Plasma Immersion Ion Implantation Treatment Research Articles

A biocompatible nanofibers modified by plasma for osteoblast growth differentiation.

This work employs nitrogen plasma immersion ion implantation (PIII) to modify electrospinning polylactic acid membranes and immobilizes essential fibroblast growth factors(bFGF) by forming cross-linking bonds. The study investigates the modified membranes' surface characteristics and the stimulatory effects of cross-linked bFGF polylactic acid membranes on osteoblast and fibroblast proliferation. The PIII process occurs under low vacuum conditions and is controlled by processing time and power pulse width. The experimental results indicate that, within a 400-second N2-PIII treatment, the spun fibers remain undamaged, demonstrating an increase in hydrophilicity (from 117° to 38°/36°) and nitrogen content (from 0% to 7.54%/8.05%). XPS analysis suggests the formation of a C-N-C=O cross-linked bond. Cell culture and activity assessments indicate that the PIII-treated and cross-linked bFGF film exhibits significantly higher cell growth activity (P<0.05) than the untreated group. These intergroup differences are attributed to the surface cross-linking bond content. In osteogenic induction, the results for each day show that the treated group performs better. However, the intergroup disparities within the cross-linked bFGF group disappear with prolonged culture time due to the rapid osteogenesis prompted by bFGF. The findings suggest that PIII treatment of electrospinning polylactic acid membranes holds promise in promoting osteogenesis in bone tissue scaffolds.

Identification of Expanded Austenite in Nitrogen-Implanted Ferritic Steel through In Situ Synchrotron X-ray Diffraction Analyses

The existence and formation of expanded austenite in ferritic stainless steels remains a subject of debate. This research article aims to provide comprehensive insights into the formation and decomposition of expanded austenite through in situ structure analyses during thermal treatments of ferritic steels. To achieve this objective, we employed the Plasma Immersion Ion Implantation (PIII) technique for nitriding in conjunction with in situ synchrotron X-ray diffraction (ISS-XRD) for microstructural analyses during the thermal treatment of the samples. The PIII was carried out at a low temperature (300–400 °C) to promote the formation of metastable phases. The ISS-XRD analyses were carried out at 450 °C, which is in the working temperature range of the ferritic steel UNS S44400, which has applications, for instance, in the coating of petroleum distillation towers. Nitrogen-expanded ferrite (αN) and nitrogen-expanded austenite (γN) metastable phases were formed by nitriding in the modified layers. The production of the αN or γN phase in a ferritic matrix during nitriding has a direct relationship with the nitrogen concentration attained on the treated surfaces, which depends on the ion fluence imposed during the PIII treatment. During the thermal evolution of crystallographic phase analyses by ISS-XRD, after nitriding, structure evolution occurs mainly by nitrogen diffusion. In the nitrided samples prepared under the highest ion fluences—longer treatment times and frequencies (PIII 300 °C 6 h and PIII 400 °C 3 h) containing a significant amount of γN—a transition from the γN phase to the α and CrN phases and the formation of oxides occurred.

Neuromorphic sensing of biomolecules covalently immobilised on polydimethyl glutarimide

Polydimethyl glutarimide (PMGI) layers with sub-micron thicknesses have been modified in a 2.5 kV Ar plasma immersion ion implantation (PIII) process to introduce free radical covalent binding sites. The surface roughness of the PMGI increased after the PIII treatment but no through-layer defects were observed. When applied to the treated PMGI, horseradish peroxidase (HRP) enzyme remained bound to the surface after extended immersion in sodium dodecyl sulfate solution (SDS). Hence, covalent binding between the activated surface and enzyme was confirmed. This covalent binding was achieved up to 24-h after the PIII process. The treated PMGI was then incorporated as a gate dielectric layer within a lateral three-terminal electrolyte-gated device. The device output characteristics resembled those of post-synaptic outputs; as successive (pre-synaptic) voltage pulses were applied to the gate, paired pulse depression and spike rate dependent plasticity were observed in the source-drain (post-synaptic) current. These characteristics were altered by the presence of HRP immobilised on the plasma-modified PMGI gate dielectric layer thus providing readout detection. These results and preliminary device characteristics show the potential for the plasma functionalized PMGI as a sensitive and reproducible biosensing technology.

