Controlled release of MT-1207 using a novel gastroretentive bilayer system comprised of hydrophilic and hydrophobic polymers.

In the present study, novel gastroretentive bilayer tablets were developed that are promising for the once-a-day oral delivery of the drug candidate MT-1207. The gastroretentive layer consisted of a combination of hydrophilic and hydrophobic polymers, namely polyethylene oxide and Kollidon® SR. A factorial experiment was conducted, and the results revealed a non-effervescent gastroretentive layer that, unlike most gastroretentive layers reported in the literature, was easy to prepare, and provided immediate tablet buoyancy (mean floating lag time of 1.5 s) that lasted over 24 h in fasted state simulated gastric fluid (FaSSGF) pH 1.6, irrespective of the drug layer, thereby allowing a 24-hour sustained release of MT-1207 from the drug layer of the tablets. Furthermore, during in vitro buoyancy testing of the optimised bilayer tablets in media of different pH values (1.0, 3.0, 6.0), the significant difference (one-way ANOVA, p < 0.001) between the respective total floating times indicated that stomach pH effects on tablet buoyancy are important to be considered during the development of non-effervescent gastroretentive formulations and the choice of dosing regimen. To the best of our knowledge, this has not been reported before, and it should probably be factored in when designing dosing regimens. Finally, a pharmacokinetic study in Beagle dogs indicated a successful in vivo 24-hour sustained release of MT-1207 from the optimised gastroretentive bilayer tablet formulations with the drug plasma concentration remaining above the estimated minimum effective concentration of 1 ng/mL at the 24-hour timepoint and also demonstrated the gastroretentive capabilities of the hydrophilic and hydrophobic polymer combination. The optimised formulations will be forwarded to clinical development.

In vitro and in vivo evaluation of a sustained-release once-a-day formulation of the novel antihypertensive drug MT-1207.

Hypertension is one of the most common chronic cardiovascular disorders. Sustained-release formulations are developed to maintain drug therapeutic levels throughout the treatment of hypertension, to promote patient compliance and improve patient outcomes. We have developed and tested in in vivo trials a once-a-day tablet formulation for the novel antihypertensive drug MT-1207. The tablets based upon a hydrophilic polymer matrix underwent post-compression parameter and physicochemical characterisations, along with in vitro drug release testing. The most promising formulation containing 31% w/w HPMC K15M gave a 24-hour release of MT-1207 with an almost constant release rate up to 20 hours. Follow in in vivo studies were carried out in Beagle dogs for the optimised sustained-release tablets in comparison to immediate-release tablets. The results showed that a sustained release of MT-1207 from the new formulation was achieved with a drug t1/2 2-2.5 times longer than the immediate-release tablets. Moreover, the AUC0-24h values of both sustained- and immediate-release tablets were identical at the same dose of 30 mg, indicating that the same amount of drug was absorbed in each case. For treatments based upon MT-1207, this development is significant for future commercial exploitation via scale-up and further trials, and for improved patient outcomes.

Mucoadhesive chitosan-coated nanostructured lipid carriers for oral delivery of amphotericin B.

This study describes the properties of an amphotericin B-containing mucoadhesive nanostructured lipid carrier (NLC), with the intent to maximize uptake within the gastrointestinal tract. We have reported previously that lipid nanoparticles can significantly improve the oral bioavailability of amphotericin B (AmpB). On the other hand, the aggregation state of AmpB within the NLC has been ascribed to some of the side effects resulting from IV administration. In the undissolved state, AmpB (UAmpB) exhibited the safer monomeric conformation in contrast to AmpB in the dissolved state (DAmpB), which was aggregated. Chitosan-coated NLC (ChiAmpB NLC) presented a slightly slower AmpB release profile as compared to the uncoated formulation, achieving 26.1% release in 5 hours. Furthermore, the ChiAmpB NLC formulation appeared to prevent the expulsion of AmpB upon exposure to simulated gastrointestinal pH media, whereby up to 63.9% of AmpB was retained in the NLC compared to 56.1% in the uncoated formulation. The ChiAmpB NLC demonstrated mucoadhesive properties in pH 5.8 and 6.8. Thus, the ChiAmpB NLC formulation is well-primed for pharmacokinetic studies to investigate whether delayed gastrointestinal transit may be exploited to improve the systemic bioavailability of AmpB, whilst simultaneously addressing the side-effect concerns of AmpB.

