CELLETS® are MCC spheres, starter beads, cores for pharmaceutical and non-pharmaceutical formulations. CELLETS® serve as starter cores for layering processes with excipients and APIs.
Cellulose-derived spherical activated carbon offers a sustainable and efficient solution for adsorbing harmful compounds such as uremic toxins [1]. This carbon material is made from renewable cellulose, which is transformed into spherical particles and then activated to increase surface area and porosity. The spherical shape improves flow properties and reduces dust, making it ideal for pharmaceutical and biomedical applications. Moreover, it combines eco-friendly production with strong adsorption performance, providing a safer and more manageable alternative to traditional powdered carbon.
Uremic toxins are metabolic waste compounds that accumulate in the body when kidney function declines. These toxins interfere with biological processes and contribute to various health issues. Drugs and adsorbent therapies aim to remove them effectively, but such interventions must be selective to avoid removing essential molecules. Therefore, understanding both the functionality and potential toxicity of uremic toxins is crucial for designing safe and effective treatments. While adsorption therapies can improve toxin clearance, they also carry risks such as unintended drug adsorption or gut irritation, which must be minimized through precise material engineering.
Summary of the Publication
Shin et al. (2025) present a study on sustainable cellulose-derived spherical activated carbon designed for efficient uremic toxin removal. The research focuses on transforming cellulose into spherical carbon precursors and activating them to achieve high porosity and surface area. The resulting material combines uniform shape, hierarchical pore structure, and strong mechanical integrity. These properties make it ideal for biomedical use, particularly for toxin adsorption under gastrointestinal conditions. The authors report that the spheres maintain their shape across different pH levels and perform well even in dynamic or competitive adsorption environments.
Furthermore, the adsorption kinetics show that these spherical carbons quickly capture uremic toxin molecules such as indole derivatives. The authors compare the material with conventional activated carbon powders and find significant improvements in handling and biocompatibility. Importantly, the spheres demonstrate low cytotoxicity, which supports their suitability for oral or extracorporeal use. Because of their uniform size and reduced dusting, they minimize irritation risks and can be easily integrated into medical formulations or devices. In addition, the study discusses the environmental and economic benefits of using cellulose feedstocks, showing that this process supports circular material use and low-cost production.
A key part of the research involves CELLETS® 100 and CELLETS® 500. These cellulose microspheres act as templates during synthesis. CELLETS® 100, having a smaller diameter, produces finer activated carbon spheres, while CELLETS® 500 leads to larger ones. This variation allows the authors to tune pore structure, surface area, and mechanical properties. Consequently, CELLETS® 100-derived carbons show faster adsorption kinetics, whereas CELLETS® 500-derived carbons offer better durability. The study highlights that choosing the right CELLETS® grade directly influences the final adsorption performance and application potential of the spherical carbon.
Conclusion and Outlook
The development of cellulose-derived spherical activated carbon marks a major step toward safer and more sustainable toxin removal technologies. By merging green chemistry with advanced nanoengineering, these materials achieve both environmental and therapeutic goals. Their customizable size, stability, and porosity enable versatile use in pharmaceutical formulations and medical devices. Looking ahead, researchers must explore long-term biocompatibility, selective adsorption behavior, and performance in complex biological fluids. Moreover, scaling up production under pharmaceutical standards will determine clinical viability. With further optimization, cellulose-derived spherical activated carbon could revolutionize uremic toxin management and open new paths for eco-friendly therapeutic materials.
References
[1] Kyungmin Shin, Su-Bin Kim, Yong-Han Kim, Dae-Duk Kim, Seul-Yi Lee, Soo-Jin Park, Materials & Design,a available online 10 October 2025, 114892. doi:10.1016/j.matdes.2025.114892
Research Advances in MCC Pellet Technology and Applications
Scientific literature on MCC pellets highlights the growing importance of CELLETS® in pharmaceutical and scientific research. These microcrystalline cellulose spheres play a key role in developing reliable multiparticulate drug delivery systems. Researchers have investigated improved rivaroxaban dissolution, efficient film coating kinetics, and their use in orally disintegrating films. In addition, studies focus on colon-targeted vitamin B₂ release and fluidized-bed coating performance. Moreover, academic theses explore uniform hot-melt coating techniques and detailed modeling of tablet disintegration. As a result, MCC pellets continue to prove their versatility across many dosage forms. Consequently, this expanding body of literature reinforces the value of CELLETS® in advancing modern drug delivery technologies.
