Activatable Graphene Quantum-Dot-Based Nanotransformers for Long-Period Tumor Imaging and Repeated Photodynamic Therapy

Photodynamic therapy (PDT) is considered as an emerging therapeutic modality against cancer with high spatiotemporal selectivity because the utilized photosensitizers (PSs) are only active and toxic upon light irradiation. To maximize its effectiveness, PDT is usually applied repetitively for ablating various tumors. However, the total overdose of PSs from repeated administrations causes severe side effects. Herein, acidity-activated graphene quantum dots-based nanotransformers (GQD NT) are developed as PS vehicles for long-period tumor imaging and repeated PDT. Under the guidance of Arg-Gly-Asp peptide, GQD NT targets to tumor tissues actively, and then loosens and enlarges in tumor acidity, thus promising long tumor retention. Afterwards, GQD NT transforms into small pieces for better penetration in tumor. Upon laser irradiation, GQD NT generates mild hyperthermia that enhances cell membrane permeability and further promotes the PSs uptake. Most intriguingly, the as-prepared GQD NT not only turns-on fluorescence/magnetic resonance signals, but also achieves efficient repeated PDT. Notably, the total PSs dose is reduced to 3.5 mu mol kg(-1), which is 10-30 times lower than that of other reported works. Overall, this study exploits a smart vehicle to enhance accumulation, retention, and release of PSs in tumors through programmed deformation, thus overcoming the overdose obstacle in repeated PDT.

Automated summary

In this study, acidity-activated graphene quantum dots-based nanotransformers (GQD NT) were developed as photosensitizer vehicles for long-period tumor imaging and repeated PDT. The GQD NT actively targeted tumor tissues and underwent loosening and enlargement in tumor acidity, enabling longer tumor retention. The GQD NT also generated mild hyperthermia upon laser irradiation, enhancing cell membrane permeability and promoting photosensitizer uptake. This study overcame the overdose obstacle in repeated PDT by using programmed deformation to enhance accumulation, retention, and release of photosensitizers in tumors.