| Fluorescent silicon nanoparticles(SiNPs)featuring strong stable fluorescence and benign biocompatibility,have been intensively exploited for various bioapplications including bioimaging,biosensing,durg delivery,and so forth.Herein,we design and fabricate fluorescent SiNPs for biomedical applications,and carry out biosafety assessment of SiNPs is performed in various animal models,especially in non-human primate animals that are more clinical relevant.Corresponding research content mainly includes:fabrication of fluorescent SiNPs-based gene carriers and tracking of their intracellular behaviors;development of traditional Chinese medicines(TCMs)(i.e.,plumbagin)-assisted chemical synthesis of fluorescent anti-cancer SiNPs and their use for fluorescence tracking and treatment of tumors;employment of fluorescent SiNPs for naked-eye visible fluorescence-guided sentinel lymph node(LN)detection and excision;evaluation of in vivo biosafety of SiNPs in various kinds of animal models(i.e.,covering from rat,rabbit to Cynomolgus monkey).The main research strategies and results are briefly demonstrated as following:Chapter 1:We first give a brief introduction of silicon nanomaterials and their recent progresses in biological and biomedical applications.Then,we summarize representative synthetic strategies for preparing fluorescent SiNPs.Afterwards,we illustrate typical examples of SiNPs-based bioimaging and cancer therapy,and recent efforts in evaluating the biosafety of fluorescent SiNPs.We further discuss challenges and opportunities in the field of SiNPs-based biomedical applications.Finally,we provide an overview of proposal significance and novelty of our current research.Chapter 2:Taking advantages of the unique optical properties of SiNPs and favorable biocompatibility of cationic protamine sulfate,we present a novel kind of fluorescent SiNPs-based gene carriers.The resultant gene carriers can effectively bound plasmid DNA(pDNA)via electrostatic interactions,delivery pDNA into cellular interior,and promote efficient expression of pDNA.By tracking the strong and stable fluorescence of SiNPs,we elucidate intracellular behaviors of the resultant fluorescent SiNPs-based gene carriers,revealing the association between their structural fabrication and corresponding transfection efficiency.We reveal that the SiNPs-based gene carriers with a PS/pDNA ratio of 40 show lysosomal escape accompanied by pDNA dissociation in the perinuclear region,thus yielding maximum transfection rate(~35.8%).Moreover,toxicity assessment further demonstrates minimal cytotoxicity of the as-prepared SiNPs-based gene carriers.Chapter 3:We synthesize a novel kind of biofunctional and fluorescent SiNPs under microwave irradiation(reaction temperature and time:100 ~oC,10 min),by using TCMs(i.e.,plumbagin)and silane as reaction precursors.The resultant SiNPs simultaneously exhibit good dispersibility in water,strong fluorescence and robust photostability(i.e.,preserve~80%of the initial intensity after 180-min continuous UV irradiation).In addition,the SiNPs feature intrinsic anti-cancer efficacy with excellent selectivety towards cancer cells.Taking advantages of these unique merits,we further employ the presented SiNPs for simultaneous fluorescence tracking and treatment of tumors.Chapter 4:Benefiting from excellent optical properties of fluorescent SiNPs,we employ the fluorescent SiNPs probes for real-time visualization of detection and precise excision of sentinel LN.Compared to clinical near-infrared(NIR)lymphatic tracers based on indocyanine green(ICG),we demonstrate that SiNPs possess unique advantageous in water dispersibility,storage and fluorescence stability,as well as enhanced LN retention time.Moreover,the NIR fluorescence(emission wavelength:~795-845 nm)of ICG could not be directly observed by naked eye,and additional imaging equipment and relatively complicated procedures are thus required for the surgery.Comparatively,naked-eye visible fluorescence-guided surgical operation can be readily carried out through monitoring strong and stable green fluorescence(emission wavelength:~475-600 nm)of SiNPs.The whole surgical procedure can be readily performed with naked eyes by using a portable UV lamp.Therefore,lymphatic drainage patterns can be vividly visualized in real-time manners,and sentinel LN can be sensitively detected and precisely excised from small-(e.g.,rats and rabbits)to non-human primate-animal(e.g.,cynomolgus macaque and rhesus macaque)models,provingthefeasibilityandavailabilityofSiNPs-basedfluorescence visualization-guided surgical operation.After the surgery,no abnormal behaviors of the post-operative animals are observed and physiological indicators are within the normal ranges,indicating the healthy condition of the animals during the whole surgery.Chapter 5:In this chapter,by using various animal models(i.e.,covering from rats and rabbits to cynomolgus macaque and rhesus macaque models),we evaluate the in vivo toxicity of fluorescent SiNPs.Particularly,in rat models,SiNPs are mainly distributed in liver and kidney,and then gradually cleared from body through renal excretion,as indicated the fluorescence imaging of urine samples.Typical complete blood count,serum biochemistry indicators and histological analysis demonstrate that there is no overt toxicity of SiNPs in rabbits and monkeys even at long-time exposure time(>180 days).In summary,we develop SiNPs probes with unique optical properties and benign biocompatibility,and explore their potential use in biology and biomedical applications.Meanwhile,systematic assessment of in vivo toxicity of SiNPs is carried out in various animal models,covering from small-animal(i.e.,rats and rabbits)and non-human primate-animal(cynomolgus macaque)models,demonstrating the low-/non-toxicity of SiNPs.Our research provides valuable information for designing high-quality fluorescent SiNPs probes and facilitating the promotion of SiNPs-based widespread applications in biological and biomedical fields. |