Enhancing cell adhesive and antibacterial activities of glass-fibre-reinforced polyetherketoneketone through Mg and Ag PIII.

Glass-fibre-reinforced polyetherketoneketone (PEKK-GF) shows great potential for application as a dental implant restoration material; however, its surface bioinertness and poor antibacterial properties limit its integration with peri-implant soft tissue, which is critical in the long-term success of implant restoration. Herein, functional magnesium (Mg) and silver (Ag) ions were introduced into PEKK-GF by plasma immersion ion implantation (PIII). Surface characterization confirmed that the surface morphology of PEKK-GF was not visibly affected by PIII treatment. Further tests revealed that PIII changed the wettability and electrochemical environment of the PEKK-GF surface and enabled the release of Mg2+ and Ag+ modulated by Giavanni effect. In vitro experiments showed that Mg/Ag PIII-treated PEKK-GF promoted the proliferation and adhesion of human gingival fibroblasts and upregulated the expression of adhesion-related genes and proteins. In addition, the treated samples inhibited the metabolic viability and adhesion of Streptococcus mutans and Porphyromonas gingivalis on their surfaces, distorting bacterial morphology. Mg/Ag PIII surface treatment improved the soft tissue integration and antibacterial activities of PEKK-GF, which will further support and broaden its adoption in dentistry.

Osteo-Immunomodulatory Role of Interleukin-4-Immobilized Plasma Immersion Ion Implantation Membranes for Bone Regeneration.

Barrier membranes for guided tissue regeneration are essential for bone repair and regeneration. The implanted membranes may trigger early inflammatory responses as a foreign material, which can affect the recruitment and differentiation of bone cells during tissue regeneration. The purpose of this study was to determine whether immobilizing interleukin 4 (IL4) on plasma immersion ion implantation (PIII)-activated surfaces may alter the osteo-immunoregulatory characteristics of the membranes and produce pro-osteogenic effects. In order to immobilize IL4, polycaprolactone surfaces were modified using the PIII technology. No discernible alterations were found between the morphology before and after PIII treatment or IL4 immobilization. IL4-immobilized PIII surfaces polarized macrophages to an M2 phenotype and mitigated inflammatory cytokine production under lipopolysaccharide stimulation. Interestingly, the co-culture of macrophages (on IL4-immobilized PIII surfaces) and bone marrow-derived mesenchymal stromal cells enhanced the production of angiogenic and osteogenic factors and triggered autophagy activation. Exosomes produced by PIII + IL4-stimulated macrophages were also found to play a role in osteoblast differentiation. In conclusion, the osteo-immunoregulatory properties of bone materials can be modified by PIII-assisted IL4 immobilization, creating a favorable osteoimmune milieu for bone regeneration.

Helium plasma immersion ion implantation studies of tungsten and tungsten heavy alloys for fusion plasma facing components

Plasma fusion devices will require plasma-facing components (PFCs) which can withstand the extreme environment at the edge of a hot fusion plasma. Despite the excellent properties of tungsten(W) as a hard refractory metal, adverse effects such as embrittlement, melting, and morphological evolution have been observed in W when it is bombarded by a high-fluence of low-energy ions including helium. This study investigates the effect of helium ion bombardment on pure tungsten and a tungsten heavy alloy (W-HA)(NAECOMET 1000). Pure tungsten and NAECOMET 1000 samples were implanted with 3 keV helium ions with fluences ranging from to , using Plasma Immersion Ion Implantation (PIII). After PIII treatment, samples were analysed using scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed differences in surface morphology and topography. Although the melting and cracking of the Ni/Cu binder phase in the NAECOMET 1000 samples was seen under all implantation conditions, the Ni/Cu presence did somewhat slow the formation of W fuzz in comparison to pure tungsten. X-ray diffraction (XRD) studies showed peak shifts increasing with helium ion fluence for both the pure W and NAECOMET 1000 samples, as well as increase in mean crystallite size, confirming the distortion of the lattice. XPS compositional analysis showed a strong oxidation (>97) near the metal surface, after helium PIII treatment, for both pure W and NAECOMET 1000 W-HA samples. Some conclusions about the potential suitability of W-HA materials for fusion plasma PFCs are drawn.

