Effect of particle size on the dispersion behavior of magnesium stearate blended with microcrystalline cellulose

The majority of tablets manufactured contain lubricants to reduce friction during ejection. However, especially for plastically deforming materials, e.g., microcrystalline cellulose (MCC), the internal addition of lubricants is known to reduce tablet tensile strength. This reduction is caused by the surface coverage by lubricant particles, the extent of which depends on both process and formulation parameters. Previously published models to predict the lubrication effect on mechanical strength do not account for changes in the excipient particle size. In this study, the impact of both lubricant concentration and mixing time on the tensile strength of tablets consisting of three different grades of MCC and four grades of magnesium stearate (MgSt) was evaluated. By taking into account the particle size of the applied excipients, a unifying relationship between the theoretically estimated surface coverage and compactibility reduction was identified. Evaluating the dispersion kinetics of MgSt as a function of time reveals a substantial impact of the initial surface coverage on the dispersion rate, while the minimal tensile strength was found to be comparable for the majority of formulations. In summary, the presented work extends the knowledge of lubricant dispersion and facilitates the reduction of necessary experiments during the development of new tablet formulations.

Highly protein-loaded melt extrudates produced by small-scale ram and twin-screw extrusion - evaluation of extrusion process design on protein stability by experimental and numerical approaches

Understanding of generation, extent and location of thermomechanical stress in small-scale (< 3 g) ram and twin-screw melt-extrusion is crucial for mechanistic correlations to the stability of protein particles (lysozyme and BSA) in PEG-matrices. The aim of the study was to apply and correlate experimental and numerical approaches (1D and 3D) for the evaluation of extrusion process design on protein stability. The simulation of thermomechanical stress during extrusion raised the expectation of protein degradation and protein particle grinding during extrusion, especially when TSE was used. This was confirmed by experimental data on protein stability. Ram extrusion had the lowest impact on protein unfolding temperatures, whereas TSE showed significantly reduced unfolding temperatures, especially in combination with kneading elements containing screws. In TSE, the mechanical stress in the screws always exceeded the shear stress in the die, while mechanical stress within ram extrusion was generated in the die, only. As both extruder designs revealed homogeneously distributed protein particles over the cross section of the extrudates for all protein-loads (20-60%), the dispersive power of TSE revealed not to be decisive. Consequently, the ram extruder would be favored for the production of stable protein-loaded extrudates in small scale.

Investigation of Dispersion Kinetics of Particulate Lubricants and their Effect on the Mechanical Strength of MCC Tablets

INTRODUCTION

Tablets are commonly produced by internally adding particulate lubricants, which are known to possibly lower the mechanical strength of tablets. This reduction is caused by the coverage of matrix forming components by lubricant particles, resulting in decreased interparticulate interactions. The known incompatibilities with some active compounds of the predominantly used lubricant, magnesium stearate, call for the in-depth characterization of alternative lubricants.

PURPOSE

Investigation of the dispersion behavior of five commonly applied pharmaceutical lubricants by mathematically modeling the dispersion kinetics for short and extended mixing times.

METHODS

The dispersion behavior of five different pharmaceutical lubricants were examined by systematically varying lubricant concentration and mixing time of binary formulations and evaluating the kinetic of tensile strength reduction by theoretically estimating the surface coverage based on particle sizes.

RESULTS

For short mixing times, a unifying relationship between compactibility reduction and theoretical surface coverage was identified. Subsequently, for extended mixing times, distinct differences in the shear strength and dispersion kinetics of the investigated lubricants were found.

CONCLUSIONS

The lubricant particle size controls the tensile strength reduction if short mixing times are applied. For extended mixing times, the investigated lubricants can be divided into two groups in terms of dispersion kinetics. Possible underlying reasons are discussed in detail in order to enhance the general understanding of lubricant dispersions in tablet formulations.

Quantification and modeling of macroparticle-induced mechanical stress for varying shake flask cultivation conditions

In biotechnological processes, filamentous microorganisms are known for their broad product spectrum and complex cellular morphology. Product formation and cellular morphology are often closely linked, requiring a well-defined level of mechanical stress to achieve high product concentrations. Macroparticles were added to shake flask cultures of the filamentous actinomycete Lentzea aerocolonigenes to find these optimal cultivation conditions. However, there is currently no model concept for the dependence of the strength and frequency of the bead-induced stress on the process parameters. Therefore, shake flask simulations were performed for combinations of bead size, bead concentration, bead density and shaking frequency. Contact analysis showed that the highest shear stresses were caused by bead-bottom contacts. Based on this, a newly generated characteristic parameter, the stress area ratio (SAR), was defined, which relates the bead wall shear and normal stresses to the total shear area. Comparison of the SAR with previous cultivation results revealed an optimum pattern for product concentration and mean product-to-biomass related yield coefficient. Thus, this model is a suitable tool for future optimization, comparison and scaling up of shear-sensitive microorganism cultivation. Finally, the simulation results were validated using high-speed recordings of the bead motion on the bottom of the shake flask.

