Research group of Professor Xiao Lehui of Nankai University: using single particle optical microscopy to explore the uptake mechanism of nanoparticles in different dimensions at the living cell level

Due to its unique size, good biocompatibility and easy functionalization, lead nanomaterials have been widely concerned in the past decades Especially in the field of biology, they can integrate imaging, biomarker, treatment and other means to form a new delivery system combining diagnosis and treatment However, the interaction between nano materials and cells and the phagocytosis mechanism involved have not been fully and systematically studied, which greatly limits the development of efficient nano delivery system Recently, the research team of Professor Xiao Lehui of Nankai University has made a new breakthrough in this field, and explored the uptake mechanism of nanoparticles of different dimensions (DOI: 10.1039/C8SC01828F) at the living cell level by using single particle optical micro imaging technology Professor Xiao Lehui's research group introduces that Professor Xiao Lehui's research group currently has 4 doctoral students and 6 graduate students The research group is mainly engaged in single molecule detection, single particle spectral analysis and single cell imaging research The research group is committed to taking functional nanomaterials or organic molecules as probes, based on the high sensitivity and high-throughput detection and analysis ability of optical microimaging technology, and through the development of a series of advanced imaging technology, to conduct detailed research on the basis and difficult problems in current chemical biology, analytical chemistry and photophysical chemistry At the level of single molecule and single particle, the research group intends to explore the photophysical properties of functional materials, the self-assembly mechanism of molecules, the pathogenic causes of major diseases, etc., so as to provide reference for solving the above problems; at the level of living cells, the research group intends to explore the interaction mechanism of functional nano materials and cells, establish an efficient means of drug transport, provide orientation Controlled and convenient drug release methods, which provide effective strategies for the early diagnosis and treatment of major diseases Prof Xiao Lehui, distinguished researcher of School of chemistry, Nankai University, doctoral supervisor, winner of National Excellent Youth Fund In 2011, he received his Ph.D in analytical chemistry from Hunan University From 2011 to 2012, he conducted postdoctoral research in Ames Laboratory of the U.S Department of energy and Washington University From 2012 to 2015, he was employed as a special professor of Xiaoxiang scholars of Hunan Normal University and a special researcher of the school of Chemistry of Nankai University since 2016 Fund review expert of NSFC, J am Chem SOC., anal Chem., chem Com And other international academic journal review experts At present, he has published more than 40 SCI papers in the journals of Annu Rev Anal Chem., angelw Chem Int ed., J am Chem SOC., nanoscale, anal Chem., biomaterials, chem SCI., J PHY Chem C Website of the research group: www.xiaolhlab.cn Cutting edge scientific research achievements: the research team of Professor Xiao Lehui of Nankai University has done a series of pioneering work around the synthesis and optical imaging of nano materials by using single particle optical microscopy and up conversion nano materials to reveal the uptake process of different dimensions of nano particles by cells In 2016, the group tripled the fluorescence intensity of the polymer point by crosslinking the PFBT polymer point on the surface of gold nanorods coated with silica The polymer can be used in fluorescence and dark field dual-mode single particle imaging, and has good application prospects in biological imaging such as biomarker and single particle tracking (anal Chem., 2016, 88, 6827-6835) In 2018, the research team obtained an ultra-small polymer point with positive charge by using fluorescent conjugated polymer and cationic lipid molecule, and then constructed a new intracellular imaging and gene transport system (nanotherapistics, 2018, 2, 157-167) Based on the microscopic imaging, the research group has also been committed to the study of the mechanism of nanoparticle cell invasion, and to explore the interaction between nanoparticle and cell membrane at the level of single particle and single cell As early as 2014, the research team studied the distribution of particles in cells and the mechanism of cell invasion through polypeptide modified nano gold (nanoscale, 2014, 6, 10207-10215) After that, the research team used single particle tracking method and dark field microscopy to further track the interaction process of gold nanoparticles coated with multi-functional peptides and artificial phospholipid bilayer membrane in real time (Annu Rev Anal Chem., 2014, 7, 89-111; anal Chem., 2016, 88, 11973-11977; anal Chem., 2016, 88, 1995-1999; Anal Chem ., 2018 , 90 , 1177-1185）。 