DOCSLIB.ORG

Polymeric Nanoparticles: Production, Characterization, Toxicology and Ecotoxicology

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

molecules Review Polymeric Nanoparticles: Production, Characterization, Toxicology and Ecotoxicology Aleksandra Zieli ´nska 1,2 , Filipa Carreiró 1, Ana M. Oliveira 1, Andreia Neves 1,Bárbara Pires 1, D. Nagasamy Venkatesh 3 , Alessandra Durazzo 4 , Massimo Lucarini 4, Piotr Eder 5 , Amélia M. Silva 6,7 , Antonello Santini 8,* and Eliana B. Souto 1,9,* 1 Department of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba, 3000-548 Coimbra, Portugal; [email protected] (A.Z.); fi[email protected] (F.C.); [email protected] (A.M.O.); [email protected] (A.N.); [email protected] (B.P.) 2 Institute of Human Genetics, Polish Academy of Sciences, Strzeszy´nska32, 60-479 Pozna´n,Poland 3 JSS College of Pharmacy, JSS Academy of Higher Education & Research, Ooty 643 001, Tamil Nadu, India; nagasamyvenkatesh@rediffmail.com 4 CREA-Research Centre for Food and Nutrition, Via Ardeatina 546, 00178 Rome, Italy; [email protected] (A.D.); [email protected] (M.L.) 5 Department of Gastroenterology, Dietetics and Internal Diseases, Poznan University of Medical Sciences, Przybyszewskiego 49, 60–355 Pozna´n,Poland; [email protected] 6 Department of Biology and Environment, University of Tras-os-Montes e Alto Douro, UTAD, Quinta de Prados, 5001-801 Vila Real, Portugal; [email protected] 7 Centre for Research and Technology of Agro-Environmental and Biological Sciences (CITAB-UTAD), Quinta de Prados, 5001-801 Vila Real, Portugal 8 Department of Pharmacy, University of Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy 9 CEB—Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal * Correspondence: [email protected] (A.S.); ebsouto@ff.uc.pt (E.B.S.) Academic Editor: Magnus Willander Received: 8 June 2020; Accepted: 13 August 2020; Published: 15 August 2020 Abstract: Polymeric nanoparticles (NPs) are particles within the size range from 1 to 1000 nm and can be loaded with active compounds entrapped within or surface-adsorbed onto the polymeric core. The term “nanoparticle” stands for both nanocapsules and nanospheres, which are distinguished by the morphological structure. Polymeric NPs have shown great potential for targeted delivery of drugs for the treatment of several diseases. In this review, we discuss the most commonly used methods for the production and characterization of polymeric NPs, the association efficiency of the active compound to the polymeric core, and the in vitro release mechanisms. As the safety of nanoparticles is a high priority, we also discuss the toxicology and ecotoxicology of nanoparticles to humans and to the environment. Keywords: polymeric nanoparticles; nanocapsules; nanospheres; therapeutic potential; targeted drug delivery; toxicology; ecotoxicology. 1. Introduction Polymeric nanoparticles (NPs) have attracted considerable interest over recent years due to their properties resulting from their small size [1–3]. Advantages of polymeric NPs as drug carriers include their potential use for controlled release, the ability to protect drug and other molecules with biological activity against the environment, improve their bioavailability and therapeutic index [1,4]. The term “nanoparticle” comprises both nanocapsules and nanospheres, which differ with respect to their morphology [5]. Nanocapsules are composed of an oily core in which the drug is usually Molecules 2020, 25, 3731; doi:10.3390/molecules25163731 www.mdpi.com/journal/molecules Molecules 2020, 25, 3731 2 of 20 Moleculesdissolved, 2020, 25, surroundedx FOR PEER REVIEW by a polymeric shell which controls the release profile of the drug from2 of the 21 core. Nanospheres are based on a continuous polymeric network in which the drug can be retained inside or core. Nanospheres are based on a continuous polymeric network in which the drug can be retained adsorbed onto their surface [5–7]. These two types of polymeric NPs recognized as a reservoir system inside or adsorbed onto their surface [5–7]. These two types of polymeric NPs recognized as a (nanocapsule), and matrix system (nanosphere) [8] are shown in Figure1. Examples of drugs /bioactive reservoir system (nanocapsule), and matrix system (nanosphere) [8] are shown in Figure 1. ingredients loaded in polymeric nanoparticles are depicted in Table1. Examples of drugs/bioactive ingredients loaded in polymeric nanoparticles are depicted in Table 1. Figure 1. Schematic representation of the structure of nanocapsules and nanospheres (arrow stands for Figurethe 1. presence Schematic of drugrepresentation/bioactive withinof the structure the nanoparticles). of nanocapsules and nanospheres (arrow stands for the presence of drug/bioactive within the nanoparticles). Table 1. Examples of drugs/bioactive ingredients