# Aggregation Tendency, Cellular Uptake, and Viability Effects of Structurally Distinct Carbazole–Phthalocyanine Gold Nanoconjugates

## TL;DR

Researchers studied how different gold nanoparticle-phthalocyanine conjugates behave in cells, focusing on their aggregation, uptake, and effects on cell viability.

## Contribution

The study introduces novel carbazole-containing phthalocyanine derivatives conjugated to gold nanoparticles and evaluates their cellular interactions.

## Key findings

- SiPc–AuNPs showed stronger aggregation tendency in medium compared to ZnPc–AuNPs.
- Pc–AuNPs caused detachment of A549 cancer cells but not endothelial cells, indicating cell-type-specific effects.
- Both SiPc- and ZnPc-based nanoconjugates localized similarly in cells, suggesting uptake is driven by the AuNP carrier.

## Abstract

Phthalocyanine–gold nanoparticle (Pc–AuNP)
conjugates
combine the unique properties of gold with the therapeutic potential
of phthalocyanines, offering a promising strategy for cancer therapy.
Here, two novel carbazole-containing Pcs, axially disubstituted Si­(IV)
and peripherally tetra-substituted Zn­(II) derivatives, were synthesized
and conjugated to gold nanoparticles of two core sizes (20 and 40
nm). Characterization was performed using TEM and SEM techniques.
Stability assays in complete medium showed a stronger aggregation
tendency for SiPc–AuNPs than for ZnPc–AuNPs. Bright-field
microscopy revealed that Pc–AuNPs induced detachment of A549
lung adenocarcinoma cells but not HUVEC endothelial cells, highlighting
a cell type–dependent effect. Despite this detachment, no significant
loss of viability occurred at 72 h, underscoring the resilience of
A549 cells to membrane and cytoskeletal stress. Once internalized,
both SiPc- and ZnPc-based nanoconjugates displayed similar cytoplasmic
and perinuclear localization, suggesting uptake was dominated by the
AuNP carrier. Preliminary MTT assays showed dye–particle interference,
leading to use of the PrestoBlue assay, which avoids insoluble formazan
artifacts. Viability analysis indicated that only Au40/SiPc transiently increased A549 reducing capacity at 24 h, likely due
to short-term ROS scavenging, which normalized by 72 h. Overall, these
findings demonstrate how metal center, substitution geometry, and
particle size collectively affect aggregation, cellular interactions,
and cytotoxic profiles, providing insights for optimizing Pc–AuNPs
as nanophototherapeutic agents.