Surface Modification Of Nanodiamond Research Articles

Surface modification of nanodiamond with pH/thermo dual responsive polymer and hyper-branched dendrimer as a near-infrared photothermal-triggered drug delivery for cancer therapy

In this study, a pH/temperature-responsive drug delivery system based on nanodiamonds is successfully developed by grafting nanodiamonds with thermosensitive polymer and then coating with a hyper-branched dendrimer for docetaxel delivery. For this purpose, alyl alchol and poly (N-isopropylacrylamide) was grafted on the surface of nanodiamonds as functional monomer and thermo-sensitive polymer, respectively. Then, three generations of dendrimers were anchored to the grafted polymer chains by using 1, 3-phenylenediamine and methyl acrylate. Chemical bonding, phase analysis, morphology, and thermal behavior were studied by Fourier transform infrared, x-ray diffraction, field emission scanning electron microscopy, and thermogravimetric techniques, respectively. Equilibrium isotherm and kinetic data were fitted well with Langmuir and pseudo-second-order models by giving a maximum capacity of adsorption. The findings of in-vitro release studies shown that the prepared nanocarrier could be employed for docetaxel delivery due to the pH and temperature-dependent sustained release (99.78% after 6 h, at pH = 5.6, T = 45 °C). Using the near-infrared laser irradiation, the docetaxel release reached 90.97% in 20 min, which was about 4.5 folds faster than without laser irradiation. The drug release from nanocarrier was modeled and the Higuchi model was introduced as the best model predicting the release behavior.

Precisely controlled polydopamine-mediated antibacterial system: mathematical model of polymerization, prediction of antibacterial capacity, and promotion of wound healing

In this work, the polydopamine (PDA)-mediated antibacterial system is synthesized for in vitro and in vivo antimicrobial activities. To precisely control the surface modification of nanodiamonds (NDs), a mathematical kinetics model of PDA deposition is established, and the conditions of synthesis reaction are discussed including the concentrations of dopamine, the reaction time, and the kinetic constant k 1, which is a function of several variables associated with the reaction temperature, light irradiance, pH value and concentration of dissolved O2 in the solution. A simulation reveals that the deposition of PDA is positively correlated with these factors and will be terminated if dissolved O2 levels are inadequate. Then, the precisely controlled thickness of PDA layers can regulate the formation of AgNPs, resulting in a rise in the intensity of Raman peaks and a predicted antibacterial activity against E. coli in vitro. An optimized antibacterial hydrogel incorporating NDs-PDA/Ag is prepared and characterized by the Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Finally, the antibacterial tests are performed to promote in vivo wound healing, as confirmed by pathological and immunohistochemical-stained tissue sections. This work provides a theoretical foundation for predicting the PDA-assisted surface modification of NDs, resulting in a divinable antibacterial effect and promoting in vivo wound healing.

Surface PEGylation of nanodiamond through a facile Michael addition reaction for intracellular drug delivery

Nanodiamond (ND) has been regarded as one of the most fascinating carbon nanomaterials for biomedical applications owing to its excellent physicochemical and biological properties. The biomedical application of ND-based materials mainly depends on its surface chemistry and properties, so the surface modification of ND is very important to improve its final biomedical application performance. In this work, a novel route for the surface modification of ND was developed via the combination of esterification reaction and Michael addition reaction. Simply, the pristine ND was first functionalized with ethylene diamine to immobilize the amino groups on the surface of ND. Then, a hydrophilic and biocompatible poly (ethylene glycol) methyl ether methacrylate (PEGMA) was further conjugated onto ND surface through Michael addition reaction to obtain PEGylated ND (ND@PEGMA) composites, which were ascertained by a series of characterization techniques. The dispersibility and potential biomedical applications of ND@PEGMA were examined and results demonstrated that ND@PEGMA displayed enhanced dispersibility and low cytotoxicity. Finally, doxorubicin hydrochloride as an anticancer drug model was successfully loaded on the prepared ND based composites, and the drug release and intracellular delivery of the drug-loaded composites (ND@PEGMA-DOX) were further studied and the results indicate that ND@PEGMA composites could be utilized as promising candidates for intracellular drug delivery.