loaded in polymeric nanoparticles. Table 1. Examples of drugs/bioactive ingredients loaded in polymeric nanoparticles. Formulated Type of Polymeric Applications Type of Polymers Ref. Drug/Bioactive Nanoparticles/Method Purpose Formulated Type of Polymeric Applications Type of Polymers Ref. Drug/Bioactive Nanoparticles/Methodnanospheres; Purpose C-6-loaded polymeric core-shell nanospheres; NPs (polymeric core-multilayer drug delivery, PCL, PLA, PLGA Coumarin-6 (C-6) C-6-loadedpolyelectrolyte polymeric shell NPs), theranostics, or [9] core-shellobtained NPs by (polymeric prepared by the bioimaging drug delivery, spontaneouscore-multilayer emulsification PCL, PLA, PLGA Coumarin-6 (C-6) theranostics, or [9] polyelectrolytesolvent evaporation shell NPs), method nanospheres; bioimaging PLGA Rapamycin obtainedRapamycin-loaded by prepared polysorbate by anti-glioma activity [10] the80-coated spontaneous PLGA NPs emulsificationnanospheres; solvent Hyperforin-loadednanospheres; AcDex-based NPs formulated via single anti-inflammatory AcDex Hyperforin Rapamycin-loaded [11] PLGA Rapamycin emulsion/solvent anti-gliomaactivity activity [10] polysorbateevaporationusing 80-coated ethyl acetate PLGAand NPs water nanospheres; diabetic retinopathy, neovascular Hyperforin-loadednanospheres; PLGA Fenofibrate (Feno) age-related macular [12] AcDex-basedPLGA-Feno NPs NPs anti-inflammatorydegeneration (ocular AcDex Hyperforin formulated via single neovascularization) [11] activity emulsion/solventnanocapsules; anti-leishmanial Amphotericin B PCL-NCs loaded with Amp B, (Leishmania biopolymer of PCL evaporationusing ethyl [13] (Amp B) obtained by nanoprecipitation infections), acetate andmethod water anti-fungal diabetic retinopathy, neovascular Fenofibrate nanospheres; PLGA age-related macular [12] (Feno) PLGA-Feno NPs degeneration (ocular neovascularization) biopolymer of PCL Amphotericin B nanocapsules; anti-leishmanial [13] Molecules 2020, 25, 3731 3 of 20 Table 1. Cont. Formulated Type of Polymeric Applications Type of Polymers Ref. Drug/Bioactive Nanoparticles/Method Purpose anionic copolymers nanocapsules; based on methacrylic FF-loaded-Eudragit L 100 NCs, undefined oral acic and methyl Fenofibrate (FF) [14] obtained by nanoprecipitation delivery methacrylate (Eudragit method L 100) in situ tissue nanocapsules; regeneration and ciprofloxacin-loaded PLGA NCs, PLGA, PCL Ciprofloxacin accelerated healing, [15] obtained by nanoprecipitation anti-inflammatory method activity nanocapsules; antibacterial activity, PLGA Curcumin (Cur) [16,17] Cur-loaded PLGA NCs pancreatic cancer colloidal nanocapsules; F108: PEG-PPG-PEG Curcumin (Cur) anticancer [18] Cur-loaded PEG-PPG-PEG NCs colloidal nanocapsules; severe combined PEG Pegademase bovine Pegademase bovine-loaded PEG immunodeficiency [17,19] NCs disease lung cancers in nanocapsules; combinationwith PCL-PEG-PCL Paclitaxel (PTX) [20] PTX-loaded PCL-PEG-PCL NCs chrono-modulatedche motherapy breast, pancreatic nanocapsules; PLGA-PEG Paclitaxel (PTX) andovarian and [20] PTX-loaded PLGA-PEG NCs brain cancers Eudragit® RS100, Eudragit® L100-55, EO based-nanoparticles by antioxidant/ Essential Oils [21] Eudragit® EPO, PCL, nanoprecipitation method antimicrobial polylactide, PLGA Cymbopogon martini nanocapsules; antioxidant, PCL [22] Roxb. (Palmarosa oil) Palmarosa oil-loaded PCL NCs antimicrobial nanocapsules; Thymus vulgaris L. Eudragit® L100-55 Thyme oil-loaded Eudragit® antioxidant [23] (Thyme oil) L100-55 NCs nanocapsules; Citrus bergamia Risso. Eudragit® RS100 Bergamot oi-loaded Eudragit® antimicrobial [24] (Bergamot oil) RS100 NCs nanocapsules; Citrus sinensis L. Eudragit® RS100 Orange oil-loaded Eudragit® antimicrobial [24] (Orange oil) RS100 nanocapsules; Rosmarinus officinalis Eudragit® EPO Rosemary oil-loaded Eudragit® antioxidant [25] L. (Rosemary oil) EPO NCs nanocapsules; Lavandula dentata L. Eudragit® EPO Lavender oil-loaded Eudragit® antioxidant [25] (Lavender oil) EPO NCs nanocapsules; antioxidant, PCL Geraniol [22] Geraniol-loaded PCL NCs antimicrobial Abbreviations: AcDex—acetalated dextran; F108—poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide); NCs—nanocapsules; NPs—nanoparticles; PCL—poly("-caprolactone); PEG—poly(ethylene glycol); PLA—poly(lactic acid); PLGA—poly(lactide-co-glycolide). 2. Methods for Production of Polymeric Nanoparticles Depending on the type of drug to be loaded in the polymeric NPs and their requirements for a particular administration route, different methods can be used for the production of the particles [26]. In general, two main strategies are employed, namely, the dispersion of preformed polymers or the polymerization of monomers [27,28]. Table2 lists the most
Recommended publications
  • Mechanical Dispersion of Clay from Soil Into Water: Readily-Dispersed and Spontaneously-Dispersed Clay Ewa A

