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Tissue Engineering and Regenerative Medicine

A Multifunctional Zinc Oxide/Poly(Lactic Acid) Nanocomposite Layer Coated on Magnesium Alloys for Controlled Degradation and Antibacterial Function Hamouda M Mousa, Abdalla Abdal-hay, Michal Bartnikowski, Ibrahim Mohamed, Ahmed Yasin, Saso Ivanovski, Chan Hee Park, and Cheol Sang Kim ACS Biomater. Sci. Eng., Just Accepted Manuscript • DOI: 10.1021/acsbiomaterials.8b00277 • Publication Date (Web): 25 Apr 2018 Downloaded from http://pubs.acs.org on April 26, 2018

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ACS Biomaterials Science & Engineering

A Multifunctional Zinc Oxide/Poly(Lactic Acid) Nanocomposite Layer Coated on Magnesium Alloys for Controlled Degradation and Antibacterial Function

Hamouda M. Mousa1,2#, Abdalla Abdal-hay2,3#, Michal Bartnikowski3, Ibrahim M.A. Mohamed1,4, Ahmed S. Yasin1, Sašo Ivanovski3 , Chan Hee Park1*, Cheol Sang Kim1*

1

Department of Bionanosystem Engineering, Division of Mechanical Design Engineering,

Chonbuk National University, Jeonju, Jeonbuk 561-756, Republic of Korea, 2

Department of Engineering Materials and Mechanical Design, Faculty of Engineering, South

Valley University, Qena 83523, Egypt, 3

School of Dentistry, the University of Queensland Oral Health Centre Herston, 288 Herston

Road, Herston QLD 4006, Australia, 4

Department of Chemistry, Faculty of Science, Sohag University, Sohag, 82524, Egypt.

# The authors are equally contributed *Corresponding authors: Tel: +82 63 270 4284, Fax: +82 63 270 2460 E-mail: [email protected] (Chan Hee Park), [email protected] (Cheol Sang Kim)

Keywords: Biodegradable magnesium alloy; biocorrosion resistance, ZnO NPs; Composite coating; Biocompatibility 1 ACS Paragon Plus Environment

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Graphical Abstract

2 ACS Paragon Plus Environment

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Abstract In the present work, magnesium (Mg) AZ31 alloy was coated with a multifunctional membrane layer composed of ZnO nanoparticles (NPs) embedded in a poly (lactic acid) (PLA) matrix. We aimed to produce a stable coating that would be used to control the degradation rate of the Mg alloy and promote a local antibacterial activity. ZnO NPs were dispersed at 5 and 10 wt. % in a PLA solution and dip-coated onto the AZ31 substrate. Surface topography, chemical composition, thickness, electrochemical corrosion performance, mass variation, antibacterial activity, adhesion performance, and cytotoxicity of an uncoated control and coated alloys were investigated. The results indicated that the incorporation of ZnO NPs at various concentrations affords a dramatic control over surface topography and degradation rates under in vitro and in vivo environmental conditions when compared to the uncoated Mg alloy control. In addition, the results confirmed that the coated layer exerts antibacterial properties and supports cell growth, indicating this system may have utility for bone tissue engineering applications.



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1. Introduction The design of biodegradable metallic implants, such as those composed of magnesium (Mg) and its alloys, has received great interest in regenerative medicine over the last few decades

1-2

.

Metallic materials are promising candidates for biomedical applications when compared with natural or synthetic polymers due to their superior mechanical properties, making them suitable for significantly load-bearing applications 3-4. Possessing mechanical properties similar to that of bone, as well as greater stiffness than ceramic biomaterials 3, Mg is considered to be a leading metallic biodegradable implant for orthopedic fixation of bone fractures and pseudarthroses (non-unions) 1. However, Mg and its alloys have low surface stability and poor corrosion resistance in aqueous environments

5-6

. Such poor corrosion resistance results in high

degradation rates in situ, leading to a loss in mechanical properties before complete healing and tissue recovery has occurred, overall impairing the healing process 7-9. Various methods have been implemented to control the high degradation rate of Mg-based implants, such as alloying, surface modification, or heat treatment

10-11

. Several researchers,

including the authors, have shown that surface modification is indeed an ideal pathway to achieving a controlled degradation rate of Mg implants, particularly throughout early time points 12-14

. Multiple surface modification methods have been assessed to enhance the surface properties

of Mg including, anodization

15-16

, macro arc oxidation

17

, electrodeposition

10

, and sol-gel

coatings 18-20. Among all of these techniques, sol-gel/organic coatings are not only a simple, costeffective strategy to suppress the early degradation of Mg, but also allow bioactive compounds or molecules to be incorporated within the deposited layers

21-22

. Several natural and synthetic

polymers and their composites have been deposited onto Mg surfaces using sol-gel coating methods 23-26. For example, Wong et al. showed that a biodegradable polymer-based coating can


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be used to control the degradation rate of Mg alloys layers do not demonstrate antibacterial properties

27

13

. Further, existing biodegradable coating

, although antibacterial activity may help to

promote tissue formation during early stages of the healing process

28

. Currently, there is an

unmet need for the development of novel biodegradable membrane coatings for Mg-based implants that are able to adequately adhere to the substrate, control the degradation rate, improve cell attachment and growth, and minimize microbial activity. Polymer/ceramic composite coatings can be designed to control the degradation of Mg and can also improve the functional performance of the material [38, 39]. For example, bioceramic nanoparticles (NPs) of hydroxyapatite (HA) or iron oxide (Fe3O4) have been incorporated within polymers coated on Mg substrates to enhance the coating stability and cell response

29-31

. Zinc

oxide (ZnO), presented herein, possesses efficient antibacterial properties and may also induce a positive effect on the attachment and growth of osteoblast-like cells 28, 32. The present work aimed to design a novel biodegradable layer composed of poly (lactic acid) (PLA) containing ZnO NPs on the surface of Mg alloy (AZ31) substrates, using a facile and cost-effective dip-coating strategy. We hypothesized that the dispersion of ZnO NPs within the PLA matrix can enhance the stability of the coating and improve the bioactivity of the construct. To investigate this, we assessed the surface topography and wettability, degradation rate in vitro and in vivo, layer adhesion, antibacterial activity, and cell attachment and proliferation in vitro. We performed these tests on a bare Mg alloy control, a PLA-only control, and two PLA/ZnO NP hybrid groups, to determine the efficacy of the proposed system.



2. Experimental section 2.1 Materials AZ31 alloy with a chemical the composition, Mg 96 %; Al 3 % and Zn 1 % were used as a substrate (Alfa Aesar, South Korea, in plate 300×300×6.35 mm). The as-received AZ31 alloy plate was cut into 12×12×6.35 mm samples using an electric discharge machine (EDM). Poly(Llactic acid) polymer (PLA, CH3O (C6H8O4)nH, Mw ~260,000 Da), dichloromethane (CH2Cl2, DCM), and a zinc oxide (ZnO) nanoparticle dispersion (

Poly(Lactic Acid) - ACS Publications

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