An Investigation into the Relative Efficacy of High-Velocity Air-Fuel-Sprayed Hydroxyapatite Implants Based on the Crystallinity Index, Residual Stress, Wear, and In-Flight Powder Particle Behavior.

Due to its resemblance to the bone, hydroxyapatite (HA) has been widely used for bioactive surface modification of orthopedic implants. However, it undergoes significant thermal decomposition and phase transformations at a high operating temperature, leading to premature implant failure. This investigation uses high-velocity air-fuel (HVAF) spray, an emerging low-temperature thermal spray technique, to deposit HA over the Ti-6Al-4V substrate. Coating characteristics, such as the crystallinity index and phase analysis, were measured using X-ray diffraction, Raman analysis, and Fourier transform infrared spectroscopy, residual stress using the sin2ψ method, and tribological performance by a fretting wear test. The coating retained an over 90% crystallinity index, a crystallite size of 41.04 nm, a compressive residual stress of -229 ± 34.5 MPa, and a wear rate of 1.532 × 10-3 mm3 N-1 m-1. Computational in-flight particle traits of HA particles (5 to 60 µm) were analyzed using computational fluid dynamics; it showed that 90% of particles were deposited at a 700 to 1000 m/s velocity and a 900 to 1450 K temperature with a 2.1 ms mean residence time. In-flight particle oxidation was minimized, and particle impact deformation was maximized, which caused severe plastic deformation, forming crystalline, compressive residual stressed coatings. The thermal decomposition model of low-temperature HVAF-sprayed HA particles helped to understand the implants' crystallinity index, residual stress, and tribological characteristics. Hence, this experimental and computational analysis shows that the HVAF process can be a promising candidate for biomedical applications for having strong and durable implants.

Sodium hydroxide pre-treated Aspergillus flavus biomass for the removal of reactive black 5 and its toxicity evaluation.

The present study was focused on the removal of Reactive Black 5 (RB5) from aqueous solution using pre treated Aspergillus flavus as a biosorbent. Pre-treatment of fungal biomass with 0.1 M sodium hydroxide facilitated the removal of dye effectively when compared to untreated fungal biomass. Optimum biosorption conditions for RB5 removal was determined as a function of dye concentration (50-400 mg/L), biosorbent concentration (100-500 mg/L), incubation time (1-7hrs), pH (3-8) and temperature (20-50 °C). At the optimum conditions, the maximum removal efficiency of RB5 achieved by NaOH pretreated A. flavus was 91%. The dye removal was studied kinetically and it obeys the pseudo-second order model and the experimental equilibrium data well fitted the Langmuir isotherm indicating monolayer adsorption of dye molecules on the biosorbent. The thermodynamic parameters such as a change in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were calculated and negative values of ΔG suggested that the dye removal process was spontaneous at all temperatures. Furthermore, the values of ΔH revealed that the adsorption process was endothermic. Recovery of RB5 from the fungal biomass was effective using 0.1 M Na2CO3 as an eluent. The interaction of adsorbate with biosorbent was analyzed using UV-Vis and FT-IR spectroscopy, SEM and XRD analyses. Phytotoxicity and microbial toxicity studies revealed the non-toxic nature of the treated dye solution. Hence, the fungal biomass pretreated with NaOH was efficient in decolorizing RB5 as well as composite raw industrial effluent generated from dyeing industries.

Decolorization of safranin using Fissidens species and its ecotoxicological assessments: An in vitro and in silico approach.

Decolorization of safranin was investigated using Fissidens species in a batch system under optimized conditions. The decolorization efficiency was improved by optimizing the conditions such as initial pH (3-9), temperature (25-45 °C), initial dye concentration (10-50 mg/L), biosorbent dosage (100-500 mg/L) and contact time (1-6 days). Maximum decolorization (95%) was recorded at initial pH of 6 with dye concentration of 20 mg/L, biosorbent dosage of 200 mg/L at 30 °C and contact time of 2 days. Desorption studies revealed 0.1 N NaOH as the best desorbing agent with 92% recovery on third day. Experimental data well fitted to Langmuir isotherm and Pseudo-second order kinetic model. The negative values of ΔGo and positive value of ΔSo and ΔHo indicates that the reaction is spontaneous, favorable and endothermic. The biosorbent - dye interactions were confirmed using UV-Vis, FT-IR, XRD and FE-SEM with EDX studies. The detoxified nature of the dye degraded metabolites was confirmed by the significant growth of green gram. The color fastness and color strength of the fabrics dyed using Fissidens species treated dye solution were compared with the tap water dyed fabrics which indicated the reuse potential of treated water in textile sector. The decolorization efficiency was further confirmed through in silico approach, where safranin well docked with the active sites of Photosystem II protein D1 of the Fissidens species. Thus, the present study proves that Fissidens species is a promising biosorbent for safranin decolorization and will lay a platform for the control and management of environmental pollution.

