Nanodiamonds for nanomedicine

Palladium-reduced graphene oxide nanocomposites enhance neurite outgrowth and protect neurons from Ishemic stroke

Currently, the construction of novel biomimetic reduced graphene oxide (RGO)-based nanocomposites to induce neurite sprouting and repair the injured neurons represents a promising strategy in promoting neuronal development or treatment of cerebral anoxia or ischemia. Here, we present an effective method for constructing palladium-reduced graphene oxide (Pd-RGO) nanocomposites by covalently bonding Pd onto RGO surfaces to enhance neurite sprouting of cultured neurons. As described, the Pd-RGO nanocomposites exhibit the required physicochemical features for better biocompatibility without impacting cell viability. Primary neurons cultured on Pd-RGO nanocomposites had significantly increased number and length of neuronal processes, including both axons and dendrites, compared with the control. Western blotting showed that Pd-RGO nanocomposites improved the expression levels of growth associate protein-43 (GAP-43), as well as β-III tubulin, Tau-1, microtubule-associated protein-2 (MAP2), four proteins that are involved in regulating neurite sprouting and outgrowth. Importantly, Pd-RGO significantly promoted neurite length and complexity under oxygen-glucose deprivation/re-oxygenation (OGD/R) conditions, an in vitro cellular model of ischemic brain damage, that closely relates to neuronal GAP-43 expression. Furthermore, using the middle cerebral artery occlusion (MCAO) model in rats, we found Pd-RGO effectively reduced the infarct area, decreased neuronal apoptosis in the brain, and improved the rats' behavioral outcomes after MCAO. Together, these results indicate the great potential of Pd-RGO nanocomposites as a novel excellent biomimetic material for neural interfacing that shed light on its applications in brain injuries.

Surface engineered nanodiamonds: mechanistic intervention in biomedical applications for diagnosis and treatment of cancer

In terms of biomedical tools, nanodiamonds (ND) are a more recent innovation. Their size typically ranges between 4 to 100 nm. ND are produced via a variety of methods and are known for their physical toughness, durability, and chemical stability. Studies have revealed that surface modifications and functionalization have a significant influence on the optical and electrical properties of the nanomaterial. Consequently, surface functional groups of NDs have applications in a variety of domains, including drug administration, gene delivery, immunotherapy for cancer treatment, and bio-imaging to diagnose cancer. Additionally, their biocompatibility is a critical requisite for theirin vivoandin vitrointerventions. This review delves into these aspects and focuses on the recent advances in surface modification strategies of NDs for various biomedical applications surrounding cancer diagnosis and treatment. Furthermore, the prognosis of its clinical translation has also been discussed.

Applications of Bioengineered Polymer in the Field of Nano-Based Drug Delivery

The most favored route of drug administration is oral administration; however, several factors, including poor solubility, low bioavailability, and degradation, in the severe gastrointestinal environment frequently compromise the effectiveness of drugs taken orally. Bioengineered polymers have been developed to overcome these difficulties and enhance the delivery of therapeutic agents. Polymeric nanoparticles, including carbon dots, fullerenes, and quantum dots, have emerged as crucial components in this context. They provide a novel way to deliver various therapeutic materials, including proteins, vaccine antigens, and medications, precisely to the locations where they are supposed to have an effect. The promise of this integrated strategy, which combines nanoparticles with bioengineered polymers, is to address the drawbacks of conventional oral medication delivery such as poor solubility, low bioavailability, and early degradation. In recent years, we have seen substantially increased interest in bioengineered polymers because of their distinctive qualities, such as biocompatibility, biodegradability, and flexible physicochemical characteristics. The different bioengineered polymers, such as chitosan, alginate, and poly(lactic-co-glycolic acid), can shield medications or antigens from degradation in unfavorable conditions and aid in the administration of drugs orally through mucosal delivery with lower cytotoxicity, thus used in targeted drug delivery. Future research in this area should focus on optimizing the physicochemical properties of these polymers to improve their performance as drug delivery carriers.

Zero-Dimensional Carbon Nanomaterials for Fluorescent Sensing and Imaging

Advances in nanotechnology and nanomaterials have attracted considerable interest and play key roles in scientific innovations in diverse fields. In particular, increased attention has been focused on carbon-based nanomaterials exhibiting diverse extended structures and unique properties. Among these materials, zero-dimensional structures, including fullerenes, carbon nano-onions, carbon nanodiamonds, and carbon dots, possess excellent bioaffinities and superior fluorescence properties that make these structures suitable for application to environmental and biological sensing, imaging, and therapeutics. This review provides a systematic overview of the classification and structural properties, design principles and preparation methods, and optical properties and sensing applications of zero-dimensional carbon nanomaterials. Recent interesting breakthroughs in the sensitive and selective sensing and imaging of heavy metal pollutants, hazardous substances, and bioactive molecules as well as applications in information encryption, super-resolution and photoacoustic imaging, and phototherapy and nanomedicine delivery are the main focus of this review. Finally, future challenges and prospects of these materials are highlighted and envisaged. This review presents a comprehensive basis and directions for designing, developing, and applying fascinating fluorescent sensors fabricated based on zero-dimensional carbon nanomaterials for specific requirements in numerous research fields.

