Controlled Formation of Porous 2D Lattices from C3 -symmetric Ph6 -Me-Tribenzotriquinacene-OAc3.

The on-surface self-assembly of molecules to form holey nanographenes is a promising approach to control the properties of the resulting 2D lattice. Usually, planar molecules are utilized to prepare flat, structurally confined molecular layers, with only a few recent examples of warped precursors. However, control of the superstructures is limited thus far. Herein, we report the temperature-controlled self-assembly of a bowl-shaped, acetylated C3 -symmetric hexaphenyltribenzotriquinacene derivative on Cu(111). Combining scanning tunneling microscopy (STM) and density functional theory (DFT) confirms the formation of highly differing arrangements starting with π-stacked bowl-to-bowl dimers at low coverage at room temperature via chiral honeycomb structures, an intermediate trigonal superstructure, followed by a fully carbon-based, flattened hexagonal superstructure formed by on-surface deacetylation, which is proposed as a precursor for holey graphene networks with unique defect structures.

Surface Control of Nanodiamond: From Homogeneous Termination to Complex Functional Architectures for Biomedical Applications.

Interest in nanodiamond (ND) has been spurred by its unique properties such as high biocompatibility, versatile surface chemistry, and the possibility to apply it as drug delivery agent, cross-linker, or coating and for sensing applications when luminescent lattice defects such as the NV centers are present in the crystal lattice. Currently, nanodiamond has been used for targeted drug delivery, phototherapeutic applications, and sensing and imaging in cellular environments and in vitro. Furthermore, suitably functionalized nanodiamond is a promising material for tissue engineering applications. However, the application of nanodiamond has long been hampered by a number of obstacles and challenges met with commercially available nanodiamonds of different origins. A major issue is related to the strong agglomeration of the individual particles resulting in covalently linked aggregates with larger sizes and a broad size distribution. Furthermore, the surface termination of typical nanodiamond particles tends to be rather inhomogeneous, containing a multitude of different functional groups. The retention of functionality of immobilized moieties for bioapplications is often not known. And finally, the surface of nanodiamond possesses a strong propensity for nonspecific interaction, especially proteins from serum, cell fluids, or the culture media used for the incubation of cells with nanodiamond. The resulting protein corona influences the possibility to access functional moieties on the diamond surface and leads to a reduced reproducibility of observations in physiological environments and a limited attribution of effects to the presence of the functional moieties on the diamond surface. In this Account, we describe our efforts to address these challenges using multiple strategies mainly for the example of detonation nanodiamond (DND). First, a homogeneous size distribution of the nanoparticles and an initial surface termination with a unique type of atoms or groups can be achieved using mechanochemical methods and treatments with different reagents in both solution and gas phases. Reactions in liquid media typically lead to more uniform results as the entire surface of the particles becomes equally accessible. We have then worked on the development of different covalent linker strategies to accommodate the grafting needs of different functional moieties and thus to enable the production of orthogonally functionalized ND particles, which can be modified with multiple moieties in a controlled fashion. The noncovalent immobilization of functional units is equally useful as it permits the conservation of functionality for sensitive proteins, which denature upon covalent immobilization. In summary, our work aims to gain full control over the surface properties of diamond nanoparticles and to develop a toolbox of chemical methods to provide functionalized and tailored nanodiamond for a plethora of biomedical applications. Further research in the field of diamond functionalization will cover also the transfer of already existing methods to other types of diamond surfaces, the production of stoichiometrically functionalized particles, the covalent and dynamic self-assembly of nanodiamond particles, and the continuing development of suitable characterization techniques.

Early dynamics of the emission of solvated electrons from nanodiamonds in water.

Solvated electrons are among the most reductive species in an aqueous environment. Diamond materials have been proposed as a promising source of solvated electrons, but the underlying emission process in water remains elusive so far. Here, we show spectroscopic evidence for the emission of solvated electrons from detonation nanodiamonds upon excitation with both deep ultraviolet (225 nm) and visible (400 nm) light using ultrafast transient absorption. The crucial role of surface termination in the emission process is evidenced by comparing hydrogenated, hydroxylated and carboxylated nanodiamonds. In particular, a transient response that we attribute to solvated electrons is observed on hydrogenated nanodiamonds upon visible light excitation, while it shows a sub-ps recombination due to trap states when excited with deep ultraviolet light. The essential role of surface reconstructions on the nanodiamonds in these processes is proposed based on density functional theory calculations. These results open new perspectives for solar-driven emission of solvated electrons in an aqueous phase using nanodiamonds.

