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Effect of Drying Methods of Alumina Powder and Graphene Oxide Mixture on the Mechanical and Electrical Properties of Sintered Composites Fabricated by Spark Plasma Sintering

P. V. Fokin, Nestor Washington Solis Pinargote, E. V. Kuznetsova, Pavel Peretyagin

Abstract

This paper presents a study on graphene-reinforced alumina ceramic composites and the resulting mechanical and electrical properties. Three drying methods were chosen for the fabrication of the initial mixtures: spray, freeze, and vacuum. Spark plasma sintering was chosen as a method of consolidating mixtures. A combination of spray drying and spark plasma sintering makes it possible to produce a high-density (99%) ceramic nanocomposite with improved mechanical properties. The hardness and crack resistance values were increased by 6 and 28%, respectively, compared to other materials studied in this work. This improvement is due to an extremely good dispersion of graphene in the composite, which leads to the decrease in the grain size of the ceramic matrix and consequently reduces the probability of crack occurrence. In addition to these exceptional mechanical properties, the sintered composites also showed high electrical conductivity, which allows the compacts to be machined using electrical discharge machining and thus facilitates the fabrication of ceramic components with sophisticated shapes while reducing machining costs.

Application of disaccharides alone and in combination, for the improvement of stability and particle properties of spray-freeze dried IgG

Daneshmand B, Faghihi H, Amini Pouya M, Aghababaie S, Darabi M, Vatanara A

Abstract

Spray-freeze drying (SFD) is a recently applied method to develop pharmaceutical powders. This study aimed to analyze the competence of Trehalose, Mannitol, Lactose, and Sorbitol instability and aerosolization of Immunoglobulin G (IgG) via SFD.

METHODS:

Induced soluble aggregates were quantified at 0 and 3 months, and 45 °C using size-exclusion chromatography. Conformation and thermogravimetric assessments were done by Fourier transform infrared spectroscopy and differential scanning calorimetry. Laser light scattering was performed to determine the particle sizes. Aerodynamic features were characterized by twin stage impinger and scanning electron microscopy.

RESULTS:

Although sugars/polyols preferably stabilized IgG following the process, storage stabilization was achieved in Trehalose, Trehalose-Lactose, Lactose, and Trehalose-Mannitol-based powders with soluble aggregates <5%. The conformation of antibody was preserved with β sheet content from 66.28% to 76.37%. Particle sizes ranged from 5.23 to 8.12 µm. Mannitol exhibited the best aerodynamic behavior, fine particle fraction (FPF: 70%) but high degree of protein aggregation during storage.

CONCLUSIONS:

SFD could favorably stabilize antibody using Trehalose and its combination with Lactose and Mannitol, and also, Lactose alone. Sorbitol disturbed IgG powder recovery. Incorporation of other types of excipient is required for efficient respiratory delivery of IgG molecules.

Keywords

IgG; Spray-freeze drying; aerodynamic behavior; disaccharides; stability

Advax augments B and T cell responses upon influenza vaccination via the respiratory tract and enables complete protection of mice against lethal influenza virus challenge

Tomar J, Patil HP, Bracho G, Tonnis WF, Frijlink HW, Petrovsky N, Vanbever R, Huckriede A, Hinrichs WLJ

Abstract

Administration of influenza vaccines via the respiratory tract has potential benefits over conventional parenteral administration, inducing immunity directly at the site of influenza exposure as well as being needle free. In this study, we investigated the suitability of Advax™, a stable particulate polymorph of inulin, also referred to as delta inulin, as a mucosal adjuvant for whole inactivated influenza vaccine (WIV) administered either as a liquid or dry powder formulation. Spray freeze-drying produced Advax-adjuvanted WIV powder particles in a size range (1-5 μm) suitable for inhalation. The physical and biological characteristics of both WIV and Advax remained unaltered both by admixing WIV with Advax and by spray freeze drying. Upon intranasal or pulmonary immunization, both liquid and dry powder formulations containing Advax induced significantly higher systemic, mucosal and cellular immune responses than non-adjuvanted WIV formulations. Furthermore, pulmonary immunization with Advax-adjuvanted WIV led to robust memory B cell responses along with an increase of lung localization factors i.e. CXCR3, CD69, and CD103. A less pronounced but still positive effect of Advax was seen on memory T cell responses. In contrast to animals immunized with WIV alone, all animals pulmonary immunized with a single dose of Advax-adjuvanted WIV were fully protected with no visible clinical symptoms against a lethal dose of influenza virus. These data confirm that Advax is a potent mucosal adjuvant that boosts vaccine-induced humoral and cellular immune responses both in the lung and systemically with major positive effects on B-cell memory and complete protection against live virus. Hence, respiratory tract immunization, particularly via the lungs, with Advax-adjuvanted WIV formulation as a liquid or dry powder is a promising alternative to parenteral influenza vaccination.