Selected Scientific literature on MCC pellets
Please, find scientific literature on MCC pellets (CELLETS®), MCC spheres. This list is constantly updated and does not claim to be complete. If you are author, scientist or R&D specialist, please submit your present publication to us for improving the visibility.
Research article Optimising the in vitro and in vivo performance of oral cocrystal formulations via spray coating European Journal of Pharmaceutics and Biopharmaceutics, Volume 124, March 2018, Pages 13-27
Dolores R. Serrano, David Walsh, Peter O’Connell, Naila A. Mugheirbi, Zelalem Ayenew Worku, Francisco Bolas-Fernandez, Carolina Galiana, Maria Auxiliadora Dea-Ayuela, Anne Marie Healy
Conference abstract Multiple-unit orodispersible mini-tablets International Journal of Pharmaceutics, Volume 511, Issue 2, 25 September 2016, Page 1128
Anna Kira Adam, Christian Zimmer, Stefan Rauscher, Jörg Breitkreutz
Research article Asymmetric distribution in twin screw granulation European Journal of Pharmaceutics and Biopharmaceutics, Volume 106, September 2016, Pages 50-58
Tim Chan Seem, Neil A. Rowson, Ian Gabbott, Marcelde Matas, Gavin K. Reynolds, AndyIngram
Research article Physical properties of pharmaceutical pellets Chemical Engineering Science, Volume 86, 4 February 2013, Pages 50-60
Rok Šibanc, Teja Kitak, Biljana Govedarica, StankoSrčič Rok Dreu
Research article Labscale fluidized bed granulator instrumented with non-invasive process monitoring devices Chemical Engineering Journal, Volume 164, Issues 2–3, 1 November 2010, Pages 268-274
Jari T. T. Leskinen, Matti-Antero H. Okkonen, Maunu M. Toiviainen, Sami Poutiainen, Mari Tenhunen, Pekka Teppola, Reijo Lappalainen, Jarkko Ketolainen, Kristiina Järvinen
Research article Granule size distribution of tablets Journal of Pharmaceutical Sciences, Volume 99, Issue 4, April 2010, Pages 2061-2069
Satu Virtanen, Osmo Antikainen, Heikki Räikkönen, Jouko Yliruusi
Research article New insights into segregation during tabletting International Journal of Pharmaceutics, Volume 397, Issues 1–2, 15 September 2010, Pages 19-26
S. Lakio, S. Siiriä, H. Räikkönen, S. Airaksinen, T. Närvänen, O. Antikainen, J.Yliruusi
Research article In vivo evaluation of the vaginal distribution and retention of a multi-particulate pellet formulation European Journal of Pharmaceutics and Biopharmaceutics, Volume 73, Issue 2, October 2009, Pages 280-284
Nele Poelvoorde, Hans Verstraelen, Rita Verhelst, Bart Saerens, Ellen De Backer, Guido Lopes dos Santos Santiago, Chris Vervaet, Mario Vaneechoutte, Fabienne De Boeck, Luc Van Borteld, Marleen Temmerman, Jean-Paul Remon
List – Publications with MCC spheres, 2008 and earlier
Research article Attrition strength of different coated agglomerates Chemical Engineering Science, Volume 63, Issue 5, March 2008, Pages 1361-1369
B. van Laarhoven, S.C.A. Wiers, S.H. Schaafsma, G.M.H. Meesters
https://cellets.com/wp-content/uploads/2021/03/books-2463779_1920-small.jpg601854Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2025-10-07 08:48:012025-11-10 16:26:03Scientific Literature on MCC Pellets: Insights into CELLETS®
There is a growing interest in enhancing the acceptability of paediatric pharmaceutical formulations. Solid oral dosage forms (SODF), especially multiparticulates, are being considered as an alternative to liquid formulations, but they may compromise palatability when large volumes are required for dosing. We hypothesised that a binary mixture of multiparticulates for paediatric use, designed to increase the formulation maximum packing fraction, could reduce the viscosity of the mixture in soft food and facilitate swallowing.
Using the Paediatric Soft Robotic Tongue (PSRT) – an in vitro device inspired by the anatomy and physiology of 2-year-old children – we investigated the oral phase of swallowing for multi-particulate formulations, i.e., pellets (350 and 700 µm particles), minitablets (MTs, 1.8 mm), and their binary mixtures (BM), by evaluating oral swallowing time, the percentage of particles swallowed, and post-swallow residues. We also conducted a systematic analysis of the effect of the administration method, bolus volume, carrier type, particle size, and particle volume fraction on pellets swallowability.
