A method for the production of liquid capsules with the potential of modifying drug dose and release is presented. For the first time, the co-ordinated use of fused deposition modelling (FDM), 3D ...printing and liquid dispensing to fabricate individualised dosage form on demand in a fully automated fashion has been demonstrated. Polymethacrylate shells (Eudragit EPO and RL) for immediate and extended release were fabricated using FDM 3D printing and simultaneously filled using a computer-controlled liquid dispenser loaded with model drug solution (theophylline) or suspension (dipyridamole). The impact of printing modes: simultaneous shell printing and filling (single-phase) or sequential 3D printing of shell bottom, filling and shell cap (multi-phase), nozzle size, syringe volume, and shell structure has been reported. The use of shell thickness of 1.6 mm, and concentric architecture allowed successful containment of liquid core whilst maintaining the release properties of the 3D printed liquid capsule. The linear relationship between the theoretical and the actual volumes from the dispenser reflected its potential for accurate dosing (R2 = 0.9985). Modifying the shell thickness of Eudragit RL capsule allowed a controlled extended drug release without the need for formulation change. Owing to its low cost and versatility, this approach can be adapted to wide spectrum of liquid formulations such as small and large molecule solutions and obviate the need for compatibility with the high temperature of FDM 3D printing process. In a clinical setting, health care staff will be able to instantly manufacture in small volumes liquid capsules with individualised dose contents and release pattern in response to specific patient's needs.
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Hydrophilic matrices are an effective option for oral controlled release but can face challenges in terms of bioavailability and efficacy when used in conjunction with poorly soluble, weakly basic ...drugs. Attenuated total reflectance Fourier transform infrared (ATR–FTIR) imaging provides dynamic information relating to the location and chemical nature of both the sustained release matrix and the active pharmaceutical ingredient (API) during hydration/dissolution. In this study, we have identified a model system combining itraconazole (IT), a poorly soluble, weakly basic API that has pK a in the physiological range, and hydroxypropyl methylcellulose, which is a commonly used oral tablet matrix. This system was investigated to determine the swelling kinetics at different pH values at a fixed ionic strength and to facilitate the study of the influence of hydrating media pH on the drug particle movement (translocation). Using ATR–FTIR imaging, we were able to show that gel layer formation and swelling were independent of pH but highly dependent on the ionic strength of the hydrating medium in placebo tablets. When the ionic strength was fixed, gel layer formation and radial swelling were both shown to be pH-dependent when IT was incorporated into the matrix. This was verified using optical imaging. The chemical specificity of ATR–FTIR imaging permitted the observation of transformational changes of IT from the free base to the ionized form in the tablet core during hydration. This phenomenon was shown to be greater at pH 1.5 than at pH 7. ATR–FTIR imaging was able to follow drug particle translocation at both pH 1.5 and pH 7; however, the extent of migration away from the tablet core was shown to be greater at lower pH. The location of the translocated particles within the gel layer was different between the two studied pH values, with particles being located close to the swelling front at pH 7 and within the diffusion front at pH 1.5. In both pH environments, the translocated IT particles were shown to be predominantly in the free base form. No evidence of fully solubilized IT was observed in the surrounding medium because of the inherent aqueous solubility of IT being below the instrument detection limits. This work highlighted the value of utilizing a chemically specific spectroscopic tool to increase the understanding of the nature of the factors affecting the release of a pH-dependent, poorly soluble drug from a hydrophilic matrix at different pH values and permitted greater insights into what happens inside the polymer matrix during drug release.
Natively unfolded proteins play key roles in normal and pathological biochemical processes. Despite their importance for function, this category of proteins remains beyond the reach of classical ...structural biology because of their inherent conformational heterogeneity. We present a description of the intrinsic conformational sampling of unfolded proteins based on residue-specific ϕ/ψ propensities from loop regions of a folded protein database and simple volume exclusion. This approach is used to propose a structural model of the 57-aa, natively disordered region of the nucleocapsid-binding domain of Sendai virus phosphoprotein. Structural ensembles obeying these simple rules of conformational sampling are used to simulate averaged residual dipolar couplings (RDCs) and small-angle x-ray scattering data. This protein is particularly informative because RDC data from the equally sized folded and unfolded domains both report on the unstructured region, allowing a quantitative analysis of the degree of order present in this part of the protein. Close agreement between experimental and simulated RDC and small-angle x-ray scattering data validates this simple model of conformational sampling, providing a precise description of local structure and dynamics and average dimensions of the ensemble of sampled structures. RDC data from two urea-unfolded systems are also closely reproduced. The demonstration that conformational behavior of unfolded proteins can be accurately predicted from the primary sequence by using a simple set of rules has important consequences for our understanding of the structure and dynamics of the unstructured state.
