Bovine Calf Serum Research Articles

Protein-metal interactions due to fretting corrosion at the taper junction of hip implants: An in vitro investigation using Raman spectroscopy

Modular hip implants are a clinically successful and widely used treatment for patients with arthritis. Despite ongoing retrieval studies the understanding of the fundamental physico-chemical mechanisms of friction and wear within the head-taper interface is still limited. Here, we Raman-spectroscopically analyze structural features of the biotribological material which is formed within the taper joint between Ti6Al4V and low-carbon cobalt alloy or high-nitrogen steel surfaces in in vitro gross-slip fretting corrosion tests with bovine calf serum. As a function of the fretting duration, we investigate short and long aliphatic chains and their adsorption behavior on the cobalt- and steel-type surfaces. Using the intensity and frequency shifts of the amide I and III Raman bands, we furthermore identify progressive protein folding and unfolding including the secondary structures of α-helix, β-sheet, and random-coil configuration as well as the formation of proteinaceous clusters depending on the hydrophilicity of the metallic surfaces. We additionally find a mixture of chromates and iron oxides with tryptophan and tyrosine at the worn cobalt alloy and high-nitrogen steel surfaces, respectively. Also, for long fretting duration, sp2 hybridized amorphous carbon is formed due to fretting-induced cleavage of proteins. Statement of significanceDespite efforts enhancing the biomedical tribology of hip implants, the impact of the organic environment on friction and wear at the femoral head-stem taper interface is limitedly understood. Using Raman spectroscopy we resolve structural changes within the biotribological material agglomerated at biomedical-grade metal alloys due to metal-organic interactions during in vitro fretting corrosion tests. Adsorption of short and long aliphatic chains, progressive protein (un)folding and proteinaceous cluster formation depend to a distinguishable extent on the fretting duration and type of alloy. Chromates and iron oxides are mixed with tryptophan and tyrosine, and amorphous carbon is formed resulting from a fretting-induced cleavage of serum proteins. Such information spectroscopically gleaned from biotribological material are vital to improve the design and performance of taper junctions.

Luminescent Cd-MOF and its mixed matrix membrane as a chemical sensor for selective and reversible detection of folic acid and Fe3+, and visible fingerprint identifying

A new luminescent metal-organic framework (MOF), {Cd2(L)2(HCO2)(OH)(H2O)}n (1) (HL = 4-(4-(pyridin-4-yl)benzamido) benzoic acid) was synthesized under solvothermal conditions, which was then incorporated into poly(methyl methacrylate) (PMMA) to produce a flexible Cd-MOF-based MMM, 1@PMMA. 1@PMMA could serve as a selective and sensitive fluorescent sensor with remarkable recyclability for detecting folic acid (FA) and Fe3+. More fascinatingly, 1@PMMA displayed a visual and convenient detection for FA and Fe3+ by naked eyes. Furthermore, 1@PMMA was successfully applied for the determination of FA and Fe3+ in the bovine calf serum samples, which demonstrates that the luminescent MOF-based MMMs could serve as promising applicants for detecting biomolecules and metal ions in biological samples. In addition, 1 could be applied for the visible identification of fingerprints.

Effects of Polyunsaturated Fatty Acid/Saturated Fatty Acid Ratio and Different Amounts of Monounsaturated Fatty Acids on Adipogenesis in 3T3-L1 Cells.

