Enzymatic Synthesis of α-Glucan Microparticles Using Amylosucrases from Bifidobacterium Species and Its Physicochemical Properties

α-Glucan microparticles (GMPs) have significant potential as high-value biomaterials in various industries. This study proposes a bottom-up approach for producing GMPs using four amylosucrases from Bifidobacterium sp. (BASs). The physicochemical characteristics of these GMPs were analyzed, and the results showed that the properties of the GMPs varied depending on the type of enzymes used in their synthesis. As common properties, all GMPs exhibited typical B-type crystal patterns and poor colloidal dispersion stability. Interestingly, differences in the physicochemical properties of GMPs were generated depending on the synthesis rate of linear α-glucan by the enzymes and the degree of polymerization (DP) distribution. Consequently, we found differences in the properties of GMPs depending on the DP distribution of linear glucans prepared with four BASs. Furthermore, we suggest that precise control of the type and characteristics of the enzymes provides the possibility of producing GMPs with tailored physicochemical properties for various industrial applications.

Ligand-based magnetic extraction and safety assessment of zinc oxide nanoparticles in food products

Zinc oxide (ZnO) is a zinc supplement widely used in health products and is approved by the FDA as Generally Regarded as Safe (GRAS). However, concerns have arisen regarding the potential health effects of nanoscale ZnO, as its reactivity differs from that of its bulk form. This has led to the need for an efficient method to extract ZnO from food products without altering its physicochemical properties, where conventional methods have proven to be inadequate. This study introduces an innovative approach using starch magnetic particles (SMPs) functionalized with a 12-amino acid peptide modified with five lysines (ZBP), that has specific affinity to ZnO. ZBP@SMPs effectively and rapidly extract intact ZnO from food products, achieving recovery efficiencies ranging from 60% to 90%, all while maintaining its morphology and crystallinity. The diameter of ZnO particles recovered from six commercial food products ranged from 25 to 500 nm, with 33% falling below 100 nm, highlighting the need for a size-dependent toxicity study. However, cytotoxicity assessment on human intestinal Caco-2 cells shows all ZnO samples affects cell proliferation and membrane integrity in a dose-dependent manner due to partial dissolution. This study contributes to understanding the safety of ZnO-containing food products and highlights potential health implications associated with their consumption.

Identification of Micrococcin P2-Derivatives as Antibiotic Candidates against Two Gram-Positive Pathogens

Thiopeptides exhibit potent antimicrobial activity against Gram-positive pathogens by inhibiting bacterial protein synthesis. Micrococcins are among the structurally simpler thiopeptides, but they have not been exploited in detail. This research involved a computational simulation of micrococcin P2 (MP2) docking in parallel with the structure-activity relationship (SAR) studied. The incorporation of particular nitrogen heterocycles in the side chain of MP2 enhances the antimicrobial activity. Micrococcin analogues 6c and 6d thus proved to be more effective against impetigo and C. difficile infection (CDI), respectively, as compared to current first-line treatments. Compound 6c also showed a shorter treatment period than that of a first-line treatment for impetigo. This may be attributed to its ability to downregulate pro-inflammatory cytokines. Compound 6d had no observed recurrence for C. difficile and exerted a minimal impact on the beneficial gut microbiome. Their pharmacokinetic properties and low toxicity profile make these compounds ideal candidates for the treatment of impetigo and CDI and validate their involvement in preclinical development.

Short-chain glucan self-assembly for green synthesis of functional biomaterials: Mechanism, synthesis, and microstructural control

Short-chain glucan (SCG) is a linear homopolymer containing 10 to 50 glucose units linked with α(1,4) glycosidic bonds. With its abundant, low-cost, nontoxic, biodegradable/biocompatible nature, self-assembled SCG particles (SSC) have emerged as functional biomaterials, which have recently attracted tremendous attentions in various fields. SCG self-assembly occurs through the spontaneous association of molecules under equilibrium conditions into stable and structurally well-defined nanoscale or micrometer-scale aggregates, which is governed by various intermolecular non-covalent interactions, including hydrogen-bonding, electrostatic, hydrophobic, and van der Waals. With precise and effective control of the self-assembly process of SSC, its structural modulation and function integration can be expected. Thus, we convinced that SCG self-assembly could provide an effective means of developing starch-based functional biomaterials with beneficial health properties and wide application in food industries. In this review, we provide an overview of recent advances in the green approach for the self-assembly of SSC, as well as the influence of thermodynamic and kinetic factors on its morphology and physicochemical properties. We highlight recent contributions to developing strategies for the construction of SSC with increasing complexity and functionality that are suitable for a variety of food applications. Finally, we briefly outline our perspectives and discuss the challenges in the field.

Metal ion-mediated modulation of morphology, physicochemical properties, and digestibility of type 3 resistant starch microparticle

Short-chain glucan (SCG) derived from debranched amylopectin has emerged as a promising candidate for the production of resistant starch particle (RSP) due to its controllable self-assembly features. Here, we investigated the effect of metal cations with different valencies and concentrations on the morphology, physicochemical properties, and digestibility of RSP formed by the self-assembly of SCG. The effect of cations on the formation of RSP followed the valency in the following order: Na⁺, Ka⁺, Mg²⁺, Ca²⁺, Fe³⁺, and Al³⁺, of which 10 mM trivalent cations increased the particle size of RSP over 2 μm and considerably decreased the crystallinity by 49.5 % ~ 50.9 %, which were significantly different from that of mono- and divalent ones. Importantly, RSP formed with divalent cations switched the surface charge from -18.6 mV to 12.9 mV, which significantly increased the RS level, indicating that metal cations would be useful for regulating physicochemical properties and digestibility of RSP.

