Magnetic resonance imaging investigation of the mixing-segregation process in a pharmaceutical blender

Twin-Screw Continuous Mixing Can Produce Dry Powder Inhalation Mixtures for Pulmonary Delivery

The feasibility of twin-screw corotating extruder as a continuous process mixer to prepare dry powder inhalation (DPI) powders was investigated. Interactive mixtures of 1% micronized budesonide, 0.3% magnesium stearate and 98.7% alpha-lactose monohydrate were manufactured using a Leistritz Nano-16 extruder at various processing conditions. One set of GFM (grooved mixing) elements were included in the screw profile to provide distributive mixing of conveyed powders with the goal of resulting in a homogeneous mixture. Residence time in the twin-screw mixer was modelled to quantify mixing efficiency. Comparative powders were also prepared using either low or high-shear batch mixing to compare the effect of mixing methods on the properties of the budesonide dry powder inhalation formulation. Twin screw mixing results in homogeneous mixtures with aerosol performance comparable to that of high-shear batch mixing. Scanning electron microscopy confirmed that twin screw mixing produces particles with morphology like that of low and high-shear batch mixing. X-ray diffraction (XRD) analysis verified that there was no form change of the drug due to twin-screw processing. Statistical regression was used to probe the relationship between twin screw mixing process parameters such as screw speed and feed rate and aerosol performance. The twin screw mixing process was found to be robust, as no significant differences in aerosol performance were found for various processing parameters.

Dual targeting powder formulation of antiviral agent for customizable nasal and lung deposition profile through single intranasal administration

Unpredictable outbreaks due to respiratory viral infections emphasize the need for new drug delivery strategies to the entire respiratory tract. As viral attack is not limited to a specific anatomic region, antiviral therapy that targets both the upper and lower respiratory tract would be most effective. This study aimed to formulate tamibarotene, a retinoid derivative previously reported to display broad-spectrum antiviral activity against influenza and severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), as a novel dual particle size powder formulation that targets both the nasal cavity and the lung by a single route of intranasal administration. Spray freeze drying (SFD) and spray drying (SD) techniques were employed to prepare tamibarotene powder formulations, and cyclodextrin was used as the sole excipient to enhance drug solubility. With the employment of appropriate atomizing nozzles, particles of size above 10 μm and below 5 μm could be produced for nasal and lung deposition, respectively. The aerosol performance of the powder was evaluated using Next Generation Impactor (NGI) coupled with a glass expansion chamber and the powder was dispersed with a nasal powder device. By blending powder of two different particle sizes, a single powder formulation with dual aerosol deposition characteristic in both the nasal and pulmonary regions was produced. The aerosol deposition fractions in the nasal cavity and pulmonary region could be modulated by varying the powder mixing ratio. All dry powder formulations exhibited spherical structures, amorphous characteristics and improved dissolution profile as compared to the unformulated tamibarotene. Overall, a novel dual targeting powder formulation of tamibarotene exhibiting customizable aerosol deposition profile was developed. This exceptional formulation strategy can be adopted to deliver other antimicrobial agents to the upper and lower airways for the prevention and treatment of human respiratory infections.

Spherical Agglomerates of Lactose Reduce Segregation in Powder Blends and Improve Uniformity of Tablet Content at High Drug Loads

We report here on improved uniformity of blends of micronised active pharmaceutical ingredients (APIs) using addition of spherical agglomerates of lactose and enhanced blend flow to improve tablet content uniformity with higher API loads. Micromeritic properties and intra-particle porosity (using nano-computed X-ray tomography) of recently introduced spherical agglomerates of lactose and two standard lactose grades for the direct compression processes were compared. Powder blends of the individual lactose types and different micronised API drug loads were prepared and subjected to specific conditions that can induce API segregation. Tablet content uniformity during direct compression was related to the lactose material attributes. The distinctive micromeritic properties of the lactose types showed that spherical agglomerates of lactose had high intra-particle porosity and increased specific surface area. The stability of binary blends after intense sieving was governed by the intra-particle porosity and surface roughness of the lactose particles, which determined the retention of the model substance. Greater intra-particle porosity, powder specific surface area, and particle size of the spherical agglomerates provided greater adhesion of micronised particles, compared to granulated and spray-dried lactose. Thus the spherical agglomerates provided enhanced final blend flow and uniformity of tablet content at higher drug loads.

