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Selectivity of Ru-rich Ru-Ti-O oxide surfaces in parallel oxygen and chlorine evolution reactions

Kateřina Minhová Macounová, Rebecca Katharina Pittkowski, Roman Nebel, Andrea Zitolo, Petr Krtil

Abstract

The electrocatalytic behaviour of single-phase Ru_1-xTi_xO₂ materials was studied to outline general trends controlling the selectivity of oxide-based anodes in parallel oxygen evolution and chlorine evolution reactions. Materials with x ranging between 0 and 0.2 were prepared by spray freeze freeze drying approach. Prepared materials show a non-homogeneous distribution of Ti in the structure with dominant clustering of the Ti along the (001) direction. For materials with x higher than 0.1 the dominant linear clustering of Ti along the z-axis changes, including Ti clustering also along (111) direction. Prepared materials are active in both oxygen evolution and chlorine evolution reactions. The Ti has a pronounced effect on the selectivity of the prepared materials. Ti presence affects the selectivity of the prepared materials in a complex manner. Materials featuring a low Ti content (x∼0.05) retain a preference for oxygen evolution reaction even in presence of chlorides and are more selective for oxygen evolution than pure RuO₂. The selectivity towards chlorine evolution increases with increasing Ti content and, apparently, also with clustering of Ti along the (111) direction. The selectivity towards chlorine evolution may be related to the tendency of the prepared catalysts to evolve the oxygen via lattice oxygen evolution reaction (LOER) reflecting the ability of the catalyst surface to form active sites under operando conditions.

Keywords

Ru-Ti-O oxides, oxygen evolution, chlorine evolution, selectivity, local structure

Effects of drying methods on physical properties and morphology of trehalose/mannitol mixtures

Daniel Tristan Osanlóo, Jonas Fransson, Björn Bergenståhl, Anna Millqvist-Fureby

Abstract

Solid-state properties of dried protein formulations are important for stability and functionality of the product. This study investigates how different drying technologies (freeze-drying with and without annealing, spray drying and spray-freeze drying) affect the structure and solid-state properties of a set of matrix formulations composed of trehalose (glass former) and mannitol (scaffolding agent) in five ratios. The dried materials were characterized using differential scanning calorimetry, thermogravimetric analysis, x-ray diffraction and scanning electron microscopy. The morphology of the dried matrix is determined by the drying technology and the composition. In all mixtures, mannitol partially dissolved in the amorphous trehalose, resulting in reduced glass transition temperature. At least 50% mannitol is required to achieve a scaffolding effect through crystallized mannitol. At 25% mannitol poor structural stability is obtained regardless of drying technology. Despite the vast differences in drying kinetics, all drying technologies resulted in similar amorphous content in the dried material.

Keywords

Freeze-drying, spray-freeze drying, spray drying, scaffolding, morphology, solid-state

Micro-fluidic Spray Freeze Dried Ciprofloxacin Hydrochloride-Embedded Dry Powder for Inhalation

Yingjie Chen, Shen Yan, Shengyu Zhang, Quanyi Yin, Xiao Dong Chen, Winston Duo Wu

Abstract

Active pharmaceutical ingredient (API)-embedded dry powder for inhalation (AeDPI) is highly desirable for pulmonary delivery of high-dose drug. Herein, a series of spray freeze-dried (SFD) ciprofloxacin hydrochloride (CH)-embedded dry powders were fabricated via a self-designed micro-fluidic spray freeze tower (MFSFT) capable of tuning freezing temperature of cooling air as the refrigerant medium. The effects of total solid content (TSC), mass ratio of CH to L-leucine (Leu) as the aerosol dispersion enhancer, and the freezing temperature on particle morphology, size, density, moisture content, crystal properties, flowability, and aerodynamic performance were investigated. It was found that the Leu content and freezing temperature had considerable influence on the fine particle fraction (FPF) of the SFD microparticles. The optimal formulation (CH/Leu = 7:3, TSC = 2%w/w) prepared at – 40°C exhibited remarkable effective drug deposition (~ 33.38%), good aerodynamic performance (~ 47.69% FPF), and excellent storage stability with ultralow hygroscopicity (~ 1.93%). This work demonstrated the promising feasibility of using the MFSFT instead of conventional liquid nitrogen assisted method in the research and development of high-dose AeDPI.

