A new type of carbon dots (CD-Asp) with targeting function toward brain cancer glioma was synthesized via a straightforward pyrolysis route by using D-glucose and L-aspartic acid as starting materials. The as-prepared CD-Asp exhibits not only excellent biocompatibility and tunable full-color emission, but also significant capability of targeting C6 glioma cells without the aid of any extra targeting molecules. In vivo fluorescence images showed high-contrast biodistribution of CD-Asp 15 min after tail vein injection. A much stronger fluorescent signal was detected in the glioma site than that in normal brain, indicating their ability to freely penetrate the blood-brain barrier and precisely targeting glioma tissue. However, its counterparts, the CDs synthesized from D-glucose (CD-G), L-asparic acid (CD-A), or D-glucose and L-glutamic acid (CD-Glu) have no or low selectivity for glioma. Therefore, CD-Asp could act as a fluorescence imaging and targeting agent for noninvasive glioma diagnosis. This work highlights the potential application of CDs for constructing an intelligent nanomedicine with integration of diagnostic, targeting, and therapeutic functions.

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The treatment of brain tumors remains a challenge due to the limited accumulation of drugs and nanoparticles. Here, we triggered the aggregation of gold nanoparticles (AuNPs) using legumain to enhance the retention of chemotherapeutics in brain tumors. This nanoplatform, AuNPs-A&C, is comprised of Ala-Ala-Asn-Cys-Lys modified AuNPs (AuNPs-AK) and 2-cyano-6-aminobenzothiazole modified AuNPs (AuNPs-CABT). AuNPs-AK could be hydrolyzed to expose the 1,2-thiolamino groups on AuNPs-AK in the presence of legumain, which occurs by a click cycloaddition with the contiguous cyano group on AuNPs-CABT, resulting in formation of AuNPs aggregates. This strategy led to an enhanced retention of the AuNPs in glioma cells both in vitro and in vivo due to the blocking of nanoparticle exocytosis and minimizing nanoparticle backflow to the bloodstream. After conjugation of doxorubicin (DOX) via a pH-sensitive linker to AuNPs-A&C, the efficiency for treating glioma was improved. The median survival time for the DOX-linked AuNPs-A&C increased to 288% in comparison to the saline group. We further show the use of the AuNPs-A&C for optical imaging applications. In conclusion, we provide a strategy to increase nanoparticle tumor accumulation with the potential to improve therapeutic outcome.

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