Histochemical targeting: Combining plasma immersion ion implantation and histochemical probes to target magnetic particles to intracellular cytological features

Paramagnetic microparticles are effective tools for cell purification, diagnostics, imaging and drug delivery and have been used for over 30 years to separate cell types from complex mixtures. The targeting of magnetic particles to cells and tissues is dependent upon the use of antibodies and adhesion molecules as targeting modalities. Here, we present a novel paradigm for the targeting of microparticles to cells according to intracellular cytological characteristics. Cell-permeable histochemical dyes, when covalently conjugated to magnetic microparticles, following plasma immersion ion implantation (PIII) imbue the particles with cell targeting properties in a process we term histochemical targeting. PIII treatment and conjugation to the lipophilic dyes Nile Red or Nile Blue led to changes in microparticle size, surface charge and lipophilicity. PIII-treated microparticles covalently conjugated with Nile Red, crossed the live cell membrane and homed to intracellular neutral lipid droplets. Nile Blue-conjugated particles crossed live cell membranes and remained in the cytosol where free fatty acids localize. Magnetic cell sorting could be performed on cultured adipocytes, as well as rat liver and adrenal cell suspensions using particles conjugated to Nile Red or Nile Blue. Taken together, our findings demonstrate that histochemical probes can be covalently conjugated to magnetic particles following PIII treatment resulting in intracellular targeting. With a vast armamentarium of cell-permeable probes available, histochemical targeting could be applied to many fields requiring magnetic particle delivery to specific sites or isolation of particular cell types.

Effect of plasma ion immersion implantation on physiochemical and biological properties of silk towards creating a versatile biomaterial platform

Silk biomaterials are widely used in tissue engineering applications due to their mechanical tuneability, processability and low immunogenic response. However, due to the lack of cell binding sites, further modification is typically required to optimize silk biomaterials towards a specific biomedical application. Plasma immersion ion implantation (PIII) is a surface modification technique that can covalently attach a wide range of bioactive molecules onto silk surfaces to trigger desirable biological responses. However, the effect of PIII treatment on the surface and bulk properties of silk biomaterials remains largely unknown. Therefore, the aim of this study is to investigate PIII-treated silk (PIII-silk) biomaterials towards their use as a platform for biomedical applications. Silk films with or without PIII treatment were examined to determine changes to the surface and bulk properties, including the chemical, mechanical, degradation properties, and the in vivo immune response. PIII treatment of silk was found to alter surface chemistry with densification of the silk surface layer and the introduction of oxygen and nitrogen functional groups. This then resulted in a significant increase in surface stiffness but also led to minor changes in tensile properties of clinically relevant silk formats and minor differences in in vitro degradation properties. Following PIII treatment, there was a significant increase in HCAEC adhesion on PIII-silk compared to untreated silk but no significant differences in fibrous encapsulation and macrophage response when implanted in vivo in a subcutaneous mouse model. Together, these results show that PIII treatment of silk minimally compromises the bulk properties and can be used to promote cellular interactions as well as a means of reagent-free, covalent immobilization of biomolecules.

Plasma Surface Engineering to Biofunctionalise Polymers for β-Cell Adhesion

Implant devices containing insulin-secreting β-cells hold great promise for the treatment of diabetes. Using in vitro cell culture, long-term function and viability are enhanced when β-cells are cultured with extracellular matrix (ECM) proteins. Here, our goal is to engineer a favorable environment within implant devices, where ECM proteins are stably immobilized on polymer scaffolds, to better support β-cell adhesion. Four different polymer candidates (low-density polyethylene (LDPE), polystyrene (PS), polyethersulfone (PES) and polysulfone (PSU)) were treated using plasma immersion ion implantation (PIII) to enable the covalent attachment of laminin on their surfaces. Surface characterisation analysis shows the increased hydrophilicity, polar groups and radical density on all polymers after the treatment. Among the four polymers, PIII-treated LDPE has the highest water contact angle and the lowest radical density which correlate well with the non-significant protein binding improvement observed after 2 months of storage. The study found that the radical density created by PIII treatment of aromatic polymers was higher than that created by the treatment of aliphatic polymers. The higher radical density significantly improves laminin attachment to aromatic polymers, making them better substrates for β-cell adhesion.

