Amylose is carbohydrate polymer defined as a linear natural polysaccharide composed of α(1→4) bound glucose units. Due to its abundance, renewable nature, low cost, and biodegradability, this polymer is regarded as a promising green material for producing crystals and particles of different sizes ranging from the nanometer scale to the micrometer scale. Herein, short amylose chains and dextran-coated iron oxide magnetic nanoparticles (Dex@IONPs) were introduced to fabricate well-dispersed starch magnetic microbeads (SMMBs), which have a well-defined spherical shape and a uniform size of about 1 μm. We found that the aggregation of SMMBs can be mediated by the introduced Dex@IONPs in a concentration-dependent manner, indicating that Dex@MNPs, as the seed crystals, play an important role in self-assembly of SMMBSs. By using streptococcal protein G tagged with maltose binding protein (MBP-SPG), specific antibody against Escherichia coli O157:H7 was successfully immobilized on the surface of SMMBs. The Ab-functionalized SMMBs showed a high capture efficiency (>90%) comparable to the commercial immunomagnetic microparticles regardless of suspending agents (1X PBS and milk). Moreover, SMMBs exhibited excellent recyclability, in which the Ab immobilized on the surface of SMMBs can be refreshed by using the maltose elution buffer along with the unchanged capture efficiency. In addition, SMMBSs were assembled into the linear rod-shape microstructure by the introduced magnetic field during the amylose-mediated precipitation process. The convenient self-assembly of SMMBs with the well-defined size and shape, biocompatibility, tolerance to environmental variances, high magnetic response behavior, and excellent recyclability in the functionalization make these magnetic microparticles promising for many potential applications such as bio-sensing, labeling, and smart delivery of active compounds.

The outbreaks of foodborne diseases associated with bacterial contamination are still critical issues all over the world. To ensure food safety, the diagnosis of pathogenic bacteria on site at early state of contamination are required. Escherichia coli O157:H7 (E. Coli O157:H7) is one of the major factor causing foodborne diseases. We introduce a sandwich type colorimetric detection method integrated with chitosan-coated starch magnetic polymer beads(CS@SMBs) that can separate and concentrate bacteria in aqueous environment. For signal amplification, horseradish peroxidase-conjugated antibody (HRP-Antibody) and 3,3',5,5'- tetramethylbenzidine (TMB) were employed as enzyme label and chromogenic substrate, respectively. We demonstrate that CS@SMBs not only show a good magnetic sensitivity, but also can capture a variety of bacteria regardless of Gram-negative and Gram-positive, which offer possibility for separation of the broad range of bacteria from food matrix. Our approach successfully captures E. coli O157:H7 with detection limit of 101 CFU/mL through naked eye, making promise of fast, on-site, and sensitive detection of pathogenic bacteria.

Ionic liquid (IL), asymmetric chemical consist of bulky cations and tiny-mobile anions, has been known as promising DNA extraction, separation and preservation agent due to its strong interaction with DNA. However, the interaction underlying DNA-IL complex forming mechanism remains to be elucidated. Herein, we employed three types of ILs (EMIM-Cl, BMIM-Cl, and OMIM-Cl) to investigate the changes of DNA morphology upon the alkyl chain length of ILs by using solid-state nanopore technology combining with atomic force microscopy (AFM). The results of AFM show the different forms of DNA, including aggregate, stretching, and bundling shapes in terms of EMIM-Cl, BMIM-Cl, and OMIM-Cl, respectively, assuming that the shape of DNA-IL complexes is responding to the alkyl chain length of ILs. In DNA translocation experiment. From the alteration of blockade current signals during the DNA pass through the nanopore, we estimate that the shapes of DNA are changed due to the treatment with BMIM-Cl, and OMIM-Cl, which not only increased the blockade current signals about 2-4 times in the case of OMIM, but also decrease the event showing translocation of DNA folding, implying that the alkyl chain affect to DNA stretching and bundling. The results indicate the length of hydrophobic alkyl group of IL plays an important role in determination of DNA morphology, providing their further application in nanopore technique for slowing DNA translocation speed toward discovering protein-DNA interaction or DNA sequencing.

Due to the globalization of food supply have been growing, there have been a great demands for food safety and quality assuarance for on-site detection. On-site detetction isuue is the process should be fast, simple, user-friendly and require minimal equipments. Herein, we developed a Radial chromatography (RC) biosensor integrated with the immuno-gold nanoparticles-coated magnetic nanoparticle (AuNPs@Fe3O4) for specific separation and detection of the target bacteria, E. coli O157:H7, in sample. The immuno-AuNPs@Fe3O4 specifically binds to E.coli O157:H7 creating AuNP@Fe3O4-E.coli complexes and captured bacteria were concentrated by magnet. The complex can be identified with inner ring derived from the difference of mobility of free AuNPs@Fe3O4 on the RC sensor. Our results show that AuNPs@Fe3O4 based RC sensor has high sensitivity to the target bacteria over non-target bacteria with a detection limit of 103 CFU/ml. Our system offers a rapid and sensitive means of detecting E.coli O157:H7 with naked eyes, which can be applied to the field diagnosis.

Amylose is carbohydrate polymer defined as a linear natural polysaccharide composed of α(1→4) bound glucose units. Due to its abundance, renewable nature, low cost, and biodegradability, this polymer is regarded as a promising green material for producing crystals and particles of different sizes ranging from the nanometer scale to the micrometer scale. Herein, short amylose chains and dextran-coated iron oxide magnetic nanoparticles (Dex@MNPs) were introduced to fabricate individual superparamagnetic amylose microparticles (SAMPs), which have a well-defined spherical shape and a uniform size of about 1 μm. We found that the aggregation of SAMPs can be mediated by the introduced Dex@MNPs in a concentration-dependent manner, indicating that Dex@MNPs, as the seed crystals, play an important role in self-assembly of SAMPs. By using streptococcal protein G tagged with maltose binding protein (MBP-SPG), specific antibody against Escherichia coli O157:H7 was successfully immobilized on the surface of SAMPs. The Ab-functionalized SAMPs showed a high capture efficiency (>90%) comparable to the commercial immunomagnetic microparticles regardless of suspending agents (1X PBS and milk). Moreover, SAMPs exhibited excellent recyclability, in which the Ab immobilized on the surface of SAMPs can be refreshed by using the maltose elution buffer along with the unchanged capture efficiency. In addition, SAMPs were assembled into the linear rod-shape microstructure by the introduced magnetic field during the amylose-mediated precipitation process. The convenient self-assembly of SAMPs with the well-defined size and shape, biocompatibility, tolerance to environmental variances, high magnetic response behavior, and excellent recyclability in the functionalization make these magnetic microparticles promising for many potential applications such as bio-sensing, labeling, and smart delivery of active compounds.