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Applications Of Micellear Phase Of Pluronics And Tetronics As Nanoreactors In The Synthesis Of Nobel Metal Nanoparticles
Published in Alexander V. Vakhrushev, Suresh C. Ameta, Heru Susanto, A. K. Haghi, Advances in Nanotechnology and the Environmental Sciences, 2019
Rajpreet Kaur, Navdeep Kaur, Divya Mandial, Lavanya Tandon, Poonam Khullar
Poloxamers and poloxamine nonionic surfactants are approved by FDA to be used as drug carriers in parenteral system, food additives and pharmaceutical ingredients have diverse applications in various biomedical fields ranging from drug delivery and medical imaging to management of vesicular diseases and disorders. The PPO block of the copolymers undergoes hydrophobic interactions with the hydrophobic surfaces of the nanospheres. This kind of adsorption results in the free movement of PEO side arms which also causes steric repulsions. The extent of adsorption depends on both size of PEO and PPO block as well as type of interactions present such as nanoparticle surface charge, hydrogen bond between PEO unit and the constituent groups on the particle surface. These kind of engineered nanoparticles exhibit reduced adsorption of proteins and blood as compared to the uncoated nanoparticles and hence resist ingestion by phagocytic scavenger cells [81, 82].
Nanogels for Brain Targeting
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Nanocarriers for Brain Targeting, 2019
Nagarjun Rangaraj, Sunitha Sampathi
Polyethers and polyesters (Fig. 15.3) are biodegradable polymers formed by monomers linked by ether (R-O-R) and ester (RCOOR) bonds respectively. Polyglycolic acid (PGA), Polylactic acid (PLA) and their copolymers- poly (lactic acid-co-glycolic acid) (PLGA), are the commonly used polyesters. PLA may be in L or D form based on the asymmetric a-carbon. Since the naturally occurring form is L it is considered as more biodegradable than D form. PLA shows greater degradation rate in comparison to PGA. Polyethylene glycol is a commonly used polyether polymer, owing to its high biocompatibility (98% excreted by man), water solubility, high stability, and no toxicity and is regarded as a gold standard in the area of drug delivery. PEG increases the circulation time by extending the endocytosis, phagocytosis, liver uptake and clearance and other adsorptive processes. Poloxamers are blocked co-polymers of two hydrophilic chains of polyethyleneoxide and one hydrophobic polypropylene oxide. The trade name is Pluronic which is available in various grades based on the varying length of polymer blocks (Devi et al., 2013, Gupta et al., 2012, Maurus et al., 2004, Uhrich et al., 1999).
Polymeric Matrix Systems for Drug Delivery
Published in Raj K. Keservani, Anil K. Sharma, Rajesh K. Kesharwani, Drug Delivery Approaches and Nanosystems, 2017
Ilić-Stojanović Snežana, Ljubiša Nikolić, Nikolić Vesna, Dušica Ilić, Ivan S. Ristić, Ana Tačić
Due to the amphiphilic character, micelles of poloxamer possess surfactant properties, including the ability to interact with the hydrophobic surfaces and biological membranes. The micelle core consists of hydrophobic PPO blocks, which are separated from the aqueous medium by a shell of hydrophilic PEO chains. Various therapeutic and diagnostic agents are incorporated in PPO core. The shell of PEO chain ensures that micelles remain in the dispersed state and reduces the undesirable interactions of drug with cells and proteins (Batrakova and Kabanov, 2008). The dissolved drugs can modify aggregation and micelle stability. A small amount of o-xylene increases the tendency of ambiphiles to form aggregates, which applies to the PEO-PPO-PEO triblock copolymers, while urea increases and the phenol decreases CMC value due to the interaction with the PEO chains (Jiang et al., 2001). Naproxen and indomethacin does not affecting CMC, but lead to a slight reduction in the micelles size and reduction of the aggregation number (Sharma and Bhatia, 2004). Short-chain alcohols, e.g., ethanol, prevent the formation of micelles in the water, while the hydrophobic aliphatic alcohols, such as butanol, favor the aggregation (Pandya et al., 1993; Armstrong et al., 1996). The temperature required for the beginning of the micelles formation reduces by increase of the polymer concentration (Alexandridis and Hatton, 1995; Alexandridis et al., 1995).
