(B) Quantification of photoacoustic signals from your images represented as the normalized photoacoustic signal intensity per mm3. (0.01 and 0.018 mm3) showing a complete response with no recurrence when treated with 100 J/cm2. Together our results demonstrate the complementary imaging and treatment capacity of DFAC. This potentially enables fluorescence imaging to assess the presence of tumor on a macroscopic scale, followed by photoacoustic imaging for delineating tumor margins guiding surgical resection and removal of any residual microscopic disease by PIT, in a single intraoperative setting. == Introduction == Antibody-based targeted diagnostic and therapeutic agents have been demonstrated for their utility in the treatment of several malignant disorders including head and neck cancers.13Antibody-based targeted photoactive agents are currently being employed in head and neck cancers for tumor margin assessment during surgical resection and photoimmunotherapy (PIT) (NCT02422979,NCT03769506).47Attaining disease-free surgical margins while minimizing resection of healthy tissue is a major challenge in tumor resection surgeries for head and neck cancers. Precise identification of tumor margins is usually important in minimizing healthy tissue loss and preserving vital structures, function, and aesthetics to improve patient compliance. As recurrence rates in head and neck cancers decrease with every extra millimeter of healthy tissue resected,8it is important to assess these molecular-targeted probes for their ability in accurately delineating tumor margins and treating tumors of microscopic sizes. In this context, while fluorescence imaging provides a macroscopic overview to identify the extent of tumor invasion and lymph node metastasis, complementing it with photoacoustic imaging, as proposed in the present study using DFAC, can help in delineation of tumor margins in three sizes. Recent improvements in tumor-targeted imaging have seen several antibody fluorophore conjugates being tested in clinical trials for guiding resection surgeries.9,10In this context, the use of photosensitizers provides an advantage where the photoactive molecule can be utilized for fluorescence imaging and treatment PF-AKT400 of the target lesions through photodynamic therapy. This has been shown in several studies from our lab as well as others.2,1114Although photoimmunotherapy (PIT) was developed three decades ago,15it has recently gained popularity with clinical approval in Japan for head and neck cancers. Ongoing phase III clinical trials are evaluating the efficacy of PIT for head and neck cancers in PF-AKT400 USA.46,16The efficacy of photodynamic therapy (PDT), however, largely depends on the tumor size and oxygenation. PDT of larger or hypoxic tumors results in worse therapeutic outcomes, whereas smaller or more oxygenated tumors respond better.1719 We have previously reported the synthesis and characterization of a dual-function antibody conjugate (DFAC) for multimodal imaging (photoacoustic and fluorescence imaging) and PIT of EGFR-overexpressing tumor cells.1,20While fluorescence imaging provides sensitivity, the tumor depth profiling provided by fluorescence imaging is low (up to a few millimeters), a deficiency adequately complemented by photoacoustic imaging, where the depth profiling can reach up to a few centimeters.21,22The ability to irradiate the tumor bed post surgery carries the potential of eliminating microscopic disease, thus minimizing recurrence. In this study, we evaluate the performance of the DFAC developed using cetuximab (an EGFR-targeted antibody) conjugated to benzoporphyrin derivative (BPD) for PF-AKT400 fluorescence imaging and PIT and a Si-centered naphthalocyanine (SiNC(OH))23dye for photoacoustic imaging in microscopic head and neck malignancy spheroids, in vitro. We also propose a framework for executing multimodal imaging, followed by PIT for precise delineation of tumor margins and removal of residual disease. == Results == == Synthesis and Characterization of Dual-Function Antibody Conjugates == The dual-function antibody conjugate (DFAC) synthesis was Rabbit Polyclonal to TBC1D3 carried out in 40% DMSO as explained previously.1While 40% DMSO may affect the structure and function of most proteins, previous studies from our lab have established this to be an optimal concentration to maintain antibody.