Nanodiamonds as vehicles for systemic and localized drug delivery

Precise surface engineering: Leveraging chemical vapor deposition for enhanced biocompatibility and durability in biomedical implants

Biomedical implants have revolutionized modern medicine, providing diverse treatment options for various medical conditions. Ensuring the long-term success of certain materials used in various applications requires careful consideration of their ability to interact with biological systems and withstand harsh biological conditions. Optimizing surface properties is crucial for successfully integrating biomedical implants into the human body, ensuring biocompatibility, durability, and functionality. Chemical Vapor Deposition (CVD) has become a crucial technology in surface engineering, offering a precise technique for applying thin films with customized properties. This article provides a comprehensive study of surface engineering for biomedical implants, specifically emphasizing the CVD coating technique. By carefully manipulating chemical reactions in the vapor phase, CVD allows for the creation of coatings that enhance wear resistance, minimize friction, and improve biocompatibility. This review also explores the underlying principles of CVD, the various process parameters involved, and the subsequent enhancements in implant performance. Using case studies and experimental findings, it showcases the ability of CVD to greatly enhance the durability and effectiveness of biomedical implants.

Tritium-Labeled Nanodiamonds as an Instrument to Analyze Bioprosthetic Valve Coatings: A Case of Using a Nanodiamond Containing Coating on a Pork Aorta

Coatings with xenogenic materials, made of detonation nanodiamonds, provide additional strength and increase elasticity. A functionally developed surface of nanodiamonds makes it possible to apply antibiotics. Previous experiments show the stability of such coatings; however, studies on stability in the bloodstream and calcification of the material in natural conditions have yet to be conducted. Tritium-labeled nanodiamonds (negative and positive) were obtained by the tritium activation method and used to develop coatings for a pork aorta to analyze their stability in a pig's bloodstream using a radiotracer technique. A chitosan layer was applied from a solution of carbonic acid under high-pressure conditions to prevent calcification. The obtained materials were used to prepare a porcine conduit, which was surgically stitched inside the pig's aorta for four months. The aorta samples, including nanodiamond-coated and control samples, were analyzed for nanodiamond content and calcium, using the radiotracer and ICP-AES methods. A histological analysis of the materials was also performed. The obtained coatings illustrate a high in vivo stability and low levels of calcification for all types of nanodiamonds. Even though we did not use additional antibiotics in this case, the development of infection was not observed for negatively charged nanodiamonds, opening up prospects for their use in developing coatings.

Levofloxacin and Amikacin Adsorption on Nanodiamonds: Mechanism and Application Prospects

This research is focused on the adsorption modification of detonation nanodiamond surfaces with antibiotics for their further use as smart materials for cardiovascular surgery purposes, namely as bioprostheses modifiers. Tritium-labeled amikacin and levofloxacin were used as tracers for the adsorption process control. We found that nanodiamonds form adsorption complexes with levofloxacin via physical adsorption, while in the case of amikacin, electrostatic attraction contributes to the formation of more stable complexes, even in the presence of electrolytes and desorbing agents (models of biological fluids). Antimicrobial characterization of nanodiamond–levofloxacin and nanodiamond–amikacin complexes indicates a reduction in the dose of antibiotics that is used as an antimicrobial agent. Therefore, the use of biomaterial based on DND complexes with antibiotics as the basis of bioprostheses will allow one either to avoid or significantly reduce the duration and intensity of antibiotics use in the postoperative period, which is critically important from the viewpoint of the development of antibiotic resistance in pathogens.

Nanoscale Diamond-Based Formulation as an Immunomodulator and Potential Therapeutic for Lymphoma

