Endothelial cell growth on silicon modified hydrogenated amorphous carbon thin films

An updated review and recent advancements in carbon-based bioactive coatings for dental implant applications

BACKGROUND

Surface coating of dental implants with a bioactive biomaterial is one of the distinguished approaches to improve the osseointegration potential, antibacterial properties, durability, and clinical success rate of dental implants. Carbon-based bioactive coatings, a unique class of biomaterial that possesses excellent mechanical properties, high chemical and thermal stability, osteoconductivity, corrosion resistance, and biocompatibility, have been utilized successfully for this purpose.

AIM

This review aims to present a comprehensive overview of the structure, properties, coating techniques, and application of the various carbon-based coatings for dental implant applicationswith a particular focuson Carbon-based nanomaterial (CNMs), which is an advanced class of biomaterials.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Available articles on carbon coatings for dental implants were reviewed using PubMed, Science Direct, and Google Scholar resources. Carbon-based coatings are non-cytotoxic, highly biocompatible, chemically inert, and osteoconductive, which allows the bone cells to come into close contact with the implant surface and prevents bacterial attachment and growth. Current research and advancements are now more focused on carbon-based nanomaterial (CNMs), as this emerging class of biomaterial possesses the advantage of both nanotechnology and carbon and aligns closely with ideal coating material characteristics. Carbon nanotubes, graphene, and its derivatives have received the most attention for dental implant coating. Various coating techniques are available for carbon-based materials, chosen according to substrate type, application requirements, and desired coating thickness. Vapor deposition technique, plasma spraying, laser deposition, and thermal spraying techniques are most commonly employed to coat the carbon structures on the implant surface. Longer duration trials and monitoring are required to ascertain the role of carbon-based bioactive coating for dental implant applications.

Preparation and Performance Study of Si-DLC Based on Ion Deposition of Different Multiple Gradient Transition Layers

In order to improve the lower adhesion strength of Si-DLC coatings to the substrate and enhance its wear resistance, Si-DLC coatings with different transition layers (AlTiSiN, AlCrN and AlTiCrN) were prepared on 304 austenitic stainless steel substrates using multi-arc ion plating technique. The effects of different transition layers on the properties of Si-DLC were characterized by scanning electron microscopy, X-ray diffractometer, nanoindentation, confocal microscopy, Rockwell hardness tester, Raman test and wear test to find the optimal Si-DLC transition layer. The results show that the Si-DLC coating with AlTiSiN as the transition layer has an ID/IG of 0.71, the highest hardness of 26.7 Gpa, low surface roughness, the highest compressive stress, the best bond strength and the best wear resistance.

Barrier Diamond-like Carbon Coatings on Polydimethylsiloxane Substrate

The plasma modification of polydimethylsiloxane (PDMS) substrates is one way to change their surface geometry, which enables the formation of wrinkles. However, these changes are very often accompanied by the process of restoring the hydrophobic properties of the modified material. In this work, the RF PACVD device (radio frequency plasma-assisted chemical vapor deposition) was used, with which the plasma treatment of PDMS substrates was carried out in argon, nitrogen, oxygen, and methane atmospheres at variable negative biases ranging from 100 V to 500 V. The obtained results show the stability of contact angles for deionized water only in the case of surfaces modified by diamond-like carbon (DLC) coatings. The influence of the applied production conditions on the thickness (between 10 and 30 nm) and chemical structure (ID/IG between 0.41 and 0.8) of DLC coatings is discussed. In the case of plasma treatments with other gases introduced into the working chamber, the phenomenon of changing from hydrophilic to hydrophobic properties after the modification processes was observed. The presented results confirm the barrier nature of the DLC coatings produced on the PDMS substrate.

Surface characterization and biological assessment of corrosion-resistant a-C:H:SiOx PACVD coating for Ti-6Al-4V alloy

