Glycans in the form of glycoproteins or glycolipids play very critical roles in various biological and pathological processes including inflammation, cancer metastasis, immune reactions, embryo development, cell-cell communications and adhesions, blood generation, etc. Proteins (lectins) that can recognize carbohydrates have played very important roles in studying glycobiology. Small molecule mimics of lectins will be very useful in the development of new therapeutics and diagnostics. Along this line, boronic acids have been widely used in the design and synthesis of small organic compounds that mimic the function of lectins. This review examines in detail the factors that are important for the design of boronic acid-based lectin mimics, boronolectins.

The first general method for the selection of boronic acid-based aptamers that allow for glycan substructure focusing is described. Using fibrinogen as a model, we have selected boronic acid-modified DNA aptamers that have high affinities (low nM K d ) and the ability to recognize changes in the glycosylation site. The method developed should also be applicable to the development of aptamers for other glyco-products, such as glycolipids and glycopeptides. E-mail: wang@gsu.edu Supporting Information Available: Description of the experimental procedure and detailed results. This material is available free of charge via the Internet at http://pubs.acs.org. Glycosylation profoundly affects the function and activities of many proteins. 1,2 However, detecting and differentiating variations in glycosylation as an integral part of a glycoprotein is not a trivial matter, mostly due to a lack of good tools. Two most powerful methods exist for developing "binders" for glycoproteins: antibody production and nucleic acid-based aptamer selection. 2 However, none of these methods has the intrinsic ability to specifically focus on the glycosylation site, which include both the glycan and the surrounding structures, in epitope selection. We are interested in examining the possibility of directing the selection of aptamers to preferentially go after the glycosylation site of a glycoprotein (the sweet spot). By taking advantage of many published methods on incorporating modified nucleotide into DNA/RNA for aptamer selection, 3 we decided to incorporate a boronic acid-modified thymidine-5′-triphosphate (B-TTP, Figure 1) into DNA for aptamer selection. Because of the intrinsic ability for the boronic acid moiety to interact with diols 4 and single hydroxyl groups, 5 we hypothesized that the incorporation of the boronic acid moiety into DNA would allow the selection to gravitate toward the glycosylation site and therefore for the specific recognition of the glycosylation site. When necessary, counter selection can be used to eliminate unwanted cross-reactivity for binders as described in literatures. 3, 6 Herein, we report our work that demonstrates the feasibility by using a model protein, fibrinogen, which was chosen because of its commercial availability in large quantities and its known glycan structures. NIH Public AccessWe used the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) approach for aptamer selection. 2,3 Introduction of the boronic acid moiety was accomplished through tethering to the 5-position of TTP ( Figure 1) because (1) modification at this position has long been known to have minimal effect on polymerase-catalyzed incorporation; 3 (2) 5-position modified TTP has been widely used in aptamer selections to tune their affinity and bestow novel properties, 3 and (3) we have demonstrated that the B-TTP can be successfully incorporated into DNA using DNA polymerases, and the synthesized boronic acid-modified DNA (B-DNA) can serve as templates for further amplification. 7For the aptamer sel...

Effective management of diabetes relies on the frequent monitoring of blood glucose concentrations. The current approach of blood sampling and glucose concentration determination in vitro) presents many problems. Therefore, there is a drive for the development of non-invasive and continuous monitoring of glucose concentrations. The use of implanted glucose fluorescent sensors represents a promising approach. Due to its strong interaction with diol moieties, the boronic acid group often plays a critical role in the design of such glucose sensors. This paper reviews the progress in this area during the last ten years.