In this study, magnetite nanoparticles were successfully synthesized using Calotropis procera aqueous leaf extract. The effect of the whole extract and some of its phytochemicals on the particle size distribution was determined using Dynamic light scattering (DLS) while other characterizations such as UV–vis spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) spectroscopy and Scanning electron microscopy (SEM) were carried out. The antimicrobial activity against selected microorganisms was also studied using the agar well diffusion method. The leaf extract showed the presence of phenols, flavonoids, saponins, alkaloids and tannins. The magnetite nanoparticle synthesized using the leaf extract (Calotropis procera/Fe3O4) had an average particle size of 11.1nm with a PDI of 0.142 while the phenolic, flavonoid and saponin extracts of Calotropis procera leafs produced magnetites with average particle sizes of 62.83nm, 68.02nm and 134nm respectively. The UV-vis spectra displayed the characteristic plasmon resonance peak at 420nm, the FTIR plots highlighted important functional groups including peaks between 600cm-1 and 400cm-1 confirming the formation of iron oxide while the SEM micrographs showed the nanoparticles were mainly irregular in shape with areas of agglomeration. Calotropis procera/Fe3O4 displayed significant anti-microbial activity against Staphylococcus aureus, Bacillus subtilis, Klebsiella pneumonia, Aspergillus niger and Fusarium oxysporum while no activity was recorded against Escherichia coli. The study indicated that Calotropis procera leaf extract was suitable for the green synthesis of magnetite with properties that suggest that it could be potentially applied as antimicrobial nanofillers.

Background: Crosslinking is one method of starch modification that has been applied to improve the properties of starch and starch-based films. The effects of different crosslinkers on some properties of starch give an insight into the impact the crosslinking modification will have on the final behaviour of starch films. The aim of this study was to analyse the effects of oxidized sucrose and citric acid crosslinking on cassava starch intended for packaging film applications. Methods: Cassava starch was crosslinked with oxidized sucrose and citric acid individually and also in combination (dual modification). The properties studied were amylose content, degree of substitution (DS), degree of crosslinking (DC), solubility, swelling power and paste clarity while FTIR, SEM, XRD and thermal analysis were also carried out. Results: The optimal concentrations of oxidized sucrose and citric acid in this study were 1% and 5% resulting in a maximum amylose content of 20.78 and 19.4 respectively while an intermediate DS (0.182- 0.401) was recorded for all crosslinked starches. The swelling power and solubility of oxidized sucrose crosslinked starch (OS-starch) was lower than that of citric acid crosslinked starch (CA-starch) in all the temperatures observed. The SEM, XRD as well as FTIR analysis highlighted changes in the crystalline structure of starch granules after the crosslinking. Thermo-gravimetric analysis indicated that the thermal stability of all starches was significantly improved by crosslinking, as residual weights of 18.74%, 19.59% and 19.68% were observed for CA-starch, OS-starch, and dual modified starch (OS-CA starch) respectively. Conclusion: Overall, the study suggests that although both crosslinkers significantly improved the physicochemical properties of cassava starch studied, oxidized sucrose had higher effect on most these properties, hence can be suggested to be better suitable when modifying starch for packaging film applications.