Rapid PCR kit: lateral flow paper strip with Joule heater for SARS-CoV-2 detection.

Polymerase chain reaction (PCR)-based diagnostic kits for point-of-care (POC) testing are highly desirable to prevent the spread of infectious diseases. Here, we demonstrate a rapid PCR testing kit that involves integrating a lateral flow paper strip with a nichrome-based thin film heater. The use of a paper membrane as a PCR-solution container results in fast thermocycling without a cooler because the membrane can contain the solution with a high specific surface area where Joule heating is applied. After PCR, amplified products are simultaneously detected at the lateral flow paper strip with the naked eye. Severe acute respiratory syndrome ß-coronavirus RNA can be detected within 30 min after PCR solution injection. This work reveals that the paper membrane can act as not only a capillary flow channel but also as a promising platform for fast PCR and detection.

Molecular Damage Detection in an Elastomer Nanocomposite with a Coumarin Dimer Mechanophore.

Molecular force probes that generate optical responses to critical levels of mechanical stress (mechanochromophores) are increasingly attractive tools for identifying molecular sites that are most prone to failure. Here, a coumarin dimer mechanophore whose mechanical strength is comparable to that of the sulfur-sulfur bonds found in vulcanized rubbers is reported. It is further shown that the strain-induced scission of the coumarin dimer within the matrix of a particle-reinforced polybutadiene-based co-polymer can be detected and quantified by fluorescence spectroscopy, when cylinders of the nanocomposite are subjected to unconstrained uniaxial stress. The extent of the scission suggests that the coumarin dimers are molecular "weak links" within the matrix, and, by analogy, sulfur bridges are likely to be the same in vulcanized rubbers. The mechanophore is embedded in polymer main chains, grafting agent, and cross-linker positions in a polymer composite in order to generate experimental data to understand how macroscopic mechanical stress is transferred at the molecular scale especially in highly entangled cross-linked polymer nanocomposite. Finally, the extent of activation is enhanced by approximately an order of magnitude by changing the regiochemistry and stereochemistry of the coumarin dimer and embedding the mechanophore at the heterointerface of the particle-reinforced elastomer.

Label-Free Direct Detection of Saxitoxin Based on a Localized Surface Plasmon Resonance Aptasensor.

Seafood is an emerging health food, and interest in improving the quality of seafood is increasing. Saxitoxin (STX) is a neurotoxin produced by marine dinoflagellates that is accumulated in seafood. It can block the neuronal transmission between nerves and muscle cell membranes, resulting in the disturbance of neuromuscular transmission and subsequent voluntary muscle paralysis. Here, we developed a new aptamer for the detection of STX using graphene oxide-systematic evolution of ligands by exponential enrichment (GO-SELEX). Furthermore, we confirmed sensitivity and selectivity of the developed aptamer specific to STX using a localized surface plasmon resonance (LSPR) sensor. The sensing chip was fabricated by fixing the new STX aptamer immobilized on the gold nanorod (GNR) substrate. The STX LSPR aptasensor showed a broad, linear detection range from 5 to 10,000 µg/L, with a limit of detection (LOD) of 2.46 µg/L (3σ). Moreover, it was suitable for the detection of STX (10, 100, and 2000 µg/L) in spiked mussel samples and showed a good recovery rate (96.13-116.05%). The results demonstrated that the new STX aptamer-modified GNR chip was sufficiently sensitive and selective to detect STX and can be applied to real samples as well. This LSPR aptasensor is a simple, label-free, cost-effective sensing system with a wide detectable range.

An optical fiber-based LSPR aptasensor for simple and rapid in-situ detection of ochratoxin A.

Label-free biosensing methods that rely on the use of localized surface plasmon resonance (LSPR) have attracted great attention as a result of their simplicity, high sensitivity, and relatively low cost. However, in-situ analysis of real samples using these techniques has remained challenging because colloidal nanoparticles (NPs) can be unstable at certain levels of pH and salt concentration. Even in the case of a chip-type LSPR sensor that can resolve the instability problem by employing NPs immobilized on the substrate, loading of a sample to sensor chip with exact volume control can be difficult for unskilled users. Herein, we report an optical-fiber-based LSPR aptasensor that can avoid these problems and serve as a portable and simple system for sensitive detection of a small mycotoxin, ochratoxin A (OTA), in real samples. The optical fiber coated with aptamer-modified gold nanorods (GNRs) is simply dipped into a solution containing OTA and subjected to LSPR analysis. Quantitative analysis of OTA is performed by measuring the spectral red shift of the LSPR peak of GNRs. Under optimized conditions, the LSPR peak shift displays a linear response (R2 = 0.9887) to OTA in the concentration range from 10pM to 100nM, with a limit of detection of 12.0pM (3S). The developed sensor shows a high selectivity for OTA over other mycotoxins such as zearalenone (ZEN) and ochratoxin B (OTB), and shows an accurate detection capability for OTA in real grape juice samples.

The Mechanical Strength of a Mechanical Bond: Sonochemical Polymer Mechanochemistry of Poly(catenane) Copolymers.

Topological molecular connections and structures, including physical entanglements in polymer networks, knots along polymer chains, and rotaxanes in sliding ring gels, have important consequences for the physical properties of polymeric materials. Often these topologies contribute through their ability to bear mechanical stress, but experimental measures of their relative mechanical strength are rare. Here, we use sonochemical polymer mechanochemistry to assess the relative mechanical strength of a multicatenane copolymer relative to copolymers of cyclic and linear analogs. The relative mechanical strengths are obtained by comparing the limiting molecular weights (Mlim ) and contour lengths (Llim ) of the polymers under pulsed ultrasound of their dilute solutions. The values of Mlim and Llim , and thus the inferred mechanical strengths of the polymers, are effectively identical. The mechanical bonds of the catenanes are therefore as strong, or stronger, mechanically as the covalent bonds along the polymer backbone.

