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eISSN: 2576-4519

Applied Bionics and Biomechanics

Mini Review Volume 2 Issue 1

The application of nanotechnology in biomechanical systems: recent developments

Ehab Hussein Bani-Hani,1 Mamdouh El Haj assad2

1Department of Mechanical Engineering, Australian College of Kuwait, Kuwait
2Department of SREE, University of Sharjah, United Arab Emirates

Correspondence: Ehab Hussein, Department of Mechanical Engineering, School of Engineering, Australian College of Kuwait, Kuwait

Received: December 19, 2017 | Published: February 14, 2018

Citation: Bani-Hani EH, assad MEH. The application of nanotechnology in biomechanical systems: recent developments. MOJ App Bio Biomech. 2018;2(1):62–63. DOI: 10.15406/mojabb.2018.02.00046

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Abstract

Nano materials are used widely in today’s life. Engineering fields are mostly made use of such substances. In biomechanical engineering the use of nanomaterial is no that famous. Today’s studies are focusing in utilizing the Nano technology in engineering materials. However, Viscoelastic behavior has been largely ignored. In this work a mini review of current studies where nano materials is utilized in biomechanical systems is presented. For example, a characterizing the micro-mechanical viscoelastic properties of cross-linked hydrogels at typical cell length scales is presented. An advanced ceramic conversion surface engineering technology has been applied for the first time to self-drilling Ti6Al4V external fixation pins to improve their performance in terms of biomechanical, biotribological and antibacterial properties. Characterization of the ceramic conversion treated Ti pins was carried out using nano- and micro-indentation and scratching.

Results of this review show that an empirical equation describing the stress-time relation can be derived from experimental data. The use of nanomaterial helps in improving the mechanical properties of the tissues under study. The mechanical properties of Ti pins are significantly increased hardness (more than three times) and the effectively enhanced wear resistance. The maximum insertion force and temperature were reduced from 192N and 31.2°C when using the untreated pins to 182N and 26.1°C when the ceramic conversion treated pins were tested.

Keywords: nano-materials, biomechanical, viscoelastic, pins

Introduction

Nanotechnology which involves handling with materials at very small dimensions (10-9m) has wide applications in engineering branches. It can improve the physical and chemical properties of the system. Thus it has many applications such as solar desalination1 and many others. Current researches are trying to involve these substances in biomechanical engineering systems. For example one of important properties in biomechanical systems is viscoelasticity of cells that are surrounded by the extracellular matrix (ECM), which is complex network of glycosaminoglycan, proteins, and fibers2 that provide biochemical and biomechanical cues that are critical for the regulation of cell adhesion, proliferation, differentiation, morphology, and gene expression so the ECM is vital for soft tissue biomechanics. Cell response to stiffness as well has contributed to the behavior of cell mechano-transduction, designating substrate elasticity as a major determinant in the regulation of Pathophysiological cell behavior and function.3,4

Generally speaking mechanical properties should be derived in the physiological region of small deformations (e.g., the 0.01÷0.1 strain range), and measurements should be performed at physiologically relevant strain rates/frequencies (e.g., a 0.001÷0.1s-1 strain rate).5‒7 Developing biomaterials for cell culture and mechano-biology studies. To date, only a few cells (hMSCs), but decreased the size and maturity of their focal adhesions. Another example is the external fracture fixation that entails the use of percutaneously placed transosseous pins and/or wires secured to external scaffolding to provide support to a limb. These include highly comminuted fractures, open fractures, fractures associated with gross soft tissue damage. Currently, external fixation has evolved from being used as a last resort fixation method to a main technique to treat a myriad of bone and soft tissue pathologies. To ensure a solid fixation, ease of insertion and reduce risk of complications a well-designed pin is required. Stainless steel and titanium self-drilling/self-tapping Schanz pins are one of best choices.8

Austenitic stainless steel is the material selected for external fixation pins. This is attributed to the attractive combination of excellent corrosion resistance, good mechanical properties and adequate biocompatibility coupled with their outstanding formability and cost-effectiveness.9 The coming section will present the up-to-date development in the above mentioned examples.

Discussion of recent developments

Bio mechanical properties

In their work10 researchers used the nano-M to characterize the micro-mechanical viscoelastic properties of gelatin hydrogels. Gelatin is widely used as cell culture substrate because of its inherent biocompatibility and bioactivity.11 Many studies have focused on characterizing the quasi-static elastic modulus (E) of GTA-cross linked gelatin hydrogels, showing an increase in E with increasing GTA concentration.12,13 The micro-mechanical Visco elastic properties of GTA-cross linked gelatin hydrogels were characterized via nano indentation tests, relating results to the cross linker concentration.

