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Constitutive Host Resistance
Published in Julius P. Kreier, Infection, Resistance, and Immunity, 2022
The process of preparation of a particle for ingestion by coating with serum protein is called opsonization. Opsonins are substances in the serum that coat particles and cause them to be engulfed by phagocytic cells. The most important of the opsonins in serum are antibodies, the C3b component of the complement system, and fibronectin (see chapter 4).
Dermal filler complications and management
Published in Michael Parker, Charlie James, Fundamentals for Cosmetic Practice, 2022
The complement system is comprised of approximately thirty proteins which are synthesised by the liver and are permanently in circulation in blood plasma. When complement proteins are triggered by microbial antigens, a cascade of events is initiated with the intention of destroying pathogens through phagocytosis, cytolysis and inflammation. Phagocytosis is triggered via a process called opsonisation, where opsonin proteins are used to mark infected or dying cells to be phagocytosed. Cytolysis occurs through the formation of the membrane attack complex (MAC) which effectively punches a hole within the plasma membrane of bacteria, causing them to rupture due to an inflow of extracellular fluid. Finally, inflammation is stimulated by the binding of complement proteins to mast cells to encourage them to secrete histamine which increases blood vessel permeability to allow cells of the immune system to extravasate and reach the target area.
Engineered Nanoparticles for Drug Delivery in Cancer Therapy *
Published in Valerio Voliani, Nanomaterials and Neoplasms, 2021
Tianmeng Sun, Yu Shrike Zhang, Pang Bo, Dong Choon Hyun, Miaoxin Yang, Younan Xia
When nanoparticles enter the plasma, opsonization (i.e., the adsorption of serum proteins) will occur immediately on their surfaces [5, 160a]. Through opsonization, foreign organisms or particles will be coated with nonspecific proteins known as opsonins to generate a corona and make the particles more visible to the phagocytic cells in the MPS. Opsonins typically contain complement proteins and immunoglobins (usually IgG) along with albumins, fibronectins, fibrinogens, and apolipoproteins [194]. Studies have shown that the corona has a layered architecture. It starts with an inner layer of proteins that strongly adsorb onto the surface, with Kd 10−6 to 10−8 m, to form the hard corona, which is then surrounded by a layer of soft corona formed by weak interactions [169, 195]. The primary driving forces for opsonization are based on hydrophobic and electrostatic interactions, together with entropic and conformational changes for the adsorbed proteins [196]. Depending on the charge and hydrophobicity of the nanoparticles, opsonization can occur within minutes. Experimental results suggest that a charged surface tends to be covered by proteins more rapidly than their counterparts with a neutral surface [160a].
Transferrin decorated PLGA encumbered moxifloxacin nanoparticles and in vitro cellular studies
Published in Drug Development and Industrial Pharmacy, 2023
Gayathri Aparnasai Reddy, Mayank Handa, Debapriya Garabadu, Ravindra Kumar, Pramod Kumar Kushawaha, Rahul Shukla
Polymeric NPs like PLGA, polycaprolactone, and poly lactic acid, when administered via the intravenous (IV) route, are rapidly uptake by the mononuclear phagocytic system (MPS). Furthermore, opsonin attachment on the surface of the NPs results in recognition by phagocytosis. It results in the elimination of NPs from the body due to the reticuloendothelial system (RES) when administered IV [16,19]. Hence, to prevent the rapid uptake by RES, PEGylation helps the NPs to escape from the RES system. Masking with PEG provides hydrophobicity to polymeric NPs by its adsorption on the surface of NPs. Moreover, delivering the drugs to the targeted site is desirable rather than the nonselective delivery of these cargos [20]. However, size of NPs plays a prominent role in RES uptake and inhibition. The size below 200 nm bypasses the RES and inhibits the need of PEGylation. To impart targeting to NPs, effective coating with ligands can be done.
Environmentally weathered polystyrene particles induce phenotypical and functional maturation of human monocyte-derived dendritic cells
Published in Journal of Immunotoxicology, 2022
Annemijne E. T. van den Berg, Maud Plantinga, Dick Vethaak, Kas J. Adriaans, Marianne Bol-Schoenmakers, Juliette Legler, Joost J. Smit, Raymond H. H. Pieters
PS particles injected intravenously are rapidly covered by blood proteins and the resulting protein biofilm has been shown to play an important role in particle–cell interaction, favoring their uptake (Lesniak et al. 2010; Tenzer et al. 2013; Schöttler et al. 2016). However, the influence of the blood-derived biofilm on MNP uptake by DC is still not well-investigated. The study here showed that pre-incubating the particles in HI human plasma significantly enhanced 0.2 µm PS particle uptake by MoDC. The uptake of 1 µm PS particles was reduced, whereas the uptake of 10 µm PS particles was only observed when the particles were pre-incubated in HI plasma. Heat-labile components of human plasma such as serum complement are not likely to be involved in the uptake observed in this study, as they were inactivated by heat-inactivation of the plasma. However, blood contains dozens of other proteins that can act as opsonins, facilitating uptake by phagocytes (Walkey et al. 2012). This highlights that the protein biofilm cannot be neglected when researching the uptake of MNP.
Lung macrophages: current understanding of their roles in Ozone-induced lung diseases
Published in Critical Reviews in Toxicology, 2020
Phagocytosis relies on cell surface receptors that have been evolutionarily selected to recognize particles including microbes, apoptotic and necrotic debris, and foreign abiotic substances. For example, antibody/complement-coated (opsonized) bacteria are recognized by Fc-gamma (Fcγ)/complement receptors (Allen and Aderem 1996). Ligand bound Fcγ/complement receptors signal substantial reorganization of the macrophage actin cytoskeleton, which, in turn, triggers the formation of membrane extensions called pseudopodia that surround and finally engulf recognized particles (Allen and Aderem 1996). Critical known receptors in opsonin-dependent phagocytosis include FcγRI (CD64), FcγRIIa (CD32), FcγRIIIa (CD16), FcαR1 (CD89), FcεR1, CR1 (CD35), CR2 (CD21), CR3 (CD11b/CD18 complex), CR4 (CD11c/CD18 complex), C5a (CD88), and surfactant protein A (SPA) (Gordon 2016; Rosales and Uribe-Querol 2017). In contrast to bacteria, environmental toxicants devoid of microbial contents are scavenged through scavenger receptors (Palecanda and Kobzik 2001). Mechanistically, these receptors scavenge inflammatory products, such as oxidized lipids, that are also potent neutrophil chemoattractants.