Temperature influence on the compression and breakage behaviour of yeast cells

Industrial biotechnology uses microbial cells to produce a wide range of products. While the genetic and molecular properties of these organisms are well understood, less is known about their mechanical properties. Previous work has established a test procedure for single yeast cells using a nanoindentation instrument equipped with a flat-punch probe, which allows single cells (Saccharomyces cerevisiae) to be compressed between two parallel surfaces. The resulting force-displacement curves clearly showed the bursting of the cells and were used to determine characteristics such as burst force and burst energy. Other studies have investigated the influence of growth conditions and measurement conditions on the mechanical characteristics. The recent study examined the mechanical characteristics according to the temperature during compression. Temperature from 0°C to 25°C has no significant effect on the micromechanical properties. Increasing the temperature up to 35°C causes a reduction in the strength of the cells. At even higher temperatures, up to 50°C, the burst force and burst energy increase significantly. A deformation geometry model was used to calculate the cell wall tensile strength as a function of temperature. The results of these studies may facilitate the identification of efficient conditions for cell disruption and product recovery in downstream biotechnological processes.

Process and formulation parameters influencing the survival of Saccharomyces cerevisiae during spray drying and tableting

Probiotic microorganisms provide health benefits to the patient when administered in a viable form and in sufficient doses. To ensure this, dry dosage forms are preferred, with tablets in particular being favored due to several advantages. However, the microorganisms must first be dried as gently as possible. Here, the model organism Saccharomyces cerevisiae was dried by spray drying. Various additives were tested for their ability to improve yeast cell survival during drying. In addition, the influence of various process parameters such as inlet temperature, outlet temperature, spray rate, spray pressure and nozzle diameter was investigated. It was possible to dry the yeast cells in such a way that a substantial proportion of living microorganisms was recovered after reconstitution. Systematic variation of formulation and process parameters showed that the use of protective additives is essential and that the outlet temperature determines the survival rate. The subsequent compression of the spray-dried yeast reduced viability and survival could hardly be improved by the addition of excipients, but the tabletability of spray-dried yeast protectant particles was quite good. For the first time, loss of viability during compaction of spray-dried microorganisms was correlated with the specific densification, allowing a deeper understanding of the mechanism of cell inactivation during tableting.

Influence of compression kinetics during tableting of fluidized bed-granulated microorganisms on microbiological and physical-mechanical tablet properties

As tablets are convenient to administer to patients, ensure safe dosing and allow cost-effective production on a large scale, they are the favored dosage form for numerous active pharmaceutical ingredients but also for the administration of viable probiotic microorganisms. Granules with viable yeast cells (Saccharomyces cerevisiae) formed by fluidized bed granulation with dicalcium phosphate (DCP), lactose (LAC) or microcrystalline cellulose (MCC) as carrier materials were tableted using a compaction simulator. Besides the compression stress, the compression speed was systematically studied by varying consolidation time and dwell time. The microbial survival as well as physical properties of the tablets, e.g., porosity and tensile strength, were determined. Higher compression stresses result in lower porosities. While on the one hand this has a detrimental effect on microbial survival (due to increased pressure and shear stress during particle rearrangement / densification), on the other hand it results in higher tensile strengths. At the same compression stress, a prolonged dwell time resulted in lower porosity and thus in lower survival rates but higher tensile strength. Against that, consolidation time showed no significant influence on the considered tablet quality attributes. Since changes of the tensile strength related survival rate were negligible (due to opposite but balancing dependence on porosity), high production speeds could be used for tableting of these granules without additional loss of viability, as long as tablets with the same tensile strength are produced.

Amyloid-like aggregation of recombinant β-lactoglobulin at pH 3.5 and 7.0: Is disulfide bond removal the key to fibrillation?

