# Femtosecond Laser-Engineered β-TCP Scaffolds: A Comparative Study of Green-Synthesized AgNPs vs. Ion Doping Against S. aureus for Bone Regeneration

## TL;DR

This study compares green-synthesized silver nanoparticles and ion doping on laser-modified β-TCP scaffolds to combat S. aureus infections and support bone regeneration.

## Contribution

A novel approach combining femtosecond laser processing with green-synthesized AgNPs or ion doping to enhance β-TCP scaffolds for antibacterial and osteogenic purposes.

## Key findings

- AgNP-functionalized scaffolds showed superior antibacterial activity against S. aureus compared to ion-doped variants.
- Femtosecond laser processing created nanostructures that improved scaffold roughness and wettability.
- Both strategies supported osteogenic differentiation of hBM-MSCs, though with some cytotoxicity at higher doses.

## Abstract

Implant-associated infections, particularly those linked to Staphylococcus aureus (S. aureus), continue to compromise the clinical success of β-tricalcium phosphate (β-TCP) implants despite their excellent biocompatibility and osteoconductivity. This investigation aims to tackle these challenges by integrating femtosecond (fs)-laser surface processing with two complementary strategies: ion doping and functionalization with green-synthesized silver nanoparticles (AgNPs). AgNPs were produced via fs-laser photoreduction using green tea leaf extract (GTLE), noted for its anti-inflammatory and antioxidant properties. Fs-laser processing was applied to modify β-TCP scaffolds by systematically varying scanning velocities, fluences, and patterns. Lower scanning velocities generated organized nanostructures with enhanced roughness and wettability, as confirmed by scanning electron microscopy (SEM), optical profilometry, and contact angle measurements, whereas higher laser energies induced significant phase transitions between hydroxyapatite (HA) and α-tricalcium phosphate (α-TCP), as revealed by X-ray diffraction (XRD). AgNP-functionalized scaffolds demonstrated markedly superior antibacterial activity against S. aureus compared to the ion-doped variants, attributed to the synergistic interplay of nanostructure-mediated surface disruption and AgNP-induced bactericidal mechanisms. Although ion-doped scaffolds exhibited limited direct antibacterial effects, they showed concentration-dependent activity in indirect assays, likely due to controlled ion release. Both strategies promoted osteogenic differentiation of human bone marrow mesenchymal stem cells (hBM-MSCs) under defined conditions, albeit with transient cytotoxicity at higher fluences and excessive ion doping. Overall, this approach holds promise for markedly improving antibacterial efficacy and osteogenic compatibility, potentially transforming bone regeneration therapies.