# Dual pH-Responsive Calcium Phosphate Nanoparticles Conjugated with Folate by CuAAC Click Chemistry for Targeted Gemcitabine Delivery to Cancer Cells

## TL;DR

This paper describes a new method to deliver the chemotherapy drug gemcitabine using pH-sensitive calcium phosphate nanoparticles targeted to cancer cells.

## Contribution

The novelty is the dual pH-responsive nanoparticle system with folate conjugation via CuAAC click chemistry for targeted drug delivery.

## Key findings

- The nanoparticles showed pH-responsive release of gemcitabine in endolysosomes.
- Folate conjugation increased uptake in folate receptor-positive cancer cells.
- The system exhibited high cytotoxicity in cancer cells while sparing normal cells.

## Abstract

Calcium phosphate
nanoparticles (CaP NPs) are biocompatible carriers
widely studied for drug delivery due to their pH-responsive degradation
and controlled release properties. In this study, CaP NPs stabilized
with carboxymethyl cellulose (CMC) and coated with a silica layer
were designed for gemcitabine (GEM) loading and folate (FA) conjugation,
targeting cancer cells overexpressing folate receptor alpha (FRα).
GEM was covalently coupled to CMC via an amide bond before CaP precipitation,
creating a prodrug system. The NPs exhibited dual pH-responsive release,
in which CaP dissolution combined with polymer-drug cleavage through
acid-catalyzed hydrolysis of CMC-GEM within endolysosomes ensured
intracellular bioavailability of free GEM molecules. FA conjugation
by strong covalent bonds via copper-catalyzed azide–alkyne
cycloaddition (CuAAC) click reaction enhanced the uptake of CaP NPs
in FRα-positive breast cancer cells (MCF-7), whereas both FA-conjugated
and nonconjugated NPs exhibited similar uptake in normal human mesenchymal
stem cells (hMSCs). GEM-loaded CaP NPs showed high cytotoxicity in
FRα-overexpressing cancer cell lines (MCF-7, MDA-MB-231, HeLa),
while FA conjugation significantly reduced toxicity in hMSCs without
compromising anticancer activity. These findings demonstrate the potential
of FA-conjugated and GEM-loaded CaP NPs as a nanoplatform for targeted
cancer therapy with reduced toxicity in healthy cells.