Functional nanofibrils from globular proteins are usually formed by heating for several hours at pH 2.0, which induces acidic hydrolysis and consecutive self-association. The functional properties of these micro-metre-long anisotropic structures are promising for biodegradable biomaterials and food applications, but their stability at pH > 2.0 is low. The results presented here show that modified β-lactoglobulin can also form nanofibrils by heating at neutral pH without prior acidic hydrolysis; the key is removing covalent disulfide bonds. The aggregation behaviour of various recombinant β-lactoglobulin variants was systemically studied at pH 3.5 and 7.0. The suppression of intra- and intermolecular disulfide bonds by eliminating one to three out of the five cysteines makes the non-covalent interactions more prevalent and allow for structural rearrangement. This stimulated the linear growth of worm-like aggregates. Full elimination of all five cysteines led to the transformation of worm-like aggregates into actual fibril structures (several hundreds of nanometres long) at pH 7.0. This understanding of the role of cysteine in protein-protein interactions will help to identify proteins and protein modifications to form functional aggregates at neutral pH.

Tableting of Fluidized Bed Granules Containing Living Microorganisms

Tablets are the favored dosage form for numerous active pharmaceutical ingredients, among others because they are easy to take, ensure safe dosing and allow cost-effective production on a large scale. This dosage form is also frequently chosen for the administration of viable probiotic microorganisms. Saccharomyces cerevisiae cells granulated in a fluidized bed process, with dicalcium phosphate (DCP), lactose (LAC) and microcrystalline cellulose (MCC) as carrier materials, were tableted using a compaction simulator, varying the compression stress. The tablets were analyzed regarding physical properties, e.g., porosity and tensile strength, as well as microbial survival. Carrier material and compression stress showed a significant influence on survival rate and physical tablet properties. The dependencies were related to material specific deformation characteristics and linked to mechanistic approaches to explain the different sensitivities.

Enhanced multi-component model to consider the lubricant effect on compressibility and compactibility

Modeling of structural and mechanical tablet properties consisting of multiple components, based on a minimum of experimental data is of high interest, in order to minimize time- and cost-intensive experimental trials in the development of new tablet formulations. The majority of commonly available models use the compressibility and compactibility of constituent components and establish mixing rules between those components, in order to predict the tablet properties of formulations containing multiple components. However, their applicability is limited to single materials, which form intact tablets (e.g. lactose, cellulose) and therefore, they cannot be applied for lubricants. Lubricants are required in the majority of industrial tablet formulations and usually influence the mechanical strength of tablets. This study combines the multi-component compaction model of Reynolds et al. (2017) with a recently published lubrication model (Puckhaber et al. 2020) to describe the impact of multiple components on a formulation consisting of two diluents and a lubricant. By that, this model combination displays a meaningful extension of existing compaction models and allows the systematic prediction of properties of lubricated multi-component tablets.

The Effect of Particle Shape on the Compaction of Realistic Non-Spherical Particles—A Multi-Contact DEM Study

The purpose of this study was to investigate the deformation behavior of non-spherical particles during high-load compaction using the multi-contact discrete element method (MC-DEM). To account for non-spherical particles, the bonded multi-sphere method (BMS), which incorporates intragranular bonds between particles, and the conventional multi-sphere (CMS), where overlaps between particles are allowed to form a rigid body, were used. Several test cases were performed to justify the conclusions of this study. The bonded multi-sphere method was first employed to study the compression of a single rubber sphere. This method’s ability to naturally handle large elastic deformations is demonstrated by its agreement with experimental data. This result was validated further through detailed finite element simulations (multiple particle finite element method (MPFEM)). Furthermore, the conventional multi-sphere (CMS) approach, in which overlaps between particles are allowed to form a rigid body, was used for the same objective, and revealed the limitations of this method in successfully capturing the compression behavior of a single rubber sphere. Finally, the uniaxial compaction of a microcrystalline cellulose-grade material, Avicel® PH 200 (FMC BioPolymer, Philadelphia, PA, USA), subjected to high confining conditions was studied using the BMS method. A series of simulation results was obtained with realistic non-spherical particles and compared with the experimental data. For a system composed of non-spherical particles, the multi-contact DEM showed very good agreement with experimental data.

