Improvement Of Biocompatibility Research Articles

Enhancing neurite growth and neural functions on polymeric nerve conduit with BMSC-derived ECM coating

The therapy of large defects in peripheral nerve injury (PNI) suffers from several drawbacks, especially the lack of autologous nerve donors. Nerve conduits are considered as a solution for nerve injury treatment, but biocompatibility improvements is still required for conduits prepared with synthetic materials. Cell-derived extracellular matrix (ECM) has drawn attention due to its lower risk of immunogenic response and independence from donor availability. The goal of this study is to coat bone mesenchymal stem cell-derived ECMs on poly(lactic-co-glycolic) acid (PLGA) conduits to enhance their ability to support neural growth and neurite extensions. The ECM-coated conduits have better hydrophilic properties than the pure PLGA conduits. A marked increase on PC12 and RSC96 cells' viability, proliferation and dorsal root ganglion neurite extension was observed. Quantitative PCR analysis exhibited a significant increase in markers for cell proliferation (GAP43), neurite extension (NF-H, MAP2, andβIII-tubulin) and neural function (TREK-1). These results show the potential of ECM-coated PLGA conduits in PNI therapy.

Nanomedicine: Innovative Strategies and Recent Advances in Targeted Cancer Therapy.

Nanomedicine's application of nanotechnology in medicine holds tremendous potential for diagnosing and treating life-threatening diseases such as cancer. Unlike conventional therapies, nanomedicine offers a promising strategy to enhance clinical outcomes while minimizing severe side effects. The principle of drug targeting enables specific delivery of therapeutic agents to their intended sites, making it a more precise and effective therapy. Combination strategies, such as the co-delivery of chemotherapeutic drugs with nucleic acids or receptor-specific molecules, are being employed to enhance therapeutic outcomes. Nanocarriers and drug delivery systems designed using these approaches offer resourceful co-delivery of therapeutic agents for anticancer therapy. Targeted drug delivery via nanotechnology-based techniques has become an urgent need and has shown significant improvements in therapeutic implications, pharmacokinetics, specificity, reduced toxicity, and biocompatibility. This review discusses the extrapolation of nanomaterials for developing innovative and novel drug delivery systems for effective anticancer therapy. Additionally, we explore the role of nanotechnology-based concepts in drug delivery research.

Insight the long-term biodegradable Mg-RE-Sr alloy for orthopaedics implant via friction stir processing

Magnesium alloys, noted for their substantial mechanical strength and exceptional biocompatibility, are increasingly being considered for use in biodegradable implants. However, their rapid degradation and significant hydrogen release have limited their applications in orthopaedics. In this study, a novel Mg-RE-Sr alloy was created by friction stir processing to modify its microstructure and enhance its degradation performance. Through microstructural characterization, the friction stir processing effectively refined the grains, accelerated the re-dissolution of precipitates, and ensured a uniform distribution of these phases. The processed alloy demonstrated improved comprehensive properties, with an in vitro corrosion rate of approximately 0.4 mm/y and increases in ultimate tensile strength and elongation by 37 % and 166 %, respectively. Notably, in vivo experiments involving a rat subcutaneous implantation model revealed a slower degradation rate of 0.09 mm/y and a uniform degradation process, basically achieving the requirements for ideal performance in orthopaedic applications. The superior degradation characteristics were attributed to the synergistic effect of attenuated galvanic corrosion and the formation of a dense Y(OH)3/Y2O3 film induced by an exceptional microstructure with a highly solid-soluted matrix and uniformly refined precipitates. Meanwhile, the alloys exhibited excellent biocompatibility and did not cause undesirable inflammation or produce toxic degradation products. These improvements in biocompatibility and degradation characteristics indicate great promise for the use of this friction stir processed alloy in osteosynthesis systems in the clinical setting.

High‐density implantable neural electrodes and chips for massive neural recordings

AbstractHigh‐density neural recordings with superior spatiotemporal resolution powerfully unveil cellular‐scale neural communication, showing great promise in neural science, translational medicine, and clinical applications. To achieve such, many design and fabrication innovations enhanced the electrode, chip, or both for biocompatibility improvement, electrical performance upgrade, and size miniaturization, offering several thousands of recording sites. However, an enormous gap exists along the trajectory toward billions of recording sites for brain scale resolution, posing many more design challenges. This review tries to find possible insight into mitigating the gap by discussing the latest progress in high‐density electrodes and chips for neural recordings. It emphasizes the design, fabrication, bonding techniques, and in vivo performance optimization of high‐density electrodes. It discusses the promising opportunities for circuit‐level and architecture‐level multi‐channel chip design innovations. We expect that joint effort and close collaboration between high‐density electrodes and chips will pave the way to high‐resolution neural recording tools supporting cutting‐edge neuroscience discoveries and applications.