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.

Ultrasmall Nanodiamonds: Perspectives and Questions.

Nanodiamonds are at the heart of a plethora of emerging applications in areas ranging from nanocomposites and tribology to nanomedicine and quantum sensing. The development of alternative synthesis methods, a better understanding, and the availability of ultrasmall nanodiamonds of less than 3 nm size with a precisely engineered composition, including the particle surface and atomic defects in the diamond crystal lattice, would mark a leap forward for many existing and future applications. Yet today, we are unable to accurately control nanodiamond composition at the atomic scale, nor can we reliably create and isolate particles in this size range. In this perspective, we discuss recent advances, challenges, and opportunities in the synthesis, characterization, and application of ultrasmall nanodiamonds. We particularly focus on the advantages of bottom-up synthesis of these particles and critically assess the physicochemical properties of ultrasmall nanodiamonds, which significantly differ from those of larger particles and bulk diamond.

The influence of differently functionalized nanodiamonds on proliferation, apoptosis and EMT/MET phenomena in 2D and 3D tumor cell cultures.

Nanodiamonds (ND) have been suggested to have several potential uses in biomedicine, since they are seemingly biocompatible. However, data about the biological effects of ND in physiological conditions are scarce. In this study, we observed that prostate cancer cells (LNCaP) and breast cancer cells (MDA-MB-231 and MCF-7) cultured with ND show morphological changes and altered gene and protein expression. In 2D we could detect only slight effects of ND on cell growth and apoptosis induction. Therefore, we applied different functionalized ND in a novel 3D cell culture model that reflects better tissue conditions compared to conventional 2D cell cultures. In 3D proliferation was reduced by all nanoparticles and benzoquinone functionalized ND induced cell death. As the used decellularized scaffold maintains the tissue architecture, we could also functionally investigate if nanoparticles induce cell migration into deeper layers and if they display markers of Mesenchymal Epithelial Transition (MET). We detected in more mesenchymal and invasive growing MDA-MB-231 cells less vimentin and increased levels of pan-cytokeratin expression after ND treatment, which indicates a MET induction. Our observations suggest that the presence of ND stimulates MET, with varying degrees of transition. The observation that ND do not support the opposite, EMT, is beneficial, since EMT is known to play a major role in tumor metastasis. However, a special focus should be placed on the characterization of biological effects to be able to guarantee the safety of ND in clinical use.

Threshold Photoelectron Spectrum of Cyclobutadiene: Comparison with Time-Dependent Wavepacket Simulations.

The C4H4 isomer cyclobutadiene (CBD) is the prime model for antiaromaticity and thus a molecule of considerable interest in chemistry. Because it is highly reactive, it can only be studied under isolated conditions. Its electronic structure is characterized by a pseudo-Jahn-Teller effect in the neutral and a E ⊗ ß Jahn-Teller effect in the cation. As a result, recording photoelectron spectra as well as describing them theoretically has been challenging. Here we present the photoion mass-selected threshold photoelectron spectrum of cyclobutadiene together with a simulation based on time-dependent wavepacket dynamics that includes vibronic coupling in the ion, taking into account eight vibrational modes in the cation. Excellent agreement between theory and experiment is found, and the ionization energy is revised to 8.06 ± 0.02 eV.

Pyrene-Based "Turn-Off" Probe with Broad Detection Range for Cu2+ , Pb2+ and Hg2+ Ions.

Detection of metals in different environments with high selectivity and specificity is one of the prerequisites of the fight against environmental pollution with these elements. Pyrenes are well suited for the fluorescence sensing in different media. The applied sensing principle typically relies on the formation of intra- and intermolecular excimers, which is however limiting the sensitivity range due to masking of e. g. quenching effects by the excimer emission. Herein we report a highly selective, structurally rigid chemical sensor based on the monomer fluorescence of pyrene moieties bearing triazole groups. This sensor can quantitatively detect Cu2+ , Pb2+ and Hg2+ in organic solvents over a broad concentrations range, even in the presence of ubiquitous ions such as Na+ , K+ , Ca2+ and Mg2+ . The strongly emissive sensor's fluorescence with a long lifetime of 165 ns is quenched by a 1 : 1 complex formation upon addition of metal ions in acetonitrile. Upon addition of a tenfold excess of the metal ion to the sensor, agglomerates with a diameter of about 3 nm are formed. Due to complex interactions in the system, conventional linear correlations are not observed for all concentrations. Therefore, a critical comparison between the conventional Job plot interpretation, the method of Benesi-Hildebrand, and a non-linear fit is presented. The reported system enables the specific and robust sensing of medically and environmentally relevant ions in the health-relevant nM range and could be used e. g. for the monitoring of the respective ions in waste streams.