Application of UV dissolution imaging to pharmaceutical systems

UV-vis spectrometry is widely used in the pharmaceutical sciences for compound quantification, alone or in conjunction with separation techniques, due to most drug entities possessing a chromophore absorbing light in the range 190-800 nm. UV dissolution imaging, the scope of this review, generates spatially and temporally resolved absorbance maps by exploiting the UV absorbance of the analyte. This review aims to give an introduction to UV dissolution imaging and its use in the determination of intrinsic dissolution rates and drug release from whole dosage forms. Applications of UV imaging to non-oral formulations have started to emerge and are reviewed together with the possibility of utilizing UV imaging for physical chemical characterisation of drug substances. The benefits of imaging drug diffusion and transport processes are also discussed.

Monitoring Magnesium Stearate Blending in a V-Blender Through Passive Vibration Measurements

Process analytical technologies are implemented within the pharmaceutical manufacturing process to rectify issues associated with current sampling methods. These include inline monitoring methods such as passive vibration measurements which are non-intrusive and less costly to other methods. In the final mixing stage of the tablet manufacturing process, a lubricant is added to ensure the mixture is ejected from the tablet die cleanly. To monitor this process, an accelerometer was attached to the lid of the V-blender loaded with various particles and magnesium stearate. At a fixed fill level, the lubricant concentration and particle mass were varied to investigate the effects of changes in process parameters on the signal vibrations measured by the sensor, the coefficient of restitution, and the flowability. It was found that measured vibrations from stress waves propagated upon collisions of the particles with the V-shell respond to and can distinguish differences in particles. As well, the magnesium stearate layer around particles alters energy dissipation and subsequently the measured vibrations. A mixing endpoint of uniform distribution of magnesium stearate with primary particles can be identified from vibrations measured by an accelerometer attached to the lid of the V-blender. The flowability change was considered negligible in the particles due to their physical morphology. These findings indicate that passive vibration measurements can be a viable, non-intrusive monitoring method while providing insight into V-blender mixing behaviors as well as improving process efficiency.

An Investigation of Magnesium Stearate Mixing Performance in a V-Blender Through Passive Vibration Measurements

Prior to compression in tablet manufacturing, a lubricant is added and mixed in a V-blender to ensure the mixture is ejected from the tablet die smoothly. Mixing is conducted batch-wise and must be analyzed offline afterwards to ensure the mixture is uniform and will produce desired tablet properties, thereby a costly and time-consuming step within the manufacturing process. To improve process efficiency, inline monitoring methods using passive acoustic emissions or vibration measurements could be implemented. Methods are non-destructive, non-invasive, and have a reduced capital cost compared to traditional methods. Using an accelerometer affixed to the lid of the V-shell, magnesium stearate was added to glass beads and monitored to determine the effect of loading configuration and fill level on mixing performance and measured vibrations. Axial loading configurations performed better than radial configurations due to the limited axial dispersion from the geometry of the V-shell. Mixing was hindered at an increased fill level due to convective and axial dispersion. The optimal fill level of a V-blender was found to be 21-23% by volume. Monitoring magnesium stearate mixing using passive vibration measurements is a non-intrusive and potentially inline method that could significantly improve pharmaceutical process efficiency.

