Vertically Aligned Carbon Nanotubes as a Unique Material for Biomedical Applications

Field Emission Properties of Cu-Filled Vertically Aligned Carbon Nanotubes Grown Directly on Thin Cu Foils

Copper-filled vertically aligned carbon nanotubes (Cu@VACNTs) were grown directly on Cu foil substrates of 0.1 mm thicknesses at different temperatures via plasma-enhanced chemical vapor deposition (PECVD). By circumventing the need for additional catalyst layers or intensive substrate treatments, our in-situ technique offers a simplified and potentially scalable route for fabricating Cu@VACNTs with enhanced electrical and thermal properties on thin Cu foils. Comprehensive analysis using field emission scanning microscopy (FESEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) mappings, and X-ray diffraction (XRD) revealed uniform Cu filling within the VACNTs across a range of synthesis temperatures (650 °C, 700 °C, and 760 °C). Field emission (FE) measurements of the sample synthesized at 700 °C (S700) showed low turn-on and threshold fields of 2.33 V/μm and 3.29 V/μm, respectively. The findings demonstrate the viability of thin Cu substrates in creating dense and highly conductive Cu-filled VACNT arrays for advanced electronic and nanoelectronics applications.

Chemodynamic PtMn Nanocubes for Effective Photothermal ROS Storm a Key Anti-Tumor Therapy in-vivo

Background

Chemodynamic therapy (CDT) is a new treatment approach that is triggered by endogenous stimuli in specific intracellular conditions for generating hydroxyl radicals. However, the efficiency of CDT is severely limited by Fenton reaction agents and harsh reaction conditions.

Methods

Bimetallic PtMn nanocubes were rationally designed and simply synthesized through a one-step high-temperature pyrolysis process by controlling both the nucleation process and the subsequent crystal growth stage. The polyethylene glycol was modified to enhance biocompatibility.

Results

Benefiting from the alloying of Pt nanocubes with Mn doping, the structure of the electron cloud has changed, resulting in different degrees of the shift in electron binding energy, resulting in the increasing of Fenton reaction activity. The PtMn nanocubes could catalyze endogenous hydrogen peroxide to toxic hydroxyl radicals in mild acid. Meanwhile, the intrinsic glutathione (GSH) depletion activity of PtMn nanocubes consumed GSH with the assistance of Mn3+/Mn2+. Upon 808 nm laser irradiation, mild temperature due to the surface plasmon resonance effect of Pt metal can also enhance the Fenton reaction.

Conclusion

PtMn nanocubes can not only destroy the antioxidant system via efficient reactive oxygen species generation and continuous GSH consumption but also propose the photothermal effect of noble metal for enhanced Fenton reaction activity.

Hyaluronic Acid-Based Reactive Oxygen Species-Responsive Multifunctional Injectable Hydrogel Platform Accelerating Diabetic Wound Healing

Diabetic wounds are more likely to develop into complex and severe chronic wounds. The objective of this study is to develop and assess a reactive oxygen species (ROS)-responsive multifunctional injectable hydrogel for the purpose of diabetic wound healing. A multifunctional hydrogel (HA@Cur@Ag) is successfully synthesized with dual antioxidant, antibacterial, and anti-inflammatory properties by crosslinking thiol hyaluronic acid (SH-HA) and disulfide-bonded hyperbranched polyethylene glycol (HB-PBHE) through Michael addition; while, incorporating curcumin liposomes and silver nanoparticles (AgNPs). The HA@Cur@Ag hydrogel exhibits favorable biocompatibility, degradability, and injectivity. The outcomes of in vitro and in vivo experiments demonstrate that the hydrogel can effectively be loaded with and release curcumin liposomes, as well as silver ions, thereby facilitating diabetic wound healing through multiple mechanisms, including ROS scavenging, bactericidal activity, anti-inflammatory effects, and the promotion of angiogenesis. Transcriptome sequencing reveals that the HA@Cur@Ag hydrogel effectively suppresses the activation of the tumour necrosis factor (TNF)/nuclear factor κB (NF-κB) pathway to ameliorate oxidative stress and inflammation in diabetic wounds. These findings suggest that this ROS-responsive multifunctional injectable hydrogel, which possesses the ability to precisely coordinate and integrate intricate biological and molecular processes involved in wound healing, exhibits notable potential for expediting diabetic wound healing.