(1) Background: Adipose tissue serves as a central repository for energy storage and is an endocrine organ capable of secreting various adipokines, including leptin and adiponectin. These adipokines exert profound influences on diverse physiological processes such as insulin sensitivity, appetite regulation, lipid metabolism, energy homeostasis, and body weight. Given the integral role of adipose tissue in metabolic regulation, it is imperative to investigate the effects of varying proportions and types of dietary fats on adipocyte function. In addition, our previous study showed that P/S = 5 and MUFA = 60% appeared to be beneficial in preventing white adipose tissue accumulation by decreasing plasma insulin levels and increasing hepatic lipolytic enzyme activities involved in β-oxidation. Therefore, the objective of this study was to explore the effects of a polyunsaturated fatty acid (PUFA) to saturated fatty acid (SFA) ratio of 5 and varying levels of monounsaturated fatty acids (MUFA = 30% or 60%) on lipogenesis. (2) Methods: We cultured 3T3-L1 mouse embryo fibroblasts in Dulbecco's modified Eagle's medium (DMEM) containing 10% bovine calf serum until confluent. Varying ratios of palmitic acid (PA), oleic acid (OA), and linoleic acid (LA) were first bound with bovine serum albumin (BSA) before being applied to 3T3-L1 adipocytes in low doses and in high doses. (3) Results: Low doses of P/S ratio = 5, MUFA = 60% (M60) fatty acids decreased the accumulation of triglycerides in mature adipocytes by decreasing the mRNA expression of adipogenic factors, such as peroxisome proliferator-activated receptors (PPARs), lipoprotein lipase (LPL), and glucose transporter-4 (GLUT-4), while increasing lipolytic enzyme (hormone-sensitive lipase, HSL) expression when compared to high doses of P/S ratio = 5, MUFA = 60% (M60), low and high doses of P/S ratio = 5, MUFA = 30% (M30). Furthermore, the treatment of M60 in low doses also decreased the secretion of leptin and increased the secretion of adiponectin in adipocytes. (4) Conclusions: The composition of P/S = 5, MUFA = 60% fatty acid in low doses appeared to result in anti-adipogenic effects on 3T3-L1 adipocytes due to the down-regulation of adipogenic effects and the transcription factor.

Performance of Austenitic High-Nitrogen Steels under Gross Slip Fretting Corrosion in Bovine Serum.

Modular artificial hip joints are a clinical standard today. However, the release of wear products from the head-taper interface, which includes wear particles in the nm size range, as well as metal ions, have raised concerns. Depending on the loading of such taper joints, a wide variety of different mechanisms have been found by retrieval analyses. From these, this paper concentrates on analyzing the contribution of gross slip fretting corrosion at ultra-mild wear rates using a bovine calf serum solution (BCS) as the lubricant. The parameters were chosen based on biomechanical considerations, producing wear rates of some ng/m wear path. In parallel, the evolution of tribomaterial (third bodies) was analyzed as to its constituents and generation rates. It has already been shown earlier that, by an advantageous combination of wear mechanisms and submechanisms, certain constituents of the tribomaterial remain inside the contact area and act like extreme-pressure lubricant additives. For the known wear and corrosion resistance of austenitic high-nitrogen steels (AHNSs), which outperform CoCrMo alloys even under inflammatory conditions, we hypothesized that such steels will generate ultra-mild wear rates under gross slip fretting. While testing AHNSs against commercially available biomedical-grade materials of CoCrMo and TiAlV alloys, as well as zirconia-toughened alumina (ZTA) and against itself, it was found that AHNSs in combination with a Ti6Al4V alloy generated the smallest wear rate under gross slip fretting corrosion. This paper then discusses the wear behavior on the basis of ex situ analyses of the worn surfaces as to the acting wear mechanisms and submechanisms, as well as to the tribological reaction products.

FRI018 A Novel Truncating Variant Of EBF2 Disrupts Human Adipocyte Differentiation In Lipodystrophy Syndromes: An Example Of A Discovery From A Clinical Translational Pipeline

