Laminated paper-based analytical devices (LPAD) with origami-enabled chemiluminescence immunoassay have been developed for the detection of cotinine, a secondhand smoke (SHS) biomarker. The devices were fabricated by a craft-cutter to define flow channels, followed by lamination. This approach of cutting/lamination to fabricate LPAD is very similar to making an identification card, offering advantages in simplicity and rugged backing when compared to the common method of patterning paper using SU-8 or wax. We also developed a protocol of localized incision and paper-folding to isolate the detection zone from flow channels; the simple origami step eliminated possible reagent diffusion and flow during antibody immobilization steps and numerous washings. By incorporating luminol-based chemiluminescence for detecting horseradish peroxidase-conjugated cotinine, we employed origami-enabled LPAD to detect cotinine in mouse serum using competitive immunoassay. The detection limit was determined to be 5 ng/mL, a clinically relevant concentration. We believe that LPAD with chemiluminescence detection provides a new platform of low cost and sensitive assays for cotinine detection.
Rats and genetically manipulated mouse models have played an important role in the exploration of molecular causes of cardiovascular diseases. However, it has not been fully investigated whether mice or rats and humans manifest similar patterns of ventricular wall motion. Although similarities in anatomy and myofiber architecture suggest that fundamental patterns of ventricular wall motion may be similar, the considerable differences in heart size, heart rate, and sarcomeric protein isoforms may yield quantitative differences in ventricular wall mechanics. To further our understanding of the basic mechanisms of myofiber contractile performance, we quantified regional and global indexes of ventricular wall motion in mice, rats, and men using magnetic resonance (MR) imaging. Both regular cine and tagged MR images at apical, midventricular, and basal levels were acquired from six male volunteers, six Fischer 344 rats, and seven C57BL/6 mice. Morphological parameters and ejection fraction were computed directly from cine images. Myocardial twist (rotation angle), torsion (net twist per unit length), circumferential strain, and normalized radial shortening were calculated by homogeneous strain analysis from tagged images. Our data show that ventricular twist was conserved among the three species, leading to a significantly smaller torsion, measured as net twist per unit length, in men. However, both circumferential strain and normalized radial shortening were the largest in male subjects. Although other parameters, such as circumferential-longitudinal shear strain, need to be evaluated, and the causes of these differences in contractile mechanics remain to be elucidated, the preservation of twist appears fundamental to cardiac function and should be considered in studies that extrapolate data from animals to humans.
Receptors are crucial to the analytical performance of
sensor arrays.
Different from the previous receptors in sensor arrays, herein, peroxidase-mimicking
DNAzymes were innovatively used as receptors to develop a label-free
chemiluminescence sensor array for discriminating various heavy metal
ions in complex samples. The peroxidase-mimicking DNAzymes are composed
of functional oligonucleotides and hemin, including G-triplex-hemin
DNAzyme (G3-DNAzyme), G-quadruplex-hemin DNAzyme (G4-DNAzyme), and
the dimer of G-quadruplex-hemin DNAzyme (dG4-DNAzyme). Circular dichroism
(CD) spectroscopy demonstrated that different metal ions diversely
affect the conformation of G-quadruplex and G-triplex, resulting in
a change in the activity of peroxidase-mimicking DNAzyme. Thus, the
unique fingerprints formed to easily discriminate seven kinds of heavy
metal ions by principal component analysis (PCA) within 20 min. The
discrimination of unknown metal ions in tap water further confirmed
its ability for discriminating multiple heavy metal ions. Moreover,
it will not bring water pollution due to the good biocompatibility
of DNA. Therefore, it not only merely offers a label-free, rapid,
environment-friendly, and cheap (1.49 $) sensor assay for discriminating
metal ions but also comes up with an innovative way for developing
sensor arrays.
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