Preparation of tantalum-containing coatings on NiTi shape memory alloys with enhanced in vitro cytocompatibility and antibacterial effectiveness

In this work, the magnetron sputtering method is used to deposit tantalum-containing coatings on NiTi shape memory alloys under various sputtering atmospheres including (i) 100% argon, (ii) 16.6% oxygen and 83.4% argon, and (iii) 16.6% nitrogen and 83.4% argon. This research examines how the sputtering atmosphere can impact surface morphology, roughness, wettability, biocompatibility, in vitro cytocompatibility, and antibacterial performance of tantalum-containing coatings. The calculation of nickel ions release by coupled inductively coupled plasma-optical emission spectrometry displayed that none of the coated samples showed any traces of nickel, unlike the bare NiTi substrate. This has led to an improvement in biocompatibility. Topographical measurements demonstrated the formation of a smooth surface under the argon-oxygen atmosphere, whereas the deposited layer in the argon-nitrogen atmosphere exhibited irregular ups and downs. The coatings deposited under the argon-nitrogen atmosphere result in a hydrophobic surface with many hills and valleys which can considerably enhance protein and cellular absorption. Besides, the samples coated under an argon-oxygen atmosphere with a smooth surface exhibited excellent antibacterial efficiency only as early as 6 h of incubation. This is probably due to the formation of amorphous tantalum pentoxide.

Improvement in Biocompatibility and Biointegration of Human Acellular Dermal Matrix through Vacuum Plasma Surface Treatment.

Efforts are ongoing to enhance the functionality of human acellular dermal matrices (hADMs), which are extensively utilized in reconstructive surgeries. Among these efforts, plasma treatments, particularly vacuum plasma treatments, have recently emerged in the medical field. This study aims to investigate the efficacy of a vacuum plasma treatment in enhancing the biocompatibility and biointegration of hADMs. Utilizing a plasma activator (ACTILINK reborn, Plasmapp Co., Ltd., Daejeon, Republic of Korea), hADMs were treated and evaluated through in vitro and in vivo analyses. Hydrophilicity changes were gauged by the blood absorption times, while SEM imaging was used to analyze physical surface deformation. Protein adsorption was measured with fluorescently labeled bovine serum albumin and fibronectin. For the in vivo study, mice were implanted with plasma-treated and untreated hADMs, and the post-implantation effects were analyzed through histological and immunofluorescence microscopy. The plasma-treated hADMs demonstrated a significantly enhanced hydrophilicity compared to the untreated samples. SEM imaging confirmed the maintenance of the microroughness after the treatment. The treated hADMs showed a significant reduction in fibronectin adsorption, a critical factor for cellular adhesion. In vivo, the plasma-treated hADMs exhibited reduced capsule formation and enhanced fibroblast infiltration, indicating improved biocompatibility and integration. These findings highlight the potential of a plasma treatment to enhance the performance of hADMs in clinical settings, offering a promising avenue for improving reconstructive surgery outcomes.

Improvement of biocompatibility of high molecular weight poly-3-hydroxybutyrate by blending with its functionalized oligomers

Oligomers of poly-3-hydroxybutyrate (PHB) were prepared by aminolysis of high molecular weight PHB with ethylenediamine and 1,4-diaminobutane. Polymer-oligomer blends (10, 30, and 50% content of the oligomers) were prepared as films by solution casting. As the content of oligomers increased, a gradual increase in the hydrophilicity of the polymer surface was observed, resulting reflected in the water contact angle decrease from 84° to 72–76°. In addition, a moderate decrease in elongation at break, Young's modulus, and tensile strength for the blends were observed as more oligomer was added to the film. Finally, the viability of NIH-3T3 mouse fibroblasts was higher compared to intact PHB when growing in non-prepared polymer/oligomer mixtures. These findings confirm the benefits of the introduction of a hydrophilic functionalized oligomer into the PHB matrix in terms of improving the biocompatibility of the resulting polymer/oligomer blends.

