Discrimination and Quantitation of Biologically Relevant Carboxylate Anions Using A [Dye•PAMAM] Complex

Abstract

Carboxylate anions are analytical targets with environmental and biological relevance, whose detection is often challenging in aqueous solutions. We describe a method for discrimination and quantitation of carboxylates in water buffered to pH 7.4 based on their differential interaction with a supramolecular fluorescent sensor, self-assembled from readily available building blocks. A fifth-generation poly(amidoamine) dendrimer (PAMAM G5), bound to organic fluorophores (calcein or pyranine) through noncovalent interactions, forms a [dye•PAMAM] complex responsive to interaction with carboxylates. The observed changes in absorbance, and in fluorescence emission and anisotropy, were interpreted through linear discriminant analysis (LDA) and principal component analysis (PCA) to differentiate 10 structurally similar carboxylates with a limit of discrimination around 100 μM. The relationship between the analytes’ chemical structures and the system’s response was also elucidated. This insight allowed us to extend the system’s capabilities to the simultaneous identification of the nature and concentration of unknown analytes, with excellent structural identification results and good concentration recovery, an uncommon feat for a pattern-based sensing system.

Beta-Lactam Antibiotic Discrimination Using a Macromolecular Sensor in Water at Neutral pH

“…The analytes’ relative binding affinities to PAMAM could be estimated from these profiles by fitting the profiles to a Langmuir-type saturation binding model (see Supporting Information ). The resulting relative affinities, listed in Table 1 , can be correlated to the charge state of the analytes; a higher negative charge on the antibiotic resulted in stronger affinity for PAMAM, thanks to stronger electrostatic interactions with the polycationic dendrimer, in accordance with similar trends we previously reported for other anionic guests [ 18 , 22 ]. This trend was particularly clear in the fluorescence anisotropy profiles because anisotropy directly reports on the molar fraction of dye bound to the macromolecular host.…”

“…Then, with the introduction of a carboxylate analyte, the latter formed its complex with PAMAM and caused dye displacement; the binding between dendrimer and analyte could therefore be monitored through the resulting spectroscopic behavior of the dye. We previously reported a sensor system built from PAMAM G5 and a commercially available dye, calcein (see Scheme 3 ), that was successful for the discrimination and quantitation of biologically relevant carboxylates in aqueous solution at pH 7.4 [ 22 ]. The β-lactam antibiotics targeted here all contain one carboxylate group in their core structure which can be a point of interaction with the PAMAM-calcein sensor, so, in this study, we expand the scope of that system towards the sensing of carboxylate-containing antibiotics, using similar conditions to those reported previously ([calcein] = 6.36 μM and [PAMAM G5] = 2.13 μM in 50 mM aqueous HEPES buffer at pH 7.4).…”

Effects of polyethylene glycol-grafted phospholipid on the anionic magnetite nanoparticles-induced deformation and poration in giant lipid vesicles

“…To study the pore formation of GUVs induced by NPs, 100 μL of NPs were introduced to a 200 μL suspension of PEG-DOPE/DOPC-GUVs containing 1.0 mM calcein (a water-soluble fluorescent dye with high quantum yield) was used in the GUV lumen to monitor the time-course of fluorescence of the GUV during the interaction with NPs [ 51 ]. Like the experiment of deformation of the GUVs, here we also varied the concentration of PEG-DOPE in the GUV-membrane accordingly to examine the effect of PEG-DOPE on NPs-induced pore formation in GUVs.…”

Optical sensor arrays for the detection and discrimination of natural products

“…The identity and concentration of 10 structurally similar carboxylic acids can be determined simultaneously at the mM level. 86…”