Binder Jetting Additive Manufacturing of Ceramics: Comparison of Flowability and Sinterability Between Raw and Granulated Powders

Binder Jetting Additive Manufacturing of Ceramics: Comparison of Flowability and Sinterability Between Raw and Granulated Powders

Wenchao Du, Guanxiong Miao, Lianlian Liu, Zhijian Pei, Chao Ma

Abstract

The objective of this study is to compare three different feedstock powders for the binder jetting process by characterizing their flowability and sinterability. Binder jetting additive manufacturing is a promising technology for fabricating ceramic parts with complex or customized geometries. Granulation is a promising material preparation method due to the potential high sinterability and flowability of the produced powder. However, no study has been made to systematically compare raw and granulated powders in terms of their flowing and sintering behaviors. This paper aims at filling this knowledge gap. Two raw powders (i.e., fine raw powder of 300 nm and coarse raw powder of 70 μm) and one granulated powder from spray freeze drying were compared. Different flowability metrics, including volumetric flow rate, mass flow rate, Hausner ratio, Carr index, and repose angle were measured. Different sinterability metrics, including sintered bulk density, volume shrinkage, and densification ratio were compared for all three powders. Results show that granulated powder achieved comparably high flowability to that of the coarse raw powder and also comparably high sinterability to that of the fine raw powder. Moreover, suitable metrics for the characterization of the sinterability and flowability for these three powders are recommended. This study suggests spray freeze drying produces high-quality feedstock powder for binder jetting process.

Keywords

Additive manufacturing, Binders (Materials), Ceramics, Drying, Feedstock, Flow (Dynamics), Sprays, Density, Materials preparation, Shrinkage (Materials), Sintering

Binder Jetting Additive Manufacturing of Ceramics: Feedstock Powder Preparation by Spray Freeze Granulation

Binder Jetting Additive Manufacturing of Ceramics: Feedstock Powder Preparation by Spray Freeze Granulation

Wenchao Du, Guanxiong Miao, Lianlian Liu, Zhijian Pei

Abstract

Objective of this study is to prepare the binder jetting feedstock powder by spray freeze drying and study the effects of its parameters on the powder properties. Binder jetting additive manufacturing is a promising technology for fabricating ceramic parts with complex or customized geometries. However, this process is limited by the relatively low density of the fabricated parts even after sintering. The main cause comes from the contradicting requirements of the particle size of the feedstock powder: a large particle size (> 5 μm) is required for a high flowability while a small particle size (< 1 μm) for a high sinterability. For the first time, a novel technology for the feedstock material preparation, called spray freeze drying, is investigated to address this contradiction. Using raw alumina nanopowder (100 nm), a full factorial design at two levels for two factors (spraying pressure and slurry feed rate) was formed to study their effects on the properties (i.e., granule size, flowability, and sinterability) of the obtained granulated powder. Results show that high pressure and small feed rate lead to small granule size. Compared with the raw powder, the flowability of the granulated powders was significantly increased, and the high sinterability was also maintained. This study proves that spray freeze granulation is a promising technology for the feedstock powder preparation of binder jetting additive manufacturing.

Inhalable liposomal powder formulations for co-delivery of synergistic ciprofloxacin and colistin against multi-drug resistant gram-negative lung infections

Inhalable liposomal powder formulations for co-delivery of synergistic ciprofloxacin and colistin against multi-drug resistant gram-negative lung infections

Shihui Yu, Shaoning Wang, Peizhi Zou, Guihong Chai, Yu-Wei Lin, Tony Velkov, Jian Li, Weisan Pan, Qi Tony Zhou