Covalent conjugates based on nanodiamonds with doxorubicin and a cytostatic drug from the group of 1,3,5-triazines: Synthesis, biocompatibility and biological activity

We report the synthesis of covalent conjugates of nanodiamonds with doxorubicin and a cytostatic drug from the class of 1,3,5-triazines. The obtained conjugates were identified using a number of physicochemical methods (IR-spectroscopy, NMR-spectroscopy, XRD, XPS, TEM). As a result of our study, it was found that ND-СONH-Dox and ND-COO-Diox showed good hemocompatibility, since they did not affect plasma coagulation hemostasis, platelet functional activity, and erythrocyte membrane. The ND-COO-Diox conjugates are also capable of binding to human serum albumin due to the presence of ND in their composition. In the study of the cytotoxic properties of ND-СONH-Dox and ND-COO-Diox in the T98G glioblastoma cell line, indicating that ND-СONH-Dox and ND-COO-Diox demonstrate greater cytotoxicity at lower concentrations of Dox and Diox in the composition of the conjugates compared to individual drugs; the cytotoxic effect of ND-COO-Diox was statistically significantly higher than that of ND-СONH-Dox at all concentrations studied. Greater cytotoxicity at lower concentrations of Dox and Diox in the composition of conjugates compared to individual cytostatics makes it promising to further study the specific antitumor activity and acute toxicity of these conjugates in models of glioblastoma in vivo. Our results demonstrated that ND-СONH-Dox and ND-COO-Diox enter HeLa cells predominantly via a nonspecific actin-dependent mechanism, while for ND-СONH-Dox a clathrin-dependent endocytosis pathway. All data obtained provide that the synthesized nanomaterials show a potential application as the agents for intertumoral administration.

Evaluation of Cytotoxicity and Bioimaging of Nitrogen-Vacancy Nanodiamonds

Nanodiamonds, due to their chemical inertness and biocompatibility, have found extensive uses in drug delivery and biomedical applications. Fluorescent nanodiamonds with fluorescent properties generated by nitrogen-vacancy defects have been intensively investigated for bioimaging, due to their high quantum yield and high photobleaching stability. In addition, the surface properties and particle size of nanodiamonds have significant impacts on cellular uptake and imaging quality. In this study, nitrogen-vacancy nanodiamonds with different particle sizes (40 nm and 90 nm) have been physicochemically characterised and investigated for their cytotoxicity and potential in fluorescence imaging. The nanodiamonds (with concentrations up to 100 µg/mL) showed cell viability >70% with mesenchymal stromal cells. The number of nanodiamonds was observed to have a larger impact on cell viability than the mass of nanodiamonds. Larger nanodiamonds (90 nm) exhibited a lower level of cytotoxicity, higher cellular uptake and fluorescence intensity. The results indicate the potential of using fluorescent nanodiamonds as a nanoprobe for effective bioimaging and cell tracking.

Divergent Effects of Laser Irradiation on Ensembles of Nitrogen-Vacancy Centers in Bulk and Nanodiamonds: Implications for Biosensing

Ensembles of negatively charged nitrogen-vacancy centers (NV^-) in diamond have been proposed for sensing of magnetic fields and paramagnetic agents, and as a source of spin-order for the hyperpolarization of nuclei in magnetic resonance applications. To this end, strongly fluorescent nanodiamonds (NDs) represent promising materials, with large surface areas and dense ensembles of NV^-. However, surface effects tend to favor the less useful neutral form, the NV⁰ centers, and strategies to increase the density of shallow NV^- centers have been proposed, including irradiation with strong laser power (Gorrini in ACS Appl Mater Interfaces. 13:43221-43232, 2021). Here, we study the fluorescence properties and optically detected magnetic resonance (ODMR) of NV^- centers as a function of laser power in strongly fluorescent bulk diamond and in nanodiamonds obtained by nanomilling of the native material. In bulk diamond, we find that increasing laser power increases ODMR contrast, consistent with a power-dependent increase in spin-polarization. Conversely, in nanodiamonds we observe a non-monotonic behavior, with a decrease in ODMR contrast at higher laser power. We hypothesize that this phenomenon may be ascribed to more efficient NV^-→NV⁰ photoconversion in nanodiamonds compared to bulk diamond, resulting in depletion of the NV^- pool. A similar behavior is shown for NDs internalized in macrophage cells under the typical experimental conditions of imaging bioassays. Our results suggest strong laser irradiation is not an effective strategy in NDs, where the interplay between surface effects and local microenvironment determine the optimal experimental conditions.

