Aptamer-functionalized quantum dots as theranostic nanotools against cancer and bacterial infections: A comprehensive overview of recent trends

Aptamers (Apts) are synthetic nucleic acid ligands that can be engineered to target various molecules, including amino acids, proteins, and pharmaceuticals. Through a series of adsorption, recovery, and amplification steps, Apts are extracted from combinatorial libraries of synthesized nucleic acids. Using aptasensors in bioanalysis and biomedicine can be improved by combining them with nanomaterials. Moreover, Apt-associated nanomaterials, including liposomes, polymeric, dendrimers, carbon nanomaterials, silica, nanorods, magnetic NPs, and quantum dots (QDs), have been widely used as promising nanotools in biomedicine. Following surface modifications and conjugation with appropriate functional groups, these nanomaterials can be successfully used in aptasensing. Advanced biological assays can use Apts immobilized on QD surfaces through physical interaction and chemical bonding. Accordingly, modern QD aptasensing platforms rely on interactions between QDs, Apts, and targets to detect them. QD-Apt conjugates can be used to directly detect prostate, ovarian, colorectal, and lung cancers or simultaneously detect biomarkers associated with these malignancies. Tenascin-C, mucin 1, prostate-specific antigen, prostate-specific membrane antigen, nucleolin, growth factors, and exosomes are among the cancer biomarkers that can be sensitively detected using such bioconjugates. Furthermore, Apt-conjugated QDs have shown great potential for controlling bacterial infections such as Bacillus thuringiensis, Pseudomonas aeruginosa, Escherichia coli, Acinetobacter baumannii, Campylobacter jejuni, Staphylococcus aureus, and Salmonella typhimurium. This comprehensive review discusses recent advancements in the design of QD-Apt bioconjugates and their applications in cancer and bacterial theranostics.     

Survival Rate and Enzyme Activities ofLactobacillus acidophilusFollowing Frozen Storage

The ability of two strains of Lactobacillus acidophilus, CRL 640 and CRL 800, to survive and retain their biological activities under frozen storage was determined. Freezing and thawing, as well as frozen storage, damaged the cell membrane, rendering the microorganisms sensitive to sodium chloride and bile salts. Both lactic acid production and proteolytic activity were depressed after 21 days at -20 degreesC, whereas beta-galactosidase activity per cell unit was increased. Cell injury was partially overcome after repair in a salt-rich medium. Copyright 1998 Academic Press.     

Relaxation of a thermal perturbation in a collisional plasma

The relationship between the nonlocal and nonstationary effects in electron heat transport processes in a weakly collisional plasma is investigated by considering the problem of the relaxation of a thermal perturbation as an example. It is shown that, for small-scale perturbations, the electron thermal conductivity depends not only on the temperature scale length but also on time. The consequence is that there exist two qualitatively different characteristic relaxation regimes of thermal perturbations on small and large scale lengths. As a result, the evolution of hot spots in laser plasmas should be described with allowance for the nonstationary nature of electron heat transport. In the course of this evolution, relaxation on the collisional kinetic time scale is clearly seen to change into relaxation on the collisional hydrodynamic time scale.     

Bioactive principles in the bark of Pilidiostigma tropicum

The crude dichloromethane bark extract of Pilidiostigma tropicum (Myrtaceae) from north Queensland, Australia, shows antibacterial and cytotoxic activity. Bioactivity-directed separation led to the isolation of rhodomyrtoxin B and ursolic acid-3-p-coumarate as the biologically active materials. The structures of these compounds were elucidated on the basis of spectral analysis. The intercalation interaction of rhodomyrtoxin B with DNA was investigated using molecular mechanics and ab initio molecular-orbital techniques. A favorable pi-pi interaction between rhodomyrtoxin B and the cytosine-guanine base pair is predicted, but the orientation of the interaction cannot be predicted based on frontier molecular orbitals.     

A miniaturized wide-angle 2D cytometer.

BACKGROUND: We present an optical waveguide based cytometer that is capable of simultaneously collecting the light scattered by cells over a wide range of solid angles. Such comprehensive scattering data are a prerequisite for the microstructural characterization of cells. METHODS: We use latex beads as cell mimics, and demonstrate the ability of this new cytometer to collect back-scattered light in two dimensions (2D). This cytometer is based on a liquid-core optical waveguide, excited by prism coupling, that also serves as the microfluidic channel. In principle, our use of a hemispherical lens allows the collection of scattered light from 0 to 180 degrees in 2D. RESULTS: The experimentally observed positions of the intensity peaks of the back-scattered light agree well with theoretical prediction of scattering from both 4.0- and 9.6-mum diameter latex beads. The position of the bead, relative to the axes of the hemispherical lens and the microchannel, strongly affects the scattering pattern. We discuss a computational method for determining these offsets. CONCLUSIONS: We show that wide-angle 2D light scattering patterns of cell-sized latex beads can be observed in a microfluidic-based optical cytometer that uses leaky waveguide mode excitation. This chip-based system is compatible with emerging chip-based technologies.     

