Interaction of bovine serum albumin and lysozyme with stainless steel studied by time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy

Influence of bovine serum albumin on biodegradation behavior of pure Zn

Zinc is emerging as a promising biodegradable metal for temporary implant applications. In this work, we investigate the influence of bovine serum albumin (BSA)-the most abundant blood protein in simulated body fluid (SBF) on degradation of pure Zn via electrochemical measurements and long-term immersion. Electrochemical experiments indicate a decrease of the corrosion rate of bare Zn with increasing BSA concentration in solution for short-term exposures. Samples were characterized with scanning electron microscope (SEM) (including energy dispersive spectroscopy [EDS], X-ray photoelectron spectroscopy [XPS], Fourier transform infrared spectroscopy [FTIR], and time-of-flight secondary ion mass spectrometry [TOF-SIMS]) after immersion up to 21 days. Presence of BSA in the electrolyte, decrease the amount of Ca-phosphate precipitation on Zn surface. However, a more compact surface layer formed in the presence of BSA in solution. Most noteworthy, in long-term exposures, BSA enhances localized corrosion of Zn-such detrimental localized attack was not observed in BSA-free solution. We suggest that a sealed space forming between the Zn substrate and a protein adsorption layer restricts mass transport, thus triggering localized corrosion of Zn.

Corrosion Behavior and In Vitro Cytotoxicity of Ni-Ti and Stainless Steel Arch Wires Exposed to Lysozyme, Ovalbumin, and Bovine Serum Albumin

In this study, the tendency and mechanisms by which protein and mechanical loads contribute to corrosion were determined by exposing Ni-Ti and stainless steel arch wires under varying mechanical loads to artificial saliva containing different types of protein (lysozyme, ovalbumin, and bovine serum albumin). The corrosion behavior and in vitro cytotoxicity results show that exposure to both protein and mechanical stress significantly decreased the corrosion resistance of stainless steel and increased the release of toxic corrosion products. Adding protein inhibited the corrosion of Ni-Ti, but the mechanical loads counteracted this effect. Even proteins containing the same types of amino acids had different effects on the corrosion resistance of the same alloy. The effect of protein or stress, or their combination, should be considered in the application of metal medical materials.

Role of protein adsorption in the bio corrosion of metallic implants - A review

Implants are exposed to a complex physiological environment that contains various organic compounds, especially proteins. The adsorption of proteins has an immense influence on the corrosion, biocompatibility and wear properties of implantable metals. Proteins engage in multiple processes that could potentially inhibit or promote metal degradation, depending on the type of proteins, their concentration and the properties of the implant material. In the bio corrosion process, proteins are denatured and transform into a film on the metal surface, inhibiting corrosion. This film is found on many retrieved artificial joints, especially on worn areas, and can protect the passive film from scrapping due to its lubricating effect, thus decreasing tribocorroion. On the other hand, the interactions of metal ions with proteins (and amino acids) create colloidal organometallic complexes. Transport of the complex compounds away from the interface increases dissolution rates; thus, it accelerates the corrosion of metallic implants. The influence of protein adsorption on the corrosion behaviour of metallic biomaterials is presented in this review. Biocompatible metals that are favourably used as implants such as stainless steel, Co-Cr alloys, Ti alloys and biodegradable Mg and Fe alloys are specifically addressed. We have highlighted the adsorption phenomenon of protein on metallic implants, the interaction of proteins with metallic implants and the role of protein adsorption on implant biocorrosion behaviour as well as their wear resistance.

