Non-Oncologic Applications of Nanomedicine-Based Phototherapy

Abstract

Phototherapy is widely applied to various human diseases. Nanomedicine-based phototherapy can be classified into photodynamic therapy (PDT) and photothermal therapy (PTT). Activated photosensitizer kills the target cells by generating radicals or reactive oxygen species in PDT while generating heat in PTT. Both PDT and PTT have been employed for treating various diseases, from preclinical to randomized controlled clinical trials. However, there are still hurdles to overcome before entering clinical practice. This review provides an overview of nanomedicine-based phototherapy, especially in non-oncologic diseases. Multiple clinical trials were undertaken to prove the therapeutic efficacy of PDT in dermatologic, ophthalmologic, cardiovascular, and dental diseases. Preclinical studies showed the feasibility of PDT in neurologic, gastrointestinal, respiratory, and musculoskeletal diseases. A few clinical studies of PTT were tried in atherosclerosis and dry eye syndrome. Although most studies have shown promising results, there have been limitations in specificity, targeting efficiency, and tissue penetration using phototherapy. Recently, nanomaterials have shown promising results to overcome these limitations. With advanced technology, nanomedicine-based phototherapy holds great potential for broader clinical practice.

Keywords: non-oncologic applications; photodynamic therapy; photosensitizers; phototherapy; photothermal therapy.

Figure 1

Mechanism of action on target lesion in photodynamic therapy (PDT). There are two types of reaction during PDT. Following absorption of light, a photosensitizer is transformed from the ground state into an excited state. The activated sensitizer generates radicals (type-I reaction) or oxidative substrates (type-II reaction) to damage the cell. Modified from Refs. [29,30,31].

Figure 2

Mechanism of action on non-oncologic diseases in PTT. A lesion containing PTT agents is irradiated with a light source. The radiation absorbed by photothermal agents is converted to heat energy, causing cell death. Modified from Ref. [54].

Figure 3

Non-oncological application of PDT. Various human diseases other than cancer that can be treated with PDTs are categorized based on different organ systems. The gray box describes the process of PDT including a light source with an appropriate wavelength, photosensitizers which can be applied topically (as in the figure) or accumulated to the target region via intravenous injection, and the irradiated target region where the phototoxicity is produced by the photoactivation of photosensitizers.

Figure 4

Promising strategies of novel nanomaterials for effective non-oncologic phototherapy.