Abstract Disclosure: M.C. Foss de Freitas: Advisory Board Member; Self; PTC Therapeutics. N. Wys: None. M. Udler: None. L. Pais: None. A. Monteiro da Rocha: None. O.A. MacDougald: None. E.A. Oral: Consulting Fee; Self; Regeneron Pharmaceuticals, Aegerion Pharmaceuticals, Ionis Pharmaceuticals Inc., Third Rock Ventures, Rejuvenate Inc. Grant Recipient; Self; Regeneron Pharmaceuticals, Aegerion Pharmaceuticals, Ionis Pharmaceuticals Inc., Novo Nordisk, Fractyl Laboratories, Rhythm pharmaceuticals, GID Dynamics. Other; Self; Aegerion Pharmaceuticals. T. Chun: None. Objective/Goals: Partial Lipodystrophy is characterized by the gradual loss of adipose tissues, which progresses after birth. The genetic and molecular underpinning of many cases of partial lipodystrophy have not been fully understood. Aiming to better understand the molecular pathogenesis of familial partial lipodystrophy, we initiated deep sequencing for our patients with partial lipodystrophy syndromes. A novel variant of early B cell factor 2 (EBF2) was identified. Here we report the biological impact of a novel truncating EBF2 variant. Methods: We performed loss-of-function and gene rescue experiments using 3T3-L1 and human primary subcutaneous preadipocytes. All cells were cultured in DMEM with 10% bovine calf serum (Invitrogen). After lentivirus transfection (Full-length EBF2 or truncated variant EBF2), cells were grown to confluence and then exposed to adipogenesis induction media containing dexamethasone, insulin and isobutyl methylxanthine. Total RNA was extracted using RNeasy Mini Kit (Qiagen), and cDNA was synthesized using IScript (Bio-Rad). Real-time qPCR was performed using TaqMan probes for Pparg and Fabp4, two key adipogenesis markers. Results: The patient was found to carry a heterozygous nonsense mutation in exon 6 of 16 (NM_022659.4) of EBF2, causing the premature termination of the protein at amino acid position 165 (EBF2 8:26033143 C>A (hg38), c.493G>T, p.Glu165Ter). Adipogenesis was significantly suppressed in 3T3-L1 cells when endogenous Ebf2 was suppressed with siRNA and lentiviral shRNA. Adipocytes with suppressed Ebf2 expression showed a marked reduction of intracellular lipid content and Pparg and Fabp4 expression (>80% reduction). With lentiviral gene transfer, EBF2 fully rescued adipogenic potential, whereas the truncated variant EBF2 p.Glu165Ter did not. Of note, 3T3-L1 cells transfected with the EBF2 variant impaired adipogenesis, suggesting an inhibitory effect of the EBF2 variant on adipogenesis. We next confirmed the inhibition in adipogenesis with the EBF2 variant in primary human preadipocytes from subcutaneous adipose tissues. Using lentiviral gene transfer in human preadipocytes, we observed that the full-length EBF2 increased the gene expression of PPARg and FABP4 while the truncated EBF2 variant did not. Conclusion: Our data suggest that EBF2 is indispensable for adipogenesis of mouse and human preadipocytes. The truncating variant of EBF2 p.Glu165Ter likely plays a pathogenic role in the partial lipodystrophy presentation of this patient. Whole genome (or exome) sequencing undertaken in patients with partial lipodystrophy and subsequent biological functional analysis may lead to identification of novel mechanisms driving novel discoveries. Presentation: Friday, June 16, 2023

386 A novel truncating variant of EBF2 disrupts human adipocyte differentiation in lipodystrophy syndromes: an example of a discovery from a clinical translational pipeline