Morphology engineering for novel antibiotics: Effect of glass microparticles and soy lecithin on rebeccamycin production and cellular morphology of filamentous actinomycete Lentzea aerocolonigenes

Lentzea aerocolonigenes, as an actinomycete, is a natural producer of the antibiotic and antitumoral drug rebeccamycin. Due to the filamentous cellular morphology handling in cultivations is challenging; therefore, morphology engineering techniques are mandatory to enhance productivity. One promising approach described in the literature is the addition of mineral particles in the micrometer range to precisely adjust cellular morphology and the corresponding product synthesis (microparticle-enhanced cultivation, MPEC). Glass microparticles are introduced in this study as a novel supplementation type for bioprocess intensification in filamentous organisms. Several investigations were conducted to screen for an optimal particle setup, including particle size and concentration regarding their impact and effects on enhanced productivity, microparticle incorporation behavior into the biopellets, the viability of pellets, and morphological changes. Glass microparticles (10 g·L^-1) with a median diameter of 7.9 µm, for instance, induced an up to fourfold increase in product synthesis accompanied by overall enhanced viability of biomass. Furthermore, structural elucidations showed that biopellets isolated from MPEC tend to have lower hyphal density than unsupplemented control pellets. In this context, oxygen microprofiling was conducted to better understand how internal structural changes interwind with oxygen supply into the pellets. Here, the resulting oxygen profiles are of a contradictive trend of steeper oxygen consumption with increasing glass microparticle supplementation. Eventually, MPEC was combined with another promising cultivation strategy, the supplementation of soy lecithin (7.5 g·L^-1), to further increase the cultivation performance. A combination of both techniques in an optimized setup resulted in a rebeccamycin concentration of 213 mg·L^-1 after 10 days of cultivation, the highest value published so far for microparticle-supplemented shake flask cultivations of L. aerocolonigenes.

Geotechnical and Shear Behavior of Novel Lunar Regolith Simulants TUBS-M, TUBS-T, and TUBS-I

The return to the Moon is an important short-term goal of NASA and other international space agencies. To minimize mission risks, technologies, such as rovers or regolith processing systems, must be developed and tested on Earth using lunar regolith simulants that closely resemble the properties of real lunar soil. So far, no singular lunar simulant can cover the multitude of use cases that lunar regolith involves, and most available materials are poorly characterized. To overcome this major gap, a unique modular system for flexible adaptable novel lunar regolith simulants was developed and chemically characterized in earlier works. To supplement this, the present study provides comprehensive investigations regarding geotechnical properties of the three base regolith simulant systems: TUBS-M, TUBS-T, and TUBS-I. To evaluate the engineering and flow properties of these heterogeneous materials under various conditions, shear tests, particle size analyses, scanning electron microscope observations, and density investigations were conducted. It was shown that small grains <25 µm (lunar dust) are highly compressive and cohesive even at low external stress. They are particularly important as a large amount of fine dust is present in lunar regolith and simulants (x50 = 76.7 to 96.0 µm). Further, ring shear and densification tests revealed correlations with damage mechanisms caused by local stress peaks for grains in the mm range. In addition, an explanation for the occurrence of considerable differences in the literature-based data for particle sizes was established by comparing various measurement procedures. The present study shows detailed geotechnical investigations of novel lunar regolith simulants, which can be used for the development of equipment for future lunar exploration missions and in situ resource utilization under realistic conditions. The results also provide evidence about possible correlations and causes of known soil-induced mission risks that so far have mostly been described phenomenologically.

Enabling Long-Cycling Life of Si-on-Graphite Composite Anodes via Fabrication of a Multifunctional Polymeric Artificial Solid-Electrolyte Interphase Protective Layer

The energy density of lithium-ion batteries (LIBs) can be meaningfully increased by utilizing Si-on-graphite composites (Si@Gr) as anode materials, because of several advantages, including higher specific capacity and low cost. However, long cycling stability is a key challenge for commercializing these composites. In this study, to solve this issue, we have developed a multifunctional polymeric artificial solid-electrolyte interphase (A-SEI) protective layer on carbon-coated Si@Gr anode particles (making Si@Gr/C-SCS) to prolong the cycling stability in LIBs. The coating is made of sulfonated chitosan (SCS) that is crosslinked with glutaraldehyde promoting good ionic conduction together with sufficient mechanical strength of the A-SEI. The focused ion beam-scanning electron microscopy and high-resolution transmission electron microscopy images show that the SCS is uniformly coated on the composite particles with thickness in nanometer. The anodes are investigated in Li metal cells Si@Gr/C-SCS||Li metal) and lithium-ion full-cells (LiNi_0.6Co_0.2Mn_0.2O₂ (NCM-622)||Si@Gr/C-SCS) to understand the material/electrode intrinsic degradation as well as the impact of the polymer coating on active lithium losses because of the continuous SEI (re)formation. The anode composites exhibit a high capacity reaching over 600 mAh g^-1, and even without electrolyte optimization, the Si@Gr/C-SCS illustrates a superior long cycle life performance of up to 1000 cycles (over 67% capacity retention). The excellent long-term cycling stability of the anodes was attributed to the SCS polymer coating acting as the A-SEI. The simple polymer coating process is highly interesting in guiding the preparation of long-cycle-life electrode materials of high-energy LIB cells.