Antifungal and Mucoadhesive Properties of an Orally Administered Chitosan-Coated Amphotericin B Nanostructured Lipid Carrier (NLC).

Surface-modified nanostructured lipid carriers (NLC) represent a promising mode of drug delivery used to enhance retention of drugs at absorption site. Formulated chitosan-coated amphotericin-B-loaded NLC (ChiAmp NLC) had a size of 394.4 ± 6.4 nm, encapsulation and loading efficiencies of 86.0 ± 3% and 11.0 ± 0.1% respectively. Amphotericin-B release from NLCs was biphasic with no changes in physical properties upon exposure to simulated gastrointestinal conditions. Antifungal properties of Amphotericin-B and ChiAmpB NLC were comparable but ChiAmpB NLC was twice less toxic to red blood cells and ten times safer on HT-29 cell lines. In vitro mucoadhesion data were observed ex vivo, where ChiAmpB NLC resulted in higher retention within the small intestine compared to the uncoated formulation. The data strongly offers the possibility of orally administering a non-toxic, yet effective Amphotericin-B nanoformulation for the treatment of systemic fungal infections.

Multiple Linear Regression Modeling To Predict the Stability of Polymer-Drug Solid Dispersions: Comparison of the Effects of Polymers and Manufacturing Methods on Solid Dispersion Stability.

Solid dispersions can be a successful way to enhance the bioavailability of poorly soluble drugs. Here 60 solid dispersion formulations were produced using ten chemically diverse, neutral, poorly soluble drugs, three commonly used polymers, and two manufacturing techniques, spray-drying and melt extrusion. Each formulation underwent a six-month stability study at accelerated conditions, 40 °C and 75% relative humidity (RH). Significant differences in times to crystallization (onset of crystallization) were observed between both the different polymers and the two processing methods. Stability from zero days to over one year was observed. The extensive experimental data set obtained from this stability study was used to build multiple linear regression models to correlate physicochemical properties of the active pharmaceutical ingredients (API) with the stability data. The purpose of these models is to indicate which combination of processing method and polymer carrier is most likely to give a stable solid dispersion. Six quantitative mathematical multiple linear regression-based models were produced based on selection of the most influential independent physical and chemical parameters from a set of 33 possible factors, one model for each combination of polymer and processing method, with good predictability of stability. Three general rules are proposed from these models for the formulation development of suitably stable solid dispersions. Namely, increased stability is correlated with increased glass transition temperature ( Tg) of solid dispersions, as well as decreased number of H-bond donors and increased molecular flexibility (such as rotatable bonds and ring count) of the drug molecule.

Extrusion 3D Printing of Paracetamol Tablets from a Single Formulation with Tunable Release Profiles Through Control of Tablet Geometry.

An extrusion-based 3D printer was used to fabricate paracetamol tablets with different geometries (mesh, ring and solid) from a single paste-based formulation formed from standard pharmaceutical ingredients. The tablets demonstrate that tunable drug release profiles can be achieved from this single formulation even with high drug loading (> 80% w/w). The tablets were evaluated for drug release using a USP dissolution testing type I apparatus. The tablets showed well-defined release profiles (from immediate to sustained release) controlled by their different geometries. The dissolution results showed dependency of drug release on the surface area/volume (SA/V) ratio and the SA of the different tablets. The tablets with larger SA/V ratios and SA had faster drug release. The 3D printed tablets were also evaluated for physical and mechanical properties including tablet dimension, drug content, weight variation and breaking force and were within acceptable range as defined by the international standards stated in the US Pharmacopoeia. X-ray powder diffraction, differential scanning calorimetry and attenuated total reflectance Fourier transform infrared spectroscopy were used to identify the physical form of the active and to assess possible drug-excipient interactions. These data again showed that the tablets meet USP requirement. These results clearly demonstrate the potential of 3D printing to create unique pharmaceutical manufacturing, and potentially clinical, opportunities. The ability to use a single unmodified formulation to achieve defined release profiles could allow, for example, relatively straightforward personalization of medicines for individuals with different metabolism rates for certain drugs and hence could offer significant development and clinical opportunities.

Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis.

Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer remains amorphous after coating of the rate controlling membrane, whether formed from an ethanol solution or an aqueous dispersion.

Mucoadhesive Chitosan-Pectinate Nanoparticles for the Delivery of Curcumin to the Colon.

In the present study, we report the properties of a mucoadhesive chitosan-pectinate nanoparticulate formulation able to retain its integrity in the milieu of the upper gastrointestinal tract and subsequently, mucoadhere and release curcumin in colon conditions. Using this system, we aimed to deliver curcumin to the colon for the possible management of colorectal cancer. The delivery system comprised of a chitosan-pectinate composite nanopolymeric with a z-average of 206.0 nm (±6.6 nm) and zeta potential of +32.8 mV (±0.5 mV) and encapsulation efficiency of 64%. The nanoparticles mucoadhesiveness was higher at alkaline pH compared to acidic pH. Furthermore, more than 80% release of curcumin was achieved in pectinase-enriched medium (pH 6.4) as opposed to negligible release in acidic and enzyme-restricted media at pH 6.8. SEM images of the nanoparticles after exposure to the various media indicate a retained matrix in acid media as opposed to a distorted/fragmented matrix in pectinase-enriched medium. The data strongly indicates that the system has the potential to be applied as a colon-targeted mucoadhesive curcumin delivery system for the possible treatment of colon cancer.

Imaging of Crystalline and Amorphous Surface Regions Using Time-of-Flight Secondary-Ion Mass Spectrometry (ToF-SIMS): Application to Pharmaceutical Materials.

The structure of a material, in particular the extremes of crystalline and amorphous forms, significantly impacts material performance in numerous sectors such as semiconductors, energy storage, and pharmaceutical products, which are investigated in this paper. To characterize the spatial distribution for crystalline-amorphous forms at the uppermost molecular surface layer, we performed time-of-flight secondary-ion mass spectroscopy (ToF-SIMS) measurements for quench-cooled amorphous and recrystallized samples of the drugs indomethacin, felodipine, and acetaminophen. Polarized light microscopy was used to localize crystallinity induced in the samples under controlled conditions. Principal component analysis was used to identify the subtle changes in the ToF-SIMS spectra indicative of the amorphous and crystalline forms for each drug. The indicators of amorphous and crystalline surfaces were common in type across the three drugs, and could be explained in general terms of crystal packing and intermolecular bonding, leading to intramolecular bond scission in the formation of secondary ions. Less intramolecular scission occurred in the amorphous form, resulting in a greater intensity of molecular and dimer secondary ions. To test the generality of amorphous-crystalline differentiation using ToF-SIMS, a different recrystallization method was investigated where acetaminophen single crystals were recrystallized from supersaturated solutions. The findings indicated that the ability to assign the crystalline/amorphous state of the sample using ToF-SIMS was insensitive to the recrystallization method. This demonstrates that ToF-SIMS is capable of detecting and mapping ordered crystalline and disordered amorphous molecular materials forms at micron spatial resolution in the uppermost surface of a material.

Disruption of diphenylalanine assembly by a Boc-modified variant.