Correction to: Versatile biotechnological applications of amylosucrase, a novel glucosyltransferase

[This corrects the article DOI: 10.1007/s10068-019-00686-6.].

Impact of solvent polarity on the morphology, physicochemical properties, and digestibility of A-type resistant starch particles

Resistant starch particles (RSP) formed by antisolvent precipitation method has attracted much attention as a functional food ingredient having beneficial effects on obesity and diabetes. However, the effect of solvent polarity on the physicochemical properties and digestibility of RSP remains unclear. Here, n-propanol, isopropanol, acetone, and ethanol were employed as antisolvents to prepare RSP. The width and length of the resulting RSP decreased from 0.87 μm to 0.59 μm and from 2.56 μm to 1.31 μm, respectively, upon increasing the solvent polarity, while dramatically decreasing their crystallinity and the gelatinization enthalpy from 80.5% to 62.3% and from 67.9 ± 14.4 J/g to 41.5 ± 8.3 J/g, respectively, suggesting that solvent polarity is critical factor determining morphology, crystallinity, and thermostability of RSP. Furthermore, the level of resistant starch in RSP was found to be inversely proportional to the degree of solvent polarity, which would provide a useful means for modulating the digestibility of RSP.

Modulation of the self-assembly kinetics and digestibility of type 3 resistant starch particles by co-crystallization with amino acid

The effect of eight different l-amino acids (L-AA) on type-3 resistant starch particles (rSPs) derived from short chain glucan (SCG) was investigated. The L-AA were categorized based on their charge and polarity. The results reveal that positively charged L-AA, such as lysine and arginine, decreased the nucleation and growth rate of rSPs, while non-charged L-AA have negligible effects. Negatively charged L-AA, such as glutamic acid and aspartic acid, had a significant impact on the morphology and crystallinity of the rSPs, resulting in particle size of around 3 μm and crystallinity of around 35%. This implies that charged L-AA influence the arrangement of SCG double helices in the particles. Furthermore, the complexation of SCG with charged L-AA reduced the level of RS in rSPs, indicating that L-AA could be useful in modulating the physical properties and digestibility of rSPs.

Facile preparation of highly uniform type 3 resistant starch nanoparticles

Resistant starch (RS) has emerged as a promising functional food ingredient. To improve the textural and sensory characteristics of RS, there need to be an effective approach to produce RS with well-defined size and shape. Here, we present a facile approach for the synthesis of highly uniform resistant starch nanoparticles (RSNP) based on recrystallization of short-chain glucan (SCG) originated from debranched starch. We found that the ratio of SCG to partially debranched amylopectin was a key parameter in regulating the morphology, size, and crystallinity of the nanoparticles, which enable us to prepare highly uniform RSNP with an average diameter of around 150 nm, while showing a good colloidal stability over a broad range of pH (2-10). Moreover, the in-vitro digestibility and RS content of RSNP was not affected over the ten successive cycles of assembly and disassembly, which would provide useful insights for the development of RS-based functional food ingredients.

Micrococcin P2 Targets Clostridioides difficile

Clostridioides difficile infection is a global public health threat. Extensive in vitro assays using clinical isolates have identified micrococcin P2 (MP2, 1) as a particularly effective anti-C. difficile agent. MP2 possesses a mode of action that differs from other antibiotics and pharmacokinetic properties that render it especially promising. Its time-kill studies have been investigated using hypervirulent C. difficile ribotype 027. DSS (dextran sulfate sodium)-induced in vivo mouse studies with that strain indicate that 1 is better than vancomycin and fidaxomicin. Thus, micrococcin P2 is a valuable platform to be exploited for the development of new anti-C. difficile antibiotics.

Antibacterial Activity against Clinical Isolates and In Vivo Efficacy of Coralmycins

Coralmycins, such as coralmycin A and DH-coralmycin A, have novel molecular skeletons and have been reported to exhibit potent antibacterial activity against standard Gram-positive bacterial strains. Here, the in vitro antibacterial activity against an extensive clinical isolate collection, time-kill kinetics, pharmacokinetics (PK), and in vivo efficacy of coralmycins were studied. Coralmycin A showed potent antibacterial activity with an MIC90 of 1 mg/L against 73 clinical methicillin-resistant Staphylococcus aureus and coagulase-negative staphylococci isolates, which was 2–8 times higher than the corresponding activities of DH-coralmycin A, vancomycin, daptomycin, and linezolid, and against 73 vancomycin-resistant Enterococcus and Streptococcus pneumoniae isolates, which was 4–16 times higher than the corresponding activities of DH-coralmycin A, daptomycin, and linezolid. Pharmacokinetic analysis after i.v. injection showed that coralmycins have a moderate volume of distribution and moderate-to-high clearance in mice. The coralmycin A and DH-coralmycin A bioavailability values were 61.3% and 11.7%, respectively, after s.c. administration. In a mouse respiratory tract infection model, coralmycin A showed bacteriostatic and bactericidal in vivo efficacies at an s.c. administration of 4 and 100 mg/kg bid, respectively; these efficacies were similar to those of vancomycin at 4 and 20 mg/kg bid, respectively. The present findings indicate that coralmycin A has great potential as a new class of antibiotic for treating infections caused by multidrug-resistant Gram-positive bacteria.

