Noninvasive Sialic Acid Detection at Cell Membrane by Using Phenylboronic Acid Modified Self-Assembled Monolayer Gold Electrode

Abstract

Alternations of sialic acid (SA) content on cell surface glycan chains have been implicated in numerous normal and pathological processes including developments, differentiations, and tumor metastasis. Overexpressions of SA have been implicated in the malignant and metastatic phenotypes for many different types of cancers, while decreased SA expression has also been identified in erythrocytes of diabetic mellitus. Techniques to conveniently monitor cell surface SA would therefore have great relevance to cytology. Preexisting methodologies to quantify SA, however, involve multiple enzymatic, dye-labeling, and lethal procedures, which are costly and time-consuming. Here we developed a potentiometric SA detection using a phenylboronic acid (PBA) compound integrated into the form of a self-assembled monolayer (SAM) onto a field effect transistor (FET) extended gold gate electrode. Due to selective binding between undisassociated PBA and SA at pH 7.4 among other glycan chain constituent monosaccharides, we found that carboxyl anions of SA were exclusively detectable as the change in threshold voltage (V(T)) of the PBA-modified FET. The technique was applied to analyses of altered SA expressions on rabbit erythrocyte as a model for diabetes. Comparative SA expression analyses for each healthy and diseased model revealed that the disease could be feasibly diagnosed simply by placing the known-count cell suspensions onto the device without any labeling and enzymatic procedures. Such a technique may also provide a quantitative adjunct to histological evaluation of tumor malignancy and metastatic potential during intra- and postoperative diagnoses. Also advantageously, a technique herein described is all within a CMOS (Complementary Metal Oxide Semiconductor) compatible format thus promising for highly efficient and low cost manufacturing with readiness of downsizing and integration by virtue of advanced semiconductor processing technologies.

Boron-Carbohydrate Interactions

“…In collaboration with Miyahara, a powerful method for the direct determination of cell-surface sialic acid levels has been developed. [63,64] Use of a self-assembled monolayer on a gold electrode allows a coating of boronates to be applied. Potentiometric measurements in the presence of cell suspensions containing either 0, 15, 30, or 100% metastatic cells are readily distinguishable (Figure 13).…”

Phenylboronic Acids-based Diagnostic and Therapeutic Applications

“…Our recent work has described a noninvasive PBA-based sensor to quantify SA. 38 Of note, most sugars can complex only with the tetrahedral anionic form of boronate, because the complex with the trigonal neutral form is usually susceptible to hydrolysis. In sharp contrast, SA-PBA binding is also favored by the trigonal form, for which involvement of multiple metastable binding sites along with intramolecular stabilization via B-N or B-O interactions are suggested to play roles.…”

“…To demonstrate the ability of the electrode to capture SA moieties on the cell membranes, erythrocyte was first investigated, for which a decline of SA content has been implicated in diabetes mellitus. 38 The altered SA level could be assessed in a real-time manner, simply by placing the known-count living cell suspensions onto the electrode. The electrode was further applied to the assessment of malignancy or the degree of metastasis of a tissue (murine melanoma: B16-F10-Luc-G5) specimen (Fig.…”

Highly sensitive SERS detection and quantification of sialic acid on single cell using photonic-crystal fiber with gold nanoparticles

“…Great efforts have been made to detect and quantify sialic acid. Commonly available detection methods include colorimetric (Svennerholm, 1957;Warren, 1959a) and fluorometric (Anumula, 1995;Katopodis et al, 1982) detection, other reported methods include chromatography spectrometry (Kawai et al, 1991;Manzi et al, 1990) and potentiometry (Matsumoto et al, 2009). However, each of these techniques is met with issues: the sensitivity of colorimetric detection is low (Freebersyser et al, 2010); fluorometric detection generally suffers from poor discrimination of specific fluorophores (König, 2000); the generation of broad emission spectra (Zipfel Contents et al, 2003) and photobleaching (Widengren and Rigler, 1996) obscure useful information.…”