Multifunctional nanoparticles for radiotherapy enhancement and targeted phototherapies

In 2024, the National Institutes of Health reported 2 million new cancer cases and 600,000 cancer-related deaths in the United States. Cancer remains a complex disease and a significant public health challenge. Conventional cancer treatments such as surgery, chemotherapy, and radiotherapy are successful. However, localization of the treatment, tumor specificity, adverse side effects of the treatments, and cancer metastases are still challenging issues. Novel treatment strategies that overcome these limitations are the focus of researchers, which is to increase the survival rate and improve patients' comfort. Radiotherapy (RT), a commonly used cancer treatment, uses ionizing radiation to kill or prevent the growth of malignant cells. It is a relatively local treatment compared to chemotherapy but is usually combined with other treatment methods for more efficient results. Some concerns associated with this treatment are dose heterogeneity, side effects on healthy tissues, and the radio-resistance of specific cancer cells. Radiosensitizers allowing local radiation enhancement at low doses of ionizing radiation and more homogeneous dose distribution within the tumor are highly popular and the subject of continuous research. Light-based therapies, such as photothermal and photodynamic therapies, may be combined with RT to enhance the treatment efficacy. These techniques provide a local, turn-on mechanism for cancer treatment. Photothermal therapy (PTT) is based on local hyperthermia caused by light irradiation of a photosensitizer (PS). Photodynamic therapy (PDT) relies on activating a photosensitizer by light and generating reactive oxygen species. Limitations in these therapies include solubility and bioavailability of the photosensitizer, day-light sensitivity of the patient, and activation of PSs mostly in blue, exerting a significant limitation in penetration depth. Protoporphyrin IX (PpIX), a common PDT photosensitizer typically irradiated with blue or red light, has been recently reported to be activated with X-ray, and this process is called radio dynamic therapy (RDT). This thesis explores the theranostic applications of gold-gold sulfide nanoparticles (GGS) with strong absorbance in the near-infrared, contrast ability in photoacoustic imaging (PAI), and potential for radiosensitization for low-dose RT, and combination of low-dose RT with phototherapies to improve therapeutic outcomes. In this thesis work, a combination of RDT with low-dose RT, bypassing high radiation dose requirements and light penetration limitations, was investigated via 5-aminolevulinic acid (ALA) loaded branched polyethyleneimine-coated GGS (bPEI-GGS) nanoparticles. ALA is a pro-drug converted to PpIX in living cells, more so in cancer cells. In vitro activity assessments were performed on PC3 prostate cancer and MDA-MB-231 breast cancer cell lines at low X-ray doses between 0.5, 1, 2, and 4 Gy. Cell viability dropped below 20% after 0.5 Gy RDT treatment with a low dose of GGS (Au concentration (μg/ml)/ALA concentration (mM): 25/0.22) for both cell lines. ALA-bPEI-GGS nanoparticles represent a promising approach to enhancing RDT effectiveness, especially for deep-seated and radioresistant tumors, with a level of selectivity towards cells overexpressing PEPT1/PEPT2. In the second part of the thesis, tumor-specific delivery of multifunctional nanoparticles providing a combination of photothermal therapy (PTT) and low-dose RT for improved therapeutic outcomes under mild conditions has been demonstrated using theranostic GGS nanoparticles with no further therapeutic agents. Multifunctional 3-mercaptopropionic acid-coated GGS (3MPA-GGS) were tagged with folic acid (FA-3MPA-GGS) to selectively target folate receptor-positive (FR+) cancer cells, enhancing therapeutic specificity and efficacy. FA-3MPA-GGS demonstrated strong NIR absorption, high-temperature increase, photothermal stability, and efficient light-to-heat conversion in the solution when irradiated with 808 nm, 215 mW laser. In vitro experiments performed with FR+ (HeLa and MDA-MB-231) and FR- (A549) cells indicated enhanced uptake, increased ROS generation, and more significant cytotoxicity in FR+ cells. Combining mild PTT with low-dose RT via FA-3MPA-GGS led to synergistic effects, lowering the treatment dose and enabling image-guided precision. Near-complete death of HeLa and MDA-MB-231 were obtained with PTT/RT at 200 μg Au/mL concentration, with 10 min 795 nm (1 W) laser irradiation followed w 0.5 Gy X-ray irradiation. This thesis's third part focuses on phototherapies without the use of ionizing radiation: the combination of nanoparticle-driven PTT and ALA-PDT. A novel dual-mode phototherapy approach for the treatment of prostate cancer using ALA-loaded superparamagnetic iron oxide nanoparticles (ALA-PAA-SPIONs) was demonstrated. Utilizing the upregulation of PEPT1/PEPT2, effective in selective transport of ALA, in prostate cancer cells presents a valuable target for enhancing delivery and specificity in treatment. In vitro experiments on LNCaP, PC3, and DU145 cell lines demonstrated selective cellular uptake of NPs in PEPT1/PEPT2 overexpressed LNCaP and PC3 cells. Formation of reactive oxygen species (ROS) and induction of apoptosis upon laser irradiation (640 nm, 700 mW, 10 minutes) lead to significant loss of cell viability (<10%), specifically in these two cell lines. The results showed the potential of ALA-PAA-SPION as a promising phototherapy agent for prostate cancer treatment, offering improved specificity and minimized systemic effects.