Carbon Dots Derived from Non-Biomass Waste: Methods, Applications, and Future Perspectives.

Carbon dots (CDs) are luminescent carbon nanoparticles with significant potential in analytical sensing, biomedicine, and energy regeneration due to their remarkable optical, physical, biological, and catalytic properties. In light of the enduring ecological impact of non-biomass waste that persists in the environment, efforts have been made toward converting non-biomass waste, such as ash, waste plastics, textiles, and papers into CDs. This review introduces non-biomass waste carbon sources and classifies them in accordance with the 2022 Australian National Waste Report. The synthesis approaches, including pre-treatment methods, and the properties of the CDs derived from non-biomass waste are comprehensively discussed. Subsequently, we summarize the diverse applications of CDs from non-biomass waste in sensing, information encryption, LEDs, solar cells, and plant growth promotion. In the final section, we delve into the future challenges and perspectives of CDs derived from non-biomass waste, shedding light on the exciting possibilities in this emerging area of research.

Chlorine Gas Sensor with Surface Temperature Control.

The work describes the design, manufacturing, and user interface of a thin-film gas transducer platform that is able to provide real-time detection of toxic vapor. This proof-of-concept system has applications in the field of real-time detection of hazardous gaseous agents that are harmful to the person exposed to the environment. The small-size gas sensor allows for integration with an unmanned aerial vehicle, thus combining high-level mobility with the ability for the real-time detection of hazardous/toxic chemicals or use as a standalone system in industries that deal with harmful gaseous substances. The sensor was designed based on the ability of thin-film metal oxide sensors to detect chlorine gas in real time. Specifically, a concentration of 10 ppm of Cl2 was tested.

Effect of nanocomposite coating and biomolecule functionalization on silk fibroin based conducting 3D braided scaffolds for peripheral nerve tissue engineering.

In this work, the effects of carbon nanofiber (CNF) dispersed poly-ε-caprolactone (PCL) nanocomposite coatings and biomolecules functionalization on silk fibroin based conducting braided nerve conduits were studied for enhancing Neuro 2a cellular activities. A unique combination of biomolecules (UCM) and varying concentrations of CNF (5, 7.5, 10% w/w) were dispersed in 10% (w/v) PCL solution for coating on degummed silk threads. The coated silk threads were braided to develop the scaffold structure. As the concentration of CNF increased in the coating, the electrical impedance decreased up to 400 Ω indicating better conductivity. The tensile and dynamic mechanical property analysis showed better mechanical properties in CNF coated samples. In vitro cytocompatibility analysis proved the non-toxicity of the developed braided conduits. Cell attachment, growth and proliferation were significantly enhanced on the biomolecule functionalized nanocomposite coated silk braided structure, exhibiting their potential for peripheral nerve regeneration and recovery.

Nanodiamond Fabrication of Superhydrophilic Wool Fabrics.

Nanodiamonds (ND) have been gaining impetus in fields such as medicine and electronics. ND has been widely used to modify polymer surfaces and composites for improved functionality. However, there have been limited research on ND application in regard to textile substrates. In this study, we presented a sustainable coating method, adapted to functionalized ND particles that would be coated onto wool fabric surfaces to enhance hydrophilicity. The application of an ND coating was found to increase wool hydrophilicity because of the presence of additional polar groups, shown by Fourier transform infrared spectrometry, which increased surface energy and fiber roughness. Scanning electron microscopy images revealed that the polar ND-coated wool scales demonstrated improved fiber hydrophilicity. Water absorbency, wicking, and contact angle results for coated fabrics confirmed significant improvement in hydrophilicity, which was directly related to the concentration of ND particles. The optimal concentration of ND was therefore selected to coat the wool fabric. Furthermore, tensile strength and abrasion resistance of the coated fabrics were increased due to the exceptional mechanical properties of ND.

Fabrication of Nanocomposites with High Elasticity and Strength for the Load-Bearing Layer of Small-Diameter Vascular Grafts.

