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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.
Active Targeting Strategies in Cancer with a Focus on Potential Nanotechnology Applications
Published in Mansoor M. Amiji, Nanotechnology for Cancer Therapy, 2006
Nanoparticles can be designed in a variety of ways to achieve targeted delivery. Some targeting strategies rely upon inherent properties of the particle, in particular, its composition, size, and surface properties. Furthermore, the particle itself can either be the agent being delivered, or it can be prepared to carry a cargo for delivery. Cargo release from the nanoparticles can occur while the nanoparticle is still relatively intact or through its decomposition. A number of methods have been described to integrate and retain cargo components within nanoparticles and these, in general, match to chemical or physical characteristics of the cargo with those of the material used to generate the nanostructure. For example, positively charged cargo can be held within the nanoparticle through interactions with an internal network such as a polyanionic polymer that resembles the organization of secretory granules synthesized by cells.40 Alternately, organized complexes akin to coacervates proposed to participate in cell structure evolution can be formed between cargo and particle matrix.40 Therefore, for some cancer-targeting strategies, one should consider not only compatibility of the nanoparticle carrier with its cargo but also degradation events that might affect temporal aspects of particle stability and cargo release.
Synthetic Polymers in Cosmetics
Published in E. Desmond Goddard, James V. Gruber, Principles of Polymer Science and Technology in Cosmetics and Personal Care, 1999
E. Desmond Goddard, James V. Gruber
It is felt that the presence of the polymer/surfactant coacervate is important for deposition of the polymer onto the anionic surfaces of hair and skin (159). It has been demonstrated that when a cationic polymer is deposited onto hair as a coacervate, subsequent rinsing removes the anionic surfactant more quickly than the bound polymer. In these electokinetic measurements, the overall charge of the hair gradually becomes more cationic. It should be kept in mind, also, that coacervate can form when a concentrated anionic surfactant solution containing a solubilized cationic polymer is diluted by the addition of water. This is the typical mode of application of conditioning shampoos to hair and skin during washing. The deposition occurs during the rinsing cycle and is appropriately termed “dilution deposition.”
Microencapsulation of Lactobacillus plantarum LN66 and its survival potential under different packaging conditions
Published in Journal of Microencapsulation, 2022
Min Zhang, Cheng Yin, Jing Qian
After selecting the optimal conditions for complex coacervation in Section 2.2, the production of the microcapsules was performed according to methodology described by Sohrab Sharifi, with slightly modifications. At the first step, 200 ml GE (2%, w/v) solution was prepared at 40 °C. The probiotic bacterium cells, prepared in Section 2.3.1, were slowly added to the solution. Then, 200 ml of GA (2%, w/v) was added to this mixture, using a 1:1 ratio of biopolymers (GE: GA). The pH of the final solution was regulated to 4.0 by adding a 10% (w/v) acetic acid dropwise slowly to stimulate electrostatically bindings between GE and GA. All of the above stages were done at 40 °C. To ensure completion of the formation of complex coacervate and allowing the separation of the phases, the produced liquid microcapsule was kept at 4 °C for 2 h. Finally, wet microcapsules were freeze dried (Lyobeta 5 PS, Spanish) at −65 °C for 48 h.
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
The viability of the bacteria is strain- and formulation-dependent and ranges from 0.2 to 2 log CFU loss [107,127,128]. Complex coacervation may enable the combination of interesting bacterial strains with other functional foods, such as omega-3 fatty acids [128]. Furthermore, adding an extra enzymatic crosslinking step would significantly improve bacterial viability. While the ionic bonds present in the coacervates can form a protective layer around the bacteria, adding stronger covalent crosslink bonds in the protein structure using an enzyme such as transglutaminase can be beneficial [129]. In fact, as complex coacervates are dependent on pH, temperature and ionic strength, their structure is always changing in response to the environment and therefore is adaptive, which is an advantage for storage [105]. This adaptive structure illustrates the advantages of this technique with its versatility and efficiency.
Current trends in PLGA based long-acting injectable products: The industry perspective
Published in Expert Opinion on Drug Delivery, 2022
Omkara Swami Muddineti, Abdelwahab Omri
Microencapsulation technique is used to prepare microspheres, including ionic gelation, spray drying, coacervation, solvent evaporation, extraction, and interfacial polymerization to harden and separate the particles [49]. Out of all the techniques, solvent evaporation/extraction is the most widely used technique for manufacturing the marketed PLGA-based microspheres. Briefly, the solvent evaporation/extraction method depends on the emulsification of the polymer (organic) solution in a continuous (aqueous) phase and later formation of microspheres via precipitation. The solvent used to solubilize the polymer and active pharmaceutical ingredient (API) should have sufficient solubility in the aqueous phase to partition and precipitation to prepare desired microparticles. Coacervation and phase separation technique is also used to manufacture PLGA-based microspheres at higher scales [50]. In this technique, polymer (mixture of polymers) solution is separated into a dilute polymer phase and concentrated coacervate phase, which is in equilibrium. Phase separation can be initiated using a change in temperature, the addition of non-solvent, and a change in ionic strength. Further, these changes induce interaction between polymers over polymer–solvent interaction, resulting in polymer dehydration. Thermal or chemical treatment is frequently used to stabilize the coacervate emulsion droplets to form microspheres, which may not apply to sensitive molecules such as proteins.