Methods to Assess Mixing of Pharmaceutical Powders

The pharmaceutical manufacturing process consists of several steps, each of which must be monitored and controlled to ensure quality standards are met. The level of blending has an impact on the final product quality; therefore, it is important to be able to monitor blending progress and identify an end-point. Currently, the pharmaceutical industry assesses blend content and uniformity through the extraction of samples using thief probes followed by analytical methods, such as spectroscopy, to determine the sample composition. The development of process analytical technologies (PAT) can improve product monitoring with the aim of increasing efficiency, product quality and consistency, and creating a better understanding of the manufacturing process. Ideally, these are inline methods to remove issues related to extractive sampling and allow direct monitoring of the system using various sensors. Many technologies have been investigated, including spectroscopic techniques such as near-infrared spectroscopy, velocimetric techniques that may use tracers, tomographic techniques, and acoustic emissions monitoring. While some techniques have demonstrated potential, many have significant disadvantages including the need for equipment modification, specific requirements of the material, expensive equipment, extensive analysis, the location of the probes may be critical and/or invasive, and lastly, the technique may only be applicable to the development phase. Both the advantages and disadvantages of the technologies should be considered in application to a specific system.

Magnetic resonance imaging of granular materials

Magnetic Resonance Imaging (MRI) has become one of the most important tools to screen humans in medicine; virtually every modern hospital is equipped with a Nuclear Magnetic Resonance (NMR) tomograph. The potential of NMR in 3D imaging tasks is by far greater, but there is only "a handful" of MRI studies of particulate matter. The method is expensive, time-consuming, and requires a deep understanding of pulse sequences, signal acquisition, and processing. We give a short introduction into the physical principles of this imaging technique, describe its advantages and limitations for the screening of granular matter, and present a number of examples of different application purposes, from the exploration of granular packing, via the detection of flow and particle diffusion, to real dynamic measurements. Probably, X-ray computed tomography is preferable in most applications, but fast imaging of single slices with modern MRI techniques is unmatched, and the additional opportunity to retrieve spatially resolved flow and diffusion profiles without particle tracking is a unique feature.

Lubricant sensitivity in function of paddle movement in the forced feeder of a high-speed tablet press

CONTEXT

The negative impact of magnesium stearate (MgSt) on the hardness of tablets is a well-known phenomenon, but the influence of paddle movement in the forced feeder on the lubricant effect during tablet compression is often neglected.

OBJECTIVE

The purpose of this research was to investigate the influence of paddle speed in the forced feeder on tablet tensile strength (TS).

MATERIALS AND METHODS

Mixtures of microcrystalline cellulose (MCC) and MgSt (0.5%) were blended using different methods (low & high shear). After blending, the formulations were compressed into tablets. All parameters of the tableting cycle were kept constant except the speed of the paddles in the forced feeder.

RESULTS AND DISCUSSION

The blending technique affected the sensitivity of the formulation to the paddle speed. The TS of pure MCC tablets did not change in function of paddle speed, while tablets prepared by low shear mixing became softer at higher paddle speed. The TS of tablets manufactured using the high-shear mixed blend was low and did not vary in function of paddle speed, suggesting that overlubrication already occurred during the initial blending step. Furthermore, analysis of the machine parameters allowed evaluation of the influence of the paddles on the flowability, initial packing, and compactability of the powder mixtures.

CONCLUSION

The results elucidated that during manufacturing of tablets using MgSt-containing blends care should not only be taken during the blending step prior to tableting, but also during the tableting process itself, as paddle speed can affect tablet TS, a critical quality attribute.

Segregation in horizontal rotating cylinders using magnetic resonance imaging

The dynamics of granular materials, particularly radial and axial segregation in horizontal rotating cylinders containing large and small particles, is studied by Magnetic Resonance Imaging (MRI). Stationary three-dimensional (3D) images and real-time two-dimensional (2D) structural images showing radial segregation, band formation, and band merging are reported. Quantitative local particle concentrations are measured in a noninvasive manner from the different magnetic resonance responses of the seeds throughout segregation. Data are acquired with sufficiently high temporal (300 ms for 2D images) and spatial resolutions (0.94 mm cubic voxels), to give insights into the underlying mechanisms of both radial and axial segregation. In particular, the increasing rate of the local particle concentration during radial segregation is quantified. Particle migration is observed in the bulk material of the 75% and 82% full cylinders during both radial and axial segregation, showing that this region beneath the avalanche layer does not behave as a solid body. We also provide direct experimental evidence to support recent numerical simulations of band merging.