    Mechanical Dispersion of Clay from Soil Into Water: Readily-Dispersed and Spontaneously-Dispersed Clay Ewa A

    Int. Agrophys., 2015, 29, 31-37 doi: 10.1515/intag-2015-0007 Mechanical dispersion of clay from soil into water: readily-dispersed and spontaneously-dispersed clay Ewa A. Czyż1,2* and Anthony R. Dexter2 1Department of Soil Science, Environmental Chemistry and Hydrology, University of Rzeszów, Zelwerowicza 8b, 35-601 Rzeszów, Poland 2Institute of Soil Science and Plant Cultivation (IUNG-PIB), Czartoryskich 8, 24-100 Puławy, Poland Received July 1, 2014; accepted October 10, 2014 A b s t r a c t. A method for the experimental determination of Clay particles can either flocculate or disperse in aque- the amount of clay dispersed from soil into water is described. The ous solution. When flocculation occurs, the particles com- method was evaluated using soil samples from agricultural fields bine to form larger, compound particles such as soil in 18 locations in Poland. Soil particle size distributions, contents microaggregates. When dispersion occurs, the particles of organic matter and exchangeable cations were measured by separate in suspension due to their electrical charge. Clay standard methods. Sub-samples were placed in distilled water flocculation leads to soils that are considered to be stable in wa- and were subjected to four different energy inputs obtained by ter whereas dispersion is associated with soils that are consi- different numbers of inversions (end-over-end movements). The dered to be unstable in water. We may note that this termi- amounts of clay that dispersed into suspension were measured by light scattering (turbidimetry). An empirical equation was devel- nology is the opposite of that used in colloid science where oped that provided an approximate fit to the experimental data for the terms ‘stable’ and ‘unstable’ are used in relation to the turbidity as a function of number of inversions.
  • Dispersity in Polymer Science

