Detonation nanodiamonds have found numerous potential applications in a diverse array of fields such as biomedical imaging and drug delivery. Here, we systematically characterized non-functionalized ...and polyglycerol-functionalized detonation nanodiamond particles (DNPs) dispersed in aqueous suspensions at different ionic strengths (∼1.0 × 10
to 1.0 × 10
M) via dynamic light scattering and cryogenic transmission electron microscopy. For these colloidal suspensions, the total potential energies of interactions between a pair of DNPs were theoretically calculated using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory plus the fitting of the Boltzmann distribution to the interparticle spacing distribution of the colloidal DNPs. These investigations revealed that the non-functionalized DNPs are dispersed in aqueous media through the long-range (>10 nm) and weak (<7
) electrical double-layer repulsive interaction, while the driving force on dispersion of polyglycerol-functionalized DNPs is mostly derived from the short-range (<2 nm) and strong (∼55
) steric repulsive potential barrier generated by the polyglycerol. Moreover, our results show that the truly monodispersed and individually dispersed DNP colloids, forming no aggregates in aqueous suspensions, are available by both functionalizing DNPs by polyglycerol and increasing ionic strength of suspending media to ≳1.0 × 10
M.
Monosized (∼4 nm) diamond nanoparticles arranged on substrate surfaces are exciting candidates for single-photon sources and nucleation sites for ultrathin nanocrystalline diamond film growth. The ...most commonly used technique to obtain substrate-supported diamond nanoparticles is electrostatic self-assembly seeding using nanodiamond colloidal suspensions. Currently, monodisperse nanodiamond colloids, which have a narrow distribution of particle sizes centering on the core particle size (∼4 nm), are available for the seeding technique on different substrate materials such as Si, SiO2, Cu, and AlN. However, the self-assembled nanoparticles tend to form small (typically a few tens of nanometers or even larger) aggregates on all of those substrate materials. In this study, this major weakness of self-assembled diamond nanoparticles was solved by modifying the salt concentration of nanodiamond colloidal suspensions. Several salt concentrations of colloidal suspensions were prepared using potassium chloride as an inserted electrolyte and were examined with respect to seeding on SiO2 surfaces. The colloidal suspensions and the seeded surfaces were characterized by dynamic light scattering and atomic force microscopy, respectively. Also, the interaction energies between diamond nanoparticles in each of the examined colloidal suspensions were compared on the basis of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. From these investigations, it became clear that the appropriate salt concentration suppresses the formation of small aggregates during the seeding process owing to the modified electrostatic repulsive interaction between nanoparticles. Finally, monosized (<10 nm) individual diamond nanoparticles arranged on SiO2 surfaces have been successfully obtained.
Silicon vacancy (SiV) color centers in diamond have attracted widespread attention owing to their stable photoluminescence (PL) with a sharp emission band in the near-infrared region (ZPL 738 nm). ...Especially, SiV center containing single-digit nanometer-sized nanodiamonds (single-digit SiV-NDs) are desirable for various applications such as bioimaging and biosensing because of their extremely small size, comparable to many biomaterials. Therefore, several attempts have been made to fabricate the single-digit SiV-NDs. However, there are no reports on the successful fabrication of such materials in reasonable scale of production. Here, we report the successful synthesis of single-digit SiV-NDs via straightforward detonation process, which is known to have the high productivity in fabrication of single-digit NDs. Triphenylsilanol (TPS), as a silicon source, was mixed with explosives (TPS/TNT/RDX = 1/59/40 wt%) and the detonation process was carried out. The obtained single-digit NDs exhibit PL at approximately 738 nm, indicating that single-digit SiV-NDs were successfully synthesized. Moreover, we conjectured that the physics behind this achievement may be attributed to the aromatic ring of TPS under the consideration of ND formation mechanism newly built up based on the results of time-resolved optical emission measurements for the detonation reaction.
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•SiV centers in diamond are provided for various bioapplications.•SiV center-containing single-digit nanometer NDs were synthesized directly by detonation process.•Detonation with triphenylsilanol as a silicon source allowed to incorporate SiV centers into DNDs.•SiV centers in DNDs showed sharp PL emission peak centered at the ZPL = 738 nm.•Optical measurement of the detonation reaction revealed the physics behind the creation of SiV centers.
► ERK-mediated signaling activity in RPE cells is elevated quickly (in 30min) upon retinectomy. ► MEK–ERK signaling is intensified by itself through up-regulation of the expression of constituent ...molecules in the pathway. ► Blockade of initial MEK–ERK signaling inhibits cell-cycle re-entry of RPE cells.
Adult newt retinal pigment epithelium (RPE) cells are mitotically quiescent in the physiological condition, but upon a traumatic injury of the neural retina (NR) they re-enter the cell-cycle and eventually regenerate the missing NR. Here, to understand the mechanism underlying the cell-cycle re-entry of RPE cells following NR injury, we first investigated changes in MEK–ERK signaling activity in RPE cells upon removal of the NR (retinectomy) from the eye of living animals, and found that ERK-mediated signaling activity is elevated quickly (in 30min) upon retinectomy. In addition, we found, in in vitro analyses, that immediate early activation of MEK–ERK signaling may occur in RPE cells upon NR injury, intensifying the MEK–ERK signaling itself through up-regulation of the expression of constituent molecules in the pathway, and that 1-h blockade of such early MEK–ERK signaling interferes with the cell-cycle re-entry, which occurs 5–10 days later. Together, these results provide us with insight that elevation of MEK–ERK signaling activity upon NR injury may be a key process for mitotically quiescent RPE cells to re-enter the cell-cycle, leading to retinal regeneration.