Effect of Recombinant Human Perlecan Domain V Tethering Method on Protein Orientation and Blood Contacting Activity on Polyvinyl Chloride.

Surface modification of biomaterials is a promising approach to control biofunctionality while retaining the bulk biomaterial properties. Perlecan is the major proteoglycan in the vascular basement membrane that supports low levels of platelet adhesion but not activation. Thus, perlecan is a promising bioactive for blood-contacting applications. This study furthers the mechanistic understanding of platelet interactions with perlecan by establishing that platelets utilize domains III and V of the core protein for adhesion. Polyvinyl chloride (PVC) is functionalized with recombinant human perlecan domain V (rDV) to explore the effect of the tethering method on proteoglycan orientation and bioactivity. Tethering of rDV to PVC is achieved via either physisorption or covalent attachment via plasma immersion ion implantation (PIII) treatment. Both methods of rDV tethering reduce platelet adhesion and activation compared to the pristine PVC, however, the mechanisms are unique for each tethering method. Physisorption of rDV on PVC orientates the molecule to hinder access to the integrin-binding region, which inhibits platelet adhesion. In contrast, PIII treatment orientates rDV to allow access to the integrin-binding region, which is rendered antiadhesive to platelets via the glycosaminoglycan (GAG) chain. These effects demonstrate the potential of rDV biofunctionalization to modulate platelet interactions for blood contacting applications.

Biomimetic silk biomaterials: Perlecan-functionalized silk fibroin for use in blood-contacting devices

Blood compatible materials are required for the development of therapeutic and diagnostic blood contacting devices as blood-material interactions are a key factor dictating device functionality. In this work, we explored biofunctionalization of silk biomaterials with a recombinantly expressed domain V of the human basement membrane proteoglycan perlecan (rDV) towards the development of blood compatible surfaces. Perlecan and rDV are of interest in vascular device development as they uniquely support endothelial cell, while inhibiting smooth muscle cell and platelet interactions. rDV was covalently immobilized on silk biomaterials using plasma immersion ion implantation (PIII), a new method of immobilizing proteins on silk biomaterials that does not rely on modification of specific amino acids in the silk protein chain, and compared to physisorbed and carbodiimide immobilized rDV. Untreated and treated silk biomaterials were examined for interactions with blood components with varying degrees of complexity, including isolated platelets, platelet rich plasma, blood plasma, and whole blood, both under agitated and flow conditions. rDV-biofunctionalized silk biomaterials were shown to be blood compatible in terms of platelet and whole blood interactions and the PIII treatment was shown to be an effective and efficient means of covalently immobilizing rDV in its bioactive form. These biomimetic silk biomaterials are a promising platform toward development of silk-based blood-contacting devices for therapeutic, diagnostic, and research applications. Statement of significanceBlood compatible materials are required for the development of therapeutic and diagnostic blood contacting devices as blood-material interactions are a key factor dictating device functionality. In this work, we explored biofunctionalization of silk biomaterials with a recombinantly expressed domain V (rDV) of the human basement membrane proteoglycan perlecan towards the development of blood compatible surfaces. Perlecan and rDV are of interest in vascular device development as they uniquely support endothelial cell, while inhibiting smooth muscle cell and platelet interactions. rDV was covalently immobilized on silk biomaterials using plasma immersion ion implantation (PIII), a new method of immobilizing proteins on silk biomaterials that does not rely on modification of specific amino acids in the silk protein chain. These biomimetic silk biomaterials are a promising platform toward development of silk-based blood-contacting devices for therapeutic, diagnostic, and research applications.