The results demonstrated that the introduction of pellets affected the flowing ability of the carriers, increasing shear viscosity. The size of the pellets did not appear to influence particle swallowability but raising the particle volume fraction (v.f.) above 10% resulted in a decrease in the percentage of particles swallowed. At v.f. 0.4, pellets were easier to swallow (+ 13.1%) than MTs, being the administration method used highly dependent on the characteristics of the multi-particulate formulation under consideration. Finally, mixing MTs with only 24% of pellets improved particle swallowability, achieving swallowing levels similar to those of pellets alone. Thus, combining SODF, i.e., MTs and pellets, improves MT swallowability, and offers new possibilities for adjusting product palatability, being particularly attractive for combination products.
Authors: Alejandro Avila-Sierra, Anais Lavoisier, Carsten Timpe, Peter Kuehl, Leonie Wagner, Carole Tournier, Marco Ramaioli
Read more
Get the full publication on paediatric solid oral dosage forms by Alejandro Avila-Sierra et al. here. Used MCC pellet: Cellets 350 and Cellets 700.
https://cellets.com/wp-content/uploads/2023/11/titelbild_Paediatric-solid-oral-dosage-forms-for-combination-products-Improving-in-vitro-swallowability-of-minitablets-using-binary-mixtures-with-pellets.jpg5881125Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2023-12-18 11:42:502023-12-18 11:42:50Paediatric solid oral dosage forms for combination products: Improving in vitro swallowability of minitablets using binary mixtures with pellets
https://cellets.com/wp-content/uploads/2022/09/parameter-titelbild.png6271200Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2023-08-22 09:15:152023-08-23 08:21:33Critical aspects of starter spheres in oral pellet formulations one should consider
Pellets are one of multiparticulate pharmaceutical forms and can offer numerous technical and biopharmaceutical advantages compared with single dose unit formulations, e.g. tablets and capsules. This study aimed at formulation of controlled-release pellets of doxazosin mesylate (DM), a widely used treatment for antihypertensive and benign prostatic hyperplasia. DM was loaded onto microcrystalline cellulose CELLETS® pellets using hydroalcoholic solution and alcoholic suspension layering techniques to achieve a minimum drug load of 4 mg DM/g pellets. DM-layered CELLETS were coated by Aquacoat dispersion (ready-made ethylcellulose dispersion) using a coating pan technique as a simple and widely utilized technique in pharmaceutical industry. Controlled-release DM-layered pellets showed a release profile comparable to the controlled-release commercial product Cardura® XL Tablet. Also, the mechanism of DM release from Aquacoat CELLETS® was mathematically modeled and imaged by scanning electron microscopy to elucidate drug release mechanisms from the prepared pellet formulations. Accelerated stability studies of the prepared pellets were performed under stress conditions of 40 °C, and 75 % RH for 3 months. In conclusion, preparation of controlled-release DM-layered CELLETS® is feasible using a simple and conventional coating pan technology. Read more about controlled-release doxazosin mesylate pellets.
References
H. A. Hazzah, M. A. EL-Massik, O. Y. Abdallah & H. Abdelkader, Journal of Pharmaceutical Investigation (2013), 43:333–342. doi:10.1007/s40005-013-0077-0
Additional information
CELLETS® are perfect starter beads for coating and layering of API, such as doxazosin mesylate. Multilayer formulation attempts enable defined release profiles and improved bioavailability. Check different pellet sizes from 100 µm to 1400 µm which fit to your formulation.
https://cellets.com/wp-content/uploads/2023/05/titelbild_Preparation-and-characterization-of-controlled-release-doxazosin-mesylate-pellets.jpg5881125Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2023-05-26 12:59:252023-08-22 16:02:06Preparation and characterization of controlled-release doxazosin mesylate pellets using a simple drug layering-aquacoating technique
https://cellets.com/wp-content/uploads/2022/02/Cellets_BCS_class_I.png6621394Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2022-02-17 15:10:072022-07-19 11:27:16BSC Class I APIs in oral formulations
This application note is based on content from Pohlen et al. [1]. Simvastatin (CAS number 79902-63-9) is a cholesterol-lowering agent with a low bioavailability of 5% [2,3]. This API is formulated as a lipid based drug delivery system for oral uptake. Two technologies, which are spray drying and fluidized bed layering technologies were compared with respect to the process and product characteristics of otherwise similar Simvastatin loaded dry emulsion systems. Investigated parameters are the process yield, encapsulation efficiency, relative product stability, particle morphology, drug content, and the relative increase in bioavailability.
