Colloidal gold and its application in cell biology

Acoustic Wave (TSM) Biosensors: Weighing Bacteria

This chapter is focused on the development and use of acoustic wave biosensor platforms for the detection of bacteria, specifically those based on the thickness shear mode (TSM) resonator. We demonstrated the mechanical and electrical implications of bacterial positioning at the solid-liquid interface of a TSM biosensor and presented a model of the TSM with bacteria attached operating as coupled oscillators. The experiments and model provide an understanding of the nature of the signals produced by acoustic wave devices when they are used for testing bacteria. The paradox of “negative mass” could be a real threat to the interpretation of experimental results related to the detection of bacteria. The knowledge of the true nature of “negative mass” linked to the strength of bacteria attachment will contribute significantly to our understanding of the results of “weighing bacteria.” The results of this work can be used for bacterial detection and control of processes of bacterial settlement, bacterial colonization, biofilm formation, and bacterial infection in which bacterial attachment plays a role.

Bionanotechnology progress and advances

Advances in the nanotechnology research have provided a new set of research tools, materials, structures, and systems for biological and medical research and applications. These nanotechnologies include the application of fluorescent quantum dots for optical imaging, the design of metallic nanoparticle surfaces for ultrasensitive biomolecular fingerprinting, and the use of nanostructures as hyperthermia agents for cancer therapy. Unlike conventional technologies, unique properties can be incorporated into nanometer-size particles, structures, and systems simply by changing their size, shape, and composition. Because of the tunable properties, biologists and clinicians could custom-design a material for a specific research need. In this review article, we highlight the recent advances and progress in Bionanotechnology research as well as provide future perspective on this integrative field.

Freeze-substitution: origins and applications

Freeze-substitution is a physicochemical process in which biological specimens are immobilized and stabilized for microscopy. Water frozen within cells is replaced by organic solvents at subzero temperatures. Freeze-substitution is widely used for ultrastructural and immunocytochemical analyses of cells by transmission and scanning electron microscopy. Less well recognized is its superiority over conventional chemical fixation in preserving labile and rare tissue antigens for immunocytochemistry by light microscopy. In the postgenome era, the focus of molecular genetics will shift from analyzing DNA sequence structure to elucidating the function of gene networks, the intercellular effects of polygenetic diseases, and the conformational rearrangements of proteins in situ. Novel strategies will be needed to integrate knowledge of chemical structures of normal and abnormal macromolecules with the physiology and developmental biology of cells and tissues from whole organisms. This review summarizes the progress and future prospects of freeze-substitution for such explorations.

Ultrasmall immunogold particles: important probes for immunocytochemistry

In this article, we review the immunocytochemical literature with respect to a comparison between conventional colloidal gold and ultrasmall gold particles as immunoprobes. We discuss the relative advantages and disadvantages of each of these types of particles for immunocytochemical applications. We present results from our own laboratories, in which we compared these immunoprobes in selected experimental situations. In addition, we discuss our work on the use of a fluorescently labeled ultrasmall immunoprobe for correlative microscopy.

Freeze-fracture, deep-etch, and freeze-substitution studies of olfactory epithelia, with special emphasis on immunocytochemical variables

Freeze-fracturing and deep-etching are a well-suited set of methods to study membrane and cytoplasmic features. Various approaches are available. Possible variables include tissue preparation, fracturing only or fracturing followed by etching, modes and materials of replication, and various ways of combining freeze-fracturing and/or deep-etching with (immuno)cytochemistry. Freeze-substitution, in particular combined with embedding in methacrylate resins such as the Lowicryls, is becoming rather widely accepted for purposes of ultrastructural (immuno)cytochemistry. Most investigators active in this field agree that this combination yields superior results compared to (immuno)cytochemistry combined with more conventional means of thin section transmission electron microscopy. Yet relatively little information is available on the variations that can occur with different approaches of freeze-substitution immunocytochemistry. This review deals with some of the variations in freeze-fracturing, freeze-etching, and freeze-substitution as applied to olfactory epithelial structures and with the effectiveness of observations obtained by application of the above sets of methods in relating the special morphology of olfactory epithelial cellular structures with those obtained by other approaches. Indeed, the data obtained continue to provide an integral image in which that morphology can be related to the special biochemistry, cell and molecular biology, and electrophysiology of olfactory epithelial structures.