Fe-Zn alloy, a new biodegradable material capable of reducing ROS and inhibiting oxidative stress.

Fe-based biodegradable materials have attracted significant attention due to their exceptional mechanical properties and favorable biocompatibility. Currently, research on Fe-based materials mainly focuses on regulating the degradation rate. However, excessive release of Fe ions during material degradation will induce the generation of reactive oxygen species (ROS), leading to oxidative stress and ferroptosis. Therefore, the control of ROS release and the improvement of biocompatibility for Fe-based materials are very important. In this study, new Fe-Zn alloys were prepared by electrodeposition with the intention of using Zn as an antioxidant to reduce oxidative damage during alloy degradation. Initially, the impact of three potential degradation ions (Fe2+, Fe3+, Zn2+) from the Fe-Zn alloy on human endothelial cell (EC) activity and migration ability was investigated. Subsequently, cell adhesion, cell activity, ROS production and DNA damage were assessed at various locations surrounding the alloy. Finally, the influence of different concentrations of Zn2+ in the medium on cell viability and ROS production was evaluated. High levels of ROS exhibited evident toxic effects on ECs and promoted DNA damage. As an antioxidant, Zn2+ effectively reduced ROS production around Fe and improved the cell viability on its surface at a concentration of 0.04 mmol/l. These findings demonstrate that Fe-Zn alloy can attenuate the ROS generated from Fe degradation thereby enhancing cytocompatibility.

Microstructure development of AM-fabricated pure Zn with heat-treatment and its mechanical properties, degradation behavior, and biocompatibility

The fabrication of zinc (Zn) parts devoid of inherent defects through Powder Bed Fusion-Laser Beam (PBF-LB) remains a formidable challenge. This study focuses on the optimization of process parameters and the implementation of tailored heat treatment to achieve high-performance PBF-LB fabricated (PBF-LBed) pure Zn bulk and scaffolds. Microstructural analysis, residual stress assessment, mechanical property testing, electrochemical experiments, immersion tests, in vitro and in vivo evaluations were conducted. The research results revealed that, under optimized process parameters and subsequent annealing, the yield strength, ultimate tensile strength, and ductility of PBF-LBed parts exhibit remarkable enhancements. Concurrently, the grain size was refined to 3 μm, accompanied by a notable improvement in biocompatibility. It could be roughly concluded that the microstructure refinement obtained through the heat treatment could significantly enhance their mechanical and electrochemical performances. Meanwhile, an appropriate Zn ion release rate achieved through grain refinement might created a more conducive microenvironment for new bone formation. Consequently, heat-treated PBF-LBed pure Zn scaffolds exhibits superior performance and application potential compared to untreated scaffolds.

In Vitro and In Vivo Testing of Stereolithography (SLA)-Manufactured Haemocompatible Photopolymers for Blood Pump

A major medical problem of state-of-the-art heart ventricular assist devices (LVADs) is device-induced thrombus formation due to inadequate blood-flow dynamics generated by the blood pump rotor. The latter is a highly complex device, with difficulties during conventional manufacturing through milling or casting. Therefore, the additive manufacturing technology relying on stereo-lithography (SLA) capable of producing parts of significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as novel and flexible technology for that type of application. However, as yet state-of-the-art SLA is not suitable to produce fully safe blood-contacting devices. Therefore, the present experiment covered chemical, mechanical, rheological, tribological, and complex biocompatibility characterization in accordance with i.a. ISO 10993 standards, including hemolysis and an acute thrombogenicity blood test on fresh animal blood (both as innovative laboratory tests to avoid animal usage in preclinical studies) with a special focus on testing demonstrators of miniaturized blood pump rotors. The conducted tests indicated acceptable biocompatibility of the material and a slight improvement in biocompatibility with surface modification. Additionally, a high biocompatibility of the tested materials was confirmed. Based on studies and simulations, stereolithography (SLA) as an additive manufacturing technology with significantly increased freedom for a blood-flow-compatible, thrombus-risk-free design was chosen as a novel and flexible technology basis in the 4DbloodROT project to enable future manufacturing of rotors with exceptional biomimetic complexity.