Enhancing bioavailability
Some of the recently discovered new chemical entities (NCE) show a low solubility and high permeability (BCS class II), or even low permeability in the case of very high lipophilicity (BCS class IV).
This means a major challenge for formulation development in terms of assuring drug bioavailability [4,5]. A strategy for increasing the solubility are lipid based drug delivery systems (LBDDS). As main advantage, they are likely to solubilize the API and make it available for the absorption into the bloodstream [6]. Additionally, converting the liquid or semi-solid LBDDS into solid dosage forms eliminates undesired characteristics such as a lack of chemical stability and product portability, susceptibility for drug recrystallization and costly manufacturing [7]. Furthermore, solid dosage form solutions allow benefits, such as easy powder processing, flow and compression behavior, controlled drug release, improved patient safety. Among others, dry emulsions are a type of solidified LBDDS and allow carrying and releasing the encapsulated lipophilic API. In the following, some solidification process technologies are introduced. The required parameter for Wurster fluidized bed and spray drying are displayed in Table 2 and Table 3, respectively.
Opposite to the spray drying process, the fluidized bed process employs CELLETS® 200 as starter beads for layering. Several formulations are composed by Pohlen et al., the materials are listed in Table 1.
Table 2: Parameters and values for Fluidized bed layering.
Parameter
Value
Setup
Mini Spray Dryer B-290 (Büchi, CH)
Two-fluid
nozzle
1.4 mm
cap opening diameter
2.20 mm
Inlet airflow rate
28 m3/h
Inlet air temperature
145°C to 175 °C
outlet air / product temperature
75 °C to 80 °C
spraying rate
6 g/min
Drying time
180 s @ 80 °C
Starter pellets
200 g
starting
emulsion
1000 g
Table 3: Parameters and values for spray drying.
Process yield
Spray drying results on average in lower process yield than the fluidized bed results. The process yield for spray drying experiments is in average value of 71.5 %, and of 83.3 % for fluidized bed layering experiments. It is assumed, that in spray drying process adhesion of the smallest particles to the cyclone walls or outtake through the air stream occur.
Drug content
An averaged API content at 9.34 mg/g in fluidized bed experiments, and at 22.2 mg/g for spray dried dry emulsions is reached. Although spray drying offers a much higher drug content and more flexible formulations, the content variation between replicates is increased. The use a swirl air generator in the fluidized bed equipment increases process stability and allows an even larger amount of oil to be incorporated. It is possible increase the maximum amount of API to 22 mg/g onto the starter pellets. Anyhow, the fluidized bed technology suffers from sticky effects of oil phases which is not a big deal in spray drying processes.
Encapsulation efficiency
A low encapsulation efficiency shall be avoided as it causes drug losses during processing and increased production costs. The encapsulation efficiency in fluidized bed experiments is at 80.0 %, compared to spray drying experiments being at 68.4 %. A main issue of the spray drying technology might be higher process temperature leading to a higher risk of API degradation. Spray drying also suffers from a larger surface-to-volume area which might induce an increased risk of oxidation during the drying process.
Morphology and particle size
The main advantage of fluidized bed technology is the use of starter pellets, which are perfectly spherical starter beads. Following, API coating results in highly spherical coated particles with a high level of monodispersity and an average particle size around 336 µm (D50 value). Not mentionable, that spray drying technology results in smaller average particle sizes at 56 µm (D50 value), but the morphology shows a coarse, rough and undefined surface. In turn, dry emulsion layered pellets have better flow properties [8].
Redispersibility and oil droplet size
All re-dispersed oil droplets have a size of a few micrometers between less than 1 µm and less than 7 µm. Fluidized bed layering technology generally leads to larger droplets. Considering also the probable bimodal nature of the droplet size distribution, fluidized bed layering provides a narrower size distribution and thus better results. In turn, the fluidized bed technology might provide slightly better bioavailability.
Product stability
Stability is measured by means of the one-month relative drug content stability. The particles produced in the fluidized bed technology show a better one-month relative drug content stability than particles produced by spray drying. This might be caused by the higher monodispersity, larger particles and smoother surfaces. All properties minimize the risk of API gradation, treatment failure, or toxicity.
