Abstract
In recent decades, nanoscience has been involved in a variety of practical applications due to unique properties resulted from nanoscale dimensions. Surface functionalization by chemical and physical modification further improved the performance of nanomaterial and its applications in a diverse area. The works presented in this thesis focuses on fabrications of functionalized nanoparticles for biodetection, bioseparation and hybrid nanomaterial synthesis. Because of the specific affinity between lectin (carbohydrate-binding protein) and saccharides, we developed three fast and sensitive methods for detecting lectins through glyco-gold nanoparticle (AuNPs) mediated agglutination. On account of the structure, saccharide density and the length of linker between the binding ligand (saccharide) and nanoparticle can affect the stability of AuNPs in buffered saline and modulate the overall binding affinity toward lectins, a detailed study has been conducted for synthesis of stable AuNPs. We discovered that AuNPs covered by 70% of saccharide with linker constructed from six ethylene glycol unit and a ten saturated carbon length (EG6C10) gave the best stability under high salt conditions (600 mM NaCl). Based on the EG6C10 structure, 7 different AuNPs functionalized by mono-, di- and trisaccharide were synthesized and used to form aggregation in the solutions with target lectins. UV-Vis and dynamic light scattering measurements were utilized as readout of the shifts of absorption and the changes of the mean hydrodynamic diameter (DH), respectively, to monitor the extent of AuNPs aggregation. Furthermore, lectin-glyconanoparticle complex captured by a uniformly oriented antibody via boronate formation on microarray chip followed by silver stain permits the detection of the presence of target protein by naked eye. In these strategies, a detection sensitivity within the pico- to nanomolar range (pM - nM) is readily achieved, which are comparable with ELISA-based assays, and therefore, make them as attractive approaches for lectin-sensing applications. In addition, these strategies are rapid, and could be easily implemented and extended to a variety of other carbohydrate-binding proteins. On the other hand, AuNPs was functionalized by a molecular linker - thioctic acid (TA) and assembled uniformly on the surface of single-crystal ZnO nanorod arrays (ZNA) instead of the procedure to reduce metal salt precursor, which gave poor control of size and shape. The size and loading of AuNPs on ZNA can be easily controlled synchronously in large scale by this synthetic methodology, which are key factors for improving the photocatalytic activities. In the photodegradation study of decomposing rhodamine B dye (RhB), which serves as an example of pollutant in water, 10 nm AuNPs decorated ZNA exhibits the highest photoreaction rate (8.5-fold enhancement compared to bare ZNA) under UV irradiation among 5 different size of AuNPs. Also, the degradation efficiency was found to be proportional to the loading amount of the AuNPs on the ZNA. The high photodegradation rate demonstrated in this study indicated that the ZNA-AuNPs heterostructures are promising candidates for the next-generation photocatalysts. At last, magnetic nanoparticles (MNPs) functionalized by boronic acid (BA@MNPs) through amide bond formation, microwave-assisted CuAAC reaction, sol-gel process, and RAFT polymerization were synthesized successfully. Based on the FTIR semi-quantitative analysis, BA@MNPs synthesized from CuAAC and RAFT polymerization approaches have shown stronger signal of BA molecule, indicating the better efficiency of immobilization on nanoparticle surface. Quantitative analysis of BA molecule on the MNPs surface and evaluation of BA@MNPs as extracting agent to capture and enrich glycoproteins are being progress.