfactants N(α),N(ω)-bis(N(α)-acylarginine) α,ω-dialkyl amides were evaluated by Rheo-Small Angle Light Scattering measurements. The complex viscosity of the systems was dependent on surfactant concentration and temperature. Under specific conditions, soft gels of homogeneous structure were produced. The cloud point (CP) of the EHEC-LAM system varied significantly with surfactant concentration, while only moderate CP changes were found in the presence of the gemini surfactants. Finally, the effect of the surfactants on the viability of a human cell line was evaluated. Despite the lower toxicity of LAM, the superior gel forming efficiency of the gemini surfactants at lower concentrations revealed their advantageous suitability as components of a biocompatible thermoresponsive gel system.

Strategies for multivariate modeling of moisture content in freeze-dried mannitol-containing products by near-infrared spectroscopy.

Accurate determination of residual moisture content of a freeze-dried (FD) pharmaceutical product is critical for prediction of its quality. Near-infrared (NIR) spectroscopy is a fast and non-invasive method routinely used for quantification of moisture. However, several physicochemical properties of the FD product may interfere with absorption bands related to the water content. A commonly used stabilizer and bulking agent in FD known for variation in physicochemical properties, is mannitol. To minimize this physicochemical interference, different approaches for multivariate correlation between NIR spectra of a FD product containing mannitol and the corresponding moisture content measured by Karl Fischer (KF) titration have been investigated. A novel method, MIPCR (Main and Interactions of Individual Principal Components Regression), was found to have significantly increased predictive ability of moisture content compared to a traditional PLS approach. The philosophy behind the MIPCR is that the interference from a variety of particle and morphology attributes has interactive effects on the water related absorption bands. The transformation of original wavelength variables to orthogonal scores gives a new set of variables (scores) without covariance structure, and the possibility of inclusion of interaction terms in the further modeling. The residual moisture content of the FD product investigated is in the range from 0.7% to 2.6%. The mean errors of cross validated prediction of models developed in the investigated NIR regions were reduced from a range of 24.1-27.6% for traditional PLS method to 15.7-20.5% for the MIPCR method. Improved model quality by application of MIPCR, without the need for inclusion of a large number of calibration samples, might increase the use of NIR in early phase product development, where availability of calibration samples is often limited.

Influence of liposomal formulation variables on the interaction with Candida albicans in biofilm; a multivariate approach.

Candida albicans is a species commonly associated with biofilm formation. The aim of this study was to identify liposomal formulation variables influencing the adhesion of liposomes to C. albicans in biofilm. C. albicans was grown on microtiter plates. Charged liposomes containing a fluorescent phospholipid (fatty acid labeled) were adsorbed onto biofilms of C. albicans in the wells. The adsorption was quantified by fluorescence measurements. Statistical experimental design and multivariate evaluation were used in the studies. The liposomal formulation factors investigated were the type of the main phospholipid (egg-PC, DMPC, and DPPC), the amount of charged component in the liposomes, and the type of the charged lipid (diacyl-TAP, DC-chol, diacyl-PA, diacyl-PG, diacyl-PS, and PI). Full factorial mixed levels designs were created. Saturated positively charged liposomes, with diacyl-TAP as the charged component and a low level of positive charge, was found to be the best choice for interaction with C. albicans. When formulating negatively charged liposomes, liposomes with DPPC as the main lipid adsorbed significantly better than liposomes with egg-PC. The amount of charge and the nature of the charged component were not found to influence the adsorption of the negatively charged liposomes to C. albicans. No synergy was detected between any of the formulation variables studied.

Immersion coating of pellet cores consisting of chitosan and calcium intended for colon drug delivery.

Biopolymers such as pectin, alginate, and chitosan have a great potential in colon drug delivery. The aim of this study was to produce pellets with calcium and chitosan in the core and then by an interfacial complexation reaction coat the cores with pectin or alginate in combination with calcium or chitosan. Pellets with calcium in the core acted as a reference. The drug release was investigated in environments mimicking the stomach and the small intestine. The morphology of the coatings indicated a more wrinkled and irregular structure for coatings composed of pectin or alginate in combination with chitosan compared to the coat consisting of alginate in combination with calcium. The results from the drug release experiments showed that all the investigated coatings, especially with alginate, slowed down the drug release compared to the uncoated cores. The release from the chitosan-containing pellets was higher than the reference. The swelling studies revealed a high degree of swelling of the core consisting of chitosan. This probably explains the higher drug release from the coated chitosan pellets.

Mucoadhesion and drug permeability of free mixed films of pectin and chitosan: an in vitro and ex vivo study.

The objective of this study was to identify the important factors for the drug permeability and mucoadhesion of casted free pectin/chitosan combination films. The factors varied were: the type of pectin (low and high methoxyl pectin) and the ratio pectin:chitosan (25:75, 50:50 and 75:25). The model drug used for measuring drug permeability was paracetamol. A texture analyzer was used for measuring mucoadhesion by using two different setups: (1) in vitro tensile tests measuring the detachment force of films versus a mucin dispersion and (2) ex vivo shear tests measuring the friction forces between pre-hydrated films and fresh porcine small intestine, with the system immersed in phosphate buffer, pH 6.8. The type of pectin used in the combination films did not have a significant effect on the drug permeability. The ex vivo mucoadhesion test revealed significant differences between low and high methoxyl pectin only for the 50:50 pectin:chitosan films. For that type of film, the peak and friction forces were highest for high methoxyl pectin. Both the mucoadhesion and drug permeability generally increased with decreasing amounts of pectin relative to chitosan in the films.

Effect of pectin type and plasticizer on in vitro mucoadhesion of free films.

The objective was to measure and compare the specific and general mucin interaction of plasticized and unplasticized pectin films. The pectin types differed in the type and degree of substitution. Mucoadhesive properties were measured by using a texture analyzer. Pectin with an intermediate degree of methoxylation (36%) displayed substantially higher general and specific mucin interaction than amidated, acetylated, and high methoxylated pectin. This was explained with extensive hydrogen bonding in addition to favorable wetting properties. When comparing all plasticized films to all unplasticized films, a consistent and statistically significant increase in the peak force was observed on adding an effective plasticizer.

In vitro measurements of mucoadhesive properties of six types of pectin.

The objective of this study was to measure and compare the specific- and general mucin interaction of six pectin types from three manufacturers, differing mainly in the degree of methoxylation and degree of amidation. Mucoadhesive properties were measured using a texture analyzer. It was found that an intermediate degree of methoxylation (35 and 36%) improved the specific mucin interaction. Amidation did not increase mucin interaction. Samples from different manufacturers did not alter these conclusions. This study indicates that the general classification of pectin as a poor mucoadhesive, without differentiating between the amount and type of substituents, probably is an oversimplification.