Effects of Titanium Implant Surface Topology on Bone Cell Attachment and Proliferation in vitro

Alkali-treated titanium dioxide promotes formation of proteoglycan layer and altered calcification and immunotolerance capacity in bone marrow stem cell

Introduction

In this study, we report that a proteoglycans (PGs)-layer between the bone and titanium dioxide (TiO2) surface after osseointegration improved the calcification capacity and immunotolerance of human bone marrow mesenchymal stem cells (hBMSCs) on TiO2. Alkaline treatment of TiO2 is a method for promoting osteogenesis in hBMSCs. We hypothesized that promotion of osteogenesis due to alkaline treatment was caused by changing PGs-layer on TiO2.

Objective

This study aimed to analyze whether alkaline treatment of TiO2 affects PGs-layer formation and immunotolerance in hBMSCs.

Methods

The topology and wettability of the alkaline-treated titanium (Ti-Al) and unprocessed titanium (Ti-MS) surfaces were characterized. Initial cell attachment, cell proliferation, calcification capacity, alkaline phosphatase activity, PGs-layer formation, PGs function, and the expression of osteogenic and immunotolerance-related genes were analyzed. The conditioned medium (CM) from hBMSCs grown on Ti-Al and Ti-MS was added to macrophages (hMps) and Jurkat cells, and immunotolerance gene expression in these cells was analyzed.

Results

hBMSCs cultured on Ti-Al showed increased initial cell attachment, cell proliferation, PG-layer formation, and osteogenic capacity compared with hBMSCs on Ti-MS. Gene expression of indoleamine 2,3-dioxygenase (IDO) in the hBMSCs cultured on Ti-Al was higher than that in the hBMSCs on Ti-MS. CM from hBMSCs did not affect markers of M1 and M2 macrophages in hMps. CM from hBMSCs cultured on Ti-Al altered the gene expression of Foxp3 in Jurkat cells compared to that of CM from hBMSCs on Ti-MS.

Significance

These results suggest that alkaline treatment of TiO2 altered PGs-layer formation, and changed the osteogenesis and immunotolerance of hBMSCs.

Bioglass and Vitamin D3 Coatings for Titanium Implants: Osseointegration and Corrosion Protection

The use of MAPLE synthesized thin films based on BG and VD3 for improving the osseointegration and corrosion protection of Ti-like implant surfaces is reported. The distribution of chemical elements and functional groups was shown by FTIR spectrometry; the stoichiometry and chemical functional integrity of thin films after MAPLE deposition was preserved, optimal results being revealed especially for the BG+VD3_025 samples. The morphology and topography were examined by SEM and AFM, and revealed surfaces with many irregularities, favoring a good adhesion of cells. The thin films' cytotoxicity and biocompatibility were evaluated in vitro at the morphological, biochemical, and molecular level. Following incubation with HDF cells, BG57+VD3_ 025 thin films showed the best degree of biocompatibility, as illustrated by the viability assay values. According to the LDH investigation, all tested samples had higher values compared to the unstimulated cells. The evaluation of cell morphology was performed by fluorescence microscopy following cultivation of HDF cells on the obtained thin films. The cultivation of HDF's on the thin films did not induce major cellular changes. Cells cultured on the BG57+VD3_025 sample had similar morphology to that of unstimulated control cells. The inflammatory profile of human cells cultured on thin films obtained by MAPLE was analyzed by the ELISA technique. It was observed that the thin films did not change the pro- and anti-inflammatory profile of the HDF cells, the IL-6 and IL-10 levels being similar to those of the control sample. The wettability of the MAPLE thin films was investigated by the sessile drop method. A contact angle of 54.65° was measured for the sample coated with BG57+VD3_025. Electrochemical impedance spectroscopy gave a valuable insight into the electrochemical reactions occurring on the surface.

Comparative study in vivo of the osseointegration of 3D-printed and plasma-coated titanium implants

BACKGROUND

Total hip arthroplasty is a common surgical treatment for elderly patients with osteoporosis, particularly in postmenopausal women. In such cases, highly porous acetabular components are a favorable option in achieving osseointegration. However, further discussion is needed if use of such acetabular components is justified under the condition of normal bone mass.

AIM

To determine the features of osseointegration of two different types of titanium implants [3-dimensional (3D)-printed and plasma-coated titanium implants] in bone tissue of a distal metaphysis in a rat femur model.

