Influence of chitosan modification on self-assembly behavior of Fe3O4 nanoparticles

Ultrafast protein digestion using an immobilized enzyme reactor following high-resolution mass spectrometry analysis for rapid identification of abrin toxin

Abrin toxin, highly dangerous with an estimated human lethal dose of 0.1-1 μg per kg body weight, has attracted much attention regarding criminal and terroristic misuse over the past decade. Therefore, developing a rapid detection method for abrin toxin is of great significance in the field of biosecurity. In this study, based on the specific dissociation method of an immobilized enzyme reactor, the trypsin immobilized reactor Fe3O4@CTS-GA-Try was prepared to replace free trypsin, and the immobilized enzyme digestion process was systematically investigated and optimized by using bovine serum albumin as the simulant of abrin. After 5 min one-step denaturation and reduction, a satisfactory peptide number and coverage were yielded with only 15 s assisted by an ultrasound probe to identify model proteins. Subsequently, abrin was rapidly digested using the established method, resulting in a stable and highly reproducible characteristic peptide number of 39, which can be analyzed by nanoelectrospray ionization coupled with high-resolution mass spectrometry. With the acquisition mode of full MS scan coupled with PRM, not only MS spectroscopy of total abrin peptides but also the corresponding MS/MS spectroscopy of specific abrin peptides can achieve the characteristic detection of abrin toxin and its different isoforms in less than 10 minutes, with high repeatability. This assay provides a universal platform and has great potential for the development of on-site detection and rapid mass spectrometric analysis techniques for macromolecular protein toxins and can further be applied to the integrated detection of chemical and biological agents.

Synthesis of chitosan-based grafting magnetic flocculants for flocculation of kaolin suspensions

A series of novel chitosan-based magnetic flocculants FS@CTS-P(AM-DMC) was prepared by molecular structure control. The characterization results showed that FS@CTS-P(AM-DMC) had a uniform size of about 21.46 nm, featuring a typical core-shell structure, and the average coating layer thickness of CTS-P(AM-DMC) was about 5.03 nm. FS@CTS-P(AM-DMC) exhibited excellent flocculation performance for kaolin suspension, achieved 92.54% turbidity removal efficiency under dosage of 150 mg/L, pH 7.0, even at high turbidity (2000 NTU) with a removal efficiency of 96.96%. The flocculation mechanism was revealed to be dominated by charge neutralization under acidic and neutral conditions, while adsorption and bridging effects play an important role in alkaline environments. The properties of magnetic aggregates during flocculation, breakage, and regeneration were studied at different pH levels and dosages. In the process of magnetophoretic, magnetic particles collide and adsorb with kaolin particles continuously due to magnetic and electrostatic attraction, transform into magnetic chain clusters, and then further form three-dimensional network magnetic aggregates that can capture free kaolin particles and other chain clusters. Particle image velocimetry confirmed the formation of eddy current of magnetic flocs and experienced three stages: acceleration, stabilization, and deceleration.

Magnetic Nanoparticles for Protein Separation and Purification

Proteins are essential for various functions such as brain activity and muscle contraction in humans. Even though food is a source of proteins, the bioavailability of proteins in most foods is usually limited due to matrix interaction with other biomolecules. Thus, it is essential to extract these proteins and provide them as a nutraceutical supplement to maintain protein levels and avoid protein deficiency. Hence, protein purification and extraction from natural sources are highly significant in biomedical applications. Chromatography, crude mechanical disruption, use of extractive chemicals, and electrophoresis are some of the methods applied to isolate specific proteins. Even though these methods possess several advantages, they are unable to extract specific proteins with high purity. A suitable alternative is the use of nanoparticles, which can be beneficial in protein purification and extraction. Notably, magnetic iron and iron-based nanoparticles have been employed in protein extraction processes and can be reused via demagnetization due to their magnetic property, smaller size, morphology, high surface-to-volume ratio, and surface charge-mediated property. This chapter is a summary of various magnetic nanoparticles (MNPs) that can be used for the biomolecular separation of proteins.