Peptide-based biomaterials are key to the future of diagnostics and therapy, promoting applications such as tissue scaffolds and drug delivery vehicles. To realise the full potential of the peptide systems, control and optimisation of material properties are essential. Here we investigated the co-assembly of the minimal amyloid motif peptide, diphenylalanine (FF), and its tert-butoxycarbonyl (Boc)-modified derivative. Using Atomic Force Microscopy, we demonstrated that the co-assembled fibers are less rigid and show a curvier morphology. We propose that the Boc-modification of FF disrupts the hydrogen bond packing of adjacent N-termini, as supported by Fourier transform infrared and fluorescence spectroscopic data. Such rationally modified co-assemblies offer chemical functionality for after-assembly modification and controllable surface properties for tissue engineering scaffolds, along with tunable morphological vs. mechanical properties.

Long-Term Amorphous Drug Stability Predictions Using Easily Calculated, Predicted, and Measured Parameters.

The purpose of this study was to develop a predictive model of the amorphous stability of drugs with particular relevance for poorly water-soluble compounds. Twenty-five representative neutral poorly soluble compounds with a diverse range of physicochemical properties and chemical structures were systematically selected from an extensive library of marketed drug products. The physical stability of the amorphous form, measured over a 6 month period by the onset of crystallization of amorphous films prepared by melting and quench-cooling, was assessed using polarized light microscopy. The data were used as a response variable in a statistical model with calculated/predicted or measured molecular, thermodynamic, and kinetic parameters as explanatory variables. Several multiple linear regression models were derived, with varying balance between calculated/predicted and measured parameters. It was shown that inclusion of measured parameters significantly improves the predictive ability of the model. The best model demonstrated a prediction accuracy of 82% and included the following as parameters: melting and glass transition temperatures, enthalpy of fusion, configurational free energy, relaxation time, number of hydrogen bond donors, lipophilicity, and the ratio of carbon to heteroatoms. Good predictions were also obtained with a simpler model, which was comprised of easily acquired quantities: molecular weight and enthalpy of fusion. Statistical models are proposed to predict long-term amorphous drug stability. The models include readily accessible parameters, which are potentially the key factors influencing amorphous stability. The derived models can support faster decision making in drug formulation development.

Analysis of leaf surfaces using scanning ion conductance microscopy.

Leaf surfaces are highly complex functional systems with well defined chemistry and structure dictating the barrier and transport properties of the leaf cuticle. It is a significant imaging challenge to analyse the very thin and often complex wax-like leaf cuticle morphology in their natural state. Scanning electron microscopy (SEM) and to a lesser extent Atomic force microscopy are techniques that have been used to study the leaf surface but their remains information that is difficult to obtain via these approaches. SEM is able to produce highly detailed and high-resolution images needed to study leaf structures at the submicron level. It typically operates in a vacuum or low pressure environment and as a consequence is generally unable to deal with the in situ analysis of dynamic surface events at submicron scales. Atomic force microscopy also possess the high-resolution imaging required and can follow dynamic events in ambient and liquid environments, but can over exaggerate small features and cannot image most leaf surfaces due to their inherent roughness at the micron scale. Scanning ion conductance microscopy (SICM), which operates in a liquid environment, provides a potential complementary analytical approach able to address these issues and which is yet to be explored for studying leaf surfaces. Here we illustrate the potential of SICM on various leaf surfaces and compare the data to SEM and atomic force microscopy images on the same samples. In achieving successful imaging we also show that SICM can be used to study the wetting of hydrophobic surfaces in situ. This has potentially wider implications than the study of leaves alone as surface wetting phenomena are important in a range of fundamental and applied studies.

Combination of (M)DSC and surface analysis to study the phase behaviour and drug distribution of ternary solid dispersions.

