In order to pack a two-meter-long DNA molecule that contains the genetic code of an organism into a several-micron sized nucleus, the molecule compacts into a dense structure called chromatin. Some parts of chromatin display a more open form called euchromatin, which is characteristic of high gene expression, while others exhibit a more densely packed chromatin called heterochromatin. Currently, there is no biosensing technology capable of sensing the conversion from heterochromatin to euchromatin and back in real time, which is a critically important question for understanding how cells function and how the human genome is regulated. Thus, the goal of this project is to develop a method for dynamic biosensing of chromatin packing in live cells and to achieve this without employing external markers that can affect cell function and, as a result, chromatin dynamics. This will be achieved by using properties of scattered light, which carries information about the object it is scattered by, even if the structure of the object is so tiny that regular microscopes cannot resolve it. An important part of this project will be an educational outreach program to share the technology with underrepresented groups and K-12 students. This outreach program is designed to reach K-12 educationally disadvantaged students from local neighborhoods with predominantly ethnic-minority student populations.<br/><br/>The novel label-free technology for dynamic biosensing of chromatin packing in live cells, proposed in this application will address fundamental unsolved problems in genetics and epigenetics. It should help to answer a poorly understood question of how signal transduction pathways directly communicate with chromatin to change the epigenetic landscape. It can also facilitate a novel synthetic biology biosensing approach as chromatin can serve as a sensor of metabolic changes during early development. It should also have important implications in public health, including chromatin changes in cancer or the role of epigenetics in infectious diseases. The approach will advance both engineering and life sciences and will be based on a combination of the principles of fractal sensing, since it is known that chromatin in live cells is organized as a fractal with heterochromatin and euchromatin domains exhibiting different fractal dimensions, and coherent confocal light absorption and scattering spectroscopic microscopy. The proposed approach is motivated by the new fundamental insights that self-similar properties of the chromatin fractal are reflected in the chromatin light scattering spectra, and these spectra can be continuously and rapidly recorded creating a 3D dynamic map of chromatin on a multitude of spatial and temporal scales.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.