Nanoprobes visualizing gliomas by crossing the blood brain tumor barrier

The difficulty in delineating the glioma margins in brain is a major obstacle for its completed resection, which leads to the disproportionately high recurrence and mortality. Besides the fast exertion rate, inadequate sensitivity and non-targeting specificity, the main reason leading to failure of small molecular probes to define gliomas is their incapability to efficiently cross the blood brain tumor barrier (BBTB). Nanoprobes (NPs) show promise to precisely delineate the geographically irregular tumor margins due to their tunable size/circulation lifetime that maximize their passive intratumoral accumulation and their convenience for surface modification that increases the BBTB transcytosis efficacy, imaging sensitivity and receptor targeting specificity. In this work, the characteristics of the BBTB are addressed from biological and physiological perspectives, strategies are presented to deliver NPs across the BBTB, recent developments of NPs are reviewed for glioma visualization and finally the difficulty and promise for clinical translation of NPs are described. Overall, NPs hold great potential for glioma imaging and treatment by pre-surgically delineating tumor margins and intra-operatively guiding tumor excision.