Effect of organic acids on the morphology and particle size of titanium dioxide (E171) in processed food

TiO₂ (E171) is widely used in processed food as a coloring agent. However, growing concerns about the potential health effects of TiO₂ nanoparticles (< 100 nm) have necessitated the need for monitoring the size distribution and cytotoxic properties of food additive TiO₂ present in commercial food. In this study, we employed magnetic separation method to extract food additive TiO₂ from 100 commercial foods. The extracted TiO₂ had a mean particle diameter of 121-143 nm along with the fraction in nanoscale (< 100 nm) ranging from 7.5% to 35.7%, where certain types of food, such as candy and jelly, were shown to contain smaller TiO₂ with higher fraction of nanoscale particles. Assuming that the low pH of the products with high content of organic acid is responsible for the smaller TiO₂, the effect of three organic acids, such as acetic acid, ascorbic acid, and citric acid, on the physicochemical property of TiO₂ was investigated. The citric acid was shown to reduce the size of TiO₂ along with the generation of fragmented nanoparticles with a size of around 20 nm, whereas the effect of acetic acid and ascorbic acid was negligible. Although TiO₂ treated with citric acid did not exhibit short-term cytotoxicity, this study suggests the importance of fully assessing the potential long-term health effect of food additive TiO₂ whose physicochemical properties were altered in processed food.

Nitro-Group-Containing Thiopeptide Derivatives as Promising Agents to Target Clostridioides difficile

The US Centers for Disease Control and Prevention (CDC) lists Clostridioides difficile as an urgent bacterial threat. Yet, only two drugs, vancomycin and fidaxomicin, are approved by the FDA for the treatment of C. difficile infections as of this writing, while the global pipeline of new drugs is sparse at best. Thus, there is a clear and urgent need for new antibiotics against that organism. Herein, we disclose that AJ-024, a nitroimidazole derivative of a 26-membered thiopeptide, is a promising anti-C. difficile lead compound. Despite their unique mode of action, thiopeptides remain largely unexploited as anti-infective agents. AJ-024 combines potent in vitro activity against various strains of C. difficile with a noteworthy safety profile and desirable pharmacokinetic properties. Its time-kill kinetics against a hypervirulent C. difficile ribotype 027 and in vivo (mouse) efficacy compare favorably to vancomycin, and they define AJ-024 as a valuable platform for the development of new anti-C. difficile antibiotics.

Bleeding risk in patients with atrial fibrillation treated with combined anti-platelet and NOAC therapy

Background

The combined use of antiplatelet agents (APT) and non-vitamin K antagonist oral anticoagulants (NOACs) in patient with atrial fibrillation (AF) is commonly encountered in clinical practice. The purpose of this study was to compare the clinical outcomes between combination therapy (NOAC and APT) and monotherapy (NOAC only).

Methods and results

We analyzed patients who were prescribed NOACs between January 2012 and December 2016. The primary outcome was major or any bleeding events and the secondary outcomes were stroke/systemic embolism (SE) and major adverse cardiac events (MACE). Of 1,068 participants, there were 264 (24.7%) patients in the combination group.

The prevalence of diabetes (p=0.017) and history of stroke and transient ischemic attacks (p&lt;0.001) was higher in the combination group than in the monotherapy group. During the mean 14.6±9.8 months of follow-up, the incidence of any bleeding was significantly higher in the combination group than in the monotherapy group (p&lt;0.001). Major bleeding, stroke/SE, and MACE between the two groups were similar. The rate of under-dosage NOACs prescriptions was higher in the combination group than in the monotherapy group (p=0.024).

Conclusions

The combination therapy had higher incidences of any bleeding events compared to the monotherapy. However, there was no difference in stroke/SE and MACE.

The bleeding risk in patients taking the combination of NOACs and APT should be carefully evaluated.

Funding Acknowledgement

Type of funding sources: None. Figure 1. Primary and secondary outcomes

Modulation of the peroxidase-like activity of iron oxide nanoparticles by surface functionalization with polysaccharides and its application for the detection of glutathione

Here, we employed three polysaccharides, such as dextran, hyaluronic acid, and chitosan, for surface modification of iron oxide nanoparticles (IONPs) and carried out in-depth investigation to elucidate the effect of surface functionalities on the peroxidase (POD) like activity of IONPs. The affinity of substrates to the catalytic site of IONPs was found to be determined by the surface functional groups and hydration layer of polysaccharide coating on the surface of IONPs. The role of hydration layer was further confirmed by the results that the POD-like activity of IONPs coated with a certain polysaccharide having higher water holding capacity was significantly enhanced by salting-out reagent, such as ammonium chloride that is known to reduce the thickness of hydration layer. Moreover, the excellent catalytic activity of dextran-coated IONPs was successfully applied to develop a highly sensitive sensing system for the detection of glutathione (GSH) with a limit of detection of 2.3 nM.

The volume of left atrium measured by multi-detector computed tomography can predict of long term outcome in catheter ablation of atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

This study aimed to identify the volume left atrium (LA) and left atrial appendage (LAA) calculated by multidetector computed tomography (MDCT) is related to the long term out come of radiofrequency catheter ablation (RFCA) for atrial fibrillation(AF).

Methods

We analyzed data from 99 consecutive patients who referred for RFCA due to drug-refractory symptomatic AF (age 56 ± 10 years; 74% men; 64% paroxysmal AF). Prior to the procedure, all patients underwent ECG-gated 128 channels MDCT scan for assessment for pulmonary vein  anatomy, LA and LAA volume estimation, and electro-anatomical mapping integration. 

