Amphiphilic Porphyrin Aggregates: A DFT Investigation

Electrochemiluminescence immunoassay system based on PCN-224-Mn and gold-platinum bimetallic nanoflowers for sensitive detection of ochratoxin A

In this work, a novel Electrochemiluminescence Immunosensor was constructed using PCN-224-Mn and gold-platinum nanoflowers (AuPt NFs) for the ultrasensitive detection of ochratoxin A (OTA). PCN-224 modified with Mn (II) was synthesized as a probe material. The interaction efficiency of PCN-224 with S2O82- was also greatly improved. AuPt NFs were used as the substrate material for the electrodes. It has favorable biocompatibility, large specific surface area and can bind more antigen. Also greatly increased the electroactive surface area and conductivity of the electrode. OTA was detected using a competitive immunoassay strategy, in which OTA in the sample competes with the encapsulated antigen for a finite number of antibodies. ECLIA for the detection of OTA was designed to be highly sensitive, with a linear range from 0.0002 ng mL-1 to 1000 ng mL-1 and a LOD as low as 0.067 pg mL-1. In addition, it was evident from the electrochemical analyses that PCN-224-Mn had a stronger and more stable ECL signal compared to the plain PCN-224. The successful preparation of specific, sensitive and reproducible ECL immunosensors confirms the great promise for the detection of OTA or other small molecule mycotoxins.

New Insights in the Computational pKb Determination of Primary Amines and Anilines

Extensive research has already provided reliable methods for the in silico prediction of pKa, while a trustworthy strategy for pKb determination is still being sought. Indeed, the approaches previously exploited for computing pKa have shown their weakness in predicting pKb. In the light of the exceptional reliability demonstrated in the pKa calculation of a wide panel of organic acids, in this work, we exploited our "easy to use methodology", based on the direct approach, to predict the pKb of primary amines. Herein, CAM-B3LYP was compared to WB97XD and B3PW91, exploring the solvation model based on density (SMD) and the polarizable continuum model (PCM), in the presence of two explicit water molecules. Noteworthy, CAM-B3LYP and WB97XD returned completely different solvent accessible surfaces (SAS) and electron potential maps (EPM) for the bases and the conjugated acids, independently from the nature of the substituents. Once again, CAM-B3LYP/SMD/2H2O method confirmed its remarkable reliability, leading to a minimum average error (MAE) lower than 0.3. This outstanding result strengthens the trustworthiness of our method, already successfully applied to predict the pKa of different substituted phenols and carboxylic acids. Thus, our "easy-to-use" process can predict also the pKb of primary ammines and anilines, always ensuring consistent outputs.

Easy to Use DFT Approach for Computational pKa Determination of Carboxylic Acids

In pKa computational determination, the challenge in exploring and fostering new methodologies and approaches goes in parallel with the amelioration of computational performances. In this paper a "ready to use methodology" has been compared to other strategies, such as the re-shaping in solvation cavity (Bondi radius re-shaping), wanting to assess its reliability in predicting the pKa of a broad list of carboxylic acids. Thus, the functionals B3LYP and CAM-B3LYP have been selected, using SMD as continuum solvation model. Exploiting our previous results, two water molecules were made explicit on the reaction centre. Data show that our model (CAM-B3LYP/2H2 O) is capable to accurately predict pKa, leading to mean absolute error (MAE) values lower than 0.5. Noteworthy, good results were achieved in computing the pKa of substituents bearing nitro and cyano groups. Focusing on B3LYP, eventually remarkable outputs were obtained only when Bondi correction was applied to the complex with two water molecules. Hence, massive outcomes were obtained in foreseeing the trichloro and trifluoro acetic acid pKa. These findings demonstrated that no complex level of theory nor external factor is required to accurately predict carboxylic acids pKa, with MAE well below 0.5 units.

An Accurate Approach for Computational pKa Determination of Phenolic Compounds

Computational chemistry is a valuable tool, as it allows for in silico prediction of key parameters of novel compounds, such as pKa. In the framework of computational pKa determination, the literature offers several approaches based on different level of theories, functionals and continuum solvation models. However, correction factors are often used to provide reliable models that adequately predict pKa. In this work, an accurate protocol based on a direct approach is proposed for computing phenols pKa. Importantly, this methodology does not require the use of correction factors or mathematical fitting, making it highly practical, easy to use and fast. Above all, DFT calculations performed in the presence two explicit water molecules using CAM-B3LYP functional with 6-311G+dp basis set and a solvation model based on density (SMD) led to accurate pKa values. In particular, calculations performed on a series of 13 differently substituted phenols provided reliable results, with a mean absolute error of 0.3. Furthermore, the model achieves accurate results with -CN and -NO₂ substituents, which are usually excluded from computational pKa studies, enabling easy and reliable pKa determination in a wide range of phenols.

Carbon Nanopowder-Based Stochastic Sensor for Ultrasensitive Assay of CA 15-3, CEA and HER2 in Whole Blood

Two microsensors obtained by the physical immobilization of 5,10,15,20-tetraphenyl-21H,23H-porphine (TPP) and 5,10,15,20-tetrakis (pentafluorophenyl chloride)-21H,23H-iron (III) porphyrin (Fe(TPFPP)Cl) in carbon nanopowder decorated with gold nanoparticles (AuNp) were designed, characterized, validated and used for the molecular recognition and simultaneous ultrasensitive determination of CEA, CA15-3 and HER2 in whole blood. High sensitivities were recorded for both microsensors. Low limits of quantification were recorded for all biomarkers: CEA (12.8 pg mL-1 by using Fe(TPFPP)Cl/AuNp, and 190 fg mL-1 by using TPP/AuNp), CA 15-3 (100 fU mL-1 for both microsensors) and HER2 (3.9 fg mL-1 by using Fe(TPFPP)Cl/AuNp, and 35 fg mL-1 by using TPP/AuNp). A very good correlation between the results obtained using the proposed microsensors and ELISA, certified by the Student t-test, proves that the screening test can be used for ultrasensitive assays of the three biomarkers in whole blood.