Influence of the drug deformation behaviour on the predictability of compressibility and compactibility of binary mixtures

Various studies investigate the predictability of the compressibility and compactibility of tablet formulations based on the behaviour of the pure materials. However, these studies are limited to a few materials so far probably because of the complexity of the powder compaction process. One approach preventing the excessive increase in complexity is the extension of the investigations from pure materials to binary powder mixtures. The focus of this study is on the predictability of the compressibility and compactibility of binary mixtures consisting of an active pharmaceutical ingredient (API) and the excipient microcrystalline cellulose. Three APIs with markedly different deformation behaviour were used. The API concentration and type are systematically varied. For all three material combinations it is found that the in-die compressibility of the binary mixtures can be precisely predicted based on the characteristic compression parameters of the raw materials using the extended in-die compression function in combination with a volume-based linear mixing rule. Since the tablet porosity (out-of-die) also follows a linear mixing rule, the predictability can be further extended using the method of Katz et al. In contrast, the influence of the API concentration on compactibility or rather on tablet tensile strength is non-linear and strongly dependent on the deformation behaviour of the API, making the predictability more difficult. Neither the approach of Reynolds et al. nor this of Kuentz and Leuenberger are able to predict the compactibility when clear deviations from a linear mixing rule appear.

Evaluation of the Formulation Parameter-Dependent Redispersibility of API Nanoparticles from Fluid Bed Granules

The production of nanosuspensions of poorly soluble active pharmaceutical ingredients (API) is a popular technique to counteract challenges regarding bioavailability of such active substances. A subsequent drying of the nanosuspensions is advantageous to improve the long-term stability and the further processing into solid oral dosage forms. However, associated drying operations are critical, especially with regard to nanoparticle growth, loss in redispersibility and associated compromised bioavailability. This work extends a previous study regarding the applicability of an API (itraconazole) nanosuspension as a granulation liquid in a fluidized bed process with focus on the influence of applied formulation parameters on the structure of obtained nanoparticle-loaded granules and their nanoparticle redispersibility. Generally, a higher dissolution rate of the carrier material (glass beads, lactose, mannitol or sucrose) and a higher content of a matrix former/hydrophilic polymer (PVP/VA or HPMC) in the granulation liquid resulted in the formation of coarser and more porous granules with improved nanoparticle redispersibility. HPMC was found to have advantages as a polymer compared with PVP/VA. In general, a better redispersibility of the nanoparticles from the granules could be associated with better dispersion of the API nanoparticles at the surface of the granules as deduced from the thickness of nanoparticle-loaded layers around the granules. The layer thickness on granules was assessed by means of confocal Raman microscopy. Finally, the dispersion of the nanoparticles in the granule layers was exemplarily described by calculation of theoretical mean nanoparticle distances in the granule layers and was correlated with data obtained from redispersibility studies.

Prediction of the impact of lubrication on tablet compactibility

The tableting of most pharmaceutical formulations requires the addition of lubricants to reduce ejection forces, prevent tooling damage and tablet defects. The internal addition of lubricants is known to reduce tablet tensile strength, especially of mainly plastically deforming materials. To date, available models show only limited quantitative predictive accuracy for the influence of lubricant concentration on the mechanical strength of tablets. This study aims to fill this gap and present a model based on the Ryshkewitch-Duckworth equation that can estimate the compactibility profiles of lubricated formulations. Binary mixtures of different diluents (microcrystalline cellulose and lactose) were prepared with common lubricants (magnesium stearate and sodium stearyl fumarate) and subsequently tableted. The resulting compactibility profiles were fitted using the Ryshkewitch-Duckworth equation and the derived fit parameters (k_b and σ₀) were correlated with the lubricant concentration. Subsequently, an empirical model was established which requires a minimum of experimental data and is able to predict the tensile strength of lubricated diluent tablets. Consequently, the developed empirical model is an interesting and valuable addition to the existing multi-component compacting models available and offers the opportunity to accelerate experimentation in the development of new tablet formulations.

