Novel hydroxyapatite–graphene nanosheets composite coatings deposited by vacuum cold spraying for biomedical applications

Yi Liu， Jing Huang ，Hua Li 12/10/2013

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Outline

•Background

•Experimental Procedures

•Results & Discussion

•Conclusions

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Thermal spraying

3 R.S.Lima, B.R.Marple, J. Therm. Spray Techn. 2007, 16:40-63

Particle velocity

Deposition

Coating manufacturing Rust cleaning

Before After

Shot Peening Cutting

Armor-piercing

1200-1500m/s ~600m/s

Vcr

High velocity particles impacting on a ductile substrate! Bonding by

intensive plastic

deformation

Characteristics of cold spray

4 H. Assadi et al. Acta Materialia 2003,51 :4379–4394

Characteristics of vacuum cold spray

The most outstanding advantages: High deposition rate (several µm/min )

Low deposition temperature

(Room temperature)

Stable chemical compositions

(a) Thick ceramic layer: over 500 µm;

(b) transparent ceramic layer:

(c) 99% at 400-900 nm;

(d) wide area coating: 200×200 mm2

Jun Akedo, J.Thermal Spray Technology, 2008, 17(2),181-198 5

Background Dental implant Hip implant Biomaterial

Market scale & Market share

6 http://www.bccresearch.com/report/HLC052.htlm

Metal implant stainless steel

Co alloy

Co alloy

Ti alloy

stainless steel

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Release of some metallic ions may cause local inflammatory !

HA-coated implant • more rapid fixation and stronger bonding between the host bone and the implant • increased uniform bone ingrowth and/or ongrowth at the bone-implant interface

biological inertness !

Why HA coated implant ?

•[1].Learmonth et al Engineering in Medicine, 220, 229 •[2].Dowson, Engineering in Medicine.215, 335 8

Background——Hydroxyapatite，HA

HA is the main mineral of which dental enamel and dentin are comprised (>97%) .

HA: Ca10( PO4)6(OH)2

Up to 60% of bone by weight is a modified form of HA

• Ceramics

– YSZ, Al2O3, ZrO2, TiO2, etc.

• Polymers

– Polyethylene, collagen, etc

• Metals

– Ti6Al4V, 316L, etc

• Others,

– CNTs, protein (e.g. gelatin), etc

Second phase reinforcement

Brittleness !!!

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• 2-dimensional hexagonal lattice of carbon

• sp2 hybridized carbon atoms

• Basis for C-60 (bucky balls), nanotubes, and graphite

• Among strongest bonds in nature

A. K. Geim, K. S. Novoselov. Nature Materials 6 183-191 (2007)

Graphene – a sheet of carbon atoms

Why graphene? Young’s modulus:~1TPa Tensile strength :~200GPa

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Why HA-graphene ?

Stress-strain plots of RG-O/ poly(vinyl alcohol) composites

TEM images of thermoplastic poly(urethane) matrix filled with graphene

Graphene nano-sheets in the SPS HA–rGO pellets

Jeffrey R. Potts, Daniel R. Dreyer, Christopher W. Bielawski , Rodney S. Ruoff. Polymer 2011, 52, 5-25.

Yi Liu,Jing Huang,Hua Li. J. Mater. Chem. B 2013,1,1826-1834

Reinforcements

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Is graphene biocompatible?

• graphene sample tested seems to be blood compatible – W. Paul, et al, Trends Biomater. Artif.

Organs, 25, 91-94 (2011)

• hMSCs grown on graphene-coated samples exhibited better viability – T.R. Nayak, et al, ACS Nano, DOI:

10.1021/nn200500h April 2011

• graphene-based nanomaterials can effectively inhibit the growth of E. coli bacteria while showing minimal cytotoxicity – W. Hu, et al, ACS Nano,4, 4317-4323

(2010)

E. coli

exposed

to GO

nanosheets

at 37 ℃ for 2 h

Biological aspects of graphene

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Nanostructuring promotes mechanical properties & biocompatibility?

Osteoblast adhesion on

nanophase HA Enhanced select protein adsorption on nanophase HA

Susmita Bose et al, Acta Biomaterialia,6,3782–3790 (2010) Webster TJ, et al, Journal of Biomedical Materials Research, 51 (3),475 – 483(2000). 13

How to retain nanostructures ? Different types of nanostructural characteristics found in the cross-section of the HA coating

HA particle formed by the agglomeration of individual nanosized HA particles

Dissolution rates in the body fluid:

ACP>TTCP> a-TCP>OHA >b-TCP>>HA

Lima, R.S.; Marple, B.R. J. Therm. Spray Techn. 2007, 16, 40-63

Decomposition

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electrophoretic deposition dip coating/sintering hot isostatic pressing

sputter coating thermal spraying (clinical applicaition)

How to retain nanostructures ?

