Three-dimensional reconstruction of cell nuclei, internalized quantum dots and sites of lipid peroxidation

We present new approaches to the 3-D reconstruction of organelle morphology and biochemical changes in confocal live-cell images. We demonstrate the 3-D shapes of nuclei, the 3-D intracellular distributions of QDs and the accompanying lipid-membrane peroxidation, and provide methods for quantification.This study provides an approach to 3-D organelle and nanoparticle visualization in the context of cell death; however, this approach is also applicable more generally to investigating changes in organelle morphology in response to therapeutic interventions, stressful stimuli and internalized nanoparticles. Moreover, the approach provides quantitative data for such changes, which will help us to better integrate compartmentalization of subcellular events and to link morphological and biochemical changes with physiological outcomes.Quantum dots (QDs) are increasingly being used as a complement to molecular dyes in bio-imaging applications. Compared with these dyes, QDs have two special properties: size-dependent luminescence, and broad excitation but relatively narrow emission spectra [1-3]. Different synthesis procedures and various capping and conjugation methods provide a wide array of QDs with different chemical and biological properties, including their stability in biological environments. QD stability is essential both for the quality of the imaging signal and for compatibility in live cells. Several groups have succeeded in conjugating or capping various biologically interesting ligands with QDs and have demonstrated their usefulness for different biological applications [4-14].Despite enormous advances in biophysical, chemical and biological investigations, compatibility of QDs with live cells remains unresolved, and research in this area is still in its infancy [15-20].QDs, like other stimuli that cause cell death, induce both subtle and robust morphological changes in several organelles, including the nucleus [21]. A type of cell death has been ascribed to the