Preparation of ionic liquids functionalized nanodiamonds-based composites through the Michael addition reaction for efficient removal of environmental pollutants

Nanodiamonds (ND) is a novel type of carbon nanomaterials with small size, large specific surface areas, low cost and some other physicochemical properties. However, the environmental applications of ND are still rarely reported because of its low adsorption performance. In this work, we reported for the first time for the surface modification of ND with ionic liquids through a facile and effective Michael addition reaction. To synthesis of the ternary ND@IL composites, ND was first linked with APTES by a silanization reaction and then [C16VIm+] [Br−] was conjugated on the surface of amino groups functionalized ND via the Michael addition reaction. The ND@IL composites were applied as adsorbents for removal of Congo red (CR) from aqueous solution and displayed high removal efficiency (92.78%) at room temperature and neutral solution. Under certain adsorption conditions, the adsorption capacities of pristine ND and ND@IL towards CR is 61.1 and 226.4 mg g−1, respectively. The pseudo-second-order model fitting the adsorption kinetic data is superior to pseudo-first-order model and Freundlich isotherm model describes the experimental data well. Further experiments showed that the removal process was pH dependence, exothermic and spontaneous. More importantly, ND@IL composites could be regenerated via adjustment of pH values and still maintain high adsorption capacity after five regeneration cycles. All of the above results demonstrated that these ionic liquids modified ND are promising adsorbents for highly efficient and quick removal of environmental pollutants from aqueous effluents.

Surface modification of nanodiamond: Toward the dispersion of reinforced phase in poly-l-lactic acid scaffolds

The agglomeration of nanodiamond severely reduces the reinforcement in matrix of composites although it is often used as a reinforcing phase. In this study, nanodiamond was modified by phospholipid to promote its dispersion in Poly-l-lactic acid (PLLA) scaffolds fabricated via selective laser sintering. Concretely, phospholipid was an amphiphilic substance with hydrophilic head and hydrophobic tails. The hydrophilic head could adsorb on nanodiamond surface through hydrogen bonding between the OH of head and the COOH of nanodiamond. The hydrophobic tails were forced arrange toward the PLLA matrix. As a result, nanodiamond particles were covered with a layer of phospholipid. They are compelled far away from each other due to the exclusion between the hydrophobic tails. This promoted the dispersion of nanodiamond in PLLA scaffolds. Consequently, the compressive strength, compressive modulus and Vickers hardness of the scaffolds modified by phospholipid increased by 162.8%, 163.2% and 88.2% compared with those of unmodified scaffolds, respectively. Meanwhile, the scaffolds could provide a suitable environment that enabled cells to adhere, grow and migrate, indicating good cytocompatibility. This study suggested the PLLA/nanodiamond scaffolds modified by phospholipid could be a potential candidate for bone tissue engineering applications.

Surface modification and disaggregation of detonation nanodiamond particles with biodegradable polyurethane

Nanodiamond(ND) is one of the most important carbon nanomaterials, which not only has the distinguishing feature of fundamental nanoparticles but also has intrinsic characteristics of diamond. Depending on its extraordinary properties, such as good biocompatibility, low toxicity and mechanical behavior, ND thus has been widely used in a variety of fields. However, pristine ND easily tends to aggregate in the form of micro-sized clusters. Therefore, two different approaches for surface modification of ND with biodegradable polyurethane by chemical of grafting-to and grafting-from are presented herein. The Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA) reveal that polyurethane has been covalently attached to ND surface, and the weight loss is 3.51% and 3.23%, which is equivalent to the grafted rate. Dynamic light scattering, transmission electron microscopic (TEM) and natural sedimentation experiment all demonstrate that modified ND with long PU chains can well disperse in organic solvents and CCD images (Charge Coupled Device Images) illustrate that modified ND render hydrophilic pristine ND good hydrophobic behavior. So ND functionalized with polyurethane broadens a new prospect of application in biomedical science. It is suggested that the polyurethane macromolecules covalently bonded onto the agglomerate surface play an important role on the colloidal stability against aggregation.

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles.

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 µg/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

Preparation of water dispersible and biocompatible nanodiamond-poly(amino acid) composites through the ring-opening polymerization

Nanodiamond (ND) is one of the most fascinating carbon materials that have been extensively investigated for biomedical applications owing to its small size, high specific surface areas, chemical inert and desirable biocompatibility. It has been reported that surface modification of ND with polymers could not only improve the dispersibility of final ND based composites but also endow them novel functions to fulfill the requirement for biomedical applications. Although some strategies have been developed previously, surface modification of ND with poly(amino acid)s has not been reported previously. In this work, poly(amino acid)s functionalized ND composites were fabricated through a ring-opening polymerization of α-amino acid N-carboxyanhydrides (NCAs), which was synthesized by conjugation of hydrophilic ethylene glycol with glutamic acid. The successful preparation of ND-GluEG composites was confirmed by a series of characterization techniques. The results suggest that the water dispersibility of final ND-GluEG composites is obviously improved. Moreover, ND-GluEG composites show low toxicity and are of great potential for biomedical applications.