Keywords

Advax; Immune mechanisms; Inhalation; Mucosal; Powders; Protection; Whole inactivated influenza vaccine

Using two-fluid nozzle for spray freeze drying to produce porous powder formulation of naked siRNA for inhalation

Liang W, Chow MYT, Chow SF, Chan HK, Kwok PCL, Lam JKW

Abstract

Spray freeze drying is an attractive technology to produce powder formulation for inhalation. It can be used to generate large porous particles which tend to aerosolize efficiently and do not aggregate readily. It also avoids material to be exposed to elevated temperature. In this study, we reported the use of two-fluid nozzle to produce spray freeze dried powder of small interfering RNA (siRNA). The effect of atomization gas flow rate and liquid feed rate were inspected initially using herring sperm DNA (hsDNA) as nucleic acid model. The atomization gas flow rate was found to have a major impact on the aerosol properties. The higher the atomization gas flow rate, the smaller the particle size, the higher the fine particle fraction (FPF). In contrast, the liquid feed rate had very minor effect. Subsequently, spray freeze dried siRNA powder was produced at various atomization gas flow rates. The particles produced were highly porous as examined with the scanning electron microscopy, and the structural integrity of the siRNA was demonstrated with gel electrophoresis. The gene-silencing effect of the siRNA was also successfully preserved in vitro. The best performing siRNA formulation was prepared at the highest atomization gas flow rate investigated with a moderate FPF of 30%. However, this was significantly lower than that obtained with the corresponding hsDNA counterparts (FPF ∼57%). A direct comparison between the hsDNA and siRNA formulations revealed that the former exhibited a lower density, hence a smaller aerodynamic diameter despite similar geometric size.

Keywords

Gene silencing; Next generation impactor; Pulmonary delivery; Spray freeze drying; siRNA

Processing of sintered and CVD coated SiC/CNFs thin composite tubes

Mubina Shaik, Asit Kumar Khanra, Bhaskar Prasad Saha

Abstract

Silicon carbide (SiC) and its composite powders dispersed with 1–3 wt% carbon nano-fibres (CNFs) were spray freeze granulated to produce spherical granules with uniform composition. Powders were shaped to thin dense tubes for use in a harsh environment by cold isostatic pressing followed by pressureless sintering at 2150 °C for 1 h in argon and SiC coating by chemical vapour deposition (CVD) technique. The physical, microstructural and thermo – mechanical properties of the composite tubes were evaluated and compared with bare SiC tubes. Good dispersibility of CNFs and sintering additives in the matrix by spray freeze granulation processing technique resulted in more than 98.5% theoretical density of the composite tubes with superior mechanical properties. SEM & EBSD analysis show grains are platy and equiaxed in nature with many CNFs trapped at the triple points hindering the SiC grain growth which is also confirmed by TEM analysis. The thermal conductivity value of the composite was also found higher than bare SiC at all temperatures when measured up to 1000 °C due to uniform distribution of CNFs in the matrix.

Keywords

SiC composites, Spray freeze granulation, Cold isostatic pressing, Sintering, CVD

Drying Technologies for the Stability and Bioavailability of Biopharmaceuticals

Fakhrossadat Emami, Alireza Vatanara, Eun Ji Park, Dong Hee Na

Abstract

Solid dosage forms of biopharmaceuticals such as therapeutic proteins could provide enhanced bioavailability, improved storage stability, as well as expanded alternatives to parenteral administration. Although numerous drying methods have been used for preparing dried protein powders, choosing a suitable drying technique remains a challenge. In this review, the most frequent drying methods, such as freeze drying, spray drying, spray freeze drying, and supercritical fluid drying, for improving the stability and bioavailability of therapeutic proteins, are discussed. These technologies can prepare protein formulations for different applications as they produce particles with different sizes and morphologies. Proper drying methods are chosen, and the critical process parameters are optimized based on the proposed route of drug administration and the required pharmacokinetics. In an optimized drying procedure, the screening of formulations according to their protein properties is performed to prepare a stable protein formulation for various delivery systems, including pulmonary, nasal, and sustained-release applications.

Keywords

Biopharmaceuticals, drying technology, protein stability, bioavailability, pharmacokinetics

Influence of process variables on physical characteristics of spray freeze dried cellulose nanocrystals

Wissam Abdallah, Musa R. Kamal

Abstract

This study compares the characteristics of cellulose nanocrystal (CNC) agglomerates prepared using spray drying, freeze drying, and spray freeze drying. Moreover, the effect of the concentration of CNC in the initial aqueous dispersion (~ 0.5–10.0 wt%) on the morphology, particle size distribution, porosity and crystalline structure of the spray freeze dried CNC agglomerates were investigated. Scanning electron microscopy was used to characterize the morphology and particle size distribution, nitrogen adsorption–desorption isotherms were used to analyze the porous structure of the particles, and X-ray diffraction was used to analyze the crystalline structure of the particles. Spray drying of CNC resulted in 0.5–30 μm dense agglomerates of slightly deformed elliptical and mushroom cap shaped particles with no porous structure. Freeze drying resulted in large irregular shape flakes of various sizes ranging mainly between 150 and 350 μm. On the other hand, spray freeze drying of CNC from dilute suspensions (~ 0.5 wt%) resulted in larger (4–240 μm) light spherical particles that were highly porous (~ 110 times larger in BET surface area), with web-like inter-connected structure consisting of 10–30 nm thick nanofibrils. Increasing the concentration to 5 wt% produced slightly denser spherical particles (13–110 μm) with slightly less porous web-like structure.