Compliance mismatch of commercially available artificial grafts, where the artificial graft and the native vessel are subject to different radial expansions, is a major issue that results in graft occlusion after implantation. A human artery possesses a nonlinear mechanical response to pulsatile pressure due to its nonlinear viscoelastic nature, which is difficult to replicate in artificial graft fabrication. Here, we fabricated nanocomposites with nonlinear mechanical responses for potential application as the load-bearing layer of vascular grafts, based on a poly(dimethylsiloxane) (PDMS)-casted nanofibrous film. The nanofibers consisted of a core-sheath structure with a PDMS elastomer reinforced with poly(methyl methacrylate) (PMMA) nanofibers as the sheath and thermoplastic polyurethane (TPU) elastomer as the core. The surface morphology and chemical composition together with the crystalline structure of the nanocomposites were characterized, and dynamic mechanical analysis was performed to select the graft with the most suitable properties as the load-bearing layer of a small-diameter vascular graft. The presence of the stiff polymer PMMA and elastic polymer TPU in the PMMA/PDMS/TPU combination resulted in a delayed dissipation of energy after exposure to a force corresponding to 180 mm Hg. Casting the PDMS/PMMA/TPU nanofibrous mat into a nanocomposite film improved the ultimate tensile strength of PDMS without compromising its elasticity. The compliance values of the nanocomposites were also found to be a close match to those of the greater saphenous vein, demonstrating a great potential of the nanocomposites as the load-bearing layer in a biostable vascular graft.

Review on electrically conductive smart nerve guide conduit for peripheral nerve regeneration.

At present, peripheral nerve injuries (PNIs) are one of the leading causes of substantial impairment around the globe. Complete recovery of nerve function after an injury is challenging. Currently, autologous nerve grafts are being used as a treatment; however, this has several downsides, for example, donor site morbidity, shortage of donor sites, loss of sensation, inflammation, and neuroma development. The most promising alternative is the development of a nerve guide conduit (NGC) to direct the restoration and renewal of neuronal axons from the proximal to the distal end to facilitate nerve regeneration and maximize sensory and functional recovery. Alternatively, the response of nerve cells to electrical stimulation (ES) has a substantial regenerative effect. The incorporation of electrically conductive biomaterials in the fabrication of smart NGCs facilitates the function of ES throughout the active proliferation state. This article overviews the potency of the various categories of electroactive smart biomaterials, including conductive and piezoelectric nanomaterials, piezoelectric polymers, and organic conductive polymers that researchers have employed latterly to fabricate smart NGCs and their potentiality in future clinical application. It also summarizes a comprehensive analysis of the recent research and advancements in the application of ES in the field of NGC.

Fast and Effective Removal of Congo Red by Doped ZnO Nanoparticles.

ZnO nanoparticles (NPs) show remarkable efficiency in removing various contaminants from aqueous systems. Doping ZnO NPs with a second metal element can dramatically change the physicochemical properties of the pristine nanoparticles. However, there have been limited reports on the absorption of doped ZnO NPs, especially comparing the performance of ZnO NPs with different doping elements. Herein, ZnO NPs were doped with three transitional metals (Co, Fe, and Mn) at a nominal 2 wt.%. The particle surface had a higher dopant concentration than the interior for all NPs, implying the migration of the dopants to the surface. Because doping atoms inhibited grain growth, the doped ZnO NPs had a small particle size and a large surface area. The adsorption performance followed the order of Fe-doped < undoped < Mn-doped < Co-doped ZnO. Co-doped ZnO had an increased surface area and less tendency to agglomerate in an aqueous solution, showing the best adsorption performance. The adsorption of Congo red (CR) on Co-doped ZnO followed the pseudo-second-order model and the Langmuir isotherm. The adsorption process was spontaneous through monolayer chemisorption, and the maximum adsorption capacity was 230 mg/g. Finally, the Co-doped ZnO was successfully incorporated into an alginate membrane by electrospinning. The membrane demonstrated excellent adsorption performance and had great potential as an innovative and low-cost adsorbent (inexpensive raw materials and simple processing) for wastewater purification.

Advanced flexible transvaginal mesh with high visibility under computerized tomography (CT) scan.

Pelvic floor disorders, including pelvic organ prolapse (POP) and stress urinary incontinence (SUI), are serious and very common. Surgery is commonly undertaken to restore the strength of the vaginal wall using transvaginal surgical mesh (TVM). However, up to 15% of TVM implants result in long-term complications, including pain, recurrent symptoms, and infection.Clinical Relevance- In this study, a new bioengineered TVM has been developed to address these issues. The TVM is visible using noninvasive imaging techniques such as computed tomography (CT); it has a highly similar structural profile to human tissue and potential to reduce pain and inflammation. These combined technological advances have the potential to revolutionize women's health.

Review of Polymeric Biomimetic Small-Diameter Vascular Grafts to Tackle Intimal Hyperplasia.

