Protoporphyrin IX (PpIX)-conjugated Self-lighting Nanoparticles For Photodynamic Therapy: Synthesis And Characterization

Abstract

In Photodynamic therapy (PDT) PDT, cancer destruction relies on applying a photosensitizing drug (PS) followed by light. Absorbed light can activate the PS to transfer energy to existing molecules and substrates or to oxygen to generate singlet oxygen which are highly toxic to cells. Protophorphyrin IX (PpIX) is a photosensitizers (PSs) which has FDA approval and an absorbance near the Soret band which is 10 times stronger than the absorbance in Q-band (600nm). Our goal was to design a modality to eliminate of external blue light in addition to increasing the drug's water dispersion which finally may result in enhancing PDT efficiency. The hypothesis of this study proposes an enhanced PDT efficiency through the delivery of synthesized afterglow nanoparticles (AG NPs), which may be excited by both X-ray and UV and emit blue light for a long time, even after removing the energy source; Folic acid-PpIX-conjugated NPs could also improve the water dispersion of PpIX. Afterglow alkaline earth silicates (Sr3MgSi2O8) nanoparticles doped with rear earth elements (Eu, Dy) were synthesized through this study; the best parameters to achieve a successful synthesis were investigated. the silanol groups oriented outside of the AG NPs caused a net negative surface charge (-38.52 mV). Alkaline wet grinding decreased the NP size from 809 ± 40.9 nm to 399.5 ± 117.5 nm. The surface silanization of synthesized AG NPs was induced to introduce an NH2 functional group on the surface of AG NPs for further drug and FA conjugation. After APTES coating, the surface charge changed to -4.28 mV because NH2 oriented out of the NPs surface. Adding a new layer caused size increments to 458 ± 136.8 nm. Calculations of Conjugation efficiency (CE) proved that 100 µg/ml of APTES-coated AG NPs was containing of 43.043 ± 6.42 µg/ml of APTES. Protonated PpIX dicholoride with high reactive COOH groups were successfully conjugated to the surface of APTES-AG NPs which led to better water dispersion of PpIX-AG NPs and caused 20 times enhancement of the red emission intensity of PpIX- AG NPs for the concentration equal to 6.25 µg/ml of free PpIX compared to the same concentration of PpIX in water; in addition, 4 times concentration decrement of drug was observed to get most intense red emission. The results of the spectrofluorophotometer confirmed that FRET had happened between APTES-AG NPs and PpIX which corresponds to the successful conjugation of PpIX and NPs. The size decreased to 232 ± 1.3 nm. Raman spectroscopy results confirmed not only PpIX but also FA were successfully conjugated to APTES-AG NPs. Ultimate NPs (FA-PpIX-APTES-AG NPs) could improve the generation of singlet oxygen 2.4% more than free PpIX for concentration of 1.5 µg/ml of free PpIX. Conjugation efficiency (CE) calculation showed that in 100 µg/ml PpIX-APTES-AG NPs, there was a 2.050±0.207 µg/ml of conjugated PpIX and 100 µg/ml PpIX-APTES-AG NPs was containing 26.87±2.998 µg/ml of FA. Exposed PC3 cells to ultimate NPs (equal to 5µg/ml of free PpIX) demonstrated 30% less dark toxicity and almost 15% more toxicity after exposure to UV for 5 min compared to that of free PpIX. All mentioned results proved that the fabrication of FA-PpIX-conjugated AG NPs may introduce an acceptable solution to current challenges of PDT including weak penetration of blue light and low water dispersion of PpIX in water.