Toward functionalization of ZnO nanotubes and monolayers with 5-aminolevulinic acid drugs as possible nanocarriers for drug delivery: a DFT based molecular dynamic simulation.

We have investigated the interactions between a 5-aminolevulinic acid (ALA) drug and ZnO nanostructures including ZnO monolayers and ZnO nanotubes (ZnONTs) using density functional theory (DFT) calculations. In the context of the dispersion corrected Perdew-Burke-Ernzerhof (PBE) approach, the energetics, charge transfer, electronic structure and equilibrium geometries have been estimated. As ALA is adsorbed onto/into the ZnONTs and on the ZnO monolayer with interaction energies (Eint) of -2.55/-2.75 eV and -2.51 eV, respectively, the calculated Eint values and bonding distances (∼2 Å) reveal that the interaction type is chemisorption. The ZnO nanostructures showed promising performance in the ALA drug functionalization, taking into account the interaction energy values. The band gap almost remains unchanged for both of the substrates under consideration after ALA adsorption, and the semiconductor properties of the substrates are preserved, according to the analyzed density of states (DOSs) spectra. The interaction nature of the ALA-ZnO nanostructures according to the atom in molecule (AIM) analysis was found to be polar attraction with partial covalent bonding between O and Zn. Our DFT based molecular dynamic (MD) simulation results demonstrate that, in the aqueous solution, ALA moves toward the interior sidewall of the ZnONTs and ZnO nanosheet surface and binds to the Zn atom through its O (carbonyl/hydroxyl groups) and N atoms and the hydroxyl H atom was dissociated and binds to the O atom of the ZnO surface. However, in the case of ALA adsorption onto the outer surface of ZnONTs, only the O atoms of carbonyl groups bind to the Zn atom and the structure of the drug remains undestroyed during the adsorption. The current findings shed light on the polar drug adsorption/encapsulation behavior on/into ZnO nanostructures, which may encourage further use of ZnO-based nanomaterials in the field of drug delivery and bio-functionalized nanomaterials.

Effects of Ge, Si, and B doping on the adsorption and detection properties of C60 fullerene towards methadone in gas and aqua phases: a DFT study.

CONTEXT: Methadone can be abused and caused addictive and has various side effects. Therefore, the development of a fast and reliable diagnosis technique for its monitoring is essential. In this work, applications of C60, GeC59, SiC59, and BC59 fullerenes were investigated utilizing density functional theory (DFT) to find a suitable probe for methadone detection. The C60 fullerene indicated weak adsorption energy for methadone sensing. Therefore, for the construction of the fullerene with good property for methadone adsorption and sensing, the GeC59, SiC59, and BC59 fullerenes have been studied. The adsorption energy of GeC59, SiC59, and BC59 in the most stable complexes were calculated at -2.08, -1.26, and -0.71 eV, respectively. Although GeC59, SiC59, and BC59 all showed strong adsorption, only BC59 present a high sensitivity for detection. Further, the BC59 fullerene showing a proper short recovery time (about 1.11 × 10-6 s for methadone desorption). Water as a solution is used to simulate the behavior of fullerenes in the body fluids, and results indicated that the selected pure and complex nanostructures are stable in water. The UV-vis spectrums indicated that the after adsorption of methadone on the BC59 exhibits shift toward the lower wavelengths (blue shift). Therefore, our investigation indicated that the BC59 fullerene is an excellent candidate for methadone detection. METHODS: The interaction of methadone with pristine and doped C60 fullerenes surfaces was calculated using the density functional theory calculations. The GAMESS program and M06-2X method with a 6-31G(d) basis set were used for computations. Since the M06-2X method overestimates the LUMO-HOMO energy gaps (Eg) of carbon nanostructures, the HOMO and LUMO energies and Eg were investigated at the B3LYP/6-31G(d) level of theory using the optimization calculations. UV-vis spectra of excited species were obtained through the time-dependent density functional theory. To simulate the human biological fluid, the solvent phase was also evaluated in adsorption studies, and water was considered a liquid solvent.

Reversible hydrogen adsorption on Li-decorated T-graphene flake: The effect of electric field.

In the present work, we have studied a new allotrope of graphene, denoted as T-graphene (TG) flake as a versatile material in hydrogen storage. Recently, the metallic character of TG has been revealed. Our results show that the Li-decoration has a significant effect on the electronic properties of TG flake. Our density functional theory (DFT) calculations exhibit that the energy band gap of TG flake is decreased by decorating of the Li atom. Hydrogen adsorption on Li-decorated TG flake (Li/TG) under the influence of different external electric fields (EFs) is also explored by DFT calculations. We found that the hydrogen adsorption on the Li/TG increases when the positive EF is applied. Our results also show that the adsorption energy of the hydrogen on the Li/TG can be gradually enhanced by increasing the applied positive external EF along with the charge transfer direction. Moreover, Li atom in the Li/TG shows the high hydrogen capacity up to six H2 molecules. On the other hand, the H2 adsorption on the Li/TG is remarkably decreased by applying the negative EFs to the Li/TG. Therefore, the H2 adsorption/release procedure on the Li/TG are reversible and can be tuned by applying the appropriate EFs. Our study exhibits that the Li/TG is a promising material for reversible adsorption and release of H2.

B24N24 fullerene as a carrier for 5-fluorouracil anti-cancer drug delivery: DFT studies.

It has been previously indicated that BN nanostructures may be nontoxic and biocompatible. Here the potential application of a B24N24 is explored as a drug delivery system for anti-cancer 5-fluorouracil based on the density functional theory. This drug prefers to attach via its oxygen atoms to the B atoms of the cluster with adsorption energy about -11.90kcalmol-1 based on the dispersion corrected B3LYP level of theory. To make the cluster more appropriate for drug delivery, we replaced a B atom by Si or Al atom to improve the interaction strength. The calculated adsorption energies are about -50.13 and -34.19kcalmol-1 for Al and Si doped BN clusters, respectively. It was found that, in addition to the more negative adsorption energy, the electronic properties of Al-doped BN are significantly sensitive to the drug adsorption. Also, a drug release mechanism is proposed, indicating that in the low pH of the cancer cells the drug and BN cluster are considerably protonated, thereby separating the drug from the surface of the cluster.