RGD-modified dihydrolipoamide dehydrogenase as a molecular bridge for enhancing the adhesion of bone forming cells to titanium dioxide implant surfaces

Effect of controlled surface roughness and biomimetic coating on titanium implants adhesion to the bone: An experiment animal study

Introduction

Laser micromachining of titanium and its alloys can create micro-grooves with sizes similar to cell diameter of about 10 μm. Its coating with arginine-glycine-aspartic acid (RGD) may enhance cellular spreading and adhesion. This study aimed to evaluate the effect of laser micro-grooving and laser micro-grooving combined with RGD coating on the strength of the dental implants/bone interface using destructive mechanical pullout testing in experimental animals.

Materials and methods

In this study, the test groups consisted of 1.5-mm diameter, 5-mm long laser-grooved and laser-grooved/RGD coated titanium alloy (Ti-6Al-4 V) rods, and the control group included plain titanium alloy (Ti-6Al-4 V) rods. These rods were implanted in the mandibles of New Zealand white rabbits for 2, 4, and 6 weeks. After sacrifice, the test and control specimens were retrieved for mechanical pullout testing. The DMA 7-e was used to pull the titanium rods out of the bone, the probe position was plotted versus time graph to monitor the test progression, and the static modulus versus time graph was viewed; such graphs was then transformed into tables. The results were analyzed using the Mann-Whitney test.

Results

The laser-grooved/RGD coated rods had significantly higher pull-out strength than the laser-grooved and control rods. Additionally, the laser-grooved rods had significantly higher pull-out strength than control rods.

Conclusion

Two novel surface treatments were used: laser micro-grooving and tri peptide RGD coating, both of which had different effects on the dental implant interface. Laser grooving improved peri-implant bone healing, whereas RGD coating facilitated earlier bone-implant adhesion and better mineralization.

Roles of Dihydrolipoamide Dehydrogenase in Health and Disease

Significance: Dihydrolipoamide dehydrogenase (DLDH) is a flavin-dependent disulfide oxidoreductase. The active form of DLDH is a stable homodimer, and its deficiencies have been linked to numerous metabolic disorders. A better understanding of redox and nonredox features of DLDH may reveal druggable targets for disease interventions or preventions. Recent Advances: In this article, the authors review the different roles of DLDH in selected pathological conditions, including its deficiency in humans, its role in stroke and neuroprotection, skin photoaging, Alzheimer's disease, and DLDH as a nondehydrogenating protein, and construction of genetically modified DLDH animal models for further studying the role of DLDH in specific pathological conditions. DLDH is also vulnerable to oxidative modifications in pathological conditions. Critical Issues: Novel animal models need to be constructed using gene knockdown techniques to investigate the redox- and nonredox roles of DLDH in related metabolic diseases. Specific small-molecule DLDH inhibitors need to be discovered. The relationship between modifications of specific amino acid residues in DLDH and given pathological conditions is an interesting area that remains to be comprehensively evaluated. Future Directions: Cell-specific or tissue-specific knockdown of DLDH creating specific pathological conditions will provide more insights into the mechanisms, whereby DLDH may have therapeutic values under a variety of pathological conditions. Antioxid. Redox Signal. 39, 794-806.

Cuproptosis-a potential target for the treatment of osteoporosis

Osteoporosis is an age-related disease of bone metabolism marked by reduced bone mineral density and impaired bone strength. The disease causes the bones to weaken and break more easily. Osteoclasts participate in bone resorption more than osteoblasts participate in bone formation, disrupting bone homeostasis and leading to osteoporosis. Currently, drug therapy for osteoporosis includes calcium supplements, vitamin D, parathyroid hormone, estrogen, calcitonin, bisphosphates, and other medications. These medications are effective in treating osteoporosis but have side effects. Copper is a necessary trace element in the human body, and studies have shown that it links to the development of osteoporosis. Cuproptosis is a recently proposed new type of cell death. Copper-induced cell death regulates by lipoylated components mediated via mitochondrial ferredoxin 1; that is, copper binds directly to the lipoylated components of the tricarboxylic acid cycle, resulting in lipoylated protein accumulation and subsequent loss of iron-sulfur cluster proteins, leading to proteotoxic stress and eventually cell death. Therapeutic options for tumor disorders include targeting the intracellular toxicity of copper and cuproptosis. The hypoxic environment in bone and the metabolic pathway of glycolysis to provide energy in cells can inhibit cuproptosis, which may promote the survival and proliferation of various cells, including osteoblasts, osteoclasts, effector T cells, and macrophages, thereby mediating the osteoporosis process. As a result, our group tried to explain the relationship between the role of cuproptosis and its essential regulatory genes, as well as the pathological mechanism of osteoporosis and its effects on various cells. This study intends to investigate a new treatment approach for the clinical treatment of osteoporosis that is beneficial to the treatment of osteoporosis.