    Dispersity in Polymer Science

    Pure Appl. Chem., Vol. 81, No. 2, pp. 351–353, 2009. doi:10.1351/PAC-REC-08-05-02 © 2009 IUPAC INTERNATIONAL UNION OF PURE AND APPLIED CHEMISTRY POLYMER DIVISION SUBCOMMITTEE ON POLYMER TERMINOLOGY* DISPERSITY IN POLYMER SCIENCE (IUPAC Recommendations 2009) Prepared by a Working Group consisting of R. G. GILBERT (AUSTRALIA), M. HESS (GERMANY), A. D. JENKINS (UK), R. G. JONES (UK), P. KRATOCHVÍL (CZECH REPUBLIC), AND R. F. T. STEPTO (UK) Prepared for publication by R. F. T. STEPTO‡ Polymer Science and Technology Group, Manchester Materials Science Centre, School of Materials, The University of Manchester, Grosvenor Street, Manchester, M1 7HS, UK *Membership of the Subcommittee on Polymer Terminology† during the preparation of this report (2003–2008) was as follows: M. Barón (Argentina, Secretary until 2003); M. Hess (Germany, Chairman to 2005, Secretary, 2006–2007); R. G. Jones (UK, Secretary 2003–2005, Chairman, from 2006); T. Kitayama (Japan, Secretary, from 2008); G. Allegra (Italy); T. Chang (Korea); C. dos Santos (Brazil); A. Fradet (France); K. Hatada (Japan); J. He (China); K.-H. Hellwich (Germany); R. C. Hiorns (France); P. Hodge (UK); K. Horie (Japan); A. D. Jenkins (UK); J.-I. Jin (Korea); J. Kahovec (Czech Republic); P. Kratochvíl (Czech Republic); P. Kubisa (Poland); I. Meisel (Germany); W. V. Metanomski (USA); V. Meille (Italy); I. Mita (Japan); G. Moad (Australia); W. Mormann (Germany); C. Ober (USA); S. Penczek (Poland); L. P. Rebelo (Portugal); M. Rinaudo (France); I. Schopov (Bulgaria); M. Schubert (USA); F. Schué (France); V. P. Shibaev (Russia); S. Słomkowski (Poland); R. F. T. Stepto (UK); D. Tabak (Brazil); J.-P.
  • Colloidal Suspensions

    Colloidal Suspensions

    Chapter 9 Colloidal suspensions 9.1 Introduction So far we have discussed the motion of one single Brownian particle in a surrounding fluid and eventually in an extaernal potential. There are many practical applications of colloidal suspensions where several interacting Brownian particles are dissolved in a fluid. Colloid science has a long history startying with the observations by Robert Brown in 1828. The colloidal state was identified by Thomas Graham in 1861. In the first decade of last century studies of colloids played a central role in the development of statistical physics. The experiments of Perrin 1910, combined with Einstein's theory of Brownian motion from 1905, not only provided a determination of Avogadro's number but also laid to rest remaining doubts about the molecular composition of matter. An important event in the development of a quantitative description of colloidal systems was the derivation of effective pair potentials of charged colloidal particles. Much subsequent work, largely in the domain of chemistry, dealt with the stability of charged colloids and their aggregation under the influence of van der Waals attractions when the Coulombic repulsion is screened strongly by the addition of electrolyte. Synthetic colloidal spheres were first made in the 1940's. In the last twenty years the availability of several such reasonably well characterised "model" colloidal systems has attracted physicists to the field once more. The study, both theoretical and experimental, of the structure and dynamics of colloidal suspensions is now a vigorous and growing subject which spans chemistry, chemical engineering and physics. A colloidal dispersion is a heterogeneous system in which particles of solid or droplets of liquid are dispersed in a liquid medium.
  • Pre-Polymerised Inorganic Coagulants and Phosphorus Removal by Coagulation - a Review