The paper focuses on the SiO_x-doped amorphous hydrocarbon (a-C:H:SiO_x) coating on the titanium (Ti-6Al-4V) alloy substrate obtained by plasma-assisted chemical vapor deposition (PACVD) in a mixture of argon gas and polyphenylmethylsiloxane vapor using a bipolar substrate bias. It is shown that the a-C:H:SiO_x coating deposition results in the formation of a negative surface potential important for application of this coating for medical implants. The a-C:H:SiO_x coatings improve the corrosion resistance of Ti alloy to 0.5 M NaCl solution and phosphate-buffered saline. In particular, the corrosion current density of the a-C:H:SiO_x-coated sample in a 0.5 M NaCl solution at 22 °C decreases from 1∙10^-8 to 1.7∙10^-10 A/cm², that reduces the corrosion rate from 9∙10^-5 to 15∙10^-7 mm/year. The a-C:H:SiO_x coating facilitates the surface endothelization of an implant located in the thoracic aorta of a mini pig, and reduces the risk of thrombosis and implant failure. This effect can be explained by the ability of the a-C:H:SiO_x coating ability to reduce in vitro a 24-hour secretion of pro-inflammatory interleukins (IL-6, IL-12(p70), IL-15, and IL-17) and cytokines (IFN-g and TNF-a) by blood mononuclear cells (MNCs) and elevates the concentration of anti-inflammatory interleukin IL-1Ra. In vitro analysis shows no cytotoxicity of the a-C:H:SiO_x coating for the human blood MNCs, suggesting a promising PACVD on Ti alloys for cardiovascular implants, including pumps for mechanical heart support systems.

A preliminary experience with a new intramedullary nail for trochanteric fractures

Background and aim of the work:

The worldwide incidence of fractures of the proximal end of the femur is increasing as the average age of the population rises. The current surgical gold treatment standard is intramedullary nail fixation. The Authors present their experience with the D-Nail system for intertrochanteric femur fractures.

Methods:

From January 1st to February 21st 2020 (breakout of COVID-19 pandemic) 34 patients were treated with the D-Nail system: 11 with basicervical fractures, 16 with intertrochanteric stable fractures and 7 with intertrochanteric unstable fractures. In 11 cases, a single cephalic screw was used; in 23 cases, two of them were used. Distal locking was executed in 7 patients. Follow-up time ranged from 2 to 3 months.

Results:

None of the reported intra- or post-operative complication was linked to the fixation device or the surgical technique. Patients were monitored with clinical and radiological checkups using modified Harris Hip Score to accurately evaluate the fluctuations in the rehabilitation period.

Conclusion:

The main advantages of this synthesis device are the proximal hole’s peculiar shape, which allows the possibility to position one or two cephalic screws on the same nail, and the silicon coating, which provides numerous biological advantages. Distal locking was executed in selected cases only, based on fracture type. Optimum treatment involves rapid execution of surgery, minimal trauma during surgery, maximum mechanical stability, and rapid weight-bearing. Although our case number is small and follow-up time brief, our results are encouraging. (www.actabiomedica.it)

Surface Characteristics and Biological Evaluation of Si-DLC Coatings Fabricated Using Magnetron Sputtering Method on Ti6Al7Nb Substrate

Diamond-like carbon (DLC) coatings are well known as protective coatings for biomedical applications. Furthermore, the incorporation of different elements, such as silicon (Si), in the carbon matrix changes the bio-functionality of the DLC coatings. This has also been proven by the results obtained in this work. The Si-DLC coatings were deposited on the Ti6Al7Nb alloy, which is commonly used in clinical practice, using the magnetron sputtering method. According to the X-ray photoelectron spectroscopy (XPS) analysis, the content of silicon in the examined coatings varied from ~2 at.% up to ~22 at.%. Since the surface characteristics are key factors influencing the cell response, the results of the cells’ proliferation and viability assays (live/dead and XTT (colorimetric assays using tetrazolium salt)) were correlated with the surface properties. The surface free energy (SFE) measurements, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the polarity and wettability of the surfaces examined increase with increasing Si concentration, and therefore the adhesion and proliferation of cells was enhanced. The results obtained revealed that the biocompatibility of Si-doped DLC coatings, regardless of the Si content, remains at a very high level (the observed viability of endothelial cells is above 70%).

In Vitro Study of a Superhydrophilic Thin Film Nitinol Endograft that is Electrostatically Endothelialized in the Catheter Prior to the Endovascular Procedure