Abstract

The aim of this study was to design and characterize dry powder inhaler formulations of ciprofloxacin and colistin co-loaded liposomes prepared by the ultrasonic spray-freeze-drying (USFD) technique. Liposomal formulations and powder production parameters were optimized to achieve optimal characteristics and in-vitro performance such as encapsulation efficiency (EE), particle size, particle distribution index (PDI), fine particle fraction (FPF), emitted dose (ED) and in vitro antibacterial activity. The formulation (F6) with the mannitol (5% w/v) as the internal lyoprotectant and sucrose (5%, w/v), mannitol (10%, w/v) and leucine (5%, w/w) as the external lyoprotectants/aerosolization enhancers showed an optimal rehydrated EE values of ciprofloxacin and colistin (44.9 ± 0.9% and 47.0 ± 0.6%, respectively) as well as satisfactory aerosol performance (FPF: 45.8 ± 2.2% and 43.6 ± 1.6%, respectively; ED: 97.0 ± 0.5% and 95.0 ± 0.6%, respectively). For the blank liposomes, there was almost no inhibitory effect on the cell proliferation in human lung epithelial A549 cells, showing that the lipid materials used in the liposome formulation is safe for use in pulmonary drug delivery. The cytotoxicity study demonstrated that the optimized liposomal formulation (F6) was not cytotoxic at least at the drug concentrations of colistin 5 μg/mL and ciprofloxacin 20 μg/mL. Colistin (2 mg/L) monotherapy showed no antibacterial effect against P. aeruginosa H131300444 and H133880624. Ciprofloxacin (8 mg/L) monotherapy showed moderate bacterial killing for both clinical isolates; however, regrowth was observed in 6 h for P. aeruginosa H133880624. The liposomal formulation displayed superior antibacterial activity against clinical isolates of Pseudomonas aeruginosa H131300444 and P. aeruginosa H133880624 compared to each antibiotic per se. These results demonstrate that the liposomal powder formulation prepared by USFD could potentially be a pulmonary delivery system for antibiotic combination to treat multi-drug resistant Gram-negative lung infections.

Keywords

Ciprofloxacin, Colistin, Liposome, Dry powder inhaler, Ultrasonic spray-freeze-drying, Antimicrobial activity, Aerosol performance

Naked pDNA/hyaluronic acid powder shows excellent long-term storage stability and gene expression in murine lungs

Naked pDNA/hyaluronic acid powder shows excellent long-term storage stability and gene expression in murine lungs

Takaaki Ito, Maino Fukuhara, Tomoyuki Okuda, Hirokazu Okamoto

Abstract

We evaluated the storage stability of powder containing naked plasmid DNA (pDNA) and hyaluronic acid (HA) or mannitol (Man) prepared by the spray-freeze-drying technique, through which we have reported high gene expression without any gene vectors. The powders composed of 5–10-µm porous particles and showing excellent dispersion were stored for 12 months under three storage conditions: 5 °C/Dry, 25 °C/Dry, and 25 °C/75% relative humidity. The humidified powders lost their porous shape within 1 week and were not suitable for inhalation characterization. On the other hand, the powders under dry conditions maintained high inhalation characteristics and pDNA integrity for 12 months. We administered the powders to the lungs of mice. The naked pDNA in HA powder showed significantly higher gene expression compared with that in Man powder and a pDNA-polyethylenimine complex solution. The gene expression of pDNA/HA powder was maintained for 12 months. These results suggest that powder containing naked pDNA is stable on storing under appropriate dry conditions and the naked pDNA/HA powder shows effective pulmonary gene expression.

Keywords

Plasmid DNA, Inhalation, Spray freeze-drying, Pulmonary drug delivery, Lung drug delivery, Gene delivery, Gene therapy

Effects of liquid nitrogen quick freezing on polyphenol oxidase and peroxide activities, cell water states and epidermal microstructure of wolfberry

Effects of liquid nitrogen quick freezing on polyphenol oxidase and peroxide activities, cell water states and epidermal microstructure of wolfberry

ZhiweiZhu, Wenhuang Lou, Da-Wen Sun

Abstract

Fresh wolfberry has a very short shelf-life and drying is the most common method for preserving wolfberry. For better retention of the quality and nutritional values of wolfberry, effects of liquid nitrogen spray freezing at different temperatures of −60 °C ± 2 °C (NF-60°C), −80 °C ± 2 °C (NF-80°C) and −100 °C ± 2 °C (NF-100°C) on wolfberry were investigated, as compared with air-blast freezing (BF) at −40 °C ± 1 °C and air velocity of 0.75 m/s. Results showed that the freezing time passing the maximum ice crystal formation zone were 450 s, 150 s, 100 s and 70 s for BF, NF-60°C, NF-80°C, and NF-100°C, respectively. Comparing with NF-100°C, NF-80°C samples showed better appearance, lower peroxidase activity, water distribution more similar to fresh samples and lower damage of inner epidermal cell structure. The current study suggested that the freezing characteristics of wolfberry did not become better at the ultralow freezing temperature of −100 °C, and NF-80°C was considered the most appropriate freezing process for the freezing characteristics of the wolfberry. It is hoped that the current results could be useful to the industry for better preserving wolfberry.

