This paper reviews the advances in nanoparticle spray drying performed in a laboratory environment and with the Nano Spray Dryer B-90, which was introduced by BUCHI Labortechnik AG in 2009. Special ...regard will be paid to relevant published works. The technological novelty of the patented Nano Spray Dryer B-90 lies in the gentle laminar drying flow, the vibrating mesh spray technology, and the highly efficient electrostatic particle collector.
Recent studies prove the successful use of this spray dryer for a variety of drug delivery applications, such as poorly soluble drugs (e.g., griseofulvin, furosemide), enzymes (e.g., galactosidase), proteins (bovine serum albumin, whey protein), amino acids (e.g., leucine), polysaccharides (e.g., trehalose, lactose), salts, encapsulation of nano-emulsions in polymeric wall materials, as well as materials science applications (e.g., battery-grade lithium carbonate).
The Nano Spray Dryer B-90 makes it possible to produce spray-dried particles in the submicron scale and to create tiny particles of down to only 350-500 nm. In contrast to traditional laboratory-scale spray dryers, it can achieve uniquely high yields of up to 94% for powder amounts down to the milligram scale (e.g., 3.0-500 mg).
Process parameters and formulation variables for a nano spray dryer.
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Many pharmaceuticals such as pills, capsules, or tablets are prepared in a dried and powdered form. In this field, ...spray drying plays a critical role to convert liquid pharmaceutical formulations into powders. In addition, in many cases it is necessary to encapsulate bioactive drugs into wall materials to protect them against harsh process and environmental conditions, as well as to deliver the drug to the right place and at the correct time within the body. Thus, spray drying is a common process used for encapsulation of pharmaceuticals. In view of the rapid progress of nanoencapsulation techniques in pharmaceutics, nano spray drying is used to improve drug formulation and delivery. The nano spray dryer developed in the recent years provides ultrafine powders at nanoscale and high product yields. In this paper, after explaining the concept of nano spray drying and understanding the key elements of the equipment, the influence of the process parameters on the final powders properties, like particle size, morphology, encapsulation efficiency, drug loading and release, will be discussed. Then, numerous application examples are reviewed for nano spray drying and encapsulation of various drugs in the early stages of product development along with a brief overview of the obtained results and characterization techniques.
This study reviews the current state of the art and the current research activities of high temperature heat pumps (HTHPs) with heat sink temperatures in the range of 90 to 160 °C. The focus is on ...the analysis of the heat pump cycles and the suitable refrigerants. More than 20 HTHPs from 13 manufacturers have been identified on the market that are able to provide heat sink temperatures of at least 90 °C. Large application potentials have been recognized particularly in the food, paper, metal and chemical industries. The heating capacities range from about 20 kW to 20 MW. Most cycles are single-stage and differ primarily in the refrigerant (e.g. R245fa, R717, R744, R134a or R1234ze(E)) and compressor type used. The COPs range from 2.4 to 5.8 at a temperature lift of 95 to 40 K. Several research projects push the limits of the achievable COPs and heat sink temperatures to higher levels. COPs of about 5.7 to 6.5 (at 30 K lift) and 2.2 and 2.8 (70 K) are achieved at a sink temperature of 120 °C. The refrigerants investigated are mainly R1336mzz(Z), R718, R245fa, R1234ze(Z), R600, and R601. R1336mzz(Z) enables to achieve exceptionally high heat sink temperatures of up to 160 °C.
•Comprehensive market overview of high temperature heat pumps.•Discussion of the current state of research of high temperature heat pumps.•Analysis of heat pump cycles and comparison of performance.•Selection of suitable refrigerants for high temperature heat pumps.•Identification of research potentials of high temperature heat pumps.
Background
Spray drying is a relatively simple, fast, reproducible and scalable drying technology that is suitable for drying heat-sensitive biopharmaceutical compounds. In view of the rapid progress ...of nanoencapsulation technologies in the pharmaceutical sector, nano spray drying is used in research to improve the powder formulation and release of active ingredients. The Nano Spray Dryer B-90 of the Swiss company Büchi Labortechnik AG extends the size of the powder particles produced into the nanometer scale with narrow size distributions and high encapsulation efficiency.
Area covered
This study explains the special nano spray drying technology and discusses the influence of the respective process parameters on the powder properties. Applications of nano spray drying for the formulation and encapsulation of active ingredients in PLA/PLGA biopolymers are investigated and discussed. Optimized process parameters for the application of nano spray drying of similar substances are presented.
Expert opinion
The analyzed studies show the possibility of producing PLGA particles from approx. 2 μm to below 200 nm by nano spray drying, as well as the encapsulation of various active ingredients in spherical particles and nano-in-nanoparticle composite structures made of PLGA polymers for controlled drug delivery systems. The researched applications are primarily in the therapeutic field, such as the treatment of inhalation diseases, inflammations, cancer, immune diseases, genetic disorders, the regulation of vasodilatation or the surface coating of medical implants with biocompatible PLGA nanoparticles.
Spray drying technology is widely known and used to transform liquids (solutions, emulsions, suspension, slurries, pastes or even melts) into solid powders. Its main applications are found in the ...food, chemical and materials industries to enhance ingredient conservation, particle properties, powder handling and storage etc. However, spray drying can also be used for specific applications in the formulation of pharmaceuticals for drug delivery (
e.g. particles for pulmonary delivery). Büchi is a reference in the development of spray drying technology, notably for laboratory scale devices. This study presents the Nano Spray Dryer B-90, a revolutionary new sprayer developed by Büchi, use of which can lower the size of the produced dried particles by an order of magnitude attaining submicron sizes. In this paper, results are presented with a panel of five representative polymeric wall materials (arabic gum, whey protein, polyvinyl alcohol, modified starch, and maltodextrin) and the potentials to encapsulate nano-emulsions, or to formulate nano-crystals (
e.g. from furosemide) are also shown.
