Biomedical Engineering Reference
In-Depth Information
with two obstacles: how to efficiently create diverse small molecule collections with
intriguing biological activity, and how to rapidly and effectively interrogate their func-
tions with different biological assays. To overcome the hindrance, small-molecule
microarray (SMM) rises to the call.
SMM is generally considered a state-of-the-art platform. In conjunction with solid-
phase combinatorial chemistry, it serves as a potent and preeminent technology to
interrogate the biological activity of small-molecules in a high-throughput manner. In
1999, MacBeath et al. demonstrated site-specific immobilization of small-molecules
onto an array, making it the first scientific description and documented evidence of
the early work on SMM. The team proved that the technology could lead to successful
identification of target protein/small molecule pairs [10]. In 2002, the same group
successfully identified a small-molecule modulator for yeast transcription inhibitor
Ure2p by screening a 3780-member small-molecule library on the microarray [11].
This remarkable breakthrough offers uncontested proof of the hypothesis that it is
possible to use small molecules to modulate selectively a target protein's activity. In
addition, the result established unambiguous demonstration of the distinctive potential
of a microarray platform for small-molecule screening research.
Over the past decade, SMM technology has experienced flourishing development
in many aspects, including small-molecule library synthesis, microarray fabrication,
and microarray application (Figure 13.1). In the following sections, the recent devel-
opment and evolution of SMM are elaborated and illustrated. Although it is not
possible to present exhaustive information and cover every detail of SMM within
the scope of this chapter, we focus on some of the most important highlights in the
development of this technology.
13.2 CHEMICAL LIBRARY DESIGN AND SYNTHESIS
A fundamental and crucial step for SMM fabrication is to create a diverse library
of biologically active compound collections. The libraries are derived mainly from
the following sources: commercially available libraries, isolated natural products,
and synthetic combinatorial libraries. Synthetic combinatorial libraries, for example,
have been shown to be a robust strategy to use to produce huge libraries of small
molecules. With advancements in solid-phase synthesis and combinatorial chemistry,
the synthesis of small-molecule libraries has been further accelerated.
Solid-phase chemistry was introduced by Merrifield in the 1960s for peptide syn-
thesis [12,13]. It provides a convenient and facile method to separate excess reagents
and soluble by-products from resin-bound products. With solid-phase chemistry,
researchers can avoid the tediousness of intermediate purification at each step of
the synthesis. It should be noted, however, that the chemistry utilized for synthesis
throughout the entire process must be highly efficient and selective. Otherwise, the
impurities accumulated will have a considerably negative impact on the overall purity
of the final product.
Split-and-pool synthesis is another technology that significantly accelerates the
process of generating huge libraries of compounds. The technology was introduced by
