# 3D-printed titanium scaffolds coated with a multifunctional photothermal-responsive hydrogel promote osteoporotic bone defect repair

## TL;DR

A new hydrogel coating for 3D-printed titanium scaffolds helps repair osteoporotic bone defects by promoting healing and reducing inflammation.

## Contribution

A multifunctional photothermal-responsive hydrogel coating is developed to enhance osteoporotic bone repair.

## Key findings

- The hydrogel coating improved stem cell migration, adhesion, and osteogenic differentiation in vitro.
- In vivo, the coated scaffolds significantly enhanced osteoporotic bone defect repair.
- The coating exhibited anti-inflammatory, antioxidant, and self-healing properties under near-infrared irradiation.

## Abstract

Osteoporotic bone defects are difficult to repair since conventional titanium scaffolds lack bioactivity and cannot overcome impaired osteogenesis, chronic inflammation, oxidative stress, and cellular senescence. To address these limitations, a multifunctional tannic acid (TA)-based hydrogel coating was developed for 3D-printed titanium alloy scaffolds. The hydrogel was formed from TA, acrylamide, and 3-acrylamidophenylboronic acid, with osteogenic growth peptide (OGP) as a bioactive component. Prussian blue (PB) nanoparticles and quercetin (QUE) were incorporated to provide dynamic crosslinking, photothermal conversion, antioxidant, and anti-inflammatory functions. Stromal cell-derived factor-1α (SDF-1α) was further integrated to recruit endogenous stem cells. The coating exhibited enhanced antiwear and self-healing properties, while near-infrared irradiation (NIR) triggered PB-mediated photothermal effects, thereby improving biotribological performance and accelerating self-repair. In vitro, the hydrogel coating combined with NIR promoted bone marrow mesenchymal stem cell migration, adhesion, and osteogenic differentiation, while simultaneously scavenging reactive oxygen species, attenuating inflammation, reducing cellular senescence, and inducing M2 macrophage polarization. In vivo, the hydrogel coated 3D-printed titanium scaffold markedly enhanced osteoporotic bone defect repair. Overall, this multifunctional hydrogel coating transforms passive titanium scaffolds into bioactive implants, offering a promising strategy for promoting osteoporotic bone regeneration.

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