peri-implant ligament

The peri-implant ligament is formed from the interface of bone tissue, through the anchoring of proteins and the surface of the dental implant. In this sense, it is relevant to understand the extent to which this ligament is structured and biomimics the periodontal ligament functions. Aim: The goal of this scoping review is to present and analyze the peri-implant ligament composition and compare the extent to which this ligament is structured and biomimics the periodontal ligament functions. Methods: This scoping review was performed according to the Joanna Briggs Institute methodology for scoping reviews and following the Preferred Reporting Items for Systematic Reviews and Meta-analyses extension for scoping review. Two independent researchers searched Pubmed, Cochrane, Embase, Virtual Health Library, Scielo, Scopus, Web of Science, Brazilian Bibliography of Dentistry, Latin American and Caribbean Literature in Health Sciences, Digital Library of Theses and Dissertations from the University of São Paulo and Portal Capes. Studies published in English, Portuguese and Spanish, over the last 21 years (2000-2021). Results: A total of 330 titles were identified and after applying inclusion and exclusion factors, 27 studies were included in this review. All proteins were identified regarding their tissue function and classified into 6 major protein groups. After that this new protein ligament was compared with the periodontal ligament regarding its function and composition. The main proteins associated with osseointegration, and thus, with the peri-implant ligament are recognized as belonging to the periodontal ligament. Conclusion: This scoping review results suggest evidence of the composition and function of the periimplant ligament. However, variations may still exist due to the existence of several modulants of the osseointegration process.

The moonlighting activities of dihydrolipoamide dehydrogenase: Biotechnological and biomedical applications

Dihydrolipoamide dehydrogenase (DLDH) is a homodimeric flavin-dependent enzyme that catalyzes the NAD⁺ -dependent oxidation of dihydrolipoamide. The enzyme is part of several multi-enzyme complexes such as the Pyruvate Dehydrogenase system that transforms pyruvate into acetyl-co-A. Concomitantly with its redox activity, DLDH produces Reactive Oxygen Species (ROS), which are involved in cellular apoptotic processes. DLDH possesses several moonlighting functions. One of these is the capacity to adhere to metal-oxides surfaces. This was first exemplified by the presence of an exocellular form of the enzyme on the cell-wall surface of Rhodococcus ruber. This capability was evolutionarily conserved and identified in the human, mitochondrial, DLDH. The enzyme was modified with Arg-Gly-Asp (RGD) groups, which enabled its interaction with integrin-rich cancer cells followed by "integrin-assisted-endocytosis." This allowed harnessing the enzyme for cancer therapy. Combining the TiO₂ -binding property with DLDH's ROS-production, enabled us to develop several medical applications including improving oesseointegration of TiO₂ -based implants and photodynamic treatment for melanoma. The TiO₂ -binding sites of both the bacterial and human DLDH's were identified on the proteins' molecules at regions that overlap with the binding site of E3-binding protein (E3BP). This protein is essential in forming the multiunit structure of PDC. Another moonlighting activity of DLDH, which is described in this Review, is its DNA-binding capacity that may affect DNA chelation and shredding leading to apoptotic processes in living cells. The typical ROS-generation by DLDH, which occurs in association with its enzymatic activity and its implications in cancer and apoptotic cell death are also discussed.

