Pattern Recognition and Visual Detection of Aldehydes Using a Single ESIPT Dye.

The accurate discrimination and quantification of aldehydes is a worthy objective made challenging by their similar chemical reactivities. Considering the nucleophilic reaction mechanism between an aldehyde and a primary amine, it is reasonable to vary the reaction pH to manipulate the reactivity of aldehydes and the stability of the resulting Schiff base for analytical purposes. We have designed and synthesized three benzothiazole-based fluorescent molecules (BS1-BS3) containing an amino group substituted at the ortho-, meta-, and para-positions for aldehyde sensing. It was determined that only BS1 having an amino group at the ortho-position exhibits a significant fluorescence response in the presence of formaldehyde at a particular pH, whereas BS2 and BS3 gave negligible responses, indicating that the ESIPT process in BS1 should be responsible for the changes in its fluorescence. Accordingly, a pH-mediated sensor array BS1SA was constructed by dissolving BS1 in aqueous solvents with different pH values. BS1SA was found to be reliable for the discrimination of seven different aldehydes and identification of unknown aldehyde samples. Moreover, BS1 was successfully applied to prepare a fluorescent test paper for the visual detection of formaldehyde vapor.

Chemical sensors for selective and quantitative heparin sensing.

Heparin is widely used as an anticoagulant drug in clinics, especially in surgery and dialysis machines. For safe use of heparin, it is necessary to closely monitor its dosage during the application. However, this was determined to be a challenging task because the chemical structure of heparin is very complicated. As a matter of fact, some well-established methods such as activated clotting time assay (ACT) and activated partial thromboplastin time assay (aPTT) were indirect and not accurate enough for monitoring heparin concentration. Therefore, the development of fluorescence sensors for selective, quantitative and fast heparin sensing has attracted much attention. To date, small organic molecule-based sensors, organic-inorganic hybrid materials and supramolecular complexes have been reported for heparin sensing. In this review, the design strategy, working principle and sensing performance of chemical sensors for heparin are discussed in detail with representative examples that have been reported mainly within the past 15 years (up to early 2020). These examples are summarized according to their type of recognition unit and photophysical sensing mechanisms.

Porphyrin-GO Nanocomposites Based NIR Fluorescent Sensor Array for Heparin Sensing and Quality Control.

Heparin (Hep), widely used in clinics as an anticoagulant drug, has high degrees of heterogeneity and shares a similar disaccharide repeating unit with its GAG analogues. The development of reliable and convenient methods to discriminate Hep from its GAG analogues and detect trace GAG contaminants in Hep is meaningful for safe usage of Hep in clinics. Herein, five porphyrin-GO nanocomposites denoted as PP1-GO, PP2a-GO, PP2b-GO, PP3-GO, and PP4-GO were synthesized by assembling corresponding positively charged porphyrins onto the surface of GO. Controlled by a different number and position of the 4-N-methyl-pyridyl groups substituted at the porphyrins, these nanocomposites were determined to be cross-reactive toward Hep and other three commonly used GAGs including Chs, HA, and DS. A NIR sensor array PP-GO was thus constructed using these nanocomposites for GAGs discrimination and Hep quality control through pattern-based recognition. HCA and LDA calculated results indicated that PP-GO was powerful for discrimination of Hep and its GAG analogues in both PBS and even 10% serum media. Moreover, the PP-GO sensor array was successfully applied for the reliable discrimination of trace GAG contaminants in Hep with 100% accuracy.

Pyrene-porphyrin based ratiometric fluorescent sensor array for discrimination of glycosaminoglycans.

Accurate discrimination of common glycosaminoglycans (GAGs) before they are used in clinics is of great importance. Herein, a ratiometric sensor array Py-PP for discrimination of GAGs was constructed using three pyrene-porphyrin supramolecular complexes termed Py-PP1, Py-PP2 and Py-PP4. These complexes were readily synthesized by mixing pyrene-1-butyric acid (Py) and porphyrins PP1, PP2 and PP4 respectively. In the presence GAGs, the effective FRET from Py to porphyrin in the complex was influenced as a result of the competitive binding interactions between porphyrin and GAG. Controlled by the structural differences in the three porphyrins, complexes Py-PP1, Py-PP2 and Py-PP4 were determined to be cross-responsive towards tested GAGs including Hep, HA, Chs and DS. Distinctive fluorescence patterns were successfully generated for each GAG by the sensor array. The Py-PP sensor array was found to be powerful for discrimination of GAGs in both PBS and 5% serum media. Moreover, Py-PP was also successfully applied for reliable differentiation of Hep from other biological interferences and detection of trace GAG contaminants (0.1%, wt%) in Hep with 100% accuracy.