Dithiocarbazates comprise an important class of Schiff bases that have remarkable pharmacological applications due to the imine group present in their structure^1,2,3. However, the lipophilic character of 1-(S-benzyldithiocarbazate)-3-methyl-5-phenyl-pyrazole (DTC) limits its gastrointestinal absorption leading to low oral bioavailability. This problem can be solved using DTC-loaded nanoparticles, such as mesoporous silica nanoparticles (MSiNP), synthesized by Stöber method, which allows controlling the pores, walls and surfaces, facilitating the incorporation of several complex organic groups⁴. In this sense, the present work reports the loading of DTC in MSiNP aiming at potential application in drug delivery and targeting. The results indicated that MSiNP-DTC presented good stability in suspension, exhibiting Z-Ave of 175.7 ± 0.9, PdI of 0.38 ± 0.04 nm and ZP values ​​of – 21.9 ± 0.33 mV. The TEM image showed the mesoporous structure of the silica nanoparticles and also revealed no influence on the size, shape and morphology of MSiNP after its surface modification with DTC. The main band of DTC in FT-IR was shifted in relation to MSiNP appearing at 1627 cm^-1 (vibration band ν(C=N)). Thermal analysis showed an endothermic peak around 104℃ which is indicative of a crystalline state of the drug, confirming DTC loading on MSiNP. The percentage of drug loading (DL) and encapsulation efficacy (EE) were 9.9 ± 0.0001% and 99.3 ± 0.002%, respectively. This high efficiency can be explained based on the results of the BET which had a significant decrease in the specific surface area and MSiNP-DTC volume (617.9 ± 15.3 m²/g and 1.01 ± 0.01 cm³/g) and an increase in pore size (6.5 ± 0.1 nm), suggesting a pore blockage, leading DTC to adhere to the MSiNP surface. Therefore, the data suggest that MSiNP-DTC has potential for the use in drug delivery applications, improving stability and overcoming the low water solubility of Schiff's dithiocarbazate bases.

1. Costa, R. de O.; Coutinho, J. P. Use of Mixture Design to Optimize Nanofabrication of Dithiocarbazate–Loaded Polylactic Acid Nanoparticles. J. Appl. Polym. Sci. 2022, 139 (3), 1–13.
2. de Menezes, T. I.; de Oliveira Costa. Preparation and Characterization of Dithiocarbazate Schiff Base–Loaded Poly(Lactic Acid) Nanoparticles and Analytical Validation for Drug Quantification. Colloid Polym. Sci. 2019, 297 (11–12), 1465–1475.
3. Costa, A. R.; de Menezes, T. I. Ruthenium(II) Dimethylsulfoxide Complex with Pyrazole/Dithiocarbazate Ligand: Synthesis, Spectroscopy Studies, DFT Calculations and Thermal Behavior. J. Therm. Anal. Calorim. 2019, 0123456789 (Ii), 1683–1696.
4. Paula, A. J.; Martinez, D. S.T. Suppression of the Hemolytic Effect of Mesoporous Silica Nanoparticles after Protein Corona Interaction: Independence of the Surface Microchemical Environment. J. Braz. Chem. Soc. 2012, 23 (10), 1807–1814.