Small-diameter artificial vascular grafts (SDAVG) are used to bypass blood flow in arterial occlusive diseases such as coronary heart or peripheral arterial disease. However, SDAVGs are plagued by restenosis after a short while due to thrombosis and the thickening of the neointimal wall known as intimal hyperplasia (IH). The specific causes of IH have not yet been deduced; however, thrombosis formation due to bioincompatibility as well as a mismatch between the biomechanical properties of the SDAVG and the native artery has been attributed to its initiation. The main challenges that have been faced in fabricating SDAVGs are facilitating rapid re-endothelialization of the luminal surface of the SDAVG and replicating the complex viscoelastic behavior of the arteries. Recent strategies to combat IH formation have been mostly based on imitating the natural structure and function of the native artery (biomimicry). Thus, most recently, developed grafts contain a multilayered structure with a designated function for each layer. This paper reviews the current polymeric, biomimetic SDAVGs in preventing the formation of IH. The materials used in fabrication, challenges, and strategies employed to tackle IH are summarized and discussed, and we focus on the multilayered structure of current SDAVGs. Additionally, the future aspects in this area are pointed out for researchers to consider in their endeavor.

Liquid metal polymer composite: Flexible, conductive, biocompatible, and antimicrobial scaffold.

Gallium and its alloys, such as eutectic gallium indium alloy (EGaIn), a form of liquid metal, have recently attracted the attention of researchers due to their low toxicity and electrical and thermal conductivity for biomedical application. However, further research is required to harness EGaIn-composites advantages and address their application as a biomedical scaffold. In this research, EGaIn-polylactic acid/polycaprolactone composites with and without a second conductive filler, MXene, were prepared and characterized. The addition of MXene, into the EGaIn-composite, can improve the composite's electrochemical properties by connecting the liquid metal droplets resulting in electrically conductive continuous pathways within the polymeric matrix. The results showed that the composite with 50% EGaIn and 4% MXene, displayed optimal electrochemical properties and enhanced mechanical and radiopacity properties. Furthermore, the composite showed good biocompatibility, examined through interactions with fibroblast cells, and antibacterial properties against methicillin-resistant Staphylococcus aureus. Therefore, the liquid metal (EGaIn) polymer composite with MXene provides a first proof-of-concept engineering scaffold strategy with low toxicity, functional electrochemical properties, and promising antimicrobial properties.

Fluorescent Magnesium Hydroxide Nanosheet Bandages with Tailored Properties for Biocompatible Antimicrobial Wound Dressings and pH Monitoring.

Magnesium hydroxide (Mg(OH)2) is hailed as a cheap and biocompatible material with antimicrobial potential; however, research aimed at instilling additional properties and functionality to this material is scarce. In this work, we synthesized novel, fluorescent magnesium hydroxide nanosheets (Mg(OH)2-NS) with a morphology that closely resembles that of graphene oxide. These multifunctional nanosheets were employed as a potent antimicrobial agent against several medically relevant bacterial and fungal species, particularly on solid surfaces. Their strong fluorescence signature correlates to their hydroxide makeup and can therefore be used to assess their degradation and functional antimicrobial capacity. Furthermore, their pH-responsive change in fluorescence can potentially act as a pH probe for wound acidification, which is characteristic of healthy wound healing. These fluorescent antimicrobial nanosheets were stably integrated into biocompatible electrospun fibers and agarose gels to add functionality to the material. This reinforces the suitability of the material to be used as antimicrobial bandages and gels. The biocompatibility of the Mg(OH)2-NS for topical medical applications was supported by its noncytotoxic action on human keratinocyte (HaCaT) cells.

Nanodiamond-chitosan functionalized hernia mesh for biocompatibility and antimicrobial activity.

Polypropylene (PP) mesh is most commonly used for the treatment of hernia and pelvic floor construction. However, some of the patients have a few complications after surgery due to the rejection or infection of the implanted meshes. The poor biocompatibility of PP mesh, low wettability results in poor cell attachment/proliferation and restricts the loading of antibacterial agent, leading to a slow healing process and high risk of infection after surgery. Here in this study, a new technique has been employed to develop a novel antimicrobial and biocompatible PP mesh modified with bioactive chitosan and functionalized nanodiamond (FND) for infection inhibition and acceleration of the healing process. An oxygen plasma treatment PP mesh was used then chitosan was strongly attached to the surface of the PP fibers. Subsequently, FND as an antibacterial agent was loaded into the chitosan modified PP fiber to provide desired antibacterial functions. The meshes were characterised with XRD, FTIR, SEM, EDX, water contact angle, confocal, and optical microscopy. The modified PP mesh with chitosan and FND showed a significant increase in its hydrophilicity and L929 fibroblast cell attachment. Furthermore, the modified mesh exhibited great antibacterial efficiency against Escherichia coli. Therefore, the newly developed technique to modify PP mesh could be a promising technique to generate a biocompatible PP mesh to accelerate the healing process and reduce the risk of infection after surgery.