Polymorphism of myosin among skeletal muscle fiber types

An immunocytochemical approach was used to localize myosin with respect to individual fibers in rat skeletal muscle. Transverse cryostat sections of rat diaphragm, a fast-twitch muscle, were exposed to fluorescein-labeled immunoglobulin against purified chicken pectoralis myosin. Fluorescence microscopy revealed a differential response among fiber types, identified on the basis of mitochondrial content. All white and intermediate fiber but only about half of the red fiber reacted with his antimyosin. In addition, an alkali-stable ATPase had the same pattern of distribution among fibers, which is consistent with the existence of two categories of red fibers. The positive response of certain red fibers indicates either that their myosin has antigenic determinants in common with "white" myosin, or that the immunogen contained a "red" myosin. Myosin, extracted from a small region of the pectorlis which consists entirely of white fibers, was used to prepare an immunoadsorbent column to isolate antibodies specific for white myosin. This purified anti-white myosin reacted with the same fibers of the rat diaphragm that had reacted with the white, intermediate, and some red fibers are sufficiently homologous to share antigenic determinants. In a slow-twitch muscle, the soleus, only a minority of the fiber reacted with antipectoralis myosin. The majority failed to respond; hence, they are not equivalent to intermediate fibers of the diaphragm; despite their intermediate mitochondrial content. Immunocytochemical analysis of two different musles of the rat has demonstrated that more than one isoenzyme of myosin can exist in a single muscle, and that individual fiber types can be recognized by immunological differences in their myosin. We conclude that, in the rat diaphragm, there are at least two immunochemically distinct types of myosin and four types of muscle fibers: white, intermediate, and two red. We suggest that these fibers correspond to the four types of motor units described by Burke et al. (Burke, R. E., D. N. Levine, P. Tsairis, and F. E. Zajac, III 1973. J. Physiol. (Lond) 234:723-748.)in the cat gastrocnemius.`     

MPrime: efficient large scale multiple primer and oligonucleotide design for customized gene microarrays

Background  

Enhancements in sequencing technology have recently yielded assemblies of large genomes including rat, mouse, human, fruit fly, and zebrafish. The availability of large-scale genomic and genic sequence data coupled with advances in microarray technology have made it possible to study the expression of large numbers of sequence products under several different conditions in days where traditional molecular biology techniques might have taken months, or even years. Therefore, to efficiently study a number of gene products associated with a disease, pathway, or other biological process, it is necessary to be able to design primer pairs or oligonucleotides en masse rather than using a time consuming and laborious gene-by-gene method.     

Herpes simplex virus triggers and then disarms a host antiviral response

Virus infection induces an antiviral response that is predominantly associated with the synthesis and secretion of soluble interferon. Here, we report that herpes simplex virus type 1 virions induce an interferon-independent antiviral state in human embryonic lung cells that prevents plaquing of a variety of viruses. Microarray analysis of 19,000 human expressed sequence tags revealed induction of a limited set of host genes, the majority of which are also induced by interferon. Genes implicated in controlling the intracellular spread of virus and eliminating virally infected cells were among those induced. Induction of the cellular response occurred in the absence of de novo cellular protein synthesis and required viral penetration. In addition, this response was only seen when viral gene expression was inhibited, suggesting that a newly synthesized viral protein(s) may function as an inhibitor of this response.     

Nonstationary kinetic theory of ion transport in plasma with small perturbations

A theory of charged particle transport for small potential perturbations in a fully ionized plasma is developed on the basis of solving a linearized kinetic equation with the Landau collision integral. This theory is free of any constraints on the characteristic time and spatial scales of perturbations. Ion fluxes appropriate for an arbitrary ion-ion collision frequency that can ensure nonlocal space-time transport in the plasma are calculated. The obtained ion transport coefficients are used to calculate the partial contribution of ions to the longitudinal permittivity of collisional plasma. The resulting expression for the plasma permittivity is applicable in the entire range of frequencies and wavenumbers.