Nanodiamond-Based Composite Structures for Biomedical Imaging and Drug Delivery

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.

Pickering emulsions stabilized by carboxylated nanodiamonds over a broad pH range

HYPOTHESIS

Surfactants in emulsions sometimes do not provide adequate stability against coalescence, whereas Pickering emulsions often offer greater stability. In a search for stabilizers offering biocompatibility, we hypothesized that carboxylated nanodiamonds (ND) would impart stability to Pickering emulsions.

EXPERIMENTS

We successfully prepared Pickering emulsions of sunflower oil in water via two different methods: membrane emulsification and probe sonication. The first method was only possible when the pH of the aqueous ND suspension was ≤ 4.

FINDINGS

Pendant-drop tensiometry confirmed that carboxylated ND is adsorbed at the oil/water interface, with a greater decrease in interfacial tension found with increasing ND concentrations in the aqueous phase. The carboxylated ND become more hydrophilic with increasing pH, according to three-phase contact angle analysis, because of deprotonation of the carboxylic acid groups. Membrane emulsification yielded larger (about 30 µm) oil droplets, probe sonication produced smaller (sub-μm) oil droplets. The Pickering emulsions show high stability against mechanical vibration and long-term storage for one year. They remain stable against coalescence across a wide range of pH values. Sonicated emulsions show stability against creaming. In this first-ever systematic study of carboxylated ND-stabilized Pickering emulsions, we demonstrate a promising application in the delivery of β-carotene, as a model active ingredient.

Carbon Quantum Dots: In vitro and in vivo Studies on Biocompatibility and Biointeractions for Optical Imaging

BACKGROUND

Understanding the biocompatibility and biointeractions of nano-carbon quantum dots (nano-CQDs) in vitro and in vivo is important for assessing their potential risk to human health. In the previous research, the physical properties of CQDs synthesized by the laser ablation in liquid (LAL) method were analyzed in detail; however, possible bioapplications were not considered.

MATERIALS AND METHODS

CQDs were prepared by LAL and characterized by atomic force microscopy, fluorescence lifetime, absorption spectrum, Fourier-transform infrared spectroscopy, and dynamic light scattering. Their biocompatibility was evaluated in vitro using assays for cytotoxicity, apoptosis, and biodistribution and in vivo using immunotoxicity and the relative expression of genes. Cells were measured in vitro using fluorescence-lifetime imaging microscopy to analyze the biointeractions between CQDs and intracellular proteins.

RESULTS

There were no significant differences in biocompatibility between the CQDs and the negative control. The intracellular interactions had no impact on the optical imaging of CQDs upon intake by cells. Optical imaging of zebrafish showed the green fluorescence was well dispersed.

CONCLUSION

We have demonstrated that the CQDs have an excellent biocompatibility and can be used as efficient optical nanoprobes for cell tracking and biomedical labeling except for L929 and PC-3M cells.

Boron-Doped Nanodiamonds as Anticancer Agents: En Route to Hyperthermia/Thermoablation Therapy

Local targeted "inside-out" hyperthermia of tumors via nanoparticles is able to sensitize tumor cells to chemotherapy, radiation therapy, gene therapy, immunotherapy, or other effects, significantly reducing the duration and intensity of treatment. In this article, new nanomaterials are proposed to be used as anticancer agents: boron-doped nanodiamonds with sizes of about 10 nm synthesized for the first time by the high-temperature high-pressure (HTHP) method. The heating ability of boron-doped nanodiamonds was investigated under different heating conditions in different environments: water, chicken egg white, and MCF-7 breast cancer cells. It was discovered that, with the same conversion of the absorbed energy into heat, the ability to heat the environment when excited at a wavelength of 808 nm of boron-doped nanodiamonds is much higher than that of detonation nanodiamonds. It was established that boron-doped nanodiamonds are extremely promising for carrying out hyperthermia and thermoablation of tumors.

Polymer/nanodiamond composites - a comprehensive review from synthesis and fabrication to properties and applications

Nanodiamond (ND) is an allotrope of carbon nanomaterials which exhibits many outstanding physical, mechanical, thermal, optical and biocompatibility characteristics. Meanwhile, ND particles possess unique spherical shape containing diamond-like structure at the core with graphitic carbon outer shell which intuitively contains many oxygen-containing functional groups at the outer surface. Such superior properties and unique structural morphology of NDs are essentially attractive to develop polymer composites with multifunctional properties. However, despite a long history from the discovery of NDs, which is dated back to the1960s, this nanoparticle has been less explored in the field of polymer (nano)composites compared with other carbon nanomaterials, e.g. carbon nanotube (CNT) and graphene. However, open literature indicates that research works in the field of polymer/ND (PND) composites have gained great momentum in the past half a decade. The present article provides a comprehensive review on recent achievements in ND based polymer composites. This review covers a very broad aspect from the synthesis, purification and functionalization of NDs to dispersion, preparation and fabrication of polymer/ND (PND) composites with a look in their recent applications for both structural and functional basis. Therefore, the review would be useful to pave the way for researchers to take some advancing steps in this respect.