Keywords

Active pharmaceutical ingredient-embedded dry powder for inhalation (AeDPI), Spray freeze drying, Adjustable freezing temperature, Porous and brittle microparticle, High fine particle fraction

Solid state of inhalable high dose powders

Bishal Raj Adhikari, Keith C. Gordon, Shyamal C. Das

Abstract

High dose inhaled powders have received increased attention for treating lung infections. These powders can be prepared using techniques such as spray drying, spray-freeze drying, crystallization, and milling. The selected preparation technique is known to influence the solid state of the powders, which in turn can potentially modulate aerosolization and aerosolization stability. This review focuses on how and to what extent the change in solid state of high dose powders can influence aerosolization. It also discusses the commonly used solid state characterization techniques and the application of potential strategies to improve the physical and chemical stability of the amorphous powders for high dose delivery.

Keywords

Aerosolization, Amorphous, Antibiotic, Chemical stability, Co-amorphous, Crystalline, Dry powder inhaler, Lung infection, Pulmonary drug delivery

Effect of spray freeze drying on the structural modification and rehydration characteristics of micellar casein powders

Jinbo Ren, Minjie Liao, Lingjun Ma, Fang Chen, Xiaojun Liao, Xiaosong Hu, Song Miao, John Fitzpatrick, Junfu Ji

Abstract

Micellar casein (MC) is usually spray-dried into powder form for transportation and storage. However, the micellar structure maintained by colloidal calcium phosphate (CCP) and hydrophobic forces leads to poor rehydration ability of MC powders, which limits its potential applications. Here, spray freeze drying (SFD) with controlled droplet size was used to produce MC powders. Their effects on the structure of MC and the subsequent rehydration characteristics including wetting, dispersion and dissolution were investigated. The results showed SFD powders obtained from smaller droplet size caused more than 50% of serum Ca²⁺ and PO₄³⁻ to release from the micellar structure. These powder particles exhibited extremely high porosity (92%) and spherical morphology, which thus greatly shortened their wetting time. Furthermore, the smallest droplets during SFD were believed to produce the MC powders with the quickest dispersion and best solubility, as over 80% of the solids could be completely dissolved in just 15 min.

Keywords

Micellar casein (MC), Spray freeze drying (SFD), Droplet size, Rehydration behaviors, Colloidal calcium phosphate (CCP)

Ointment containing spray freeze-dried metronidazole effective against rosacea

Klára Szentmihályi, Krisztina Móricz, Gábor Gigler, Zoltán May, Eszter Bódis, Judit Tóth, Mónika Bakonyi, Szilvia Klébert, Tivadar Feczkó, Zoltán Károly

Abstract

Rosacea is a chronic, inflammatory skin disease that affects about 10% of the population. Metronidazole-containing ointments are typically recommended for the daily treatment of symptoms. For increasing bioavailability and effectiveness, it is needed to reduce the particle size. Therefore, micronized metronidazole was prepared by spray freeze-drying (SFD) method, then its most important features were examined such as morphology, crystallinity and particle size. The anti-inflammatory effect of the as-prepared agent was tested on a mouse model of rosacea for effectiveness against oedema and redness of the ears, and it was compared to a reference cream.

Metronidazole size was reduced successfully by SFD to 2.7 μm from 162.6 μm. The material was non-porous and preserved its crystalline state. The spray freeze-dried metronidazole mixed into ointment was effective against oedema and ear-redness. The ointment reduced oedema in five times lower doses (2 × 0.04 mg metronidazole) and the ear-redness in half dose (2 × 0.2 mg metronidazole) than the cream containing reference metronidazole (2 × 0.2 mg and 2 × 0.4 mg metronidazole, respectively). In conclusion, the SFD technique is an adequate and gentle procedure for reducing the size of metronidazole, which is highly effective in rosacea.

Keywords

Rosacea, Metronidazole, Spray freeze-drying, Particle size, Mouse, Oedema

Microencapsulation of High-Content Actives Using Biodegradable Silk Materials

Muchun Liu, Pierre-Eric Millard, Henning Urch, Ophelie Zeyons, Douglas Findley, Rupert Konradi, Benedetto Marelli