Effects and interactions of metal oxides in microparticle-enhanced cultivation of filamentous microorganisms

Filamentous microorganisms are used as molecular factories in industrial biotechnology. In 2007, a new approach to improve productivity in submerged cultivation was introduced: microparticle-enhanced cultivation (MPEC). Since then, numerous studies have investigated the influence of microparticles on the cultivation. Most studies considered MPEC a morphology engineering approach, in which altered morphology results in increased productivity. But sometimes similar morphological changes lead to decreased productivity, suggesting that this hypothesis is not a sufficient explanation for the effects of microparticles. Effects of surface chemistry on particles were paid little attention, as particles were often considered chemically-inert and bioinert. However, metal oxide particles strongly interact with their environment. This review links morphological, physical, and chemical properties of microparticles with effects on culture broth, filamentous morphology, and molecular biology. More precisely, surface chemistry effects of metal oxide particles lead to ion leaching, adsorption of enzymes, and generation of reactive oxygen species. Therefore, microparticles interfere with gene regulation, metabolism, and activity of enzymes. To enhance the understanding of microparticle-based morphology engineering, further interactions between particles and cells are elaborated. The presented description of phenomena occurring in MPEC eases the targeted choice of microparticles, and thus, contributes to improving the productivity of microbial cultivation technology.

Tablet formulation development focusing on the functional behaviour of water uptake and swelling

The functional behaviour of tablets is strongly influenced by their manufacturing process and the choice of excipients. Water uptake and swelling are prerequisites for tablet disintegration, dispersion and hence active pharmaceutical ingredient (API) dissolution. High proportions of polymeric excipients in tablets, which are typically used as API carriers in amorphous solid dispersions (ASDs), may be challenging due to the formation of a gelling polymer network (GPN). In this study, systematic investigations into the formulation development of tablets containing polymeric and other excipients are performed by water uptake and swelling analysis. The impact of tablet composition and porosity as well as pH of the test medium are investigated. The pH affects the analysis results for Eudragit L100-55 and Eudragit EPO. HPMC and Kollidon VA64 inhibit water uptake and swelling of tablets due to the formation of a GPN. High tablet porosity, coarse particle size of the polymer and the addition of fillers and disintegrants can reduce the negative impact of a GPN on tablet performance. The application of lubricants slows down the analysed processes. Water uptake and swelling data are fitted to an empirical model obtaining four characteristic parameters to facilitate the simple quantitative assessment of varying tablet formulations and structural properties.

Nanoparticle Additivation Effects on Laser Powder Bed Fusion of Metals and Polymers-A Theoretical Concept for an Inter-Laboratory Study Design All Along the Process Chain, Including Research Data Management

In recent years, the application field of laser powder bed fusion of metals and polymers extends through an increasing variability of powder compositions in the market. New powder formulations such as nanoparticle (NP) additivated powder feedstocks are available today. Interestingly, they behave differently along with the entire laser powder bed fusion (PBF-LB) process chain, from flowability over absorbance and microstructure formation to processability and final part properties. Recent studies show that supporting NPs on metal and polymer powder feedstocks enhances processability, avoids crack formation, refines grain size, increases functionality, and improves as-built part properties. Although several inter-laboratory studies (ILSs) on metal and polymer PBF-LB exist, they mainly focus on mechanical properties and primarily ignore nano-additivated feedstocks or standardized assessment of powder feedstock properties. However, those studies must obtain reliable data to validate each property metric’s repeatability and reproducibility limits related to the PBF-LB process chain. We herein propose the design of a large-scale ILS to quantify the effect of nanoparticle additivation on powder characteristics, process behavior, microstructure, and part properties in PBF-LB. Besides the work and sample flow to organize the ILS, the test methods to measure the NP-additivated metal and polymer powder feedstock properties and resulting part properties are defined. A research data management (RDM) plan is designed to extract scientific results from the vast amount of material, process, and part data. The RDM focuses not only on the repeatability and reproducibility of a metric but also on the FAIR principle to include findable, accessible, interoperable, and reusable data/meta-data in additive manufacturing. The proposed ILS design gives access to principal component analysis (PCA) to compute the correlations between the material–process–microstructure–part properties.

Macroparticle-enhanced cultivation of Lentzea aerocolonigenes: Variation of mechanical stress and combination with lecithin supplementation for a significantly increased rebeccamycin production

The actinomycete Lentzea aerocolonigenes produces the antitumor antibiotic rebeccamycin. In previous studies the rebeccamycin production was significantly increased by the addition of glass beads during cultivation in different diameters between 0.5 and 2 mm and the induced mechanical stress by the glass beads was proposed to be responsible for the increased production. Thus, this study was conducted to be a systematic investigation of different parameters for macroparticle addition, such as bead diameter, concentration, and density (glass and ceramic) as well as shaking frequency, for a better understanding of the particle-induced stress on L. aerocolonigenes. The induced stress for optimal rebeccamycin production can be estimated by a combination of stress energy and stress frequency. In addition, the macroparticle-enhanced cultivation of L. aerocolonigenes was combined with soy lecithin addition to further increase the rebeccamycin concentration. With 100 g L^-1 glass beads in a diameter of 969 µm and 5 g L^-1 soy lecithin a concentration of 388 mg L^-1 rebeccamycin was reached after 10 days of cultivation, which corresponds to the highest rebeccamycin concentrations achieved in shake flask cultivations of L. aerocolonigenes stated in literature so far.