Nanodiamonds and surfactants in water: Hydrophilic and hydrophobic interactions

HYPOTHESIS

Nanodiamonds, one of the most promising nanomaterials for the use in biomedicine, placed in the organisms are bound to interact with various amphiphilic lipids and their micelles. However, while the influence of surfactants, the close relative of lipids, on the properties of colloidal nanodiamonds is well studied, the influence of nanodiamonds on the properties of surfactants, lipids, and, therefore, on the structure of surrounding tissues, is poorly understood.

EXPERIMENT

In this work, the influence of interactions of hydrophobic and hydrophilic nanodiamonds with ionic surfactant sodium octanoate in water on hydrogen bonds, the properties of the surfactant and micelle formation were studied using Raman spectroscopy and dynamic light scattering technique.

FINDINGS

Nanodiamonds are found to actively influence the bulk properties only of the premicellar surfactant solutions: the strength of hydrogen bonds, ordering and conformation of hydrocarbon tails, the critical micelle concentration. This influence is deduced to be dependent on two mechanisms not unique to nanodiamonds: (1) the induction of micro-flows around nanoparticles undergoing Brownian motions, and (2) the creation of the chaotic state in the surfactant solutions if two or more incompatible types of interactions between nanoparticles' surfaces and surfactants are similarly favorable, e.g. hydrophobic interaction and Coulomb attraction.

Fluorescence microscopy for visualizing single-molecule protein dynamics

BACKGROUND

Single-molecule fluorescence imaging (smFI) has evolved into a valuable method used in biophysical and biochemical studies as it can observe the real-time behavior of individual protein molecules, enabling understanding of their detailed dynamic features. smFI is also closely related to other state-of-the-art microscopic methods, optics, and nanomaterials in that smFI and these technologies have developed synergistically.

SCOPE OF REVIEW

This paper provides an overview of the recently developed single-molecule fluorescence microscopy methods, focusing on critical techniques employed in higher-precision measurements in vitro and fluorescent nanodiamond, an emerging promising fluorophore that will improve single-molecule fluorescence microscopy.

MAJOR CONCLUSIONS

smFI will continue to improve regarding the photostability of fluorophores and will develop via combination with other techniques based on nanofabrication, single-molecule manipulation, and so on.

GENERAL SIGNIFICANCE

Quantitative, high-resolution single-molecule studies will help establish an understanding of protein dynamics and complex biomolecular systems.

Orthogonal Functionalization of Nanodiamond Particles after Laser Modification and Treatment with Aromatic Amine Derivatives

A laser system with a wavelength of 1064 nm was used to generate sp² carbon on the surfaces of nanodiamond particles (NDPs). The modified by microplasma NDPs were analysed using FT-IR and Raman spectroscopy. Raman spectra confirmed that graphitization had occurred on the surfaces of the NDPs. The extent of graphitization depended on the average power used in the laser treatment process. FT-IR analysis revealed that the presence of C=C bonds in all spectra of the laser-modified powder. The characteristic peaks for olefinic bonds were much more intense than in the case of untreated powder and grew in intensity as the average laser power increased. The olefinized nanodiamond powder was further functionalized using aromatic amines via in situ generated diazonium salts. It was also found that isokinetic mixtures of structurally diverse aromatic amines containing different functional groups (acid, amine) could be used to functionalize the surfaces of the laser-modified nanoparticles leading to an amphiphilic carbon nanomaterial. This enables one-step orthogonal functionalization and opens the possibility of selectively incorporating molecules with diverse biological activities on the surfaces of NDPs. Modified NDPs with amphiphilic properties resulting from the presence carboxyl and amine groups were used to incorporate simultaneously folic acid (FA-CONH-(CH₂)₅-COOH) and 5(6)-carboxyfluorescein (FL-CONH-(CH₂)₂-NH₂) derivatives on the surface of material under biocompatible procedures.

Clinical Applications of Carbon Nanomaterials in Diagnostics and Therapy

Nanomaterials have the potential to improve how patients are clinically treated and diagnosed. While there are a number of nanomaterials that can be used toward improved drug delivery and imaging, how these nanomaterials confer an advantage over other nanomaterials, as well as current clinical approaches is often application or disease specific. How the unique properties of carbon nanomaterials, such as nanodiamonds, carbon nanotubes, carbon nanofibers, graphene, and graphene oxides, make them promising nanomaterials for a wide range of clinical applications are discussed herein, including treating chemoresistant cancer, enhancing magnetic resonance imaging, and improving tissue regeneration and stem cell banking, among others. Additionally, the strategies for further improving drug delivery and imaging by carbon nanomaterials are reviewed, such as inducing endothelial leakiness as well as applying artificial intelligence toward designing optimal nanoparticle-based drug combination delivery. While the clinical application of carbon nanomaterials is still an emerging field of research, there is substantial preclinical evidence of the translational potential of carbon nanomaterials. Early clinically trial studies are highlighted, further supporting the use of carbon nanomaterials in clinical applications for both drug delivery and imaging.