One-step assembly of bimetal-phenolic networks for antifouling and antibacterial coatings

Titanium (Ti) and its alloys have been widely used as clinical implant biomaterials. However, protein adhesion and bacterial infection can negatively impact the efficacy of these implants. To combat this, a promising strategy is to develop a versatile coating on Ti materials that endows them with antifouling and antibacterial capabilities. This work focused on the development of a polydopamine (PDA) and poly(sulfobetaine methacrylate) (PSBMA) co-deposition coating on Ti substrates. The coating contained copper ions, iron ions, and catechol groups, which coordinated to assemble bimetal-phenolic networks (bMPNs). Digital imaging, SEM, AFM, XPS, water contact angle, and film thickness tests confirmed the success of the modification. The antibacterial properties of the coating were evaluated using Gram-positive Staphylococcus aureus, while the cytotoxicity of the coating on human umbilical vein endothelial cells was also examined. The results demonstrated an excellent improvement in hydrophilicity, antibacterial properties, and benign biocompatibility of the coated Ti substrate, making it suitable for bioimplants and medical devices.

Laser Surface Texturing: Characteristics and Applications

Abstract Laser surface texturing (LST) has emerged as a versatile and efficient technique for modifying surface properties across various materials. This paper provides an analysis of the characteristics and diverse applications of laser surface texturing. The paper begins by explaining the fundamental principles underlying LST, highlighting the mechanisms involved in material interaction and the resultant surface modifications. It explores the influence of laser parameters such as pulse duration, energy density, and wavelength on the texturing process, emphasizes their impact on surface morphology, roughness, and topographical features. Furthermore, this paper delves into the wideranging applications of LST across different industries and fields. It examines how LST enhances surface functionalities, including improvements in tribological properties, wettability, friction reduction, and biocompatibility. Additionally, the utilization of LST for creating microstructures enabling advanced functionalities in optics, electronics, biomedical devices, and energy harvesting systems is discussed. Moreover, the challenges and future directions in LST technology are highlighted, which encompass advances in precision, scalability, and integration of LST with other manufacturing processes. The potential environmental implications and economic feasibility of LST are also discussed. In summary, this paper examines the characteristics, applications, challenges, and future prospects of laser surface texturing, showcasing its significance as a promising technology for tailoring surface properties across diverse materials and industries.

Research progress of metal-based additive manufacturing in medical implants

Abstract Metal-based additive manufacturing has gained significant attention in the field of medical implants over the past decade. The application of 3D-printing technology in medical implants offers several advantages over traditional manufacturing methods, including increased design flexibility for implant customization, reduced lead time for emergency cases, and the ability to create complex geometry shapes for patient-specific implants. In this review study, the working principles and conditions of metal 3D-printing technologies such as selective laser sintering, selective laser melting, and electron beam melting, as well as their applications and advantages in the medical field, are investigated in detail. The application scenarios and research status of non-degradable metals including titanium alloy, medical stainless steel, etc., and degradable metals like magnesium alloy are introduced as printing materials. We discuss the improvement of mechanical properties and biocompatibility of implants through surface modification, porous structure design, and the optimization of molding processes. Finally, the biocompatibility issues and challenges caused by the accuracy of CT imaging, fabrication, implant placement, and other aspects are summarized.

Novel Hybrid Silver-Silica Nanoparticles Synthesized by Modifications of the Sol-Gel Method and Their Theranostic Potential in Cancer.

Cancer is one of the leading causes of death worldwide. Conventional therapies lack selectivity and suffer from toxicity and drug resistance, leading to metastasis. To overcome these limitations, a new category of nanomaterials exploiting the tumor characteristics has been developed in cancer nanotherapeutics. Among them, pH, metabolism, and the disrupted architecture of cells can be exploited for theranostic applications. Such nanomaterials can be inorganic nanoparticles with silver ones and gain high attention as diagnostic, therapeutic, and antibacterial compounds. Silver has been linked with triggering the death of cancer cells via DNA damage due to the production of reactive oxygen species (ROS) during photodynamic therapy. Thus, improvement of biocompatibility, modification with targeted agents, and drug conjugation promote the use of silver nanoparticles. In this work, we managed to synthesize hybrid Ag@SiO2 core-shell nanoparticles via a modified sol-gel method by tackling the known etching of silver caused by ammonia by employing different bases of the sol-gel reaction. The bases used in the synthetic route were diethylamine (DEA) and triethylamine (TEA) and were monitored with silver nanoparticles individually from the absorbance peak of silver in the UV-vis region, showing no etching of silver in contrast with ammonia, which is usually used in the sol-gel method. Furthermore, we synthesized biocompatible nanoparticles with anticancer and diagnostic properties toward breast cancer cells and glioblastoma cells. The nanoparticles were characterized both structurally and morphologically. Their biological evaluation suggests minor toxicity toward healthy cells and red blood cells (RBCs). Also, the diagnostic potential of the hybrid nanoparticles was exploited by optical fluorescence microscopy. Therefore, we strongly suggest the investigation of such nanostructures as a dual platform for the diagnosis and therapy of cancer.

