Abstract
This work reports for the first time on the synthesis, characterization, and photodynamic
therapy efficacy of the novel aluminium (III) chloride 2(3), 9(10), 16(17), 23(24)-tetrakis-(sodium
2-mercaptoacetate) phthalocyanine (AlClPcTS41) when alone and when conjugated to PEGylated
copper–gold bimetallic nanoparticles (PEG-CuAuNPs) as photosensitizers on colon cancer cells
(Caco-2). The novel AlClPcTS41 was covalently linked to the PEG-CuAuNPs via an amide bond to
form AlClPcTS41-PEG-CuAuNPs. The amide bond was successfully confirmed using FTIR while
the crystal structures were studied using XRD. The morphological and size variations of the PEGCuAuNPs
and AlClPcTS41-PEG-CuAuNPs were studied using TEM, while the hydrodynamic sizes
and polydispersity of the particles were confirmed using DLS. The ground state electron absorption
spectra were also studied and confirmed the typical absorption of metallated phthalocyanines and
their nanoparticle conjugates. Subsequently, the subcellular uptake, cellular proliferation, and PDT
anti-tumor effect of AlClPcTS41, PEG-CuAuNPs, and AlClPcTS41-PEG-CuAuNPs were investigated
within in vitro Caco-2 cells. The designed AlClPcTS41 and AlClPcTS41-PEG-CuAuNPs demonstrated
significant ROS generation abilities that led to the PDT effect with a significantly decreased viable
cell population after PDT treatment. These results demonstrate that the novel AlClPcTS41 and
AlClPcTS41-PEG-CuAuNPs had remarkable PDT effects against Caco-2 cells and may trigger apoptosis
cell death pathway, indicating the potential of the AlClPcTS41 and AlClPcTS41-PEG-CuAuNPs in
enhancing the cytotoxic effect of PDT treatment.