The Biological Effect Investigations And Bioimaging Of Fluorescent CdTe Quantum Dots And Silicon Nanoparticles In Living Organisms

With the rapid development of nanotechnology,numerous nanomaterials have been created for various applications.In particular,fluorescent nanoparticles such as II-VI semiconductor quantum dots(QDs)and fluorescent silicon nanoparticles(SiNPs)have been exploited as fluorescent probes for various biological and biomedical studies.A consensus has been reached that before wide-ranging bioapplications of nanomaterials,their biosafety assessment is essentially required for investigating in systematic manners.Caenorhabditis elegans(C.elegans)and Bombyx mori are two classic model organisms that have been extensively used in various biological and biomedical studies due to their several unique merits,including low maintenance cost,ease of manipulation,short generation time,well-defined anatomical features and well-characterized genetic background,etc.In this dissertation,utilizing C.elegans and Bombyx mori as animal models,we investigate the phenomenon and mechanism of autophagy induced by CdTe QDs in live organisms,the in vivo behavior and toxicity of CdTe QDs and SiNPs,as well as the in vivo imaging of SiNPs,which help us understand the relationship between nanomaterials and living organisms in vivo level.The main research results are as follows:Chapter 1:In this chapter,we give an introduction to the recent research progresses of CdTe QDs-and SiNPs-based nano-biotechnology,and discuss the objectives and methods of the study in this dissertation.Chapter 2:In this chapter,we systematically investigate the CdTe QDs-induced autophagy in live organisms.Our results demonstrate that the internalized CdTe QDs trigger a complete autophagic process in C.elegans intestinal cells.Further investigations reveal that the observed CdTe QDs-induced autophagy in C.elegans is neither a response to released heavy metal ions by the CdTe QDs,nor an attempt to engulf exogenous CdTe QD materials,but a defensive strategy of the organism to clear and recycle damaged endosomes.Chapter 3:C.elegans is employed as a platform to systematically investigate the in vivo toxicity of SiNPs in live organisms from the whole-animal level to the molecular level.Our studies show that SiNPs have no significant effect on development,life span or reproductive ability,even when the worms are treated with a high concentration(e.g.,50 mg/mL)of SiNPs for all growth and development stages.Subcellular analysis of the SiNPs-treated worms reveals that the intracellular processes of the C.elegans intestine are not disturbed by the presence of SiNPs.Toxicity analyses at the molecular level also reveal that the SiNPs do not induce harmful or defensive cellular events,such as endoplasmic reticulum stress,mitochondria stress and oxidative stress.These findings altogether suggest the fluorescent SiNPs as promising fluorescent nanoprobes with negligible toxicity.Chapter 4:we herein choose C.elegans as an animal model to investigate the in vivo behavior and imaging of fluorescent SiNPs.Our studies show that SiNPs are easily incorporated into the tissues and cells of the live C.elegans.The internalized SiNPs display uniformed distribution and limited diffusion ability in vivo,and possess good biocompatibility and photostability in live organisms.Furthermore,Arg-Gly-Asp(Arginine-Glycine-Aspartic acid,RGD)peptides-modified SiNPs(SiNP-RGD)can specifically label muscle attachment structures in live C.elegans.These findings provide feasibility of long-term and real-time bioimaging by using the SiNPs-based fluorescent probes.Chapter 5:Bombyx mori is utilized as an animal model to investigate the in vivo behavior and toxicity of CdTe QDs and SiNPs.First,the CdTe QDs in the hemolymph are transported concomitantly to the floating tissues,leading to obvious toxicity.We find that amino acids linked to CdTe QDs significantly increase the targeted transfer efficiency and biological safety in Bombyx mori.The reactive oxygen species(ROS)induced by amino acids-modified CdTe QDs decreases in visceral tissues,thus reducing the toxicity of CdTe QDs.Second,our study shows thdifferent types of circulating hemocytes and their impact on those hemocytes differs at the ability of SiNPs to enter significantly.The SiNPs that entered the hemocytes initiate apoptosis via the lysosomal pathway.And we further find that the damage caused by high-dose SiNPs to hematopoiesis is self-healing.These studies are helpful for understanding the in vivo biological effects of CdTe QDs and SiNPs.In summary,this thesis demonstrates a relatively comprehensive investigation of the biological effects and bioimaging of CdTe QDs and SiNPs in living organisms,i.e.,the in vivo behavior and toxicity of CdTe QDs and SiNPs,and the biological imaging application of SiNPs.Our results provide invaluable information for safety evaluation and bio-application of CdTe QDs and SiNPs.