In colloidal systems, the interplay between the short range attraction and long-range repulsion can lead to a low density associated state consisting of clusters of individual particles. Recently, ...such an equilibrium cluster phase was also reported for concentrated solutions of lysozyme at low ionic strength and close to the physiological pH. Stradner et al. (2004) Equilibrium cluster formation in concentrated protein solutions and colloids. Nature 432:492-495 found that the position of the low-angle interference peak in small-angle x-ray and neutron scattering (SAXS and SANS) patterns from lysozyme solutions was essentially independent of the protein concentration and attributed these unexpected results to the presence of equilibrium clusters. This work prompted a series of experimental and theoretical investigations, but also revealed some inconsistencies. We have repeated these experiments following the protein preparation protocols of Stradner et al. using several batches of lysozyme and exploring a broad range of concentrations, temperature and other conditions. Our measurements were done in multiple experimental sessions at three different high-resolution SAXS and SANS instruments. The low-ionic-strength lysozyme solutions displayed a clear shift in peak positions with concentration, incompatible with the presence of the cluster phase but consistent with the system of repulsively interacting individual lysozyme molecules. Within the decoupling approximation, the experimental data can be fitted using an effective interparticle interaction potential involving short-range attraction and long-range repulsion.
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Form changes during drug product processing can be a risk to the final product quality in terms of chemical stability and bioavailability. In this study, online Raman spectroscopy was ...used to monitor the form changes in real time during high shear wet granulation of Compound A, a highly soluble drug present at a high drug load in an extended release formulation. The effect of water content, temperature, wet massing time and drying technique on the degree of drug transformation were examined. A designed set of calibration standards were employed to develop quantitative partial least square regression models to predict the concentration of each drug form during both wet granulation and the drying process. Throughout all our experiments we observed complex changes of the drug form during granulation, manifest as conversions between the initial non-solvated form of Compound A, the hemi-hydrate form and the “apparent” amorphous form (dissolved drug). The online Raman data demonstrate that the non-solvated form converts to an “apparent” amorphous form (dissolved drug) due to drug dissolution with no appearance of the hemi-hydrate form during water addition stage. The extent of conversion of the non-solvated form was governed by the amount of water added and the rate of conversion was accelerated at higher temperatures. Interestingly, in the wet massing zone, the formation of the hemi-hydrate form was observed at a rate equivalent to the rate of depletion of the non-solvated form with no change in the level of the “apparent amorphous” form generated. The level of hemi-hydrate increased with an increase in wet massing time. The drying process had a significant effect on the proportion of each form. During tray drying, changes in drug form continued for hours. In contrast fluid bed drying appeared to lock the final proportions of drug form product attained during granulation, with comparatively small changes observed during drying. In conclusion, it was possible to simultaneously monitor the three forms in real time during wet granulation and drying using online Raman spectroscopy. The results regarding the effect of process parameters on the degree of transformation are critical for designing a robust process that ensures a consistent form in the final drug product.
The viscoelastic nature of polymeric formulations utilised in drug products imparts unique thermomechanical attributes during manufacturing and over the shelf life of the product. Nevertheless, it ...adds to the challenge of understanding the precise mechanistic behaviour of the product at the microscopic and macroscopic level during each step of the process. Current thermomechanical and rheological characterisation techniques are limited to assessing polymer performance to a single phase and are especially hindered when the polymers are undergoing thermomechanical transitions. Since pharmaceutical processing can occur at these transition conditions, this study successfully proposes a thermomechanical characterisation approach combining both mechanical and rheological data to construct a comprehensive profiling of polymeric materials spanning both glassy and rubbery phases. This approach has been used in this study to assess the mechanical and rheological behaviour of heterogenous polymer blends of hydroxypropyl cellulose (HPC) and hydroxypropyl methylcellulose (HPMC) over a shearing rate range of 0.1–100 s−1 and a temperature range of 30–200 °C. The results indicate that HPC and HPMC do not appear to interact when mixing and that their mixture exhibits the mechanistic properties of the two individual polymers in accordance with their ratio in the mixture. The ability to characterise the behaviour of the polymers and their mixtures before, throughout, and after the glassy to rubbery phase transition by application of the combined techniques provides a unique insight towards a quality-by-design approach to this and other polymer-based solid dosage forms, designed with the potential to accelerate their formulation process through obviating the need for multiple formulation trials.
The uptake of alkaline phosphate present in dissolution medium into a hydrating hydroxypropyl methylcellulose matrix tablet and that its activity was retained therein was demonstrated. This presents ...a risk to the stability of prodrugs that are substrates of this enzyme such as phosphonooxymethyl derivative prodrugs. It was found that fostemsavir, a phosphonooxymethyl derivative prodrug being developed for the treatment of HIV-1 infection, was unexpectedly resistant to hydrolysis within a hydrated HPMC matrix when subjected to drug release testing in media containing alkaline phosphatase. Studies indicated that this was not due to microenvironmental pH effects, osmolality effects or effective phosphate concentration effects associated with the presence of the prodrug. That the prodrug and not its parent could affect enzyme activity in a concentration dependent manner, and that another phosphate ester prodrug fosphenytoin did not inhibit alkaline phosphatase activity within a hydrated HPMC matrix suggested that the unexpected stability of the HIV-1 therapy prodrug may be associated with the ability of the phosphate group-containing compound itself to inhibit the enzyme at the concentrations it exists at in the hydrated dosage form and so enables the development of the compound in this type of dosage form.
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