Boronate‐Containing Copolymers: Polyelectrolyte Properties and Sugar‐Specific Interaction with Agarose Gel

Abstract

Copolymers of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with acryamide (AA), N,N-dimethylacrylamide (DMAA), and N-isopropylacrylamide (NIPAM) were found to adsorb on cross-linked agarose gel (Sepharose CL-6B) in the pH range from 7.5-9.2, due to specific boronate-sugar interactions. The molar percentages of phenylboronic acid (PBA) groups in the boronate-containing copolymers (BCCs), as estimated by 1H NMR spectroscopy, were 13, 10, and 16%, respectively, whereas the apparent ionization constants, the pKa values, of the copolymers were similar and equal to 9.0 +/- 0.2 at 20 degrees C. The copolymers adsorption capacities were in the range of 15-30 mg x ml(-1) gel (14-36 micromol pendant PBA ml(-1) gel) at pH 9.2 and decreased with decreasing pH value. The interaction of monomeric NAAPBA with Sepharose CL-6B was characterized by an equilibrium association constant of 53 +/- 17 M(-1), the chromatographic capacity factor k' = 1.8, and a total content of binding sites of 27 +/- 10 micromol x ml(-1) gel at pH 9.2. The weak reversible binding of monomeric NAAPBA and almost irreversible binding of NAAPBA copolymers to the gel at pH 9.2 suggested a multivalent character of the copolymer adsorption. At pH 7.5, the maximal adsorption capacity was displayed by the AA-NAAPBA copolymer (15 mg x ml(-1) gel). All the BCCs could be completely desorbed from the gel by 0.1 M fructose in aqueous buffered media with pH values from 7.5-9.2. The strong adsorption of AA-NAAPBA on agarose gel probably relates to the conformation of the copolymer in aqueous solution and provides opportunities for biomedical applications of the copolymer under physiological conditions. Multivalent, weak-affinity adsorption of BCCs to the agarose gel seems to be a tentative model for the copolymers' binding to oligo- and polysaccharides of cell membranes and mucosal surfaces.

Glucose sensors based on a responsive gel incorporated as a Fabry-Perot cavity on a fiber-optic readout platform

“…Boronic acid bind reversibly to cis-diols such as carbohydrates, polyvinyl alcohol and glycoproteins (James, 2007;Kuzimenkova et al, 2006). Boronic acids have been utilised in a variety of methods for glucose sensing including fluorescent (Badugu et al, 2004), electrochemical (Yokoyama et al, 1989) and optical detection .…”

Thin semitransparent gels containing phenylboronic acid: porosity, optical response and permeability for sugars

“…The dependence was also linear from 2 to 20 mM glucose at pH 7.5 (see Figure 3). The increase in sensitivity of the gels to glucose with increasing pH probably resulted from the increased fraction of ionized PBA groups (Kuzimenkova et al, 2006) capable of complex formation with the sugar. The linear calibrations were obtained in 50 mM sodium phosphate buffer at a relatively high ionic strength (ca.…”

“…Recently, we have found that random copolymer of acrylamide (Am) and N-acryloyl-m-aminophenylboronic acid (NAAPBA) (13 mol% NAAPBA) undergoes pH-dependent phase transition and forms precipitate in aqueous solutions at pH < 8, due to hydrophobic interactions of neutral PBA-groups (Kuzimenkova et al, 2006). Being copolymerized in water on a glass surface in the absence of any bifunctional cross-linker, the monomers formed semitransparent hydrogels (see Figure 1a) insoluble in water, 50 mM sodium phosphate buffer solutions (pH 6-8) and even in 1 M NaOH.…”

“…The gel-coated slides were kept in a dessicator over distilled water for 2 h and then transferred to and stored in distilled water for several days. The aqueous extract was dialysed, chromatographed on Sepharose CL-6B column to separate NAAPBA according to Kuzimenkova et al (2006) and assayed for the non-reacted NAAPBA by UV-spectrophotometry (l max ¼ 265 nm, e ¼ 9800 M À1 cm À1 at pH 9.2). For preparation of thinner gels, the volumes of mixed solutions were proportionally reduced (100 þ 50 ml, etc., see Table 2).…”

“…This has led to several studies of polymer hydrogels and thin polymeric films containing phenylboronic acid (PBA) as possible sugar sensors (Kikuchi et al, 1996;Gabai et al, 2001;Asher et al, 2003;Lee et al, 2004). Polymers containing PBA as a pendant group are known to interact with sugars, polysaccharides and nucleic acids in aqueous media Uguzdogan et al, 2003;Kanekiyo et al, 2005;Liu and Scouten, 2005;Kuzimenkova et al, 2006). For the physico-chemical reasons discussed below, it was difficult to obtain a linear response of dimensional or electrical characteristics of the gels to sugar concentration.…”