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Host Response to Biomaterials
Published in Claudio Migliaresi, Antonella Motta, Scaffolds for Tissue Engineering, 2014
Sangeetha Srinivasan, Julia E. Babensee
In the classical pathway, the complement fragment C1q attaches to pathogens primarily by the binding to the Fc portion of opsonizing antibodies. Also, the C1q component can directly bind to pathogens by diverse mechanisms such as binding to C-reactive protein and polysaccharides expressed by pathogens.71 In the alternate pathway, spontaneous cleavage of C3 results in opsonization of pathogens, by covalent binding of C3b specifically to hydroxyl groups on surfaces.72 Endogenously secreted C3b can also bind to host cells; however, cell surface-bound complement regulatory proteins such as CD46, CD55, and CD59 block the host cell death.73,74 Further, the alternative pathway offers an amplification loop to strengthen the initially weak signals.75,76 Activation of the classical or lectin pathways results in the breakdown of C4 into C4a and C4b. Complement component C4b is capable of opsonizing pathogens by covalently binding to cells through hydroxyl, amides, or carbohydrate moieties.77
Indocyanine green-loaded exosomes for image-guided glioma nano-therapy
Published in Journal of Experimental Nanoscience, 2022
Bo Fan, Song Yang, Yuan-yu Wang, Chao Zhang, Ji-peng Yang, Li-qun Wang, Zhong-qiang Lv, Xue-fang Shi, Zhen-zeng Fan, Jian-kai Yang
There are three advantages of ICG-loaded exsomes over traditional liposome ICG. Compared with existing artificial liposomes, good biocompatibility is one of its advantages as drug carriers. Currently, liposomes are the primary delivery device for siRNA and other RNAs, which can cause toxic immune responses in the human body and cause accumulation of toxicity to organs such as liver, eventually unsatisfied outcome. Exosomes have better biocompatibility and can overcome the shortcomings of liposome-induced immunogenicity and accumulated toxicity in vivo. Another advantage of exosomes as drug carriers is their biological stability. Antigen-presenting cell-derived exosomes can express membrane-bound complement regulators CD55 and CD59 to enhance the stability of circulation in vivo. Previous studies have shown that exosomes have a longer circulating time in vivo even when exposed to inflammatory conditions [24]. Numerous studies have demonstrated that nanoparticles can achieve targeted aggregation to tumor tissue through enhanced penetration and retention (EPR) due to their small size (≤100 nm). The size of exosomes is between 30 and 100 nm, and the targeting effect on tumor tissue also follows the EPR effect [25]. Moreover, certain cell-derived exosomes have intrinsic targeting functions. For example, exosomes derived from central nervous cells can cross the blood-brain barrier and target specific neurons [26]. Exosomes derived from hypoxic tumor cells are prone to be recruited into hypoxic tumor tissues [27]. The results of biodistribution studies also showed that the accumulation of exosomes in tumor tissue depending on the parent cell type. Therefore, when studying exosomes that target specific tissues or cells, it is necessary to consider the effect of their source cells on the targeting efficiency.