Fig 1 (a) (b) SEM characterization and single particle fluorescence micrograph of ucnps with four different morphologies; (c) (d) fluorescence intensity distribution of ucnps with four different morphologies and change of single particle fluorescence intensity with time (source: chem SCI., 2018, DOI: 10.1039 / c8sc01828f) recently, based on the above work, the research team used a single particle optical microscope and a series of upconversion nanoparticles (ucnps) to reveal the uptake rule and phagocytosis mechanism of nanostructures with different morphology and surface charges Compared with other fluorescent nanomaterials, up conversion materials have the characteristics of low cytotoxicity, wide emission spectrum, high quantum yield and good fluorescence stability More importantly, upconversion materials can convert low energy near-infrared light into high-energy emission light, thus significantly reducing the self background of biological samples From this point of view, Professor Xiao Lehui's research group first took sodium citrate as the protective agent and NaYF 4 as the main material, and obtained a kind of ucnps-1 with good dispersion, excellent fluorescence performance and approximate 2D structure By changing the molar ratio of sodium citrate and rare earth elements in the synthesis process, the 2D nano sheet was gradually stretched, and three kinds of 3D nanostructures (ucnps-2, - 3, - 4) were formed Fig 2 the potential (A-D) and fluorescence intensity distribution (E-H) of four different morphologies of ucnps after polymer modification (source: chem SCI., 2018, Doi: 10.1039/c8sc01828f) considering that the surface charge of nanoparticles is one of the important factors affecting their cell phagocytosis, the author further modified three polymers (PAA, PVP, PEI) on the surface of nanomaterials, so as to give them different surface charges without changing the fluorescence performance (Fig 2) Fig 3 cell imaging of different polymer modified ucnps and HeLa cells cultured at 37 ℃ for 4 hours (source: chem SCI., 2018, DOI: 10.1039 / c8sc01828f) through co incubation of the above-mentioned modified series of ucnps with HeLa cells, and analysis of the obtained fluorescence micrograph (Figure 3), the author found that no matter how the shape changes, the positively charged nanoparticles are more likely to be phagocytized by cells However, with the surface charge unchanged, the smaller the size and the larger the specific surface area, the more nanoparticles enter the cell (FIG 4A) In addition, the author also found that with the change of material shape from 2D (ucnps-1) to 3D (ucnps-2), the uptake of positively charged nanoparticles by cells decreased only 11.6%, far lower than 43.5% of negatively charged nanoparticles; when the size further increased (ucnps-3 and ucnps-4), the difference of particles with different charges decreased Therefore, for small-sized nanoparticles, physical adsorption is the main driving force of their phagocytosis With the increase of particle size, the effect of electric charge is weakened, and the morphology of nanomaterials becomes the main factor affecting the phagocytic efficiency (Fig 4b) Fig 4 (a) (c) statistical chart of single cell intake of different polymer modified ucnps and HeLa cells after incubation at 37 ℃ and 4 ℃ for 4 hours (b) The proportion of the decrease of the intake of the cells with the increase of the size (for example, ucnps 12 represents the proportion of the decrease of the intake after the transformation of the shape of nanoparticles from ucnps-1 to ucnps-2) (d) The proportion of endocytosis in the uptake of different size positively charged ucnps (ucnps PEI) by cells (source: chem SCI., 2018, DOI: 10.1039/c8sc01828f) in order to further study the phagocytosis mechanism of cells to nanoparticles, the author also reduced the co incubation temperature of cells and nanoparticles to 4 ℃, thus inhibiting the energy-mediated phagocytosis process However, the results show that a small amount of nanoparticles still enter the cell at this time, indicating that the cell uptake process may involve a variety of complex mechanisms (Fig 4C) By introducing nest mediated endocytosis inhibitor genistein and grid mediated endocytosis inhibitor dynaosre, we found that the phagocytic efficiency of cells to nanoparticles was greatly reduced, which indicated that the phagocytic process of cells mediated by grid protein and nest was the main way for nanoparticles to enter cells, but at the same time, a small amount of fluorescence in cells also proved that other The presence of uptake pathways (Figure 5) Fig 5 statistical chart of single cell intake of positively charged ucnps (ucnps PEI) and HeLa cells with different sizes after incubation for 4 hours without drug treatment (red), with genistein (g) (green) and dynaosre (d) (purple) and with genistein and dynaosre (black) respectively (source: chem SCI., 2018, DOI: 10.1039/c8sc01828f) to sum up, based on a series of up conversion nanomaterials with different morphology and surface charges, with their excellent fluorescence performance and single particle optical microscopic imaging technology, the author has realized a comprehensive exploration of the factors affecting the phagocytic efficiency and phagocytic mechanism This research will provide new ideas and options for the design and development of nano carrier system in biomedical field This research achievement was recently published on Chemical Science (DOI: 10.1039 / c8sc01828f) under the title of "the mortgage and surface charge dependent cellular uptake efficiency of upconversion nanostructures revealed by single particle optical microscopy" The author of this paper is Di Zhang, Lin Wei, Mei Zhong, Lehui Xiao, * hung wing Li, and Jianfang Wang Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeango app, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.