# Dual Structural Role of Niobium in Bioactive Borate Glasses Modulates Bioactivity, Cytocompatibility, and Hemostatic Potential

## TL;DR

This paper explores how adding niobium to borate glasses changes their structure and biological properties, such as bioactivity and cell compatibility.

## Contribution

The study reveals niobium's dual structural role in borate glasses, influencing their multifunctional biological performance.

## Key findings

- Niobium acts as a network former at low concentrations and a network modifier at higher concentrations.
- Structural changes due to niobium suppress surface reactivity and ion release.
- Nb-containing glasses show maintained cytocompatibility but reduced hemostatic potential.

## Abstract

Designing bioactive glasses with tunable biological responses
requires
a precise understanding of how network modifiers influence structure–property
relationships. This work investigates the effect of incorporating
niobium pentoxide (Nb2O5) into melt-derived
borate glasses, aiming to uncover how Nb affects the glass structure
and its multifunctional biological performance. Glasses with nominal
compositions: 60B2O3–(19-x/2)­CaO–(19-x/2)­Na2O–2P2O5–xNb2O5 (x = 0, 2.5, 5, 7.5, and 10 wt %) were synthesized
and comprehensively characterized. A key finding is the dual structural
role of Nb: it predominantly acts as a network former at ≤5
wt % and as a network modifier at higher contents. This transition
directly influences the glass network connectivity, as supported by
physical, thermal, and vibrational techniques, and reflected a conversion
from BO4 to BO3 units with an increase in Nb
content, correlating with a modification in hardness and elastic modulus.
Structural changes also suppressed surface reactivity and ion release,
leading to a modulation in hydroxycarbonate apatite formation in simulated
body fluid. On the other hand, glasses containing Nb maintained or
enhanced cytocompatibility with human adipose mesenchymal stem cells.
In contrast, Nb-containing glasses demonstrated reduced hemostatic
potential, likely due to Nb forming niobate complexes that may influence
ion exchange and clotting pathways. Overall, these findings shed light
on the potential of Nb incorporation as a strategy to tailor the multifunctional
properties of bioactive borate glasses for targeted biomedical applications
and offer a fresh perspective on how the dual structural role of niobium
contributes to their overall performance within the context of biomaterials.