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Microbial poly-γ-glutamic acid (γ-PGA) as an effective tooth enamel protectant
Parati, Mattia Clarke, Louisa Anderson, Paul Hill, Robert Khalil, Ibrahim Stanley, Michele S McGee, Donal Mendrek, Barbara Kowalczuk, Marek
Parati, Mattia
Clarke, Louisa
Anderson, Paul
Hill, Robert
Khalil, Ibrahim
Stanley, Michele S
McGee, Donal
Mendrek, Barbara
Kowalczuk, Marek
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2022-07-20
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Abstract
Poly-γ-glutamic acid (γ-PGA) is a bio-derived water-soluble, edible, non-immunogenic nylon-like polymer with the biochemical characteristics of a polypeptide. This Bacillus-derived material has great potential for a wide range of applications, from bioremediation to tunable drug delivery systems. In the context of oral care, γ-PGA holds great promise in enamel demineralisation prevention. The salivary protein statherin has previously been shown to protect tooth enamel from acid dissolution and act as a reservoir for free calcium ions within oral cavities. Its superb enamel-binding capacity is attributed to the L-glutamic acid residues of this 5380 Da protein. In this study, γ-PGA was successfully synthesised from Bacillus subtilis natto cultivated on supplemented algae media and standard commercial media. The polymers obtained were tested for their potential to inhibit demineralisation of hydroxyapatite (HAp) when exposed to caries simulating acidic conditions. Formulations presenting 0.1, 0.25, 0.5, 0.75, 1, 2, 3 and 4% (w/v) γ-PGA concentration were assessed to determine the optimal conditions. Our data suggests that both the concentration and the molar mass of the γ-PGA were significant in enamel protection (p = 0.028 and p < 0.01 respectively). Ion Selective Electrode, combined with Fourier Transform Infra-Red studies, were employed to quantify enamel protection capacity of γ-PGA. All concentrations tested showed an inhibitory effect on the dissolution rate of calcium ions from hydroxyapatite, with 1% (wt) and 2% (wt) concentrations being the most effective. The impact of the average molar mass (M) on enamel dissolution was also investigated by employing commercial 66 kDa, 166 kDa, 440 kDa and 520 kDa γ-PGA fractions. All γ-PGA solutions adhered to the surface of HAp with evidence that this remained after 60 min of continuous acidic challenge. Inductively Coupled Plasma analysis showed a significant abundance of calcium ions associated with γ-PGA, which suggests that this material could also act as a responsive calcium delivery system. We have concluded that all γ-PGA samples tested (commercial and algae derived) display enamel protection capacity regardless of their concentration or average molar mass. However, we believe that γ-PGA D/L ratios might affect the binding more than its molar mass.
Citation
Parati M, Clarke L, Anderson P, Hill R, Khalil I, Tchuenbou-Magaia F, Stanley MS, McGee D, Mendrek B, Kowalczuk M, Radecka I. (2022) Microbial Poly-γ-Glutamic Acid (γ-PGA) as an Effective Tooth Enamel Protectant. Polymers, 14(14):2937. https://doi.org/10.3390/polym14142937
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Journal article
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en
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© 2022 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/polym14142937
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2073-4360
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2073-4360
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This work was partially supported the University of Wolverhampton Research Investment Fund (RIF4); ERDF Science in Industry Research Centre (SIRC 01R19P03464) project and BBSRC Algae-UK for Proof of Concept project BB/S009825/1; UCL Ref: 5749484.