METHODS

This study was performed on 20 white male laboratory rats weighing 300-350 g aged 6 mo. Rats were divided into two groups of 10 animals, which had two different types of implants were inserted into a hole defect (2 × 3 mm) in the distal metaphysis of the femur: Group I: 3D-printed titanium implant (highly porous); Group II: Plasma-coated titanium implant. After 45 and 90 d following surgery, the rats were sacrificed, and their implanted femurs were extracted for histological examination. The relative perimeter (%) of bone trabeculae [bone-implant contact (BIC%)] and bone marrow surrounding the titanium implants was measured.

RESULTS

Trabecular bone tissue was formed on the 45th day after implantation around the implants regardless of their type. 45 d after surgery, group I (3D-printed titanium implant) and group II (plasma-coated titanium implant) did not differ in BIC% (83.51 ± 8.5 vs 84.12 ± 1 .73; P = 0.838). After 90 d, the BIC% was higher in group I (87.04 ± 6.99 vs 81.24 ± 7.62; P = 0.049), compared to group II. The relative perimeter of the bone marrow after 45 d did not differ between groups and was 16.49% ± 8.58% for group I, and 15.88% ± 1.73% for group II. Futhermore, after 90 d, in group I the relative perimeter of bone marrow was 1.4 times smaller (12.96 ± 6.99 vs 18.76 ± 7.62; P = 0.049) compared to the relative perimeter of bone marrow in group II.

CONCLUSION

The use of a highly porous titanium implant, manufactured with 3D printing, for acetabular components provides increased osseointegration compared to a plasma-coated titanium implant.

Biological Activity and Thrombogenic Properties of Oxide Nanotubes on the Ti-13Nb-13Zr Biomedical Alloy

The success of implant treatment is dependent on the osseointegration of the implant. The main goal of this work was to improve the biofunctionality of the Ti-13Nb-13Zr implant alloy by the production of oxide nanotubes (ONTs) layers for better anchoring in the bone and use as an intelligent carrier in drug delivery systems. Anodization of the Ti-13Nb-13Zr alloy was carried out in 0.5% HF, 1 M (NH₄)₂SO₄ + 2% NH₄F, and 1 M ethylene glycol + 4 wt.% NH₄F electrolytes. Physicochemical characteristics of ONTs were performed by high-resolution electron microscopy (HREM), X-ray photoelectron spectroscopy (XPS), and scanning Kelvin probe (SKP). Water contact angle studies were conducted using the sitting airdrop method. In vitro biological properties and release kinetics of ibuprofen were investigated. The results of TEM and XPS studies confirmed the formation of the single-walled ONTs of three generations on the bi-phase (α + β) Ti-13Nb-13Zr alloy. The ONTs were composed of oxides of the alloying elements. The proposed surface modification method ensured good hemolytic properties, no cytotoxity for L-929 mouse cells, good adhesion, increased surface wettability, and improved athrombogenic properties of the Ti-13Nb-13Zr alloy. Nanotubular surfaces allowed ibuprofen to be released from the polymer matrix according to the Gallagher-Corrigan model.

[Physiological reactions in the interface between cementless implants and bone]

BACKGROUND

Surgical treatment of patients with osteoarthritis of the hip and persisting symptoms under conservative therapy has become increasingly important against the background of an aging population.

OBJECTIVES

What are the physiological reactions in the interface between cementless implants and bone?

METHODS

The literature is reviewed, expert opinions and animal models are analyzed and discussed.

RESULTS

Surface coating of implants with hydroxyapatite or titanium can have positive effects on osteointegration. Additional local application of mediators might be beneficial for osteointegration in the future.

CONCLUSION

Early peri-implant bone healing directly after implantation and late remodeling of the bone-implant interface are essential for secondary implant stability.

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites

Nanocrystalline calcium phosphate (CP) bioceramic coatings and their combination with biopolymers are innovative types of resorbable coatings for load-bearing implants that can promote the integration of metallic implants into human bodies. The nanocrystalline, amorphous CP particles are an advantageous form of the various calcium phosphate phases since they have a faster dissolution rate than that of crystalline hydroxyapatite. Owing to the biomineral additions (Mg, Zn, Sr) in optimized concentrations, the base CP particles became more similar to the mineral phase in human bones (dCP). The effect of biomineral addition into the CaP phases was thoroughly studied. The results showed that the shape, morphology, and amorphous characteristic slightly changed in the case of biomineral addition in low concentrations. The optimized dCP particles were then incorporated into a chosen polycaprolactone (PCL) biopolymer matrix. Very thin, non-continuous, rough layers were formed on the surface of implant substrates via the spin coating method. The SEM elemental mapping proved the perfect incorporation and distribution of dCP particles into the polymer matrix. The bioresorption rate of thin films was followed by corrosion measurements over a long period of time. The corrosion results indicated a faster dissolution rate for the dCP-PCL composite compared to the dCP and CP powder layers.