    Pre-Polymerised Inorganic Coagulants and Phosphorus Removal by Coagulation - a Review

    Pre-polymerised inorganic coagulants and phosphorus removal by coagulation - A review Jia-Qian Jiang and Nigel J D Graham Environmental and Water Resource Engineering, Department of Civil Engineering, Imperial College of Science, Technology and Medicine, London SW7 2BU Abstract This paper reviews the use of pre-polymerised inorganic coagulants in water and waste-water treatment, and discusses the removal of phosphorus by chemical precipitation and coagulation. Commonly used inorganic coagulants are aluminium or iron (III) based salts, but a range of hydrolysed Al/Fe species, and not the Al/Fe salt itself, are responsible for the removal of impurities from water. By the development and use of polymeric inorganic coagulants, the coagulation performance can be improved significantly in some cases. Chemical precipitation and coagulation in phosphorus removal are two different processes, with the former related to the compound solubility and the latter depending on the destabilisation-adsorption mechanism. Presently, there is uncertainty concerning the mechanisms and overall performance of phosphorus removal by pre-polymerised metal coagulants. Introduction coagulants in water and waste-water treatment; to assess the present use of chemical precipitation and coagulation as a means Coagulants used for water and waste-water treatment are pre- for phosphorus removal; to evaluate the overall performance of dominantly inorganic salts of iron and aluminium. When dosed pre-polymerised coagulants in comparison with that of conven- into water the iron or aluminium ions hydrolyse rapidly and in an tional coagulants; and to discuss the relevant coagulation mecha- uncontrolled manner, to form a range of metal hydrolysis species. nisms for treating water and waste water.
  • Known As the Dispersed Phase), Distributed Throughout a Continuous Phase (Known As Dispersion Medium)

    Known As the Dispersed Phase), Distributed Throughout a Continuous Phase (Known As Dispersion Medium)

    COLLOIDAL DISPERSIONS Dispersed systems consist of particulate matter (known as the dispersed phase), distributed throughout a continuous phase (known as dispersion medium). CLASSIFICATION OF DISPERSED SYSTEMS On the basis of mean particle diameter of the dispersed material, three types of dispersed systems are generally considered: a) Molecular dispersions b) Colloidal dispersions, and c) Coarse dispersions Molecular dispersions are the true solutions of a solute phase in a solvent. The solute is in the form of separate molecules homogeneously distributed throughout the solvent. Example: aqueous solution of salts, glucose Colloidal dispersions are micro-heterogeneous dispersed systems. The dispersed phases cannot be separated under gravity or centrifugal or other forces. The particles do not mix or settle down. Example: aqueous dispersion of natural polymer, colloidal silver sols, jelly Coarse dispersions are heterogeneous dispersed systems in which the dispersed phase particles are larger than 0.5µm. The concentration of dispersed phase may exceed 20%. Example: pharmaceutical emulsions and suspensions COMPARISON OF CHARACTERISTICS THREE DISPERSED SYSTEMS Molecular dispersions Colloidal dispersions Coarse dispersions 1. Particle size <1 nm 1 nm to 0.5 µm >0.5 µm 2. Appearance Clear, transparent Opalescent Frequently opaque 3. Visibility Invisible in electron Visible in electron Visible under optical microscope microscope microscope or naked eye 4. Separation Pass through semipermeable Pass through filter paper but Do not pass through
  • CHAPTER 3 Transport and Dispersion of Air Pollution