Application of non-metal nanoparticles, as a novel approach, for improving the stability of blood products: 2011-2021

Despite the importance of the proper quality of blood products for safe transfusion, conventional methods for preparation and their preservation, they lack significant stability. Non-metal nanoparticles with particular features may overcome these challenges. This review study for the first time provided a comprehensive vision of the interaction of non-metal nanoparticles with each blood product (red blood cells, platelets and plasma proteins). The findings of this review on the most effective nanoparticle for improving the stability of RBCs indicate that graphene quantum dots and nanodiamonds show compatibility with RBCs. For increasing the stability of platelet products, silica nanoparticles exhibited a suppressive impact on platelet aggregation. Pristine graphene also shows compatibility with platelets. For better stability of plasma products, graphene oxide was indicated to preserve free human serum albumin from thermal shocks at low ionic strength. For increased stability of Factor VIII, mesoporous silica nanoparticles with large pores exhibit the superb quality of recovered proteins. Furthermore, 3.2 nm quantum dots exhibited anticoagulant effects. As the best promising nanoparticles for immunoglobulin stability, graphene quantum dots showed compatibility with γ-globulins. Overall, this review recommends further research on the mentioned nanoparticles as the most potential candidates for enhancing the stability and storage of blood components.

Single-Atom Fe-Anchored Nano-Diamond With Enhanced Dual-Enzyme Mimicking Performance for H2O2 and Glutathione Detection

Glutathione (GSH) is an important antioxidant and free radical scavenger that converts harmful toxins into harmless substances and excretes them out of the body. In the present study, we successfully prepared single-atom iron oxide-nanoparticle (Fe-NP)-modified nanodiamonds (NDs) named Fe-NDs via a one-pot in situ reduction method. This nanozyme functionally mimics two major enzymes, namely, peroxidase and oxidase. Accordingly, a colorimetric sensing platform was designed to detect hydrogen peroxide (H₂O₂) and GSH. Owing to their peroxidase-like activity, Fe-NDs can oxidize colorless 3,3',5,5'-tetramethylbenzidine (TMB) into blue with sufficient linearity at H₂O₂ concentrations of 1-60 μM and with a detection limit of 0.3 μM. Furthermore, using different concentrations of GSH, oxidized TMB can be reduced to TMB, and the color change from blue to nearly colorless can be observed by the naked eye (linear range, 1-25 μM; detection limit, 0.072 μM). The established colorimetric method based on oxidase-like activity can be successfully used to detect reduced GSH in tablets and injections with good selectivity and high sensitivity. The results of this study exhibited reliable consistency with the detection results obtained using high-performance liquid chromatography (HPLC). Therefore, the Fe-NDs colorimetric sensor designed in this study offers adequate accuracy and sensitivity.

Trigonelline hydrochloride conjugated onto PEGylated nanodiamonds for a selective encapsulation efficiency and controlled release for the inhibition of collagen fibrillation

Recently, researchers are involved in finding a cure for fibrotic disorders, which are an acute disease.

Self-assembling combretastatin A4 incorporated protamine/nanodiamond hybrids for combined anti-angiogenesis and mild photothermal therapy in liver cancer

Tumor angiogenesis has been identified as an important factor in the development and progression of tumors, and anti-angiogenesis therapy has been recognized as an effective tumor therapy pattern. The unique characteristics of nanodiamonds (NDs) have been explored for photothermal therapy (PTT) against cancer, while the efficiency of mild PTT mediated by bare NDs was limited. The combination of different therapies into a single nanoplatform has shown great potential for synergistic cancer treatment. In this investigation, we integrated hydrophobic antiangiogenesis agent combretastatin A4 (CA4) into the protamine sulfate (PS) functionalized NDs hybrids (NDs@PS) with a noncovalent self-assembling method (CA4-NDs@PS) for potential combined anti-angiogenesis and mild PTT in liver cancer. The resulted CA4-NDs@PS NDs exhibited high drug loading ability, good dispersibility and colloidal stability. The near-infrared (NIR) laser irradiation could trigger the release of CA4 from CA4-NDs@PS NDs and elevate the temperature of CA4-NDs@PS NDs aqueous solution.In vitroresults illustrated that CA4-NDs@PS coupled with laser irradiation could remarkably enhance HepG-2 cells killing efficiency, leading to an enhanced photocytotoxicity. Furthermore,in vivoexperiments revealed that CA4-NDs@PS exhibited a highly synergistic anticancer efficacy with NIR laser irradiation in HepG-2 tumor-bearing mice. Altogether, our present study fabricated a novel NDs@PS-based nanoplatform for combined anti-tumor angiogenesis and mild PTT against liver cancer.