The experimental results obtained10 were fitted to a Maxwell Standard Linear Solid model, showing that increasing GTA concentration results in increased instantaneous and equilibrium elastic moduli and in a higher characteristic relaxation time. Therefore, not only do gelatin hydrogels become stiffer with increasing cross linker concentration but there is also a concomitant change in their viscoelastic behavior towards a more elastic one. The experimental data allows the derivation of stress – time relation expressed in Eq. (1):

σ ind ( t )= ε ind . ̇ ( E 0 t+ η 1 ( 1 e E 1 η 1 t ) ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqcfaieaaaaaa aaa8qacqaHdpWCpaWaaSbaaeaapeGaamyAaiaad6gacaWGKbaapaqa baWdbmaabmaapaqaa8qacaWG0baacaGLOaGaayzkaaGaeyypa0Zdam aaxacabaWdbiabew7aL9aadaWgaaqaa8qacaWGPbGaamOBaiaadsga a8aabeaapeGaaiOlaaWdaeqabaWdbiablEWaMaaadaqadaWdaeaape GaamyraSWdamaaBaaajuaGbaqcLbmapeGaaGimaaqcfa4daeqaa8qa caWG0bGaey4kaSIaeq4TdG2damaaBaaabaqcLbmapeGaaGymaaqcfa 4daeqaa8qadaqadaWdaeaapeGaaGymaiabgkHiTiaadwgapaWaaWba aeqabaWdbiabgkHiTmaalaaapaqaa8qacaWGfbWcpaWaaSbaaKqbag aajugWa8qacaaIXaaajuaGpaqabaaabaWdbiabeE7aO9aadaWgaaqa aKqzadWdbiaaigdaaKqba+aabeaaaaWdbiaadshaaaaacaGLOaGaay zkaaaacaGLOaGaayzkaaaaaa@617F@     (1)

Eq. (1) consists of a pure spring (E0) assembled in parallel to a Maxwell arm (i.e., a spring E1 in

Series with a dashpot η1, defining a characteristic relaxation time τ 1 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqcfaieaaaaaa aaa8qacqaHepaDl8aadaWgaaqcfayaaKqzadWdbiaaigdaaKqba+aa beaaaaa@3BC8@ = η 1 E 1 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaqcfaieaaaaaa aaa8qadaWcaaWdaeaapeGaeq4TdG2cpaWaaSbaaKqbagaajugWa8qa caaIXaaajuaGpaqabaaabaWdbiaadweal8aadaWgaaqcfayaaKqzad WdbiaaigdaaKqba+aabeaaaaaaaa@4018@ .

Pin fixation

Nanotechnology showed a great improvement in the field of pin fixation.14 In coating processes it is well known that titanium and its alloys are described as poor mechanical properties in terms of low hardness and low load bearing capacity. In addition poor tribological properties in terms of low hardness, high friction and strong adhesive wear15,16 are recorded. Therefore, without strong mechanical support from the substrate, the very thin (nanometric) TiO2 films formed in air at room temperature.17 This led to the loss of the anti-bacterial property. A problem of high temperature at bone-pin surface during insertion occurs, which would cause damage to the bone and retard its healing after operation.18

Thus researchers14 report a novel approach to generate a multi-functional surface for titanium Schanz pins by converting their Ti surfaces into a TiO2 ceramic layer through thermal oxidation of Ti in an oxygen-containing atmosphere. Oxygen diffuses into the subsurface to form a hardened case which can provide a strong mechanical support to the surface TiO2 ceramic layer, thus effectively conferring a high load bearing capacity of the CCT treated Ti surfaces. Characterization of the ceramic conversion treated Ti pins was carried out using scanning electron microscope, X-ray diffraction, Glow-discharge optical emission spectroscopy, nano- and micro-indentation and scratching; the biomechanical and bio-tribological properties of the surface engineered Ti pins were evaluated by insertion into high density bone simulation material; and the antibacterial behavior was assessed with Staphylococcus aureus NCTC 6571. The experimental results have showed that the surfaces of external fixation pins were successfully converted into a TiO2 rutile supported by an oxygen hardened case with very good bonding due to the in-situ conversion nature.

Conclusion

Nano materials have strong contribution in the field of biomechanical systems. Starting from improving the physical properties such as the hardness and viscoelasticity to improve the pin fixation processes. Where the force on the pin is minimized and the temperature is reduces due to friction. This allows a long lasting of the pin. Nano- and micro-indentation and scratching are used for systematic characterization of the ceramic conversion treated Ti pins.

Acknowledgements

The author thanks National Natural Science Foundation (Grant No. 51504141) for providing the research grant.

Conflict of interest

Author declares that there is no conflict of interest.

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