Results

The volume of LA and LAA calculated by CT was 142.6 ± 32.2 mL and 14.7 ± 6.0 mL, respectively. LA volume was smaller in paroxysmal AF(PAF) than persistent AF(PeAF) (133.9 ± 29.3 mL vs. 158.0 ± 31.4 mL, p &lt; 0.0001) but  LAA volume was not significantly different between PAF and PeAF(13.9 ± 5.0 mL vs. 16.3 ± 7.3 mL, p = 0.09). Patients were classified into 2 groups by the LA volume of 160mL; group 1  (LA volume &lt; 160mL,n = 73) and group 2 (LA volume ≥160mL, n = 26). After a mean follow up 12.6 ± 5.3 months, 78.8% of the patients maintained sinus rhythm after the index ablation. AF free survival was significantly greater in group  1 than group 2 (84.9% vs. 61.5% p = 0.017). No relationship was found between LAA volume and the outcome of RFCA. Multivariate analysis showed that the LA volume &gt;160mL was an independent predictor of arrhythmia-free after ablation (Hazard ration 2.55, 95% confidential interval 1.02-6.35, p = 0.045)

Conclusion

Higher LA volume is independent risk factor for AF recurrence after RFCA but not LAA volume. The LA volume quickly assessed by MDCT could be a good predictor of long term recurrence after AF ablation.

Supraparticle Engineering for Highly Dense Microspheres: Yttria-Stabilized Zirconia with Adjustable Micromechanical Properties

Various supraparticles have been extensively studied owing to their excellent catalytic properties that are attributed to their inherent porous structure; however, their mechanical properties have not garnered attention owing to their less dense structure. We demonstrate a rational approach for fabricating assembled supraparticles and, subsequently, highly dense microspheres. In addition, 3 mol % yttria-stabilized zirconia (3YSZ) and alumina particles were selected as building blocks and assembled into higher-order architectures using a droplet-based template method (spray drying) for validation with proof-of-concept. Moreover, structural features such as density, size, sphericity, and morphology of supraparticles were controlled by adjusting the competing kinetics occurring between the assembly of building blocks and evaporation of the solvent in the droplets. The preparatory aqueous suspension and process parameters were optimized as well. A detailed understanding of the formation mechanism facilitated the yield of tailor-made supraparticles and, thereafter, highly dense microspheres (approximate relative density = 99%) with excellent sphericity (>98%) via heat treatment. The microspheres displayed highest hardness (26.77 GPa) and superior elastic modulus (210.19 GPa) compared with the mechanical properties of the 3YSZ samples reported to date. Ultimately, the proposed supraparticle engineering provided insight for controlling the structural features and resultant micromechanical properties, which widely extends the applicability of supraparticle-based functional materials for practical purposes that require materials with high density and excellent mechanical properties.

Biosynthesis of glyceride glycoside (nonionic surfactant) by amylosucrase, a powerful glycosyltransferase

Amylosucrase (ASase, E.C. 2.4.1.4) is a powerful transglycosylation enzyme that can transfer glucose from sucrose to the hydroxyl (-OH) group of various compounds. In this study, recombinant ASases from Deinococcus geothermalis (DgAS) and Bifidobacterium thermophilum (BtAS) were used to synthesize biosurfactants based on the computational analysis of predicted docking simulations. Successful predictions of the binding affinities, conformations, and three-dimensional structures of three surfactants were computed from receptor-ligand binding modes. DgAS and BtAS were effective in the synthesis of biosurfactants from glyceryl caprylate, glyceryl caprate, and polyglyceryl-2 caprate. The results of the transglycosylation reaction were consistent for both ASases, with glyceryl caprylate acceptor showing the highest concentration, as confirmed by thin layer chromatography. Furthermore, the transglycosylation reactions of DgAS were more effective than those of BtAS. Among the three substrates, glyceryl caprylate glycoside and glyceryl caprate glycoside were successfully purified by liquid chromatography-mass spectrometry (LC-MS) with the corresponding molecular weights.

Natural Plant Extracts and Compounds for Rheumatoid Arthritis Therapy

Natural plant extracts and compounds (NPECs), which originate from herbs or plants, have been used in the clinical treatment of rheumatoid arthritis (RA) for many years. Over the years, many scientists have carried out a series of studies on the treatment of RA by NPEC. They found a high quantity of active NPECs with broad application prospects. In view of various complex functions of these NPECs, exploring their potential as medicines for RA treatment will be beneficial for RA patients. Thus, to help advance the development of high-quality NPECs for RA, we herein aimed to review the research progress of NPECs in the treatment of RA in recent years. Our findings showed that, from the pharmacological perspective, natural plant extracts or mixed herbal compounds effectively regulate the immune system to alleviate RA by inhibiting pro-inflammatory cytokines. Further, individualized medication can be applied according to each patient's physical condition. However, the pathogenesis of RA and its immune mechanism has not been fully understood and requires further studies.

Synthetic Ligand-Coated Starch Magnetic Microbeads for Selective Extraction of Food Additive Silicon Dioxide from Commercial Processed Food

The amorphous form of silicon dioxide has long been regarded as a safe food additive (E551) that is widely used in commercially processed food as an anticaking agent. However, starting with titanium dioxide, there have been growing safety concerns regarding to the use of nanoscale silicon dioxide particles in food as food additives. The size, morphology, and chemical properties of inorganic food materials are important parameters to determine its potential toxicity. Therefore, an effective means of extracting an intact form of SiO₂ from food without altering the physicochemical property of SiO₂ particles is of great need to accurately monitor its characteristics. Here, we report on an effective magnetic separation method to extract food additive SiO₂ from food by utilizing a diatom-originated peptide with a specific affinity to SiO₂ particles. The affinity-based magnetic separation was found to be specific to SiO₂ particles over other types of inorganic food additives such as titanium dioxide and zinc oxide. The size and morphology of SiO₂ were shown to not be affected by the extraction processes. This method was successfully applied to extract and characterize the food additive SiO₂ from six different types of commercial food.