Single-Step Fabrication Method toward 3D Printing Composite Diamond-Titanium Interfaces for Neural Applications.

Owing to several key attributes, diamond is an attractive candidate material for neural interfacing electrodes. The emergence of additive-manufacturing (AM) of diamond-based materials has addressed multiple challenges associated with the fabrication of diamond electrodes using the conventional chemical vapor deposition (CVD) approach. Unlike the CVD approach, AM methods have enabled the deposition of three-dimensional diamond-based material at room temperature. This work demonstrates the feasibility of using laser metal deposition to fabricate diamond-titanium hybrid electrodes for neuronal interfacing. In addition to exhibiting a high electrochemical capacitance of 1.1 mF cm-2 and a low electrochemical impedance of 1 kΩ cm2 at 1 kHz in physiological saline, these electrodes exhibit a high degree of biocompatibility assessed in vitro using cortical neurons. Furthermore, surface characterization methods show the presence of an oxygen-rich mixed-phase diamond-titanium surface along the grain boundaries. Overall, we demonstrated that our unique approach facilitates printing biocompatible titanium-diamond site-specific coating-free conductive hybrid surfaces using AM, which paves the way to printing customized electrodes and interfacing implantable medical devices.

Multifunctional Sutures with Temperature Sensing and Infection Control.

The next-generation sutures should provide in situ monitoring of wound condition such as temperature while reducing surgical site infection during wound closure. In this study, functionalized nanodiamond (FND) and reduced graphene oxide (rGO) into biodegradable polycaprolactone (PCL) are incorporated to develop a new multifunctional suture with such capabilities. Incorporation of FND and rGO into PCL enhances its tensile strength by about 43% and toughness by 35%. The sutures show temperature sensing capability in the range of 25-40 °C based on the shift in zero-splitting frequency of the nitrogen-vacancy (NV- ) centers in FND via optically detected magnetic resonance, paving the way for potential detection of infection or excessive inflammation in healing wounds. The suture surface readily coats with antibiotics to reduce bacterial infection risk to the wounds. The new suture thus is promising in monitoring and supporting wound closure.

Nanodiamond in composite: Biomedical application.

The biocompatibility of materials is the determining factor for them to be applied in biomedical areas. Nanodiamond (ND) has gained increasing interest in this area due to its biocompatibility, ease of surface functionalization and excellent mechanical performance. ND has been widely used to reinforce biopolymers, and the resultant biocomposites have found applications in bone tissue engineering, chemotherapeutic drug delivery, and wound healing. Fluorescent ND, when combined with biopolymers, is serving for bioimaging and sensing applications. Herein, we contribute a description of ND, recent trends in its adoption for biopolymers, functionalization methods, amalgamation techniques of ND with biopolymers, potential applications of these composites in the biomedical field and future perspectives.

Nanocomposite-Coated Silk-Based Artificial Conduits: The Influence of Structures on Regeneration of the Peripheral Nerve.

In this study, silk filaments are coated with different concentrations (5, 7.5, and 10% w/w) of carbon nanofibers (CNFs) dispersed in poly-ε-caprolactone. The nanocomposite-coated silk filaments are subjected to knitting, braiding, and twisting. The tubular structures are covered with a silk fibroin/polyvinyl film for the nerve conduit application. Physical characterization of the developed nerve conduits demonstrates suitable mechanical properties comparable to native nerve tissue. Cell proliferation is confirmed through in vitro cell culture studies using Neuro 2a and rat primary cortical neural progenitor cells, which show that the proliferation happens along the interconnected macrochannels of the internal structure of the nerve conduit. The knitted structure presents better biological properties than the nerve conduits with other internal structures. The in vivo sciatic nerve implantation is performed in a rabbit model using the best conduit, i.e., 10% CNF-based nanocomposite-coated silk with a knitted inner structure without any biomolecules or tube filling gels. Regeneration of a 2 cm gap excised sciatic nerve is investigated by immunohistochemistry and histology of implanted nerve conduits removed after 30 days. Results suggest that the CNF-based conducting nanocomposite coating in this well-defined architecture of the conduit helps in signal transmission and neural growth during the regeneration of the transected nerve.

Three-dimensional directional nerve guide conduits fabricated by dopamine-functionalized conductive carbon nanofibre-based nanocomposite ink printing.