This review provides a comprehensive overview of scientific research on plasma treatment of polymer powders over the last 40 years. The current state of the art is described with special focus on ...basic research in the laboratory and commercially available technologies in industrial applications. Different reactor systems with low‐pressure and atmospheric pressure plasma are presented. Then, numerous application examples of plasma‐treated polymer powders are presented together with a brief overview of the experimental test results. Furthermore, the effects of the process parameters on the final properties of the polymer powders are discussed. Attempts are made to determine similarity parameters and correlations between the generated surface functionalities. Finally, some suggestions for future research are given.
This review provides a comprehensive overview of scientific research on plasma treatment of polymer powders over the last 40 years. The current state of the art is described with special focus on laboratory research and industrial applications. Different reactor systems are presented together with numerous application examples. The effects of the process parameters on the final properties of the polymer powders are discussed. Some suggestions for future research are given.
Nanoparticle engineering of water insoluble active substances using a novel piezoelectric spray-drying process.
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► Nano and micro particle engineering using a piezoelectric spray ...drying methodology. ► The spray-drying processing parameters control the size of the obtained particles. ► The drug/polymer ratio and the solvent mixtures play a key role on obtained particle size. ► The produced particles present spherical shape, narrow particle size distribution and porous surface. ► CyA is molecularly dispersed within the PLGA particles while DEX is in crystalline state.
In the current study nano and microparticle engineering of water insoluble drugs was conducted using a novel piezoelectric spray-drying approach. Cyclosporin A (CyA) and dexamethasone (DEX) were encapsulated in biodegradable poly(
d,
l-lactide-co-glycolide) (PLGA) grades of different molecular weights. Spray-drying studies carried out with the Nano Spray Dryer B-90 employed with piezoelectric driven actuator. The processing parameters including inlet temperature, spray mesh diameter, sample flow rate, spray rate, applied pressure and sample concentration were examined in order to optimize the particle size and the obtained yield. The process parameters and the solute concentration showed a profound effect on the particle engineering and the obtained product yield. The produced powder presented consistent and reproducible spherical particles with narrow particle size distribution. Cyclosporin was found to be molecularly dispersed while dexamethasone was in crystalline state within the PLGA nanoparticles. Further evaluation revealed excellent drug loading, encapsulation efficiency and production yield. In vitro studies demonstrated sustained release patterns for the active substances. This novel spray-drying process proved to be efficient for nano and microparticle engineering of water insoluble active substances.
The industry is currently responsible for around 21% of the total CO2 emissions, mainly due to heat production with fossil fuel burners. There are already different technologies on the market that ...can potentially reduce CO2 emissions. Nevertheless, the first step for their introduction is to analyze their potential on a global scale by detecting in which countries each of them is more attractive, given their energy prices and resources. The present work involves a techno-economic analysis of different alternatives to replace industrial gas boilers for low-pressure steam production at 120 °C and 150 °C. Solar Heat for Industrial Processes (SHIP) was compared with Electric Boilers (EBs), High-Temperature Heat Pumps (HTHPs), and Absorption Heat Transformers (AHTs). SHIP systems have the potential to reach payback periods in the range of 4 to 5 years in countries with Direct Normal Irradiance (DNI) values above 1400 kWh/m2/year, which is reached in Spain, Italy, Greece, Portugal, and Romania. HTHPs and AHTs lead to the lowest payback periods, Levelized Cost of Heat (LCOH), and highest CO2 emission savings. For both AHTs and HTHPs, payback periods of below 1.5 years can be reached, particularly in countries with electricity-to-gas price ratios below 2.0.
Several theoretical studies have predicted that refrigerant mixtures with glides of more than 20 K can yield COP improvements in heat pumps for operating conditions where the temperature difference ...between the heat source and heat sink is large, but experimental validations and quantifications are scarce. The application of high-glide mixtures (>20 K) in industrial heat pumps in the field is, therefore, still hampered by concerns about the behavior and handling of the mixtures. This study experimentally investigates hydrocarbon (HC) mixtures R-290/600 (propane/butane) and R-290/601 (propane/pentane) and compares them to previously tested mixtures of synthetic refrigerants. Comprehensive evaluations are presented regarding COP, compressor performance, pressure drop, heat transfer, and the possibility of inline composition determination. The mixtures were tested over a range of compositions at a source inlet temperature of 60 °C and a sink outlet temperature of 100 °C, with the heat sink and heat source temperature differences controlled to 35 K. R-290/601 at a mass composition of 70%/30% was found as the best mixture with a COP improvement of 19% over R-600 as the best pure fluid. The overall isentropic compressor efficiency was similar for HC and synthetic refrigerants, given equal suction and discharge pressures. Pressure drops in heat exchangers and connecting lines were equal for synthetic and HC mixtures at equal mass flow rates. This allows higher heating capacities of HC mixtures at a given pressure drop (mass flow rate) due to their wider vapor dome. A previously developed evaporator heat transfer correlation for synthetic refrigerant mixtures was applicable to the HC mixtures. A condenser heat transfer correlation previously fitted for synthetic refrigerants performed significantly worse for HC mixtures. Composition determination during operation and without sampling was possible with a deviation of at most 0.05 mass fraction using simple temperature and pressure measurements and REFPROP for thermodynamic property calculations. Overall, high-glide HC mixtures, just like mixtures of synthetic refrigerants, showed significant COP improvements for specific operating conditions despite a decreased heat transfer coefficient. Potential problems like composition shift or poor compressor performance were not encountered. As a next step, testing high-glide mixtures in pilot-plant installations is recommended.
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