Impact of starch granule-associated channel protein on characteristic of and λ-carrageenan entrapment within wheat starch granules

This study investigated the physicochemical characteristics of protease-treated wheat starch (PT-WST) to understand the role of starch granule-associated proteins (SGAPs) and the potential capability of PT-WST to provide a nutrient delivery system (NDS). Protease treatment was conducted at 4 °C and 37 °C (PT04 and PT37), respectively. A model delivery system was assessed with PT37 granules infiltrated by λ-carrageenan (λC) under variations of molecular size (λC hydrolysates produced from 0, 2.5, 100, and 500 mM HCl solution), agitation time, and temperature. Protein-specific (3-(4-carboxybenzyl)quioline-2-carboxaldehyde) or non-reactive (methanolic merbromin) fluorescent dye staining revealed that removal of SGAPs on surfaces and channels were more effective for PT37 than for PT04. Consistent amylose content, swelling, and gelatinization temperature before and after protease treatment suggested minimal impact on the starch structure. PT37 presented higher solubility and pasting viscosity than PT04. This resulted from excessive SGAP removal, which enhanced entrapment capacity. λC molecular size and agitation temperature showed a negative correlation with the content of λC entrapped within PT37, and this content depended on the interplay between the agitation time and λC molecular size. As λC molecular size decreased, the λC distribution became uniform throughout the granules, which confirmed the potential of PT-WST as a carrier for NDS.

Paper-based colorimetric detection of pathogenic bacteria in food through magnetic separation and enzyme-mediated signal amplification on paper disc

Herein, we report a colorimetric sensing system for the detection of highly virulent bacteria, Escherichiacoli O157:H7, in sausage by utilizing magnetic separation and enzyme-mediated signal amplification on paper disc. For magnetic separation, Poly-l-lysine coated starch magnetic particles (PLL@SMPs) were synthesized and utilized for the separation and concentration of the bacteria in sample suspension. Horseradish peroxidase-conjugated antibody (HRP-Antibody) and 3,3',5,5'- tetramethylbenzidine (TMB) were employed for the specific signal amplification in the presence of target bacteria. The synthesized PLL@SMPs showed an excellent capture efficiency (>90%) for the pathogenic bacteria in large volume sample suspension. The intrinsic problems associated with the non-specific binding of sensing components that lead to the high background signal and low sensitivity in colorimetric detection was successfully resolved by employing hyaluronic acid as a blocking agent. The effective separation and concentration of target bacteria by PLL@SMPs and target-specific signal amplification with exceptionally high signal to noise ratio enabled the detection of target bacteria with a detection limit in the single digit regime. The sensing system proposed in this study was successfully used for the detection of the target pathogenic bacteria, E. coli O157:H7, in sausage sample with the limit of detection (LOD) as low as 30.8 CFU/mL with 95% probability. The simple nature of paper-based detection system with a great sensitivity and specificity would provide an effective means of evaluating the safety of food and environmental samples.

Tertiary RNA Folding-Targeted Drug Screening Strategy Using a Protein Nanopore

Bacterial riboswitch RNAs are attractive targets for novel antibiotics against antibiotic-resistant superbacteria. Their binding to cognate metabolites is essential for the regulation of bacterial gene expression. Despite the importance of RNAs as therapeutic targets, the development of RNA-targeted, small-molecule drugs is limited by current biophysical methods. Here, we monitored the specific interaction between the adenine-sensing riboswitch aptamer domain (ARS) and adenine at the single-molecule level using α-hemolysin (αHL) nanopores. During adenine-induced tertiary folding, adenine-bound ARS intermediates exhibited characteristic nanopore events, including a two-level ionic current blockade and a ∼ 5.6-fold longer dwell time than that of free RNA. In a proof-of-concept experiment, tertiary RNA folding-targeted drug screening was performed using a protein nanopore, which resulted in the discovery of three new ARS-targeting hit compounds from a natural compound library. Taken together, these results reveal that αHL nanopores are a valuable platform for ultrasensitive, label-free, and single-molecule-based drug screening against therapeutic RNA targets.

Preparation of starch-based drug delivery system through the self-assembly of short chain glucans and control of its release property

Here, we report a starch-based carrier system for the delivery of insoluble bioactive compound via oral route. We utilized the intrinsic characteristics of debranched amylopectins that self-assemble into a spherical microparticle in aqueous environment to encapsulate guest molecules. Upon complexation with β-cyclodextrin, the model bioactive compound, curcumin (CUR), was effectively incorporated into the starch microparticles (SMPs) to form CUR-CD@SMPs during the self-assembly reaction. The stability of encapsulated curcumin against environmental stresses, such as photodegradation and chemical oxidation, was greatly enhanced upon encapsulation. The size of CUR-CD@SMPs could be precisely controlled from 0.3 μm to 2 μm by modulating the rate of debranching reaction. A change of release profiles from concave-downward to sigmoidal form was observed upon increasing the size of CUR-CD@SMPs, suggesting that the release site could be controlled by modulating the crystallinity or size of the carrier microparticles.

Charge-switchable magnetic separation and characterization of food additive titanium dioxide nanoparticles from commercial food

Growing concerns about the potential health effects of nanoscale titanium dioxide (TiO₂) have necessitated the need for monitoring the size distribution and physicochemical properties of food additive TiO₂ that are present in commercial food. Acid digestion is by far the most widely used method to remove interfering food matrices, but the highly corrosive nature of the reaction could alter the physicochemical properties of the TiO₂, which may give a skewed information about the materials. Here, we report an effective approach to extract intact form of food additive TiO₂ nanoparticles from processed food through charge-charge interaction between TiO₂ particles and charge-switchable starch magnetic beads (PL@SMBs), of which the captured TiO₂ is readily harvested by switching the surface charge of PL@SMBs to neutral. The size and surface property of extracted TiO₂ were shown to be well maintained due to the mild nature of the reaction. The extracted TiO₂ particles from 10 commercial processed food showed a size distribution from 40 to 250 nm with a mean diameter of 115 nm, of which 22 % of them were less than 100 nm. The extracted TiO₂ did not exhibit short-term cytotoxicity, but induced cellular oxidative stress at high concentration.

