Marius Hossu

X-ray-induced nanoparticle-based photodynamic therapy of cancer

AIM In this study, Ce(3+)-doped lanthanum(III) fluoride (LaF3:Ce(3+)) nanoparticles were synthesized by a wet-chemistry method in dimethyl sulfoxide (DMSO) and their application as an intracellular light source for photodynamic activation was demonstrated. MATERIALS & METHODS The LaF3:Ce(3+)/DMSO nanoparticles have a strong green emission with a peak at approximately 520 nm, which is effectively overlapped with the absorption of protoporphyrin IX (PPIX). The nanoparticles were encapsulated into poly(D,L-lactide-co-glycolide (PLGA) microspheres along with PPIX. Upon irradiation with x-rays (90 kV), energy transfer from the LaF3:Ce(3+)/DMSO nanoparticles to PPIX occurs and singlet oxygen is generated for cancer cell damage. RESULTS The LaF3:Ce(3+)/DMSO/PLGA or LaF3:Ce(3+)/DMSO/PPIX/PLGA microspheres alone caused only sublethal cytotoxicity to the cancer cells. Upon x-ray irradiation, the LaF3:Ce(3+)/DMSO/PPIX/PLGA microspheres induced oxidative stress, mitochondrial damage and DNA fragmentation on prostate cancer cells (PC3). DISCUSSION The results indicate that x-rays can activate LaF3:Ce(3+) and PPIX nanocomposites, which can be a novel method for cancer destruction.

Solution combustion synthesis, photoluminescence and X-ray luminescence of Eu-doped nanoceria CeO2:Eu

Rare earth Eu3+-doped nanoceria with an average size of 60 nm were synthesized by urea–nitrate solution combustion reaction. The microstructure and morphology of the samples were characterized by X-ray diffraction patterns (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (SEM). The host is confirmed to be pure CeO2. However, there are two distinct oxygen surroundings due to the substitution of Ce4+ species with Eu3+ ions. The optical properties of CeO2:Eu were investigated by photoluminescence and X-ray luminescence spectroscopy. The samples can be excited with 360 nm (ultra-violet light, the charge transfer band of O–Ce) and 466 nm (blue light, the Eu3+ 7F0 → 5D2 transition) respectively, and exhibit typical red-light emission of Eu3+. At low Eu3+ concentrations, the sample can be effectively excited with 360 nm. With the increase of the Eu3+ concentration, the dominant excitation wavelength is changed to 466 nm, which is beneficial for use in solid state lighting because of the coincidence with the emission of GaN chips. Under the excitation of 466 nm, the quenching concentration of Eu3+ can be increased to 16 mol% due to the interface effects of the nanoscale materials. Furthermore, the X-ray luminescence of CeO2:Eu also shows strong red-light emission, manifesting that the material is a promising scintillator for radiation detection.

Folic acid-CdTe quantum dot conjugates and their applications for cancer cell targeting

In this study, we report the preparation, luminescence, and targeting properties of folic acid-CdTe quantum dot conjugates. Water-soluble CdTe quantum dots were synthesized and conjugated with folic acid using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide-N-hydroxysuccinimide chemistry. The influence of folic acid on the luminescence properties of CdTe quantum dots was investigated, and no energy transfer between them was observed. To investigate the efficiency of folic acid-CdTe nanoconjugates for tumor targeting, pure CdTe quantum dots and folic acid-coated CdTe quantum dots were incubated with human nasopharyngeal epidermal carcinoma cell line with positive expressing folic acid receptors (KB cells) and lung cancer cells without expression of folic acid receptors (A549 cells). For the cancer cells with positive folate receptors (KB cells), the uptake for CdTe quantum dots is very low, but for folic acid-CdTe nanoconjugates, the uptake is very high. For the lung cancer cells without folate receptors (A549 cells), the uptake for folic acid-CdTe nanoconjugates is also very low. The results indicate that folic acid is an effective targeting molecule for tumor cells with overexpressed folate receptors.

Interaction of porphyrins with CdTe quantum dots

Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

A new Cu–cysteamine complex: structure and optical properties

Here we report the structure and optical properties of a new Cu–cysteamine complex (Cu–Cy) with a formula of Cu3Cl(SR)2 (R = CH2CH2NH2). This Cu–Cy has a different structure from a previous Cu–Cy complex, in which both thio and amine groups from cysteamine bond with copper ions. Single-crystal X-ray diffraction and solid-state nuclear magnetic resonance results show that the oxidation state of copper in Cu3Cl(SR)2 is +1 rather than +2. Further, Cu3Cl(SR)2 has been observed to show intense photoluminescence and X-ray excited luminescence. More interesting is that Cu3Cl(SR)2 particles can produce singlet oxygen under irradiation by light or X-ray. This indicates that Cu3Cl(SR)2 is a new photosensitizer that can be used for deep cancer treatment as X-ray can penetrate soft tissues. All these findings mean that Cu3Cl(SR)2 is a new material with potential applications for lighting, radiation detection and cancer treatment.

