Dual responsive dextran-graft-poly (N-isopropylacrylamide)/doxorubicin prodrug via Schiff base reaction.

Stimulus-responsive nanoparticles stand out in studies for cancer treatment since these systems can promote a selective release of the drug in tumor tissues and cells, minimizing the effects caused by conventional chemotherapy. Dextran-graft-poly (N-isopropylacrylamide) copolymers were synthesized via Schiff base formation. The synthesis of copolymers was confirmed by Fourier transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (NMR) and the analyses of dynamic light scattering (DLS) showed that the copolymers were thermal and pH dual-responsive. The chemotherapy drug doxorubicin (DOX) was conjugated to the copolymers via Schiff base formation, obtaining nanoparticles by self-assembling with size smaller than 130 nm. A higher percentage of doxorubicin was released at pH 5.0 (59.1 ± 2.1%) compared to physiological pH (34.9 ± 4.8%), confirming a pH-sensitive release profile. The in vitro cytotoxicity assay demonstrated that DOX-loaded nanoparticles can inhibit cancer cell proliferation and promote reduced cytotoxicity in non-tumor cells. The D45kP30k-DOX nanoparticles induced morphological changes in HCT-116 cells suggesting cell death and the cell uptake assay indicated that the nanoparticles can be internalized by endocytosis. Therefore, DOX-loaded nanoparticles exhibited potential as smart systems for cancer treatment.

Eco-friendly synthesis of an alkyl chitosan derivative.

Chitosan (CH) was N-alkylated via Schiff base formation and further reduced via sodium borohydride. The reaction was carried out at room temperature, in a homogeneous aqueous medium, using as a source of alkyl group an essential oil (Eucalyptus staigeriana) containing an unsaturated aldehyde (3,7-dimethylocta-2,6-dienal). Derivatives were characterized by Infrared Spectroscopy, proton and carbon Nuclear Magnetic Resonance, XRD, particle size distribution and zeta potential. Chitosan hydrophobization evidence was given by FTIR as new bands at 2929 cm-1 due to methyl groups, along with the presence of strong band at 1580 cm-1 owing to N substitution. Moreover, carbon and proton NMR corroborated the insertion of methyl groups in chitosan backbone. The degree of substitution was found to be in the range 0.69-1.44. X-ray diffractograms revealed that the insertion of alkyl substituents in chitosan backbone led to a less crystalline material. Data from antibacterial activity revealed that chitosan and derivatives were effective against Gram-positive bacteria, whereby derivatives exhibited greater inhibitory effect than CH. Derivatives are likely candidates for use as carriers for active principles of interest of food, pharmacy and medicine.

Influence of galactomannan molar mass on particle size galactomannan-grafted-poly-N-isopropylacrylamide copolymers.

In order to synthesize nanoparticles of galactomannan-g-poly-N-isopropylacrylamide copolymers, galactomannan from fava d'anta was partially hydrolyzed using hydrochloric acid. Degradation reduced the molar mass and increase mannose/galactose molar ratio. This study shows that high molar mass of galatomannan lead to formation of copolymers with particle size in the order of micrometer, however reducing molar mass from 106 to 104 g mol-1, thermo-sensitive copolymer with low critical aggregation concentration, transition temperature close to body temperature (37 °C) and particle size in the range of 300-170 nm can be obtained. As a proof of concept, partially degraded galactomannan-g-NIPAm copolymer was used to incorporated indomethacin. Good encapsulation efficiency and a controlled release were observed indicating that this material has potential to be used as nanocarrier system.