Determination of the fate and biological responses of food additive silica particles in commercial foods

Synthetic amorphous silica (SAS) is widely added to commercial foods as an anticaking agent. Concern about the potential application of nanosized silica in foods has increased as nanomaterials are not intended for use as food additives. This study evaluated the particle size distributions and biological responses of food additive SAS. An accurate, sensitive, and cost-effective analytical method for probing SAS was established, and quantitative analysis of its presence in commercial foods was performed. The results demonstrate that food additive SAS is an aggregated material composed of nanosized particles with nanosized aggregates of silica particles identified in commercial foods. Food additive SAS did not exhibit acute cytotoxicity compared to both general-grade nano (G-nano) and bulk (G-bulk) silica. Moreover, intestinal transport amounts of food additive SAS were significantly lower than for G-nano. Taken together, we find that food additive SAS does not exhibit acute toxicity resulting from nanosized materials.

Gold Nanoparticle-Coated Starch Magnetic Beads for the Separation, Concentration, and SERS-Based Detection of E. coli O157:H7

Here, we report gold nanoparticle-coated starch magnetic beads (AuNP@SMBs) that were prepared by in situ synthesis of AuNPs on the surface of SMBs. Upon functionalization of the surface with a specific antibody, the immuno-AuNP@SMBs were found to be effective in separating and concentrating the target pathogenic bacteria, Escherichia coli O157:H7, from an aqueous sample as well as providing a hotspot for surface-enhanced Raman scattering (SERS)-based detection. We employed a bifunctional linker protein, 4× gold-binding peptide-tagged Streptococcal protein G (4GS), to immobilize antibodies on AuNP@SMBs and AuNPs in an oriented form. The linker protein also served as a Raman reporter, exhibiting a strong and unique fingerprint signal during the SERS measurement. The amplitude of the SERS signal was shown to have a good correlation with the concentration of target bacteria ranging from 10⁰ to 10⁵ CFU/mL. The detection limit was determined to be as low as a single cell, and the background signals derived from nontarget bacteria were negligible due to the excellent specificity and colloidal stability of the immuno-AuNP@SMBs and SERS tags. The highly sensitive nature of the SERS-based detection system will provide a promising means to detect the pathogenic microorganisms in food or clinical specimen.

Multidrug-resistant tuberculosis in South Korea: a retrospective analysis of national registry data in 2011-2015

BACKGROUND: Multidrug-resistant tuberculosis (MDR-TB) poses a threat to public health as a result of high treatment costs and unsatisfactory outcomes.OBJECTIVE: To elucidate trend, demographic and clinical characteristics and treatment outcomes of patients with MDR-TB between 2011 and 2015 in South Korea.METHOD: Data of patients with MDR-TB diagnosed between 1 January 2011 and 31 December 2015 were retrieved from the nationwide Internet-based TB notification system and analysed retrospectively.RESULTS: During the study period, 5192 MDR-TB patients were notified. We identified an increasing number of MDR-TB patients among foreign populations (from 1.3% to 7.7%), decreasing resistance rates to other anti-TB drugs (e.g., resistance to pyrazinamide, from 40.9% to 28.2%), a decreasing interval from treatment initiation to negative conversion of sputum culture (from 165.7 to 103.7 days) and shortening of treatment duration (719.7 to 613.2 days). However, treatment success rates did not change, and had an average of 65.7%.CONCLUSION: Despite decreasing resistance rates to other drugs and faster treatment responses, treatment outcomes did not improve during the study period. Strict management of MDR-TB patients on treatment should be adopted to improve treatment outcomes.

Versatile biotechnological applications of amylosucrase, a novel glucosyltransferase

Amylosucrase (AS; EC 2.4.1.4) is an enzyme that has great potential in the biotechnology and food industries, due to its multifunctional enzyme activities. It can synthesize α-1,4-glucans, like amylose, from sucrose as a sole substrate, but importantly, it can also utilize various other molecules as acceptors. In addition, AS produces sucrose isomers such as turanose and trehalulose. It also efficiently synthesizes modified starch with increased ratios of slow digestive starch and resistant starch, and glucosylated functional compounds with increased water solubility and stability. Furthermore, AS produces turnaose more efficiently than other carbohydrate-active enzymes. Amylose synthesized by AS forms microparticles and these can be utilized as biocompatible materials with various bio-applications, including drug delivery, chromatography, and bioanalytical sciences. This review not only compares the gene and enzyme characteristics of microbial AS, studied to date, but also focuses on the applications of AS in the biotechnology and food industries.