CdO nanoparticles, c-MWCNT nanoparticles and CdO nanoparticles/c-MWCNT nanocomposite fibres: in vitro assessment of anti-proliferative and apoptotic studies in HeLa cancer cell line

A simple ultrasonic assisted chemical technique was used to synthesise cadmium oxide (CdO) nanoparticles (NPs) and CdO NPs/c-Multiwalled carbon nanotube (c-MWCNT) nanocomposite fibres.To confirm the physio-chemico properties and to analyse surface morphology of the obtained nanomaterials X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) were performed. To evaluate the anti-cancer property of CdO NPs, c-MWCNT NPs and CdO NPs/c-MWCNT nanocomposite fibres, an anti-proliferative assay test (Methylthiazolyl diphenyl- tetrazolium bromide - MTT assay) were performed on HeLa cells which further estimated IC50 value (Least concentration of sample in which nearly 50% of cells remain alive) under in-vitro conditions. On comparison, CdONPs/c-MWCNT based system was found to be superior by achieving 52.3% cell viability with its minimal IC50 value of 31.2 μg/ml. Lastly, the CdO NPs based system was taken up for an apoptotic study using DNA fragmentation assay for estimating its ability to cleave the DNA of the HeLa cells into internucleosomal fragments using the agarose gel electrophoresis method. In conclusion, based on our observations, CdO NPs/c-MWCNT hybrid based system can be further used for the development of efficient drug delivery and therapeutic systems.

Fabrication of Gd-DOTA-functionalized carboxylated nanodiamonds for selective MR imaging (MRI) of the lymphatic system

Magnetic resonance imaging (MRI) contrast agents with the particle diameter of around 3-10 nm hold the potential to be selectively uptaken by lymphatic vessels and be filtered in the kidney for final excretion. However, there are no existing MRI contrast agents based on gadolinium (Gd) complexes within the size of this range, and thus the selective imaging of the lymphatic system has not yet been achieved. In our previous report, we succeeded in fabricating nano-scale MRI contrast agents by complexing ordinary contrast agents (Gd-diethylenetriaminepentaacetic acid (DTPA)) with carboxylated nanodiamond (CND) particles to conquer this problem. However, DTPA has recently been reported to release Gd ions in the course of time, leading to the potential danger of severe side effects in the human body. In this study, we utilized cyclic-chained DOTA as an alternative chelating material for DTPA to fabricate CND-based MRI contrast agents for the selective lymphatic imaging. The newly fabricated contrast agents possessed the diameter ranging from 3 to 10 nm in distilled water and serum, indicating that these particles can be selectively uptaken by lymphatic vessels and effectively filtered in the kidney. Furthermore, the DOTA-applied CND contrast agents exhibited stronger MRI visibility in water and serum compared to DTPA-applied CND contrast agents. These results indicate that DOTA-applied CND contrast agents are promising materials for the selective MR imaging of lymphatic systems.

Comparison of diamond nanoparticles captured on the floating and grounded membranes in the hot filament chemical vapor deposition process

Negatively charged diamond nanoparticles are known to be generated in the gas phase of the hot filament chemical vapor deposition (HFCVD) process. However, the structures of these nanoparticles remain unknown. Also, the effect of charging on the stability of nanodiamond structures has not been studied experimentally. Here, by installing a capturing apparatus in an HFCVD reactor, we succeeded in capturing nanoparticles on the floating and grounded SiO, carbon, and graphene membranes of a copper transmission electron microscope grid during HFCVD. We examined the effect of charge on the crystal structure of nanodiamonds captured for 10 s under various conditions and identified four carbon allotropes, which are i-carbon, hexagonal diamond, n-diamond, and cubic diamond, by analyzing 150 d-spacings of ∼100 nanoparticles for each membrane. Nanoparticles captured on the floating membrane consisted mainly of cubic diamond and n-diamond, whereas those captured on the grounded membrane consisted mainly of i-carbon. Diamond particles deposited for 8 h on the floating silicon (Si) substrate exhibited an octahedron shape with well-developed facets, and a high-intensity 1332 cm-1 Raman peak, whereas diamond particles deposited on the grounded Si substrate showed a spherical shape partially covered with crystalline facets with a broad G-band Raman peak. These results indicate that charging stabilizes the diamond structure.

Porphyrin–Nanodiamond Hybrid Materials—Active, Stable and Reusable Cyclohexene Oxidation Catalysts

The quest for active, yet “green” non-toxic catalysts is a continuous challenge. In this work, covalently linked hybrid porphyrin–nanodiamonds were prepared via ipso nitro substitution reaction and characterized by X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, infrared spectroscopy (IR) and thermogravimetry-differential scanning calorimetry (TG-DSC). The amine-functionalized nanodiamonds (ND@NH2) and 2-nitro-5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin covalently linked to nanodiamonds (ND@βNH-TPPpCF3) were tested using Allium cepa as a plant model, and showed neither phytotoxicity nor cytotoxicity. The hybrid nanodiamond–copper(II)–porphyrin material ND@βNH-TPPpCF3-Cu(II) was also evaluated as a reusable catalyst in cyclohexene allylic oxidation, and displayed a remarkable turnover number (TON) value of ≈265,000, using O2 as green oxidant, in the total absence of sacrificial additives, which is the highest activity ever reported for said allylic oxidation. Additionally, ND@βNH-TPPpCF3-Cu(II) could be easily separated from the reaction mixture by centrifugation, and reused in three consecutive catalytic cycles without major loss of activity.