Dissolution
Both technologies show a superior dissolution behavior compared to the dissolution of pure crystalline API (less than 3 %) or a generic API tablet (less than 10 %). It has to be stated, that both technologies allow dissolution rates of more than 80 % within the first 30 minutes, wherein the Spray drying products show a slightly better and faster dissolution rate.
Bioavailability
Bioavailability of formulations from fluidized bed layered dry emulsion pellets provide the highest increase in relative bioavailability within the examined formulations, confirming that fluidized bed technology is superior to spray drying technology for potent or low dose APIs.
Summary
Fluidized bed layering and spray drying technology have been selected for analyzing the properties of dry emulsions. Simvastatin was selected as API, encapsulated in the dry emulsion.
Fluidized bed layering technology uses starter cores, such as CELLETS® as a dry emulsion carrier system, while spray drying does not.
The main advantage of the fluidized bed technology is the higher process yield, the better encapsulation efficiency and redispersibility, the defined morphology of the product causing better process handling and product stability.
Spray drying technology allows a higher drug content with better chances of formulation variation, and an even faster and more complete dissolution (Figure 1).
Figure 1: Advantages of technological methods compared to a pure API usage.
References
[1] M. Pohlen, J. Aguiar Zdovc, J. Trontelj, J. Mravljak, M. G. Matjaž, I. Grabnar, T. Snoj and R. Dreu, Eur J Pharm Biopharm (2021), S0939-6411(21)00353-2, doi:10.1016/j.ejpb.2021.12.004
[2] S. Geboers, J. Stappaerts, J. Tack, P. Annaert and P. Augustijns, Int. J. Pharm. 510 (2016) 296-303, doi:10.1016/j.ijpharm.2016.06.048
https://cellets.com/wp-content/uploads/2022/01/FB-SP-pureAPI.png6811201Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2022-01-04 18:02:182022-01-13 10:04:00Technologies for enhancing bioavailability of Simvastatin
Amorphous solid dispersions layered pellets solve a problem of poorly water soluble drugs. Speaking about oral drug formulations, drug carrier solutions based on starter cores are suitable for several drug classes and open new opportunities for modified drug release profiles. Layering and coating techniques, such as Wurster fluid bed process at different batch sizes, are well established.
However, an increasing number of poorly water soluble drugs challenges modern formulations. A novel approach improving the solubility of those drugs is to formulate them as amorphous solid dispersions (ASD) with a suitable polymer candidate [1]. In this study, Nifedipine was used as a model drug. Nifedipine manages angina, high blood pressure, Raynaud’s phenomenon, and premature labor [2].
Formulation & techniques
ASD formulations can be performed by hot-melt extrusion or spray drying technique. Both techniques have disadvantages such that hot-melt extrusion cannot be employed for temperature-sensitive drugs [3], and spray drying needs a further compaction step not to result in fine powder with poor flowability, broad particle size distribution and high sensitivity to electrostatic charge. Therefore, a further compaction step is required to obtain a freely flowable product [4].
In this context, two techniques for the preparation of ASDs are compared: A 6”-Wurster fluid bed with Type-C bottom plate (Glatt, Germany) and spouted bed (ProCell5™ with Zig-Zag-sifter, Glatt, Germany) are used.
The formulation contains the drug and a stabilizing co-polymer (Kollidon®, KVA64, BASF, Germany). Nifedipine and Kollidon are mixed resulting in a drug load of 40 % (w/w) and dissolved in Acetone (30 % w/w solid content).
Parameter
FB
SB
Spray rate [g/min]
20
20-35
Product temp. [°C]
50-60
50-60
Process gas temp. [°C]
65
80
Process air flow [m³/h]
180-200
65-120
Spraying nozzle diameter [mm]
1.2
1.2
Spraying pressure [bar]
2.0
0.5
Table 1: Manufacturing parameters for fluid bed (FB) and spouted bed (SB).
In the fluid bed process, microcrystalline pellets (Cellets® 500, IPC Dresden, Germany) were layered with the spraying solution such that a drug load of 21.8 % (w/w) is reached. In the spouted bed process, fine powder is generated by spray drying, further agglomeration and layering. An overview on the process parameters is given in Table 1.
Dissolution Tests
Dissolution tests were conducted in a PBS buffer at pH 6.8 and 37 °C (± 0.5 °C). A physical mixture of Nifedipine and KVA64 (40 % w/w drug load) is used as reference.
