Medicinal and chemosensing applications of chitosan based material: A review

Chitosan (CTS), has emerged as a highly intriguing biopolymer with widespread applications, drawing significant attention in various fields ranging from medicinal to chemosensing. Key characteristics of chitosan include solubility, biocompatibility, biodegradability and reactivity, making it versatile in numerous sectors. Several derivatives have been documented for their diverse therapeutic properties, such as antibacterial, antifungal, anti-diabetic, anti-inflammatory, anticancer and antioxidant activities. Furthermore, these compounds serve as highly sensitive and selective chemosensor for the detection of various analytes such as heavy metal ions, anions and various other species in agricultural, environmental and biological matrixes. CTS derivatives interacting with these species and give analytical signals. In this review, we embark on an exploration of the latest advancements in CTS-based materials, emphasizing their noteworthy contributions to medicinal chemistry spanning the years from 2021 to 2023. The intrinsic biological and physiological properties of CTS make it an ideal platform for designing materials that interact seamlessly with biological systems. The review also explores the utilization of chitosan-based materials for the development of colorimetric and fluorimetric chemosensors capable of detecting metal ions, anions and various other species, contributing to advancements in environmental monitoring, healthcare diagnostics, and industrial processes.

Discriminative 'Turn-on' Detection of Al3+ and Ga3+ Ions as Well as Aspartic Acid by Two Fluorescent Chemosensors

In this work, two Schiff-base-based chemosensors L1 and L2 containing electron-rich quinoline and anthracene rings were designed. L1 is AIEE active in a MeOH-H₂O solvent system while formed aggregates as confirmed by the DLS measurements and fluorescence lifetime studies. The chemosensor L1 was used for the sensitive, selective, and reversible 'turn-on' detection of Al³⁺ and Ga³⁺ ions as well as Aspartic Acid (Asp). Chemosensor L2, an isomer of L1, was able to selectively detect Ga³⁺ ion even in the presence of Al³⁺ ions and thus was able to discriminate between the two ions. The binding mode of chemosensors with analytes was substantiated through a combination of ¹H NMR spectra, mass spectra, and DFT studies. The 'turn-on' nature of fluorescence sensing by the two chemosensors enabled the development of colorimetric detection, filter-paper-based test strips, and polystyrene film-based detection techniques.

Development of an azo functionalized oligomeric chitosan sensor for rapid visual, spectrophotometric and spectrofluorometric detection of KMnO4 up to micromolar concentrations

A water-soluble azo functionalized oligomeric chitosan reagent (β-NAC) has been developed for the visual detection and quantification of KMnO₄ at micromolar concentrations. The β-NAC sensor was also explored as a detection probe for the spectrophotometric and spectrofluorometric detection of several metal ions and anions. The synthesized reagent was characterized by TGA-DTA-DTG analysis, DLS studies, BET analysis, and spectral analysis. The β-NAC reagent produces conspicuous colours with different concentrations and different pH values of KMnO₄ solution. This provides evidence for high selectivity in the visual detection of KMnO₄ up to the micromolar level because of its interactions in the case of KMnO₄ only. The colour of the β-NAC reagent after interacting with KMnO₄ (10^-3 M) changes from brown to blood red. Furthermore, the β-NAC sensor was employed for the spectrophotometric detection of KMnO₄. The absorption spectrum of β-NAC shows a peak at 327 nm and on interacting with KMnO₄, it shows a bathochromic shift to 331 nm. The intensity of the peak at 331 nm increases as the concentration of KMnO₄ was increased from 1 μM to 0.01 M. The detection and quantification limits in the spectrophotometric detection of KMnO₄ were found to be 4.55 μM and 15.17 μM, respectively. The results of pH studies show that there is a pH effect of the KMnO₄ solution on KMnO₄ detection. The stability of the complex was determined by investigating the effect of time on the absorption intensity. In the spectrofluorometric detection, the fluorescence intensity of β-NAC at the 427 nm emission maxima was decreased on adding KMnO₄ solution. The fluorescence quenching increased on increasing the KMnO₄ concentration from 1 μM to 0.008 M. The optimum pH for fluorescence quenching was found to be 8. The detection and quantification limits in the spectrofluorometric detection of KMnO₄ were found to be 0.967 μM and 3.223 μM, respectively. The Stern-Volmer constant value was found to be 41 366.2 L mol^-1, confirming the significant complexation between KMnO₄ and the β-NAC reagent. Interference studies were conducted to analyse the effect of various metal ions and anions on KMnO₄ detection. Electrochemical studies were also performed to analyse the mechanism of complex formation.