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Medication: Nanoparticles for Imaging and Drug Delivery
Published in Harry F. Tibbals, Medical Nanotechnology and Nanomedicine, 2017
In a typical method for preparing nanoparticles of insulin or other pep-tide, the peptide is dissolved in an aqueous solution; then a nonsolvent such as a low molecular weight (C1 to C6) alcohol is stirred in with the aqueous solution. The alcohol absorbs up to 100% of its weight of water, causing the peptide to precipitate out of solution, with particles having diameters in the range of about 100-200 nm. If the mixture contains a suitable polymer, the particles are spontaneously coated as they precipitate; the process is called phase inversion nanoencapsulation.
Postprocessing of Dialysis Membranes
Published in Sirshendu De, Anirban Roy, Hemodialysis Membranes, 2017
The first aspect to discuss about this study is the physical properties of the membranes. Polymers like PVP and PEG help a membrane engineer tailor the pore sizes. Membranes are formed by the process of phase inversion. In this study, non-solvent-induced phase inversion14–16 has been employed as has been discussed in the previous chapters. In this regard, it is important to note that although both PVP and PEG are hydrophilic polymers, yet they work in an antagonistic manner.17 PVP induces the formation of pores, whereas PEG helps in constricting them. This interplay manifests in the MWCO and hydraulic permeability values of HCO and HPM membranes (Tables 6.2 and 6.3). HCO membranes have only PVP and this induces quicker demixing of the solution, yielding more open membranes. HPMs have PEG as well in their composition; hence, the viscosity of the solution is more, leading to delayed demixing and hence denser membranes. Thus, the MWCO of HCO is more than that of HPM and, consequently, their porosities and hydraulic permeabilities too follow the same trend.
Ultrasound Instrumentation and Techniques
Published in Martin G. Pomper, Juri G. Gelovani, Benjamin Tsui, Kathleen Gabrielson, Richard Wahl, S. Sam Gambhir, Jeff Bulte, Raymond Gibson, William C. Eckelman, Molecular Imaging in Oncology, 2008
Paul A. Dayton, Mark A. Borden
Phase inversion or pulse inversion imaging is a technique in which two transmitted pulses of opposite phase are transmitted one after the other separated by a delay (33,54,55). This technique takes advantage of the nonlinear scattering of microbubbles. Linear scatterers such as tissue reflect the original and inverted pulses similarly, and the two opposite phase pulses will cancel when echoes from the two pulses are summed. In contrast, nonlinear scatterers, such as contrast agent microbubbles, respond differently to the different phase pulses, and the sum of the echoes from microbubbles will not be zero. This technique achieves tissue suppression in exchange for a reduction in imaging frame rate. A major limitation with this technique, as well as all multiple-pulse imaging strategies, is sensitivity to tissue or contrast motion. Additionally, the nonlinear response of tissue at higher acoustic pressures limits the ability to phase inversion imaging to fully suppress tissue.
Advances in engineering and delivery strategies for cytokine immunotherapy
Published in Expert Opinion on Drug Delivery, 2023
Margaret Bohmer, Yonger Xue, Katarina Jankovic, Yizhou Dong
Cytokine-loaded microspheres may also be a treatment for inflammatory gastrointestinal disorders, such as inflammatory bowel disease (IBD). In one study, IL-10 was loaded into microspheres formulated by phase inversion nanoencapsulation (PIN), in which a dilute polymer solution is added to a large quantity of non-solvent to spontaneously form microspheres [155]. These IL-10-loaded microspheres were administered to a mouse model of spontaneous gastrointestinal polyposis (APCmin/+) to curb IL-17 production in T cells, since IL-17 stimulates polyp growth in APCmin/+ mice. Consequently, these microspheres resulted in reduced IL-17 expression by IL-17-producing pathogenic Tregs and strengthened regular Treg-mediated polyposis repression [156]. A different study researched microspheres containing TGF-β and all-trans retinoic acid (ATRA) to treat IBD [157]. TGF-β was encapsulated in PLA microspheres via PIN and ATRA was loaded into PLGA microspheres. This microsphere combination attenuated IBD symptoms in two mouse models of colitis: dextran sodium sulfate-induced colitis and CD4+ CD25- T-cell transfer colitis. The proposed mechanism involved TGF-β-dependent gut Treg production: a mechanism for which retinoic acid is a cofactor [157]. However, a later study on this same microsphere combination found that its administration substantially reduced endogenous TGF-β levels in the colon and blood [158]. The authors suggested this may be due to a negative feedback system where the presence of exogenous TGF-β reduced endogenous production [158].
Bridging the gap between fundamental research and product development of long acting injectable PLGA microspheres
Published in Expert Opinion on Drug Delivery, 2022
Xun Li, Zhanpeng Zhang, Alan Harris, Lin Yang
Figure 2a shows the novel PLGA microspheres manufacturing process of the ImSus technology platform which is based on the phase inversion method. It can be easily found that all the phase inversion and microspheres formation process can be completed in one vessel. Additionally, all the excipients in the ImSus technology are generally regarded as safe (GRAS) and approved for parenteral applications. Meanwhile, the organic solvents for dissolving PLGA are selected from ICH class 3 solvents and completely or partly soluble in water. In terms of the phase inversion process, firstly, a drug solution and PLGA solution are mixed by dissolver. Then, a surfactant solution is added, which initiates the phase inversion movement to form drug loaded PLGA microspheres. The last step is the regular PLGA microsphere washing and freeze-drying process. Additionally, Figure 2b shows the influence of critical components in the phase inversion method which is reflected by the ternary phase diagram. It can be easily found that the use of partially water-soluble organic solvents results in a quick precipitation of the PLGA particle suspension, thereby skipping the emulsification procedure. More interestingly, different internal structures (e.g. dense matrix and porous matrix) and surface morphologies (spheres, sponges, or capsules) can be obtained by optimizing process parameters ‘dispersing speed and time’ and ‘adding surfactant phase rate.’ With respect to the ternary phase diagram the dense and the porous polymer matrix are generated by following the phase inversion path (1) or (2), respectively [56].
Development and optimization of drug-loaded nanoemulsion system by phase inversion temperature (PIT) method using Box–Behnken design
Published in Drug Development and Industrial Pharmacy, 2021
Manish Kumar, Ram Singh Bishnoi, Ajay Kumar Shukla, Chandra Prakash Jain
In the PIT method, phase inversion is induced by varying the temperature. Nonionic surfactants, such as polyethoxylated surfactants undergo dehydration of polyoxyethylene groups when the temperature is increased, so become lipophilic that leads to changes in the spontaneous curvature of the surfactant. At low temperature, polyethoxylated surfactants are hydrophilic which facilitate the formation of oil in water (O/W) emulsion. When the temperature increases, surfactant becomes lipophilic, which leads to phase inversion of the system and the water in oil (W/O) emulsion system formed. The temperature at which phase inversion occurs is known as phase inversion temperature or HLB temperature. At this point of temperature, the system is rapidly cooled with stirring, to form O/W nanoemulsions with very fine oil droplets [15–17].