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)
 

Morphology of the pristine titanium surface (a), sonochemically fabricated titania mesoporous surface (TMS) top-view and crosssection (b), and top-view and cross-section of titania nanotubes (TNT) obtained by electrochemical oxidation (c). Insets show the schemes of the surface nanostructuring. Scheme showing the deposition of hydroxyapatite (HA) into the pores of the titania matrix (d-f). SEM images of the sonochemical nanostructured titanium (TMS) and TNT surfaces with chemically deposited HA: TMS-HA (g) and TNT-HA (h), respectively.
(study and images: ©Kuvyrkov 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.
 

The schematic illustration of the sonication cell (a), Schematic illustration of the surface structuring process taking place during the ultrasonic treatment of a titanium surface in aqueous alkaline solution(b) and formed surface (c), photo of titanium implants (d): the greenish one (the left sample in the hand) is implant after ultrasonic treatment, the yellowish one (the sample is situated on right) is non-modified implant.
(study and images: ©Kuvyrkov et al., 2020)

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.

Dizayn, ishlab chiqarish va konsalting – Germaniyada ishlab chiqarilgan sifat

Hielscher ultrasonikatorlari eng yuqori sifat va dizayn standartlari bilan mashhur. Mustahkamlik va qulay foydalanish ultratovush qurilmalarimizni sanoat ob'ektlariga silliq integratsiya qilish imkonini beradi. Qo'pol sharoitlar va talabchan muhit Hielscher ultrasonikatorlari tomonidan osonlik bilan hal qilinadi.

Hielscher Ultrasonics ISO sertifikatiga ega kompaniya bo'lib, eng zamonaviy texnologiya va foydalanuvchilarga qulaylik bilan ajralib turadigan yuqori samarali ultratovush apparatlariga alohida e'tibor beradi. Albatta, Hielscher ultrasonikatorlari Idoralar talablariga javob beradi va UL, CSA va RoHs talablariga javob beradi.

The XRD patterns of titania coating fabricated by thermal treatment of polished titanium (a) and sonochemically treated polished titanium (b); SEM images of polished titanium surface (c) and sonochemically generated mesoporous titanium dioxide surface (d). Sonication was performed using the sonicator UIP1000hdT.
(study and images: ©Kuvyrkov et al., 2018)