Detonation nanodiamond (DND) is the smallest class of diamond nanocrystal capable of hosting various color centers with a size akin to molecular pores. Their negatively charged nitrogen-vacancy ...center (NV−) is a versatile tool for sensing a wide range of physical and even chemical parameters at the nanoscale. The NV− is, therefore, attracting interest as the smallest quantum sensor in biological research. Nonetheless, recent NV− enhancement in DND has yet to yield sufficient fluorescence per particle, leading to efforts to incorporate other group-IV color centers into DND. An example is adding a silicon dopant to the explosive mixture to create negatively charged silicon-vacancy centers (SiV−). In this paper, we report on efficient observation (∼50% of randomly selected spots) of the characteristic optically detected magnetic resonance (ODMR) NV− signal in silicon-doped DND (Si-DND) subjected to boiling acid surface cleaning. The NV− concentration is estimated by continuous-wave electron spin resonance spectroscopy to be 0.35 ppm without the NV− enrichment process. A temperature sensitivity of 0.36K/Hz in an NV− ensemble inside an aggregate of Si-DND is achieved via the ODMR-based technique. Transmission electron microscopy survey reveals that the Si-DNDs core sizes are ∼11.2 nm, the smallest among the nanodiamond’s temperature sensitivity studies. Furthermore, temperature sensing using both SiV− (all-optical technique) and NV− (ODMR-based technique) in the same confocal volume is demonstrated, showing Si-DND’s multimodal temperature sensing capability. The results of the study thereby pave a path for multi-color and multimodal biosensors and for decoupling the detected electrical field and temperature effects on the NV− center.
Diamond nanoparticles (DNPs) are expected as splendid coating materials to give, e.g. corrosion resistance, anti-bacterial properties, and antireflection function. In this paper, we demonstrate a ...technique of electrostatic layer-by-layer deposition of DNPs onto substrate surfaces using DNP colloidal suspensions with different signs of zeta potentials alternately. The formed DNP layers are investigated in terms of film thickness, surface roughness, and homogeneity. Plus, those morphologies of DNP layers are theoretically correlated with the colloidal properties of DNP suspensions based on the electrostatic interaction potential energy between colloidal DNPs and substrate surfaces. Consequently, it turns out that the demonstrated technique enables formation of DNP thin layers with desired thickness, particle density, and surface roughness on substrate surfaces by controlling the ionic strength of colloidal DNPs.
The adult newt has the remarkable ability to regenerate a functional retina from retinal pigment epithelium (RPE) cells, even when the neural retina (NR) is completely lost from the eye. In this ...system, RPE cells are reprogrammed into a unique state of multipotent cells, named RPESCs, in an early phase of retinal regeneration. However, the signals that trigger reprogramming remain unknown. Here, to approach this issue we focused on Pax6, a transcription factor known to be expressed in RPESCs. We first identified four classes (v1, v2, v3 and v4) of Pax6 variants in the eye of adult newt, Cynops pyrrhogaster. These variants were expressed in most tissues of the intact eye in different combinations but not in the RPE, choroid or sclera. On the basis of this information, we investigated the expression of Pax6 in RPE cells after the NR was removed from the eye by surgery (retinectomy), and found that two classes (v1 and v2) of Pax6 variants were newly expressed in RPE cells 10 days after retinectomy, both in vivo and in vitro (RLEC system). In the RLEC system, we found that Pax6 expression is mediated through a pathway separate from the MEK-ERK pathway, which is required for cell cycle re-entry of RPE cells. These results predict the existence of a pathway that may be of fundamental importance to a better understanding of the reprogramming of RPE cells in vivo.
Summary
The onset mechanism of proliferation in mitotically quiescent retinal pigment epithelium (RPE) cells is still obscure in humans and newts, although it can be a clinical target for ...manipulating both retinal diseases and regeneration. To address this issue, we investigated factors or signaling pathways involved in the first cell‐cycle entry of RPE cells upon retinal injury using a newt retina‐less eye‐cup culture system in which the cells around the wound edge of the RPE exclusively enter the cell cycle. We found that MEK–ERK signaling is necessary for their cell‐cycle entry, and signaling pathways whose activities can be modulated by heparin, such as Wnt‐, Shh‐, and thrombin‐mediated pathways, are capable of regulating the cell‐cycle entry. Furthermore, we found that the cells inside the RPE have low proliferation competence even in the presence of serum, suggesting inversely that a loss of cell‐to‐cell contact would allow the cells to enter the cell cycle.
•X-ray photoelectron diffraction (XPD) is a fruit of advancement of X-ray photoelectron spectroscopy (XPS).•XPD is now a handy method for determining non-destructively the near-surface atomic ...structures.•Insulating materials, however, cause nuisance charging effects in XPS and XPD.•A simple method of sample treatment for angle-scan XPD for insulating diamond is demonstrated.•This simple method may be applied in principle to any insulating material.
A simple method of sample treatment for angle-scan X-ray photoelectron diffraction (XPD) for insulating diamond is demonstrated. The resulting XPD patterns have shown that a quantitative measure of near-surface atomic order is obtained for the insulating diamond. This simple method may be applied in principle to any insulating material, which enables non-destructive characterization of near-surface order of insulating materials by XPD.
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