Abstract
The cancer incidence world-wide has caused an increase in the demand for effective forms of treatment. One unconventional form of treatment for cancer is photodynamic therapy (PDT). PDT has 3 fundamental factors, namely a photosensitiser (PS) drug, light and oxygen. When a PS drug is administered to a patient, it can either passively or actively accumulate within a tumour site and once exposed to a specific wavelength of light, it is excited to produce reactive oxygen species (ROS), resulting in tumour destruction. However, the efficacy of ROS generation for tumour damage is highly dependent on the uptake of the PS in tumour cells. Thus, PS selective/targeted uptake and delivery in tumour cells is a crucial factor in PDT cancer drug absorption studies. Generally, within non-targeted drug delivery mechanisms, only minor amounts of PS are able to passively accumulate in tumour sites (due to the enhanced permeability and retention (EPR) effect) and the remainder distributes into healthy tissues, causing unwanted side effects and poor treatment prognosis. Thus, to improve the efficacy of PDT cancer treatment, research is currently focused on the development of specific receptor-based PS-nanocarrier platform drugs, which promote the active uptake and absorption of PS drugs in tumour sites only, avoiding unwanted side effects, as well as treatment enhancement. Therefore, the aim of this review paper is to focus on current actively targeted or passively delivered PS nanoparticle drug delivery systems, that have been previously investigated for the PDT treatment of cancer and so to deduce their overall efficacy and recent advancements.
Highlights
Cancer is the second leading cause of death after stroke and heart disease and so represents a major health concern worldwide [1,2]
photodynamic therapy (PDT) can provide an alternative treatment method to assist in the eradication of target cancer cells/tissues, while avoiding systematic toxicity and unwanted side in the eradication of target cancer cells/tissues, while avoiding systematic toxicity and unwanted side effects when compared to conventional therapies
These moieties or ligands) such as antibodies, peptides or aptamers to their surface (Figure 3) [15,20]. These moieties have a specific affinity for specific receptors, which are only overexpressed on the tumour cells and their vasculature, but not on normal cells [16]. This surface functionalisation of NPPS drug delivery systems facilitates a more effective, specific and active accumulation and sub-cellular of PSs in tumour tissues or cells
Summary
Cancer is the second leading cause of death after stroke and heart disease and so represents a major health concern worldwide [1,2]. The main issue when treating cancer patients with conventional therapies such as chemotherapy or radiation, is that these forms of treatment tend to have a low selectivity for cancer cells and so are required to be administered in high toxic drug loads to be considered effective [5]. These high toxic drug loads tend to affect normal body cells as well, often inducing severe unwanted side effects when patients undergo these forms of treatment [5]. Effective forms of treatment [6]
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