Streptococcus mutans Growth and Resultant Material Surface Roughness on Modified Glass Ionomers

The present study investigate the optical density of Streptococcus mutans (S. mutans) at 450 nm (OD450 nm) as well as the change in surface roughness of three commercially available chitosan- and nanodiamond-modified glass ionomers. The results indicated that the optical density of S. mutans OD450 nm decreased significantly (p < 0.0001) from 0 h through 2–4 h for each of the control materials. The lowest S. mutans OD450 nm was noted for Fuji IX followed by Ketac Universal. Riva Self Cure had the largest increase in the S. mutans OD450 nm. The control materials and their chitosan/nanodiamond modifications showed significant growth at 6 h compare to the preceding time periods of 2 and 4 h. The materials Fuji IX, Fuji IX modified with 5% Nanodiamonds, Fuji IX modified with 10% Chitosan and Ketac Universal modified with 10% Chitosan performed the best with regard to the bacterial reduction. Only the chitosan modifications showed an increase in the surface roughness after 24 h of exposure to the S. mutans. The chitosan and the nanodiamond modifications provided the best disruption of the S. mutans biofilm formation.

Pullulan based stimuli responsive and sub cellular targeted nanoplatforms for biomedical application: Synthesis, nanoformulations and toxicological perspective

With growing interest in polymers of natural origin, innumerable polysaccharides have gained attention for their biomedical application. Pullulan, one of the FDA approved nutraceuticals, possesses multiple unique properties which make them highly advantageous for biomedical applications. This present review encompasses the sources, production, properties and applications of pullulan. It highlights various pullulan based stimuli-responsive systems (temperature, pH, ultrasound, magnetic), subcellular targeted systems (mitochondria, Golgi apparatus/endoplasmic reticulum, lysosome, endosome), lipid-vesicular systems (solid-lipid nanoparticles, liposomes), polymeric nanofibres, micelles, inorganic (SPIONs, gold and silver nanoparticles), carbon-based nanoplatforms (carbon nanotubes, fullerenes, nanodiamonds) and quantum dots. This article also gives insight into different biomedical, therapeutic and diagnostic applications of pullulan viz., imaging, tumor targeting, stem cell therapy, gene therapy, vaccine delivery, cosmetic applications, protein delivery, tissue engineering, photodynamic therapy and chaperone-like activities. The review also includes the toxicological profile of pullulan which is helpful for the development of suitable delivery systems for clinical applications.

The Puzzling Potential of Carbon Nanomaterials: General Properties, Application, and Toxicity

Being a member of the nanofamily, carbon nanomaterials exhibit specific properties that mostly arise from their small size. They have proved to be very promising for application in the technical and biomedical field. A wide spectrum of use implies the inevitable presence of carbon nanomaterials in the environment, thus potentially endangering their whole nature. Although scientists worldwide have conducted research investigating the impact of these materials, it is evident that there are still significant gaps concerning the knowledge of their mechanisms, as well as the prolonged and chronic exposure and effects. This manuscript summarizes the most prominent representatives of carbon nanomaterial groups, giving a brief review of their general physico-chemical properties, the most common use, and toxicity profiles. Toxicity was presented through genotoxicity and the activation of the cell signaling pathways, both including in vitro and in vivo models, mechanisms, and the consequential outcomes. Moreover, the acute toxicity of fullerenol, as one of the most commonly investigated members, was briefly presented in the final part of this review. Thinking small can greatly help us improve our lives, but also obliges us to deeply and comprehensively investigate all the possible consequences that could arise from our pure-hearted scientific ambitions and work.

Zwitterion-Functionalized Detonation Nanodiamond with Superior Protein Repulsion and Colloidal Stability in Physiological Media

Nanodiamond (ND) is a versatile and promising material for bioapplications. Despite many efforts, agglomeration of nanodiamond and the nonspecific adsorption of proteins on the ND surface when exposed to biofluids remains a major obstacle for biomedical applications. Here, the functionalization of detonation nanodiamond with zwitterionic moieties in combination with tetraethylene glycol (TEG) moieties immobilized by click chemistry to improve the colloidal dispersion in physiological media with strong ion background and for the simultaneous prevention of nonspecific interactions with proteins is reported. Based on five building blocks, a series of ND conjugates is synthesized and their performance is compared in biofluids, such as fetal bovine serum (FBS) and Dulbecco's modified Eagle medium (DMEM). The adsorption of proteins is investigated via dynamic light scattering (DLS) and thermogravimetric analysis. The colloidal stability is tested with DLS monitoring over prolonged periods of time in various ratios of water/FBS/DMEM and at different pH values. The results show that zwitterions efficiently promote the anti-fouling properties, whereas the TEG linker is essential for the enhanced colloidal stability of the particles.

