BODIPY dyes tends to be highly fluorescent, but their emissions can be attenuated by adding substituents with appropriate oxidation potentials. Substituents like these have electrons to feed into photoexcited BODIPYs, quenching their fluorescence, thereby generating relatively long-lived triplet states. Singlet oxygen is formed when these triplet states interact with 3O2. In tissues, this causes cell damage in regions that are illuminated, and this is the basis of photodynamic therapy (PDT). The PDT agents that are currently approved for clinical use do not feature BODIPYs, but there are many reasons to believe that this situation will change. This review summarizes the attributes of BODIPY dyes for PDT, and in some related areas.

Achieving effective treatment of deep-seated tumors is a major challenge for traditional photodynamic therapy (PDT) due to difficulties in delivering light into the sub-surface. Thanks to its great tissue penetration, X-rays hold the potential to become an ideal excitation source for activating photosensitizers (PS) that accumulate in deep tumor tissue. Recently, a wide variety of nanoparticles have been developed for this purpose. The nanoparticles are not only designed as carriers for loading various kinds of PSs, but also can facilitate the activation process by transferring energy harvested from X-ray irradiation to the loaded PS. In this review, we focus on recent developments of nanoscintillators with high energy transfer efficiency, their rational designs, as well as potential applications in next generation PDT. Treatment of deep-seated tumors by using radioisotopes as an internal light source will also be discussed.

Animal models, particularly rodents, are major translational models for evaluating novel anticancer therapeutics. In this review, different types of nanostructure-based photosensitizers that have advanced into the in vivo evaluation stage for the photodynamic therapy (PDT) of cancer are described. This article focuses on the in vivo efficacies of the nanostructures as delivery agents and as energy transducers for photosensitizers in animal models. These materials are useful in overcoming solubility issues, lack of tumor specificity, and access to tumors deep in healthy tissue. At the end of this article, the opportunities made possible by these multiplexed nanostructure-based systems are summarized, as well as the considerable challenges associated with obtaining regulatory approval for such materials. The following questions are also addressed: (1) Is there a pressing demand for more nanoparticle materials? (2) What is the prognosis for regulatory approval of nanoparticles to be used in the clinic?

Traditional photodynamic therapy (PDT) requires external light to activate photosensitizers for therapeutic purposes. However, the limited tissue penetration of light is still a major challenge for this method. To overcome this limitation, we report an optimized system that uses Cerenkov radiation for PDT by using radionuclides to activate a well-known photosensitizer (Chlorin e6, Ce6). By taking advantage of hollow mesoporous silica nanoparticles (HMSNs) that can intrinsically radiolabel oxophilic zirconium-89 (89Zr, t1/2 = 78.4 h) radionuclide, as well as possess great drug loading capacity, Ce6 can be activated by Cerenkov radiation from 89Zr in the same nanoconstruct. In vitro cells viability experiments demonstrated dose-dependent cell deconstructions as a function of concentration of Ce6 and 89Zr. In vivo studies show inhibition of tumor growth when mice were subcutaneously injected with [89Zr]HMSN-Ce6 and histological analysis of tumor section showed damage to tumor tissues, implying that reactive oxygen species mediated the destruction. This study offers a way to use internal radiation source to achieve deep-seated tumor therapy without using any external light source for future applications.

BODIPYs are photosensitizers activatable by light to generate highly reactive singlet oxygen (O) from molecular oxygen, leading to tissue damage in the photoirradiated region. Despite their extraordinary photophysical characteristics, they are not featured in clinical photodynamic therapy. This review discusses the recent advances in the design and/or modifications of BODIPYs since 2013, to improve their potential in photodynamic cancer therapy and related areas.