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The concept of refractive-index matching to enhance the optical penetration depth of whole blood is discussed on the basis of in vitro studies that used the technique of near-infrared optical coherence tomography. It was found that optical clearing of blood is defined not only by refractive-index matching but also by changes in the size of red blood cells and in their aggregation ability when chemicals are added. For example, in whole blood diluted to twice its volume by saline with the addition of 6.5% glycerol, the total attenuation coefficient was reduced from 4.2 to 2.0 mm(-1), and the optical penetration at 820 nm was correspondingly increased to 117%. For the other agents tested (glucose, dextrans, propylene glycol, and trazograph) the enhancement of penetration was 20-150.5%. In the blood sedimentation study, regular or irregular oscillations or jumps of the red-blood cell-plasma boundary were observed. The 1-min time period of regular oscillations correlated well with the kinetics of the aggregation process as described by the two subsequent stages of formation of linear and three-dimensional aggregates. The results also showed that optical clearing of blood by osmotic agents is potentially useful not only in blood sedimentation and aggregation studies but also in intravascular optical coherence tomography imaging techniques.

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Highly ordered mesoporous silica materials are hydrothermally synthesized at high temperature by using fluorocarbon–hydrocarbon surfactant mixtures as templates. Because of the high temperature of the synthesis, the obtained materials show complete silica condensation, which give rise to ultra‐stabile structures. JLU‐20 for example (see TEM image of calcined JLU‐20) has a fully condensed mesopore wall with a very high Q4/Q3 ratio of 6.5.

The purpose of the present study is to investigate systematically the mechanisms of alterations in the optical properties of whole blood immersed in the biocompatible agent dextran, and to define the optimal concentration of dextrans required for blood optical clearing in order to enhance the capability of light penetration depth for optical imaging applications. In the experiments, dextrans with different molecular weights and various concentrations were employed and investigated by the use of the optical coherence tomography technique. Changes in light attenuation, refractive index and aggregation properties of blood immersed in dextrans were studied. It was concluded from the results that the mechanisms for blood optical clearing are characteristic of the types of dextrans employed, their concentrations and the application stages. Among the substances applied, Dx500 at a concentration at 0.5 g dl(-1) gives the best result in improving light penetration depth through the blood. The increase of light transmission at the beginning of the addition of dextrans is mainly attributed to refractive index matching between the scattering centres and the ground matter. Thereafter, the transmission change is probably due to a dextran-induced aggregation-disaggregation effect. Overall, light scattering in the blood could be effectively reduced by the application of dextrans. It represents a promising approach to increasing the imaging depth for in vivo optical imaging of biological tissue, for example optical coherence tomography.

In an effort to find an effective concentration that could minimize the side effect for clinical applications, and to understand the potential synergistic effect of hyperosmotic agents on optical clearing of gastric tissues, porcine stomach tissues (pyloric mucosa) applied with a mixed solution of glycerol and dimethyl sulfoxide (DMSO) are investigated with near infrared reflectance spectroscopy. Five chemical solutions, containing 80% glycerol, 50% DMSO, 50% glycerol with 10% DMSO, 20% DMSO and 30% DMSO, respectively, are prepared and studied; all of which show significant improvement in light transmittance, and thus reduction of the light scattering of tissue. It is found that, among the solutions investigated, 50% glycerol with 30% DMSO achieves the best clearing effect on the improvement of light penetration. Light transmittance is increased approximately 29% and diffuse reflectance decreased approximately 31% at 30 min after the topical application of 50% glycerol with 30% DMSO. This solution shows significantly stronger effect than 80% glycerol on optical clearing even though they have the same osmolarity. 80% glycerol leads to 23% increase of light transmittance and 24% decrease of diffuse reflectance. The mixed solution of 50% glycerol and 20% DMSO has less osmolarity than the solution of 80% glycerol, but they achieve a similar degree of optical clearing. In other words, the clearing effect of glycerol is enhanced by adding DMSO into it. It is suggested that membrane penetration and carrier effect of DMSO probably accounts for this synergistic effect.

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The solution configuration of labile coordination complexes may be difficult to determine, even in cases in which the solid state structure is known. We have previously synthesized a series of chiral ligands which form pseudo-C 3 -symmetric complexes with Zn II and Cu II salts that possess an available electrophilic coordination site. Molecular modeling of Zn II complexes of the chiral ligand N,N-bis[(2-quinolyl)methyl]-1-(2-pyridyl)ethanamine (␣-MeBQPA) showed that the spatial arrangement of the heterocyclic arms is controlled by a substituent on one methylene arm, resulting in the adoption of an enantiomeric conformation displaying a propeller-like asymmetry. In this paper we report the application of the exciton chirality method to the determination of the conformation of asymmetric metal-ligand complexes in solution. There is a good correlation between the predicted and the observed Cotton effects, demonstrating that the geometry in solution closely resembles that predicted by computational simulations and those obtained by X-ray crystallographic studies of metal complexes with racemic and enantiomerically pure ligands. The X-ray crystallographic structure of the first optically pure complex in this series is reported. Chirality 9: 616-622, 1997.