| Since Tomalia reported dendrimer polyamidoamine (PAMAM) in 1985, great attenation had been paid to PAMAM dendrimer due to its great potential appalication in many fields because of its well-defined structure, hollow cavities deep within the branching structure and high density of functional groups. However, it is difficult to obtain liquid dendrimers with high purity because both of the excessive raw materials and dendrimers are soluble in methanol and rotary evaporation method is not so effective. At the same time the liquid state limit the application of dendrimers. Immobilized dendrimers to the appropriate carrier can obtain dendrimers with high purity and the separation is very simple, meanwhile the application of PAMAM is expanded. Dendrimer-grafted silica is a type of organic-inorganic hybrid material which combins inorganic materials and the fascinating structural features of dendrimers, and it representes the combination of organic and inorganic.However, the conventional synthesis of PAMAM grafted silica requires a long reaction time, and new technology is needed to accelerate the reaction. Microwave radiation is a new technology rapid development and application in recent years. This technology has the significant advantages of heating reactants and solvents directly with no temperature gradient, fast heating, minimal hot vessel surface, high efficiency, greatly accelerating reactions, and improving reaction yields compared with traditional heating. Microwave technology was adopted for grafting of PAMAM dendrimer onto the surface of silica. The PAMAM was grown from amino groups on the colloidal silica surface by repetition of two steps:(1) Michael addition of methyl acrylate (MA) to amino groups on the surface and (2) amidation of the resulting terminal ester groups with ethylenediamine (EDA). Fluorescence microscopy, elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR) and titrimetry were used to characterize the structure and composition of the dendrimer-grafted silica surface. The results indicated that PAMAM were grafted successfully onto the silica surface with microwave assistance.PAMAM provides large amount of NH2 which bring different interactions with amino acids and proteins. Besides, the biocompatibility of PAMAM is excellent, so in this paper, the PAMAM grafted silica was apply to the immobilization of biological technology.Bovine serum albumin (BSA) was used as a model of biological molecule to react with the dendrimer-grafted silica by adsorption and chemical bonding through glutaraldehyde. The results showed that the immobilization efficiency for BSA increased with increasing PAMAM generation.The PAMAM grafted silica was used to immobilize aminoacylase. Immobilized enzyme technology was developed from the 20th century 60s. The advantages of immobilized enzymes over free enzymes include resuse, enhanced stability, rapid separation of the catalyst from the reaction mixture and reduced operation cost. The results showed that the immobilization efficiency for aminoacylase increased with the generation of PAMAM increasing and the immobilized enzyme remained high activity.The anti-epitestosterone monoclonal antibodies were immobilized onto the PAMAM grafted silica and prepared an off-line immunoextraction column. The column was employed to immunoaffinity extraction (IAE) of epitestosterone and testosterone from liquid sample. The immunoaffinity extraction is based on the specific interaction between antigen and antibody, therefore the target analytes are specific captured and enrich from complex sample matrices. The main advantages of IAE are the high sensitivity and exquisite selectivity. The results showed that the anti-epitestosterone monoclonal antibodies remained higher activity after immobilization and simultaneous determination of testosterone and epitestosterone in male urine was achieved by the immunoaffinity column coupling with capillary electrophoresis.
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