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.

Efficient surface functionalization of detonation nanodiamond using ozone under ambient conditions.

Oxidative treatment is an important method for the purification and functionalization of carbon nanomaterials. Here we report on the treatment of detonation diamond particles with ozone at low temperatures. The homogeneous reaction in colloidal dispersion opens up a novel path for the efficient and homogeneous functionalization of the surface of nanodiamond with ozonides. As these are stable under the chosen ozonolysis conditions, they can be transformed to a number of different surface groups in subsequent oxidative or reductive workup steps. This versatile method for the preparation of oxygen-terminated diamond nanoparticles provides excellent control over the composition of the surface moieties in a waste-free and easy to set up way.

Pentadiynylidene and Its Methyl-Substituted Derivates: Threshold Photoelectron Spectroscopy of R1-C5-R2 Triplet Carbon Chains.

Mass-selective threshold photoelectron spectroscopy in the gas phase was employed to characterize the dialkynyl triplet carbenes pentadiynylidene (HC5H), methylpentadiynylidene (MeC5H), and dimethylpentadiynylidene (MeC5Me). Diazo compounds were employed as precursors to generate the carbenes by flash pyrolysis. The R1-C5-R2 carbon chains were photoionized by vacuum ultraviolet (VUV) synchrotron radiation in photoelectron photoion coincidence (PEPICO) experiments. High-level ab initio computations were carried out to support the interpretation of the experiments. For the unsubstituted pentadiynylidene (R1 = R2 = H) the recorded spectrum yields an adiabatic ionization energy (IEad) of 8.36 ± 0.03 eV. In addition, a second carbene isomer, 3-(didehydrovinylidene)cyclopropene, with a singlet electronic ground state, was identified in the spectrum based on the IEad of 8.60 ± 0.03 eV and Franck-Condon simulations. We found that multireference computations are required to reliably calculate the IEad for this molecule. CASPT2 computations predicted an IEad = 8.55 eV, while coupled-cluster computations significantly overestimate the IE. The cyclic isomer is most likely formed from another isomer of the precursor present in the sample. Stepwise methyl-substitution of the carbene leads to a reduction of the IE to 7.77 ± 0.04 eV for methylpentadiynylidene and 7.27 ± 0.06 eV for dimethylpentadiynylidene. The photoionization and dissociative photoionization of the precursors is investigated as well.

In vitro cytotoxicity assessment of nanodiamond particles and their osteogenic potential.

Scaffolds functionalized with nanodiamond particles (nDP) hold great promise with regard to bone tissue formation in animal models. Degradation of the scaffolds over time may leave nDP within the tissues, raising concerns about possible long-term unwanted effects. Human SaOS-2 osteoblast-like cells and U937 monoblastoid cells were exposed to five different concentrations (0.002-2 mg/L) of nDP (size range: 2.36-4.42 nm) for 24 h. Cell viability was assessed by impedance-based methods. The differential expression of stress and toxicity-related genes was evaluated by polymerase chain reaction (PCR) super-array, while the expression of selected inflammatory and cell death markers was determined by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). Furthermore, the expression of osteogenic genes by SaOS-2 cells, alkaline phosphatase activity and the extracellular calcium nodule deposition in response to nDP were determined in vitro. Cells responded differently to higher nDP concentrations (≥0.02 mg/L), that is, no loss of viability for SaOS-2 cells and significantly reduced viability for U937 cells. Gene expression showed significant upregulation of several cell death and inflammatory markers, among other toxicity reporter genes, indicating inflammatory and cytotoxic responses in U937 cells. Nanodiamond particles improved the osteogenicity of osteoblast-like cells with no evident cytotoxicity. However, concentration-dependent cytotoxic and inflammatory responses were seen in the U937 cells, negatively affecting osteogenicity in co-cultures. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1697-1707, 2018.

A Copolymer Scaffold Functionalized with Nanodiamond Particles Enhances Osteogenic Metabolic Activity and Bone Regeneration.