4D-Printable Photocrosslinkable Polyurethane-Based Inks for Tissue Scaffold and Actuator Applications.

4D printing recently emerges as an exciting evolution of conventional 3D printing, where a printed construct can quickly transform in response to a specific stimulus to switch between a temporary variable state and an original state. In this work, a photocrosslinkable polyethylene-glycol polyurethane ink is synthesized for light-assisted 4D printing of smart materials. The molecular weight distribution of the ink monomers is tunable by adjusting the copolymerization reaction time. Digital light processing (DLP) technique is used to program a differential swelling response in the printed constructs after humidity variation. Bioactive microparticles are embedded into the ink and the improvement of biocompatibility of the printed constructs is demonstrated for tissue engineering applications. Cell studies reveal above 90% viability in 1 week and ≈50% biodegradability after 4 weeks. Self-folding capillary scaffolds, dynamic grippers, and film actuators are made and activated in a humid environment. The approach offers a versatile platform for the fabrication of complex constructs. The ink can be used in tissue engineering and actuator applications, making the ink a promising avenue for future research.

Surface modification by pre-adsorption of proteins and polypeptides on Ti substrate with controlled hydrophilicity to improve biocompatibility

The water contact angle (WCA) value of the Ti substrate surfaces was successfully controlled to high hydrophilicity (≤ 20 deg.) by the treatment of UV light irradiation, atmospheric plasma or hydrothermal treatment, and stored in different environments to control the variation in WCA over time. Proteins with various molecular mass were used to investigate the protein adsorption on the Ti substrate controlled WCA. ATR-FTIR was employed to quantify the protein adsorption amount. It was found that all proteins had relatively higher adsorption amount on superhydrophilic surface. The adsorption amount of proteins was similar under the same WCA value. PEGs, as organic molecules without peptide bonds, was unable to be adsorbed on Ti with WCA < 60 deg., while can be adsorbed only on the hydrophobic surfaces with WCA > 90 deg. In particular, we have carried out in vivo tests upon the protein pre-adsorbed Ti specimens. The in vivo tests indicated that the Ti substrate which pre-adsorbed proteins with high molecular mass had much higher osteoconductivity than that without protein adsorption. On the other hand, the PEGs adsorbed substrates showed no effect on osteoconductivity enhancement. This was due to its lack of peptide bonds. It was considered that implants adsorbed polypeptides can greatly enhance the osseointegration, regardless the mass and type of molecules. In general, the adsorption of protein and polypeptide containing amino acid is an effective way to improve osseointegration, before implantation into body environment. It provides crucial guidance to the biocompatibility improvement of the metallic bone implant materials.

Development of Gelatin Methacryloyl/Sodium Alginate Interpenetrating Polymer Network Hydrogels for Bone Regeneration by Activating the Wnt/β-Catenin Signaling Pathway via Lithium Release.

Hydrogels have gained significant attention as biomaterials due to their remarkable properties resembling those of the extracellular matrix (ECM). In the present investigation, we successfully synthesized interpenetrating polymer network (IPN) hydrogels using gelatin methacryloyl (GelMA) and sodium alginate (SA), incorporating various concentrations of lithium chloride (LiCl; 0, 5, and 10 mM), aiming to develop a hydrogel scaffold for bone regeneration. Notably, the compressive modulus of the IPN hydrogels remained largely unaffected upon the inclusion of LiCl. However, the hydrogel with the high concentration of LiCl exhibited reduced fragmentation after compression testing. Intriguingly, we observed a significant improvement in cellular biocompatibility, primarily attributed to activation of the Wnt/β-catenin signaling pathway induced by LiCl. Subsequently, we evaluated the efficacy of the newly developed IPN-Li hydrogels in a rat cranial defect model and found that they substantially enhanced bone regeneration. Nevertheless, it is important to note that the introduction of high concentrations of LiCl did not significantly promote osteogenesis. This outcome can be attributed to the excessive release of Li+ ions into the extracellular matrix, hindering the desired effect. Overall, the IPN-Li hydrogel developed in this study holds great promise as a biodegradable material for bone regeneration applications.