Impacts of pre-rigor salting with KCl on technological properties of ground chicken breast

The objective of this study was to determine the impact of pre-rigor salting using KCl on the technological properties of ground chicken breast. Chicken breast muscle (M. pectoralis major and minor) was hot-debonded and salted with 2% NaCl (w/w), 1% NaCl+1% KCl mixture, or 2% KCl, respectively, within 30 min after slaughter. Post-rigor salting treatment was prepared with 2% NaCl at 24 h postmortem. All pre-rigor salting treatments showed higher ultimate pH, protein solubility, and final yield than post-rigor salting treatment (P < 0.05). However, the positive effects of pre-rigor salting on chicken breast differed by salt type. Pre-rigor salting with KCl resulted in higher ultimate pH and R-values of chicken breast than pre-rigor salting with NaCl (P < 0.05). Despite the high ultimate pH, pre-rigor salting with KCl resulted in lower protein solubility, final yield, and hardness of chicken breast than pre-rigor salting with NaCl (P < 0.05). These results indicate that pre-rigor salting with KCl could contribute to the maintenance of relatively excellent technological properties of pre-rigor chicken breasts compared to post-rigor salted chicken breast. However, this current study also suggests that the impact of KCl on technological properties in pre-rigor chicken breast, such as water-holding capacity, protein solubility, and texture, could be less effective than pre-rigor salting with NaCl at an identical percentage concentration.

Paper-Based Radial Chromatographic Immunoassay for the Detection of Pathogenic Bacteria in Milk

Here, a paper-based radial flow chromatographic immunoassay (RFCI) employing gold nanoparticles (AuNPs) as chromatic agents was developed for the detection of Escherichia coli O157:H7 in whole milk. A 4-repeated gold-binding peptide-tagged (4GBP) streptococcal protein G (SPG) fusion protein was constructed as a bifunctional linker to immobilize antibodies on the surface of AuNPs with a well-oriented form based on the specific affinity of GBP and SPG to the gold and Fc portion of the antibody, respectively. 4GS@AuNPs prepared with the bifunctional linker protein exhibited excellent colloidal stability even at high salt concentrations of up to 500 mM, which is a critical requirement for its application to a broad range of biological and food samples. The enhanced colloidal stability and excellent binding capability of the immuno-4GS@AuNPs toward target bacteria lowered the detection limit of RFCI for target pathogenic bacteria in whole milk as low as 10³ CFU/mL, which is by an order of magnitude lower than that of conventional immuno-AuNPs prepared with physical adsorption of antibodies. The RFCI pattern could also be converted into a grayscale value by simple image processing for quantitative determination of target pathogenic bacteria. This paper-based detection system would provide an effective means of monitoring the presence of food-borne pathogens in real food samples with naked eyes.

Alpha-Hederin Nanopore for Single Nucleotide Discrimination

Various types of biological and synthetic nanopores have been developed and utilized for the high-throughput investigation of individual biomolecules. Biological nanopores made with channel proteins are so far superior to solid-state ones in terms of sensitivity and reproducibility. However, the performance of a biological nanopore is dependent on the protein in the channel structure its dimensions are predetermined and are difficult to modify for broader applications. Here inspired by the cytotoxic mechanisms of a saponin derivative, alpha-hederin, we report a nonproteinaceous nanopore that can be formed spontaneously in a lipid membrane. We propose the pore-forming mechanism of alpha-hederin in a cholesterol-rich lipid membrane and a strategy to control the pore-forming rate by a lipid partitioning method. The small diameter and effective thickness of alpha-hederin nanopores enabled us to discriminate ssDNA homopolymers as well as four types of nucleotides, showing its potential as a DNA sequencing tool.

Paper-based lateral flow strip assay for the detection of foodborne pathogens: principles, applications, technological challenges and opportunities

As a representative colorimetic biosnesor, paper-based LFSA have emerged as a promising and robust tool that can easily and instansly detect the presence of target biological components in food sample. Recently, LFSAs have gained a considerable attention as an alternative method for rapid diagnosis of foodborne pathogens to the conventional culture-based assays such as plate counting and PCR. One major drawback of the current LFSAs for the detection of pathogenic bacteria is the low sensitivity, limiting its practical applications in POCT. Not like many other protein-based biomarkers that are present in nM or pM range, the number of pathogenic bacteria that cause disease can be as low as few CFU/ml. Here, we review current advances in LFSAs for the detection of pathogenic bacteria in terms of chromatic agents and analyte types. Furthermore, recent approaches for signal enhancement and modifications of the LFSA architecture for multiplex detection of pathogenic bacteria are included in this review, together with the advantages and limitations of each techniques. Finally, the technological challenges and future prospect of LFSA-based POCT for the detection of pathogenic bacteria are discussed.

A low-noise silicon nitride nanopore device on a polymer substrate

We report a novel low-noise nanopore device employing a polymer substrate. The Si substrate of a fabricated Si-substrate-based silicon nitride (Si3N4) membrane was replaced with a polymer substrate. As such, laser machining was used to make a micro-size hole through the polyimide (PI) substrate, and a thin Si3N4 membrane was then transferred onto the PI substrate. Finally, a nanopore was formed in the membrane using a transmission electron microscope for detection of biomolecules. Compared to the Si-substrate-based device, the dielectric noise was greatly reduced and the root-mean-square noise level was decreased from 146.7 to 5.4 pA. Using this device, the translocation of double-strand deoxyribonucleic acid (DNA) was detected with a high signal/noise (S/N) ratio. This type of device is anticipated to be available for future versatile sequencing technologies.

Molecular Rearrangement of Glucans from Natural Starch To Form Size-Controlled Functional Magnetic Polymer Beads

Herein, we report a fairly simple and environmentally friendly approach for the fabrication of starch-based magnetic polymer beads (SMPBs) with uniform shape and size through spontaneous rearrangement of short-chain glucan (SCG) produced by enzymatic debranching of waxy maize starch. The paramagnetic materials, dextran-coated iron oxide nanoparticles (Dex@IONPs), were readily incorporated into the starch microstructure and rendered a superparamagnetic property to the SMPBs. The morphology and size of resulting SMPBs turned out to be modulated by Dex@IONPs in a concentration-dependent manner, of which Dex@IONPs was assumed to be acting as a seed inducing the epitaxial crystallization of SCG and further transforming it into homogeneous microparticles. The surface of SMPBs was readily functionalized with an antibody through a one-step reaction using a linker protein. The immuno-SMPBs showed great capture efficiency (>90%) for target bacteria. The colloidal stability and favorable surface environment for biomolecules are believed to be responsible for the high capture efficiency and specificity of the SMPBs. Furthermore, the captured bacteria along with antibody and linker protein were effectively eluted from the surface of SMPBs by adding free maltose, making this new material suitable for various chromatographic applications.

