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What Are Polymeric Carriers?
Published in Mesut Karahan, Synthetic Peptide Vaccine Models, 2021
Gülderen Karakuş, Dolunay Şakar Daşdan
Microencapsulation is the coating of a solid or liquid particle or a droplet with a polymeric film material and known as the first of the microparticular systems entering our lives in recent years. Microencapsulation technology is often used in a wide range of pharmaceuticals, foodstuffs, agriculture, cosmetics, textiles, etc. In the case of polymeric vaccine techniques, the active drug substance is coated with a coating material called a wall at the so-called core. The liquid substance is reduced by more easily portable volatility, increased stability, and stability with this coating technique. In addition, the effect of time also increases. Different techniques are used for encapsulation. Depending on the physical and chemical properties of the core material, the technique to be used also varies. The coacervation method is the oldest and the most widely used method. Coacervation occurs as a result of temperature change, addition of salt, addition of another polymer or polymer-polymer interaction. Unlike microcapsules, microspheres are the carriers that enable the active substance in the drug to be delivered to the desired area in the body. Biocompatibility and non-toxicity are the most important reasons. The dimensions range in size from 1 µm to 50 µm. The polymers (natural or synthetic) generally used are chitosan, polyesters, lipids, and cellulose derivatives (Geary et al. 2015).
Antigen Delivery Systems Used to Induce Immunomodulation
Published in Thomas F. Kresina, Immune Modulating Agents, 2020
M. Zahirul I. Khan, Ian G. Tucker, Joan P. Opdebeeck
Microparticles can be prepared in different ways, including coacervation and various polymerizations. Some of these methods require the use of organic solvents and long encapsulation processes that may denature the labile antigen molecules. To overcome such problem, absorption of the antigen from aqueous solutions into preformed gluteraldehyde cross-linked chitosan microspheres was attempted with limited success [92]. A new class of water-soluble polymers, polyphosphazenes, has been suggested as a solution to this organic solvent-related problem. Gelation of an aqueous solution of the polymer by ionic cross-linking through metal ions (e.g., Ca2+) produces a hydrogel that has been used to incorporate antigen and deliver it in the form of microspheres [8]. Their release characteristics can be modulated by changing the polymer concentration within the matrix, incorporating appropriate side groups to the polymer, or coating the microspheres with cationic substances like poly(l-lysine) [8], The polymer also works as an adjuvant in its solution form when mixed and delivered with antigen; preliminary studies suggest that this polymer is a safe adjuvant [8].
Chemical Modulation of Topical and Transdermal Permeation
Published in Marc B. Brown, Adrian C. Williams, The Art and Science of Dermal Formulation Development, 2019
Marc B. Brown, Adrian C. Williams
Coacervation is a somewhat specialised form of ion-pairing and is usually used to describe electrostatically driven liquid–liquid phase separation when oppositely charged macromolecular ions associate; one liquid phase is a concentrated colloidal phase (the coacervate) and the other phase exists as a highly dilute colloidal phase. The term “coacervate” essentially means “to assemble together or cluster” and the coacervate droplets typically have a diameter between 1 and 100 µm. A common example of this phenomenon is when aqueous solutions of the oppositely charged biopolymers gelatin and gum arabic are mixed; a gelatin–acacia coacervate has been used to encapsulate benzocaine in topical formulations.
Fecal microbiota transplantation: a review on current formulations in Clostridioides difficile infection and future outlooks
Published in Expert Opinion on Biological Therapy, 2022
Adèle Rakotonirina, Tatiana Galperine, Eric Allémann
Complex coacervation consists of applying oppositely charged biopolymers to form a soluble complex, further promoting their aggregation until their size and surface properties render them insoluble and liquid-to-liquid phase separation occurs. This process depends on the solution pH value, ionic strength, polymer concentration, ratio of polymers, temperature degree of homogenization and physical conditions during the experiment. Proteins and polysaccharides are mostly used for this technique: gelatin, albumin, whey protein, beta-lactoglobulin, Arabic gum, chitosan, pectin, alginates, xanthan gum, carrageenan, carboxymethylcellulose and other plant proteins or polysaccharides [106]. Briefly, the bacterial cells are added to the mixture of polymers (with the best ratio and concentration), and the pH value is adjusted for optimal coacervation. Then, the mixture is left either at room temperature or in an ice bath to solidify, and the microcapsules are harvested by decantation of the clear supernatant [107,127]. The obtained microcapsules can be either dried on a spouted bed, vacuum-dried, freeze-dried or spray-dried [106]. The complex coacervation process is presented in Figure 5.
A topical formulation containing quercetin-loaded microcapsules protects against oxidative and inflammatory skin alterations triggered by UVB irradiation: enhancement of activity by microencapsulation
Published in Journal of Drug Targeting, 2021
David L. Vale, Renata M. Martinez, Daniela C. Medeiros, Camila da Rocha, Natália Sfeir, Renata F. V. Lopez, Fabiana T. M. C. Vicentini, Waldiceu A. Verri, Sandra R. Georgetti, Marcela M. Baracat, Rúbia Casagrande
In general, microencapsulation drawbacks include microsphere aggregation and adherence [53]. However, microencapsulation has other advantages, and in special the system we used that is a microencapsulation method developed by Baracat, Nakagawa [28] in which the drug is encapsulated using the complex coacervation method with pectin and casein polymers. These are low-cost natural polymers and are susceptible to in vivo degradation through hydrolysis or enzymatic attack. Pectin is a linear polysaccharide from the residue of D-galacturonic acid in bond α (1-4), which forms a complex with another polymer due to its pH-dependent charge. Casein, on the other hand, is a glycophosphoprotein with amphiphilic properties, that is, amphoteric character [54]. In the complex coacervation process, these polymers unite and form microcapsules of approximately 3.138 to 4.290 µm in size with first order kinetic release for 6 h [28]. In another study, the investigation of the drying method of these microcapsules based on pectin and casein was carried out and its alteration according to the incorporated drug investigated. The drying method by spray dryer remained stable physico-chemical characteristics of the microcapsules and showed a gradual and monomodal release of the incorporated drug [54].
Microencapsulation of fish oil by casein-pectin complexes and gum arabic microparticles: oxidative stabilisation
Published in Journal of Microencapsulation, 2019
Arianne Cunha dos Santos Vaucher, Patrícia C. M. Dias, Pablo T. Coimbra, Irina dos Santos Miranda Costa, Ricardo Neves Marreto, Gisela Maria Dellamora-Ortiz, Osvaldo De Freitas, Mônica F. S. Ramos
In this work, two processes of microencapsulation were employed: a mechanical (spray drying) and a chemical (complex coacervation) process. Microencapsulation by spray drying occurs in two steps: emulsification of the core oil in the polymer solution followed by removal of the solvent by a hot stream of air (Thies 1996). Water soluble polymers such as modified starches, whey, maltodextrin, beta-cyclodextrin and GA are generally used as wall material (Arslan-Tontul and Erbas 2017). Complex coacervation is based on the ability of cationic and anionic water-soluble polymers to interact in water to form a liquid, polymer-rich phase called a complex coacervate. Dispersion of a water insoluble core material in this system and wetting of this core material by the complex coacervate, results in spontaneous coating of the core material with a thin film of coacervate. In this case, the capsules are formed when this liquid film is solidified (Thies 1996) and spray drying is used to dry the resulting material. A variety of proteins and polysaccharides are used to obtain biopolymer particles, including whey proteins, casein, soy proteins, gelatine, zein, starch, cellulose and pectin (Matalanis et al.2011).