Results
In the following, results from both experiments, which are amorphous solid dispersions layered pellets (fluid bed) and ASD pellets from direct pelletization (spouted bed) are compared.
Flowability and particle size
ASD layered pellets show a better sphericity, higher level of monodispersity and better flowability properties than the ASD pellets from direct pelletization (Figure 2). Nonetheless, it has to be pointed out that both techniques result in a high particle quality for capsule filling. Analysis data is shown in Table 2.
Parameter
FB
SB
D10 [µm]
824 ± 23
559 ± 28
D50 [µm]
943 ± 13
732 ± 50
D90 [µm]
1091 ± 11
1374 ± 410
Bulk density [g/L]
427
280
Flowability [s/100g]
12.1
16.2
Table 2: Analysis of ASD layered pellets (FB) and ASD pellets from direct compaction (SB).
Fig. 2a: SEM images of processed pellets. A: ASD layered pellets based on Cellets® (FB)
Fig. 2b: SEM images of processed pellets. B: ASD pellets from direct pelletization (SB)
Dissolution profiles
Independent from the processing technique, pellets achieved an approximately factor 2 higher end concentration than the physical mixture. Pellets obtained from the fluid bed process showed a clear supersaturation phase after 1 hour and a generally higher dissolution rate than pellets obtained from the spouted bed process. Contrarily, the dissolution rate of the latter pellets approaches the supersaturation phase more continuously after 3 hours.
Fig. 3: Dissolution as a function of time. Black: ASD layered pellets (FB). Red: ASD pellets from direct pelletization (SB). Blue: physical mixture.
Summary
Both techniques, fluid bed and spouted bed as well, can be employed for manufacturing amorphous solid dispersions with good flow properties and dissolution profiles. Both techniques can be scaled up to pilot and production scale for batch or continuous manufacture of freely flowable ASDs. Cellets® serve stable and reliable cores for this venture.
Acknowledgement
We gratefully acknowledge Dr. Annette Grave and Dr. Norbert Pöllinger (Glatt Pharmaceutical Services, Germany), and Prof. Karl G. Wagner and Marius Neuwirth (University Bonn, Germany).
Cellets are inert starter cores made of microcrystalline cellulose (MCC). They play an important role in new formulations of solid dosage forms. As a carrier system for actives, the chemical inertness and surface smoothness are crucial parameters. Additionally, high level of robustness and sphericity simplify formulations and technical processes, such as fluidized bed technologies for coating and layering. In a joint study between the University of Hertfordshire and Freeman Technology (a Micromeritics company), the effect of pellets’ size on the behavior in a Wurster process is explained. Wurster fluid bed coating of Cellets with particle size larger than 400 µm is unproblematic. However, decreasing the particle size begins to complicate the coating process. So, powder rheology was used to compare Cellets with different particle sizes in terms of their effect on the powder flow in the Wurster fluid bed coater. For deeper knowledge, we strongly recommend reading investigations by V. Mohylyuk et al. [1]
Materials
Cellets® 90, 100, 200 and 350 (D50-size from 94 µm to 424 μm, Ingredientpharm, Switzerland). MCC powder Avicel® PH-102 (supplied by IMCD UK Ltd., UK) is included in the investigations, as it is widely used in industry and can be used by readers for comparison with other studies.
Wurster fluid-bed
Wurster process is a bottom-spray method, employed as a coating technology, for layering powder-like particles in a fluidized bed system (Figure 1). The process can be separated in different zones of mass flow, such as the down-flow zone or the horizontal transport zone. The flowability in these zones is crucial for homogeneous and efficient coating of the particles.
Figure 1: Wurster process is a bottom-spray method for layering powder-like particles in a fluidized bed system.
Hereby, the size of particles might play an important role. The narrow size distribution of MCC pellets is shown in Figure 2 and Figure 3. Measured data is presented in Table 1.
The compact Cellets with fair sphericity, zero friability and a high level of surface smoothness show a fair mass flow rate which is almost independent of particle size at given experimental conditions and was determined by the gravitational funnel method. The reference MCC powder did not flow through the orifice.
Excipient
PSD
[µm]
Span
[µm]
Flow rate
[g/s]
Avicel PH-102
115a
1.85
No flow
Cellets 90
94b
0.44
1.76
Cellets 100
163b
0.27
2.06
Cellets 200
270b
0.34
1.89
Cellets 350
424b
0.22
1.83
Table 1: Particle size distribution (D50) value and span by laser diffraction (a) and digital microscopy (b), and the mass flow rate by gravitational funnel method (5 mm diameter orifice) for the investigated excipients.
