Biomaterials For Drug Delivery And Biosensor Construction

Nanomaterials are widely used in the fields of clinical diagnostics, drug analysis, energy, catalysis, and the environment, due to its small sizes, large surface areas, easy modification, the unique physical and chemical properties, biocompatibility, etc. Application of biological nanomaterials has become a hot issue. Searching biomaterials of novle biocompatibility that can be used biological imaging, drug delivery, gene therapy are researchers’goals. Based on these background, this dissertation focus on the appliction of nanomaterials in drug and gene delivery, and the use of nanoparticles to build sensor for detecting cancer markers, including proteins and RNA. The main contents are as follows:1. pH-Sensitive Polydopamine Nanocapsules for Cell Imaging and Drug Delivery Based on Folate Receptor TargetingMultifunctional polydopamine-based nanocapsules were easily prepared via a bioinspired, template assisted method, and further used as a robust platform for simultaneous cell imaging and drug delivery. A pH-triggered drug delivery system that can specially target to folate-receptors-overexpressing cancer cells was designed based on newly developed polydopamine capsules and folic acid. The polycapsules bioconjugates possess capabilities of high drug loading, enhanced folate-receptor-mediated cell uptake, and sustained drug release by intracellular pH changes. It was also found that the sustained release of drugs significantly increased reactive oxygen species (ROS) level in targeted cells. The efficient cell-specific endocytosis and intracellular pH-responsive controlled drug delivery of the capsules is promising for future in vivo therapeutic application.2. Highly Dispersible PEGylated Graphene/Au Composites as Gene Delivery Vector and Potential Cancer Therapeutic AgentGraphene/Au composites with a high positive charge, which is advantageous for the binding and condensation of negatively charged siRNA, are synthesized via an in situ reduction method, using PEI as a reductant and protective reagent. Owing to the sufficient amounts of amino groups, PEI-grafted graphene/Au composites can be further modified with methoxyl-PEG to acquire low cytotoxicity, novel blood compatibility, and optimal dispersibility in physiological environments. The obtained PEGylated PEI-grafted graphene/Au composites (PPGA) allow efficient loading of siRNA, forming PPGA/siRNA complexes to transport into HL-60 cells and downregulated anti-apoptosis Bcl-2 protein, indicating PPGA is a suitable platform for gene delivery. Moreover, PPGA display an enhanced photothermal response with respect to PPG under NIR laser irradiation, suggesting that PPGA can be used as an efficient photothermal agent.3. Bimetallic Pd-Pt Supported Graphene Promoted Enzymatic Redox Cycling for Ultrasensitive Electrochemical Quantification of MicroRNA from Cell Lysates.MicroRNAs (miRNAs), small endogenous noncoding RNAs with approximately 22 nucleotides, have attracted numerous researchers’ attention due to their important roles in a variety of biological processes such as cell differentiation, apoptosis, proliferation,and immunological response. Recently, miRNAs have emerged as new candidate diagnostic and prognostic biomarkers for detecting a wide variety of cancers. A great challenge for quantitative miRNA analysis is high sequence homology among family members. A novel electrochemical biosensor with triple signal amplification for the ultrasensitive detection of miRNA was developed based on phosphatase, redox-cycling amplification, bimetallic Pd-Pt supported graphene functionalized screen-printed gold electrode, and two stem-loop structured DNAs were used as target capturers. A proportional relationship was observed between the logarithm of target let-7b concentration and the DPV peak currents in a linear range from 10 fM to 0.1 nM with a detection limit of 3.55 fM. At the same time, this proposed biosensor is sufficiently selective to discriminate the target miRNA from homologous miRNAs and non-complementary miRNAs due to the loop-stem structure of capture probes and T4 DNA ligase. Therefore, this biosensor is an attractive candidate for the development of an accurate, selective, and ultrasensitive method for miRNA expression profiling and clinical diagnostics.4. Attomole Sensitive Electrochemical Detection of microRNAs Based on Metal Ion Functionalized Titanium Phosphate NanospheresMicroRNAs have the potential to be used as biomarkers for diagnosis and prognosis of cancer and attract more and more attention. Herein, a novel electrochemical genebiosensor was developed for ultradetection of miR-21 by using metal-ions functionalized titanium phosphate nanospheres as labels and Ru(NH3)63+ as electron transfer bridge. The metal ions could be detected through square wave voltammetry (SWV). The large amount of metal ions loading on the TiP nanospheres greatly amplified the signals and the Ru(NH3)63+ improve the electon transfer rates to enhance the electrochemical signals. A proportional relationship was observed between the logarithm of target miRNA-21 concentration and the peak currents in a linear range from 1 aM to 10 pM with a detection limit of 0.76 aM. The propsed biosensor owns a high sensitivity, specificity and is applicable to quantify miRNA in cell lyates.5. N-Acetylglucosamine Biofunctionalized CdSeTe Quantum Dots as Fluorescence Probe for Specific Protein RecognitionHsp70 proteins are implicated in resistance to chemotherapy in cancers, the detection of which is important for cancer treatment and prognosis. In this work, we report the study on the detection of specific intracellular target protein in fixed cells using GlcNAc-conjugated CdSeTe QDs. The QDs were coupled with Con A via a carbodiimide reaction and then were further assembled with GlcNAc by lectin-carbohydrate interaction between Con A and GlcNAc. The obtained QDs-Con A-GlcNAc conjugates have an emission wavelength at 650 nm that is close to the near-infrared (NIR) regions and a specific recognition for Hsp70. These results show that the QDs-Con A-GlcNAc probe can be a promising tool for direct localization of the Hsp70 protein.