Multimodal Applications of Zinc Gallate-Based Persistent Luminescent Nanoparticles in Cancer Treatment: Tumor Margining, Diagnosis, and Boron Neutron Capture Therapy.

On the basis of the boron neutron capture therapy (BNCT) modality, we have designed and synthesized a zinc gallate (ZnGa 2 O 4 )-based nanoformulation for developing an innovative theranostic approach for cancer treatment. Initially, the (ZnGa 1.995 Cr 0.005 O 4 or ZnGa 2 O 4 :(0.5%)Cr persistent luminescence nanoparticles (PLNPs) embedded on silica matrix were synthesized. Their surface functionalization was performed using organic synthesis strategies to attach the amine functional moieties which were further coupled with poly(vicinal diol). These diols were helpful for conjugation with 10 B(OH) 3 , which subsequently served to couple with an in-house-synthesized variant of pH-(low)-insertion peptide (pHLIP) finally giving a tumor-targeting nanoformulation. Most importantly, the polymeric diols helped in conjugation of a substantial number of 10 B to provide the therapeutic dose required for effective BNCT. This nanoformulation internalized substantially (∼80%) to WEHI-164 cancer cells within 6 h. Tumor homing studies indicated that the accumulation of this formulation at the acidic tumor site was within 2 h. The in vitro evaluation of the formulation against WEHI-164 cancer cells followed by neutron irradiation revealed its potent cytotoxicity with IC 50 ∼ 25 μM. In the case of studies on animal models, the melanoma-induced C57BL/6 and fibrosarcoma-induced BALB/c mice were treated with formulations through intratumoral and intravenous injections, respectively, followed by neutron irradiation, leading to a significant killing of the cancer cells, which was evidenced by a reduction in tumor volume (75-80%) as compared with a control tumor. Furthermore, the histopathological studies confirmed a damaging effect only on tumor cells, while there was no sign of damage to the vital organs in treated mice as well as in controls.