The application of Cd Se/ZnS quantum dots and confocal laser scanning microscopy for three-dimensional imaging of nanfibrous structures

This paper reports a fast, accurate, and non-destructive three-dimensional imaging approach based on using quantum dots and confocal laser scanning microscopy to get three-dimensional images of internal pore structure of the nanofibrous materials. A practical method of making the fiber fluorescent using quantum dots was applied before three-dimensional imaging by confocal laser scanning microscopy. Fibrous scaffolds with different porosity parameters produced by electrospinning and their three-dimensional pore structure was evaluated by this approach. Furthermore, the introduced approach can be used to measure the pore interconnectivity of the scaffold

Symmetrically tapered <30-micron-thick quasi-planar Ge waveguides as chemical sensors for microanalysis

Symmetrically tapered planar IR waveguides have been fabricated by starting with a ZnS coated concave piece of single-crystal Ge, embedding it in an epoxide resin as a supporting substrate, and then grinding and polishing a planar surface until the thickness at the taper minimum is <30 μm. Such tapering is expected to enhance a waveguide's sensitivity as an evanescent wave sensor by maximizing the amount of evanescent wave energy present at the thinnest part of the waveguide. As predicted by theory, the surface sensitivity, i.e., the absorbance signal per molecule in contact with the sensing region, increases with decreasing thickness of the tapered region even while the total energy throughput decreases. The signal-to-noise ratio obtained depends very strongly on the quality of the polished surfaces of the waveguides. The surface sensitivity is superior to that obtained with a commercial Ge attenuated total reflection (ATR) accessory for several types of sample, including thin films (<10 ng) and small volumes (<1 μL) of volatile solvents. By using the waveguides, light-induced structural changes in the protein bacteriorhodopsin were observable using samples as small as ∼50 pmol (∼1 μg). In addition, the waveguide sensors can reveal the surface compositions on a single human hair, pointing to their promise as a tool for forensic fiber analysis.

Biofunctionalization of 3D nylon 6,6 scaffolds using a two-step surface modification

Nylon is a relatively inert polymer. The ability to easily functionalize nylon with biomolecules will improve the utilization of nylon in biological systems. A potential use of the biofunctionalized nylon scaffolds is in devices for cell therapeutics that can specifically select cells present in small numbers, such as hematopoietic stem cells. This study developed a versatile and simple two-step technique combining oxygen plasma treatment with wet silanization to graft biomolecules onto nylon 6,6 3D porous scaffolds. Scaffolds that were exposed to oxygen plasma exhibited up to 13-fold increase in silane attachment ((3-mercaptopropyl)trimethoxysilane/(3-aminopropyl)trimethoxysilane) compared to untreated scaffolds. To address the limitation of nondestructive characterization of the surface chemistry of 3D scaffolds, fluorescent CdSe/ZnS nanoparticles were used as a reporting tool for -NH(2) functionalized surfaces. Scaffolds that were covalently bound with neutravidin protein remained stable in phosphate buffered saline up to four months. Functionality of the neutravidin-grafted scaffolds was demonstrated by the specific binding of CD4 cells to the scaffold via CD4-specific antibody. Ultimately, these neutravidin-functionalized 3D nylon scaffolds could be easily customized on demand utilizing a plethora of biotinylated biomolecules (antibodies, enzymes and proteins) to select for specific cell of interest. This technique can be extended to other applications, including the enhancement of cell-scaffold interactions.