Impact of the Cellets’ size
The impact of the Cellets’ size on bulk powder behavior can only be estimated by screening additional parameters. In addition to the mass flow rate, standard pharmacopoeia methods such as bulk/tapped density were initially employed for the characterization of the powder’s properties. This was extended to rotating drum measurements providing the dynamic angle of repose and dynamic cohesivity index. Via powder rheology the conditioned bulk density, basic flowability energy, specific energy, pressure drop, permeability and compressibility (Figure 4) were obtained [1].
By picking the compressibility of Cellets at an applied force of 10 kPa normal stress, two key points need to be mentioned: (a) smaller particle size induces a higher rate of compressibility; (b) Cellets are less compressible than the reference MCC powder.
These findings are part of the open question on powder flow in a Wurster process. It is expected, that Cellets with a lower compressibility will result in better flow behavior in the fluidized bed.
Microscopic imaging of Cellets 100 (top left), 200 (top right), 350 (bottom left) with 1 mm scale bar and 100x magnification. Bottom right: surface of Cellets 350 in 1000x magnification.
Compressibility at 10 kPa normal stress on Cellets with varying particle size (D50) and Avicel® PH-102.
Summary
The flow of Cellets’ through a Wurster fluid-bed coater is likely to show improved performance as the Cellets’ particle size increases. Among others, a lower compressibility demonstrates a rheological behavior which is superior to MCC.
References
[1] Mohylyuk V, Styliari ID, Novykov D, Pikett R, Dattani R. Assessment of the effect of Cellets’ particle size on the flow in a Wurster fluid-bed coater via powder rheology. J D Deliv Sci Tec. 2019; 54: 101320, doi: 10.1016/j.jddst.2019.101320.
https://cellets.com/wp-content/uploads/2021/04/Figure-3.jpg12001200Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2021-04-13 11:31:352022-07-27 13:24:36Impact of the particle size on powder behavior in a Wurster fluid-bed process
The renaissance of micropellets is promoting innovative technologies
In recent years, formulations based on pellets and micropellets have been the trend. New technologies make it possible to circumvent property rights for active ingredients and are therefore very popular with pharmaceutical customers. But which technologies are the most important?
Pellets are the jack-of-alltrades of solid dosage forms. Positioned somewhere between powder and granulate, they make bitter medicine more palatable and can even awaken a child’s instinct to play when the dosage forms are imaginative enough. One well-known example is the Xstraw, a plastic tube shaped like a drinking straw which is filled with pellets of active ingredient, through which children or elderly people can take in the medicine with water. Pellets in tablets are also making a splash – hybrids which combine all the advantages of both dosage forms. The pioneers in the development of these formulations, known as Multiple Unit Pellet Systems (or MUPS for short), was Astra Zeneca in 1999. Their move to embed the proton pump inhibitor Omeprazole in micropellets and then compress these pellets into immediate release tablets was an award-winning one at the time. The development of MUPS and Xstraw symbolizes the impetus pellets have fueled in recent years.
Klaus N. Möller, Head of Business Development at Glatt in Binzen / Germany, explains: “New excipients, coating materials and sophisticated processes allow us to extend the patent protection period and to make the dosage form more attractive.“
The number of patents registered yearly for pellet-based formulations has increased exponentially and is set to continue. According to research performed by IMS Health, the market for OSD (Oral Solid Dosage Forms) is growing by 6 to 8 percent every year. The number of drugs approved by the FDA also reflect this trend: in 2015, more than half were solid products.
Pellets, as defined by pharmacy guru Prof. Peter Kleinebudde are “an isometric agglomerate of powder particles in an approximate spherical or cylindrical form”, and are a task for perfectionists. The smoother and rounder the pellets, the better they are at fulfilling their purpose. The equipment manufacturer Glatt and their specialists from Pharmaceutical Services have been actively ursuing the subject for years.
There are two fundamental ways of making active ingredient pellets: direct pelletization, in which the powdered active ingredient and excipient combine in a matrix, and active ingredient layering, in which uses side spray or Wurster technology to apply the active ingredient to a starter core of sugar or microcrystalline cellulose.