The Effect of Binder Loading on the Pore Size of 3D Printed PMMA

Binder jetting is known to produce porous objects by depositing the binder selectively layer by layer on a powder bed. In this study, the pore size of printed parts and the correlating mechanical properties are investigated on a commercially available PMMA powder binder system. Pore sizes are measured via capillary flow porometry and mechanical properties via tensile tests. Porometry indicates that the pore size stays at a constant level of 22 µm at 5 to 10 wt% binder loading before decreasing to 6 µm at loadings of 30 wt% or higher. The results were compared with the mechanical testing and related to the agglomerate strength model of Rumpf. The highlights of the article are the application of a binder jetted part as a filter and the identification of a close relationship between porosity and mechanical strength, similar to phenomena in agglomeration science.

The influence of particle size on the application of compression and compaction models for tableting

The physical characteristics of raw materials determine powder compression and compaction performance as relevant in pharmaceutical processes. For instance, the influence of initial particle size on powder compression and the resulting strength of specimen are highly complex and are still not sufficiently understood. Existing studies are often limited to materials with well-defined deformation behaviour, such as purely brittle or ductile. However, the deformation behaviour of active pharmaceutical ingredients (APIs) is often more complex. In this study, the influence of initial particle size on powder compressibility and compactibility is systematically characterized by consideration of in-die compressibility, specific energies, quick elastic recovery, tablet porosity and, tensile strength for the binder microcrystalline cellulose and three APIs. The decrease of particle size leads to an increase of the resistance against compression by trend and probably to a different contribution of the acting deformation mechanisms. The compactibility is increased with decreasing particle size because of the increasing number of bonds in a cross-sectional area of the tablet, as found by the application of the model of Rumpf. Furthermore, it is found that the model of Rumpf combined with the JKR model provides a meaningful property function to estimate tablet tensile strength.

Morphological and physiological characterization of filamentous Lentzea aerocolonigenes: Comparison of biopellets by microscopy and flow cytometry

Cell morphology of filamentous microorganisms is highly interesting during cultivations as it is often linked to productivity and can be influenced by process conditions. Hence, the characterization of cell morphology is of major importance to improve the understanding of industrial processes with filamentous microorganisms. For this purpose, reliable and robust methods are necessary. In this study, pellet morphology and physiology of the rebeccamycin producing filamentous actinomycete Lentzea aerocolonigenes were investigated by microscopy and flow cytometry. Both methods were compared regarding their applicability. To achieve different morphologies, a cultivation with glass bead addition (Ø = 969 μm, 100 g L-1) was compared to an unsupplemented cultivation. This led to two different macro-morphologies. Furthermore, glass bead addition increased rebeccamycin titers after 10 days of cultivation (95 mg L-1 with glass beads, 38 mg L-1 without glass beads). Macro-morphology and viability were investigated through microscopy and flow cytometry. For viability assessment fluorescent staining was used additionally. Smaller, more regular pellets were found for glass bead addition. Pellet diameters resulting from microscopy followed by image analysis were 172 μm without and 106 μm with glass beads, diameters from flow cytometry were 170 and 100 μm, respectively. These results show excellent agreement of both methods, each considering several thousand pellets. Furthermore, the pellet viability obtained from both methods suggested an enhanced metabolic activity in glass bead treated pellets during the exponential production phase. However, total viability values differ for flow cytometry (0.32 without and 0.41 with glass beads) and confocal laser scanning microscopy of single stained pellet slices (life ratio in production phase of 0.10 without and 0.22 with glass beads), which is probably caused by the different numbers of investigated pellets. In confocal laser scanning microscopy only one pellet per sample could be investigated while flow cytometry considered at least 50 pellets per sample, resulting in an increased statistical reliability.