Visualization of silver-enhanced reaction products from protein-and immuno-colloidal gold probes by laser scanning confocal microscopy in reflection mode

We have employed a laser scanning confocal microscope in reflection mode to directly and indirectly visualize sites of deposition of silver-enhanced reaction products from colloidal gold probes. A direct approach was used for the localization of alpha-fetoprotein receptors in human myoblasts by incubating primary cultures with an alpha-fetoprotein-gold conjugate. For an indirect approach, cultured CEM cells, derived from a human T-lymphoma cell line, were incubated with a mouse monoclonal antibody to mature T-cells, followed by a gold-labelled antibody to mouse immunoglobulins. Multiple optical sections of each sample were collected by reflection laser scanning confocal microscopy and combined into three-dimensional renderings. A (non-confocal) transmission image was generated of each field for comparative purposes. The increasing use of reflection laser scanning confocal microscopy combined with colloidal gold conjugates as biological markers will probably be of considerable advantage in cytochemical analysis.

Three-dimensional localization of immunogold markers using two tilted electron microscope recordings

A method is presented to determine the three-dimensional positions of immuno-labeled gold markers from tilted electron micrograph recordings by using image processing techniques. The method consists of three basic modules: localization of the markers in the recordings, estimation of the motion parameters, and matching corresponding markers between the views. Localization consists of a segmentation step based on edge detection and region growing. It also allows for the separation of (visually) aggregated markers. Initial estimates for the motion parameters are obtained from a small number of user-indicated correspondences. A matching algorithm based on simulated annealing is used to find corresponding markers. With the resulting mapping, the motion parameters are updated and used in a new matching step, etc. Once the parameters are stable, the marker depths are retrieved. The developed method has been applied to semithin resin sections of A431 cells labeled for DNA and detected by silver-enhanced ultrasmall gold particles. It represents a reliable method to analyze the three-dimensional distribution of gold markers in electron microscope samples.

Hereditary eosinophil peroxidase deficiency: immunochemical and spectroscopic studies and evidence for a compound heterozygosity of the defect

Hereditary eosinophil peroxidase (EPO; EC 1.11.1.7) deficiency is a rare abnormality of eosinophil granulocytes characterized by decreased or absent peroxidase activity and decreased volume of the granule matrix. The molecular basis of the defect is not known. We report here its molecular characterization in an EPO-deficient subject and his family members. The EPO-deficient eosinophils contained EPO-related material as determined immunochemically using either monoclonal or polyclonal anti-EPO antibodies but had no spectroscopic evidence of EPO. Eosinophil precursors from the EPO-deficient subject contained normally sized EPO mRNA, which was reverse transcribed into the corresponding cDNA clones encompassing the whole gene. Sequencing of these clones disclosed two mutations, a G-->A transition causing a nonconservative replacement of an arginine residue with a histidine and an insertion causing a shift in the reading frame with the appearance of a premature stop codon. The two mutations were located on different chromosomes indicating a compound heterozygosity for the defect. Both the son and the daughter of the proband inherited the G-->A transition, and their eosinophils contained a peroxidase activity intermediate between that of control subjects and the proband, suggesting that the transition is a deficiency-causing mutation. Eosinophil precursors from the EPO-deficient subject were found to actively synthesize an EPO that was apparently normal in terms of cytochemical reaction for peroxidase and immunoreactivity with monoclonal and polyclonal anti-EPO antibodies, but spectroscopically abnormal. The cytochemical reaction for peroxidase tended to decrease or disappear in the eosinophil precursors of the EPO-deficient subject but not of a normal subject as differentiation went on, suggesting that the Arg-->His substitution causes the production of an unstable EPO that undergoes progressive degradation as the cells mature.