    CHAPTER 3 Transport and Dispersion of Air Pollution

    CHAPTER 3 Transport and Dispersion of Air Pollution Lesson Goal Demonstrate an understanding of the meteorological factors that influence wind and turbulence, the relationship of air current stability, and the effect of each of these factors on air pollution transport and dispersion; understand the role of topography and its influence on air pollution, by successfully completing the review questions at the end of the chapter. Lesson Objectives 1. Describe the various methods of air pollution transport and dispersion. 2. Explain how dispersion modeling is used in Air Quality Management (AQM). 3. Identify the four major meteorological factors that affect pollution dispersion. 4. Identify three types of atmospheric stability. 5. Distinguish between two types of turbulence and indicate the cause of each. 6. Identify the four types of topographical features that commonly affect pollutant dispersion. Recommended Reading: Godish, Thad, “The Atmosphere,” “Atmospheric Pollutants,” “Dispersion,” and “Atmospheric Effects,” Air Quality, 3rd Edition, New York: Lewis, 1997, pp. 1-22, 23-70, 71-92, and 93-136. Transport and Dispersion of Air Pollution References Bowne, N.E., “Atmospheric Dispersion,” S. Calvert and H. Englund (Eds.), Handbook of Air Pollution Technology, New York: John Wiley & Sons, Inc., 1984, pp. 859-893. Briggs, G.A. Plume Rise, Washington, D.C.: AEC Critical Review Series, 1969. Byers, H.R., General Meteorology, New York: McGraw-Hill Publishers, 1956. Dobbins, R.A., Atmospheric Motion and Air Pollution, New York: John Wiley & Sons, 1979. Donn, W.L., Meteorology, New York: McGraw-Hill Publishers, 1975. Godish, Thad, Air Quality, New York: Academic Press, 1997, p. 72. Hewson, E. Wendell, “Meteorological Measurements,” A.C.
  • GPC - Gel Permeation Chromatography Aka Size Exclusion Chromatography- SEC

    GPC - Gel Permeation Chromatography Aka Size Exclusion Chromatography- SEC

    GPC - Gel Permeation Chromatography aka Size Exclusion Chromatography- SEC Wendy Gavin Biomolecular Characterization Laboratory Version 1 May 2016 1 Table of Contents 1. GPC Introduction………………………………………………………. Page 3 2. How GPC works………………………………………………………... Page 5 3. GPC Systems…………………………………………………………… Page 7 4. GPC/SEC Separations – Theory and System Considerations… Page 9 5. GPC Reports……………………………………………………………. Page 10 6. Calibrations of GPC systems………………………………………... Page 14 7. GPC preparation……………………………………………………….. Page 16 8. Alliance System………………………………………………………… Page 17 9. GPC columns…………………………………………………………… Page 18 2 1. GPC Introduction Gel permeation chromatography (GPC) is one of the most powerful and versatile analytical techniques available for understanding and predicting polymer performance. It is the most convenient technique for characterizing the complete molecular weight distribution of a polymer. Why is GPC important? GPC can determine several important parameters. These include number average molecular weight (Mn), weight average molecular weight(Mw) Z weight average molecular weight(Mz), and the most fundamental characteristic of a polymer its molecular weight distribution(PDI) These values are important, since they affect many of the characteristic physical properties of a polymer. Subtle batch-to-batch differences in these measurable values can cause significant differences in the end-use properties of a polymer. Some of these properties include: Tensile strength Adhesive strength Hardness Elastomer relaxation Adhesive tack Stress-crack resistance Brittleness Elastic modules Cure time Flex life Melt viscosity Impact strength Tear Strength Toughness Softening temperature 3 Telling good from bad Two samples of the same polymer resin can have identical tensile strengths and melt viscosities, and yet differ markedly in their ability to be fabricated into usable, durable products.
  • The Influence of Inter-Particle Forces on Diffusion at the Nanoscale

