PEGAylated graphene oxide/superparamagnetic nanocomposite as a high-efficiency loading nanocarrier for controlled delivery of methotrexate.

Polymer-coated nanocarriers play an important role in targeted drug delivery. The use of polymers such as polyethylene glycol increases stability, biocompatibility, and blood circulation time of the drug, and may consequently improve the success of drug delivery. In the present work, a simple approach has been reported for synthesizing polyethylene glycol bis amin (PEGA) functionalized graphene oxide/iron oxide nanocomposite as a remarkable unit for loading drugs. The biomedical applications of the synthesized nanocomposite were investigated by immobilizing methotrexate (MTX), as an anticancer drug. The structural and morphological characteristics and the successful synthesis of the nanocomposite were evaluated by different charachterization techniques. The cytotoxicity assay of the nanocarrier showed higher toxicity against HeLa and MCF-7 cell lines, compared to free MTX. The drug release experiments in acidic and physiological conditions suggested the first order kinetics model for the release of MTX from the nanocomposite. Furthermore, the agglutination, complement activation, and coagulation time experiments demonstrated the blood compatibility of the synthesized nanocarrier.

Physicochemical and crystalline properties of standard maize starch hydrothermally treated by direct steaming.

The changes in physicochemical properties of standard maize starch (SMS) by three hydrothermal treatments; DV-HMT (Direct Vapor-Heat Moisture Treatment), RP-HMT (Reduced Pressurized-Heat Moisture Treatment) and DIC (instantaneous controlled pressure drop) were investigated at different processing conditions; steam pressure (SP) varied from 1 to 3bar during 20min. Starch was steamed by direct contact, whose interest was to intensify the heat transfer phenomenon but also the water transfer. The physicochemical changes of SMS depended on process conditions and their extent followed this order: DIC>RP-HMT>DV-HMT. All treatments significantly increased gelatinization temperatures and decreased the enthalpies, confirmed by loss of granules birefringence. From 2bar, the crystalline structure changed from A-type to Vh-type, revealing formation of amylose-lipid complexes during steaming. The results clearly showed that the particle size distribution depends on the melting extent of crystalline structure during treatment. At severe processing conditions the melted fraction increased and more complex aggregates of different sizes have been formed.

Role of vacuum steps added before and after steaming treatment of maize starch. Impact on pasting, morphological and rheological properties.

Standard maize starch (SMS) was hydrothermally treated by three processes; DV-HMT (Direct Vapor-Heat Moisture Treatment), RP-HMT (Reduced-Pressurized Heat Moisture Treatment) and DIC (in French: Détente Instantanée Contrôlée, instantaneous controlled pressure drop). Impact of processes were studied in order to determine the role of added steps of vacuum before and after treatment of starch by live steam at different pressures (1, 1.5, 2, 2.5 and 3 bar) on morphological, pasting (Brabender) and rheological properties of SMS suspension. The three treatments tend to modify the physical properties of starch on the same way, but the extent of these modifications depends on the process and on the level presure applied. The intensity of modifications follows this order: DIC>RP-HMT>DV-HMT. This was attributed to the presence of the initial vacuum step (DIC and RP-HMT) which intensified the transfer phenomena and to the mechanical effect induced by the abrupt decompression towards vacuum (DIC) leading to weakness of starch granules. The treatments changed the shape and distribution size of granules. The sizes were shifted towards higher values after the treatment due both to the improvement of swelling capacity of granules and to the presence of agglomerates particles of different sizes as confirmed by scanning electron microscopy. The agglomerates glued together by gelatinized granules were favored by the direct contact of starch with steam during the treatments. The results showed for all treatments, a reduction of the consistency coefficient (k) and of the yield stress (τ0) of starch suspensions with increasing of process intensity. For severe conditions (3 bar), no difference between the treatments was observed; a complete fluidization of starch suspensions (the consistencies were too weak to be detected), τ0 vanished and the rheological behavior tended to a Newtonian type. Elastic modulus (G'), measured during gelation at 25°C, decreased dramatically (G'<1 Pa), that revealed the loss of rigidity and disappearance of granular integrity of starch.