Spectrofluorimetric determination of aluminum ions via complexation with luteolin in absolute ethanol

A simple, cost-effective colorimetric assay for aluminum ions via complexation with the flavonoid rutin

Aluminum has been linked to deleterious health effects with high concentration, chronic exposure, creating a need for innovative detection techniques. Colorimetric assays are an ideal approach since they are simple, cost-effective, and field adaptable. Yet, commercially available colorimetric assays for aluminum are limited since it forms few colored chelation complexes. Flavonoids, a class of polyphenolic compounds, are one of the few examples that create colored aluminum complexes. Aluminum ions (Al3+) are the main constituent in colorimetric assays for flavonoid detection in food or plant samples. Our assay design was based on colorimetric flavonoid assays, where the assay reported herein was optimized. Specifically, the flavonoid rutin concentration and sample-to-rutin volume ratio (295:5 µL) were optimized to detect Al3+ at low µM concentrations in samples. The assay performed comparably, and in some instances better, than those requiring advanced instrumentation and previously reported colorimetric assays, with a linear range (1–8 µM), sensitivity (7.6 nM), limit of detection (79.8 nM), and limit of quantification (266 nM) for Al3+. The colorimetric assay was accurate (99 ≤ 108 ± 4 ≤ 6% Al3+ recovery), precise (low intra- and inter-assay coefficient of variation (CV) of 3.1 ≤ 5.9% and 4.4%, respectively), and selective for Al3+ ions compared to solutions containing a variety of other mono-, di-, and tri-cations at much higher concentrations (10- to 100-fold higher). Lastly, the colorimetric assay was applicable to complex analysis. It was used to generate a chelation curve depicting the Al3+ chelation capacity of sodium alginate, a biologically derived polymer used as a bioink for 3D bioprinting.

A Review on Coordination Properties of Al(III) and Fe(III) toward Natural Antioxidant Molecules: Experimental and Theoretical Insights

This review focuses on the ability of some natural antioxidant molecules (i.e., hydroxycinnamic acids, coumarin-3-carboxylic acid, quercetin, luteolin and curcumin) to form Al(III)- and Fe(III)-complexes with the aim of evaluating the coordination properties from a combined experimental and theoretical point of view. Despite the contributions of previous studies on the chemical properties and biological activity of these metal complexes involving such natural antioxidants, further detailed relationships between the structure and properties are still required. In this context, the investigation on the coordination properties of Al(III) and Fe(III) toward these natural antioxidant molecules might deserve high interest to design water soluble molecule-based metal carriers that can improve the metal’s intake and/or its removal in living organisms.

Phytochemicals toward Green (Bio)sensing

Because of numerous inherent and unique characteristics of phytochemicals as bioactive compounds derived from plants, they have been widely used as one of the most interesting nature-based compounds in a myriad of fields. Moreover, a wide variety of phytochemicals offer a plethora of fascinating optical and electrochemical features that pave the way toward their development as optical and electrochemical (bio)sensors for clinical/health diagnostics, environmental monitoring, food quality control, and bioimaging. In the current review, we highlight how phytochemicals have been tailored and used for a wide variety of optical and electrochemical (bio)sensing and bioimaging applications, after classifying and introducing them according to their chemical structures. Finally, the current challenges and future directions/perspective on the optical and electrochemical (bio)sensing applications of phytochemicals are discussed with the goal of further expanding their potential applications in (bio)sensing technology. Regarding the advantageous features of phytochemicals as highly promising and potential biomaterials, we envisage that many of the existing chemical-based (bio)sensors will be replaced by phytochemical-based ones in the near future.

Amphiphilic carbon dots for sensitive detection, intracellular imaging of Al3

In this paper, a simple and effective method was designed to synthesize hydrophobic carbon dots. Subsequently, amphiphilic fluorescent carbon dots (A-CDs) were synthesized by further surface modification. The result A-CDs show excellent optical properties with a quantum yield of 16.9%. It was interestingly found that morin (MR) and its fluorescent metal-ion complex (MR-Al³⁺) can successfully coordinate on the surface of A-CDs, the emission of A-CDs completely overlapped the absorption peak of MR-Al³⁺. Thus, the prepared A-CDs can be used as an effective fluorescent probe for Al³⁺ based on a fluorescence resonance energy transfer process. The sensing platform can realize real-time detection of Al³⁺ within 0.5 min. The fluorescence signals of the system were linearly correlated with the concentration of Al³⁺ over a range of 8-20 μM, with a detection limit of 0.113 μM. The method was also successfully applied to image the distribution of Al³⁺ in Human Umbilical Vein Endothelial Cells.