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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].
Magnetic Nanoparticles: Challenges and Opportunities in Drug Delivery
Published in Jeffrey N. Anker, O. Thompson Mefford, Biomedical Applications of Magnetic Particles, 2020
Allan E. David, Mahaveer S. Bhojani, Adam J. Cole
The primary components of the MPS include opsonin proteins circulating in the blood, macrophages, and cells in the liver, spleen, and bone marrow. Opsonins are a group of proteins (including certain antibodies) circulating in the blood stream that make foreign bodies more susceptible to phagocytosis by macrophages. Macrophages, derived from Greek words meaning “big eaters,” are a type of white blood cell that ingest and then digest foreign particles and microorganisms. MNPs that enter the blood stream are coated by opsonin proteins and then taken up by activated macrophages. In general, particles with highly charged surfaces are more quickly adsorbed from plasma and, thus, display substantially shorter circulation times when compared to neutrally charged MNPs (Chertok, David, and Yang 2010).
In Vivo Targeting of Magnetic Nanoparticles
Published in Nguyễn T. K. Thanh, Clinical Applications of Magnetic Nanoparticles, 2018
Laurent Adumeau, Marie-Hélène Delville, Stéphane Mornet
For in vivo application, noncontrolled adsorption on the NP surface is an important issue. In the blood, administered NPs are exogenous materials liable to be eliminated by the immune defence system, which represents one of the major barriers for systematically administered nanomedicines. Opsonins are plasma biomolecules, in particular immunoglobulin and proteins of the complement, marking antigens and promoting their phagocytosis. Adsorption of opsonins onto the surface of NPs, a process termed as opsonisation, enhances the recognition and uptake of these NPs by the macrophages belonging to the reticuloendothelial system (RES), present in the liver (Kupffer cells), in the spleen and in the bone marrow. This opsonisation leads to the rapid clearance of the nanomaterials from the vascular compartment. Such an effect can be advantageous when these organs are the intended target sites, while in the other case, it may limit the NP delivery to the targeted zone.116
Stealth PEGylated chitosan polyelectrolyte complex nanoparticles as drug delivery carrier
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Xingyue Deng, Jing Zhao, Kaiwen Liu, Chao Wu, Fei Liang
Blood circulation half-life of nano drug carrier can be prolonged by escaping recognition and clearance of immune system after grafting stealth coating with no affinity for opsonin onto the surface of nanoparticles [7]. Nanoparticles can be coated with hydrophilic stealth polymers, surfactant or biodegradable copolymers, such as poly(ethylene glycol) (PEG), poly(ethylene oxide), polloxam and so on [8,9]. In addition, biomimetic strategies including cell-membrane camouflaging and CD47 functionalization are also used for the development of stealth nano-delivery systems [10]. The most widely used ‘stealth’ polymer in drug delivery is PEG, due to the properties such as biocompatibility, hydrophilicity, electroneutral, low interfacial free energy, steric hindrance effect and high flexibility [11,12], which has been approved for use in various drug formulations by US Food and Drug Administration (FDA) [13,14]. PEGylation of nanoparticles which can be ‘stealth’ or ‘invisible’ to macrophages is highly effective approach for drug delivery and cancer therapy [15,16]. It has been accepted as a general strategy to evade clearance by the MPS and prolong blood circulation time, ranging from a few minutes to a few days [17,18]. Researches have shown that PEGylated nanoparticles can prevent conditioning of blood components and other serum, avoid immunological recognition and improve the biodistribution [19]. Klibanov et al. demonstrated PEGylated liposomes have increased the blood circulation time from 30 min to up to 5 h [20]. Vertut Doi [21] found that the binding capacity of 5 mol% PEG grafted on liposome surface was 30% lower than that of unmodified liposome on J774 cells. Bonfa [22] systematically studied the effect of PEG modification on the adsorption of PMMA nanoparticles. Essa [23] studied the effect of PEG graft density on the long-term cycling performance of PLA nanoparticles, and the study showed that PEG graft density was 4%–7% when it was the most suitable for drug delivery system as stealth nanoparticles.