A Review on Stimuli-Actuated 3D Micro/Nanostructures for Tissue Engineering and the Potential of Laser-Direct Writing via Two-Photon Polymerization for Structure Fabrication

In this review, we present the most recent and relevant research that has been done regarding the fabrication of 3D micro/nanostructures for tissue engineering applications. First, we make an overview of 3D micro/nanostructures that act as backbone constructs where the seeded cells can attach, proliferate and differentiate towards the formation of new tissue. Then, we describe the fabrication of 3D micro/nanostructures that are able to control the cellular processes leading to faster tissue regeneration, by actuation using topographical, mechanical, chemical, electric or magnetic stimuli. An in-depth analysis of the actuation of the 3D micro/nanostructures using each of the above-mentioned stimuli for controlling the behavior of the seeded cells is provided. For each type of stimulus, a particular recent application is presented and discussed, such as controlling the cell proliferation and avoiding the formation of a necrotic core (topographic stimulation), controlling the cell adhesion (nanostructuring), supporting the cell differentiation via nuclei deformation (mechanical stimulation), improving the osteogenesis (chemical and magnetic stimulation), controlled drug-delivery systems (electric stimulation) and fastening tissue formation (magnetic stimulation). The existing techniques used for the fabrication of such stimuli-actuated 3D micro/nanostructures, are briefly summarized. Special attention is dedicated to structures' fabrication using laser-assisted technologies. The performances of stimuli-actuated 3D micro/nanostructures fabricated by laser-direct writing via two-photon polymerization are particularly emphasized.

Kappa-carrageenan-Functionalization of octacalcium phosphate-coated titanium Discs enhances pre-osteoblast behavior and osteogenic differentiation

Bioactive coatings are promising for improving osseointegration and the long-term success of titanium dental or orthopaedic implants. Biomimetic octacalcium phosphate (OCP) coating can be used as a carrier for osteoinductive agents. κ-Carrageenan, a highly hydrophilic and biocompatible seaweed-derived sulfated-polysaccharide, promotes pre-osteoblast activity required for bone regeneration. Whether κ-carrageenan can functionalize OCP-coating to enhance osseointegration of titanium implants is unclear. This study aimed to analyze carrageenan-functionalized biomimetic OCP-coated titanium structure, and effects of carrageenan functionalization on pre-osteoblast behavior and osteogenic differentiation. Titanium discs were coated with OCP/κ-carrageenan at 0.125-2 mg/ml OCP solution, and physicochemical and biological properties were investigated. κ-Carrageenan (2 mg/ml) in the OCP coating of titanium discs decreased the pore size in the sheet-like OCP crystal by 41.32%. None of the κ-carrageenan concentrations tested in the OCP-coating did affect hydrophilicity. However, κ-carrageenan (2 mg/ml) increased (1.26-fold) MC3T3-E1 pre-osteoblast spreading at 1 h i.e., κ-Carrageenan in the OCP-coating increased pre-osteoblast proliferation (max. 1.92-fold at 2 mg/ml, day 1), metabolic activity (max. 1.50-fold at 2 mg/ml, day 3), and alkaline phosphatase protein (max. 4.21-fold at 2 mg/ml, day 3), as well as matrix mineralization (max. 5.45-fold at 2 mg/ml, day 21). κ-Carrageenan (2 mg/ml) in the OCP-coating increased gene expression of Mepe (4.93-fold) at day 14, and Runx2 (2.94-fold), Opn (3.59-fold), Fgf2 (3.47-fold), Ocn (3.88-fold), and Dmp1 (4.59-fold) at day 21 in pre-osteoblasts. In conclusion, κ-carrageenan modified the morphology and microstructure of OCP-coating on titanium discs, and enhanced pre-osteoblast metabolic activity, proliferation, and osteogenic differentiation. This suggests that κ-carrageenan-functionalized OCP coating may be promising for in vivo improvement of titanium implant osseointegration.