Prodigiosin production from Serratia marcescens strain CSK and their antioxidant, antibacterial, cytotoxic effect and in silico study of caspase-3 apoptotic protein.

The present study emphasizes the production and optimization of prodigiosin (PG) pigment from Serratia marcescens strain CSK, which was isolated from Shevaroy Hills, Salem district, Tamil Nadu, India. The response surface methodology analysis was applied for the optimization process of PG production. The maximum production of PG (2950 mg/L) was obtained at pH 7.0 with the addition of tryptophan (4.0 g/L) and sucrose (3.0 g/L) with 60 h of incubation. Further, the PG was characterized using high-performance liquid chromatography, Fourier-transform infrared spectroscopy, and gas chromatography-mass spectrometry. The purified PG exhibited strong antioxidant and antibacterial activities. Also, PG's cytotoxic effects against human breast cancer (MCF-7) cells were observed through acridine orange-ethidium bromide (AO-EB) and Hoechst staining. Molecular dockingstudies revealed that PG could bind positively to the caspase-3 (breast cancer protein 1RE1) binding site with a binding energy score of 17.37 kcal/mol. Overall, the novel PG was found to be an anticancer drug for potential applications in the pharmaceutical industry.

Thermal spray processes influencing surface chemistry and in-vitro hemocompatibility of hydroxyapatite-based orthopedic implants.

Orthopedic implants made from titanium are a popular choice in the medical field because of their remarkable strength-to-weight ratio. Nevertheless, they may not interact well with human blood, resulting in thrombosis and hemolysis. In fact, non-hemocompatibility is believed to be responsible for about 31 % of medical device failures in the US alone, requiring painful and expensive revision surgery. To address this issue, bioactive hydroxyapatite coatings are applied to Ti-6Al-4V implants using thermal spray techniques. However, the temperature used during thermal processing impacts the coating's surface properties, affecting the mechanical and biological properties. Furthermore, the effectiveness of HA coatings on titanium for orthopedic applications has not been validated by biocompatibility tests, particularly hemocompatibility. In this study, we aimed to investigate the relative efficacy of three thermal spray processes of different temperature ranges: Atmospheric plasma spray (APS) (high temperature), Flame spray (FS) (moderate temperature), and High-Velocity Oxy-Fuel spray (HVOF) (low temperature), and study their impact on coating's surface properties, affecting blood components and implant's strength. The crystallinity of the HA coating increased by 32 % with a decrease in the operating temperature (APS < FS < HVOF). HVOF coating exhibited a ~ 34 % and ~ 120 % improvement in adhesion strength and ~ 31 % and 59 % increment in hardness compared to APS and FS coating, respectively, attributed to its low porosity, low coating thickness (~55 µm), and high degree of crystallinity. The HVOF coating showcased a significant increase in non-hemolytic behavior, with hemolysis rates ~8 and ~ 11 times lower than APS and FS coatings, respectively, owing to its smooth texture and high degree of crystallinity (p < 0.05). Furthermore, the HVOF coating exhibited minimal blood clotting based on the whole blood clotting assay, again confirmed by PT and aPTT assays showing delayed clotting time, indicating its non-thrombogenic behavior. The number of platelets adhered to the three coatings showed no significant difference compared to Ti-6Al-4V. APS and FS coatings showed low platelet activation, unlike HVOF coating and titanium, which revealed round platelets, similar to the negative control. Neither titanium nor HA coatings exhibited antibacterial properties, which may be due to their high affinity for organic substances, which promotes bacterial adhesion and replication. Among the three thermal processes, HVOF coating displayed good apatite growth, non-hemolytic, and non-thrombogenicity with no platelet activation owing to its low processing temperature, high degree of crystallinity (89.7 %), hydrophilicity, smooth (~4 µm) and dense (~97 %) microstructural properties. The results demonstrated that the HVOF-HA coating presented in this work meets the hemocompatible requirements and shows promise for prospective application as an orthopedic implant. Furthermore, this study has the potential to significantly reduce the use of animals in in-vivo research and improve their welfare while also cutting costs.

Effect of Surface Chemistry on Hemolysis, Thrombogenicity, and Toxicity of Carbon Nanotube Doped Thermally Sprayed Hydroxyapatite Implants.

