Diffuse optics determination of hemoglobin derivatives in red blood cells and liposome encapsulated hemoglobin

Fluorescence absorbance inner-filter decomposition: the role of emission shape on estimates of free Ca(2+) using Rhod-2

A method for decomposing complex emission spectra by correcting for known inner-filter effects is described. This approach builds on previous work using a linear combination of model emission spectra and combines the known absorption characteristics of the system to fit the composite emission spectrum. Rhod-2, which has a small Stokes shift and significant self-absorption, was used as the model system. By adding the absorption characteristics of Rhod-2 to the model, the degree of fit was significantly improved, thus minimizing residuals, and accurately predicted the spectral shape changes with increasing concentration, [Rhod-2]. More complex studies were conducted with Rhod-2 in isolated cardiac mitochondria with multiple emission and absorption elements. By including known absorbances to the spectral decomposition, the overall precision increased almost four fold. Moreover, this approach eliminated the significant [Rhod-2] dependence on the apparent K(50) and therefore improved the accuracy of free [Ca(2+)] calculations. These data demonstrate that secondary inner-filter correction can significantly improve spectral decomposition of complex emission spectra, which are used in a variety of biological applications.

Effects of Photofrin on in vivo skin reflectivity

Skin reflection spectra were measured before and 24 h after administration of Photofrin to nevoid basal-cell carcinoma syndrome patients. The presence of the drug reduced the reflectivity of uninvolved skin and increased the reflectivity of erythematous basal cell cancers. Data analysis with diffusion approximation and Monte Carlo simulation were employed to estimate the optical constant changes and localized drug concentration.