    The Influence of Inter-Particle Forces on Diffusion at the Nanoscale

    www.nature.com/scientificreports OPEN The infuence of inter-particle forces on difusion at the nanoscale Francesco Giorgi1, Diego Coglitore2, Judith M. Curran1, Douglas Gilliland3, Peter Macko3, Maurice Whelan3, Andrew Worth3 & Eann A. Patterson1 Received: 18 March 2019 Van der Waals and electrostatic interactions are the dominant forces acting at the nanoscale and they Accepted: 12 August 2019 have been reported to directly infuence a range of phenomena including surface adhesion, friction, Published: xx xx xxxx and colloid stability but their contribution on nanoparticle difusion dynamics is still not clear. In this study we evaluated experimentally the changes in the difusion coefcient of nanoparticles as a result of varying the magnitude of Van der Waals and electrostatic forces. We controlled the magnitude of these forces by varying the ionic strength of a salt solution, which has been shown to be a parameter that directly controls the forces, and found by tracking single nanoparticles dispersed in solutions with diferent salt molarity that the difusion of nanoparticles increases with the magnitude of the electrostatic forces and Van der Waals forces. Our results demonstrate that these two concurrently dynamic forces play a pivotal role in driving the difusion process and must be taken into account when considering nanoparticle behaviour. Gold nanoparticles have attracted a growing interest in the scientifc community in recent years, especially for biological and medical applications. However, there is a lack of knowledge about the mechanisms that regulate their difusion through liquid media. It is well-known that two of the main forces acting on charged nanoparticles dispersed in a medium are Van der Waals and electrostatic forces, but their actual contribution to particle difu- sion has not been experimentally investigated.
  • Particle Aggregation During a Diatom Bloom. 11. Biological Aspects

    Particle Aggregation During a Diatom Bloom. 11. Biological Aspects

    MARINE ECOLOGY PROGRESS SERIES Published January 24 Mar. Ecol. Prog. Ser. Particle aggregation during a diatom bloom. 11. Biological aspects Ulf Riebesell Alfred Wegener Institute for Polar and Marine Research, Colurnbusstr., D-2850 Bremerhaven. Germany ABSTRACT: For a 6 wk period covering the time before, during, and after the phytoplankton spring bloom, macroscopic aggregates (20.5 mm diameter) were repeatedly collected and water column properties simultaneously measured at a fixed station in the Southern North Sea. Distinct changes in aggregate structure and composition were observed during the study. Predominantly detrital aggregates dur~ngthe early phase of the study were followed by diatom-dominated algal flocs around the peak of the bloom. Mucus-rich aggregates containing both algal and detrital components and with large numbers of attached bacteria dominated the post-bloom interval. The phytoplankton succession within the aggregates closely reflected the succession in the water column with a time delay of a few days. Algal flocculation did not occur as a simultaneous aggregation of the entire phytoplankton community, but as a successional aggregat~onof selected diatom species. Although the concentrations of ~norganicnutrients diminished considerably during the development of the phytoplankton bloom, the termination of the bloom appeared to be mostly controlled by physical coagulation processes. The importance of biologically-controlled factors for physical coagulation is discussed. INTRODUCTION stickiness, proposed that physical processes alone could determine the time and extent of algal aggregation. Mass flocculation during diatom blooms as predicted Based on a physical coagulation model, Jackson pre- by Smetacek (1985) has since been documented both in dicted that the rate of aggregation strongly depends on the field (Kranck & Milligan 1988, Alldredge & Got- algal concentration.
  • Lecture Notes on Structure and Properties of Engineering Polymers

    Lecture Notes on Structure and Properties of Engineering Polymers

    Structure and Properties of Engineering Polymers Lecture: Microstructures in Polymers Nikolai V. Priezjev Textbook: Plastics: Materials and Processing (Third Edition), by A. Brent Young (Pearson, NJ, 2006). Microstructures in Polymers • Gas, liquid, and solid phases, crystalline vs. amorphous structure, viscosity • Thermal expansion and heat distortion temperature • Glass transition temperature, melting temperature, crystallization • Polymer degradation, aging phenomena • Molecular weight distribution, polydispersity index, degree of polymerization • Effects of molecular weight, dispersity, branching on mechanical properties • Melt index, shape (steric) effects Reading: Chapter 3 of Plastics: Materials and Processing by A. Brent Strong https://www.slideshare.net/NikolaiPriezjev Gas, Liquid and Solid Phases At room temperature Increasing density Solid or liquid? Pitch Drop Experiment Pitch (derivative of tar) at room T feels like solid and can be shattered by a hammer. But, the longest experiment shows that it flows! In 1927, Professor Parnell at UQ heated a sample of pitch and poured it into a glass funnel with a sealed stem. Three years were allowed for the pitch to settle, and in 1930 the sealed stem was cut. From that date on the pitch has slowly dripped out of the funnel, with seven drops falling between 1930 and 1988, at an average of one drop every eight years. However, the eight drop in 2000 and the ninth drop in 2014 both took about 13 years to fall. It turns out to be about 100 billion times more viscous than water! Pitch, before and after being hit with a hammer. http://smp.uq.edu.au/content/pitch-drop-experiment Liquid phases: polymer melt vs.
  • Food Dispersion Systems Process Stabilization. a Review