Integrative medicine practices, such as Ayurveda, are popular in India and many South Asian countries, yet basic research to investigate the concepts, procedures, and medical benefits of ayurvedic products has received little attention and is not fully understood. Here, we report a functional nanodiamond-based traditional Ayurvedic herbomineral formulation, Heerak Bhasma (Ayu_ND), for the treatment of solid tumors called Dalton’s lymphoma generated in CD1 mice. Ayu_ND-mediated immunostimulation significantly reduces tumor cell proliferation and induces apoptosis aided by the active participation of dendritic cells. Immunomodulatory Ayu_ND treatment is highly immunostimulatory and drives dendritic cells to produce TNF-α. Treatment with Ayu_ND significantly reduces the tumor volume, inhibits metastasis in distant vascularized organs, and increases the life span of tumor-bearing animals compared with untreated littermates. These events were associated with elevated serum levels of the protective cytokines IFN-γ and TNF-α and downregulated the disease, exacerbating TGF-β. Ayu_ND-mediated therapeutic success was also accompanied by the depletion of regulatory T cells and enhanced vaccine-induced T-cell immunity, guided by the restoration of the memory CD8⁺ T-cell pool and prevention of PD-1-mediated T cell exhaustion. The results provide a basis for further evaluation of ayurvedic formulations and drug efficacy in treating cancers.

Nanotechnology in Colorectal Cancer for Precision Diagnosis and Therapy

Colorectal cancer (CRC) is the third most frequently occurring tumor in the human population. CRCs are usually adenocarcinomatous and originate as a polyp on the inner wall of the colon or rectum which may become malignant in the due course of time. Although the therapeutic options of CRC are limited, the early diagnosis of CRC may play an important role in preventive and therapeutic interventions to decrease the mortality rate. The CRC-affected tissues exhibit several molecular markers that may be exploited as the novel strategy to develop newer approaches for the treatment of the disease. Nanotechnology consists of a wide array of innovative and astonishing nanomaterials with both diagnostics and therapeutic potential. Several nanomaterials and nano formulations such as Carbon nanotubes, Dendrimer, Liposomes, Silica Nanoparticles, Gold nanoparticles, Metal-organic frameworks, Core-shell polymeric nano-formulations, Nano-emulsion System, etc can be used to targeted anticancer drug delivery and diagnostic purposes in CRC. The light-sensitive photosensitizer drugs loaded gold and silica nanoparticles can be used to diagnose as well as the killing of CRC cells by the targeted delivery of anticancer drugs to cancer cells. This review is focused on the recent advancement of nanotechnology in the diagnosis and treatment of CRC.

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.

Predicting structure/property relationships in multi-dimensional nanoparticle data using t-distributed stochastic neighbour embedding and machine learning

Combining researchers' domain expertise and advanced dimension reduction methods we demonstrate how visually comparing the distribution of nanoparticles mapped from multiple dimensions to a two dimensional plane can rapidly identify possible single-structure/property relationships and to a lesser extent multi-structure/property relationships. These relationships can be further investigated and confirmed with machine learning, using genetic programming to inform the choice of property-specific models and their hyper-parameters. In the case of our nanodiamond case study, we visually identify and confirm a strong relationship between the size and the probability of observation (stability) and a more complicated (and visually ambiguous) relationship between the ionisation potential and band gaps with a range of different structural, chemical and statistical surface features, making it more difficult to engineer in practice.

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.

Toxicology in the Super-Resolution Era

Light microscopy has played a central role in science for the past couple of hundred years and will continue to do so. Multiple super-resolution microscopy techniques have been in the headlines for smashing what for more than 100+ years was believed to be the limits of optical microscopy. This resolution improvement enables the visualization of molecular structures and processes on the nano scale. While certain scientific questions in toxicology can benefit from modalities within the super-resolution suite, due diligence is required for efficiency and to achieve optimal results. For a given hypothesis being tested, there are biophysical issues that need to be considered before heading down the super-resolution road. All commercially available super-resolution modalities, along with cautions and tips, will be discussed. © 2019 by John Wiley & Sons, Inc.

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.

The Response of HeLa Cells to Fluorescent NanoDiamond Uptake

Fluorescent nanodiamonds are promising probes for nanoscale magnetic resonance measurements. Their physical properties predict them to have particularly useful applications in intracellular analysis. Before using them in intracellular experiments however, it should be clear whether diamond particles influence cell biology. While cytotoxicity has already been ruled out in previous studies, we consider the non-fatal influence of fluorescent nanodiamonds on the formation of reactive oxygen species (an important stress indicator and potential target for intracellular sensing) for the first time. We investigated the influence of different sizes, shapes and concentrations of nanodiamonds on the genetic and protein level involved in oxidative stress-related pathways of the HeLa cell, an important model cell line in research. The changes in viability of the cells and the difference in intracellular levels of free radicals, after diamond uptake, are surprisingly small. At lower diamond concentrations, the cellular metabolism cannot be distinguished from that of untreated cells. This research supports the claims of non-toxicity and includes less obvious non-fatal responses. Finally, we give a handhold concerning the diamond concentration and size to use for non-toxic, intracellular measurements in favour of (cancer) research in HeLa cells.

