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Formation of nanofibrous alumina by polyvinyl alcohol assisted sprayfreeze-drying technique

Abdur Razzaque, Satoshi Irie, Koji Nakane

Abstract

In the experiment, three-dimensional net-structured alumina nanofibers were successfully prepared by spray-freeze-drying
process for the first time with an average diameter below 100 nm. Alumina nanofibers were obtained from polyvinyl alcohol
(PVA) and boehmite precursor nanofibers after calcination at 500 °C for 5 hours. At first, boehmite nanoparticles as a source of
alumina were dispersed with 1 wt% PVA aqueous solution to form alumina nanofibers with different weight ratios of PVA and
alumina. The best weight ratio of PVA and alumina (30:70) was selected on the basis of fiber morphology, nano diameter, thermal
stability and precipitation of boehmite nanoparticles. This best weight ratio of PVA and alumina was applied again to form
alumina nanofibers from PVA/boehmite precursor nanofibers which were prepared using 0.5, 0.1 and 0.01 wt% PVA aqueous
solutions. The best alumina nanofibers were obtained when 0.1 wt% PVA solution was used. Here, average fiber diameter of
alumina nanofibers was 79 nm along with more interconnected net-structure and higher specific surface area. Crystalline phase
of alumina nanofibers was transferred from γ-alumina to α-alumina when calcination temperature increased from 500 °C to
1200 °C. Specific surface area and porosity of alumina nanofibers significantly decreased with the increase of calcination
temperature.

Keywords:

Spray-freeze-drying, Precursor nanofiber, Alumina nanofiber, Net-structure

Lyophilised and Thermostable mRNA-Lipid Nanoparticle Vaccines: Excipient Selection, Process Design and Cold–Chain-Independent Distribution for Low- and Middle-Income Countries

Anish Verma, Sarbjot Singh, Anita Devi

Abstract

The messenger RNA lipid nanoparticle (mRNA-LNP) platform reached the clinic at extraordinary speed, yet it carried an inconvenient inheritance: a liquid drug product that survives only at deep sub-zero temperatures. The frozen chain that this demands, running from roughly-80 to-20 degrees Celsius, is precisely the infrastructure that low-and middle-income countries (LMICs) most often lack, and it converts a scientific triumph into a distribution failure at the last mile. This review argues that the instability is a formulation problem with a formulation solution, and that lyophilisation is the most mature route to a refrigerator-stable or ambient-stable mRNA vaccine. It examines why the aqueous particle degrades, working through the chemistry of RNA backbone hydrolysis and lipid ester cleavage that the resident water in the particle core sustains. It then treats the two levers that a formulator actually controls. The first is excipient selection, where disaccharides such as sucrose and trehalose vitrify the matrix and replace hydrogen bonds at the lipid headgroups, while bulking agents and a matched buffer set the collapse behaviour of the cake. The second is process design, where the freezing, primary drying and secondary drying stages must each be held below the critical temperature of the freeze concentrate to avoid collapse, aggregation and residual moisture that would defeat the exercise. Evidence that an optimised cycle can compress a multi-day process to under a day, hold particle size and encapsulation within narrow bounds, and confer refrigerated shelf lives measured in months is now consistent across several independent groups. The review closes on the distribution question, quantifying what a warm-stable presentation would mean for LMIC immunisation and setting out the manufacturing and regulatory work that still stands between the bench result and a licensed product.

Keywords:

mRNA vaccines; lipid nanoparticles; lyophilisation; freeze-drying; thermostability; cryoprotectants; cold chain; low- and middle-income countries.

