A Fluorescent Probe for Pyrophosphate Based on Tetraphenylethylene Derivative with Aggregation-Induced Emission Characteristics

An AIEE-active Triphenylethylene Derivative with Photoresponsive Character for Latent Fingerprints Detection via a Simple Soaking Method

Latent fingerprints (LFPs) is one of the most important physical evidence in the criminal scene, playing an important role in forensic investigations. Therefore, developing highly sensitive and convenient materials for the visualization of LFPs is of great significance. We designed and synthesized an organic fluorescent molecule TP-PH with aggregation-induced enhanced emission (AIEE) activity. By simply soaking, blue fluorescent images with high contrast and resolution are readily developed on various surfaces including tinfoil, steel, glass and plastic. Remarkably, LFPs can be visualized within 5 min including the first-, second- and tertiary-level details. In addition, TP-PH exhibits interesting photoactivated fluorescence enhancement properties. Under irradiation of 365 nm UV light with a power density of 382 mW/cm2, the fluorescence quantum yield displays approximately 21.5-fold enhancement. Mechanism studies reveals that the photoactivated fluorescence is attributed to the irreversible cyclodehydrogenation reactions under UV irradiation. This work provides a guideline for the design of multifunctional AIEE fluorescent materials.

An aggregation induced emission active bis-heteroleptic ruthenium(II) complex for luminescence light-up detection of pyrophosphate ions

A red emissive ruthenium(II) complex 1[PF6]2 of an amino ethanol substituted 1,10-phenanthroline-based ligand (L1) has been developed and characterized by spectroscopic analysis and single-crystal X-ray diffraction. Complex 1 shows an aggregation-induced emission (AIE) enhancement and forms nano-aggregates in the poor solvent water and highly dense polyethylene glycol (PEG) media. The possible reason behind the AIE properties may be the rigidity gained through weak supramolecular interactions between neighbouring phenanthroline ligands and PF₆^- counterions. The AIE properties were supported by UV-vis and photoluminescence (PL) spectroscopy and dynamic light scattering (DLS) studies to substantiate the formation of nano-aggregates and to understand the morphology of the aggregated particles, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies were performed. Compound 1[PF6]2 was highly selective towards pyrophosphate ions (PPi) over other phosphates such as ATP, ADP, AMP and H₂PO₄^- ions and other competitive anions in the PL spectroscopic channel in acetonitrile. The PL titrations of 1[PF6]2 with PPi in CH₃CN furnished the association constant K_a = 1.08 × 10⁴ M^-1 and the detection limit was calculated as low as 1.54 μM. The PPi detection has been established through the unique H-bonding interaction, supported by ¹H NMR titration. Finally, the cytotoxicity study and bioimaging were carried out for biological application. The complex shows very low cytotoxicity and good biocompatibility and is suitable for intracellular PPi imaging.

Multicolor diagnosis of salivary alkaline phosphatase triggered by silver-coated gold nanobipyramids

Alkaline phosphatase (ALP) is one of the most versatile biomarkers for early detection of several diseases, such as oral carcinomas and periodontitis; therefore, great efforts have been dedicated for developing an ALP biosensor. Multicolor detection of ALP in saliva is ideal for a point-of-care diagnosis; however, this approach is very challenging since spectral responses over wavelengths of several tens of nanometers have thus far remained difficult to achieve. In this work, a colorimetric biosensor for ALP assay has been developed based on ALP affinity to dephosphorylate glucose phosphate into glucose, which has the affinity to deposit Ag nanoshells onto Au nanobipyramids with a multicolor response. This approach provides a blue shift of localized surface plasmon resonance (LSPR) as large as 190 nm corresponding to distinctive color changes, from yellowish brown to red based on the thickness of the formed Ag shell around the Au nanobipyramids. The change in the LSPR has been conducted for highly sensitive quantitative bioassay of ALP with a detectable multicolor change with linear dynamic range of 0.1-20 U/L and low limit of detection (LOD) of 0.085 U/L. Furthermore, the developed multicolor ALP biosensor exhibits high selectivity with high recovery of 98.6% demonstrating  its reliability and suitability for a point-of-care diagnosis.

A colorimetric alkaline phosphatase biosensor based on p-aminophenol-mediated growth of silver nanoparticles

Alkaline phosphatase (ALP) is an enzyme that catalyzes the dephosphorylation of proteins, nucleic acids, and biomolecules. It is a potential biomarker for diverse diseases such as breast cancer, osteopenia, and hepatobiliary. Herein, we developed a colorimetric sensor for the ALP assay based on its enzymatic activity to dephosphorylate the p-aminophenol phosphate (pAPP) into pAP. In a solution containing silver nanoparticles (AgNPs) and Ag⁺ ions prepared using a low concentration of NaBH₄, pAP mediates the growth of AgNPs by reducing the concentration of Ag⁺ ions to enhance the intensity of localized surface plasmon resonance as the pAPP cannot induce a reduction of the remaining Ag⁺ due to the masking of the hydroxyl with phosphate. The quantitative assay of the ALP was demonstrated via the colorimetric detection of the pAP-mediated growth of AgNPs in the presence of an ALP. The highly sensitive enzymatic growth of AgNPs provided a wider dynamic linear range of 0.5-225 U/L with a lower limit of detection of 0.24 U/L than that previously reported. The use of pAP resulted in excellent selectivity of the sensor for the ALP assay in human serum, yielding a high recovery rate and a high precision of 99.2 ± 1.5 % for the standard addition method.

Recent Advances in Aggregation-Induced Emission Chemosensors for Anion Sensing

The discovery of the aggregation-induced emission (AIE) phenomenon in the early 2000s not only has overcome persistent challenges caused by traditional aggregation-caused quenching (ACQ), but also has brought about new opportunities for the development of useful functional molecules. Through the years, AIE luminogens (AIEgens) have been widely studied for applications in the areas of biomedical and biological sensing, chemosensing, optoelectronics, and stimuli responsive materials. Particularly in the application of chemosensing, a myriad of novel AIE-based sensors has been developed to detect different neutral molecular, cationic and anionic species, with a rapid detection time, high sensitivity and high selectivity by monitoring fluorescence changes. This review thus summarises the recent development of AIE-based chemosensors for the detection of anionic species, including halides and halide-containing anions, cyanides, and sulphur-, phosphorus- and nitrogen- containing anions, as well as a few other anionic species, such as citrate, lactate and anionic surfactants.