Bioinks—materials used in printing cells in designed 3D forms
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Dilara Goksu Tamay, Nesrin Hasirci
Poloxamers are tri-block copolymers, having a hydrophobic chain in the center between two hydrophilic blocks. The central group is poly(propylene oxide) (PPO) and the end groups are poly(ethylene oxide) (PEO). The length of the chains can be tailored so that the end product may have the desired properties. Pluronic is the trade name of poloxamers. Companies sell poloxamers with codes which points molecular mass of core part and percentage of end groups. Due to the unique structure, poloxamers have thermo-gelling property. They can flow at low temperatures and can easily form self-assembling gels at room temperatures in a reversible process. In aqueous media, they form micelles where the PPO groups are concentrated at the core and PEO groups are turned towards to medium. These micron size particles are generally used as drug delivery systems [226]. Formation of micelle process and the sizes of micelles can be tailored by choosing the proper poloxamers with certain chemical structure (chain lengths and molar ratios of hydrophilic/hydrophobic parts) and at preferable concentration. Presence of salts in the medium affects the phase transition.
Influence of composition on the encapsulation properties of P/O/W multiple emulsions for Vitamin C
Published in Journal of Dispersion Science and Technology, 2019
Wanping Zhang, Liaoyuan Zhang, Dan Zhu, Yiwei Wu, Yubo Qin, Wenhua Ou, Lili Song, Qianjie Zhang
As reported in literatures, there are several factors could affect W/O/W system stability and encapsulation rate, including the structure and concentration of emulsifiers, the osmotic press and additives.[18] Two types of emulsifiers are required in the preparation of double emulsions. Firstly, lipophilic emulsifiers with a low Hydrophile-Lipophile-Balance (low HLB) soluble in the oil phase are required to stabilize the primary W/O interface. The primary water droplets are inclined to coalescence with each other, and can be loosed to the outer water phase through mass transfer, thus the encapsulation rate will be reduced. Therefore, it is necessary to use sufficient lipophilic emulsifiers with large steric lipophilic group to prepare stable W/O droplets.[22] The lipophilic emulsifier, such as Cetyl PEG/PPG-10/1 Dimethicone (EM90), is a type of polysiloxane with polyethyleneoxide and alkyl side groups, which plays a critical role in the formation of the W/O interfacial film. Secondly, hydrophilic emulsifiers with high HLB are needed in the external water phase to stabilize the O/W interface.[19–21] Comparing with the monomeric emulsifiers, the polymeric emulsifiers have shown superior physical stability. Poloxamer 407 (F127) is a hydrophilic emulsifier with strong hydrophilicity which stems from its special chemical structure (A-B-A block copolymers that consist of a large number of polyethylene oxide and polypropylene oxide).[23]
Efficiency of sildenafil encapsulation in poloxamer micelles
Published in Journal of Dispersion Science and Technology, 2019
Charisopon Chunhachaichana, Teerapol Srichana
Poloxamer is a synthetic nonionic triblock copolymer well known for its thermo-responsive property, biocompatibility, biodegradability and low toxicity. Poloxamers, including poloxamer 188 (P188), are a series of closely related block copolymers of ethylene oxide (EO) and propylene oxide (PO), which conform to a basic EOa-POb-EOa structure. P188 are usually used as emulsifiers, stabilizers, and solubilizers.[5] Recently, P188 has also found practical applications in drug delivery systems,[6–8] which stems from their ability to form block copolymer micelles characterized by a hydrophobic PO core and hydrophilic EO shell. However, it can only form micelles above its critical micelle concentration (CMC) at a specific temperature, and in some cases, the micellization can be interrupted by the change in temperature or the presence of electrolytes or drug molecules, causes the instability of the micelles.[9] It leaves us with the need not only to confirm the CMC of the surfactants but also to ascertain the physicochemical and thermodynamic evidence of the micelles in the presence of the drug molecules. Several analytical methods were published to investigate the micelle formation, including surface tensiometry,[10,11] dynamic light scattering (DLS),[12–14] spectrophotometry,[10,11,13,15] conductometry,[11,16] and ultrasonic resonance.[12]