From Pharmacological Uncertainty to Inhalation Development: An Evidence-Gated Roadmap for Codonopsis-Derived Triterpenoid Saponins

Xiaohua Zhang, Chunxia Yang, Ping Wang, Ping Yang, Shanru Liu, Shubin Liu & Xiaoling Yang

Abstract

Codonopsis-derived triterpenoid saponins merit investigation because preclinical studies identify immunomodulatory activity and a biologically active parent-metabolite relationship. Pulmonary delivery could increase exposure at a lung target while limiting unnecessary systemic exposure, but uncertain immune direction, membrane interactions, pulmonary absorption, and repeated-dose safety prevent a direct formulation recommendation. This critical narrative review evaluates chemical identity, lung pharmacology, and transferable delivery precedents using targeted searches updated through September 16, 2026 and a structured assessment of study relevance and limitations. Evidence is distinguished by material and route: defined saponins or fractions, composition-characterized botanical extracts, the associated metabolite echinocystic acid, and unrelated engineering precedents. Earlier anti-inflammatory lancemaside A studies and a 2026 immunostimulatory study in interferon-gamma-primed macrophages require matched replication rather than a claim of an established biphasic mechanism. Oral C. lanceolata extract efficacy in allergic lung inflammation and echinocystic acid pharmacology support further investigation but do not validate an inhaled parent saponin. No qualifying therapeutic aerosol-inhalation study of a Codonopsis saponin, standardized saponin fraction, or composition-characterized extract was identified in the searches performed. We propose four connected development stages: select a reproducibly beneficial active entity; establish pulmonary safety and local pharmacokinetics/pharmacodynamics with the simplest feasible formulation; correct a demonstrated delivery limitation when necessary; and integrate efficacy, device-patient suitability, storage stability, and manufacturing. Lipid carriers, spray-dried or spray-freeze-dried powders, mucus-modifying surfaces, and targeting systems are assessed against their measured benefits and failure modes. Numerical targets remain explicit development hypotheses rather than regulatory standards. The framework supports local pulmonary treatment as the initial objective and makes progression, reformulation, and termination conditional on evidence.

Keywords:

Codonopsis lanceolata, lancemaside A, echinocystic acid, Spray freeze-drying, triterpenoid saponins, pulmonary drug delivery, inhalation

Selecting an appropriate binder to prepare alumina granules via spray freeze granulation drying

Naoki Kondo, Akihiro Shimamura, Mikinori Hotta, Junichi Tatami, Shinya Kawaguchi

Abstract

Spray freeze granulation drying (SFGD) is a granulation technique, involving the freezing of sprayed droplets, followed by freeze drying. This technique affords soft granules, which is advantageous for producing sintered bodies with few defects. However, non-spherical and/or hard granules are sometimes formed by SFGD, and the sintered body fabricated from such granules shows reduced density and strength. The formation of such non-spherical and/or hard granules is expected to be avoided by selecting an appropriate binder. Therefore, in this study, four types of binders (water-soluble acrylic polymer, acrylic emulsion, and poly vinyl alcohol with low and high degree of polymerization) were tested to produce alumina granules via SFGD. The shapes and properties of the granules, as well as densities and strength of the sintered bodies, were evaluated. By choosing a suitable binder, the formation of non-spherical granules can be significantly reduced, and soft granules are obtained. These leads to a sintered body with high density and high strength. The acrylic emulsion binder was found to be the best performing binder among the four binders.

Keywords:

Spray freeze granulation drying, Binder, Granule, Sintering, Alumina

Application of Natural Polymers to Enhance Probiotic Stability Following the Spray Freeze Drying Method.

M. Akrami, Mohammad Mahdi Omranpoor, Milad Imeni, Azadeh Emami, Vahid Ramezani

Abstract

Probiotics, defined as live microorganisms that confer health benefits on the host, are sensitive to environmental stresses. However, the stability of Lactobacillus casei during spray freeze drying (SFD) under different encapsulation conditions has not been thoroughly investigated. In various concentrations, the influence of three natural polymers, sodium alginate, xanthan gum, and chitosan, is evaluated on the stability and physicochemical properties of SFD-processed Lactobacillus casei powder at different storage temperatures, 4 °C, 25 °C, and 40 °C, for 90 days, as well as probiotic stability in simulated gastric and bile-containing media. In addition, the particles’ physicochemical properties are evaluated by tap density, FTIR, SEM, and DSC analysis. Probiotic microparticles after SFD are composed of a highly porous amorphous phase of polymers and various polymorphous structures of sucrose. Data shows that bacterial viability exceeds 90% immediately after SFD when low sodium alginate or xanthan gum concentrations were used. In addition, chitosan negatively impacts probiotic viability. However, applying a higher polymer ratio is problematic in long-term storage and contact with gastric fluid.