Keywords

Wolfberry, Liquid nitrogen quick freezing, Water distribution, Epidermal structure, Freezing characteristics

Effective mRNA pulmonary delivery by dry powder formulation of PEGylated synthetic KL4 peptide

Effective mRNA pulmonary delivery by dry powder formulation of PEGylated synthetic KL4 peptide

Abstract

Pulmonary delivery of messenger RNA (mRNA) has considerable potential as therapy or vaccine for a range of lung diseases. Inhaled dry powder formulation of mRNA is particularly attractive as it has superior stability and dry powder inhaler is relatively easy to use. A safe and effective mRNA delivery vector as well as a suitable particle engineering method are required to produce a dry powder formulation that is respirable and mediates robust transfection in the lung. Here, we introduce a novel RNA delivery vector, PEG12KL4, in which the synthetic cationic KL4 peptide is attached to a monodisperse linear PEG of 12-mers. The PEG12KL4 formed nano-sized complexes with mRNA at 10:1 ratio (w/w) and mediated effective transfection on human lung epithelial cells. PEG12KL4/mRNA complexes were successfully formulated into dry powder by spray drying (SD) and spray freeze drying (SFD) techniques. Both SD and SFD powder exhibited satisfactory aerosol properties for inhalation. More importantly, the biological activity of the PEG12KL4 /mRNA complexes were successfully preserved after drying. Using luciferase mRNA, the intratracheal administration of the liquid or powder aerosol of PEG12KL4 /mRNA complexes at a dose of 5 μg mRNA resulted in luciferase expression in the deep lung region of mice 24 h post-transfection. The transfection efficiency was superior to naked mRNA or lipoplexes (Lipofectamine 2000), in which luciferase expression was weaker and restricted to the tracheal region only. There was no sign of inflammatory response or toxicity of the PEG12KL4 /mRNA complexes after single intratracheal administration. Overall, PEG12KL4 is an excellent mRNA transfection agent for pulmonary delivery. This is also the first study that successfully demonstrates the preparation of inhalable dry powder mRNA formulations with in vivo transfection efficiency, showing the great promise of PEG12KL4 peptide as a mRNA delivery vector candidate for clinical applications.

Keywords

Inhalation, mRNA transfection, PEGylation, Peptide, Spray drying, Spray freeze drying

Effect of Particle Formation Process on Characteristics and Aerosol Performance of Respirable Protein Powders.

Effect of Particle Formation Process on Characteristics and Aerosol Performance of Respirable Protein Powders

Brunaugh AD, Wu T, Kanapuram SR, Smyth HDC

Abstract

Pulmonary delivery of biopharmaceuticals may enable targeted local therapeutic effect and noninvasive systemic administration. Dry powder inhaler (DPI) delivery is an established patient-friendly approach for delivering large molecules to the lungs; however, the complexities of balancing protein stability with aerosol performance require that the design space of biopharmaceutical DPI formulations is rigorously explored. Utilizing four rationally selected formulations obtained using identical atomization conditions, an extensive study of the effect of the particle formation process (spray drying or spray freeze-drying) on powder properties, aerosol performance, and protein stability was performed. Multiple linear regression analysis was used to understand the relationship between powder properties, device dispersion mechanism, and aerosol performance. Spray drying and spray freeze-drying, despite the same spraying conditions, produced powders with vastly different physical characteristics, though similar aerosol performance. The resulting regression model points to the significance of particle size, density, and surface properties on the resulting aerosol performance, with these factors weighing differently according to the device dispersion mechanism utilized (shear-based or impaction-based). The physical properties of the produced spray dried and spray freeze-dried powders have differing implications for long-term stability, which will be explored extensively in a future study.