Electrostatic endothelial cell seeding has evolved as an exceptional technique to improve the efficiency of cell seeding in terms of frequency of attached cells and the amount of cell adhesion for the treatment of vascular diseases. In the recent times, both untreated and superhydrophilic thin film nitinol (TFN) have exhibited strong prospects as substrates for creation of small-diameter endovascular grafts due to their hallmark properties of superelasticity, ultra low-profile character, and grown hemocompatible oxide layer with the presence of a uniform endothelial layer on the surface. The purpose of the current study is to understand the effects of endothelial cell seeding parameters (i.e., applied voltage, incubation time, substrate chemistry, and cell suspension solution) to investigate the cell seeding phenomenon and to improve the cell adhesion and growth on the TFN surface under electrostatic transplantation. Both parallel plate and cylindrical capacitor models were used along with the Taguchi Design of Experiment (DOE) methods to design in vitro test parameters. A novel in vitro system for a cylindrical capacitor model was created using a micro flow pump, micro incubation system, and silicone tubings. The augmented endothelialization on thin film nitinol was developed to determine the effect of cell seeding and deployed in a 6 Fr intravascular catheter setup. Cell viability along with morphology and proliferation of adhered cells were evaluated using fluorescent and scanning electron microscopy. Our results demonstrated that the maximum number of cells attached on STFN in the catheter was observed in 5 V with the 2 h exposure of in the cell culture medium (CCM) solution. The condition showed 5 V voltage with 0.68 × 10^-6 µC electrostatic charge and 5.11 V·mm^-1 electric field. Our findings have first demonstrated that the electrostatic endothelialization on the superhydrophilic thin film nitinol endograft within the catheter prior to the endovascular procedure could enhance the biocompatibility for low-profile endovascular applications.

Preparation of chitosan films using different neutralizing solutions to improve endothelial cell compatibility

The development of chitosan-based constructs for application in large-size defects or highly vascularized tissues is still a challenging issue. The poor endothelial cell compatibility of chitosan hinders the colonization of vascular endothelial cells in the chitosan-based constructs, and retards the establishment of a functional microvascular network following implantation. The aim of the present study is to prepare chitosan films with different neutralization methods to improve their endothelial cell compatibility. Chitosan salt films were neutralized with either sodium hydroxide (NaOH) aqueous solution, NaOH ethanol solution, or ethanol solution without NaOH. The physicochemical properties and endothelial cell compatibility of the chitosan films were investigated. Results indicated that neutralization with different solutions affected the surface chemistry, swelling ratio, crystalline conformation, nanotopography, and mechanical properties of the chitosan films. The NaOH ethanol solution-neutralized chitosan film (Chi-NaOH/EtOH film) displayed a nanofiber-dominant surface, while the NaOH aqueous solution-neutralized film (Chi-NaOH/H(2)O film) and the ethanol solution-neutralized film (Chi-EtOH film) displayed nanoparticle-dominant surfaces. Moreover, the Chi-NaOH/EtOH films exhibited a higher stiffness as compared to the Chi-NaOH/H(2)O and Chi-EtOH films. Endothelial cell compatibility of the chitosan films was evaluated with a human microvascular endothelial cell line, HMEC-1. Compared with the Chi-NaOH/H(2)O and Chi-EtOH films, HMECs cultured on the Chi-NaOH/EtOH films fully spread and exhibited significantly higher levels of adhesion and proliferation, with retention of the endothelial phenotype and function. Our findings suggest that the surface nanotopography and mechanical properties contribute to determining the endothelial cell compatibility of chitosan films. The nature of the neutralizing solutions can affect the physicochemical properties and endothelial cell compatibility of chitosan films. Therefore, selection of suitable neutralization methods is highly important for the application of chitosan in tissue engineering.

Preparation and characterization of chitosan-heparin composite matrices for blood contacting tissue engineering

Chitosan has been widely used for biomaterial scaffolds in tissue engineering because of its good mechanical properties and cytocompatibility. However, the poor blood compatibility of chitosan has greatly limited its biomedical utilization, especially for blood contacting tissue engineering. In this study, we exploited a polymer blending procedure to heparinize the chitosan material under simple and mild conditions to improve its antithrombogenic property. By an optimized procedure, a macroscopically homogeneous chitosan-heparin (Chi-Hep) blended suspension was obtained, with which Chi-Hep composite films and porous scaffolds were fabricated. X-ray photoelectron spectroscopy and sulfur elemental analysis confirmed the successful immobilization of heparin in the composite matrices (i.e. films and porous scaffolds). Toluidine blue staining indicated that heparin was distributed homogeneously in the composite matrices. Only a small amount of heparin was released from the matrices during incubation in normal saline for 10 days. The composite matrices showed improved blood compatibility, as well as good mechanical properties and endothelial cell compatibility. These results suggest that the Chi-Hep composite matrices are promising candidates for blood contacting tissue engineering.