Assessing blood compatibility is crucial before in vivo procedures and is considered more reliable than many in vitro tests. This study examines the physiochemical properties and blood compatibility of bioactive powders ((0.5-2 wt % carbon nanotube (CNT)/alumina)-20 wt %)) produced through a heterocoagulation colloidal technique followed by ball milling with hydroxyapatite (HAp). The 1 wt % CNT composite demonstrated a surface charge ∼5 times higher than HAp at pH 7.4, with a value of -11 mV compared to -2 mV. This increase in electrostatic charge is desirable for achieving hemocompatibility, as evidenced by a range of blood compatibility assessments, including hemolysis, blood clotting, platelet adhesion, platelet activation, and coagulation assays (prothrombin time (PT) and activated partial thrombin time (aPTT)). The 1 wt % CNT composite exhibited hemolysis ranging from 2 to 7%, indicating its hemocompatibility. In the blood clot investigation, the absorbance values for 1-2 wt % CNT samples were 0.927 ± 0.038 and 1.184 ± 0.128, respectively, indicating their nonthrombogenicity. Additionally, the percentage of platelet adhered on the 1 wt % CNT sample (∼5.67%) showed a ∼2.5-fold decrement compared to the clinically used negative control, polypropylene (∼13.73%). The PT and aPTT experiments showed no difference in the coagulation time for CNT samples even at higher concentrations, unlike HAC2 (80 mg). In conclusion, the 1 wt % CNT sample was nontoxic to human blood, making it more hemocompatible, nonhemolytic, and nonthrombogenic than other samples. This reliable study reduces the need for additional in vitro and in vivo studies before clinical trials, saving time and cost.

Bioactive surface modifications through thermally sprayed hydroxyapatite composite coatings: a review of selective reinforcements.

Hydroxyapatite (HA) has been an excellent replacement for the natural bone in orthopedic applications owing to its close resemblance to the bone properties; however, it is brittle and has low strength. Surface modification techniques have been able to allay such mineral issues by depositing on substrate. These methods, being economical, impart mechanical strength without compromising biocompatibility. In this review article, the discussion is confined to plasma spray (high temperature) and other low temperature surface modification techniques: high-velocity oxy-fuel (HVOF) and cold spray. The processing temperature seems to significantly affect the performance of implants deposited with HA. Monolithic HA may not add enough strength to the bioimplants. Hence, this review discusses selective reinforcements to HA and their roles in enhancing the properties. Herein, a variety of selective reinforcements are discussed, such as carbon allotropes: graphene, carbon nanotubes, and nano diamond; metallic materials: Ag, Sr, Mg, and Ti; ceramic materials: Al2O3, SiO2, ZrO2, and TiO2; multi-materials: Al2O3-CNT/HA, Al2O3-TiO2/HA and others; and functionally graded composites: HA, 20 and 50 wt% Ti-6Al-4V/HA layered coating. Most of these reinforcements could not trade-off between biocompatibility and strength. The detailed in vitro and in vivo studies are still lacking. The literature on the relative effectiveness of these reinforcements is scanty, while the interface between HA coating and reinforcements is seldom explored. This review presents the suitability of thermal spray techniques based on the microstructure, mechanical, and biological properties. Therefore, it is envisaged that the present review can intrigue future researchers to understand the scope of surface coatings in achieving the better performance of implants at clinical trials.

Improvement in Slurry Erosion and Corrosion Resistance of Plasma-Sprayed Fly Ash Coatings for Marine Applications.

Fly ash (FA), a multicompound mineral, is an industrial waste produced during coal burning in thermal power stations. It has been regarded as the most environmentally hazardous material. Furthermore, handling FA has been a significant challenge for many developing countries. Therefore, researchers have been exhorted to enhance its usage to counter its handling issues. FA is enriched with mullite, silica, and alumina. Having such mineralogy, FA can be envisaged as a promising candidate for combating erosion and corrosion in marine environments. With this motivation, the research aims to deposit as-received FA using the plasma-spraying technique onto a marine-grade steel substrate without additives and assess the performance of such coatings for erosion and corrosion properties. The coating has exhibited more than 100% improvement in microhardness. The erosion resistance was improved by ∼11% compared to that of the uncoated sample, which is attributed to the hardness to elastic modulus ratio (H/E) and its unique mineralogy. The minor improvement in erosion resistance was attributed to the coating's poor fracture toughness. The erosion study shows that slurry concentration and rotational speeds were the most influential parameters. The scar depth was significantly shallower for FA-coated samples. The corrosion resistance has improved only by ∼13.49%, owing to the porous nature of the coating. Therefore, such coatings with appropriate improvements in their properties are expected to assuage both environmental and industrial challenges.