Keywords

Biopharmaceutical; dispersibility; particle engineering; pulmonary drug delivery; spray drying; spray freeze-drying

A spray freeze dried micropellet based formulation proof-of-concept for a yellow fever vaccine candidate

A spray freeze dried micropellet based formulation proof-of-concept for a yellow fever vaccine candidate

Clénet D, Hourquet V, Woinet B, Ponceblanc H, Vangelisti M

Abstract

The stability of live-attenuated viruses is very challenging due to thermal sensitivity; therefore, solid form is usually required (often freeze-dried products). Micropellet technology is a lyophilization technology that has the potential to provide greater flexibility in the presentation of a given vaccine particularly in multi-dose format or in combination of different vaccines. As a novel vaccine alternative process, this spray freeze-dried (SFD) micropellet technology was evaluated using as a model a yellow fever virus produced in Vero cells (vYF). Screening of excipients was performed in order to optimize physico-chemical properties of the micropellets. Sugar/polymer-based formulations induced high glass transition temperature (Tg), adequate breaking force and attrition resistance of the SFD micropellets. These mechanical parameters and their stability are of considerable importance for the storage, the transport but also the filling process of the SFD micropellets. By adding excipients required to best preserve virus infectivity, an optimal sugar/polymer-based formulation was selected to build micropellets containing vYF. Monodisperse and dried micropellets with a diameter of about 530 µm were obtained, exhibiting similar potency to conventional freeze-dried product in terms of vYF infectious titer when both solid forms were kept under refrigerated conditions (2-8°C). Comparable kinetics of degradation were observed for vYF formulated in micropellets or as conventional freeze-dried product during an accelerated stability study using incubations at 25°C and 37°C over several weeks. The results from this investigation demonstrate the ability to formulate live-attenuated viruses in micropellets. Pharmaceutical applications of this novel vaccine solid form are discussed.

Keywords

Micropellets; formulation screening; freeze-drying; live-attenuated vaccine stability

Microwave heating synthesis and luminescence of NaY(WO4)2:(Ho3+, Yb3+) phosphors

Microwave heating synthesis and luminescence of NaY(WO4)2:(Ho3+, Yb3+) phosphors

Yang Yang, Hao Feng, Xiuguo Zhang

Abstract

NaY(WO4)(2):(Ho3+, Yb3+) phosphors were synthesized by microwave heating in an EDTA-mediated process. The samples were characterized by XRD, FT-IR, SEM, and fluorescence spectrophotometer. The XRD and FT-IR results show that the samples have the tetragonal phase. The SEM results show that obtained samples have octahedral morphology. ‘Oriented attachment’ and ‘Ostwald ripening’ play key roles in the formation of octahedrons. The UC emission spectra of NaY(WO4)(2):(Ho3+, Yb3+) phosphors under 980 nm excitation show two intense bands corresponding to F-5(4) + S-5(2) -> I-5(8) and F-5(5) -> I-5(8) transitions of Ho3+ ions. Based on the energy level diagrams of Yb3+ and Ho3+, as well as the results of power dependence of UC emission intensities, possible excitation path ways for different bands are deduced. The green and red UC emissions of NaY(WO4)(2):(Ho3+, Yb3+) phosphors originate from the two-photon process. Also, the samples have good thermal stability.

Preparation and characterization of nano amitriptyline hydrochloride particles by spray freeze drying

Preparation and characterization of nano amitriptyline hydrochloride particles by spray freeze drying

Hu Y, Ma C, Sun M, Guo C, Shen J, Wang J, Nie F, Gao B.

Abstract

Aim: To investigate the enhancement of bioavailability by the usage of drug nanoparticles for increasing the efficacy of antidepressant therapeutic value. Materials & methods: Nano-amitriptyline HCI (AMT·HCl) particles were successfully prepared via a simple spray freeze drying (SFD) method.

Results: The as-prepared nanoparticles are amorphous instead of crystalline. The mean size of AMT·HCl nanoparticles is 90 nm. In in vitro evaluation, AMT·HCl nanoparticles have greatly improved the dissolution compared with pure bulk materials, which have potential for enhancing human bioavailability and diminishing toxic effect. A nanoparticle formation mechanism was also proposed.

Conclusion: These findings promote the development of antidepressant therapeutic evaluation based on the usage of AMT·HCl nanoparticles by SFD method and indicate that SFD is an alternative for a range of nanoparticle preparation in industrial pharmacy.

Keywords

evaluation; amitriptyline hydrochloride; antidepressants; bioavailability; nanocrystals; spray freeze drying