Uptake and intracellular accumulation of diamond nanoparticles - a metabolic and cytotoxic study

Diamond nanoparticles, known as nanodiamonds (NDs), possess several medically significant properties. Having a tailorable and easily accessible surface gives them great potential for use in sensing and imaging applications and as a component of cell growth scaffolds. In this work we investigate in vitro interactions of human osteoblast-like SAOS-2 cells with four different groups of NDs, namely high-pressure high-temperature (HPHT) NDs (diameter 18-210 nm, oxygen-terminated), photoluminescent HPHT NDs (diameter 40 nm, oxygen-terminated), detonation NDs (diameter 5 nm, H-terminated), and the same detonation NDs further oxidized by annealing at 450 °C. The influence of the NDs on cell viability and cell count was measured by the mitochondrial metabolic activity test and by counting cells with stained nuclei. The interaction of NDs with cells was monitored by phase contrast live-cell imaging in real time. For both types of oxygen-terminated HPHT NDs, the cell viability and the cell number remained almost the same for concentrations up to 100 µg/mL within the whole range of ND diameters tested. The uptake of hydrogen-terminated detonation NDs caused the viability and the cell number to decrease by 80-85%. The oxidation of the NDs hindered the decrease, but on day 7, a further decrease was observed. While the O-terminated NDs showed mechanical obstruction of cells by agglomerates preventing cell adhesion, migration and division, the H-terminated detonation NDs exhibited rapid penetration into the cells from the beginning of the cultivation period, and also rapid cell congestion and a rapid reduction in viability. These findings are discussed with reference to relevant properties of NDs such as surface chemical bonds, zeta potential and nanoparticle types.

Heterogeneous PEGylation of diamond nanoparticles

Coating the surfaces of inorganic nanoparticles with polyethylene glycol (PEG) is an important step in the development of many nanoparticle-based drug delivery systems. The efficiency with which drug molecules can be loaded on to nanoparticle surfaces is contingent on the concentration, distribution and stability of the PEG coating. In this study the distribution and relative stability of PEG on diamond nanoparticles is predicted, for clean and passivated surface structures, in 3D. This is an ideal exemplar, since PEGylated diamond nanoparticles are already being trialed as carriers for doxorubicin (DOX). The results show that PEGylation is favorable near the {100} facets regardless of surface reconstructions or pre-treatment, but pre-treatment is required to increase the probability of stable and homogeneous PEGylation on other facets.

Diamond nanostructures for drug delivery, bioimaging, and biosensing

This review summarizes the superior properties of diamond nanoparticles and vertically aligned diamond nanoneedles and their applications in biosensing, bioimaging and drug delivery.

Impact of speciation on the electron charge transfer properties of nanodiamond drug carriers

Unpassivated diamond nanoparticles (bucky-diamonds) exhibit a unique surface reconstruction involving graphitization of certain crystal facets, giving rise to hybrid core-shell particles containing both aromatic and aliphatic carbon. Considerable effort is directed toward eliminating the aromatic shell, but persistent graphitization of subsequent subsurface-layers makes perdurable purification a challenge. In this study we use some simple statistical methods, in combination with electronic structure simulations, to predict the impact of different fractions of aromatic and aliphatic carbon on the charge transfer properties of the ensembles of bucky-diamonds. By predicting quality factors for a variety of cases, we find that perfect purification is not necessary to preserve selectivity, and there is a clear motivation for purifying samples to improve the sensitivity of charge transfer reactions. This may prove useful in designing drug delivery systems where the release of (selected) drugs needs to be sensitive to specific conditions at the point of delivery.