PIII Treatment of SS Samples Using a Current-Controlled High-Voltage Pulser

Plasma immersion ion implantation (PIII) was conducted in a large volume chamber with a current-controlled high-voltage pulser, to test the vacuum, plasma, and PIII conditions, in a preparation for the treatments of large workpieces or the batch-processing mode. For that purpose, a rugged high-power pulser (10 kW average) based on solid-state moderate voltage pulse system (1 kV) was coupled to a high-voltage transformer (1:22) to feed different loaded sample supports placed in different positions inside the chamber. It was found that the plasma, when produced by a hot filament enhanced glow discharge source, is not uniformly distributed in the chamber but despite that, implantation doses are locally uniform within 10% for 10-15-cm distances, along with the supports. Stainless steel 304 (SS304) -type samples were successfully treated with nitrogen PIII and different tests showed improvements on their mechanical and tribological properties.

Nitrogen plasma immersion ion implantation treatment of Ti6Al7Nb alloy for bone-implant applications: Enhanced in vitro biological responses and in vivo initial bone-implant contact

Ti6Al4V alloy has been widely applied to orthopedic and dental implants; however, V ions release may have detrimental side effects. Ti6Al7Nb alloy provides mechanical characteristics similar to those of Ti6Al4V while with fewer potentially biological side effects. In the present investigation, nitrogen plasma immersion ion implantation (N-PIII) treatment was applied to Ti6Al7Nb alloy surfaces. N-PIII surface treatment formed a thin (< 100 nm) TiN-containing film on Ti6Al7Nb surface. A higher applied N-PIII voltage resulted in a higher TiN content on Ti6Al7Nb surface. Compared to the untreated Ti6Al7Nb surface, the N-PIII treated Ti6Al7Nb surface had higher surface roughness, hydrophilicity, hardness, corrosion resistance in simulated body fluid, protein (fibronectin) adsorption, and growth of human bone marrow mesenchymal stem cells, particularly Ti6Al7Nb surface with a higher TiN content. Initial bone-implant contact was investigated in vivo by implanting Ti6Al7Nb screw-type implants (with and without N-PIII treatment) in the femur of mini-pigs for two weeks. At two weeks of post-implantation, the N-PIII treated implant surface with a higher TiN content showed a higher initial bone-implant contact than other implants. Overall, the proposed N-PIII treatment of Ti6Al7Nb alloy surface (particularly with a higher TiN content) enhanced in vitro corrosion resistance, protein adsorption, and cell response as well as in vivo initial bone-implant contact.

Covalent Immobilization of N-Acetylcysteine on a Polyvinyl Chloride Substrate Prevents Bacterial Adhesion and Biofilm Formation.

Biofilm formation and antimicrobial resistance at surgical implant sites result in high morbidity and mortality. Identifying novel molecules that inhibit biofilm formation to coat surgical biomaterials is essential. One such compound is N-acetylcysteine (NAC), a potent antioxidant precursor for glutathione, necessary in mammalian cells and known to disrupt/prevent biofilms. In this study, NAC was covalently immobilized onto functionalized polyvinyl chloride surfaces using plasma immersion ion implantation (PIII) treatment that achieves covalent binding without the need for linker groups. NAC immobilization was characterized using water contact angles, Fourier-transform infrared, and X-ray photoelectron spectroscopy techniques. Bacterial viability and biofilm formation on NAC surfaces were assessed using resazurin assays, phase contrast microscopy, and colony counting experiments. Effect of NAC on bacterial polysaccharide production and DNA cleaving was investigated using the phenol-sulfuric acid method and the Qubit fluorometer. Surface thermodynamics between the NAC coating and bacterial cells were measured using the Lewis acid-base method. Surface characterization techniques demonstrated superficial changes after PIII treatment and subsequent covalent NAC immobilization. NAC-coated surfaces significantly reduced biofilm viability and the presence of Gram-negative and Gram-positive bacteria. NAC also decreased polysaccharide production and degraded DNA. This led to unfavorable conditions for biofilm formation on NAC-coated surfaces, as demonstrated by surface thermodynamic analysis. NAC-coated surfaces showed no cytotoxicity to human fibroblast cells. This study has successfully utilized NAC as an antibiofilm coating, which may pave the way for improved prophylactic coatings on medical implant devices in the future.