Sun Limin et.al.J.Biomed Mater Res. 2001;58(5):570-92. 15

Characteristics of vacuum cold spray

The most outstanding advantages: High deposition rate (several µm/min )

Low deposition temperature

(Room temperature)

Stable chemical compositions

(a) Thick ceramic layer: over 500 mm;

(b) transparent ceramic layer:

(c) 99% at 400-900 nm;

(d) wide area coating: 200×200 mm2

Jun Akedo, J.Thermal Spray Technology, 2008, 17(2),181-198 16

Experimental procedures-materials TEM image of graphene AFM analyses of the synthesized graphene

TEM images of HA and HA–graphene composites powders

HA HA-0.1% graphene HA-1.0% graphene

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Experimental Procedures-apparatus

Schematic diagram of the VCS apparatus

Experimental parameters

Deposition

temperature

Pressure of

deposition

chamber (Pa)

He gas

flow

(L/min)

Size of nozzle

orifice

(mm×mm)

Scanning

speed (mm/s)

Spray

distance

(mm)

RT 100-7000 3-10 2.5×0.25 10 10

1mm thick Ti plates —— Substrates 18

Results & Discussion-Microstructure

Adhesive strength by micro-scratch tester

XRD patterns

No changes of the phases in the coatings compared to the starting feedstock!

The adhesive strength of pulsed laser deposited HA coating on Ti-based permanent implants is 10.77N.

The VCS coatings have good adhesion to the substrate! 19

Nano-structure of original powders have been completely retained in coatings !

HA HA-0.1%G HA-1.0%G Surface view of the as-deposited VCS coatings

( Ra:1.1µm ) ( Ra:1.3µm ) ( Ra:1.7µm )

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Porosity and microstructure of the VCS coatings

HA

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Porosity and microstructure of the VCS coatings

HA-1.0GN

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Addition of GN results in denser structure

TEM image

The results suggest intimate contact of GNs with the substrate.

SEM images

TEM image

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Room temperature impact consolidation (RTIC)

Deposition mechanism of VCS HA coating

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The mechanical properties of the coatings are improved by the addition of GN

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Attachment of osteoblast on the Ti, HA and HA-graphene composite coatings for 3hrs

Ti substrate

HA

After 3hrs incubation, the cell showed better stretching state on the HA-based coatings than on Ti substrate !

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HA-0.1%G

HA-1.0%G

More GNs in the HA-based coatings resulted in faster spreading of the cells ! 27

MTT results for the cells proliferated on the surfaces of the samples

Cells attached/proliferated on the surfaces of the samples after different duration of the in vitro incubation

GNs in the HA-based coatings promoted spreading and proliferation of the cells !

Proliferation of osteoblast on the Ti, HA and HA-graphene composite coatings

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HA-GN nanocomposite coatings were successfully fabricated by VCS at room temperature.

Comprehensive microstructural characterization showed that the physical characteristics of the starting feedstocks were completely inherited by the as-deposited coatings without detectable crystal grain growth or phase changes.

The GN-containing HA coatings markedly enhanced mechanical properties and attachment and proliferation of the osteoblast cells.

The fabrication of the novel HA-GN nanocomposite biomedical coatings by the VCS could open doors for processing new nanostructured biomaterials with exceptional properties.

Conclusions

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Acknowledgements This research was supported by National Natural Science Foundation of China (grant # 31271017) and 100 Talents Program of Chinese Academy of Sciences (both to H.L.). The authors thank Drs. Yuyue Wang and Zhaohui Dang from Xi’an Jiaotong University, China for their technical help in making the coatings by VCS.

Yi Liu, Zhaohui Dang, Yuyue Wang, Jing Huang, Hua Li，Hydroxyapatite/graphene-nanosheet composite coatings deposited by vacuum cold spraying for biomedical applications: inherited nanostructures and enhanced properties ,Carbon, Accepted Yi Liu, Jing Huang, Hua Li，Deposition and characterization of vacuum cold sprayed hydroxyapatite/graphene-nanosheet coatings for biomedical applications, J Therm Spray Techn , Accepted

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