PURPOSE: Miscibility of the different compounds that make up a solid dispersion based formulation play a crucial role in the drug release profile and physical stability of the solid dispersion as it defines the phase behaviour of the dispersion. The standard technique to obtain information on phase behaviour of a sample is (modulated) differential scanning calorimetry ((M)DSC). However, for ternary mixtures (M)DSC alone is not sufficient to characterize their phase behaviour and to gain insight into the distribution of the active pharmaceutical ingredient (API) in a two-phased polymeric matrix. METHODS: MDSC was combined with complementary surface analysis techniques, specifically time-of-flight secondary ion mass spectrometry (ToF-SIMS) and atomic force microscopy (AFM). Three spray-dried model formulations with varying API/PLGA/PVP ratios were analyzed. RESULTS: MDSC, TOF-SIMS and AFM provided insights into differences in drug distribution via the observed surface coverage for 3 differently composed ternary solid dispersions. CONCLUSIONS: Combining MDSC and surface analysis rendered additional insights in the composition of mixed phases in complex systems, like ternary solid dispersions.

Surface characteristics of spray-dried microspheres consisting of PLGA and PVP: relating the influence of heat and humidity to the thermal characteristics of these polymers.

In view of the increasing interest in injectable controlled release formulations for the treatment of chronic diseases, injectable polymeric microspheres consisting of a surface layer of poly(lactic-co-glycolic acid) (PLGA) and an underlying polyvinylpyrrolidone (PVP) layer were previously developed. The present study focuses on the influence of heat and humidity on the surface characteristics of these spray-dried PLGA/PVP microspheres. The response of the polymeric matrix to these factors will provide an insight into the expected release behavior and stability of the formulation. This should result in the development of a drug matrix with desired and tunable characteristics in terms of physicochemical stability and drug release profile, relevant in a later stage of research. Glass transition temperatures (Tgs) and miscibility behavior were analyzed by modulated differential scanning calorimetry (MDSC). Scanning electron microscopy (SEM) provided insight in particle morphology. Atomic force microscopy (AFM) was used to study the nanoscale topography and phase behavior of the samples. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS) were utilized for surface chemical analysis and quantification respectively. It could be concluded that the surface characteristics (chemical composition, phase behavior, and topography) of spray-dried PVP/PLGA microparticles were affected by exposure to heat and humidity. When exposed to these conditions, a surface rearrangement occurs whereby an increase of PVP at the surface is observed, coupled with a decrease in PLGA. This phenomenon can be explained based upon the relative thermal characteristics and consequent molecular mobility of the two polymers.

Curcumin-containing chitosan nanoparticles as a potential mucoadhesive delivery system to the colon.

In the present study, we investigate the mucoadhesive characteristics and release of the anticancer agent curcumin, contained in chitosan nanoparticles (CS-NPs). Such a system has potential therapeutic benefits in the treatment of colon cancer through prolonged retention and delivery. The CS-NPs were ionically gelled with tripolyphosphate (TPP) and registered an isoelectric pH of 6.2 (z-average diameter of 214 nm ± 1.0 nm). pH variations around the isoelectric point caused a reduction in CS-NPs electrical charge which correspondingly increased the z-average due to agglomeration. Curcumin release from CS-NPs was slowest at chitosan to TPP weight ratio of 3:1, with a significant retention (36%) at the end of 6 h. Adsorption isotherms of mucin on CS-NPs fitted both the Freundlich and Langmuir models, suggesting a monolayer-limited adsorption on heterogeneous sites with varied affinities. Encapsulated curcumin exerted an influence on the adsorption of mucin due to H-bonding as well as π-π interactions between the phenolic moieties of curcumin and mucin.

Near-field Raman spectroscopy of biological nanomaterials by in situ laser-induced synthesis of tip-enhanced Raman spectroscopy tips.

We report a new approach in tip-enhanced Raman spectroscopy (TERS) in which TERS-active tips with enhancement factors of ∼10(-5)× can be rapidly (1-3 min) produced in situ by laser-induced synthesis of silver nanoparticles at the tip apex. The technique minimizes the risks of tip contamination and damage during handling and provides in situ feedback control, which allows the prediction of the tip performance. We show that TERS tips produced by this technique enable the measurement of spatially resolved TERS spectra of self-assembled peptide nanotubes with a spatial resolution of ∼20 nm.

Understanding the interfacial properties of nanostructured liquid crystalline materials for surface-specific delivery applications.