Biocompatibility in regenerative nanomedicine

Biocompatibility is a very common word that is used within biomaterial science and used for description of the interactions between the foreign material and the body. However, the meaning of biocompatibility as well as the mechanisms that collectively constitutes is still unclear. With the advance of nanotechnology, new concerns have been observed related to biocompatibility of these biomaterials. Due to their small size and variability of their physical and chemical properties, nanoparticles' (NP) distribution within the body and interactions with the target cells and tissues are highly variable. Here, we tried to provide an overview about NPs, the concept of biocompatibility and biocompatibility-related issues in nanomedicine and several different NPs.

Applications of Nanodiamonds in the Detection and Therapy of Infectious Diseases

We are constantly exposed to infectious diseases, and they cause millions of deaths per year. The World Health Organization (WHO) estimates that antibiotic resistance could cause 10 million deaths per year by 2050. Multidrug-resistant bacteria are the cause of infection in at least one in three people suffering from septicemia. While antibiotics are powerful agents against infectious diseases, the alarming increase in antibiotic resistance is of great concern. Alternatives are desperately needed, and nanotechnology provides a great opportunity to develop novel approaches for the treatment of infectious diseases. One of the most important factors in the prognosis of an infection caused by an antibiotic resistant bacteria is an early and rigorous diagnosis, jointly with the use of novel therapeutic systems that can specifically target the pathogen and limit the selection of resistant strains. Nanodiamonds can be used as antimicrobial agents due to some of their properties including size, shape, and biocompatibility, which make them highly suitable for the development of efficient and tailored nanotherapies, including vaccines or drug delivery systems. In this review, we discuss the beneficial findings made in the nanodiamonds field, focusing on diagnosis and treatment of infectious diseases. We also highlight the innovative platform that nanodiamonds confer for vaccine improvement, drug delivery, and shuttle systems, as well as their role in the generation of faster and more sensitive clinical diagnosis.

Diamond Nanoparticles Downregulate Expression of CycD and CycE in Glioma Cells

Our previous studies have shown that diamond nanoparticles (NDs) exhibited antiangiogenic and proapoptotic properties in vitro in glioblastoma multiforme (GBM) cells and in tumors in vivo. Moreover, NDs inhibited adhesion, leading to the suppression of migration and invasion of GBM. In the present study, we hypothesized that the NDs might also inhibit proliferation and cell cycle in glioma cells. Experiments were performed in vitro with the U87 and U118 lines of GBM cells, and for comparison, the Hs5 line of stromal cells (normal cells) after 24 h and 72 h of treatment. The analyses included cell morphology, cell death, viability, and cell cycle analysis, double timing assay, and gene expression (Rb, E2F1, CycA, CycB, CycD, CycE, PTEN, Ki-67). After 72 h of ND treatment, the expression level of Rb, CycD, and CycE in the U118 cells, and E2F1, CycD, and CycE in the U87 cells were significantly lower in comparison to those in the control group. We observed that decreased expression of cyclins inhibited the G1/S phase transition, arresting the cell cycle in the G0/G1 phase in glioma cells. The NDs did not affect the cell cycle as well as PTEN and Ki-67 expression in normal cells (Hs5), although it can be assumed that the NDs reduced proliferation and altered the cell cycle in fast dividing cells.

Carbon Nanomaterials for Energy and Biorelated Catalysis: Recent Advances and Looking Forward

Along with the wide investigation activities in developing carbon-based, metal-free catalysts to replace precious metal (e.g., Pt) catalysts for various green energy devices, carbon nanomaterials have also shown great potential for biorelated applications. This article provides a focused, critical review on the recent advances in these emerging research areas. The structure-property relationship and mechanistic understanding of recently developed carbon-based, metal-free catalysts for chemical/biocatalytic reactions will be discussed along with the challenges and perspectives in this exciting field, providing a look forward for the rational design and fabrication of new carbon-based, metal-free catalysts with high activities, remarkable selectivity, and outstanding durability for various energy-related/biocatalytic processes.

Fluorescent Fe Embedded Magnetic Nanodiamonds Made by Ion Implantation

We demonstrate fluorescent Fe embedded magnetic nanodiamonds by ion implantation and two-step annealing. The diamond characteristics with a highly ordered core and a graphite surface layer are maintained after the implantation process. After the two-step annealing process, a bright red fluorescence associated with nitrogen-vacancy centers is observed. These new fluorescent magnetic nanodiamonds can be used as a dual-function in vivo tracer with both optical visibility and magnetic resonance imaging capabilities. They are potentially useful for the more advanced in vivo biological and medical applications.

