Four kinds of aminosilane layers on glass slides or silicon wafers were prepared. The amine densities of the layers prepared with aminopropyldiethoxymethylsilane (APDES), aminopropylmonoethoxydimethylsilane (APMES), a mixture of (aminopropyl)triethoxysilane (APTES) and n-butyltrimethoxysilane (n-BTMS) (v/v ) 1:10) are 4.0((0.8), 1.0((0.2), and 0.30((0.6) amine/nm 2 , respectively. A substrate with much higher amine density, that is, 40((8) amines/nm 2 was also prepared by allowing aziridine to polymerize on the APDES-treated substrate. AFM revealed that APDES-, APMES-, and APTES/n-BTMS-treated surfaces were relatively flat; on the other hand, an aziridine-treated surface showed embossed morphology. The amine substrates were allowed to react with a heterobifunctional linker succinimidyl 4-maleimido butyrate (SMB), and subsequently pentadecadeoxynucleotides were microarrayed on the SMB-treated substrates. Characteristics of the DNA microarrays including the dynamic range, the mismatch discrimination efficiency, and so forth were examined. Noteworthily, DNA microarrays on the aziridinepolymerized substrate showed much higher fluorescence intensity. At the same time, DNA microarrays from these four substrates were able to discriminate internal-and terminal-mismatched pairs, but the fluorescence ratio was far from the one that thermodynamics implies.

We have prepared solid substrates modified with a cone-shaped dendron that generates mesospacing (3.2 nm on average) on the surface. This nanoscale-controlled surface provided an ideal DNA microarray in which each probe DNA strand was given ample space for the incoming target DNA, resulting in selectivity as high as that in solution (100: < 1). In addition, high hybridization yield confirms that DNA probes on the mesospaced surface are sterically unhindered for the hybridization.

Microarrays of biomolecules are emerging as powerful tools for genomics, proteomics, and clinical assays, since they make it possible to screen biologically important binding events in a parallel and high throughput fashion. Because the microarrays are fabricated on a solid support, coating of the surface and immobilization strategy of the biomolecules are major issues for successful microarray fabrication. This review deals with both DNA microarrays and protein microarrays, and focuses on the various modification approaches for the two-dimensional surface materials and three-dimensional ones. In addition, the immobilization strategies including adsorption, covalent attachment, physical entrapment, and affinity attachment of the biomolecules are summarized, and advantage and limitation of representative efforts are discussed.

Scheme 1Fig. 2 Excitation spectra of the europium(iii) complex in the presence of 1 equiv. of Bis-Tris. Spectra were recorded in water upon addition of (a) 0, (b) 1.0, (c) 2.0 and (d) 2.5 equiv. NaOH.

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