OBJECTIVES/GOALS: Aiming to better understand the molecular pathogenesis of familial partial lipodystrophy (PL), we initiated whole-exome sequencing for our patients with PL syndromes. A novel variant of early B cell factor 2 (EBF2) was identified. Here we report the biological impact of a novel truncating EBF2 variant. METHODS/STUDY POPULATION: Using 3T3-L1 and human primary subcutaneous preadipocytes, we performed loss-of-function and gene rescue experiments. All cells were cultured in DMEM with 10% bovine calf serum (Invitrogen) at 5% CO2. After lentivirus transfection, cells were grown to confluence and then exposed to adipogenesis induction media containing dexamethasone (0.25µM), insulin (1µg/ml) and isobutyl methylxanthine (0.5 mM). Total RNA was extracted using RNeasy Mini Kit (Qiagen) and cDNA was synthesized using IScript (Bio-Rad). Real-time qPCR was performed using TaqMan probes for Pparg and Fabp4, two key adipogenesis markers. RESULTS/ANTICIPATED RESULTS: Patient was found to carry a heterozygous nonsense mutation in exon 6 of EBF2, causing the premature termination of the protein at amino acid position 165. Adipogenesis was significantly suppressed in 3T3L1 cells when endogenous Ebf2 was suppressed with siRNA and lentiviral shRNA. Adipocytes with suppressed Ebf2 expression showed marked reduction of intracellular lipid content and Pparg and Fabp4 expression (>80% reduction). With lentiviral gene transfer, EBF2 fully rescued adipogenic potential, whereas the truncated variant EBF2 did not. Of note, 3T3-L1 cells transfected with the EBF2 variant displayed impaired adipogenesis, suggesting a dominant-negative effect of the EBF2 variant on adipogenesis. We confirmed the dominant effect of the EBF2 variant in human adipocyte differentiation. DISCUSSION/SIGNIFICANCE: Our data suggest that EBF2 is indispensable for adipogenesis. The loss of function and dominant-negative effect of the truncating variant of EBF2 likely plays a pathogenic role in PL. Whole exome sequencing of PL patients and ex-vivo functional analysis help identify novel gene variants and better understand the molecular pathogenesis of PL.

Expression profile of key genes involved in DNA repair mechanisms in bovine cumulus cells cultured with bovine serum albumin or fetal calf serum

Cumulus cells from cumulus-oocyte complexes (COC) matured in vitro in serum-free medium show high incidence of apoptosis and DNA double-strand breaks (DSB). This study aimed to characterize the transcript expression profile of selected genes involved in DNA repair mechanisms in bovine cumulus cells cultured with bovine serum albumin (BSA) or fetal calf serum (FCS). Briefly, bovine cumulus-oocyte complexes were in vitro matured with either, 0.4% BSA or 10% FCS for 3, 6, 12 or 24h. The total RNA of cumulus cells was used for real-time PCR analysis. Transcript abundance of XRCC6, XRCC5, DNAPK, GAAD45B, TP53BP1, RAD50, RAD52, ATM and BRCA2 target genes changed as the IVM proceeded (P<0.05). However, an interaction between protein source (FCS or BSA) and time was not detected (P≥0.05). Cumulus cells from COCs matured with BSA presented higher mRNA expression of two genes compared to FCS group: TP53BP1 at 6h and BRCA1 at 3, 6, 12 and 24h (P<0.05). In summary, our results showed for the first time the expression profile of the key genes involved in DSB repair mechanisms in cumulus cells obtained from bovine COCs matured with FCS or BSA. The higher mRNA expression of BRCA1 and TP53BP1 and lower mRNA expression of TNFAIP6 suggests an increase in apoptosis rate and DNA damage in cumulus cells cultured in BSA-supplemented medium and may explain, at least to some extent, the reduced developmental potential of bovine oocytes matured in serum-free medium.

Corrosion Study of Additively Manufactured Hip Implant Acetabular Shells: The Influence of Porous Structure and Post-treatment

Additively manufactured (AM) implants are rapidly increasing in the medical field, but corrosion resistance remains an essential concern on the newly developed AM implants. In the current study, three kinds of AM shells were evaluated in a three-electrode system under cyclic polarization and electrochemical impedance spectroscopy with bovine calf serum (BCS). The commercial acetabular shell with BIOFOAM® from MicroPort Inc. was the control group. We hypothesized that the AM shells would demonstrate comparative corrosion properties to the control group. After the corrosion testing, all groups were examined with scanning electron microscopy (SEM) with elemental analysis of energy-dispersive spectroscopy (EDS). Based on results of corrosion experiments, AM shells presented less corrosion current in cyclic polarization, which is supported by electrochemical impedance spectroscopy (EIS). After fitted with the equivalent circuit with EIS data, AM shells exhibited higher resistance of polarization and lower capacitance, indicating higher corrosion resistance. With examination of SEM with EDS, a patchy layer of titanium with higher carbon and oxygen concentration was apparent on the surface of the control group, which might cause the galvanic effect inducing higher corrosion currents. In conclusion, AM shells demonstrated a better corrosion resistance than the control group, but there were several limitations in the current study. Future research is required to fully assess the corrosion properties of implants.

