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Nanomaterials in Chemotherapy
Published in D. Sakthi Kumar, Aswathy Ravindran Girija, Bionanotechnology in Cancer, 2023
P. K. Hashim, Anjaneyulu Dirisala
Hydrophilic drugs such as small molecules and biomolecules (e.g., nucleic acid and protein) can be loaded into the aqueous interior of liposomes, while hydrophobic (lipophilic) drugs are placed within the lipid bilayer. This is usually conducted during the preparation steps of liposomes, also known as ‘passive loading’. In a typical liposome preparation process by Bangham method or thin lipid film hydration method [74], a mixture of lipids and cholesterol in organic solvents first evaporated followed by a freeze-drying procedure to form a thin film in a round-bottom flask. Upon the addition of aqueous solvents, rehydration takes place producing a multilamellar vesicle (MLV) or a giant unilamellar vesicle (GUV) [75]. To achieve small unilamellar vesicles (SUVs) with homogeneous size distribution, an additional sonication or multiple extrusions through a polycarbonate membrane is necessary [76–78]. Advanced techniques using microfluidics have recently been introduced to prepare mono-disperse liposomes. A notable example is a micro hydrodynamic focusing method proposed by Jahn et al. where a flow of phospholipids in an organic phase diffuse to an aqueous laminar flow, perpendicular to each other, causing the phospholipids to assemble into liposomes [79]. In ‘passive loading’, the degree of drug loading may depend on the type of lipids, type of drugs, liposome composition, as well as preparation methods [80, 81].
Tissue Engineering of Articular Cartilage
Published in Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi, Articular Cartilage, 2017
Kyriacos A. Athanasiou, Eric M. Darling, Grayson D. DuRaine, Jerry C. Hu, A. Hari Reddi
A major concern with rotating bioreactors is the random motion of scaffolds in the culture vessel. Generally, multiple constructs are cultured in a single bioreactor, which results in groups of tumbling samples that can collide into one another or into the walls of the bioreactor. These unpredictable collisions can kill cells or damage the scaffold during early culture periods. Another difficulty is identifying the flow patterns within a bioreactor filled with constructs. One attempt to localize the nutrient flow and keep a more stable culturing environment is the hydrodynamic focusing bioreactor, created by National Aeronautics and Space Administration to simulate a no-gravity cell culture (Figure 4.42) (Tsao et al. 1994, 1997; Tsao and Gonda 1999). As with other rotating bioreactors, the inner and outer walls rotate to produce a range of shear forces. However, instead of having a cylindrical shape, the hydrodynamic focusing bioreactor is a dome. This modification is proposed to focus cells and nutrients together to enhance mass transfer. Another version of the rotating bioreactor is the “rotating shaft” bioreactor (Chen et al. 2004). This device uses the motion of the inner cylinder to move attached samples in a continual rotary motion around the central axis. However, the culture vessel is only half-filled with medium, so samples move in and out of the liquid. This is proposed to increase oxygenation as well as provide slightly higher levels of shear.
Routine and Special Techniques in Toxicologic Pathology
Published in Pritam S. Sahota, James A. Popp, Jerry F. Hardisty, Chirukandath Gopinath, Page R. Bouchard, Toxicologic Pathology, 2018
Daniel J. Patrick, Matthew L. Renninger, Peter C. Mann
Flow cytometry requires cells in suspension, such as whole blood or bone marrow, or cells from solid tissue fine-needle aspirates or biopsies (e.g., lymph node, spleen, or thymus) in which the cells are mechanically or enzymatically dissociated. These cells are passed through a fluid sheath sleeve to create laminar flow; and by hydrodynamic focusing, a column of single cells are passed through a laser beam (or beams). At the point of intersection between the cells and the laser beam, known as the interrogation point, forward scatter light and side scatter light from each cell are collected by detectors. Side scatter light also passes through a number of dichroic mirrors with fluorescent detectors so that multiple wavelengths of emitted fluorescent light can be simultaneously detected. Care must be taken to make sure that the correct excitation sources with wavelengths compatible with particular fluorescent probes are used to avoid spectral overlap and reduce potential compensation issues. The detected light can then be digitized, analyzed, and graphically displayed by a computer. The data can be plotted in a single dimension to produce a histogram or in two-dimensional dot plots. The distribution regions representing populations of cells on these plots can be isolated by applying an electronic “gate” to isolate the cell populations of interest, which can simplify and increase the relevance of the statistical analysis. Once a cell population has been classified, statistical analysis to determine test article–related effects can be accomplished by various statistical methods. Critical controls include unstained cells, matching isotype controls, compensation controls, and biologic controls, including a known positive, if available.
Feasibility of a mean platelet volume standard: an international council for standardization in hematology (ICSH) inter-laboratory study
Published in Platelets, 2022
Paul Harrison, Joshua Price, Marie Didembourg, Alan Johnson, Samuel Baldwin, Marcel Veronneau, Daniel Baertlein, Xiaoyong Shi, Samuel Machin
In the 1950s, the discovery of the “Coulter” aperture impedance principle revolutionized particle counting and led to the invention of automated blood counters [1,2]. Hematology laboratories could soon produce blood counts very efficiently with improved accuracy and precision [3,4]. Hydrodynamic focusing coupled with the use of pulse shape analysis eventually enabled platelet measurements to also be performed in whole blood samples. The evolution of modern full blood counters is still continuing and the full blood count including red blood cell (RBC) and platelet counts remains the most commonly used pathology test [5–7]. Mean platelet volume (MPV) and RBC mean cell volume (MCV) therefore became additional parameters of interest to both clinicians and researchers and are routinely available within most modern analyzers. Changes in MPV and MCV are usually associated with thrombocytopenia [8,9] and anemia, respectively [10]. Instrument calibration for MPV is independent of their calibration for MCV and is most often established with a suspension of various size latex beads. However, unlike MCV [11], MPV analysis is still not subject to specific calibration and standardization guidelines. MPV normal values therefore can vary widely between 6.0 and 13.2 fL [12,13].
Microfluidics in drug delivery: review of methods and applications
Published in Pharmaceutical Development and Technology, 2023
Mutasem Rawas-Qalaji, Roberta Cagliani, Noor Al-hashimi, Rahma Al-Dabbagh, Amena Al-Dabbagh, Zahid Hussain
Many techniques have been used to generate liposomes, but the integration of microfluidic devices has aided in forming monodispersed liposomes with less time and the number of steps (Meure et al. 2008). The droplet-based microfluidic method is a very common method used utilized to generate liposomes (Teh et al. 2008). It is based on manipulation of two immiscible phases that produces micrometer to nanometer-sized droplets, and usually it will be in form of W/O emulsions. The generation of liposomes that have size less than 100 nm requires flow-focusing device with a pressure-controlled system (Damiati et al. 2018). Another microfluidic method can be used to generate liposomes which is continuous flow method. This method uses microfluidic hydrodynamic focusing.