Distribution studies tissue imaging techniques

In addition to some early applications in bioanalysis, ambient ionization mass spectrometry has been used as an imaging tool to study drug distribution in tissue sections. Most of the work reported so far involved the use of DESI as the ambient ionization method. Compared to other mass spectrometry-based tissue imaging techniques such as MALDI and SIMS, DESI allows tissue samples to be analyzed under ambient conditions without sample preparation, which simplifies the procedure and prevents the redistribution of analytes during matrix deposition. A major drawback of DESI as an imaging tool is its relatively low spatial resolution (typically 250 pm) and therefore cannot be used for cellular or subcellular imaging. 

Another important characteristic of photoreactive agents is their apparent affinity for certain targets that are of special interest for interventional vascular therapists, As most photosensitizers fluoresce, the kinetics of their distribution in vascular tissue can be investigated both at macroscopic and microscopic levels using fluorescence imaging techniques (Fig, 3), Numerous studies on porphyrin, chlorin, texaphryin, pheophorbide and phthalocyanine photosensitizers in various animal models have documented selective localization in... 

During the past several years, significant progress was made for the MALDI-MS imaging technique. It has been proven to be a valuable tool for studying drug distribution in animal tissues. MALDI-IMS is a simple, quick, and molecularly specific analytical platform that can distinguish small molecules from their metabolites on... 

In a separate study, a protocol for Matrix-assisted laser desorption-ionization (MALDI) imaging mass spectrometry (IMS) has been proposed.18 This IMS technique provides a new approach to visualize spatial distribution of thousands of molecular species, including peptides, proteins, and their metabolites in two- or three-dimensional levels. This approach may also provide a straightforward method of determining the tissue distribution of multiple peptides or proteins in a quantitative manner.18 Chu et al.19 reported a nondestructive molecular extraction method to obtain proteins from a single FFPE or frozen tissue section, without destroying the tissue morphology, such... 

Various techniques, such as intrusion methods, image analysis and weight determinations are used to provide estimates of the porosity and the distribution of pore sizes within a tissue scaffold. This preliminary study of the structural features of particulate-leached PCL scaffolds has shown that reliable measures of porosity can be obtained from simple weighing measurements (Buoyancy method). 

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