A potential issue in current nerve guides is that they do not transmit electrical nerve impulses between the distal and proximal end of an injured nerve, i.e. a synapse. Conductivity is a desirable property of an ideal nerve guide that is being considered for peripheral nerve regeneration. Most conductive polymers reported for the fabrication of tissue engineering scaffolds, such as polypyrrole and polyaniline, are non-biodegradable and possess weak mechanical properties, and thus cannot be fabricated into 3D structures. Herein, we have designed a new nanocomposite material composed of dopamine, carbon nanofibers (CNF) and polycaprolactone (PCL) for the fabrication of nerve conduits, which facilitates the growth and migration of neurons toward the targeted end of an injured nerve. This support and navigation of the scaffold leads to better sensory and motor function. The results showed that the mechanical properties of the printed PCL increased by 30% in comparison with the pure PCL film, which is comparable with human nerves. The in vitro cell study of human glioma cells showed that the printed lines provided support for neural cell attachment, migration and differentiation toward the targeted end. In contrast, in the absence of printed lines in the scaffold, the cells attach and grow in random directions, forming a flower shape (cell cluster) on the surface of PCL. Thus, the proposed scaffold is a promising candidate for nerve guide application based on its signal transmission and navigating neurons in a correct pathway towards the targeted end.

Correction: Three-dimensional directional nerve guide conduits fabricated by dopamine-functionalized conductive carbon nanofibre-based nanocomposite ink printing.

[This corrects the article DOI: 10.1039/D0RA06556K.].

Polypropylene-nanodiamond composite for hernia mesh.

Commercial hernia mesh is commonly made from polypropylene (PP), due to its inertness, biocompatibility, physical properties, ease of processing and versatility for conversion into flexible shape. However, reportedly hernia mesh prepared from PP experienced issues such as diminished long-term strength, foreign body rejection, lack of biocompatibility and high adhesion to the abdomen wall. Infiltration of the mesh by soft tissue (called remodeling) results in an integration of mesh into the body, leading to a rapid reduction in mesh mechanical properties and potential infection. Here, this study addresses these issues through the incorporation of nanodiamond (ND) into PP filament and coating on the surface of plasma-treated PP-ND mesh. The results show that the dynamic modulus of the PP-ND mesh increased significantly, without compromising its flexibility. Coating PP-ND mesh with hydroxylated ND led to a reduction in nonspecific protein adsorption onto the surface of nanocomposite, which is an important characteristic for hernia mesh to prevent foreign body reaction, attachment of mesh to the abdominal wall and nearby organs. In-vitro study with mammalian cells shows that coated PP-ND mesh with functionalized ND exhibits a significant increase in the number of adhered cells with more elongated morphology in comparison with other PP meshes, due to the better hydrophilicity. Therefore, the ND coated nanocomposite mesh can be a promising candidate for hernia repair in the future; however, more investigation is required.

Electrospun Nanodiamond-Silk Fibroin Membranes: A Multifunctional Platform for Biosensing and Wound-Healing Applications.

Next generation wound care technology capable of diagnosing wound parameters, promoting healthy cell growth, and reducing pathogenic infections noninvasively would provide patients with an improved standard of care and accelerated wound repair. Temperature is one of the indicating biomarkers specific to chronic wounds. This work reports a hybrid, multifunctional optical material platform-nanodiamond (ND)-silk membranes as biopolymer dressings capable of temperature sensing and promoting wound healing. The hybrid structure was fabricated through electrospinning, and 3D submicron fibrous membranes with high porosity were formed. Silk fibers are capable of compensating for the lack of an extracellular matrix at the wound site, supporting the wound-healing process. Negatively charged nitrogen vacancy (NV-) color centers in NDs exhibit optically detected magnetic resonance (ODMR) and act as nanoscale thermometers. This can be exploited to sense temperature variations associated with the presence of infection or inflammation in a wound, without physically removing the dressing. Our results show that the presence of NDs in the hybrid ND-silk membranes improves the thermal stability of silk fibers. NV- color centers in NDs embedded in silk fibers exhibit well-retained fluorescence and ODMR. Using the NV- centers as fluorescent nanoscale thermometers, we achieved temperature sensing in 25-50 °C, including the biologically relevant temperature window, for cell-grown ND-silk membranes. An enhancement (∼1.5× on average) in the temperature sensitivity of the NV- centers was observed for the hybrid materials. The hybrid membranes were further tested in vivo in a murine wound-healing model and demonstrated biocompatibility and equivalent wound closure rates as the control wounds. Additionally, the hybrid ND-silk membranes exhibited selective antifouling and biocidal propensity toward Gram-negative Pseudomonas aeruginosa and Escherichia coli, while no effect was observed on Gram-positive Staphylococcus aureus.