Development and evaluation of a protease inhibitor antiretroviral drug-loaded carbon nanotube delivery system for enhanced efficacy in HIV treatment

The primary objective of this study was to enhance the effectiveness of the protease inhibitor antiretroviral drug by designing a novel delivery system using carboxylated multiwalled carbon nanotubes (COOH-MWCNTs). To achieve this, Fosamprenavir calcium (FPV), a prodrug of amprenavir known for inhibiting the proteolytic cleavage of immature virions, was selected as the protease inhibitor antiretroviral drug, and loaded onto COOH-MWCNTs using a direct loading method. The structural specificity of the drug-loaded MWCNTs, the percent entrapment efficiency, and in vitro drug release were rigorously evaluated for the developed formulation, referred to as FPV-MWCNT. Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and atomic force microscopy (AFM) techniques were employed to confirm the structural integrity and specificity of the FPV-MWCNT formulation. The results demonstrated a remarkable entrapment efficiency of 79.57 ± 0.4 %, indicating the successful loading of FPV onto COOH-MWCNTs. FE-SEM and AFM analyses further confirmed the well-dispersed and elongated structure of the FPV-MWCNT formulation, without any signs of fracture, ensuring the stability and integrity of the drug delivery system. Moreover, particle size analysis revealed an average size of 290.1 nm, firmly establishing the nanoscale range of the formulation, with a zeta potential of 0.230 mV, signifying the system's colloidal stability. In vitro drug release studies conducted in methanolic phosphate buffer saline (PBS) at pH 7.4 and methanolic acetate buffer at pH 5 demonstrated sustained drug release from the FPV-MWCNT formulation. Over a period of 96 h, the formulation exhibited a cumulative drug release of 91.43 ± 2.3 %, showcasing the controlled and sustained release profile. Furthermore, hemolysis studies indicated a notable reduction in the toxicity of both FPV and MWCNT upon conjugation, although the percent hemolysis increased with higher concentrations, suggesting the need for careful consideration of dosage levels. In conclusion, the findings from this study underscore the potential of the FPV-MWCNT formulation as an effective and promising drug-conjugated system for delivering antiretroviral drugs. The successful encapsulation, sustained drug release, and reduced toxicity make FPV-MWCNT a compelling candidate for enhancing the therapeutic efficacy of protease inhibitor antiretroviral drugs in the treatment of HIV. The developed delivery system holds great promise for future advancements in HIV treatment and paves the way for further research and development in the field of drug delivery utilizing carbon nanotube-based systems.

Artificial Periosteum with Oriented Surface Nanotopography and High Tissue Adherent Property

Massive periosteal defects often significantly impair bone regeneration and repair, which have become a major clinical challenge. Unfortunately, current engineered periosteal materials can hardly currently focus on achieving high tissue adhesion property, being suitable for cell growth, and inducing cell orientation concurrently to meet the properties of nature periosteum. Additionally, the preparation of oriented surface nanotopography often relies on professional equipment. In this study, inspired by the oriented collagen structure of nature periosteum, we present a composite artificial periosteum with a layer of oriented nanotopography surface containing carbon nanotubes (CNTs), cross-linked with adhesive polydopamine (PDA) hydrogel on both terminals. An oriented surface structure that can simulate the oriented alignment of periosteal collagen fibers can be quickly and conveniently obtained via a simple stretching of the membrane in a water bath. With the help of CNTs, our artificial periosteum exhibits sufficient mechanical strength and desired oriented nanotopological structure surface, which further induces the directional arrangement of human bone marrow mesenchymal stem cells (hBMSCs) on the membrane. These oriented hBMSCs express significantly higher levels of osteogenic genes and proteins, while the resultant composite periosteum can be stably immobilized in vivo in the rat model of massive calvarial defect through the PDA hydrogel, which finally shows promising bone regeneration ability. We anticipate that the developed functional artificial periosteum has great potential in biomedical applications for the treatment of composite defects of the bone and periosteum.

