Heteroatoms chemical tailoring of aluminum nitrite nanotubes as biosensors for 5-hydroxyindole acetic acid (a biomarker for carcinoid tumors): insights from a computational study†

This study aims to elucidate the properties of aluminum nitrite nanotubes (AlNNT) encapsulated with phosphorus (P@AlNNT), sulphur (S@AlNNT), and silicon (Si@AlNNT) heteroatoms for use as biosensors for 5-hydroxyindoleacetic acid (5HIAA). It was considered an indicative biomarker for carcinoid tumors and investigated using the density functional theory (DFT) at the ωB97XD/def2svp level of theory. With adsorption energies of −0.009 eV, 0.055 eV, and 0.044 eV for 5HIAA_P@AINNT, 5HIAA_S@AINNT, and 5HIAA_Si@AINNT, respectively, the 5HIAA_P@AINNT was the only favorable system for adsorption of 5HIAA. According to the topological investigation, the hydrogen bond strength was in the order of 5HIAA_Si@AlNNT > 5HIAA_S@AlNNT > 5HIAA_P@AlNNT. This was also confirmed by NCI-RDG analysis. Regarding sensory parameters, as per the fraction of electron transfer, 5HIAA_S@AlNNT had the highest propensity to react with the sensor followed by 5HIAA_Si@AlNNT. The order of recovery time (τ) was recorded to be 5HIAA_P@AlNNT < 5HIAA_S@AlNNT < 5HIAA_Si@AlNNT. It was recorded that the systems 5HIAA_S@AlNNT and 5HIAA_Si@AlNNT had longer recovery times at 310 K when compared to their recovery times at 298 K. However, the system 5HIAA_P@AlNNT records a minute shorter recovery time at 298 K compared to its recovery time at 310 K. Results from molecular dynamic simulation reveal that 5HIAA_S@AlNNT and 5HIAA_Si@AlNNT are more thermally stable, which is necessary for reliable and accurate detection. System 5HIAA_P@AlNNT records the most favourable adsorption property and considerable sensing characteristics.