Nonlamellar liquid crystalline dispersions such as cubosomes and hexosomes have great potential as novel surface-targeted active delivery systems. In this study, the influence of internal nanostructure, chemical composition, and the presence of Pluronic F127 as a stabilizer, on the surface and interfacial properties of different liquid crystalline particles and surfaces, was investigated. The interfacial properties of the bulk liquid crystalline systems with coexisting excess water were dependent on the internal liquid crystalline nanostructure. In particular, the surfaces of the inverse cubic systems were more hydrophilic than that of the inverse hexagonal phase. The interaction between F127 and the bulk liquid crystalline systems depended on the internal liquid crystalline structure and chemical composition. For example, F127 adsorbed to the surface of the bulk phytantriol cubic phase, while for monoolein cubic phase, F127 was integrated into the liquid crystalline structure. Last, the interfacial adsorption behavior of the dispersed liquid crystalline particles also depended on both the internal nanostructure and the chemical composition, despite the dispersions all being stabilized using F127. The findings highlight the need to understand the specific surface characteristics and the nature of the interaction with colloidal stabilizer for understanding and optimizing the behavior of nonlamellar liquid crystalline systems in surface delivery applications.

Investigations of the supramolecular structure of individual diphenylalanine nano- and microtubes by polarized Raman microspectroscopy.

Polarized Raman microspectroscopy and atomic force microscopy were used to obtain quantitative information regarding the molecular structure of individual diphenylalanine (FF) nano- and microtubes. The frequencies of the Raman spectral bands corresponding to the amide I (1690 cm(-1)) and amide III (1249 cm(-1)) indicated that the FF-molecules interact by hydrogen bonding at the N-H and not at the C═O sites. The calculated mean orientation angles of the principal axes of the Raman tensors (PARTs) obtained from the polarized Raman spectral measurements were 41 ± 4° for the amide I and 59 ± 5° for amide III. On the basis of the orientation of the PART for the amide I mode, it was found that the C═O bond is oriented at an angle of 8 ± 4° to the tube axis. These values did not vary significantly with the diameter of the tubes (range 400-1700 nm) and were in agreement with the molecular structure proposed previously for larger crystalline specimens.

The structure and formation of hydrogen-bonded molecular networks on Au(111) surfaces revealed by scanning tunnelling and torsional-tapping atomic force microscopy.

A comprehensive scanning probe microscopy study has been carried out to characterise 3,4,9,10-Perylenetetracarboxylic diimide (PTCDI)-melamine hydrogen-bonded networks deposited on Au(111)-surfaces. Both scanning tunnelling and atomic force microscopy were utilized. Such complementary analysis revealed a multilayered structure of the networks on the Au(111)-surface as opposed to a widely reported monolayer structure. Details of the network formation mechanism are presented. We have also demonstrated that despite the apparent network stability in ambient conditions it is unstable in aqueous solutions of pH 4.5 and 7.1.

ToF-SIMS analysis of chemical heterogenities in inkjet micro-array printed drug/polymer formulations.

Three different formulations comprising two drugs, felodipine and hydrochlorothiazide (HCT) and two polymers, poly(vinyl pyrolidone) (PVP) and poly(lactic-co-glycolic acid) (PLGA) were inkjet printed as micro-dot arrays and analysed on an individual micro-spot basis by time-of-flight secondary ion mass spectrometry (ToF-SIMS). For the HCT/PLGA formulation, the spots showed heterogeneity of the drug and other chemical constituents. To further investigate these heterogeneities, multivariate curve resolution was applied to the ToF-SIMS hyperspectral image datasets. This approach successfully identified distinct chemical components elucidating the HCT, PLGA, substrate material, and contaminants based on sulphur, phosphorous and sodium chloride. Spots printed using either of the drugs with PVP exhibited full substrate coverage and a uniform distribution of the active ingredient along with all other constituents within the printed spot area. This represents the preferred situation in terms of stability and controlling the release of a drug from a polymer matrix.