Nanopore based detection of Bacillus thuringiensis HD-73 spores using aptamers and versatile DNA hairpins

A versatile nanopore sensing platform to detect any aptamer using nanopores by designing DNA hairpins that are complementary to the aptamer is described. This platform can detect the presence of aptamer binding targets regardless of their size, which has been a major hurdle for nanopore detection systems. Moreover, the signal-to-noise ratio is increased by eliminating most of the unwanted substances from the sample via simple sample preparation steps. To detect Bacillus thuringiensis HD-73 spores using this sensing platform, DNA hairpins complementary to the target-specific aptamers were designed, and the hairpins were characterized using alpha-hemolysin nanopores after the reaction of spores and aptamers and subsequent reaction with the complementary DNA hairpins. The platform exhibited a detection limit as low as 1.2 × 101 CFU mL-1 and was compatible with a wide range of spore concentrations from 1.2 × 101 CFU mL-1 to 1.2 × 106 CFU mL-1 while it is still expandable to higher spore concentrations.

Reduction of DNA Folding by Ionic Liquids and Its Effects on the Analysis of DNA-Protein Interaction Using Solid-State Nanopore

DNA folding is not desirable for solid-state nanopore techniques when analyzing the interaction of a biomolecule with its specific binding sites on DNA since the signal derived from the binding site could be buried by a large signal from the folding of DNA nearby. To resolve the problems associated with DNA folding, ionic liquids (ILs), which are known to interact with DNA through charge-charge and hydrophobic interactions are employed. 1-n-butyl-3-methylimidazolium chloride (C4 mim) is found to be the most effective in lowering the incident of DNA folding during its translocation through solid-state nanopores (4-5 nm diameter). The rate of folding signals from the translocation of DNA-C4 mim is decreased by half in comparison to that from the control bare DNA. The conformational changes of DNA upon complexation with C4 mim are further examined using atomic force microscopy, showing that the entanglement of DNA which is common in bare DNA is not observed when treated with C4 mim. The stretching effect of C4 mim on DNA strands improves the detection accuracy of nanopore for identifying the location of zinc finger protein bound to its specific binding site in DNA by lowering the incident of DNA folding.

Rapid Identification of Vibrio Species Isolated from the Southern Coastal Regions of Korea by MALDI-TOF Mass Spectrometry and Comparison of MALDI Sample Preparation Methods

Vibrio species are generally recognized as pathogens predominant in seafood along coastal areas. The food industry has sought to develop efficient microbial detection methods. Owing to the limits of conventional methods, this study aimed to establish a rapid identification method for Vibrio isolated from Korea, based on matrix-assisted laser-desorption/ionization timeof- flight mass spectrometry (MALDI-TOF MS). Four different preparation procedures were compared to determine the appropriate means to pretreat Vibrio species, using 17 isolates and five reference strains. Extended direct transfer and full formic acid extraction methods using bacterial colonies on agar plates revealed very low identification rates. Formic acid and trifluoroacetic acid (TFA) extractions using bacterial broth cultures were also performed. All Vibrio isolates and reference strains prepared by TFA extraction were successfully identified to the species level (17/22, 77.3%) and to the genus level (5/22, 22.7%). Thus, TFA extraction was considered the most appropriate method to pretreat Vibrio species for MALDI-TOF MS. The remaining 33 isolates and two reference strains were prepared by TFA extraction and analyzed by MALDI-TOF MS. Overall, 50 isolates were identified to the species level (40/50, 80%) and to the genus level (10/50, 20%). All isolates were identified as 43 V. alginolyticus, six V. parahaemolyticus, and one V. vulnificus species. V. alginolyticus and V. parahaemolyticus were isolated from fish offal (87.5% and 12.5%, respectively), seawater (91.3%, 8.7%), and shellfish (62.5%, 37.5%), whereas V. alginolyticus and V. vulnificus were isolated from sediment (90.9% and 9.1%, respectively). This study established a reliable system of MALDI-TOF MS preparation and analysis for Vibrio identification.

Transdermal water-in-oil nanocarriers of nitric oxide for triggering penile erection

Men’s sexual health can have significant effects on a man’s self-esteem, sexual relationship and male reproductive functions. Although commercially available drugs (e.g., VIAGRA and CIALIS) show effective treatment of erectile dysfunction (ED), patients with severe ED fail to respond to these medicines. Topical nitric-oxide (NO) delivery to penis can be a painless, alternative solution with severe ED because NO triggers erection and diffuses to the trabecular arteries and smooth muscles in the penis. We here develop water-in-oil (W/O) nanoemulsions (NEs) that contain NO and can directly spread on the penis. We optimize NE formation conditions including hydrophilic-lipophilic balance (HLB) and ratio of oil, water and surfactants. Then, by spreading NEs on penis skin of intact middle aged dogs, we verify medication effects and safety of the NEs in vivo. The water-in-oil NEs can be a promising non-invasive medication for ED patients with low response to a phosphodiesterase type 5 (PDE5) inhibitor, thus increasing quality of life in the aging society.