Background Brain tumors are inherently difficult to access due to the cellular blood-brain barrier (BBB) and blood-tumor barrier (BTB) that limit the delivery of contrast and therapeutic agents to tumor tissues from the systemic circulation[1,2].Near-infrared (NIR) heptamethine cyanine fluorescence dyes have emerged as promising tools for noninvasive cancer imaging [3, 4]o These NIR agents show preferential uptake in tumor cells but not normal cells as demonstrated in a variety of cancer cell lines, tumor xenografts, spontaneous mouse tumors in transgenic animals and human tumor samples [5, 6].