Parameters influencing magnetically enhanced centrifugation for protein separation

Semi-circle magnetophoretic separation under rotated magnetic field for colorimetric biosensing of Salmonella

Magnetic separation was often applied to isolate and concentrate foodborne bacteria using immunomagnetic nanobeads before downstream bacterial detection. However, nanobead-bacteria conjugates (magnetic bacteria) were coexisting with excessive unbound nanobeads, limiting these nanobeads on magnetic bacteria to further act as signal probes for bacterial detection. Here, a new microfluidic magnetophoretic biosensor was elaboratively developed using a rotated high gradient magnetic field and platinum modified immunomagnetic nanobeads for continuous-flow isolation of magnetic bacteria from free nanobeads, and combined with nanozyme signal amplification for colorimetric biosensing of Salmonella. First, the platinum modified immunomagnetic nanobeads were mixed with the bacterial sample to form the magnetic bacteria, and magnetically separated to eliminate non-magnetic background. Then, the mixture of free immunomagnetic nanobeads and magnetic bacteria was injected with sheath flow (PBS) at higher flowrate into the semi-circle magnetophoretic separation channel under rotated magnetic field, which was generated by two repulsive cylindric magnets and their in-between ring iron gear, leading to continuous-flow isolation of magnetic bacteria from free immunomagnetic nanobeads because they suffered from different magnetic forces and thus had different deviating positions at the outlet. Finally, the separated magnetic bacteria and unbound magnetic nanobeads were respectively collected and used to catalyze coreless substrate into blue product, which was further analyzed using the microplate reader to obtain bacterial amount. This biosensor could determinate Salmonella as low as 41 CFU/mL in 40 min.

Mechanistic Study of Protein Adsorption on Mesoporous TiO2 in Aqueous Buffer Solutions

Protein adsorption is of fundamental importance for bioseparation engineering applications. In this work, a series of mesoporous TiO₂ with various geometric structures and different aqueous buffer solutions were prepared as platforms to investigate the effects of the surface geometry and ionic strength on the protein adsorptive behavior. The surface geometry of the TiO₂ was found to play a dominant role in the protein adsorption capacity when the ionic strength of buffer solutions is very low. With the increase in ionic strength, the effect of the geometric structure on the protein adsorption capacity reduced greatly. The change of ionic strength has the highest significant effect on the mesoporous TiO₂ with large pore size compared with that with small pore size. The interaction between the protein and TiO₂ measured with atomic force microscopy further demonstrated that the adhesion force induced by the surface geometry reduced with the increase in the ionic strength. These findings were used to guide the detection of the retention behavior of protein by high-performance liquid chromatography, providing a step forward toward understanding the protein adsorption for predicting and controlling the chromatographic separation of proteins.

Influence of conventional and recent extraction technologies on physicochemical properties of bioactive macromolecules from natural sources: A review

The incorporation of bioactive macromolecules from natural sources into marketable functional foods and nutraceuticals is of major significance to the agri-food sector. Interest in this area of research stems from the application of purified bioactive macromolecules in enhancing food quality and as an alternative to some pharmaceutical drugs for delivery of potential health benefits, with less associated adverse effects. To obtain bioactive macromolecules of high quality, appropriate use of extraction techniques and its influence on sensory and physicochemical properties is paramount. With the advent of technology-aided processes, there has been remarkable improvement in the extraction efficiency of these bioactive agents. An overview of the influence of these new techniques on extraction efficiency and physicochemical properties of proteins, lipids and fibers, which this detailed review provides, will prove to be a valuable resource to food industries aiming to maximize production of bioactive macromolecules from natural sources as well as the scientific community.