Pilot study on biocompatibility of fluorescent nanodiamond-(NV)-Z~800 particles in rats: safety, pharmacokinetics, and bio-distribution (part III)

Introduction

We hereby report on studies aimed to characterize safety, pharmacokinetics, and bio-distribution of fluorescent nanodiamond particles (NV)-Z~800 (FNDP-(NV)) administered to rats by intravenous infusion in a single high dose.

Methods

Broad scale biological variables were monitored following acute (90 minutes) and subacute (5 or 14 days) exposure to FNDP-(NV). Primary endpoints included morbidity and mortality, while secondary endpoints focused on hematology and clinical biochemistry biomarkers. Particle distribution (liver, spleen, lung, heart, and kidney) was assessed by whole organ near infrared imaging using an in vivo imaging system. This was validated by the quantification of particles extracted from the same organs and visualized by fluorescent and scanning electron microscopy. FNDP-(NV)-treated rats showed no change in morbidity or mortality and preserved normal motor and sensory function, as assessed by six different tests.

Results

Blood cell counts and plasma biochemistry remained normal. The particles were principally distributed in the liver and spleen. The liver particle load accounted for 51%, 24%, and 18% at 90 minutes, 5 days, and 14 days, respectively. A pilot study of particle clearance from blood indicated 50% clearance 33 minutes following the end of particle infusion.

Conclusion

We concluded that systemic exposure of rats to a single high dose of FDNP-(NV)-Z~800 (60 mg/kg) appeared to be safe and well tolerated over at least 2 weeks. These data suggest that FNDP-(NV) should proceed to preclinical development in the near future.

Multimodality Imaging of Silica and Silicon Materials In Vivo

Recent progress in the development of silica- and silicon-based multimodality imaging nanoprobes has advanced their use in image-guided drug delivery, and the development of novel systems for nanotheranostic and diagnostic applications. As biocompatible and flexibly tunable materials, silica and silicon provide excellent platforms with high clinical potential in nanotheranostic and diagnostic probes with well-defined morphology and surface chemistry, yielding multifunctional properties. In vivo imaging is of great value in the exploration of methods for improving site-specific nanotherapeutic delivery by silica- and silicon-based drug-delivery systems. Multimodality approaches are essential for understanding the biological interactions of nanotherapeutics in the physiological environment in vivo. The aim here is to describe recent advances in the development of in vivo imaging tools based on nanostructured silica and silicon, and their applications in single and multimodality imaging.

Hydroxylation and self-assembly of colloidal hydrogenated nanodiamonds by aqueous oxygen radicals from atmospheric pressure plasma jet

Plasma chemical surface modification of nanoparticles in gas–liquid type reactors enables a controllable, specific, low-cost, and environmentally friendly alternative to wet chemistry methods or thermal and dry plasma treatments. Here the atmospheric pressure radio-frequency microplasma jet (µ-APPJ) operating with 0.6% O₂ in He is used to deliver aqueous oxygen radicals (AOR) to the surface of ∼3 nm hydrogenated detonation nanodiamonds (H-DNDs) suspended in water. The AOR-treated H-DND samples are characterized by FTIR and XPS spectroscopies and by AFM and SEM imaging. The main chemical reaction mechanism is identified as the abstraction of surface hydrogen atoms by O or OH radicals and a consequent attachment of the OH group, thereby increasing concentration of alcohols, carboxyls, and aldehydes on the DND's surface. FTIR spectra reveal also a structural re-arrangement of the surface water on the AOR-treated H-DNDs. Yet zeta-potential of AOR-treated H-DNDs still remains positive (decreases from +45 mV to +30 mV). The chemical modification gives rise to formation of nanoscale chain-like aggregates when AOR-treated H-DNDs are deposited on Si substrate.

Colloidal nanodiamonds are hydroxylated by action of plasma-supplied O atoms and undergo self-assembly to chains.