    Food Dispersion Systems Process Stabilization. a Review

    ───Food Technology ─── Food dispersion systems process stabilization. A review. Andrii Goralchuk, Olga Grinchenko, Olga Riabets, Оleg Kotlyar Kharkiv State University of Food Technology and Trade, Kharkiv, Ukraine Abstract Keywords: Introduction. The overview is given to systematize Emulsion information on the indicators, affecting the production and Foam stabilization of foams and emulsions, for applying the Stabilization existing regularities for more complex dispersed Rheology (polyphase) systems. Layers Materials and methods. Analytical studies of the production and stabilization of foams and polyphase dispersed systems published over the past 20 years. The research focuses on the foams, emulsions, foam emulsion systems and the systems, being simultaneously foam, Article history: emulsion and suspension. Results and discussion. Though foams and Received 28.11.2018 emulsions have similarities and their production differs in Received in revised form 15.08.2019 the dispersion rate, determined by the rate of surfactants Accepted 28.11.2019 adsorption. Emulsifying is faster than foaming, therefore, the production of foam emulsions can be sequential only. Coalescence, as a destruction indicator, is typical of foams and emulsions alike, and it is determined by the properties Corresponding author: of surfactants. Other indicators are determined by the features of the dispersion medium. The study systematized Andrii Goralchuk the factors, ensuring the stability of dispersion systems. The E-mail: structural mechanical factor is effective in
  • UNIVERSITY of CALIFORNIA Los Angeles Phase Behavior of Particle

    UNIVERSITY of CALIFORNIA Los Angeles Phase Behavior of Particle

    UNIVERSITY OF CALIFORNIA Los Angeles Phase Behavior of Particle-Polyelectrolyte Complexes A thesis submitted in partial satisfaction of the requirements for the degree Master of Science in Chemical Engineering by John E. Neilsen 2019 ABSTRACT OF THE THESIS Phase Behavior of Particle-Polyelectrolyte Complexes by John Neilsen Master of Science in Chemical Engineering University of California, Los Angeles, 2019 Professor Samanvaya Srivastava, Chair The phase behavior of particle-polyelectrolyte complexes was systematically studied using a model system comprising oppositely charged silica nanoparticles and poly(allylamine) hydrochloride (PAH) polycations. Phase behaviors of aqueous mixtures of silica nanoparticles and PAH were elucidated over a wide parameter space of particle and polyelectrolyte concentrations as well as solution pH. Trends in phase behaviors were analyzed to create a fundamental understanding of the fundamental properties that govern the complexation of these oppositely charged species. ii The thesis of John Neilsen is approved. Vasilios Manousiouthakis Junyoung O. Park Samanvaya Srivastava, Committee Chair University of California, Los Angeles 2019 iii Contents 1. Introduction……………………………………………………..………………….…….…..….…..…1 1.1 Aqueous Particle-Polyelectrolyte Self-Assemblies…………..…….....………….....….….1 1.2 Biological Significance …………..……………………..…...….…...…......…….…………..2 1.3 Technological Applications…………..………………….……......……………...………....2 2. Background……………………………………………...………………….……………………..……5 2.1 The Voorn-Overbeek Theory……….………………….…….……………….……….……6