# Covalently Surface-Functionalized Porphyrins on Silica Nanoparticles for Efficient Photodynamic Therapy

## TL;DR

Researchers developed silica nanoparticles with attached porphyrins for improved photodynamic therapy, showing enhanced cell-killing effects at low light doses.

## Contribution

A novel method of covalently attaching porphyrins to silica nanoparticles is introduced, demonstrating superior photocytotoxicity.

## Key findings

- Silica–porphyrin nanohybrids retained efficient singlet oxygen generation.
- H-PCOOH showed significantly enhanced photocytotoxicity compared to free porphyrins.
- H-PCOOH induced cell death at low light doses with an IC50 below 0.3 µM.

## Abstract

Silica nanoparticles (SiNPs) are widely explored as biocompatible platforms for the delivery of photosensitizers in photodynamic therapy (PDT). In this work, porphyrins bearing amine (PNH2) or carboxyl (PCOOH) groups were covalently conjugated onto functionalized SiNP surfaces via carbodiimide-mediated amide coupling, yielding the silica–porphyrin nanohybrids H-PNH2 and H-PCOOH. Successful surface functionalization was confirmed by Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Photophysical studies demonstrated that both nanohybrids retained efficient singlet oxygen (1O2) generation. In vitro biological assays revealed a strong dependence of photodynamic activity on the nature of the conjugated porphyrin, with H-PCOOH exhibiting markedly enhanced photocytotoxicity with respect to the free porphyrins, while H-PNH2 showed an attenuated light-dose response. Notably, H-PCOOH induced pronounced cell death at low light doses (1 J/cm2), with a half-maximal inhibitory concentration (IC50) below 0.3 µM. These findings highlight the potential of silica–porphyrin nanohybrids as efficient photosensitizers for PDT applications.