Carboxylated nanodiamonds can be used as negative reference in in vitro nanogenotoxicity studies

Nanodiamonds (NDs) are promising nanomaterials for biomedical applications. However, a few studies highlighted an in vitro genotoxic activity for detonation NDs, which was not evidenced in one of our previous work quantifying γ-H2Ax after 20 and 100 nm high-pressure high-temperature ND exposures of several cell lines. To confirm these results, in the present work, we investigated the genotoxicity of the same 20 and 100 nm NDs and added intermediate-sized NDs of 50 nm. Conventional in vitro genotoxicity tests were used, i.e., the in vitro micronucleus and comet assays that are recommended by the French National Agency for Medicines and Health Products Safety for the toxicological evaluation of nanomedicines. In vitro micronucleus and in vitro comet assays (standard and hOGG1-modified) were therefore performed in two human cell lines, the bronchial epithelial 16HBE14o- cells and the colon carcinoma T84 cells. Our results did not show any genotoxic activity, whatever the test, the cell line or the size of carboxylated NDs. Even though these in vitro results should be confirmed in vivo, they reinforce the potential interest of carboxylated NDs for biomedical applications or even as a negative reference nanoparticle in nanotoxicology. Copyright © 2017 John Wiley & Sons, Ltd.

Fluorescent nanodiamonds engage innate immune effector cells: A potential vehicle for targeted anti-tumor immunotherapy

Fluorescent nanodiamonds (FNDs) are nontoxic, infinitely photostable, and emit fluorescence in the near infrared region. Natural killer (NK) cells and monocytes are part of the innate immune system and are crucial to the control of carcinogenesis. FND-mediated stimulation of these cells may serve as a strategy to enhance anti-tumor activity. FNDs were fabricated with a diameter of 70±28 nm. Innate immune cell FND uptake, viability, surface marker expression, and cytokine production were evaluated in vitro. Evaluation of fluorescence emission from the FNDs was conducted in an animal model. In vitro results demonstrated that treatment of immune cells with FNDs resulted in significant dose-dependent FND uptake, no compromise in cell viability, and immune cell activation. FNDs were visualized in an animal model. Hence, FNDs may serve as novel agents with "track and trace" capabilities to stimulate innate immune cell anti-tumor responses, especially as FNDs are amenable to surface-conjugation with immunomodulatory molecules.

Role of Nanodiamonds in Drug Delivery and Stem Cell Therapy

CONTEXT

The use of nanotechnology in medicine and more specifically drug delivery is set to spread rapidly. Currently many substances are under investigation for drug delivery and more specifically for cancer therapy.

EVIDENCE ACQUISITION

Nanodiamonds (NDs) have contributed significantly in the development of highly efficient and successful drug delivery systems, and in stem cell therapy. Drug delivery through NDs is an intricate and complex process that deserves special attention to unravel underlying molecular mechanisms in order to overcome certain bottlenecks associated with it. It has already been established that NDs based drug delivery systems have excellent biocompatibility, nontoxicity, photostability and facile surface functionalization properties.

RESULTS

There is mounting evidence that suggests that such conjugated delivery systems well retain the properties of nanoparticles like small size, large surface area to volume ratio that provide greater biocatalytic activity to the attached drug in terms of selectivity, loading and stability.

CONCLUSIONS

NDs based drug delivery systems may form the basis for the development of effective novel drug delivery vehicles with salient features that may facilitate their utility in fluorescence imaging, target specificity and sustainedrelease.

A review on fluorescent inorganic nanoparticles for optical sensing applications

Fluorescent inorganic nanoparticles are immerging novel materials that can be adopted for a large number of optical bioassays and chemical sensing probes.

Science and engineering of nanodiamond particle surfaces for biological applications (Review)

Diamond has outstanding bulk properties such as super hardness, chemical inertness, biocompatibility, luminescence, to name just a few. In the nanoworld, in order to exploit these outstanding bulk properties, the surfaces of nanodiamond (ND) particles must be accordingly engineered for specific applications. Modification of functional groups on the ND's surface and the corresponding electrostatic properties determine their colloidal stability in solvents, formation of photonic crystals, controlled adsorption and release of cargo molecules, conjugation with biomolecules and polymers, and cellular uptake. The optical activity of the luminescent color centers in NDs depends on their proximity to the ND's surface and surface termination. In order to engineer the ND surface, a fundamental understanding of the specific structural features and sp(3)-sp(2) phase transformations on the surface of ND particles is required. In the case of ND particles produced by detonation of carbon containing explosives (detonation ND), it should also be taken into account that its structure depends on the synthesis parameters and subsequent processing. Thus, for development of a strategy of surface modification of detonation ND, it is imperative to know details of its production. In this review, the authors discuss ND particles structure, strategies for surface modification, electrokinetic properties of NDs in suspensions, and conclude with a brief overview of the relevant bioapplications.

Nanodiamonds and silicon quantum dots: ultrastable and biocompatible luminescent nanoprobes for long-term bioimaging

Ultra-stability and low-toxicity of silicon quantum dots and fluorescent nanodiamonds for long-termin vitroandin vivobioimaging are demonstrated.