Cucurbituril hosts as promoters of aggregation induced emission of triphenylamine derivatives

Bimodal Array-Based Fluorescence Sensor and Microfluidic Technology for Protein Fingerprinting and Clinical Diagnosis

Proteins play a crucial role in determining disease states in humans, making them prime targets for the development of diagnostic sensors. The developed sensor array is used to investigate global proteomic changes by fingerprinting multifactorial disease states in model urine simulating phenylketonuria and in serum from preeclamptic pregnant women. Here, we report a fluorescence-based chemical sensing array that exploits the host-guest interaction between cucurbit[7]uril (CB[7]) and fluorescent triphenylamine derivatives (TPA) to detect a range of proteins. Using linear discriminant analysis, we identify fluorescence fingerprints of 14 proteins with over 98% accuracy in buffer and human serum. The array is optimized on an automated droplet microfluidic-based platform, for high-throughput sensing with controlled composition and lower sample volumes. This sensor enables the discrimination of proteins in physiological buffer and human serum, with promising applications in disease diagnosis.

Unlocking the Potential of Push-Pull Pyridinic Photobases: Aggregation-Induced Excited-State Proton Transfer

The pH effect on the photophysics of three push-pull compounds bearing dimethoxytriphenylamine (TPA-OMe) as electron donor and pyridine as electron acceptor, with different ortho-functionalization (-H, -Br, and -TPA-OMe), is assessed through steady-state and time-resolved spectroscopic techniques in DMSO/water mixed solutions and in water dispersions over a wide pH range. The enhanced intramolecular charge transfer upon protonation of the pyridinic ring leads to the acidochromic (from colorless to yellow) and acido(fluoro)chromic (from cyan to pink) behaviours of the investigated compounds. In dilute DMSO/buffer mixtures these molecules exhibited low pKa values (≤3.5) and extremely short singlet lifetimes. Nevertheless, it is by exploiting the aggregation phenomenon in aqueous environment that the practical use of these compounds largely expands: i) the basicity increases (pKa≈4.5) approaching the optimum values for pH-sensing in cancer cell recognition; ii) the fluorescence efficiencies are boosted due to Aggregation-Induced Emission (AIE), making these compounds appealing as fluorescent probes; iii) longer singlet lifetimes enable Excited-State Proton Transfer, paving the way for the application of these molecules as photobases (pKa*=9.1). The synergy of charge and proton transfers combined to the AIE behaviour in these pyridines allows tunable multi-responsive optical properties providing valuable information for the design of new light-emitting photobases.

Highly Selective Fluorescent Sensors: Polyethylenimine Derivatives of Triphenylamine and Coumarin for GTP and ATP Interaction via Fluorescence Lifetime Imaging Microscopy

Chemical derivatives of polyethylenimine (PEI) receptors with either triphenylamine (TPA) or 7-hydroxy-4-methyl-coumarin (Cou) form stable complexes with adenine and guanine nucleotides in water. The host-guest complex modulation is found to be based on noncovalent molecular interactions such as π-π stacking and hydrogen bonding, which are dependent on the aromatic moieties attached to the polyaminic (PEI) backbone. PEI-TPA acts as a chemosensor with a recognition driving force based on aggregation-induced emission (AIE), involving π-π interaction between the nucleic base and TPA. It detects GTP by a chelation enhancement quenching effect of fluorescence (CHEQ) with a measured logarithm stability constant, log β = 7.7. By varying the chemical characteristics of the fluorophore, as in the PEI-Cou system, the driving force for recognition changes from a π-π interaction to an electrostatic interaction. The coumarin derivative detects ATP with a log β value one order of magnitude higher than that for GTP, allowing for the selective recognition of the two nucleotides in a 100% aqueous solution. Furthermore, fluorescence lifetime imaging microscopy (FLIM) allows for a correlation between the selectivity of PEI-TPA toward nucleotides and the morphology of the structures formed upon ATP and GTP recognition. This study offers valuable insights into the design of receptors for the selective recognition of nucleotides in water.

Supramolecular host-guest interaction-driven electrochemical recognition for pyrophosphate and alkaline phosphatase analysis

Herein, we report an electrochemical biosensor based on the supramolecular host-guest recognition between cucurbit[7]uril (CB[7]) and L -Phenylalanine-Cu(II) Complex for pyrophosphate (PPi) and alkaline phosphatase (ALP) analysis. First, L -Phe-Cu(II) Complex is simply synthesized by the complexation of Cu(II) (metal node) with L -Phe (bioorganic ligand), which can be immobilized onto CB[7] modified electrode via host-guest interaction of CB[7] and L -Phe. In this process, the signal of the Complex triggered electro-catalytic reduction of H 2 O 2 can be captured. Next, in the view of strong chelation between PPi and Cu(II), a biosensing system of the model "PPi and Cu(II) premixing, then adding L -Phe" is designed and the platform can be applied for PPi analysis well by hampering the formation of L -Phe-Cu(II) Complex. Along with ALP introduction, PPi can be hydrolyzed into orthophosphate (Pi), where abundant Cu(II) ions are released to form L -Phe-Cu(II) Complex, which gives rise to the catalytic reaction of Complex to H 2 O 2 reduction. The quantitative analysis of H 2 O 2 , PPi and ALP activity is achieved successfully and the detection of limits are 0.067 μM, 0.42 μM and 0.09 mU/mL ( S / N =3), respectively. With the merits of high sensitivity and selectivity, cost-effectiveness, and simplification, our developed analytical system has great potential to act on diagnosis and treatment of ALP-related diseases.