Synthesis, characterization of acrylate polymer having chalcone moiety: evaluation of antimicrobial, anticancer and drug release study.

This article describes synthesis, characterization, antimicrobial, drug-releasing and anti-cancer activity of acrylate monomer and its polymer containing chalcone moiety. The synthesized polymers were characterized through IR, 1H NMR and UV-visible spectroscopy techniques. The molecular weight of the obtained polymer is found to be around 4000 g/mol. The synthesized polymers are thermally stable up to 260 °C. The monomer and its polymer show higher activity against gram-negative bacteria and these compounds show remarkable activity over breast cancer cells. The synthesized monomer and polymers showed higher anticancer activity. The inhibitory potential of monomers and polymers premeditated using optimized in vitro evaluation MTT assay and live cell images. The drug release potential was controlled through co-monomer, pH and temperature.

Process optimization of biogas energy production from cow dung with alkali pre-treated coffee pulp.

Biogas production from cow dung with co-substrate agricultural waste is one of the most demanding technologies for generating energy in a sustainable approach considering eco-friendly. In the present study, coffee pulp (CP) was pre-treated with 1% NaOH and combined with various proportions of cow dung (CD) to explore its biogas producing potentiality. The optimization of the process was studied using Response surface methodology. Statistics based on 3-D plots were generated to evaluate the changes in the response surface and to understand the relationship between the biogas yield and other parameters. The highest methane production (144 mL/kg) was achieved after 90 h of incubation with 1:3 of CP and CD at 40 °C. Gas chromatography analyzes the chemical compositions of the generated biogas and its post combustion emissions. The chemical composition of the substrates before digestion and after fermentation (biogas spent sludge) were measured in terms of fiber content and the values were noted as, total solids (0.53%), ash content (9.2%), volatile fatty acid (100 mg/L), organic carbon (46%) and a total carbohydrate (179 mg/g). The results of the optimization of biogas production presented in this work found to have significance with the process parameters. The outcome of the study has supported the fact of conventional combustion technology that has to be upgraded to prevent these hazardous emissions into the atmosphere.

Induction of p53 dependent apoptosis upon overexpression of a nuclear protein tyrosine phosphatase.

Two ubiquitously expressed protein tyrosine phosphatases, PTP-S2 and PTP-S4 (also known as TC45 and TC48, respectively), are alternately spliced products of the same gene. Overexpression of PTP-S2 by transient transfection induced chromatin condensation and nuclear fragmentation, typical of apoptosis. Expression of PTP-S4 resulted in a much lower number of cells with apoptotic phenotype. PTP-S2 induced apoptosis in MCF7 and A549 human tumor cell lines which are p53 positive but not in HeLa and SW620 cells which are p53 negative. Apoptosis induced by PTP-S2 in MCF7 cells was inhibited by cotransfection with mutant p53 (Arg-273 --> His) but not by wild type p53. PTP-S2 induced apoptosis was inhibited by antiapoptotic protein Bcl2 and certain inhibitors of caspases. These results suggest that the nuclear tyrosine phosphatase PTP-S2 induces p53 dependent, serum starvation independent and caspase mediated apoptosis.

Regulation of expression of beta-galactoside alpha 2,6-sialyltransferase in a rat tumor, Zajdela ascitic hepatoma.

Tumor cell surface sialic acid levels determine a number of important properties governing cellular interactions and cell-cell communication. Towards understanding the mechanism of regulation of sialic acid levels upon cellular transformation, we have studied the regulation of expression of beta-galactoside alpha 2,6-sialyltransferase in a rat tumor, the Zajdela ascitic hepatoma. We demonstrate distinct differences in the regulation of expression of the enzyme in the tumor cells as compared to normal liver cells. The expression of sialyltransferase is regulated both at the transcriptional and post-transcriptional level in a tissue-specific manner.

Differential expression of thymidine kinase gene in two subpopulations of a rat tumour correlates with their tumorigenic and cell division potential.

We have studied the expression of the thymidine kinase (TK) gene in two kinetically heterogenous populations of a rat tumour cell line--the Zajdela ascitic hepatoma (ZAH). We have demonstrated that the TK gene is differentially expressed in the two cell types. The more tumorigenic and rapidly dividing subpopulation shows higher levels of mRNA and enzyme activity for TK. In addition, we have shown that the tumorigenic cells accumulate the primary unspliced transcript and utilise only part of it for maturation. It is, therefore, likely that ZAH cells regulate their division and possibly tumorigenic potential by regulating the expression of the TK gene.

Safety of left innominate vein division during aortic arch surgery.