Site-dependent atomic and molecular affinities of hydrocarbons, amines and thiols on diamond nanoparticles

Like many of the useful nanomaterials being produced on the industrial scale, the surface of diamond nanoparticles includes a complicated mixture of various atomic and molecular adsorbates, attaching to the facets following synthesis. Some of these adsorbates may be functional, and adsorption is encouraged to promote applications in biotechnology and nanomedicine, but others are purely adventurous and must be removed prior to use. In order to devise more effective treatments it is advantageous to know the relative strength of the interactions of the adsorbates with the surface, and ideally how abundant they are likely to be under different conditions. In this paper we use a series of explicit electronic structure simulations to map the distribution of small hydrocarbons, amines and thiols on a 2.9 nm diamond nanoparticle, with atomic level resolution, in 3-D. We find a clear relationship between surface reconstructions, facet orientation, and the distribution of the different adsorbates; with a greater concentration expected on the (100) and (110) facets, particularly when the supersaturation in the reservoir is high. Adsorption on the (111) facets is highly unlikely, suggesting that controlled graphitization may be a useful stage in the cleaning and treatment of nanodiamonds, prior to the deliberate coating with functional adsorbates needed for drug delivery applications.

Challenges in modelling nanoparticles for drug delivery

Although there have been significant advances in the fields of theoretical condensed matter and computational physics, when confronted with the complexity and diversity of nanoparticles available in conventional laboratories a number of modeling challenges remain. These challenges are generally shared among application domains, but the impacts of the limitations and approximations we make to overcome them (or circumvent them) can be more significant one area than another. In the case of nanoparticles for drug delivery applications some immediate challenges include the incompatibility of length-scales, our ability to model weak interactions and solvation, the complexity of the thermochemical environment surrounding the nanoparticles, and the role of polydispersivity in determining properties and performance. Some of these challenges can be met with existing technologies, others with emerging technologies including the data-driven sciences; some others require new methods to be developed. In this article we will briefly review some simple methods and techniques that can be applied to these (and other) challenges, and demonstrate some results using nanodiamond-based drug delivery platforms as an exemplar.

Nanodiamond–PMO for two-photon PDT and drug delivery

We report nanodiamond–PMO nanosystems which generate ROS upon two-photon excitation.

One-component nanomedicine

One-component nanomedicine (OCN) represents an emerging class of therapeutic nanostructures that contain only one type of chemical substance. This one-component feature allows for fine-tuning and optimization of the drug loading and physicochemical properties of nanomedicine in a precise manner through molecular engineering of the underlying building blocks. Using a precipitation procedure or effective molecular assembly strategies, molecularly crafted therapeutic agents (e.g. polymer-drug conjugates, small molecule prodrugs, or drug amphiphiles) could involuntarily aggregate, or self-assemble into nanoscale objects of well-defined sizes and shapes. Unlike traditional carrier-based nanomedicines that are inherently multicomponent systems, an OCN does not require the use of additional carriers and could itself possess desired physicochemical features for preferential accumulation at target sites. We review here recent progress in the molecular design, conjugation methods, and fabrication strategies of OCN, and analyze the opportunities that this emerging platform could open for the new and improved treatment of devastating diseases such as cancer.

Improving surface and defect center chemistry of fluorescent nanodiamonds for imaging purposes--a review

Diamonds are widely used for jewelry owing to their superior optical properties accounting for their fascinating beauty. Beyond the sparkle, diamond is highly investigated in materials science for its remarkable properties. Recently, fluorescent defects in diamond, particularly the negatively charged nitrogen-vacancy (NV(-)) center, have gained much attention: The NV(-) center emits stable, nonbleaching fluorescence, and thus could be utilized in biolabeling, as a light source, or as a Förster resonance energy transfer donor. Even more remarkable are its spin properties: with the fluorescence intensity of the NV(-) center reacting to the presence of small magnetic fields, it can be utilized as a sensor for magnetic fields as small as the field of a single electron spin. However, a reproducible defect and surface and defect chemistry are crucial to all applications. In this article we review methods for using nanodiamonds for different imaging purposes. The article covers (1) dispersion of particles, (2) surface cleaning, (3) particle size selection and reduction, (4) defect properties, and (5) functionalization and attachment to nanostructures, e.g., scanning probe microscopy tips.