Customizing 3D Structures of Vertically Aligned Carbon Nanotubes to Direct Neural Stem Cell Differentiation

Neural tissue-related illnesses have a high incidence and prevalence in society. Despite intensive research efforts to enhance the regeneration of neural cells into functional tissue, effective treatments are still unavailable. Here, a novel therapeutic approach based on vertically aligned carbon nanotube forests (VA-CNT forests) and periodic VA-CNT micropillars produced by thermal chemical vapor deposition is explored. In addition, honeycomb-like and flower-like morphologies are created. Initial viability testing reveals that NE-4C neural stem cells seeded on all morphologies survive and proliferate. In addition, free-standing VA-CNT forests and capillary-driven VA-CNT forests are created, with the latter demonstrating enhanced capacity to stimulate neuritogenesis and network formation under minimal differentiation medium conditions. This is attributed to the interaction between surface roughness and 3D-like morphology that mimics the native extracellular matrix, thus enhancing cellular attachment and communication. These findings provide a new avenue for the construction of electroresponsive scaffolds based on CNTs for neural tissue engineering.

Programmable DNA Hydrogel Provides Suitable Microenvironment for Enhancing TSPCS Therapy in Healing of Tendinopathy

Tendon stem/progenitor cells (TSPCs) therapy is a promising strategy for enhancing cell matrix and collagen synthesis, and regulating the metabolism of the tendon microenvironment during tendon injury repair. Nevertheless, the barren microenvironment and gliding shear of tendon cause insufficient nutrition supply, damage, and aggregation of injected TSPCs around tendon tissues, which severely hinders their clinical application in tendinopathy. In this study, a TSPCs delivery system is developed by encapsulating TSPCs within a DNA hydrogel (TSPCs-Gel) as the DNA hydrogel offers an excellent artificial extracellular matrix (ECM) microenvironment by providing nutrition for proliferation and protection against shear forces. This delivery method restricts TSPCs to the tendons, significantly extending their retention time. It is also found that TSPCs-Gel injections can promote the healing of rat tendinopathy in vivo, where cross-sectional area and load to failure of injured tendons in rats are significantly improved compared to the free TSPCs treatment group at 8 weeks. Furthermore, the potential healing mechanism of TSPCs-Gel is investigated by RNA-sequencing to identify a series of potential gene and signaling pathway targets for further clinical treatment strategies. These findings suggest the potential pathways of using DNA hydrogels as artificial ECMs to promote cell proliferation and protect TSPCs in TSPC therapy.

Plasma-Etched Vertically Aligned CNTs with Enhanced Antibacterial Power

The emergence of multidrug-resistant bacteria represents a growing threat to public health, and it calls for the development of alternative antibacterial approaches not based on antibiotics. Here, we propose vertically aligned carbon nanotubes (VA-CNTs), with a properly designed nanomorphology, as effective platforms to kill bacteria. We show, via a combination of microscopic and spectroscopic techniques, the ability to tailor the topography of VA-CNTs, in a controlled and time-efficient manner, by means of plasma etching processes. Three different varieties of VA-CNTs were investigated, in terms of antibacterial and antibiofilm activity, against Pseudomonas aeruginosa and Staphylococcus aureus: one as-grown variety and two varieties receiving different etching treatments. The highest reduction in cell viability (100% and 97% for P. aeruginosa and S. aureus, respectively) was observed for the VA-CNTs modified using Ar and O₂ as an etching gas, thus identifying the best configuration for a VA-CNT-based surface to inactivate both planktonic and biofilm infections. Additionally, we demonstrate that the powerful antibacterial activity of VA-CNTs is determined by a synergistic effect of both mechanical injuries and ROS production. The possibility of achieving a bacterial inactivation close to 100%, by modulating the physico-chemical features of VA-CNTs, opens up new opportunities for the design of self-cleaning surfaces, preventing the formation of microbial colonies.

Carbon dioxide-boosted growth of high-density and vertically aligned carbon nanotube arrays on a stainless steel mesh

Vertically aligned carbon nanotubes (VACNTs), a unique group of highly aligned CNTs normal to a substrate, have been extensively studied during the past decades. However, it is a long-standing challenge to improve the height of VACNTs due to the incidental deactivation of catalysts during growth. Herein, we demonstrate a facile strategy toward synthesizing high-density and well-aligned CNT arrays from in situ formed Fe-based catalysts on a stainless steel (SS) mesh. These catalysts were generated by direct oxidation-reduction treatment to the SS, which had excellent adhesion on the mesh substrate, and thus suppressed catalyst aggregation and promoted CNT growth under the flow of C₂H₂. In particular, by feeding additional CO₂ at an optimal rate, the height of CNT arrays could be boosted from ca. 15 μm to ca. 80.0 μm, one of the highest heights observed for VACNTs on SS-based substrates so far. This is attributed to the prolonged activity of the catalysts by CO₂ induced removal of extra carbon. Our study might provide an insight into the development of efficient strategies for VACNT growth on conductive substrates.