Keywords:

Spray freeze drying

Tailored Sugar-Mediated Porous Particle Structures for Improved Dispersion of Drug Nanoparticles in Spray-Freeze-Drying.

Kumi Semba, Kazunori Kadota, Tero Kämäräinen, Yuzuki Nakayama, Yuta Hatanaka, Hiromasa Uchiyama, H. Arima-Osonoi, Kazumasa Sugiyama, Y. Tozuka

Abstract

We fabricated porous particles incorporating sugars (mannitol, sucrose, or dextran) and fenofibrate nanoparticles (FNPs) by using spray-freeze-drying (SFD). The type of sugar significantly influenced the pore architecture of the resulting SFD particles. Rapid freezing of droplets containing dextran produced ice encapsulation within a dextran matrix, forming porous dextran particles. In the presence of FNPs, the particle size (approximately 4 μm) and pore volume (0.3 cm3/g) of SFD dextran were barely affected. In contrast, SFD particles derived from mannitol and sucrose exhibited denser structures with a lower pore volume than dextran. SFD mannitol incorporating FNPs produced porous structures. FNPs containing surfactant and polymer, which reduced surface tension and increased viscosity, promoted the formation of small droplets with a polymeric structure and porous particles with a relatively sharp size distribution with a median around 5 μm. FNPs were uniformly distributed in SFD dextran, which featured large pore structures, whereas in SFD mannitol, the Raman signal of FNPs was more broadly distributed across the powder samples. Both morphologies contributed to enhancing the FNP dispersibility within a redispersed suspension of SFD particles. FNPs in SFD mannitol and dextran matrices maintained their particle size distribution from before SFD, showing no aggregation upon redispersion. Dextran formed a highly porous network irrespective of the presence of FNPs, whereas mannitol tended to alter the particle attributes upon FNP inclusion. In conclusion, SFD particles derived from dextran and mannitol might help to increase FNP dispersibility by increasing the formation of porous architectures.

Keywords:

Spray freeze-drying

Water based processing of LiFePO4/C cathode material for Li-ion batteries utilizing freeze granulation

Jessica Orlenius, O. Lyckfeldt, Keivan Amiri Kasvayee, P. Johander

Abstract

A water based solid state synthesis of LiFePO 4 has been conducted by utilizing freeze granulation. Various processing conditions were tested and achieved powder properties were characterized by density, XRD, specific surface area, carbon content, conductivity and SEM. Freeze granulation, a novel method for precursor preparation was shown to be an effective method to provide high degree of homogeneity prior to calcination and high ultimate yield of pure LiFePO 4 . Cathodes were manufactured by water based as well as NMP system based tape casting. A commercial LiFePO 4 /C powder was also characterized and used to manufacture cathodes as comparison in this study. Charge cycling tests showed promising results with high capacity and long term stability, well in the range of what the commercial powder provided. Post-milling of calcined powder prior to paste preparation for tape casting tended, however, to retard the capacity owing to disturbed carbon distribution and loss of conductivity of the LiFePO 4 /C. In comparison with the solvent system for cathode manufacturing, the water based system gave similar cell performance, illustrating the possibility to apply a more environmentally sustainable processing of Li-battery cells.

