Despite recent advances in the chemotherapy of leukemia and other hematologic malignancies, a large proportion of patients remain incurable. Autologous stem cell transplantation (ASCT) is potentially curative treatment strategy, which is limited by the risk of re-infusion of residual tumor cells in the graft. While numerous purging methods have been developed, no existing method removes 100% of the tumor cells from the transplant. A major problem of ASCT is that there is residual disease in more than 90% of transplanted grafts, which causes recurrence after clinically successful treatment. Our newly established collaboration is aimed at developing the Laser Assisted NanoThermolysis Cell Elimination Technique (LANTCET) for purging of leukemia cells from autologous bone marrow or apheresis grafts. Our

central hypothesis is that selective loading of the target (leukemia) cells with antibody-conjugated gold or silver nanorods (NR) followed by extra-corporal irradiation of stem cell graft with laser pulses at the wavelength of 1064 nm will enable efficient ex vivo purging of tumor cells from a mixture with normal cells. Gold and silver NRs possess very strong optical absorption tunable in the near-infrared spectral range (650 nm to 1100 nm) by changing their aspect ratio (of length to diameter). Our preliminary data show that gold and silver nanorods absorb 1000 times stronger than organic dyes of equal concentration, and 10 to 100 times stronger than gold nanoshells of equal volume. NR can be targeted specifically to leukemic cells using monoclonal antibodies (MAB). The cells loaded with gold or silver NR can be detected using photothermal microscopy and destroyed by laser-generated microbubbles (LMB) of vapor that emerge around the optically absorbing gold or silver NRs. The speed of laser scanning allows rapid processing of the entire graft (100 cc -200 cc). Various strategies may be employed to produce clusters of nanorods in leukemic cells, which results in 100 fold reduction of the laser damage threshold for tumor cells. Due to the very strong optical absorption by NR and total transparency of cellular components in the nearinfrared, the NRs may generate LMBs and thus damage the tumor cells at a laser fluence that is safe for cells without NR. While gold NRs are less toxic to normal cells compared to silver NRs, the latter have an order of magnitude stronger absorbance, making them better candidates for the laser damage of tumor cells. At the end of the proposed project an optimal nanoparticle will be chosen for future research. The nanotechnology of fabricating gold and silver nanorods has only recently become developed by Fairway Medical Technologies (FMT) that intends to advance it further for the clinical use. Our multidisciplinary team composed of a hematologist with substantial experience in leukemia research, an engineer and a physicist proposes to develop a new technology for image-guided elimination of residual leukemic cells in the bone marrow graft for ASCT. A leukemia expert from MDACC will lead the project and perform all control experiments, testing and evaluation using leukemia cells and normal stem from the cell bank. FMT will provide the major components for the experimental setup. Rice University will perform the laser irradiation of cells guided by the photothermal detection system. The proposed combination of nanotechnology, highly specific immunologic methods with spectrally selective laser irradiation guided by photothermal detection enables the high specificity and safety of the graft treatment. Combination of LANCET with ASCT avoids the need for delivery of high power laser pulses deep into tissue and thereby is particularly appropriate for the purging of autologous grafts. LANCET may provide higher efficacy and safety by purging the graft tissues of tumor cells and thus fulfill a longstanding need for leukemia patients.