BACKGROUND: The surgical approach to the aortic arch via median sternotomy can be hindered by the left innominate vein (LIV). Retraction of the LIV may injure the vein. The safety of LIV ligation has been controversial. Opinion has also differed regarding whether a divided vein should be reanastomosed after arch replacement is completed. We report our experience with division and ligation of the LIV for improved aortic arch exposure and facilitated excision of mediastinal tumors. METHODS: From January 1996 to June 1998, the LIV was divided and ligated in 14 patients (8 men, 4 women) after consideration of local anatomy, adequacy of aortic arch exposure, level of distal aortic anastomosis, and in case of mediastinal tumors, extent of involvement of mediastinal structures. The LIV was divided between clamps, doubly ligated, and the ends oversewn. Patients were assessed at 1 month and at yearly intervals for upper extremity edema and neurologic symptoms. RESULTS: In 12 patients LIV division improved aortic arch access, and in 2 patients, it facilitated excision of mediastinal tumors. The mean age of patients was 56 years (range 22 to 80). Follow-up ranged from 1 week to 30 months. All patients had left upper extremity edema for 7 to 10 days, which resolved with arm elevation. One early patient required reexploration for bleeding from the LIV stump. One patient died because of multiorgan dysfunction. None had any residual left upper extremity edema or neurologic symptoms. CONCLUSIONS: We conclude that, although not uniformly or commonly necessary, division of the LIV can safely be utilized to facilitate aortic arch exposure without significant long-term morbidity. LIV reanastomosis is not necessary.

Differential amplification and expression of c-myb oncogene in Zajdela ascitic hepatoma.

Organisation and expression of c-myb protooncogene have been studied in a heterogeneous tumour the Zajdela ascitic hepatoma (ZAH). The myb gene is selectively amplified in the more tumorigenic subpopulation of the tumour while the non-lethal subpopulation does not show any change. Analysis of transcripts of the myb gene in tumorigenic versus nontumorigenic cells shows that the level of amplification of the gene does not correspond to the level of its transcription. Results have been discussed in the light of existing evidence regarding the role of c-myb gene expression during cell cycle.

Response of some Calvin cycle enzymes subjected to salinity shock in vitro.

Leaf enzyme extracts of 10 day old seedlings of horsegram were subjected to NaCl or Na2SO4 treatment in vitro. Salinity shock caused decline in the activities of RuBP carboxylase, R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. At low concentrations, Na2SO4 did not alter the activities of R-5-P kinase, R-5-P isomerase and NADP-Gly-3-P dehydrogenase. RuBP carboxylase was found to be more sensitive to salt shock than the other enzymes studied. Further, NaCl was more toxic to the enzyme activities as compared to Na2SO4.

Stress responses in two genotypes of mulberry (Morus alba L.) under NaCl salinity.

Changes in biomass yield rates, cell membrane stability (CMS), malondialdehyde (MDA) content and in the levels of physiological stress markers such as proline and glycine betaine in two high yielding genotypes (S1 and ATP, salt tolerant and salt sensitive, respectively) of mulberry under NaCl salinity were studied. Biomass yield rates and CMS were significantly decreased in both the genotypes under stress conditions. Per cent of decrease in biomass yield rate and CMS was relatively less in S1 than in ATP. Salt stress results a significant increase in the accumulation of proline, by 6-fold in S1 and 4-fold in ATP. Glycine betaine content was also increased significantly in stressed plants. However, the per cent increase was more in S1 than in ATP. The level of lipid peroxidation as indicated by MDA formation was greater in ATP than in S1. These results clearly support the better salt tolerant nature of S1 compared to ATP genotype.

Anterior cervical osteophytes: a rare cause of dysphagia.

Anterior cervical osteophyte is a rare cause of dysphagia usually occurring in the elderly. We report two cases in which the anterior cervical osteophytes impinged upon the esophagus, and we describe their surgical management. Initial investigation of a case of dysphagia should be directed to the common causes; however, in the elderly and in those with disorders of the cervical spine an anterior cervical osteophyte may be the cause of dysphagia.

Cell free ascitic fluid prevents loss of cell surface sialic acid from Zajdela Ascitic Hepatoma cells in culture.

In the Zajdela Ascitic Hepatoma (ZAH), a rat tumor, high levels of cell surface sialic acid residues are present which masked the immunogenicity of the cells. We have shown here that cell surface sialic acid level goes down rapidly when ZAH cells are put in culture. The reduction in surface sialic acid levels is due to a decrease in sialic acid residues on the major sialylated glycoprotein, gp 120, as well as a decrease in gp 120 polypeptide. The loss of sialic acid from the cultured cells is reduced if the cells are cultured in the presence of cell free ascitic fluid from ZAH tumor.