RESUMO
In the present work, different configurations of nt iartificial neural networks (ANNs) were analyzed in order to predict the experimental diameter of nanofibers produced by means of the electrospinning process and employing polyvinyl alcohol (PVA), PVA/chitosan (CS) and PVA/aloe vera (Av) solutions. In addition, gelatin type A (GT)/alpha-tocopherol (α-TOC), PVA/olive oil (OO), PVA/orange essential oil (OEO), and PVA/anise oil (AO) emulsions were used. The experimental diameters of the nanofibers electrospun from the different tested systems were obtained using scanning electron microscopy (SEM) and ranged from 93.52 nm to 352.1 nm. Of the three studied ANNs, the one that displayed the best prediction results was the one with three hidden layers with the flow rate, voltage, viscosity, and conductivity variables. The calculation error between the experimental and calculated diameters was 3.79%. Additionally, the correlation coefficient (R2) was identified as a function of the ANN configuration, obtaining values of 0.96, 0.98, and 0.98 for one, two, and three hidden layer(s), respectively. It was found that an ANN configuration having more than three hidden layers did not improve the prediction of the experimental diameter of synthesized nanofibers.
RESUMO
Cytosine, a DNA and RNA building-block, and Metformin, the most widely prescribed drug for the treatment of Type 2 Diabetes mellitus were made to react separately with ammonium or sodium metavanadates in acidic aqueous solutions to obtain two polyoxovanadate salts with a 6:1 ratio of cation-anion. Thus, compounds [HCyt]6[V10O28]·4H2O, 1 and [HMetf]6[V10O28]·6H2O, 2 (where HCyt = Cytosinium cation, [C4H6N3O]+ and HMetf = Metforminium cation, [C4H12N5]+) were obtained and characterized by elemental analysis, single crystal X-ray diffraction, vibrational spectroscopy (IR and Raman), solution 51V-NMR, thermogravimetric analysis (TGA-DTGA), as well as, theoretical methods. Both compounds crystallized in P 1 ¯ space group with Z' = 1/2, where the anionic charge of the centrosymmetric ion [V10O28]6- is balanced by six Cytosinium and six Metforminium counterions, respectively. Compound 1 is stabilized by π-π stacking interactions coming from the aromatic rings of HCyt cations, as denoted by close contacts of 3.63 Å. On the other hand, guanidinium moieties from the non-planar HMetf in Compound 2 interact with decavanadate µ2-O atoms via N-H···O hydrogen bonds. The vibrational spectroscopic data of both IR and Raman spectra show that the dominant bands in the 1000-450 cm-1 range are due to the symmetric and asymmetric ν(V-O) vibrational modes. In solution, 51V-NMR experiments of both compounds show that polyoxovanadate species are progressively transformed into the monomeric, dimeric and tetrameric oxovanadates. The thermal stability behavior suggests a similar molecular mechanism regarding the loss of water molecules and the decomposition of the organic counterions. Yet, no changes were observed in the TGA range of 540-580°C due to the stability of the [V10O28]6- fragment. Dispersion-corrected density functional theory (DFT-D) calculations were carried out to model the compounds in aqueous phase using a polarized continuum model calculation. Optimized structures were obtained and the main non-covalent interactions were characterized. Biological activities of these compounds are also under investigation. The combination of two therapeutic agents opens up a window toward the generation of potential metalopharmaceuticals with new and exciting pharmacological properties.