Tailoring Pyro- and Orthophosphate Species to Enhance Stem Cell Adhesion to Phosphate Glasses

Nigel De Melo,Ifty Ahmed,Virginie Sottile,Md Towhidul Islam,Laura Macri-Pellizzeri,Jeremy J Titman,Lauren Murrell

doi:10.3390/ijms22020837

Nigel De Melo, Ifty Ahmed + Show 5 more

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https://doi.org/10.3390/ijms22020837

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Abstract

Phosphate-based glasses (PBGs) offer significant therapeutic potential due to their bioactivity, controllable compositions, and degradation rates. Several PBGs have already demonstrated their ability to support direct cell growth and in vivo cytocompatibility for bone repair applications. This study investigated development of PBG formulations with pyro- and orthophosphate species within the glass system (40 − x)P2O5·(16 + x)CaO·20Na2O·24MgO (x = 0, 5, 10 mol%) and their effect on stem cell adhesion properties. Substitution of phosphate for calcium revealed a gradual transition within the glass structure from Q2 to Q0 phosphate species. Human mesenchymal stem cells were cultured directly onto discs made from three PBG compositions. Analysis of cells seeded onto the discs revealed that PBG with higher concentration of pyro- and orthophosphate content (61% Q1 and 39% Q0) supported a 4.3-fold increase in adhered cells compared to glasses with metaphosphate connectivity (49% Q2 and 51% Q1). This study highlights that tuning the composition of PBGs to possess pyro- and orthophosphate species only, enables the possibility to control cell adhesion performance. PBGs with superior cell adhesion profiles represent ideal candidates for biomedical applications, where cell recruitment and support for tissue ingrowth are of critical importance for orthopaedic interventions.

Highlights

In regenerative medicine, restoration of biological function can be aided by biomaterials created from metals, ceramics or polymers offering a variety of chemical structures, surface properties, degradation rates, and mechanical stiffness [1,2]
To confirm the composition of the different Phosphate based glasses (PBGs) produced, EDX analysis was performed on each formulation and the measurements for P40, P35 and P30 confirmed that the materials were within 1–4 mol% of the target formulation with a maximum deviation in percentage difference revealed to be 1.7 mol% (Table 1)
Among the wide range of biomaterials being developed for orthopedic applications, PBGs offer significant advantages in terms of geometric and chemical versatility, which make them well-suited for regenerative medicine applications [27,34,41]

Summary

Introduction

Restoration of biological function can be aided by biomaterials created from metals, ceramics or polymers offering a variety of chemical structures, surface properties, degradation rates, and mechanical stiffness [1,2]. These properties allow for material functionalization to promote cell adhesion, support cell differentiation, exert anti-microbial effects, and assist drug delivery, among other applications [3,4,5]. The number of bridging oxygen atoms per tetrahedra, which define the Qn -speciation, are progressively broken down as network modifiers are added to the composition, decreasing connectivity within the glass [10]. Through modifications of the glass composition, it is entirely possible to influence a gradual decrease in structural connectivity (Q3 to Q0 ) which is denoted respectively as ultra-, meta-, pyro-, and orthophosphates [11,12,13]

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