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.

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.

Ionic liquids (ILs) are organic salts with low melting point by asymmetric ionic strength between cation and anion. They have been known as promising DNA extraction, separation and preservation agent due to their hydrophilic, hydrophobic interaction with DNA. However, few studies have been performed about how DNA-ILs complexes form and their mechanism. Herein, we present three types of ionic liquids (EMIM-Cl, BMIM-Cl, and OMIM-Cl) change the DNA structure depend on alkyl chain length of ionic liquids. Structural changes of DNA by ionic liquids are observed by Atomic force microscopy, gel electrophoresis, zeta potential and solid-state nanopore technology. The results of AFM show the different structures of DNA, including aggregate, stretching, and bundling shapes in terms of EMIM-Cl, BMIM-Cl, and OMIM-Cl respectively. In DNA translocation experiment, DNA/EMIM-Cl show rare translocation signal due to aggregated structure by neutralized surface charge. DNA/BMIM-Cl and DNA/OMIM-Cl show slowing down the translocation speed due to changes of DNA net charge and structure. Especially, OMIM-Cl make slowing down the DNA translocation speed about 102~104 times compared to translocation speed of bare DNA by unzipping the bundling shape of complex. In conclusion, the morphology of DNA could be modified by the incorporation with different alkyl chain length of ILs, providing their further application in nanopore technique for slowing DNA sequencing or understanding protein-DNA interaction.

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.

Ionic liquids (ILs) have been used in DNA extraction/separation, DNA preservation and PCR based on their characteristic affinity to DNA. However, few studies have been performed about how DNA-IL complex forms and its mechanism which would be essential to understand the role of ILs over the range of applications. Herein, we present that the differences in the structure of the DNA- IL complex are associated with the alkyl chain length of IL. The assumption was evidenced by Atomic force microscopy, DNA specific dye staining, gel-electrophoresis and real-time electrical measurement. We observed unique electrical signals with altered duration time and amplitude when DNA- ILs complexes pass through solid-state nanopore. We examined three types of ILs (EMIM-Cl, BMIM-Cl, and OMIM-Cl) for their characteristics to form DNA-ILs complexes. The results indicated that the length of hydrophobic alkyl group in respective ILs determines the form of DNA-IL complex. In conclusion, the morphology of DNA could be modified by the incorporation with different alkyl chain length of ILs, providing their further application in biosensor such as nanopore technique for DNA sequencing or understanding protein-DNA interaction.

Various methods for the detection of E. coli O157:H7 in food have been developed in the past decades. However, current detection methods require specialized instruments and lengthy preparation time. In an effort to achieve a rapid and sensitive detection, we developed a radial chromatography (RC) biosensor integrated with gold nanoparticle (AuNP) conjugated with antibody for the detection of E. coli O157:H7. The immuno-AuNP binds to E. coli O157:H7 creating AuNP-E. coli O157:H7 complexes by specific antigen-antibody interaction. The AuNP-E. coli O157:H7 complexes can be identified clearly from free AuNP by RC based on their mobility on porous matrix. Thus, the AuNP complexed with target bacteria, E. coli O157:H7 could be discriminated from free AuNP by radial chromatography. The results showed that the developed RC biosensor is highly selective to E. coli O157:H7 over non-target bacteria, including Bacillus cereus, Staphylococcus aureus and Vibrio cholerae with a detection limit of 105 CFU/ml. When combined with a pre-concentration step using immunomagnetic beads, we could further enhance the detection limit down to 103 CFU/ml. In this study, we developed a novel method that is rapid, sensitive and applicable for qualitative and quantitative detection of E. coli O157:H7. The detection procedure is simple and the results can be easily determined by naked eyes, suggesting that this system is practical and can be applied to the field diagnosis in food industry for the detection of pathogenic bacteria.