Natural-product-based, carrier-free, noncovalent nanoparticles for tumor chemo-photodynamic combination therapy

Cancer, with its diversity, heterogeneity, and complexity, is a significant contributor to global morbidity, disability, and mortality, highlighting the necessity for transformative treatment approaches. Photodynamic therapy (PDT) has aroused continuous interest as a viable alternative to conventional cancer treatments that encounter drug resistance. Nanotechnology has brought new advances in medicine and has shown great potential in drug delivery and cancer treatment. For precise and efficient therapeutic utilization of such a tumor therapeutic approach with high spatiotemporal selectivity and minimal invasiveness, the carrier-free noncovalent nanoparticles (NPs) based on chemo-photodynamic combination therapy is essential. Utilizing natural products as the foundation for nanodrug development offers unparalleled advantages, including exceptional pharmacological activity, easy functionalization/modification, and well biocompatibility. The natural-product-based, carrier-free, noncovalent NPs revealed excellent synergistic anticancer activity in comparison with free photosensitizers and free bioactive natural products, representing an alternative and favorable combination therapeutic avenue to improve therapeutic efficacy. Herein, a comprehensive summary of current strategies and representative application examples of carrier-free noncovalent NPs in the past decade based on natural products (such as paclitaxel, 10-hydroxycamptothecin, doxorubicin, etoposide, combretastatin A4, epigallocatechin gallate, and curcumin) for tumor chemo-photodynamic combination therapy. We highlight the insightful design and synthesis of the smart carrier-free NPs that aim to enhance PDT efficacy. Meanwhile, we discuss the future challenges and potential opportunities associated with these NPs to provide new enlightenment, spur innovative ideas, and facilitate PDT-mediated clinical transformation.

A multifunctional nanoplatform based on graphitic carbon nitride quantum dots for imaging-guided and tumor-targeted chemo-photodynamic combination therapy

Graphitic carbon nitride quantum dots (g-CNQDs) have shown great potential in imaging, drug delivery and photodynamic therapy (PDT). However, relevant research on g-CNQDs for PDT or drug delivery has been conducted separately. Herein, we develop a g-CNQDs-based nanoplatform (g-CPFD) to achieve simultaneously imaging and chemo-photodynamic combination therapy in one system. A g-CNQDs-based nanocarrier (g-CPF) is first prepared by successively introducing carboxyamino-terminated oligomeric polyethylene glycol and folic acid onto the surface of g-CNQDs via two-step amidation. The resultant g-CPF possesses good physiological stability, strong blue fluorescence, desirable biocompatibility, and visible light-stimulated reactive oxygen species generating ability. Further non-covalently loaded doxorubicin enables the system with chemotherapy function. Compared with free doxorubicin, g-CPFD expresses more efficient chemotherapy to HeLa cells due to improved folate receptor-mediated cellular uptake and intracellular pH-triggered drug release. Furthermore, g-CPFD under visible light irradiation shows enhanced inhibition on the growth of cancer cells compared to sole chemotherapy or PDT. Thus, g-CPFD exhibits exceptional anti-tumor efficiency due to folate receptor-mediated targeting ability, intracellular pH-triggered drug release and a combined treatment effect arising from PDT and chemotherapy. Moreover, this nanoplatform benefits imaging-guided drug delivery because of inherent fluorescent properties of doxorubicin and g-CPF, hence achieving the goal of imaging-guided chemo-photodynamic combination treatments.