Abstract

There is a compelling need across several industries to substitute non-degradable, intentionally added microplastics with biodegradable alternatives. Nonetheless, stringent performance criteria in actives’ controlled release and manufacturing at scale of emerging materials hinder the replacement of polymers used for microplastics fabrication with circular ones. Here, the authors demonstrate that active microencapsulation in a structural protein such as silk fibroin can be achieved by modulating protein protonation and chain relaxation at the point of material assembly. Silk fibroin micelles’ size is tuned from several to hundreds of nanometers, enabling the manufac-turing—by retrofitting spray drying and spray freeze drying techniques—of micro capsules with tunable morphology and structure, that is, hollow-spongy, hollow-smooth, hollow crumpled matrices, and hollow crumpled multi-domain. Microcapsules degradation kinetics and sustained release of soluble and insoluble payloads typically used in cosmetic and agriculture applications are controlled by modulating fibroin’s beta-sheet content from 20% to near 40%. Ultraviolet-visible studies indicate that burst release of a commonly used herbicide (i.e., saflufenacil) significantly decreases from 25% to 0.8% via silk fibroin microencapsulation. As a proof-of-concept for agrochemicals applications, a 6-day greenhouse trial demonstrates that saflufenacil delivered on corn plants via silk microcapsules reduces crop injury when compared to the non-encapsulated version.

Keywords

Agrochemicals, controlled release, microcapsules, microplastics, vitamin c, silk

Spray freeze drying of dairy products: Effect of formulation on dispersibility

Alberto Baldelli, Hale Oguzlu, Diana Yumeng Liang, Alison Subiantoro, Meng Wai Woo, Anubhav Pratap-Singh

Abstract

Milk powders are commonly produced by using the technique of spray drying. In this work, we propose the use of spray freeze drying technology to improve the re-dispersibility of milk powders in aqueous systems. We explore how formulation can influence the re-dispersibility of dairy products. Due to higher porosity and lower tapped density, milk powder produced by spray freeze drying showed an average 15% percentage higher re-dispersibility than spray-dried powders after only 20 s of agitation. Higher fat percentages and the presence of an additive, maltodextrin, worsened the re-dispersibility of spray freeze-dried dairy powders. An increase in 6% of fat percentage decreased the percentage of redissolved powder by 30%. Similarly, an increase in 5% maltodextrin weight resulted in a 5% lower re-dispersibility. The results of this study shall be fundamental in providing future guidelines for the use of spray freeze drying technique for producing milk and other dairy powders with high quality and nutrient retention.

Keywords

Spray freeze drying, Particle formation, Milk powder, Redispersibility

Spray Freezing Coating on the Carrier Particles for Powder Preparation

Qing Xu, Ruixin Wang, Fan Zhang, Ruifang Wang, Long Wu, Bo Lin

Abstract

Carrier particle spray freeze-drying is a new technology with high added value for thermosensitive powder spray freeze-drying. The technology includes the following steps: atomization, coating, freezing, and drying. Due to the action of carrier particles, the condensation of frozen droplets in the conventional spray freeze-drying process is overcome. However, there are many influencing factors involved in the process of freezing coating. The mechanism of the complex droplet collision freezing process still needs to be studied. In this paper, from the perspective of spray freezing coating after atomized droplets collide with low-temperature carrier particles, the coating process and freezing process of single droplets impacting the sphere are analyzed microscopically. The freezing coating processes of static and dynamic carrier particles are reviewed. Moreover, the surface evaluation of powder and equipment development for creating powder products is discussed.

Keywords

spray freezing coating, carrier particles, drying, powder characteristics, integrated equipment

Debate: Nanoparticles – a blessing or a curse?

Hans Leuenberger

Abstract

This chapter was inspired by Ilya Prigogine (Nobel laureate 1977) and by six axioms derived1 earlier, such as A1, Far from equilibrium conditions, favoring transformations from disorder into order leading to the creation of life, and A5 and 6, The evolutionary process uses all existing physical laws of the present standard cosmological model and beyond to find a niche for a successful survival of the biological system being complemented by A7, Nature’s principle of self-similarity, A8, Bionic inspired philosophical solutions, and most important by A9, The human society is a living biological system. Thus, life of a society is governed by the same laws as for a human being. From a global point of view, society’s life depends on system relevant organs such as brain (pool of scientists), heart (system of banks) pumping blood (money) to the muscles (industry), to the lungs (combustion engines), and to the digestive system (recycling industry). As in case of a human being, the society’s health, life, and death depend on framework conditions such as technologies improving quality of life. For this reason, an innovative spray-freeze drying process is presented, allowing manufacturing nanocomposite pellets for nanomedicine. The chapter shows that this technological solution based on scientific integrity is not sufficient for securing the public acceptance. It is necessary to respect religion and ethics, business ethics, legal framework, and to complement the nine axioms by A10, Common denominator of all Religions = Ethical Codex, by A11, Common denominator of Marketing and Politics = Trustworthy Communication and by A12, Common denominator of all Trustworthy Sciences = Scientific Integrity. In conclusion, the chapter defines rigorous prerequisites for public acceptance of nanotechnology and beyond, such as science diplomacy for the survival of mankind.