Magnetic resonance imaging studies on gadonanotube-reinforced biodegradable polymer nanocomposites

We report about the in vitro cytotoxicity and MRI studies of Gd(3+)ions-doped ultra-short single-walled carbon nanotube (gadonanotubes), gadonanotubes- reinforced poly(lactic-co-glycolic acid) (PLGA) polymer nanocomposites and in vivo small animal MRI studies using the gadonanotubes. These studies were performed to explore the suitability of gadonanotubes-reinforced PLGA polymer nanocomposite as a model scaffold for noninvasive magnetic resonance imaging (MRI) to evaluate nanotube release during the degradation process of the scaffold and their biodistribution upon release from the polymer matrix in vivo. The gadonanotubes at 1-100 ppm and the gadonanotubes/PLGA nanocomposites (2 wt % gadonanotubes) did not show any cytotoxicity in vitro as demonstrated using the LIVE/DEAD viability assay. For the first time, r(2) relaxivity measurements were obtained for the superparamagnetic gadonanotubes. In vitro 7T MRI of the superparamagnetic gadonanotubes ([Gd] = 0.15 mM) suspended in a biocompatible 1% Pluronic F127 solution, gave a r(2) value of 578 mM(-1) s(-1). Upon subcutaneous injection of the gadonanotubes suspension into the dorsal region of rats, the high r(2) value translated into excellent and prolonged negative contrast enhancement of in vivo T(2)weighted proton MRI images. The in vitro characterization of the nanocomposite discs and their degradation process by MRI, showed strong influence of the gadonanotube on water proton relaxations. These results indicate that the gadonanotubes/PLGA nanocomposites are suitable for further in vivo studies to track by MRI the biodegradation release and biodistribution of gadonanotubes.

Highly reproducible powder aerosolisation for lung delivery using powder-specific electromechanical vibration

Dry powder inhalers (DPIs) have been in use since the 1970s, but it is only within the past few years that their use has constituted > approximately 10% of the inhaler units sold worldwide. Similarly, active DPIs have been in development for more than a decade, but no active device has yet been approved. Oriel is developing an active DPI technology that uses a very simple physical design coupled with a complex knowledge of powder flow and dispersion characterisation. The DPI uses electromechanical vibration with frequencies determined through the analysis of powder flow properties. Results so far have shown highly reproducible, efficient performance. The technology lends itself to both unit-dose and multidose platforms in a targeted cost-effective DPI.

Examination of homogeneity with X-ray beams

The effects of blending time and rotation speed on the homogeneity of powder blends were examined. The concentrations of the samples were measured with an energy-dispersive X-ray fluorescence analyser, and control measurements were made with a UV spectrophotometer. The paired sample t-test showed that, for a large majority of the samples for which measurements were made to determine the concentrations, there was no essential difference. It may be stated, in accordance with the fitted equation, that the rotation speed and the square of the blending time exert significant effects on the distribution of the active ingredient. The energy-dispersive X-ray fluorescence analyser can be applied well for direct determination of the homogeneity of certain powder blends.

In-line monitoring of a pharmaceutical blending process using FT-Raman spectroscopy

FT-Raman spectroscopy (in combination with a fibre optic probe) was evaluated as an in-line tool to monitor a blending process of diltiazem hydrochloride pellets and paraffinic wax beads. The mean square of differences (MSD) between two consecutive spectra was used to identify the time required to obtain a homogeneous mixture. A traditional end-sampling thief probe was used to collect samples, followed by HPLC analysis to verify the Raman data. Large variations were seen in the FT-Raman spectra logged during the initial minutes of the blending process using a binary mixture (ratio: 50/50, w/w) of diltiazem pellets and paraffinic wax beads (particle size: 800-1200 microm). The MSD-profiles showed that a homogeneous mixture was obtained after about 15 min blending. HPLC analysis confirmed these observations. The Raman data showed that the mixing kinetics depended on the particle size of the material and on the mixing speed. The results of this study proved that FT-Raman spectroscopy can be successfully implemented as an in-line monitoring tool for blending processes.