Negin Kamyar1 Ryan Greenhalgh5 Tatiana Nascimento2 Eliton Medeiros2 Peter Matthews3 Liebert Nogueira4 Håvard Haugen4 David Lewis1 Jonny Blaker1

1, School of Materials, University of Manchester, Manchester, , United Kingdom
5, Department of Physics, Cambridge University, Cambridge, , United Kingdom
2, Department of Materials Engineering, Federal University of Paraíba, João Pessoa, , Brazil
3, School of Chemical & Physical Science, Keele University, Newcastle, , United Kingdom
4, Department of Biomaterials, University of Oslo, Oslo, , Norway

Black phosphorus (BP) is a two-dimensional (2-D) semiconductor with a tuneable direct band gap and highly anisotropic properties. It is inherently unstable and degrades into phosphate ions in aqueous media via oxidation 1. Whilst the current paradigm with 2D materials leans toward stabilisation, in this study, we do the opposite and explore the use of 2D BP as a source of phosphate ions by exploiting its inherent instability for controlled phosphate ion release. Liquid exfoliated BP 2 was incorporated into degradable poly (lactide-co-glycolide) (PLGA) fibres via solution blow spinning 3,4, forming a flexible 3-D nanocomposite with a continuous open-fibre structure. With increasing BP concentration, the average fibre diameter increased by 43%, which we attribute to changes in the precursor solution properties including surface tension and viscosity. Raman spectroscopy along with ICP-AES confirmed the incorporation of BP into the nanocomposite. By increasing the initial loading of BP there was an increase in the BP optical phonon mode intensity in Raman spectra. ICP-AES was used to quantify exact BP loading and demonstrated that modifying the initial loading of BP in the PLGA fibres permitted tuneable release rates of phosphate ions over 8 weeks in vitro. Hence, the release rate of phosphate ions from PLGA-BP nanocomposite fibres can be controlled by compositional tuning of BP and lactide to glycolide ratio in the PLGA. Such nanocomposites have advantages over conventional bioactive glasses as they do not exhibit brittle behaviour which imparts great potential for non-load-bearing bone tissue applications and flexible therapeutic implants.

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3. R. D. Greenhalgh, W. S. Ambler, S. J. Quinn, E. S. Medeiros, M. Anderson, B. Gore, A. Menner, A. Bismarck, X. Li, N. Tirelli and J. J. Blaker, Journal of Materials Science, 2017, 52, 9066-9081.
4. E. L. G. Medeiros, A. L. Braz, I. J. Porto, A. Menner, A. Bismarck, A. R. Boccaccini, W. C. Lepry, S. N. Nazhat, E. S. Medeiros and J. J. Blaker, ACS Biomaterials Science & Engineering, 2016, 2, 1442-1449.