Identification Of Dominant Physicochemical Properties Of GNPs In Evading Phagocytosis

It has been a long time that various nanomaterials are being applied in human society especially in health and medicine. Drug formulations based on nanomaterials always exhibit more efficiency than free drugs due to the special physic-chemistry characteristics of nanomaterials. For example, using nanocarriers to deliver hydrophobic drugs is able to improve the drug’s solubility and half-time in blood without decrease of drug activity. Furthermore, nanoparticles are very easy to be functionalized since they have severe large specific surface area, which is very important for nano drugs to acquire some special ability like targeting or penetrating.However, to immune-system, nanomaterials are foreign substances which can elicit immune-responses. Nanoparticles will be taken in by cells like macrophages and accumulate in organs like liver, kidney and so on. In this progress, not only the immune-response but also the nanoparticles’accumulation can induce significant damage to human body. In a word, the unsafety of nanomaterials to human body block the development of nano technology in medical science.Gold nanomaterial has been seeing as one of the most nontoxic nanomaterials. And it has already been applied in many areas like targeting delivery, photothermal therapy, disease diagnosis and so on. However, plenty of studies show that gold nanoparticles can also be swallowed significantly by macrophage and accumulate inside human organs. Furthermore, size and surface chemistry of nanoparticles are key factors to determine how much and in what way macrophages uptake gold nanoparticles. So we believed that finding the key surface chemistry through modified gold nanoparticles with ligands in different characteristics, more safety nanomaterials would be designed.Our study focused on how size and surface chemistry influence the progress of macrophages recognizing gold nanospheres and the corresponding phagocytosis. We designed a list of surface ligands and distinguish the surface chemistry to five types: charge, hydrophobicity, hydrogen bonding ability, pi-pi interaction density and steric hindrance. Through Transmission Electron Microscopy and Inductively Coupled Plasma Mass Spectrometry, we can know how and how much the macrophage uptake gold nanoparticles. The results showed that small particle was difficult to be recognized and swallowed by macrophages. We can also know the uptake variations when the surface ligands are changed. The results suggested that hydrophilic and negatively charged nanoparticles were not welcome by macrophages. The reasons underlying that would be that hydrophilic and negatively charged nanoparticles could not be recognized by identified receptors. Hydrophilic nanoparticles could not be recognized by scavenger receptors and hydrophobic proteins while negatively charged nanoparticles escaped the reorganization of scavenger receptors and mannose receptors.Our study showed how surface characteristics of gold nanospheres determine the reorganization and phagocytosis of macrophage and proved that hydrophobicity and charge are key factors to determine the phagocytosis progress. Our results are significantly important to understand the interactions between macrophages and nanomaterials.