Improvement in 316L steel surface features, corrosion and biocompatibility through novel CNT-assisted hydroxyapatite powder mixed-EDM process

Improvement in 316L steel surface features, corrosion and biocompatibility through novel CNT-assisted hydroxyapatite powder mixed-EDM process

Promote Osseointegration Through Surface Functionalization of Ti-Zr Alloy by Nano Composite Fiber

Using bioactive and biocompatible coatings to biofunctionalized metallic implant surfaces for enhanced bone regeneration while resisting bacterial infection has attracted materials scientists' interest. Bio-metallic Ti-25Zr disc sample was prepared using powder metallurgy and then coated using an electrospinning method to form a nanocomposite fiber as a coating layer over the surface of the metal alloy substrate. Three nano-compounds (Nano-hydroxyapatite, Nano-Titanium dioxide, Nano-strontium titanite) were added individually to the Polycaprolactone/Chitosan blend to prepare the electrospinning solutions. The results show a significant improvement in biocompatibility for the coated samples after seven days of (MC3T3-E1) cell culture. Cell viability percentages were significantly higher for the coated samples compared to uncoated ones, with values of PCL/Chitosan/nHA (HA1) has 239.45±17.95%, PCL/Chitosan/nSrTiO3 (SR1) has170.09±8.12%, and PCL/Chitosan/nTiO2 (TI1) has 117.19±19.42%, while bare Ti-25Zr has 80.52±1.97%. Cell proliferation also shows a remarkable increase with time for coated samples, and the enhancement reaches 197.76% for (HA1), 111.38% (SR1), and 45.81 % (TI1) in comparison with (bare Ti-25Zr). For the antibacterial test, no inhibition zone for the control sample (bare Ti-25Zr) was observed, while the coated samples showed a suitable and comparable inhibition zone. The coating procedure is simple and inexpensive, and composite nano-fiber has high biocompatibility and promise in orthodontic and orthopedic bone regeneration.

Chronic stability of a neuroprosthesis comprising multiple adjacent Utah arrays in monkeys

Objective. Electrical stimulation of visual cortex via a neuroprosthesis induces the perception of dots of light (‘phosphenes’), potentially allowing recognition of simple shapes even after decades of blindness. However, restoration of functional vision requires large numbers of electrodes, and chronic, clinical implantation of intracortical electrodes in the visual cortex has only been achieved using devices of up to 96 channels. We evaluated the efficacy and stability of a 1024-channel neuroprosthesis system in non-human primates (NHPs) over more than 3 years to assess its suitability for long-term vision restoration. Approach. We implanted 16 microelectrode arrays (Utah arrays) consisting of 8 × 8 electrodes with iridium oxide tips in the primary visual cortex (V1) and visual area 4 (V4) of two sighted macaques. We monitored the animals’ health and measured electrode impedances and neuronal signal quality by calculating signal-to-noise ratios of visually driven neuronal activity, peak-to-peak voltages of the waveforms of action potentials, and the number of channels with high-amplitude signals. We delivered cortical microstimulation and determined the minimum current that could be perceived, monitoring the number of channels that successfully yielded phosphenes. We also examined the influence of the implant on a visual task after 2–3 years of implantation and determined the integrity of the brain tissue with a histological analysis 3–3.5 years post-implantation. Main results. The monkeys remained healthy throughout the implantation period and the device retained its mechanical integrity and electrical conductivity. However, we observed decreasing signal quality with time, declining numbers of phosphene-evoking electrodes, decreases in electrode impedances, and impaired performance on a visual task at visual field locations corresponding to implanted cortical regions. Current thresholds increased with time in one of the two animals. The histological analysis revealed encapsulation of arrays and cortical degeneration. Scanning electron microscopy on one array revealed degradation of IrOx coating and higher impedances for electrodes with broken tips. Significance. Long-term implantation of a high-channel-count device in NHP visual cortex was accompanied by deformation of cortical tissue and decreased stimulation efficacy and signal quality over time. We conclude that improvements in device biocompatibility and/or refinement of implantation techniques are needed before future clinical use is feasible.