Size and shape dependent deprotonation potential and proton affinity of nanodiamond

Many important reactions in biology and medicine involve proton abstraction and transfer, and it is integral to applications such as drug delivery. Unlike electrons, which are quantum mechanically delocalized, protons are instantaneously localized on specific residues in these reactions, which can be a distinct advantage. However, the introduction of nanoparticles, such as non-toxic nanodiamonds, to this field complicates matters, as the number of possible sites increases as the inverse radius of the particle. In this paper we present > 10(4) simulations that map the size- and shape-dependence of the deprotonation potential and proton affinity of nanodiamonds in the range 1.8-2.7 nm in average diameter. We find that while the average deprotonation potential and proton affinities decrease with size, the site-specific values are inhomogeneous over the surface of the particles, exhibiting strong shape-dependence. The proton affinity is strongly facet-dependent, whereas the deprotonation potential is edge/corner-dependent, which creates a type of spatial hysteresis in the transfer of protons to and from the nanodiamond, and provides new opportunities for selective functionalization.

Anisotropic adsorption and distribution of immobilized carboxyl on nanodiamond

Stable and predictable functionalization of nanodiamond with carboxyl is an important first step in loading these materials with therapeutic agents, and the conjugation with proteins, cytochrome, antigen, and DNA. By creating a map of the adsorption strength of COOH, OH, O and H with atomic level resolution across the entire surface of an experimentally realistic nanodiamond, we have shown how the distribution is highly anisotropic, and depends on surface reconstructions, facet orientation, and ultimately the shape. This provides useful insights into how the structure of nanodiamond impacts the formation of COOH surface monolayers, and suggests that efforts to separate nanodiamonds by shape would be highly beneficial in the development of drug delivery vehicles targeted to specific treatment regimes.

Nanodiamond-mediated impairment of nucleolar activity is accompanied by oxidative stress and DNMT2 upregulation in human cervical carcinoma cells

Because applications of nanomaterials in nanomedicine and nanotechnology are rapidly increasing, nanodiamond (ND) health risk assessment is urgently needed. In the present study, we used HeLa cell model to evaluate nanodiamond biocompatibility. We found ND-mediated cytotoxicity, proliferation inhibition and oxidative stress. Conversely, ND-associated genotoxicity was limited to higher concentrations used. Nanodiamond was also recognized as a hypermethylating agent. ND-associated redox imbalance contributed to nucleolar stress: size and number of nucleoli were affected, and release of nucleolar protein RRN3 occurred. Surprisingly, we did not observe stress-induced RNA depletion. In contrast, RNA was stabilized: total RNA level and integrity (28S/18S rRNA ratio) were unaffected. After nanodiamond treatment, upregulation of DNA methyltransferase 2 (DNMT2) was shown. Perhaps, DNMT2, as a part of the regulatory loop of metabolic pathways through RNA methylation, may contribute to RNA stabilization and confer stress resistance after nanodiamond treatment. In conclusion, using HeLa cell model, we showed that ND biocompatibility is limited and special care should be taken when introducing ND-based biomaterials to biological systems.

Nanodiamond-mitoxantrone complexes enhance drug retention in chemoresistant breast cancer cells

Chemoresistance is a prevalent issue that accounts for the vast majority of treatment failure outcomes in metastatic cancer. Among the mechanisms of resistance that markedly decrease treatment efficacy, the efflux of drug compounds by ATP-binding cassette (ABC) transporter proteins can impair adequate drug retention by cancer cells required for therapeutic cytotoxic activity. Of note, ABC transporters are capable of effluxing several classes of drugs that are clinical standards, including the anthracyclines such as doxorubicin, as well as anthracenediones such as mitoxantrone. To address this challenge, a spectrum of nanomaterials has been evaluated for improved drug retention and enhanced efficacy. Nanodiamonds (NDs) are emerging as a promising nanomaterial platform because they integrate several important properties into a single agent. These include a uniquely faceted truncated octahedral architecture that enables potent drug binding and dispersibility in water, scalably processed ND particles with uniform diameters of approximately 5 nm, and a demonstrated ability to improve drug tolerance while delaying tumor growth in multiple preclinical models, among others. This work describes a ND–mitoxantrone complex that can be rapidly synthesized and mediates marked improvements in drug efficacy. Comprehensive complex characterization reveals a complex with favorable drug delivery properties that is capable of improving drug retention and efficacy in an MDA-MB-231-luc-D3H2LN (MDA-MB-231) triple negative breast cancer cell line that was lentivirally transduced for resistance against mitoxantrone. Findings from this study support the further evaluation of ND–MTX in preclinical dose escalation and safety studies toward potentially clinical validation.

