Abstract:
We describe the synthesis and characterization of a thiol-functionalized porphyrin derivative 2 and
its gold nanoparticle conjugates. The porphyrin 2 exhibited its characteristic intense Soret absorption at 420 nm
with a molar extinction coefficient value of 3.6 × 105M−1 cm−1 and good fluorescence in the region of 650–
660 nm. The porphyrin-capped gold nanoparticles (POPNPs) were synthesized from the citrate-capped gold
nanoparticles by the ligand exchange method and characterized by spectroscopic and morphological analyses
(UV–Vis, DLS and TEM). The broadening of the absorption spectrum and quenching of the fluorescence
intensity for the porphyrin gold nanoconjugates suggest efficient incorporation of the porphyrin moiety onto
the gold surface. The results of DLS and TEM analyses indicate that the nanoconjugate POPNPs are uniformly
spherical in shape with a size of ca. 25 ± 5 nm and exhibits a negative zeta potential value of −16.0 ± 2 mV.
The singlet oxygen generation efficiency of the porphyrin 2 and POPNPs was calculated and are found to be ca.
0.53±0.02 and 0.43±0.03, respectively. The in vitro photobiological studies revealed that POPNPs exhibited
enhanced photodynamic activity compared to their parent porphyrin derivative 2 with an IC50 value of 5μM in
MDA MB 231 cell lines. The mechanism of the cell destruction was studied by Annexin-FITC and confirmed
through TMRM assay. We observed the increase in the percentage of cell population corresponding to the late
apoptotic stage ca. 37.7% and 51.2% for 5 and 10 μM of POPNPs, respectively, thereby demonstrating their
apoptotic-mediated cell destruction and use in PDT applications.