Improvement on UHMWPE and PMMA Surface Flashover Under Atmospheric Pressure Using PIII Processing

Polymers are plastic materials used as insulators in power supplies, pulsers, transformers, etc., because of their low cost and excellent insulating properties. However, in several applications, the insulating performance of these materials is limited by the surface flashover instead of the dielectric bulk breakdown (BD). On the other hand, many works have demonstrated that the material hydrophobicity has a huge effect on the increase of resistance to surface flashover in polymers. In this article, to change this material property, the plasma immersion ion implantation (PIII) technique has been used for the treatment of sample surfaces of two important polymers: ultrahigh molecular weight polyethylene (UHMWPE) and poly-methyl-methacrylate (PMMA) used in medical and industrial applications, respectively. By means of the PIII treatment, it was shown that the surface BD voltage of such polymers has increased, improving the resistance to surface flashover. Contact angle diagnostic and atomic force microscopy (AFM) were measured, respectively, for the surface hydrophobicity and roughness to correlate with the increase of the surface BD voltage. Moreover, a special BD testing pulser is employed to assess the polymer resistance to surface flashover by measuring the corresponding BD voltage under atmospheric pressure.

Improving the in vitro cell differentiation and in vivo osseointegration of titanium dental implant through oxygen plasma immersion ion implantation treatment

Titanium (Ti) is widely used in dental implants; however, the bioinert surface has been shown to limit osseointegration, particularly in patients with poor bone quality. This study created a thin bioactive oxide film on Ti dental implants via oxygen plasma immersion ion implantation (OPIII) to improve bone cell differentiation and osseointegration. OPIII treatment was performed using low (1016 ions/cm2) and high (4 × 1017 ions/cm2) doses of oxygen ions. The Ti surfaces were characterized in terms of topography, wettability, chemical composition, and crystal structure. The differentiation of human bone marrow mesenchymal stem cells on OPIII-treated Ti surfaces was evaluated in vitro in terms of alkaline phosphatase (ALP) activity (early stage marker) and von Kossa staining (late stage marker). The osseointegration of OPIII-treated screw-type Ti dental implants in the femur of rabbits was evaluated in vivo using scanning electron microscope/backscattered electron imaging and histological staining at 4 weeks after implantation. OPIII treatment could induce a Ti oxide film on Ti surface without altering the surface topography, roughness or wettability. Higher oxygen ions dose increased the thickness of the surface Ti oxide film as well as the proportion of rutile phase titanium dioxide (TiO2) in the Ti oxide film. The OPIII-treated Ti surfaces presented higher ALP expression level, stronger von Kossa staining signal, and higher bone-to-implant contact. Note that all of these effects were more pronounced on surfaces created using higher oxygen ions dose due to the higher proportion of rutile phase TiO2. Overall, our results indicate that OPIII treatment using higher oxygen ions dose can enhance the in vitro bone cell differentiation and in vivo osseointegration of Ti dental implants.

Covalent binding of molecules to plasma immersion ion implantation‐activated microparticles for delivery into cells

Delivery of biomolecules to target cells is an essential step in gene therapy, targeted drug delivery, and cell imaging, and can be achieved by encapsulation or conjugation to micro‐ or nanoparticles. For successful systemic delivery, these complexes must be stable under physiological conditions and prevent leakage of the cargo. Covalent binding of the active agent to a carrier is one‐way to facilitate this stability but frequently requires several steps. Here we show that plasma immersion ion implantation (PIII) treatment can activate the surface of paramagnetic polystyrene microparticles (MPs), increasing autofluorescence and allowing conjugation of biological molecules in a single‐step. Using PIII‐activated MPs, we demonstrate covalent binding of therapeutically relevant payloads including antibodies (Abs) and small‐interfering RNAs (siRNAs). The PIII‐activated magnetic particles were actively taken up by the cells, were nontoxic, and could be visualized due to increased autofluorescence induced by the PIII treatment. Ab and siRNA were effectively conjugated simultaneously to the active surface, and these functionalized MPs were also taken up by cells. This simple PIII‐based activation system has the potential to be applied to many different therapeutic approaches.