Keywords:

Freeze granulation

Influence of Porosity on Performance of Freeze-granulated Fe2O3/Al2O3 Oxygen Carriers Used for Chemical Looping Combustion

Yi Zhang, A. Rubel, Sameh Mehrez, J. Neathery, Kunlei Liu

Abstract

Chemical looping combustion (CLC) is a promising solution for the next coal-fired power generation technology with inherent CO2 separation capability. One of the critical aspects for the development of the CLC process is to develop suitable oxygen carrier (OC) particles to transfer oxygen to the fuel in the absence of air. Relevant studies have focused on active material screening, thermodynamic analysis and operational tests. This investigation was conducted on the microstructural property of OCs, to be specific, the particle porosity effect on the performance of iron-based OCs. Fe2O3, supported on Al2O3 was used as the oxygen carrier. The effect of water content of the spray slurry used to produce the OC was varied to determine the influence of OC porosity on reactivity, oxygen transfer capacity and mechanical durability. A preliminary test was done to establish the minimum and maximum water percentage needed to make slurry. A process that included freeze granulation (FG), freeze drying, and calcination was used to prepare four samples of iron oxide/alumina with various water-to-solid phase ratios. A scanning electron microscope (SEM) was used to characterize the porosity of FG Fe2O3/Al2O3 particles. A direct relationship was observed. A Shimpo FGE-10X force gauge was used to measure the crushing strength of selected samples. A thermogravimetric analyzer (TGA) coupled with a mass spectrometer (MS) was used to study the change in reaction rates through multiple reduction-oxidation cycles of the samples. Crystallinity of the OCs in reduced and oxidized forms were confirmed by XRD analysis.

Assembled Carbon Nanostructure Prepared by Spray Freeze Drying for Si-Based Anodes

Wanxiong Zhu, Liewen Guo, Kairan Li, Mengxue Shen, Chang Lu, Zipeng Jiang, Huaihe Song, Ang Li

Abstract

Silicon-based materials provide a new pathway to break through the energy storage limits of battery systems but their industrialization process is still constrained by inherent diffusion hysteresis and unstable electrode structures. In this work, we propose a novel structural design strategy employing a modified spray freeze drying technique to construct multidimensional carbon nanostructures. The continuous morphological transition from carbon nanowires to carbon nanosheets was facilitated by the inducement of ultralow-temperature phase separation and the effect of polymer self-assembly. The unique wrinkled carbon nanosheet encapsulation effectively mitigated the stress concentration induced by the aggregation of silicon nanoparticles, while the open two-dimensional structure buffered the volume changes of silicon. As expected, the SSC-5M composite retained a reversible capacity of 1279 mAh g−1 after 100 cycles at 0.2 C (1 C = 1700 mAh g−1) and exhibited a capacity retention of 677.1 mAh g−1 after 400 cycles at 1 C, demonstrating excellent cycling stability. This study offers a new strategy for the development of silicon-based energy storage devices.

Keywords:

Spray Freeze Drying

Li2TiO3 pebble fabrication by freeze granulation & freeze drying method

A. Shrivastava, T. Kumar, Riddhi Shukla, P. Chaudhuri

Abstract

Lithium titanate (Li2TiO3) ceramic is one of the candidate tritium breeding material for fusion reactor. Li2TiO3 in the form of spherical pebbles are kept inside the canisters of the fusion blanket. Prior to pebble fabrication, Li2TiO3 powder was prepared by using Li2CO3 and TiO2 as precursor materials by solid-state reaction method. To make the powder-fine, they were mixed and milled together inside the high energy planetary ball mill followed by calcination at 1000 °C for 5 h. An experimental setup based on the freeze granulation and freeze-drying method was developed in-house, where the green pebbles of 1.5–2 mm were prepared by dropping Li2TiO3 slurry into liquid nitrogen through the 0.6 mm nozzle opening. The pebble drying was performed by the sublimation process at – 60 °C under vacuum followed by the sintering of green pebbles at 950 °C, 1050 °C, and 1150 °C. Various characterizations of the powder and pebbles were carried out to ascertain its phase purity, surface morphology, porosity, pore-size distribution, etc. The results of those characterizations confirm the single-stage reaction, phase purity, desired dimension of pebbles, and their physical and thermal properties. The details of those characterizations along with the dependence of sintering temperatures with the pore size distribution and bulk density of pebbles are discussed in this paper.

Keywords:

Freeze granulation, freeze drying