An investigation on tribological behavior of methacrylated κ-carrageenan and gellan gum hydrogels as a candidate for chondral repair.

Natural polysaccharides have recently attracted attention as structural biomaterials to replace focal chondral defects. In the present study, in-vitro tribological performance of methacrylated κ-carrageenan and gellan gum hydrogels (KA-MA and GG-MA) was evaluated under physiological conditions. Coefficient of friction (COF) was continuously recorded over testing whilst worn area was measured post-testing. The findings help improve our understanding of KA-MA-H and GG-MA-H tribological performance under various physiological conditions. The friction and wear performance of the hydrogels improved in bovine calf serum lubricant at lower applied loads. Adhesion was the dominant wear mechanism detected by SEM. Among the proposed hydrogels GG-MA-H found robust mechanical properties, increased wear resistance and considerably low COF, which may suggest its potential usage as a cartilage substitute.

Rheological Behavior of Different Calf Sera before, during and after Biomechanical Testing

Due to different rheological behavior of human synovial fluid and the test mediums for in vitro examinations, wear tests cannot replicate the in vivo situation completely. The standards for wear testing indicate calf serum as in vitro test medium. However, these standards do not contain precise information on the main constituent components and the rheological properties. In this study, bovine calf serum and newborn calf serum with a protein concentration of 20 g/L, both approved for wear testing defined by the International Organization for Standardization (ISO), were characterized according to their rheological properties to detect differences before and during tribological simulation. The rheological behavior was determined at five defined intervals of a tribological test. The two test fluids differ in their rheological properties before and during the test and can therefore lead to deviating results in tribological testing. Furthermore, both test media changes considerably over test duration. At a test duration of 0.5 Mio cycles, both fluids have changed so that there is no longer any difference between them in terms of rheological properties. These changes could be attributed to denaturation and degradation of proteins. Thus, the choice of medium impacts tribological test results which should be considered for the interpretation of these studies.

Hip implant modular junction: The role of CoCrMo alloy microstructure on fretting-corrosion

Cobalt-chromium-molybdenum (CoCrMo) alloy is one of the most used metals in total hip replacement (THR) due to the alloy's superior corrosion qualities and biocompatibility. Over time these prostheses may undergo wear and corrosion processes in a synergistic process known as tribocorrosion. Implant retrieval studies have shown that damage patterns on THR modular junction surfaces indicating specifically in vivo fretting-corrosion to take place. To date, there have been no studies on the fretting-corrosion behaviors of CoCrMo alloy under the consideration of specific microstructural features. A custom-built flat-on-flat fretting-corrosion setup was utilized to test the synergistic tribocorrosion behavior of fretting-corrosion. The difference in microstructure was generated through the cutting orientations of the transverse and the longitudinal direction of the bar stock material, where the longitudinal cut exhibits a characteristic banded microstructure (banded group) and the transverse cut a homogenous microstructure (unbanded group). A three-electrode system was employed to monitor the induced currents. Two different types of electrolytes were used in the current study: 1. Bovine calf serum (BCS-30 g/L protein) (normal conditions) 2. BCS with Lipopolysaccharide (LPS, 0.15 μg/ml) (simulated infectious conditions). In the free potential mode, banded samples showed an increased potential compared to the unbanded samples. In potentiostatic conditions, the banded group also exhibited a higher induced current in both electrolyte environments, indicating more corrosion loss. Both Nyquist and Bode plots showed both orientations of metal becoming more corrosion resistant post-fretting when compared to pre-fretting data. The longitudinal group at OCP demonstrated a unique shape of the fretting-loop, which might be related to tribochemical reactions. Based on the mechanical, electrochemical, and surface characterization data, the transverse group (unbanded) microstructures demonstrates a higher resistance to fretting-corrosion damage.