Keywords

Cellulose nanocrystals, Spray freeze drying, Morphology, Particle size distribution, Porosity Crystallinity

Ultrasonic spray-freeze drying of partially purified microbial transglutaminase

Hilal Isleroglu, Izzet Turker, Mehmet Tokatli, Banu Koc

Abstract

Ultrasonic spray-freeze drying (USFD) was evaluated to produce partially purified microbial transglutaminase (mTGase) powder, and the effects of the process conditions (a nozzle frequency of 48–120 kHz and a flow rate of 2–8 ml/min) on enzyme activity and particle size were determined. Furthermore, the relative activity changes at each step of USFD and the behavior of the dried enzyme at extreme pH levels, high temperature and presence of the metal ions were investigated. Additionally, the final product produced by USFD and the powder produced by conventional freeze drying (CFD) were compared in terms of relative activities and physical properties. The results showed that atomizing conditions affected the particle size and, hence the enzyme activity. The enzyme activity was enhanced by ultrasonic atomizing at all conditions while most of the activity loss occurred in the drying step. The USFD provided higher enzyme activity, smaller particle size, better particle morphology and better reconstitution properties than CFD, which are explained by the ultrasonic atomizing and accelerated freezing steps of USFD. Also, the USFD sample preserved its stability in tough conditions, such as extreme pH levels, high temperature and the presence of metal ions better than the CFD counterpart.

Keywords

Spray-freeze drying, Ultrasonic atomization, Transglutaminase, Relative activity, Particle size

Encapsulation of cationic iridium(III) tetrazole complexes into a silica matrix: synthesis, characterization and optical properties

Ilaria Zanoni, Valentina Fiorini, Marcos Rosado, Belén Ballesteros, Maria Androulidaki, Magda Blosi, Simona Ortelli, Stefano Stagni, Michele Dondia and Anna Luisa Costa

Abstract

Herein we report the easy incorporation of brightly phosphorescent cationic iridium(III) tetrazole complexes into a silica based matrix via an easily scalable colloidal process. For this purpose, two cationic Ir(III) emitters bearing 5-aryl tetrazole ligands (R-CN4) were selected: blue [F2IrPTZ-Me]+ (C^N = F2ppy; N^N = PTZ-Me – 2-(2-methyl-2H-tetrazol-5-yl)pyridine) and red [IrQTZ-Me]+ (C^N = ppy; N^N = QTZ-Me – 2-(2-methyl-2H-tetrazol-5-yl)quinoline). The cationic complexes were readily adsorbed to negatively charged silica nanoparticles and trapped in the sol–gel matrix. The sol-to-solid phase transfer was performed by using an innovative spray-freeze-drying technique, leading to the formation of phosphorescent solid micro-granules. The structural and optical characterisation of the Ir(III) complexes together with SiO2 nanoparticles, nanosols (Ir@SiO2) and powders (Ir@SiO2 powders), revealed how the presence of the Ir(III)-based complexes did not alter the morphology of the colloidal silica or granulated phases. Moreover, the silica matrix did not interfere with the optical properties of the embedded complexes. The distribution of [F2IrPTZ-Me]+ and [IrQTZ-Me]+ in the spray-freeze-dried powders was qualitatively evaluated by fluorescence microscopy, revealing how the luminescent particles were homogeneously dispersed all over the silica matrix. Interestingly, in aqueous solution the release of complex [F2IrPTZ-Me]+ from the corresponding Ir@SiO2 powder is almost negligible, therefore suggesting that a strong interaction occurs between the host–silica matrix and the Ir(III) guest complex.

Spray freeze-dried monolithic silica aerogel based on water-glass with thermal superinsulating properties

Yuelei Pan, Xudong Cheng, Ting zhou, Lunlun Gong, Heping Zhang

Abstract

In this study, silica aerogels were prepared using water-glass precursor based on two drying strategies, namely conventional freeze drying (C-FD) and spray freeze drying (S-FD). It was known that the pore structure of silica aerogel can be optimized uniformly based on S-FD method when tert-butyl alcohol is directly utilized as a solvent. As a result, silica aerogels obtained by the S-FD method are monolithic with high thermal stability and low thermal conductivity, showing a great potential of thermal insulation materials for high-temperature environment.

Keywords

Silica aerogels, Spray, Freeze drying, Thermal insulation, Thermal stability