Adsorption and decontamination of α-synuclein from medically and environmentally-relevant surfaces

The assembly and accumulation of α-synuclein fibrils are implicated in the development of several neurodegenerative disorders including multiple system atrophy and Parkinson's disease. Pre-existing α-synuclein fibrils can recruit and convert soluble non-fibrillar α-synuclein to the fibrillar form similar to what is observed in prion diseases. This raises concerns regarding attachment of fibrillary α-synuclein to medical instruments and subsequent exposure of patients to α-synuclein similar to what has been observed in iatrogenic transmission of prions. Here, we evaluated adsorption and desorption of α-synuclein to two surfaces: stainless steel and a gold surface coated with a 11-Amino-1-undecanethiol hydrochloride self-assembled-monolayer (SAM) using in-situ combinatorial quartz crystal microbalance with dissipation and spectroscopic ellipsometry. α-Synuclein was found to attach to both surfaces, however, increased α-synuclein adsorption was observed onto the positively charged SAM surface compared to the stainless steel surface. Dynamic light scattering data showed that larger α-synuclein fibrils were preferentially attached to the stainless steel surface when compared with the distributions in the original α-synuclein solution and on the SAM surface. We determined that after attachment, introduction of a 1N NaOH solution could completely remove α-synuclein adsorbed on the stainless steel surface while α-synuclein was retained on the SAM surface. Our results indicate α-synuclein can bind to multiple surface types and that decontamination is surface-dependent.

Surface and Protein Adsorption Properties of 316L Stainless Steel Modified with Polycaprolactone Film

The surface and protein adsorption properties of 316L stainless steel (316L SS) modified with polycaprolactone (PCL) films are systematically investigated. The wettability of the PCL films was comparable to that of bare 316L SS because the rough surface morphology of the PCL films counteracts their hydrophobicity. Surface modification with PCL film significantly improves the corrosion resistance of the 316L SS because PCL is insulating in nature. A coating of PCL film effectively reduces the amount of adhered bovine serum albumin (BSA) on the surface of 316L SS in a bicinchoninic acid protein assay. PCL is both biodegradable and biocompatible, suggesting the potential for the surface modification of implants used in human bodies; in these applications, excellent corrosion resistance and anticoagulant properties are necessary.

Protein interactions with layers of TiO2 nanotube and nanopore arrays: Morphology and surface charge influence

In the present work we investigate the key factors involved in the interaction of small-sized charged proteins with TiO₂ nanostructures, i.e. albumin (negatively charged), histone (positively charged). We examine anodic nanotubes with specific morphology (simultaneous control over diameter and length, e.g. diameter - 15, 50 or 100nm, length - 250nm up to 10μm) and nanopores. The nanostructures surface area has a direct influence on the amount of bound protein, nonetheless the protein physical properties as electric charge and size (in relation to nanotopography and biomaterial's electric charge) are crucial too. The highest quantity of adsorbed protein is registered for histone, for 100nm diameter nanotubes (10μm length) while higher values are registered for 15nm diameter nanotubes when normalizing protein adsorption to nanostructures' surface unit area (evaluated from dye desorption measurements) - consistent with theoretical considerations. The proteins presence on the nanostructures is evaluated by XPS and ToF-SIMS; additionally, we qualitatively assess their presence along the nanostructures length by ToF-SIMS depth profiles, with decreasing concentration towards the bottom.

STATEMENT OF SIGNIFICANCE

Surface nanostructuring of titanium biomedical devices with TiO₂ nanotubes was shown to significantly influence the adhesion, proliferation and differentiation of mesenchymal stem cells (and other cells too). A high level of control over the nanoscale topography and over the surface area of such 1D nanostructures enables a direct influence on protein adhesion. Herein, we investigate and show how the nanostructure morphology (nanotube diameter and length) influences the interactions with small-sized charged proteins, using as model proteins bovine serum albumin (negatively charged) and histone (positively charged). We show that the protein charge strongly influences their adhesion to the TiO₂ nanostructures. Protein adhesion is quantified by ELISA measurements and determination of the nanostructures' total surface area. We use a quantitative surface charge model to describe charge interactions and obtain an increased magnitude of the surface charge density at the top edges of the nanotubes. In addition, we track the proteins presence on and inside the nanostructures. We believe that these aspects are crucial for applications where the incorporation of active molecules such as proteins, drugs, growth factors, etc., into nanotubes is desired.

