# Loading Density Influences the Tumor Cell Targeting and Signaling Inhibition Capabilities of Antibody Nanoconjugates

## TL;DR

This study shows that lower antibody density on nanoconjugates improves targeting and treatment of triple-negative breast cancer cells.

## Contribution

The study reveals that lower antibody loading density enhances the therapeutic efficacy of antibody–nanoparticle conjugates in targeting TNBC cells.

## Key findings

- Low-density antibody nanoconjugates showed ∼2× greater binding avidity to TNBC cells compared to high-density conjugates.
- Low-density conjugates significantly reduced tumor spheroid area, metabolic activity, and cell number in TNBC cells.
- Lower antibody density improved Wnt signaling inhibition and suppressed oncogenic cell behavior more effectively.

## Abstract

Triple-negative breast cancer (TNBC) is the most aggressive
breast
cancer subtype and accounts for up to 20% of all breast cancers. Since
conventional chemotherapy and radiotherapy are ineffective against
TNBC, nanoparticle-based medicines are being investigated as a potentially
superior treatment option. Of such platforms, antibody–nanoparticle
conjugates have been shown to precisely target diseased cells through
selective antigen binding and to regulate oncogenic cellular signaling
by blocking ligand activation of the targeted receptor. For example,
silica core-gold shell “nanoshells” (NS) conjugated
to Frizzled7 (FZD7) antibodies can preferentially bind TNBC cells
to suppress Wnt signaling and inhibit disease progression. To improve
understanding of antibody nanoconjugate structure/function relationships,
in this study, we evaluated the influence of antibody loading density
on the ability of FZD7-NS conjugates to bind TNBC cells, suppress
Wnt signaling, and inhibit oncogenic cell behavior. We found that
a lower antibody loading density of ∼60 antibodies per NS provided
increased TNBC cellular binding and enhanced therapeutic efficacy
compared to a higher antibody loading of ∼170 antibodies per
NS. Specifically, the low-density FZD7-NS exhibited ∼2×
greater binding avidity to MDA-MB-231 human TNBC cells than high-density
FZD7-NS, yielding more robust inhibition of several Wnt target genes,
as measured by RT-qPCR. Congruently, tumor spheroids formed from MDA-MB-231
cells that were pretreated with low-density FZD7-NS had significantly
reduced area, metabolic activity, and cell number compared to those
treated with high-density FZD7-NS. These results emphasize the importance
of determining the appropriate surface ligand density when designing
antibody–nanoparticle conjugates for therapeutic utility.