A case for the specialists
One interesting process variant for matrix pellets is the extrusion of wet granulate in a basket extruder and subsequent rounding in a spheronizer. Möller elucidates: “Continuous wet granulation, followed by extrusion, spheronization and drying now make it possible to perform continuous processes”. Active ingredient pellets made like this can then be covered with a functional coating, be continuously mixed with excipients and be directly compressed into a MUPS tablet. The challenge is to avoid separation of the ingredients and destruction of the tablets during pressing.
Glatt, whose portfolio comprises all granulation and pellet manufacturing techniques, has spent recent years developing additional ways of “fine tuning” the pellet process and has opened up a range of new, interesting possibilities for the lifecycle management of active ingredients.
Pellets and micropellets can be further processed into a wide range
Applying the final touches
But what differentiates the manufacturing of granulates from the manufacturing of pellets? From a pharmaceutical point of view, both processes are closely related and are only separated by the form of the particle, since the ideal shape for pellets is a sphere. There are also definite commonalities in procedure. As Möller explains: “The fluidized bed can be used for both granulation and pelletization. This is why we configure fluidized bed machines on request to be multipurpose installations which then allow the continuous manufacturing of pellets. The individual process modules for direct pelletization with rotor technology, for layering active ingredient and for pellet coating with Wurster technology or the simple drying of wet granulates can be added as necessary. Wurster technology has been used in practice for many years: it is a fluidized bed technique in which starter cores or active ingredient pellets are sprayed with a insists. Möller says: “This method is robust and, because the process is so stable, it’s generally the most popular way to process pellets.”
Depending on the composition of the tablets, processing can last anywhere between eight and ten hours. The knack is knowing how to optimize the efficiency and times of the production process. Additionally, Möller recommends timely expert assistance during the development of the pellet formulation and the production process: “Right from the beginning, it will help to avoid mistakes and to keep an eye on process times and manufacturing costs”.
Micropellets and more
Glatt’s development team demonstrated how to refine an established process with the fluidized bed agglomeration technique known as MicroPx. The trick is to use the Conti process, which was conceived in Pharmaceutical Services’ laboratories in Binzen: first, the active ingredient/excipient liquid is spray-dried to a very fine product dust in a fluidized bed and agglomerated into tiny primary particles. The micropellets then build up, layer by layer, until the desired size is reached. The heart of this technology is a zigzag classifier which continuously ejects particles of sufficient size from the process, while simultaneously allowing smaller particles to reenter the process chamber where they continue to grow. Möller explains that the result of this method are high dosage active ingredient pellets in the size range of 100 to 400 μm with a narrow particle size distribution and content uniformity of a consistent 90 to 95 percent. This means that one significant limitation of former times is now no longer an issue: for many years, the volume of a pellet- filled capsule was larger — and therefore much harder to swallow — than the equivalent tablet with the same dose and composition. The use of microencapsulation, which changes bitter-tasting active ingredients into tasteless microparticles, means the taste is much improved now, too. Micropellets can be also pressed into tablets or MUPS tablets which already begin disintegration in the mouth. But the reason pharmaceutical companies find the MicroPx process so exciting is that it makes completely new formulations possible and therefore allows the legal circumvention of property rights. The technology experts have long known the secret to the perfect pellet, too, an answer provided by Complex Perfect Spheres Technology (CPS). CPS is a souped-up rotor process for fluidized bed machines that uses direct pelletization to yield functionalized pellets and micropellets which are perfectly round and smooth. Unlike classic rotor technology, the modified technique uses a tapered rotating disc which allows the movement of particles to be directed and pelletization to be performed to a defined endpoint. The results are perfectly spherical pellets of exactly defined sizes of between 100 and 1500 μm and extremely narrow size distribution. This is how Glatt’s own Cellets of microcrystalline cellulose are created, which are used as starter cores for pellets and in the Wurster process, for example — thus completing the formulation cycle.
Author
Klaus Möller, Head of Business Development Glatt Process Technology Pharma
https://cellets.com/wp-content/uploads/2021/03/Pellets-and-micropellets-can-be-further-processed-into-a-wide-range.jpg5571257Bastian Arlthttps://cellets.com/wp-content/uploads/2016/10/Logo_Cellets_2016_website.pngBastian Arlt2021-03-22 10:39:542022-07-27 13:25:59The path to the perfect sphere
ingredientpharm
ingredientpharm
ingredientpharm
Ingredient Pharm
Ingredientpharm
glatt.com