ToF-SIMS and Principal Component Analysis Investigation of Denatured, Surface-Adsorbed Antibodies

Antibody denaturation at solid-liquid interfaces plays an important role in the sensitivity of protein assays such as enzyme-linked immunosorbent assays (ELISAs). Surface immobilized antibodies must maintain their native state, with their antigen binding (Fab) region intact, to capture antigens from biological samples and permit disease detection. In this work, two identical sample sets were prepared with whole antibody IgG, F(ab')₂ and Fc fragments, immobilized to either a silicon wafer or a diethylene glycol dimethyl ether plasma polymer surface. Analysis was conducted on one sample set at day 0, and the second sample set after 14 days in vacuum, with time-of-flight secondary ion mass spectrometry (ToF-SIMS) for molecular species representative of denaturation. A 1003 mass fragment peak list was compiled from ToF-SIMS data and compared to a 35 amino acid mass fragment peak list using principal component analysis. Several ToF-SIMS secondary ions, pertaining to disulfide and thiol species, were identified in the 14 day (presumably denatured) samples. A substrate and primary ion independent marker for denaturation (aging) was then produced using a ratio of mass peak intensities according to denaturation ratio: [I_61.9534 + I_62.9846 + I_122.9547 + I_84.9609 + I_120.9461]/[I_30.9979 + I_42.9991 + I_73.0660 + I_147.0780]. The ratio successfully identifies denaturation on both the silicon and plasma polymer substrates and for spectra generated with Mn⁺, Bi⁺, and Bi₃⁺ primary ions. We believe this ratio could be employed to as a marker of denaturation of antibodies on a plethora of substrates.

In vitro biocompatibility of CoCrMo dental alloys fabricated by selective laser melting

OBJECTIVE

Selective laser melting (SLM) is increasingly used for the fabrication of customized dental components made of metal alloys such as CoCrMo. The main aim of the present study is to elucidate the influence of the non-equilibrium microstructure obtained by SLM on corrosion susceptibility and extent of metal release (measure of biocompatibility).

METHODS

A multi-analytical approach has been employed by combining microscopic and bulk compositional tools with electrochemical techniques and chemical analyses of metals in biologically relevant fluids for three differently SLM fabricated CoCrMo alloys and one cast CoCrMo alloy used for comparison.

RESULTS

Rapid cooling and strong temperature gradients during laser melting resulted in the formation of a fine cellular structure with cell boundaries enriched in Mo (Co depleted), and suppression of carbide precipitation and formation of a martensitic ɛ (hcp) phase at the surface. These features were shown to decrease the corrosion and metal release susceptibility of the SLM alloys compared with the cast alloy. Unique textures formed in the pattern of the melting pools of the three different laser melted CoCrMo alloys predominantly explain observed small, though significant, differences. The susceptibility for corrosion and metal release increased with an increased number (area) of laser melt pool boundaries.

SIGNIFICANCE

This study shows that integrative and interdisciplinary studies of microstructural characteristics, corrosion, and metal release are essential to assess and consider during the design and fabrication of CoCrMo dental components of optimal biocompatibility. The reason is that the extent of metal release from CoCrMo is dependent on fabrication procedures.

Surface-protein interactions on different stainless steel grades: effects of protein adsorption, surface changes and metal release

Implantation using stainless steels (SS) is an example where an understanding of protein-induced metal release from SS is important when assessing potential toxicological risks. Here, the protein-induced metal release was investigated for austenitic (AISI 304, 310, and 316L), ferritic (AISI 430), and duplex (AISI 2205) grades in a phosphate buffered saline (PBS, pH 7.4) solution containing either bovine serum albumin (BSA) or lysozyme (LSZ). The results show that both BSA and LSZ induce a significant enrichment of chromium in the surface oxide of all stainless steel grades. Both proteins induced an enhanced extent of released iron, chromium, nickel and manganese, very significant in the case of BSA (up to 40-fold increase), whereas both proteins reduced the corrosion resistance of SS, with the reverse situation for iron metal (reduced corrosion rates and reduced metal release in the presence of proteins). A full monolayer coverage is necessary to induce the effects observed.