Sonochemically Nanostructured Implants Improving Osseointegration
Implants, orthopedic prostheses and dental implants are made mainly from titanium and alloys. Sonication is used to create nanostructured surfaces on metallic implants. Ultrasonic nanostructuring allows to modify metallic surfaces generating uniformly distributed nano-sized patterns on implant surfaces. These nanostructured metallic implants show a significantly improved tissue growth and osseointegration leading to improved clinical success rates.
Ultrasonically Nanostructured Implants for Improved Osseointegration
The utilization of metals, including titanium and alloys, is prevalent in the fabrication of orthopedic and dental implants due to their favourable surface properties, enabling the establishment of a biocompatible interface with peri-implant tissues. To optimize the performance of these implants, strategies have been developed to modify the nature of this interface by implementing nanoscale alterations on the surface. Such modifications exert a notable influence on critical aspects, including protein adsorption, interactions between cells and the implant surface (cell-substrate interactions), and the subsequent development of surrounding tissue. By precisely engineering these nanometer-level changes, scientists aim to enhance the biointegration and overall efficacy of implants, leading to improved clinical outcomes in the field of implantology.
Protocol for Ultrasonic Nanostructuring of Titanium Implants
Several research studies have demonstrated the simple, yet high effective nanostructuring of titanium and alloy surfaces using high-intensity ultrasound. The sonochemical treatment (i.e. ultrasound treatment) leads to the formation of a rough titania layer of sponge-like structure, which shows significantly enhances cell proliferation.
Structuring of titanium surface via sonochemical treatment: The titanium samples of 20 × 20 × 0.5 mm were previously polished and washed with deionized water, acetone, and ethanol consecutively to eliminate any contaminants. Afterward, titanium samples were ultrasonically treated in 5 m NaOH solution using Hielscher ultrasonicator UIP1000hd operated at 20 kHz (see picture left). The sonicator was equipped with the sonotrode BS2d22 (surface area of the tip 3.8 cm2) and the booster B4-1.4, magnifying the working amplitude 1.4 times. The mechanical amplitude was ≈81 μm. The generated intensity was of 200 W cm−2. The maximum power input was 760 W resulting from the multiplication of the intensity with the frontal area (with 3.8 cm2) of the used sonotrode BS2d22. Titanium samples were fixed in a homemade Teflon holder and treated for 5 min.
(cf. Ulasevich et al., 2020)
Mechanism of Ultrasonic Nanostructuring of Metal Surfaces
The ultrasonic treatment of metal surfaces leads to mechanical etching of titanium surfaces which causes the formation of a mesoporous structure on titanium.
The mechanism of the ultrasonic mechanism is based on acoustic cavitation, which occurs when low-frequency, high-intensity ultrasound waves are coupled into a liquid. When high-power ultrasound travels through a liquid, alternating high-pressure / low-pressure cycles are generated. During the low-pressure cycles minute vacuum bubbles, so-called cavitation bubbles arise in the liquid. These cavitation bubbles grow over several pressure cycles until they cannot absorb any further energy. At this point of maximum bubble growth, the cavitation bubble implodes with a violent burst and creates a highly energy-dense micro-environment. The energy-dense field of acoustic/ultrasonic cavitation is characterized by high pressure and temperature differentials exhibiting pressures of up to 2,000atm and temperatures of approx. 5000 K, high-speed liquids jets with velocities of up 280m/sec and shockwaves. When such cavitation occurs near a metallic surface not only mechanical forces but also chemical reactions occur.
In these conditions, redox reactions take place leading to oxidative reactions and titania layer formation. Besides generating the reactive oxygen species (ROS) that oxidized the titanium surface, ultrasonically generated oxidation-reduction reactions provide effective surface etching that result in obtaining the titanium dioxide layer of 1 μm thick. This means, titanium dioxide dissolves partially in alkaline solution generating the pores distributed disorderly.
The sonochemical method offers a fast and versatile for the fabrication of nanostructured materials, both inorganic and organic, that are often unachievable via conventional methods. The major advantage of this technique is that the propagation of cavitation generates large local temperature gradients in solids, resulting in materials with a porous layer and disordered nanostructures at room conditions. Additionally, the external ultrasound irradiation can be used to trigger the release of encapsulated biomolecules through pores in nanostructured coating.
High-Performance Sonicators for Nanostructuring Metallic Implant Surfaces
Hielscher Ultrasonics offers the full range of sonicators for nano-applications such as the nanostructuring of metallic surfaces (e.g. titanium and alloys). Depending on the the material, surface area and production throughput of implants, Hielscher offers you the ideal sonicator and sonotrode (probe) for you nano-structuring application.
One of the main advantages of Hielscher sonicators is the precise amplitude control and the capability to deliver very high amplitudes in continuous 24/7 operation. The amplitude, which is the displacement of the ultrasonic probe, is responsible for the sonication intensity) and therefore a crucial parameter of reliable and effective ultrasonic treatment.
- high efficiency
- state-of-the-art technology
- reliability & robustness
- adjustable, precise process control
- batch & inline
- for any volume
- intelligent software
- smart features (e.g., programmable, data protocolling, remote control)
- easy and safe to operate
- low maintenance
- CIP (clean-in-place)
Design, Manufacturing and Consulting – Quality Made in Germany
Hielscher ultrasonicators are well-known for their highest quality and design standards. Robustness and easy operation allow the smooth integration of our ultrasonicators into industrial facilities. Rough conditions and demanding environments are easily handled by Hielscher ultrasonicators.
Hielscher Ultrasonics is an ISO certified company and put special emphasis on high-performance ultrasonicators featuring state-of-the-art technology and user-friendliness. Of course, Hielscher ultrasonicators are CE compliant and meet the requirements of UL, CSA and RoHs.
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Literature / References
- Kuvyrkou, Yauheni; Brezhneva, Nadzeya; Skorb, Ekaterina; Ulasevich, Sviatlana (2021): The influence of the morphology of titania and hydroxyapatite on the proliferation and osteogenic differentiation of human mesenchymal stem cells. RSC Advances 11, 2021. 3843-3853.
- Ulasevich, Sviatlana; Ryzhkov, Nikolay; Andreeva, Daria; Özden, Dilek; Piskin, Erhan; Skorb, Ekaterina (2020): Light-to-Heat Photothermal Dynamic Properties of Polypyrrole-Based Coating for Regenerative Therapy and Lab-on-a-Chip Applications. Advanced Materials Interfaces 7, 2020.
- Kuvyrkov, Evgeny; Brezhneva, Nadezhda; Ulasevich, Sviatlana; Skorb, Ekaterina (2018): Sonochemical nanostructuring of titanium for regulation of human mesenchymal stem cells behavior for implant development. Ultrasonics Sonochemistry 52, 2018.
Facts Worth Knowing
Osteoinductivity or osteogenic property refers to the intrinsic capability of a material to stimulate the formation of new bone tissue either de novo (from the beginning) or ectopically (in non-bone-forming sites). This property is of paramount importance in the field of bone tissue engineering and regenerative medicine. Osteoinductive materials possess specific biological signals or growth factors that initiate a cascade of cellular events, leading to the recruitment and differentiation of stem cells into osteoblasts, the cells responsible for bone formation. This phenomenon allows for the creation of new bone in areas where bone regeneration is required, such as large bone defects or non-union fractures. The ability to induce bone formation de novo or in non-bone-forming sites holds significant therapeutic potential for the development of innovative approaches to treat skeletal disorders and enhance bone repair processes. Understanding and harnessing the mechanisms underlying osteoinductivity can contribute to the advancement of effective bone graft substitutes and implant materials that promote successful bone regeneration.