Functionalizing polymer scaffolds with nanodiamond particles (nDPs) has pronounced effect on the surface properties, such as improved wettability, an increased active area and binding sites for cellular attachment and adhesion, and increased ability to immobilize biomolecules by physical adsorption. This study aims to evaluate the effect of poly(l-lactide-co-ε-caprolactone) (poly(LLA-co-CL)) scaffolds, functionalized with nDPs, on bone regeneration in a rat calvarial critical size defect. Poly(LLA-co-CL) scaffolds functionalized with nDPs are also compared with pristine scaffolds with reference to albumin adsorption and seeding efficiency of bone marrow stromal cells (BMSCs). Compared with pristine scaffolds, the experimental scaffolds exhibit a reduction in albumin adsorption and a significant increase in the seeding efficiency of BMSCs (p = 0.027). In the calvarial defects implanted with BMSC-seeded poly(LLA-co-CL)/nDPs scaffolds, live imaging at 12 weeks discloses a significant increase in osteogenic metabolic activity (p = 0.016). Microcomputed tomography, confirmed by histological data, reveals a substantial increase in bone volume (p = 0.021). The results show that compared with conventional poly(LLA-co-CL) scaffolds those functionalized with nDPs promote osteogenic metabolic activity and mineralization capacity. It is concluded that poly(LLA-co-CL) composite matrices functionalized with nDPs enhance osteoconductivity and therefore warrant further study as potential scaffolding material for bone tissue engineering.

Functionalization of bone implants with nanodiamond particles and angiopoietin-1 to improve vascularization and bone regeneration.

One of the major challenges in bone tissue engineering is adequate vascularization within bone substituents for nutrients and oxygen supply. In this study, the production and results of a new, highly functional bone construct consisting of a commercial three-dimensional ß-tricalcium phosphate scaffold (ß-TCP, ChronOS®) and hydrophilic, functionalized nanodiamond (ND) particles are reported. A 30-fold increase in the active surface area of the ChronOS + ND scaffold was achieved after modification with ND. In addition, immobilization of angiopoietin-1 (Ang-1) via physisorption within the ß-TCP + ND scaffold retained the bioactivity of the growth factor. Homogeneous distribution of the ND and Ang-1 within the core of the three-dimensional scaffold was confirmed using ND covalently labelled with Oregon Green. The biological responses of the ß-TCP + ND scaffold with and without Ang-1 were studied in a sheep calvaria critical size defect model showing that the ß-TCP + ND scaffold improved the blood vessel ingrowth and the ß-TCP + ND + ND + Ang-1 scaffold further promoted vascularization and new bone formation. The results demonstrate that the modification of scaffolds with tailored diamond nanoparticles is a valuable method for improving the characteristics of bone implants and enables new approaches in bone tissue engineering.

Synthesis and fluxional behaviour of novel chloroborole dimers.

The (B-Cl)-chloroboroles 2-chloro-1,3-di(4-R-phenyl)-2,4,5,6-tetra-hydrocyclopenta[c]borole (R = H, Br) undergo a novel dimerisation process in CH2Cl2 solution. The resulting unsymmetric dimers are highly fluxional in solution via reversible enantiomerisation through an intermediate with mirror symmetry. DFT calculations suggest an unusual dimerisation mechanism and provide insight into the dynamics of the dimers.

Nanodiamond modified copolymer scaffolds affects tumour progression of early neoplastic oral keratinocytes.

This study aimed to evaluate the tumorigenic potential of functionalising poly(LLA-co-CL) scaffolds. The copolymer scaffolds were functionalised with nanodiamonds (nDP) or with nDP and physisorbed BMP-2 (nDP-PHY) to enhance osteoinductivity. Culturing early neoplastic dysplastic keratinocytes (DOK(Luc)) on nDP modified scaffolds reduced significantly their subsequent sphere formation ability and decreased significantly the cells' proliferation in the supra-basal layers of in vitro 3D oral neoplastic mucosa (3D-OT) when compared to DOK(Luc) previously cultured on nDP-PHY scaffolds. Using an in vivo non-invasive environmentally-induced oral carcinogenesis model, nDP scaffolds were observed to reduce bioluminescence intensity of tumours formed by DOK(Luc) + carcinoma associated fibroblasts (CAF). nDP modification was also found to promote differentiation of DOK(Luc) both in vitro in 3D-OT and in vivo in xenografts formed by DOK(Luc) alone. The nDP-PHY scaffold had the highest number of invasive tumours formed by DOK(Luc) + CAF outside the scaffold area compared to the nDP and control scaffolds. In conclusion, in vitro and in vivo results presented here demonstrate that nDP modified copolymer scaffolds are able to decrease the tumorigenic potential of DOK(Luc), while confirming concerns for the therapeutic use of BMP-2 for reconstruction of bone defects in oral cancer patients due to its tumour promoting capabilities.