Doping of Carbon Materials for Metal-Free Electrocatalysis

Carbon atoms in the graphitic carbon skeleton can be replaced by heteroatoms with different electronegative from that of the carbon atom (i.e., heteroatom doping) to modulate the charge distribution over the carbon network. The charge modulation can be achieved via direct charge transfer with an electron acceptor/donor (i.e., charge transfer doping) or through introduction of defects (i.e., defective doping). Various doping strategies, including heteroatom doping, charge-transfer doping, and defective doping, have now been devised for modulating the charge distribution of numerous graphite carbon materials to impart new properties to carbon materials. Consequently, carbon nanomaterials with defined doping have recently become prominent members in the carbon family, promising for a variety of applications, including catalysis, energy conversion and storage, environmental remediation, and important chemical production and industrial processes. The purpose of this review is to present an overview on the doping of carbon materials for metal-free electrocatalysis, especially the development of doping strategies and doping-induced structure and property changes for potential catalytic applications. Current challenges and future perspectives in the doped carbon-based metal-free catalyst field are also discussed.

Recent Advances in Carbon Nanomaterials for Cancer Phototherapy

Carbon nanomaterials have received great attention from the scientific community over the past few decades because of their unique physical and chemical properties. In this minireview, we will summarize the recent progress of the use of various carbon nanomaterials in the field of cancer phototherapy. The structural characteristics of each category and the surface functionalization strategies of these nanomaterials will be briefly introduced before focusing on their therapeutic applications. Recent advances on their use in photothermal therapy, photodynamic therapy, and combined phototherapies are presented. Moreover, a few challenges and perspectives on the development of carbon nanomaterials for future theranostics are also discussed.

Predicting the impact of structural diversity on the performance of nanodiamond drug carriers

Diamond nanoparticles (nanodiamonds) are unique among carbon nanomaterials, and are quickly establishing a niché in the biomedical application domain. Nanodiamonds are non-toxic, amenable to economically viable mass production, and can be interfaced with a variety of functional moieties. However, developmental challenges arise due to the chemical complexity and structural diversity inherent in nanodiamond samples. Nanodiamonds present a narrow, but significant, distribution of sizes, a dizzying array of possible shapes, and a complicated surface containing aliphatic and aromatic carbon. In the past these facts have been cast as hindrances, stalling development until perfectly monodispersed samples could be achieved. Current research has moved in a different direction, exploring ways that the polydispersivity of nanodiamond samples can be used as a new degree of engineering freedom, and understanding the impact our limited synthetic control really has upon structure/property relationships. In this review a series of computational and statistical studies will be summarised and reviewed, to characterise the relationship between chemical complexity, structural diversity and the reactive performance of nanodiamond drug carriers.

Recent review of the effect of nanomaterials on stem cells

The field of stem-cell-therapy offers considerable promise as a means of delivering new treatments for a wide range of diseases. Recent progress in nanotechnology has stimulated the development of multifunctional nanomaterials (NMs) for stem-cell-therapy. Several clinical trials based on the use of NMs are currently underway for stem-cell-therapy purposes, such as drug/gene delivery and imaging. However, the interactions between NMs and stem cells are far from being completed, and the effects of the NMs on cellular behavior need critical evaluation. In this review, the interactions between several types of mostly used NMs and stem cells, and their associated possible mechanisms are systematically discussed, with specific emphasis on the possible differentiation effects induced by NMs. It is expected that the enhanced understanding of NM-stem cell interactions will facilitate biomaterial design for stem-cell-therapy and regenerative medicine applications.

Carbon-Based Metal-Free Electrocatalysis for Energy Conversion, Energy Storage, and Environmental Protection

Abstract

Carbon-based metal-free catalysts possess desirable properties such as high earth abundance, low cost, high electrical conductivity, structural tunability, good selectivity, strong stability in acidic/alkaline conditions, and environmental friendliness. Because of these properties, these catalysts have recently received increasing attention in energy and environmental applications. Subsequently, various carbon-based electrocatalysts have been developed to replace noble metal catalysts for low-cost renewable generation and storage of clean energy and environmental protection through metal-free electrocatalysis. This article provides an up-to-date review of this rapidly developing field by critically assessing recent advances in the mechanistic understanding, structure design, and material/device fabrication of metal-free carbon-based electrocatalysts for clean energy conversion/storage and environmental protection, along with discussions on current challenges and perspectives.

Graphical Abstract

Nanodiamonds for device applications: An investigation of the properties of boron-doped detonation nanodiamonds

The inclusion of boron within nanodiamonds to create semiconducting properties would create a new class of applications in the field of nanodiamond electronics. Theoretical studies have differed in their conclusions as to whether nm-scale NDs would support a stable substitutional boron state, or whether such a state would be unstable, with boron instead aggregating or attaching to edge structures. In the present study detonation-derived NDs with purposefully added boron during the detonation process have been studied with a wide range of experimental techniques. The DNDs are of ~4 nm in size, and have been studied with CL, PL, Raman and IR spectroscopies, AFM and HR-TEM and electrically measured with impedance spectroscopy; it is apparent that the B-DNDs studied here do indeed support substitutional boron species and hence will be acting as semiconducting diamond nanoparticles. Evidence for moderate doping levels in some particles (~10¹⁷ B cm⁻³), is found alongside the observation that some particles are heavily doped (~10²⁰ B cm⁻³) and likely to be quasi-metallic in character. The current study has therefore shown that substitutional boron doping in nm NDs is in fact possible, opening-up the path to a whole host of new applications for this interesting class of nano-particles.

