Selective photoreactions in a programmable array microscope (PAM): Photoinitiated polymerization, photodecaging, and photochromic conversion

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Abstract
Background: Innovative thinking and experimentation were the hallmarks of Mack Fulwyler's approach to research. This report summarizes some of the ideas and their early realizations that he pursued in the field of imaging cytometry, work that was not published before his untimely death, although he composed the initial draft of this report.Methods: Included are related experiments implemented in the programmable array microscope (PAM) devised for patterned illumination and detection, the instrument that Mack Fulwyler employed during a sabbatical leave in Göttingen in 1998. Despite being the originator of instrumentation for flow cytometry and sorting, Mack Fulwyler was intensely interested in imaging systems, recognizing their ability to resolve cellular details obscured by the whole cell signals generally acquired in flow. At one point, these interests merged with those of two other authors (I.T.Y. and T.M.J.), leading to the Image Cytometry and Sorting (ICAS) strategy and project. A major goal was uncomplicated rare cell detection and isolation using a sequential process of cellular labeling via suitable probes, whole field imaging, and selective area‐restricted photoinduced reactions designed to encapsulate and/or chemically or physically tag cells in a manner permitting subsequent fractionation by bulk techniques.Results and Conclusion: This publication features photoinduced polymerization, photodecaging, photoactivation, and photochromic conversion reactions carried out by Fulwyler and/or the other authors with the PAM, employing operator designated patterns and locations in various samples. Photopolymerization of polyethylene glycol‐diacrylate to a gel‐like structure allowing the specific selection of objects (cells) for further analysis and processing techniques was the approach explored personally by Mack Fulwyler in relation to the ICAS concept. © 2005 International Society for Analytical Cytology