Relative Mechanical Strengths of Weak Bonds in Sonochemical Polymer Mechanochemistry.

The mechanical strength of scissile chemical bonds plays a role in material failure and in the mechanical activation of latent reactivity, but quantitative measures of mechanical strength are rare. Here, we report the relative mechanical strength of polymers bearing three putatively "weak" scissile bonds: the carbon-nitrogen bond of an azobisdialkylnitrile (<30 kcal mol(-1)), the carbon-sulfur bond of a thioether (71-74 kcal mol(-1)), and the carbon-oxygen bond of a benzylphenyl ether (52-54 kcal mol(-1)). The mechanical strengths are assessed in the context of chain scission triggered by pulsed sonication of polymer solutions, by using two complementary techniques: (i) the competition within a single polymer chain between the bond scission of interest and the nonscissile mechanochemical ring opening of gem-dichlorocyclopropane mechanophores and (ii) the molecular weights at long (4 h) sonication times of multimechanophore polymers. The two methods produce a consistent story: in contrast to their thermodynamic strengths, the relative mechanical strengths of the three weak bonds are azobisdialkylnitrile (weakest) < thioether < benzylphenyl ether. The greater mechanical strength of the benzylphenyl ether relative to the thermodynamically stronger carbon-sulfur bond is ascribed to poor mechanochemical coupling, at least in part as a result of the rehybridization that accompanies carbon-oxygen bond scission.

A novel allylic transfer reaction of chirally modified 2-borylbutadiene: synthesis of chiral homoallenyl alcohols.

An enantioselective synthesis of the homoallenyl alcohols was achieved from the reaction of chiral 2-borylbutadiene with aldehydes through an allylic transfer reaction in good yields and enantioselectivities.

Cytokine responses induced by Mycobacterium tuberculosis in patients with HIV-1 infection and tuberculosis.

OBJECTIVE: Tuberculosis (TB) is an important opportunistic infection in HIV patients. Immune responses to Mycobacterium tuberculosis in HIV/TB patients were evaluated. METHODS: Fifteen patients with HIV/TB, ten with HIV, four with TB, and five controls were enrolled. Peripheral blood mononuclear cells were isolated and stimulated with mycobacterial antigen (PPD). Interferon (IFN)-gamma and TNF-alpha in culture supernatants were measured by ELISA. RESULTS: IFN-gamma and TNF-alpha production after PPD stimulation was markedly decreased in HIV patients, but not in HIV/TB patients. In HIV patients with a CD4 cell count of less than 200/mm3, IFN-gamma and TNF-alpha production after PPD stimulation was higher in HIV/TB patients than in HIV patients. Cytokine responses to M. tuberculosis reconstituted after highly active antiretroviral therapy (HAART) and were prominent in HIV/TB patients. CONCLUSIONS: Cytokine responses to M. tuberculosis were retained in HIV-infected patients with tuberculosis, even in patients with a CD4 cell count of less than 200/mm3, and reconstituted after HAART.

A high frequency of macrolide-lincosamide-streptogramin resistance determinants in Staphylococcus aureus isolated in South Korea.

Genes conferring resistance to one of the macrolide-lincosamide-streptogramin (MLS) antibiotics may confer cross-resistance to others, because they have similar effects on bacterial protein synthesis. In Korea, over 70% of Staphylococcus aureus isolates are methicillin-resistant and erythromycin-resistant methicillin-resistant S. aureus (MRSA) is also prevalent. We investigated the frequency of MLS resistance in erythromycin-resistant S. aureus isolates. A total of 682 isolates of S. aureus were collected in a nationwide antibiotic resistance survey. Susceptibility to erythromycin, clindamycin, and quinupristin/dalfopristin was tested by disk diffusion. In all, 37% of the methicillin-susceptible S. aureus (MSSA) and 97% of the MRSA isolates were resistant to at least one of the MLS antibiotics, whereas all were susceptible to quinupristin/dalfopristin. Out of 518 strains that were resistant to erythromycin, 60 clindamycin-susceptible (30 MSSA, 30 MRSA) and 44 clindamycin-resistant isolates (14 MSSA, 30 MRSA) were selected at random from these strains. Thirteen genes related to MLS resistance were detected in these isolates by PCR. Of the 104 MSSA and MRSA strains tested, 98 harbored one or more erm gene. The most common was erm(A), with erm(C) next. But, msr(A), lnu(A), and mef(A) were rare and no resistance to streptogramin A was encountered.

Inhibition of HIV-1 integrase by galloyl glucoses from Terminalia chebula and flavonol glycoside gallates from Euphorbia pekinensis.

The bioassay-directed isolation of Terminalia chebula fruits afforded four human immunodeficiency virus type 1 (HIV-1) integrase inhibitors, gallic acid ( 1) and three galloyl glucoses ( 2 - 4). In addition, four flavonol glycoside gallates ( 5 - 8) from Euphorbia pekinensis containing the galloyl moiety also showed the inhibitory activity at a level comparable to those of 2 - 4. By comparison with the activities of the compounds not bearing this moiety, it is proposed that the galloyl moiety plays a major role for inhibition against the 3'-processing of HIV-1 integrase of these compounds.