Fabrication Of Fluorescent Silicon Nanoparticles-Based Red Blood Cell Drug Delivery System And Evaluation Of Associated Toxicity

In recent years,enormous efforts have been made in developing silicon nanomaterials with unique physical/chemical properties,good biocompatibility,large surface-to-volume ratio and surface tailorability.Among them,fluorescent zerodimensional silicon nanoparticles(Si NPs)have attracted broad attention in biological and biomedical applications.In this study,fluorescent Si NPs-based red blood cell(RBC)drug delivery system(DDS)is fabricated.In addition,the toxicity and in vivo behavior of fluorescent Si NPs are investigated in a comprehensive and reliable manner.The main contents are as follows:Chapter 1: We give an introduction to the recent research progresses of cell membrane-based nanomaterials,silicon nanomaterials,their drug delivery application and biosafety assessments.Then,we discuss the objectives and methods of the studies in this dissertation.Chapter 2: The development,characterization and tumor cell killing effect of doxorubicin(DOX)-loaded Si NPs(Si NPs-DOX)impregnated into RBCs(Si NPsDOX@RBCs).Si NPs-DOX are encapsulated in RBCs by ‘dilutional hypotonic hemolysis method’.Importantly,the resulting DDSs exhibit bright fluorescence coupled with robust photostability(i.e.,~24% loss of fluorescent intensity after 25 min continuous laser irradiation)and significantly lengthened blood residency(i.e.,t1/2 = 7.31 ± 0.96 h).The release behavior of Si NPs-DOX@RBCs is relatively slow(35% of Si NPs-DOX is released from RBCs after 1 week).Furthermore,Si NPs-DOX@RBCs are employed for long-term and real-time imaging of living cells.In addition,Si NPs-DOX@RBCs show high killing ability of tumor cells(43.2% tumor cells survive under the concentration of 5 μg·m L-1 DOX).Chapter 3: Biosafety assessment of fluorescent Si NPs in vitro and in vivo.The in vitro studies suggest Si NPs have no distinct effect on cell viability,apoptosis and cell cycle.The biodistribution and clearance of intravenously injected Si NPs are investigated.Particularly,the Si NPs mostly locate in liver,kidney and spleen in short time postinjection.Afterwards,Si NPs are noticeably excreted through urine by renal metabolism(3 days),and then cleared from the body after 3 months.During this period,all indicators such as histopathology,hematology and body weight are within normal range,suggesting no obvious toxicity of Si NPs in vivo.In summary,we firstly develop Si NPs-DOX@RBCs with slow drug release profile and extended blood circulation time.Taking advantage of the optical properties of Si NPs,the intracellular behavior of Si NPs-DOX@RBCs is tracked in long-term and real-time manner.Secondly,we systemically investigate the toxicity and in vivo behavior of Si NPs.The biodistribution and biodegradation process in mice are studied.These results validate the low/non toxicity of fluorescent Si NPs.