Nanodiamond-enhanced MRI via in situ hyperpolarization

Nanodiamonds are of interest as nontoxic substrates for targeted drug delivery and as highly biostable fluorescent markers for cellular tracking. Beyond optical techniques, however, options for noninvasive imaging of nanodiamonds in vivo are severely limited. Here, we demonstrate that the Overhauser effect, a proton–electron polarization transfer technique, can enable high-contrast magnetic resonance imaging (MRI) of nanodiamonds in water at room temperature and ultra-low magnetic field. The technique transfers spin polarization from paramagnetic impurities at nanodiamond surfaces to ¹H spins in the surrounding water solution, creating MRI contrast on-demand. We examine the conditions required for maximum enhancement as well as the ultimate sensitivity of the technique. The ability to perform continuous in situ hyperpolarization via the Overhauser mechanism, in combination with the excellent in vivo stability of nanodiamond, raises the possibility of performing noninvasive in vivo tracking of nanodiamond over indefinitely long periods of time.

Hyperpolarized magnetic resonance imaging can enhance imaging contrast by orders of magnitude, but applications are limited by the thermal relaxation of hyperpolarized states. Here, Waddington et al. demonstrate the on-demand hyperpolarization of hydrogen spins through the Overhauser effect with nanodiamonds.

Estimation of microscope drift using fluorescent nanodiamonds as fiducial markers

Fiducial markers are used to correct the microscope drift and should be photostable, be usable at multiple wavelengths and be compatible for multimodal imaging. Fiducial markers such as beads, gold nanoparticles, microfabricated patterns and organic fluorophores lack one or more of these criteria. Moreover, the localization accuracy and drift correction can be degraded by other fluorophores, instrument noise and artefacts due to image processing and tracking algorithms. Estimating mechanical drift by assuming Gaussian distributed noise is not suitable under these circumstances. Here we present a method that uses fluorescent nanodiamonds as fiducial markers and uses an improved maximum likelihood algorithm to estimate the drift with both accuracy and precision within the range 1.55-5.75 nm.

Recent advances in carbon based nanosystems for cancer theranostics

This review deals with four different types of carbon allotrope based nanosystems and summarizes the results of recent studies that are likely to have applications in cancer theranostics. We discuss the applications of these nanosystems for cancer imaging, drug delivery, hyperthermia, and PDT/TA/PA.

PEG Grafted-Nanodiamonds for the Delivery of Gemcitabine

Carboxyl end-functionalized poly[poly(ethylene glycol) methyl ether methacrylate] [P(PEGMEMA)] and its block copolymer with gemcitabine substituted poly(N-hydroxysuccinimide methacrylate) [PGem-block-P(PEGMEMA)] are synthesized via reversible addition-fragmentation transfer (RAFT) polymerization. Then, two polymers are grafted onto the surface of amine-functionalized nanodiamonds to obtain [P(PEGMEMA)]-grafted nanodiamonds (ND-PEG) and [PGem-block-P(PEGMEMA)]-grafted nanodiamonds (ND-PF). Gemcitabine is physically absorbed to ND-PEG to produce ND-PEG (Gem). Two polymer-grafted nanodiamonds (i.e., with physically absorbed gemcitabine ND-PEG (Gem) and with chemically conjugated gemcitabine ND-PF) are characterized using attenuated total reflectance infrared spectroscopy, dynamic light scattering, and thermogravimetric analysis. The drug release, cytotoxicity (to seed human pancreatic carcinoma AsPC-1 cells), and cellular uptake of ND-PEG (Gem) and ND-PF are also investigated.

Carbon-Based Materials for Photo-Triggered Theranostic Applications

Carbon-based nanomaterials serve as a type of smart material for photo-triggered disease theranostics. The inherent physicochemical properties of these nanomaterials facilitate their use for less invasive treatments. This review summarizes the properties and applications of materials including fullerene, nanotubes, nanohorns, nanodots and nanographenes for photodynamic nanomedicine in cancer and antimicrobial therapies. Carbon nanomaterials themselves do not usually act as photodynamic therapy (PDT) agents owing to the high hydrophobicity, however, when the surface is passivated or functionalized, these materials become great vehicles for PDT. Moreover, conjugation of carbonaceous nanomaterials with the photosensitizer (PS) and relevant targeting ligands enhances properties such as selectivity, stability, and high quantum yield, making them readily available for versatile biomedical applications.