Multifunctional natural polymer-based metallic implant surface modifications

High energy traumas could cause critical damage to bone, which will require permanent implants to recover while functionally integrating with the host bone. Critical sized bone defects necessitate the use of bioactive metallic implants. Because of bioinertness, various methods involving surface modifications such as surface treatments, the development of novel alloys, bioceramic/bioglass coatings, and biofunctional molecule grafting have been utilized to effectively integrate metallic implants with a living bone. However, the applications of these methods demonstrated a need for an interphase layer improving bone-making to overcome two major risk factors: aseptic loosening and peri-implantitis. To accomplish a biologically functional bridge with the host to prevent loosening, regenerative cues, osteoimmunomodulatory modifications, and electrochemically resistant layers against corrosion appeared as imperative reinforcements. In addition, interphases carrying antibacterial cargo were proven to be successful against peri-implantitis. In the literature, metallic implant coatings employing natural polymers as the main matrix were presented as bioactive interphases, enabling rapid, robust, and functional osseointegration with the host bone. However, a comprehensive review of natural polymer coatings, bridging and grafting on metallic implants, and their activities has not been reported. In this review, state-of-the-art studies on multifunctional natural polymer-based implant coatings effectively utilized as a bone tissue engineering (BTE) modality are depicted. Protein-based, polysaccharide-based coatings and their combinations to achieve better osseointegration via the formation of an extracellular matrix-like (ECM-like) interphase with gap filling and corrosion resistance abilities are discussed in detail. The hypotheses and results of these studies are examined and criticized, and the potential future prospects of multifunctional coatings are also proposed as final remarks.

Biomimetic titanium implant coated with extracellular matrix enhances and accelerates osteogenesis

Aim: To evaluate the biological function of titanium implants coated with cell-derived mineralized extracellular matrix, which mimics a bony microenvironment. Materials & methods: A biomimetic titanium implant was fabricated primarily by modifying the titanium surface with TiO₂ nanotubes or sand-blasted, acid-etched topography, then was coated with mineralized extracellular matrix constructed by culturing bone marrow mesenchymal stromal cells. The osteogenic ability of biomimetic titanium surface in vitro and in vivo were evaluated. Results: In vitro and in vivo studies revealed that the biomimetic titanium implant enhanced and accelerated osteogenesis of bone marrow stromal cells by increasing cell proliferation and calcium deposition. Conclusion: By combining surface topography modification with biological coating, the results provided a valuable method to produce biomimetic titanium implants with excellent osteogenic ability.

Fueling a Hot Debate on the Application of TiO2 Nanoparticles in Sunscreen

Titanium is one of the most abundant elements in the earth's crust and while there are many examples of its bioactive properties and use by living organisms, there are few studies that have probed its biochemical reactivity in physiological environments. In the cosmetic industry, TiO2 nanoparticles are widely used. They are often incorporated in sunscreens as inorganic physical sun blockers, taking advantage of their semiconducting property, which facilitates absorbing ultraviolet (UV) radiation. Sunscreens are formulated to protect human skin from the redox activity of the TiO2 nanoparticles (NPs) and are mass-marketed as safe for people and the environment. By closely examining the biological use of TiO2 and the influence of biomolecules on its stability and solubility, we reassess the reactivity of the material in the presence and absence of UV energy. We also consider the alarming impact that TiO2 NP seepage into bodies of water can cause to the environment and aquatic life, and the effect that it can have on human skin and health, in general, especially if it penetrates into the human body and the bloodstream.

Characterization of Sol-Gel Derived Calcium Hydroxyapatite Coatings Fabricated on Patterned Rough Stainless Steel Surface

Sol-gel derived calcium hydroxyapatite (Ca10(PO4)6(OH)2; CHA) thin films were deposited on stainless steel substrates with transverse and longitudinal patterned roughness employing a spin-coating technique. Each layer in the preparation of CHA multilayers was separately annealed at 850 °C in air. Fabricated CHA coatings were placed in simulated body fluid (SBF) for 2, 3, and 4 weeks and investigated after withdrawal. For the evaluation of obtained and treated with SBF coatings, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray diffraction (XRD) analysis, Raman spectroscopy, XPS spectroscopy, scanning electron microscopy (SEM) analysis, and contact angle measurements were used. The tribological properties of the CHA coatings were also investigated in this study.