Nanodiamonds-mediated doxorubicin nuclear delivery to inhibit lung metastasis of breast cancer

Lung metastasis is one of the greatest challenges for breast cancer treatment. Here, a nanodiamonds (NDs)-mediated doxorubicin (DOX) delivery system was first designed to inhibit the lung metastasis of breast cancer effectively. DOX was non-covalently bound to NDs via physical adsorption in an aqueous solution, then DSPE-PEG 2K was coated to the NDs-DOX complex (NDX) to increase the dispersibility and prolong the circulation time. DSPE-PEG 2K coating NDX (DNX) displayed high drug loading and excellent ability to deliver DOX to the nucleus, thereby significantly enhancing cytotoxicity and inducing cell apoptosis. Furthermore, DNX showed good histocompatibility and could improve drug accumulation in lung, as a result, markedly inhibited the lung metastasis of breast cancer. The high anti-metastasis efficacy with the decreased systemic toxicity suggested that DNX could be a promising drug delivery system for the therapy of lung metastasis of breast cancer.

Core-shell designs of photoluminescent nanodiamonds with porous silica coatings for bioimaging and drug delivery II: application

Recent advances within materials science and its interdisciplinary applications in biomedicine have emphasized the potential of using a single multifunctional composite material for concurrent drug delivery and biomedical imaging. Here we present a novel composite material consisting of a photoluminescent nanodiamond (ND) core with a porous silica (SiO2) shell. This novel multifunctional probe serves as an alternative nanomaterial to address the existing problems with delivery and subsequent tracing of the particles. Whereas the unique optical properties of ND allows for long-term live cell imaging and tracking of cellular processes, mesoporous silica nanoparticles (MSNs) have proven to be efficient drug carriers. The advantages of both ND and MSNs were hereby integrated in the new composite material, ND@MSN. The optical properties provided by the ND core rendered the nanocomposite suitable for microscopy imaging in fluorescence and reflectance mode, as well as super-resolution microscopy as a STED label; whereas the porous silica coating provided efficient intracellular delivery capacity, especially in surface-functionalized form. This study serves as a demonstration how this novel nanomaterial can be exploited for both bioimaging and drug delivery for future theranostic applications.

Nanoparticles assume electrical potential according to substrate, size, and surface termination

Electrical potential of nanoparticles under relevant environment is substantial for their applications in electronics as well as sensors and biology. Here, we use Kelvin force microscopy to characterize electrical properties of semiconducting diamond nanoparticles (DNPs) of 5-10 nm nominal size and metallic gold nanoparticles (20 and 40 nm) on Si and Au substrates under ambient conditions. The DNPs are deposited on Si and Au substrates from dispersions with well-defined zeta-potential. We show that the nanoparticle potential depends on its size and that the only reliable potential characteristic is a linear fit of this dependence within a 5-50 nm range. Systematically different potentials of hydrogenated, oxidized, and graphitized DNPs are resolved using this methodology. The differences are within 50 mV, that is much lower than on monocrystalline diamond. Furthermore, all of the nanoparticles assume their potential within -60 mV according to the Au and Si substrate, thus gaining up to 0.4 V difference. This effect is attributed to DNP charging by charge transfer and/or polarization. This is confirmed by secondary electron emission. Such effects are general with broad implications for nanoparticles applications.

Silicon vacancy color center photoluminescence enhancement in nanodiamond particles by isolated substitutional nitrogen on {100} surfaces

Fluorescent nanodiamonds were produced by incorporation of silicon-vacancy (Si-V) defect centers in as-received diamonds of averaged size ∼255 nm using microwave plasma chemical vapor deposition. The potential for further enhancement of Si-V emission in nanodiamonds (NDs) is demonstrated through controlled nitrogen doping by adding varying amounts of N(2) in a H(2) + CH(4) feedgas mixture. Nitrogen doping promoted strong narrow-band (FWHM ∼ 10 nm) emission from the Si-V defects in NDs, as confirmed by room temperature photoluminescence. At low levels, isolated substitutional nitrogen in {100} growth sectors is believed to act as a donor to increase the population of optically active (Si-V)(-) at the expense of optically inactive Si-V defects, thus increasing the observed luminescence from this center. At higher levels, clustered nitrogen leads to deterioration of diamond quality with twinning and increased surface roughness primarily on {111} faces, leading to a quenching of the Si-V luminescence. Enhancement of the Si-V defect through controlled nitrogen doping offers a viable alternative to nitrogen-vacancy defects in biolabeling/sensing applications involving sub-10 nm diamonds for which luminescent activity and stability are reportedly poor.

