Selective Modification of Halloysite Nanotubes with 1-Pyrenylboronic Acid: A Novel Fluorescence Probe with Highly Selective and Sensitive Response to Hyperoxide

Abstract

A novel fluorescence probe based on modified halloysite nanotubes (HNTs) by using 1-pyrenylboronic acid selectively grafted onto the inner surface of lumen was successfully achieved. The solid-state nuclear magnetic resonance ((13)C and (11)B), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) confirmed that the boronic acid group only binds to alumina at the tube lumen and does not bind the tube's outer siloxane surface. The modified HNTs (HNTs-PY) inherit the spectroscopic properties relating to the pyrene units. Interestingly, the established Al-O-B linkage gives the H2O2-sensitivity to pyrene grafted tubes. HNTs-PY exhibits a highly specific "turn-off" response for hyperoxide over other reactive oxygen species (ROS) and oxidative ions owing to their chemoselective boronate-to-phenol switch. The "turn-off" response can even be tracked when the additional amount of H2O2 was limited to 1 × 10(-6) mol. Thus, the selective modification method under mild conditions for the design of novel organic-inorganic hybrid fluorescence probe may open up a broader application as well as for identification and diagnosis.

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“…From the slope of oxygen consumption during the inhibited period (see Fig. 7 and 8), k inh values were obtained by using eqn (11) while the n coefficients were determined from the length of the inhibited period (t) by using eqn (12), from the known rate of radical production by AIBN (initiation rate, R i ).…”

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“…However, when coupled with the FTIR data, our group concludes that the number of molecules capable of grafting to the surface of the HNTs is lower than that reported in other similar studies [42][43][44][45]. In previously reported studies, the solvents used for the reaction were used to wash the compounds after the synthesis [42][43][44][45]. While this would remove some excess material, this method is ineffective at removing the material bound to the surface of the HNTs that is deposited in layer-by-layer self-assembly [20,46,47].…”

“…The signals in both FTIR and 13C{H1}CPMAS were weak when compared to the spectra present in the literature [13]. However, when coupled with the FTIR data, our group concludes that the number of molecules capable of grafting to the surface of the HNTs is lower than that reported in other similar studies [42][43][44][45]. In previously reported studies, the solvents used for the reaction were used to wash the compounds after the synthesis [42][43][44][45].…”

“…Furthermore, the addition of fluorescein isothiocyanate (FITC) to the surface creates a method by which the effectiveness of the targeted system can be determined via in vivo imaging [16]. Additionally, this study describes a washing process for the HNTs, post modification, that is not reported in similar studies [24,33,37,[42][43][44][45]. The resulting modified HNTs were characterized via FTIR, 13C{H1}CPMAS NMR, and UV-Vis spectroscopy.…”

Electrochemical Detection of Hydrogen Peroxide by Inhibiting the p-Benzenediboronic Acid-Triggered Assembly of Citrate-Capped Au/Ag Nanoparticles on Electrode Surface

“…The most common techniques used for H 2 O 2 detection at present are fluorescence and electrochemistry which employ fluorescent probes and enzyme-/nanomaterial-modified electrodes, respectively. We noticed that a few of the fluorescent H 2 O 2 sensors are based on the selective and efficient reaction between boronate groups (either boronic acid or boronate ester) and H 2 O 2 [25,26,27,28,29,30]. The boronate group in a fluorescent probe is usually removed by H 2 O 2 to yield its corresponding phenol form, thus resulting in an increase/decrease of the fluorescence intensity or a shift of the fluorescence peak.…”