Influence of Formulation Parameters on Redispersibility of Naproxen Nanoparticles from Granules Produced in a Fluidized Bed Process

The particle size reduction of active pharmaceutical ingredients is an efficient method to overcome challenges associated with a poor aqueous solubility. With respect to stability and patient's convenience, the corresponding nanosuspensions are often further processed to solid dosage forms. In this regard, the influence of several formulation parameters (i.e., type of carrier material, type and amount of additional polymeric drying excipient in the nanosuspension) on the redispersibility of naproxen nanoparticle-loaded granules produced in a fluidized bed process was investigated. The dissolution rate of the carrier material (i.e., sucrose, mannitol, or lactose) was identified as a relevant material property, with higher dissolution rates (sucrose > mannitol > lactose) resulting in better redispersibility of the products. Additionally, the redispersibility of the product granules was observed to improve with increasing amounts of polymeric drying excipient in the nanosuspension. The redispersibility was observed to qualitatively correlate with the degree of nanoparticle embedding on the surface of the corresponding granules. This embedding was assumed to be either caused by a partial dissolution and subsequent resolidification of the carrier surface dependent on the dissolution rate of the carrier material or by resolidification of the dissolved polymeric drying excipient upon drying. As the correlation between the redispersibility and the morphology of the corresponding granules was observed for all investigated formulation parameters, it may be assumed that the redispersibility of the nanoparticles is determined by their distance in the dried state.

Along the Process Chain to Probiotic Tablets: Evaluation of Mechanical Impacts on Microbial Viability

Today, probiotics are predominantly used in liquid or semi-solid functionalized foods, showing a rapid loss of cell viability. Due to the increasing spread of antibiotic resistance, probiotics are promising in pharmaceutical development because of their antimicrobial effects. This increases the formulation requirements, e.g., the need for an enhanced shelf life that is achieved by drying, mainly by lyophilization. For oral administration, the process chain for production of tablets containing microorganisms is of high interest and, thus, was investigated in this study. Lyophilization as an initial process step showed low cell survival of only 12.8%. However, the addition of cryoprotectants enabled survival rates up to 42.9%. Subsequently, the dried cells were gently milled. This powder was tableted directly or after mixing with excipients microcrystalline cellulose, dicalcium phosphate or lactose. Survival rates during tableting varied between 1.4% and 24.1%, depending on the formulation and the applied compaction stress. More detailed analysis of the tablet properties showed advantages of excipients in respect of cell survival and tablet mechanical strength. Maximum overall survival rate along the complete manufacturing process was >5%, enabling doses of 6 × 108 colony forming units per gram (CFU gtotal−1), including cryoprotectants and excipients.

Accelerated Particle Separation in a DLD Device at Re > 1 Investigated by Means of µPIV

A pressure resistant and optically accessible deterministic lateral displacement (DLD) device was designed and microfabricated from silicon and glass for high-throughput fractionation of particles between 3.0 and 7.0 µm comprising array segments of varying tilt angles with a post size of 5 µm. The design was supported by computational fluid dynamic (CFD) simulations using OpenFOAM software. Simulations indicated a change in the critical particle diameter for fractionation at higher Reynolds numbers. This was experimentally confirmed by microparticle image velocimetry (µPIV) in the DLD device with tracer particles of 0.86 µm. At Reynolds numbers above 8 an asymmetric flow field pattern between posts could be observed. Furthermore, the new DLD device allowed successful fractionation of 2 µm and 5 µm fluorescent polystyrene particles at Re = 0.5-25.

Influence of High, Disperse API Load on Properties along the Fused-Layer Modeling Process Chain of Solid Dosage Forms

In order to cope with the increasing number of multimorbid patients due to demographic changes, individualized polypill solutions must be developed. One promising tool is fused layer modeling (FLM) of dosage forms with patient-specific dose combinations and release individualization. As there are few approaches reported that systematically investigate the influence of high disperse active pharmaceutical ingredient (API) loads in filaments needed for FLM, this was the focus for the present study. Different filaments based on polyethylene oxide and hypromellose (HPMC) with different loads of theophylline as model API (up to 50 wt.%) were extruded with a twin-screw extruder and printed to dosage forms. Along the process chain, the following parameters were investigated: particle size and shape of theophylline; mechanical properties, microstructure, mass and content uniformity of filaments as well as dosage forms and the theophylline release from selected dosage forms. Especially for HPMC, increasing theophylline load enhanced the flexural strength of filaments whilst the FLM accuracy decreased inducing defects in microstructure. Theophylline load had no significant effect on the dissolution profile of HPMC-based dosage forms. Therefore, a thorough analysis of particle-induced effects is necessary to correlate mechanical properties of filaments, printability, and the dosage-and-release profile adjustment.