On the absolute photoionization cross section and dissociative photoionization of cyclopropenylidene.

We report the determination of the absolute photoionization cross section of cyclopropenylidene, c-C3H2, and the heat of formation of the C3H radical and ion derived by the dissociative ionization of the carbene. Vacuum ultraviolet (VUV) synchrotron radiation as provided by the Swiss Light Source and imaging photoelectron photoion coincidence (iPEPICO) were employed. Cyclopropenylidene was generated by pyrolysis of a quadricyclane precursor in a 1 : 1 ratio with benzene, which enabled us to derive the carbene's near threshold absolute photoionization cross section from the photoionization yield of the two pyrolysis products and the known cross section of benzene. The cross section at 9.5 eV, for example, was determined to be 4.5 ± 1.4 Mb. Upon dissociative ionization the carbene decomposes by hydrogen atom loss to the linear isomer of C3H(+). The appearance energy for this process was determined to be AE(0K)(c-C3H2; l-C3H(+)) = 13.67 ± 0.10 eV. The heat of formation of neutral and cationic C3H was derived from this value via a thermochemical cycle as Δ(f)H(0K)(C3H) = 725 ± 25 kJ mol(-1) and Δ(f)H(0K)(C3H(+)) = 1604 ± 19 kJ mol(-1), using a previously reported ionization energy of C3H.

In Vivo Host Response and Degradation of Copolymer Scaffolds Functionalized with Nanodiamonds and Bone Morphogenetic Protein 2.

The aim is to evaluate the effect of modifying poly[(l-lactide)-co-(ε-caprolactone)] scaffolds (PLCL) with nanodiamonds (nDP) or with nDP+physisorbed BMP-2 (nDP+BMP-2) on in vivo host tissue response and degradation. The scaffolds are implanted subcutaneously in Balb/c mice and retrieved after 1, 8, and 27 weeks. Molecular weight analysis shows that modified scaffolds degrade faster than the unmodified. Gene analysis at week 1 shows highest expression of proinflammatory markers around nDP scaffolds; although the presence of inflammatory cells and foreign body giant cells is more prominent around the PLCL. Tissue regeneration markers are highly expressed in the nDP+BMP-2 scaffolds at week 8. A fibrous capsule is detectable by week 8, thinnest around nDP scaffolds and at week 27 thickest around PLCL scaffolds. mRNA levels of ALP, COL1α2, and ANGPT1 are significantly upregulating in the nDP+BMP-2 scaffolds at week 1 with ectopic bone seen at week 8. Even when almost 90% of the scaffold is degraded at week 27, nDP are observable at implantation areas without adverse effects. In conclusion, modifying PLCL scaffolds with nDP does not aggravate the host response and physisorbed BMP-2 delivery attenuates inflammation while lowering the dose of BMP-2 to a relatively safe and economical level.

Biofunctionalization of scaffold material with nano-scaled diamond particles physisorbed with angiogenic factors enhances vessel growth after implantation.

Biofunctionalized scaffold facilitates complete healing of large defects. Biological constraints are induction and ingrowth of vessels. Angiogenic growth factors such as vascular endothelial growth factor or angiopoietin-1 can be bound to nano-scaled diamond particles. Corresponding bioactivities need to be examined after biofunctionalization. We therefore determined the physisorptive capacity of distinctly manufactured, differently sized nDP and the corresponding activities of bound factors. The properties of biofunctionalized nDPs were investigated on cultivated human mesenchymal stem cells and on the developing chicken embryo chorio-allantoic membrane. Eventually porous bone substitution material was coated with nDP to generate an interface that allows biofactor physisorption. Angiopoietin-1 was applied shortly before scaffold implantation into an osseous defect in sheep calvaria. Biofunctionalized scaffolds exhibited significantly increased rates of angiogenesis already one month after implantation. Conclusively, nDP can be used to ease functionalization of synthetic biomaterials. FROM THE CLINICAL EDITOR: With the advances in nanotechnology, many nano-sized materials have been used in the biomedical field. This is also true for nano-diamond particles (nDP). In this article, the authors investigated the physical properties of functionalized nano-diamond particles in both in-vitro and in-vivo settings. The positive findings would help improve understanding of these nanomaterials in regenerative medicine.