Bioactive glasses as potential radioisotope vectors for in situ cancer therapy: investigating the structural effects of yttrium

Abstract

The incorporation of yttrium in bioactive glasses (BGs) could lead to a new generation of radionuclide vectors for cancer therapy, with high biocompatibility, controlled biodegradability and the ability to enhance the growth of new healthy tissues after the treatment with radionuclides. It is essential to assess whether and to what extent yttrium incorporation affects the favourable properties of the BG matrix: ideally, one would like to combine the high surface reactivity typical of BGs with a slow release of radioactive yttrium. Molecular Dynamics simulations show that, compared to a BG composition with the same silica fraction, incorporation of yttrium results in two opposing effects on the glass durability: a more fragmented silicate network (leading to lower durability) and a stronger yttrium-mediated association between separate silicate fragments (leading to higher durability). The simulations also highlight a high site-selectivity and some clustering of yttrium cations, which are likely linked to the observed slow rate of yttrium released from related Y-BG compositions. Optimisation of yttrium BG compositions for radiotherapy applications thus depends on the delicate balance between these effects.

Effect of strontium inclusion on the bioactivity of phosphate-based glasses

“…Using this new potential, we have shown that the Sr-O bond length is *2.44-2.49 Å and the Table 6 The average number of fragments bound to each Na, Ca or Sr atom for the glass compositions studied coordination number is 7.5-7.8; both of these quantities are larger than for Na-O or Ca-O, which have typical coordination numbers of less than seven. Although all three modifier ions prefer to bond to non-bridging oxygen atoms, the extent to which each of them does so depends on their field strength [24]. Sodium has the lowest field strength and the lowest percentage of NBOs in its first coordination shell and calcium has the highest field strength and the largest percentage of NBOs in its first coordination shell, while strontium is intermediate between the two.…”

“…Molecular dynamics (MD) simulations provide the atomic structure of the glass, as well as enabling computation of large-scale materials properties. We and others have previously used MD simulations to elucidate the connection between atomic structure and dissolution behaviour of a variety of silicate [20][21][22][23][24][25][26][27] and phosphate glasses [28][29][30] intended for implantation, including strontium-containing silicate glass [13,14]. However, there have been no simulations of Sr in phosphate glass.…”

Characterization of Y2O3 and CeO2 doped SiO2-SrO-Na2O glasses

“…Y and Ce are similar in ionic size to Na, however, as trivalent and tetravalent ions their associated field strength is higher which may impart a covalent characteristic to the O atoms they associate with within the glass network. In addition, the coordination environment of both Y and Ce in glasses has been found to be between 6 and 8 where they preferentially associate with NBOs [45,52,53]. These characteristics are likely producing the increase seen in Tg where stronger Y-NBO and Ce-NBO association with multiple NBOs increase the stability, and likely has implications for their movement through the glass structure in vivo which has been observed through lack of release in SBF studies [9,34,54].…”

Investigating the Effect of Glass Ion Release on the Cytocompatibility, Antibacterial Eflcacy and Antioxidant Activity of Y2O3 / CeO2 doped SiO2-SrO-Na2O glasses

“…In addition, it can be seen that over the 30 day time period the antioxidant potential slightly increases for the Con, LY, LCe and HCe glass extracts, while no effect is observed for the HY and YCe glass extracts as the Si release is stable for Y and Ce containing glasses and decreases for Con. This is likely due to a maximum concentration of the negatively charged silicic acid polymers that can be generated with a given Si concentration and pH [43,61]. Therefore, for the Y and Ce containing glasses at a stable Si concentration, a slight increase in pH observed with respect to time, may produce an associated increase in antioxidant activity.…”