Biodistribution of amino-functionalized diamond nanoparticles. In vivo studies based on 18F radionuclide emission

Nanoparticles have been proposed for several biomedical applications; however, in vivo biodistribution studies to confirm their potential are scarce. Nanodiamonds are carbon nanoparticles that have been recently proposed as a promising biomaterial. In this study, we labeled nanodiamonds with (18)F to study their in vivo biodistribution by positron emission tomography. Moreover, the impact on the biodistribution of their kinetic particle size and of the surfactant agents has been evaluated. Radiolabeled diamond nanoparticles accumulated mainly in the lung, spleen, and liver and were excreted into the urinary tract. The addition of surfactant agents did not lead to significant changes in this pattern, with the exception of a slight reduction in the urinary excretion rate. On the other hand, after filtration of the radiolabeled diamond nanoparticles to remove those with a larger kinetic size, the uptake in the lung and spleen was completely inhibited and significantly reduced in the liver.

Visualization of interaction between inorganic nanoparticles and bacteria or fungi

PURPOSE

The objective of the present investigation was to evaluate the morphologic characteristics of self-assemblies of diamond (nano-D), silver (nano-Ag), gold (nano-Au), and platinum (nano-Pt) nanoparticles with Staphylococcus aureus (bacteria) and Candida albicans (fungi), to determine the possibility of constructing microorganism-nanoparticle vehicles.

METHODS

Hydrocolloids of individual nanoparticles were added to suspensions of S. aureus and C. albicans. Immediately after mixing, the samples were inspected by transmission electron microscopy.

RESULTS

Visualization of the morphologic interaction between the nanoparticles and microorganisms showed that nano-D, which are dielectrics and exhibit a positive zeta potential, were very different from the membrane potentials of microorganisms, and uniformly surrounded the microorganisms, without causing visible damage and destruction of cells. All metal nanoparticles with negative zeta potential had cell damaging properties. Nano-Ag showed the properties of self-organization with the cells, disintegrating the cell walls and cytoplasmic membranes, and releasing a substance (probably cytoplasm) outside the cell. Arrangement of nano-Au with microorganisms did not create a system of self-organization, but instead a "noncontact" interaction between the nanoparticles and microorganisms was observed to cause damage to fungal cells. Nano-Pt caused both microorganisms to release a substance outside the cell and disintegrated the cytoplasmic membrane and cell wall.

CONCLUSION

Nano-Ag, nano-Au, and nano-Pt (all metal nanoparticles) are harmful to bacteria and fungi. In contrast, nano-D bind closely to the surface of microorganisms without causing visible damage to cells, and demonstrating good self-assembling ability. The results indicate that both microorganisms could be used as potential carriers for nano-D.

Receptor-targeted nanocarriers for therapeutic delivery to cancer

Efficient and site-specific delivery of therapeutic drugs is a critical challenge in clinical treatment of cancer. Nano-sized carriers such as liposomes, micelles, and polymeric nanoparticles have been investigated for improving bioavailability and pharmacokinetic properties of therapeutics via various mechanisms, for example, the enhanced permeability and retention (EPR) effect. Further improvement can potentially be achieved by conjugation of targeting ligands onto nanocarriers to achieve selective delivery to the tumour cell or the tumour vasculature. Indeed, receptor-targeted nanocarrier delivery has been shown to improve therapeutic responses both in vitro and in vivo. A variety of ligands have been investigated including folate, transferrin, antibodies, peptides and aptamers. Multiple functionalities can be incorporated into the design of nanoparticles, e.g., to enable imaging and triggered intracellular drug release. In this review, we mainly focus on recent advances on the development of targeted nanocarriers and will introduce novel concepts such as multi-targeting and multi-functional nanoparticles.

Nanoparticles: Switching blinking on and off

Diamonds with a diameter of just 5 nm are capable of supporting colour centres and emitting fluorescence, and encapsulating these nanodiamonds in a polymer stops them blinking.