X-ray luminescence of CdTe quantum dots in LaF3:Ce/CdTe nanocomposites

CdTe quantum dots have intense photoluminescence but exhibit almost no x-ray luminescence. However, intense x-ray luminescence from CdTe quantum dots is observed in LaF3:Ce/CdTe nanocomposites. This enhancement in the x-ray luminescence of CdTe quantum dots is attributed to the energy transfer from LaF3:Ce to CdTe quantum dots in the nanocomposites. The combination of LaF3:Ce nanoparticles and CdTe quantum dots makes LaF3:Ce/CdTe nanocomposites promising scintillators for radiation detection.

Enhancement of protoporphyrin IX performance in aqueous solutions for photodynamic therapy

Molecular modification of protoporphyrin IX (PpIX) was conducted to improve its water solubility and therapeutic performance for photodynamic therapy. The carboxylic acid and the two nitrogen atoms in the core of PpIX molecule were protonated following by conjugation with 3-aminopropyl triethoxysilane (APTES). Then, folic acid (FA) was conjugated to the APTES-coated PpIX (MPpIX) through chemical bonding between FA and protonated PpIX. The results showed that APTES coating can stabilize PpIX and increase its water solubility. Consequently, this leads to the enhancement in luminescence and singlet oxygen production. Upon X-ray irradiation, singlet oxygen can be detected in the MPpIX but not in PpIX. This means that MPpIX can be used for deep cancer treatment as X-ray can penetrate deeply into tissue. Molecular modification also reduces the dark toxicity of PPIX and increases their cell uptake. All these traits indicate that the Molecular modification of PpIX may potentially improve the efficacy of photodynamic therapy for cancer treatment.

Nonlinear enhancement of spontaneous biophoton emission of sweet potato by silver nanoparticles.

Ultraweak biophoton emission of cutting-injured sweet potato is enhanced by the incubation with Ag nanoparticles in a nonlinear way. The late peak of the emission after the cutting injury is amplified as much as 15 times, while only little amplification was identified for the emission measured immediately after the cutting. The effect requires the presence of nutritive media to support the active metabolic processes and is also affected by the timing of the addition of the Ag nanoparticles. Proposed mechanisms of reactive oxygen species generation and energy resonance transfer are discussed.

Enhancement of biophoton emission of prostate cancer cells by Ag nanoparticles

Ultraweak intrinsic bioluminescence of cancer cell is a noninvasive method of assessing bioenergetic status of the investigated cells. This weak biophoton emission generated by prostate cancer cells (PC3) was measured in the presence of Ag nanoparticles and its correlation with singlet oxygen production was investigated. The comparison between nanoparticles concentration, bioluminescence intensity, and cell survival showed that Ag nanoparticles do not significantly affect cell survival at used concentration but they increase cell bioluminescent processes. It was also confirmed that singlet oxygen contributes to biophoton emission, that Ag nanoparticles increase this contribution, and that there are secondary mechanisms independent of singlet oxygen by which Ag nanoparticles contribute to increased cellular bioluminescence, possibly through plasmon resonance enhancement of intrinsic fluorescence.

Synthesis of ZnS:Ag,Co water-soluble blue afterglow nanoparticles and application in photodynamic activation

Silver and cobalt co-doped ZnS (ZnS:Ag,Co) water-soluble afterglow nanoparticles were synthesized using a wet chemistry method followed by aging at room temperature. The nanoparticles had a cubic zinc blende structure with average sizes of approximately 4 nm and emitted a blue fluorescence emission centered at 441 nm due to radiative transitions from surface defects to Ag(+) luminescent centers. Intense afterglow emission peaking at 475 nm from the obtained nanoparticles was observed and was red-shifted compared to the fluorescence emission peak. X-ray photoelectron spectroscopy revealed a large increase of O/S ratio, indicating a surface oxidation process during aging. The S vacancies produced accordingly may contribute to form more electron traps and enhance afterglow. The ZnS:Ag,Co afterglow nanoparticles have a very low dark-toxicity and are applied as a light source for photodynamic therapy activation by conjugating with protoporphyrin together. Our preliminary study has shown that the ZnS:Ag,Co afterglow nanoparticles can significantly reduce the x-ray dosage used in activation and thus may be a very promising candidate for future x-ray excited photodynamic therapy in deep cancer treatment.