Examinando por Autor "Diaz de Tuesta, Jose L."

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Comprehensive characterization and development of multi-core shell superparamagnetic nanoparticles for controlled delivery of drugs and their kinetic release modelling
(Elsevier, 2023) Moretto, Simone; Santos Silva, Adriano; Diaz de Tuesta, Jose L.; Roman, Fernanda F.; Cortesi, Rita; Bertão, Ana Raquel; Bañobre-López, Manuel; Pedrosa, Marta; Silva, Adrián M.T.; Gomes, Helder T.
The nanoparticles designed for application in cancer treatment should have biocompatibility, colloidal stability and triggered release at tumor sites. Magnetic nanoparticles arise as an interesting option to be used as drug nanocarriers, considering the possibility of driving nanoparticles to the correct delivery site and exploring different triggers to achieve such accomplishment. In this study, nickel ferrite nanoparticles are explored as a magnetic core for drug delivery systems, using doxorubicin and omeprazole as model drugs. The developed nickel ferrite presents a strong superparamagnetic behavior and high purity, as demonstrated by magnetometry and TGA results. The carbon-coating procedure and functionalization allowed the nanoparticle to achieve the desired characteristics for biomedical applications (i.e. stability in water, biocompatibility, and size). According to TEM results, the final carbon-coated magnetic nanoparticles have an average size of 25.09 ± 0.58 nm and multi-core shell architecture, which is suitable for biomedical applications as drug nanocarriers. In addition, DLS demonstrated that functionalized nanoparticles are monodisperse, with a hydrodynamic diameter of 167 ± 59 nm, which fits the recommended range (100–200 nm) to benefit from enhanced permeability and retention effect. Drug loading tests with doxorubicin and omeprazole revealed the versatility of the designed nanoparticles, able to load 97% of doxorubicin and 51% of omeprazole. The pH-triggered release was also confirmed for both pharmacological compounds, showing a higher cumulative drug under acidic conditions (simulating a tumor microenvironment). Finally, the kinetic analysis applied to the study of the release mechanism of both medicines showed that non-linear models fit with higher accuracy the experimental data.
Polyolefin-derived carbon nanotubes as magnetic catalysts for wet peroxide oxidation of paracetamol in aqueous solutions
(Elsevier, 2023) Diaz de Tuesta, Jose L.; Silva, Adriano Santos; Roman, Fernanda F.; Sanches, Lucas F.; Alves da Silva, Fernando; Pereira, Ana I.; Silva, Adrián M.T.; Faria, Joaquim L.; Gomes, Helder T.
This work deals with developing feasible valorization technologies to prepare carbon nanotubes (CNTs) from plastic solid waste and demonstrate their application in catalytic wet peroxide oxidation (CWPO). CNTs were synthesized by catalytic chemical vapor deposition (CCVD) at 850 ºC, considering low-density polyethylene (LDPE), high-density polyethylene (HDPE), and polypropylene (PP) as carbon precursors representative of urban plastic solid waste. Iron oxide nanoparticles supported in alumina, previously synthesized by sol-gel, were used as catalysts in the CCVD process. TEM micrographs allow us to determine 41 nm as the average outer diameter of the CNTs and to visualize magnetic iron nanoparticles (ca. 10 nm) embedded inside the CNTs (ca. 6.4 % of content measured as ashes). These magnetic nanoparticles were kept in the CNT structure even after the purification of the CNTs with sulphuric acid, allowing to obtain magnetic CNTs. All purified and non-purified CNTs prepared from the polyolefins were assessed as catalysts in CWPO of paracetamol (PCM), used as a model pharmaceutical contaminant in water at CPCM,0 = 100 μg mL− 1 (CH2O2,0 = 472 μg mL− 1 , CCNT = 2.5 g L− 1 , pH0 = 3.5 and T = 80 ◦C). The concentrations of PCM, H2O2, aromatic and total phenolic compounds were monitored for 24 h. All CNTs showed catalytic activity, allowing the complete degradation of PCM at 6 h of reaction time. The stability and reusability of materials are tested and proved in CWPO.