The Study Of Endocytosis And Radiosensitization Of Nanoparticles Based On Scanning Ion Conductance Microscopy

Understanding cellular interaction of nanomaterials is pivotal for designing highly efficientfunctional biomaterials for cellular imaging,sensing,and delivery of biological/biomedicalsubstances.While various techniques have provided the biophysicochemical information of thebiological layer interfacing the surface of nanomaterials,limited knowledge is available about howthe live cell membrane interacts with and responds to extracellular nanomaterials at the early stage.In recent years,there have been exciting developments to turn sanning ion conductance microscopy(SICM)into a powerful multifunctional microscope for live cell studies.SICM techniques havebeen extended to map the electrical and electrochemical properties of a surface,along withtopography imaging.During nano-bio interactions,the electrostatic properties of cell membrane areexpected to be perturbed by the adsorption,interaction,and internalization of extracellularnanomaterials.It is of fundamental importance to understand the nano-bio interactions throughinvestigating corresponding electrical changes of cell membrane.In this thesis,the interaction between nanoparticles and cell membrane and the radiasensitizationof nanoparticles were studied.The main works are as follows:1)Using the newly-enabled multifunctional SICM,we observed the topography and potentialof sample surface.We used the multifunctional SICM to study the modified PDMS substrates,andstudied the topograpghy and surface potential of PDMS subtrates with different roufhness andcharges;and got more accurate results.2)The potential distribution pattern was investigated using a(Finite element based numerical)FEM for solving Poisson and Nernst–Planck(PNP)equations.PNP equations were fully coupledand solved using boundary conditions matching the expected experimental conditions.3)We used the SICM to study the interaction betwwen nanoparticles and cell membrane toobserve the dynamic process of endocytosis.In this report,two structurally similar conjugatedpolymer nanoparticles(CPNs)that have different functional groups(i.e.,primary amine versusguanidine)at the end of the side chain were used,providing opportunities to study functionalgroup-dependent cellular interaction and entry of CPNs.Using the newly-enabled surface potentialmapping capability of multifunctional SICM,we found that the topographic features exhibit eithermore positive potentials due to adsorbed/embedded CPNs on the membranes or more negativepotentials due to membrane deformation and transmembrane pore formations.Our results implythat the cells are able to survive the initial nano-bio interactions by self-repairing the damages(i.e.,nanocraters and pores)in the membranes and later become resilient to the same level of CPNinteractions,while conventional energy-dependent endocytoses become predominate after aprolonged CPN interactions when CPNs are still abundant in the extracellular environment.4)We studied the radiosensitization of two different nanoparticles after endocytosis.Nanomaterials have been used in conjunction with radiotherapy in order to enhance the sensitivity of cancer cells to the effects of radiation and reduce damage to surrounding tissue.In the present study,we synthesized cerium nanoparticles(CNPs)modified with neogambogic acid(NGA)and selenium nanoparticles(Nano-Se),researched the ability of NGA-CNPs and Nano-Se to enhance the radiation effect,and studied the mechanism of radiosensitization.