Plasma immersion ion implantation and shot peening influence on the fatigue strength of AA 7050-T7451 aluminum alloy

The 7xxx aluminum alloy series is applied in aircraft components that demand high specific mechanical strength and fatigue resistance. The corrosive environment and friction forces imposed on those components reduce the service life. Therefore, anodizing is frequently used to enhance resistance against corrosion and wear. However, anodizing decreases the fatigue life of aluminum alloys. Plasma immersion ion implantation (PIII) is an alternative surface treatment that has been used to improve surface hardness, corrosion resistance and reduce wear damage. The PIII treatment consists of accelerating positive ions towards a sample by applying negative high voltage pulses in plasma. The shot peening (SP) process is a surface treatment that can be used with other surface treatments to improve the fatigue strength. The present work aimed at investigating the fatigue behavior of AA 7050-T451 aluminum alloy treated with SP, PIII, and a combination of both SP and PIII surface treatments. The combination of SP and PIII treatments (SP + PIII) improved the fatigue performance with respect to the base material and was more efficient than PIII in improving the fatigue strength for high-cycle fatigue regime. The fatigue strength improvement is related to the induced compressive residual stresses at the surface layers, which was responsible for delaying the nucleation and early fatigue crack propagation periods. The residual stress at the surface changed from −62 MPa to −130 MPa and −210 MPa for the SP and SP + PIII conditions, respectively. Compared to chromic anodizing, the SP + PIII condition increased the fatigue life in about 4 times at a maximum stress level of 281 MPa. The combination of SP and PIII treatments tested in this work is more advantageous regarding fatigue behavior than chromic anodizing, which reduces the fatigue strength of the material.

Increasing fatigue resistance of AISI 4340 steel by nitrogen plasma ion-implantation

Failures in structural components due to cyclic loading are associated with materials surface damage. Coatings deposited by different surface processes are more or less effective to improve the degradation resistance of diverse elements. The present study aim is to analyze plasma immersion ion implantation (PIII) effect on axial fatigue strength, corrosion and wear resistance of AISI 4340 steel. Experimental results indicate an axial fatigue strength increase for 1, 2 and 3 h of treatment. PIII treatment was not effective to protect AISI 4340 steel against environmental aggressive action. In abrasive wear tests, lower pin mass reduction was observed due to superficial treatment.

Enhanced biocompatibility of polyurethane-type shape memory polymers modified by plasma immersion ion implantation treatment and collagen coating: An in vivo study

As one of the promising smart materials, polyurethane-type shape memory polymers (SMPU) have been extensively investigated as potential biomedical implant materials. However, the hydrophobicity and bio-inertness of SMPU are major problems for biomedical applications. We applied plasma immersion ion implantation (PIII) to increase surface wettability and enable one-step covalent, functionalisation of SMPU with biological molecules to create a tuneable, biocompatible surface. The changes of surface properties due to PIII treatment in nitrogen plasma were determined by measurements of morphology, contact angle, surface energy, and nanoindentation. Collagen attachment on SMPU with and without PIII treatment was measured by Attenuated total reflectance-Fourier transform infrared (ATR-FTIR). To investigate in vivo biocompatibility, SMPU with/without PIII and with/without collagen were subcutaneously implanted in mice. SMPU implants with surrounding tissue were collected at days 1, 3, 7, 14 and 28 to study acute/subacute inflammatory responses at histopathological and immunohistochemical levels. The results show that PIII treatment improves wettability and releases residual stress in the SMPU surfaces substantially. Covalent attachment of collagen on PIII treated SMPU in a single step incubation was demonstrated by its resistance to removal by rigorous Sodium Dodecyl Sulfonate (SDS) washing. The in-vivo results showed significantly lower acute/subacute inflammation in response to SMPU with PIII treatment + collagen coating compared to untreated SMPU, collagen coated untreated SMPU, and PIII treated SMPU, characterised by lower total cell numbers, macrophages, neovascularisation, cellular proliferation, cytokine production, and matrix metalloproteinase production. This comprehensive in vivo study of PIII treatment with protein coating demonstrates that the combination of PIII treatment and collagen coating is a promising approach to enhance the biocompatibility of SMPU, facilitating its application as an implantable biomaterial.