Distribution of Iron Nanoparticles in Arrays of Vertically Aligned Carbon Nanotubes Grown by Chemical Vapor Deposition

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene-toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20-30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe₃C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated.

Review of Flexible Wearable Sensor Devices for Biomedical Application

With the development of cross-fertilisation in various disciplines, flexible wearable sensing technologies have emerged, bringing together many disciplines, such as biomedicine, materials science, control science, and communication technology. Over the past few years, the development of multiple types of flexible wearable devices that are widely used for the detection of human physiological signals has proven that flexible wearable devices have strong biocompatibility and a great potential for further development. These include electronic skin patches, soft robots, bio-batteries, and personalised medical devices. In this review, we present an updated overview of emerging flexible wearable sensor devices for biomedical applications and a comprehensive summary of the research progress and potential of flexible sensors. First, we describe the selection and fabrication of flexible materials and their excellent electrochemical properties. We evaluate the mechanisms by which these sensor devices work, and then we categorise and compare the unique advantages of a variety of sensor devices from the perspective of in vitro and in vivo sensing, as well as some exciting applications in the human body. Finally, we summarise the opportunities and challenges in the field of flexible wearable devices.

Magnetic-Powered Janus Cell Robots Loaded with Oncolytic Adenovirus for Active and Targeted Virotherapy of Bladder Cancer

A unique robotic medical platform is designed by utilizing cell robots as the active "Trojan horse" of oncolytic adenovirus (OA), capable of tumor-selective binding and killing. The OA-loaded cell robots are fabricated by entirely modifying OA-infected 293T cells with cyclic arginine-glycine-aspartic acid tripeptide (cRGD) to specifically bind with bladder cancer cells, followed by asymmetric immobilization of Fe₃ O₄ nanoparticles (NPs) on the cell surface. OA can replicate in host cells and induce cytolysis to release the virus progeny to the surrounding tumor sites for sustainable infection and oncolysis. The asymmetric coating of magnetic NPs bestows the cell robots with effective movement in various media and wireless manipulation with directional migration in a microfluidic device and bladder mold under magnetic control, further enabling steerable movement and prolonged retention of cell robots in the mouse bladder. The biorecognition of cRGD and robust, controllable propulsion of cell robots work synergistically to greatly enhance their tissue penetration and anticancer efficacy in the 3D cancer spheroid and orthotopic mouse bladder tumor model. Overall, this study integrates cell-based microrobots with virotherapy to generate an attractive robotic system with tumor specificity, expanding the operation scope of cell robots in biomedical community.

Nanosafety Analysis of Graphene-Based Polyester Resin Composites on a Life Cycle Perspective

The use, production, and disposal of engineering nanomaterials (ENMs), including graphene-related materials (GRMs), raise concerns and questions about possible adverse effects on human health and the environment, considering the lack of harmonized toxicological data on ENMs and the ability of these materials to be released into the air, soil, or water during common industrial processes and/or accidental events. Within this context, the potential release of graphene particles, their agglomerates, and aggregates (NOAA) as a result of sanding of a battery of graphene-based polyester resin composite samples intended to be used in a building was examined. The analyzed samples were exposed to different weathering conditions to evaluate the influence of the weathering process on the morphology and size distribution of the particles released. Sanding studies were conducted in a tailored designed sanding bench connected to time and size resolving measurement devices. Particle size distributions and particle number concentration were assessed using an optical particle counter (OPC) and a condensation particle counter (CPC), respectively, during the sanding operation. A scanning electron microscope/energy dispersive X-ray (SEM/EDX) analysis was performed to adequately characterize the morphology, size, and chemical composition of the released particles. A toxicity screening study of pristine and graphene-based nanocomposites released using the aquatic macroinvertebrate Daphnia magna and relevant human cell lines was conducted to support risk assessment and decision making. The results show a significant release of nanoscale materials during machining operations, including differences attributed to the % of graphene and weathering conditions. The cell line tests demonstrated a higher effect in the human colon carcinoma cell line Caco2 than in the human fibroblasts (A549 cell line), which means that composites released to the environment could have an impact on human health and biota.