Effects of cinnamon extract on sirtuin activity: potential for metabolic regulation blood glucose control

Sirtuins (SIRTs) are a family of enzymes that are involved in several metabolic and inflammatory pathways in diseases. Sirtuins are histone‐deacetylase enzymes which remove an acetyl group from lysine residues in histone proteins. Acetylation of histones plays a role in epigenetic regulation of gene expression. Recent studies demonstrate that SIRT enzymes can regulate fasting glucose, concentration of circulating insulin, insulin resistance, pancreatic activity, and inflammation. Metabolic parameters, like glucose homeostasis and chronic inflammation, contribute to the development of diseases like type 2 diabetes mellitus (T2DM). Increasing expression of SIRT can aid in the regulation of these metabolic parameters and may be involved in diseases like T2DM. Our research aims to analyze the activity of HDACs and SIRT in 3T3L‐1 cells. 3T3L‐1 cells were grown in bovine calf serum and nuclear extracts were collected using a nuclear extraction kit. Nuclear extracts were then analyzed for protein concentration and added to the Epigenase™ Universal SIRT Activity/Inhibition Assay Kit. The data collected suggests that cinnamon does alter the activity of SIRT and further research will be explored to determine the extent to which this effect proves useful in the treatment of T2DM.

Corrosion Behavior of Selective Laser Melting (SLM) Manufactured Ti6Al4V Alloy in Saline and BCS Solution.

The frequency of surgeries involving the use of metal implants in orthopedic medicine to replace degenerative or fractured joints is increasing, and it is therefore important to optimize the lifespan and quality of these implants. Advances in additive manufacturing (AM), or 3D printing, are creating new opportunities to personalize implants in ways that reduce mechanical stress at the joint implant interface and improve bone ingrowth and implant stability; however, it is not well understood if and to what degree the AM process alters the corrosion behavior of the materials it produces. In this study, six Ti6Al4V prints manufactured via a selective laser melting (SLM) method were examined regarding their corrosion behavior in both saline and bovine calf serum (BCS) solutions. Ecorr and Icorr values were comparable between the CM-Ti6Al4V control and SLM-EDM surfaces; however, SLM surfaces were found to have more narrow passivation behavior evidenced by significant decreases in Epass values relative to CM-Ti6Al4V. We believe this is a consequence of microstructural differences between CM-Ti6Al4V and SLM-Ti6Al4V. Specifically, the SLM-Ti6Al4V demonstrated a dominant α' martensitic microstructure and decreased vanadium-rich β-phase. BCS solution had a detrimental effect on potential parameters, Ecorr and OCP, decreasing these values relative to their saline counterparts. Increased surface roughness of the SLM-printed surface seemed to amplify the effects of the BCS solution. Furthermore, modest decreases in Epass and Ipass were observed in BCS solution, suggesting that the presence of protein may also interfere with passivation behavior. These findings have implications for how SLM-Ti6Al4V implants will perform in vivo and could possibly influence implant longevity and performance.

Art’s Work in the Age of Biotechnology: Shaping Our Genetic Futures

Art’s Work in the Age of Biotechnology: Shaping Our Genetic Futures

Constructing High-Recognition Protein-Imprinted Materials Using "Specially Designed" Block Macromolecular Chains as Functional Monomers and Crosslinkers.

