? DESCRIPTION (provided by applicant): The objective of this grant application is to research, test and validate a bi-modal diagnostic platform combining optical and ultrasound imaging technologies for real-time, non-destructive in-vitro and in-vivo analysis of composition, structure function and site specific cellular repopulation of extracellular matrix (ECM) scaffolds utilized fr vascular tissue engineering. The proposed approach has the potential to significantly advance the field of vascular tissue engineering and facilitate translation of engineered vascular material to clinical application. The non-destructive nature of the proposed platform enables repeated assessment of ECM scaffold and recellularized construct structure-function relationships both in-vitro and in-vivo. The proposed technology therefore alleviates the need for destructive analysis methods across multiple time points, which are costly, time consuming and frequently impractical. Moreover, the proposed technology will facilitate (a) in-vitro rapid screening of scaffold production methods and non-destructive assessment of batch quality; and (b) non- terminal in-vivo assessment across multiple time points, thereby providing mechanistic insights into engineered vascular tissue regenerative processes. The proposed bi-modal platform will integrate two non-ionizing radiation techniques for label-free tissue analysis: (1) Multispectral Time-Resolved Fluorescence Spectroscopy (TRFS) system for evaluation of ECM composition and biochemical heterogeneities of vascular biomaterials; and (2) High-frequency Ultrasound (US) imaging for evaluation of structural properties and morphology in vascular biomaterials. This is enabled by either Ultrasound Backscatter Microscopy (UBM) for planar scanning or conventional Intravascular Ultrasound (IVUS) for rotational scanning. Four specific aims will be addressed. Aim 1 is focused on developing a set of customized tools (instrumentation and data analysis methods) for in- vitro and in-vivo assessment of vascular scaffolds and constructs. Aim 2 in focused on demonstrating the feasibility of the bi-modal platform as a non-destructive tool for assessment of vascular scaffold properties. Aim 3 is focused on demonstrating the bi-modal platform's ability as a non-destructively tool for in-vitro studying and monitoring of vascular tissue construct formation. Aim 4 is focused on demonstrating the feasibility of the bi-modal technique as a non-destructive tool for monitoring the maturation of vascular constructs in-vivo post- implantation. In summary, the technology proposed for development and validation in this grant application offers a non-destructive solution for the evaluation of many important features (compositional, structural and functional) associated with the maturity and functionality of vascular biomaterials. This is likely to improve our ability to produce engineered vascular tissues in the laboratory for in-vivo implantation which can accelerate the integration time of the implant with the surrounding host tissue, thus restoring the desired quality of life to the patient. Emphasis will be placed on the evaluation of engineered vascular tissue, though, if successful, this non-destructive technique can be applied to assess a variety of engineered tissues.