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Sulfamethazine is a representative member of the sulfonamide antibiotic drugs; it is still used in human and veterinary therapy. The protonation state of this drug affects its aqueous solubility, which can be controlled by its inclusion complexes with native or chemically-modified cyclodextrins. In this work, the temperature-dependent (298-313 K) interaction of sulfamethazine with native and randomly methylated β-cyclodextrins have been investigated at acidic and neutral pH. Surprisingly, the interaction between the neutral and anionic forms of the guest molecule and cyclodextrins with electron rich cavity are thermodynamically more favorable compared to the cationic guest. This property probably due to the enhanced formation of zwitterionic form of sulfamethazine in the hydrophobic cavities of cyclodextrins. Spectroscopic measurements and molecular modeling studies indicated the possible driving forces (hydrophobic interaction, hydrogen bonding, and electrostatic interaction) of the complex formation, and highlighted the importance of the reorganization of the solvent molecules during the entering of the guest molecule into the host's cavity.Molecules 2019, 24, 4565 2 of 12 tissues [13,14]. Furthermore, sulfonamides can appear as contaminants in various foods, which may cause adverse health effects [15][16][17]. The host-guest type complex formation of these antibiotics with CDs is an extensively studied field [18][19][20][21][22][23][24]. Zoppi et al. focus on the increased water solubility of sulfonamide drugs in the presence of native and methylated β-CD [23,24]. In the case of sulfamethazine (SMT), their nuclear magnetic resonance (NMR) and molecular modeling results demonstrate that SMT included the substituted pyrimidine ring into the β-CD cavity. Contradictory, NMR and quantum chemical results of Bani-Yaseen and Mo'ala revealed that complex formation is favorable with inclusion of the aniline moiety through the β-CD cavity [18].Several studies have been performed to get an insight into the factors which affect the thermodynamic and kinetic stability or selectivity of host-guest complexes [25,26], because the deeper understanding of these interactions has high importance. The pH-responsive host-guest encapsulation is also a highly studied field in material sciences [27] and in pharmacology [28,29]. Therefore, besides the complex stability and stoichiometry of SMT -β-CD complex and along the contradictory description of the related structures [18,23,24], the investigation of the pH dependence interaction of SMT with CDs is also reasonable.In our recent study [30], we demonstrated the importance of pH-dependent dipole moment of SMT molecule, which phenomenon can affect the complex geometry formed with β-CD (BCD) and randomly methylated β-CD (RAMEB) (Figure 1). Now we focus on the thermodynamic properties of the formation of inclusion complexes at different pH values. Our aim is to analyze the weak interactions between the pH dependent ionic and neutral forms of SMT and native or methylated CDs at molecular l...

The sulfamethazine drug interaction with carbon nanotubes was investigated with the aim of improving the adsorption capacity of the adsorptive materials. Experiments were performed to clarify how the molecular environment affects the adsorption process. Single-walled carbon nanotubes have a higher removal efficiency of sulfamethazine than pristine or functionalized multi-walled carbon nanotubes. Although the presence of cyclodextrin molecules improves the solubility of sulfamethazine, it reduces the adsorption capacity of the carbon nanotube towards the sulfamethazine drug and, therefore, inhibits the removal of these antibiotic pollutants from waters by carbon nanotubes.

Sulphonamide drugs (sulphamethazine, sulphamerazine, sulphadiazine, sulphathiazole) were studied in a wide potential window (between 2 and − 2 V) in acetonitrile, dimethyl sulphoxide and in 50–50 v/v% binary mixtures of acetonitrile and water. The voltammograms of the outlined compounds were very similar both in the anodic and cathodic part in each non-aqueous solvents except for sulphathiazole. These sulphonamide drugs were also investigated in presence of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) and its sodium salt and the voltammograms changed due to an acid–base reaction. HEPES and its sodium salt could be investigated in acetonitrile only in their saturation concentration as they were slightly soluble in this solvent. In a separate experiment their solubilities were determined at 298 K in acetonitrile with the co-solvent calibration method using water as co-solvent. Complementary fluorescence studies in dimethyl sulphoxide did not show the presence of any interaction between sulphonamide drugs and HEPES as well as its sodium salt.