The use of a macromolecularly functional monomer and crosslinker (MFM) to stabilize and imprint a template protein is a new method to construct high-recognition protein-imprinted materials. In this study, for the first time, a "specially designed" block MFM with both "functional capability" and "crosslinking capability" segments was synthesized via reversible addition-fragmentation chain-transfer polymerization and used to fabricate bovine serum albumin (BSA)-imprinted microspheres (SiO2@MPS@MIPs-MFM) by the surface imprinting strategy. Results from circular dichroic spectrum experiments reflected that the block MFM could maintain the natural form of BSA, whereas its corresponding and equivalent micromolecularly functional monomer (MIM) seriously destroyed the secondary structure of proteins. Batch rebinding experiments showed that the maximum adsorption capacity and imprinting factor of SiO2@MPS@MIPs-MFM reached 314.9 mg g-1 and 4.02, which were significantly superior to that of MIM-based imprinted materials. In addition, since the crosslinking capability segments in block MFM involved zwitterionic functional groups with a protein-repelling effect, SiO2@MPS@MIPs-MFM showed better specific rebinding ability than the imprinted material prepared by MFM without this component. Besides, scanning electron microscopy and transmission electron microscopy images showed that the shell thickness of SiO2@MPS@MIPs-MFM was approximately 15 nm, and such a thin imprinted layer ensured its rapid adsorption equilibrium (120 min). As a result, SiO2@MPS@MIPs-MFM revealed fantastic selectivity and recognition ability in a mixed protein solution and could efficiently extract BSA from biological samples of bovine calf serum. The proposal of block MFM enriched the options and designability of monomers in protein imprinting technology, thereby laying a foundation for developing high-performance protein-imprinted materials.

A novel synthesis method of carbide-derived carbon (CDC) in open air for hip implants

The inferior tribocorrosion behavior of commonly used biomedical alloys has led to the early failure of total hip replacements (THRs) and serious complications. Our previous results have shown that carbide-derived carbon (CDC) produced by direct chlorination can provide excellent protection to Ti6Al4V and has a high durability.In this study, a novel method has been developed to synthesize CDC on Ti6Al4V substrates by electrolysis from LiCl-KCl with a low melting point. Compared to previous preparation processes, this newly developed approach eliminates the exposure to chlorine gas and the requirement of the inert gas environment, which makes the synthesis process more controllable and the CDC layer more uniform. X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM) techniques were utilized to characterize the products. Based on the characterization results, the produced CDC has a porous structure which may contain nanocrystalline graphite (NCG) and amorphous carbon (a-C). The theoretical thickness of the sample is estimated by a calculation which is approximately 1.44 μm. In addition, the performance of the new layer was tested in a tribocorrosion hip simulator. A system has a pin on ball contact and immersed in bovine calf serum of 30 g/L protein concentration, with a pH of 7.6 and a temperature of 37 °C. We applied a normal force of 16 N and ran the test for 3600 cycles with 1 Hz. According to the recordings of normal and tangential forces, the evolution of friction coefficient is deducted and reported in the results.The findings have shown that the CDC samples prepared by electrolysis method exhibit smaller friction coefficient (approximately 0.12) and potential drop (less than 0.1 V compared to 1.1 V for substrate). Therefore, it is promising that CDC prepared by the novel electrolysis approach can protect Ti6Al4V substrates from the tribocorrosive damages.

Temperature-sensitive tribological performance of titanium alloy lubricated with PNIPAM microgels

In the pressent work, nanosized poly (N-isopropyl acrylamide) (PNIPAM) microgels were prepared and used as lubricant additives in bovine calf serum (BCS) for titanium alloy/ultra-high molecular weight polyethylene contact. The effects of sliding speed, load, and temperature on the lubrication behavior were studied on a pin-on-disc tribometer. The tribological results showed that the PNIPAM microgels can significantly improve the lubricity of BCS solution. The PNIPAM microgels exhibited notable temperature-sensitive lubrication characteristics. When the temperature was close to the low critical solution temperature of the PNIPAM microgels, the contact had the lowest friction coefficient due to the formation of a good lubricating layer with collapsed microgels and proteins. This discovery contributes to establishing a new strategy for friction-reduction and antiwear of titanium alloy artificial joint materials.

The 7H11 Agar Medium Supplemented with Calf Bovine Serum for Susceptibility Testing of Mycobacterium tuberculosis Isolates Against Pyrazinamide.

Despite its importance, pyrazinamide (PZA) is a blind spot in drug susceptibility testing in tuberculosis laboratories. The aim of this study was to set up a reliable agar-based proportion method for detection of PZA-resistant phenotypes using Middlebrook 7H11 agar supplemented with calf bovine serum (CBS) compared with albumin/dextrose/catalase (ADC) enrichment and pncA/rpsA sequencing results. The 7H11 agar medium supplemented with 10% ADC or 10% CBS (pH 6.2) and 100 μg/mL PZA was used to detect PZA resistance among 64 Mycobacterium tuberculosis isolates. Sanger sequencing and whole-genome sequencing were performed to track mutations in the pncA, rpsA, and their upstream regions. A total of 43 rifampicin/multidrug-resistant, 20 drug-susceptible, and 1 isoniazid mono-resistant M. tuberculosis isolates were investigated. The 7H11+ADC and 7H11+CBS could detect 22 and 23 PZA-resistant strains, respectively. With the same specificity, the sensitivity and accuracy of 7H11+CBS was found to be a little greater than 7H11+ADC in PZA resistance detection compared with sequencing results. Twenty-four mutant strains were found to have different mutations in pncA-upstream, pncA and rpsA genes, in which Gly97Asp was the most dominant mutation. The results obtained from 7H11+CBS were comparable to the results of 7H11+ADC. Therefore, the 7H11 agar proportion method would be a less-expensive test using CBS and produces reliable results.

Rheologic Behavior of Bovine Calf Serum.

Recent studies have illuminated the rheological behavior of synovial fluid and the role of protein and hyaluronan (HA). However, with respect to artificial joint replacement in standardized wear simulations, bovine serum is used as fluid test medium. Little is known about the rheological characteristics of bovine serum, which are needed for precise tribological investigations. The steady shear viscosity of bovine calf serum is determined for protein concentrations used in standardized wear simulations depending on shear rate and temperature T. Additionally, the density of the serum is determined for both protein concentrations. The results show shear thinning behavior of bovine calf serum with a nearly Newtonian behavior in the range of high shear rates. Within the range of high shear rates, mean viscosities of η = 0.82–0.88 mPa·s were found for protein concentrations of 20 g/L and mean viscosities of η = 0.88–0.94 mPa·s for 30 g/L, decreasing with temperature. Densities of 1.004–1.005 g/cm3 and 1.007–1.008 g/cm3 were found for 20 and 30 g/L protein concentrations, respectively.

The role of fretting-frequency on the damage modes of THR modular junction: In-vitro study

According to the National Center for Health Statistics, currently, more than 250,000 total hip replacements annually in the US alone, with an estimated increase to 500,000 by the year 2030. The usage of tapered junctions between the femoral neck and head gives the surgeon flexibility in implant assembly. However, these modular junctions are subjected to micro-motion that may cause chemical and fretting-corrosion at the modular junction. Therefore, it is imperative to study these forces to mitigate their effects. The current study aims to understand the effects of fretting-corrosion as a function of fretting frequencies caused by common physical activities in an in-vitro model of hip modular junctions. The fretting system has a tribological contact condition of flat-on-flat, mounted to a load frame. CoCrMo pins were polished and immersed in a synovial fluid-like electrolyte solution (Bovine calf serum 30 g/l). Electrochemical measurements were made using a potentiostat. Samples then undergo 3600 cycles at 50 μm (to simulate gross slips), with a horizontal load at 200 N, and a frequency of 0.5 Hz, 0.7 Hz, 1 Hz, and 1.5 Hz to simulate Sit Down-Stand Up, Stair Climb, Walking, and Jogging, respectively. Worn surfaces were then examined under optical and scanning electron microscopy.The evolution of free potential as a function of time for tested frequencies shows the initial potential drop and stabilized trend in the potential evolution. The sample group at a higher frequency displays a higher tendency of corrosion than a lower frequency; however, the dissipation energy decreases as a function of fretting frequency. Both electrochemical and mechanical responses correlate to the variation in the fretting frequencies. Organometallic complexes were found on the surfaces of the samples that were subjected to a slower frequency of fretting, whereas mechanical grooving was noticed on samples with a faster frequency. Hence, these preliminary studies suggest that implant failure rates may be altered based on fretting-frequencies induced by physical activity. Further studies will be required to verify the findings and explore the potential role of fretting frequency in the damage modes of the modular junction.