Dopamine@Nanodiamond as novel reinforcing nanofillers for polyimide with enhanced thermal, mechanical and wear resistance performance.

In this study, to achieve a homogeneous dispersion of nanodiamond (ND) in a polyimide (PI) matrix and a strong interfacial adhesion between ND and the PI matrix, a biomimetic nondestructive dopamine chemistry was employed for surface modification of ND. FTIR and Raman spectroscopy studies revealed that self-polymerization of dopamine could produce thinner polydopamine (PDA) layers on the ND surface via spontaneous oxidation and the intermolecular cross-linking reaction of PDA molecules. The structure and morphology of PDA–ND were studied by FTIR, SEM, and Raman spectroscopy, which verified the π–π interactions between PDA and ND. The facile dispersion of PDA–ND in a polyamic acid prepolymer made it possible to obtain PI/ND composites with no obvious ND aggregation. The effect of PDA–ND nanoparticles on the thermal, mechanical and tribological properties of the resulting PI/PDA–ND composites were evaluated, and the results showed that the incorporation of PDA–ND could increase the hardness, tensile strength, storage modulus, as well as the wear resistance properties. PI/PDA–ND composites prepared in this study showed that PDA–ND is a promising nanoreinforcing filler for PI composites.

Facile modification of nanodiamonds with hyperbranched polymers based on supramolecular chemistry and their potential for drug delivery

Due to their excellent chemical stability and remarkable biocompatibility, nanodiamonds (NDs) have received widespread research attention by the biomedical field. The excellent water dispersibility of NDs has significant importance for biomedical applications. Therefore, surface modification of NDs with hydrophilic polymers has been extensively investigated over the past few decades. In this study, we synthesize β-CD containing hyperbranched polymer functionalized ND (ND-β-CD-HPG) composites with high water dispersibility via supramolecular chemistry based on the host-guest interactions between β-Cyclodextrin (β-CD) and adamantine (Ad). The hydroxyl groups of NDs first reacted with 1, 1-adamantanecarbonyl chloride to obtain ND-Ad, which was further functionalized with β-CD containing hyperbranched polymers to form the final ND-β-CD-HPG composites. The successful preparation of ND-β-CD-HPG composites was confirmed by several characterization techniques. Furthermore, the loading and release of the anticancer agent doxorubicin hydrochloride (DOX) on ND-β-CD-HPG composites was also examined to explore its potential in drug delivery. When compared with traditional methods of surface modification of NDs, this method was convenient, fast and efficient. We demonstrated that ND-β-CD-HPG composites have great water dispersibility, low toxicity, high drug-loading capacity and controlled drug-release behavior. Based on these characteristics, ND-β-CD-HPG composites are expected to have high potential for biomedical applications.

Comparison between photoemitting and colloidal properties of nanodiamond particles

In this paper, we present an investigation on two types of nanodiamond (ND) powders with average size of particles around 250nm and having different sp2 (graphite phase) and sp3 (diamond phase) carbon contents. The ND surface modification is carried out by physical methods i.e. treatments in H2 microwave plasma. The quantum efficiency (QE) of photocathodes and the stability of aqueous dispersions are assessed by photoemission and zeta potential (ZP) measurements, respectively.The resultant hydrogenated surface affects in the solid state the QE of ND-based photocathodes and in solution the particle ZP. The effect of the hydrogen treatment is beneficial inducing an enhancement of photocathode QE and a corresponding increase of the ZP. A schematized energy diagram is proposed to illustrate and explain the strong correlation between QE and ZP parameters.

The effect of nanodiamond surface modification on interaction with Pseudomonas putida K12

Interactions between nanodiamonds with an unmodified surface and nanodiamonds with chlorinated, as well as aminated, surfaces and the bacterium surfaces and Pseudomonas putida K12 were studied. It was revealed that only nanodiamonds with a modified surface possessed a considerable biocidal effect. Aminated nanodiamonds were twice as efficient as chlorinated ones. Electron microscopy showed that nanodiamonds were adsorbed onto the cell surface and damaged it. It is proposed that the higher biocidity of the aminated nanoparticles was caused by a positive charge inducing electrostatic interaction with the negatively charged surface of the bacterial cytoplasmic membrane.

Surface modification of nanodiamond through metal free atom transfer radical polymerization

Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by 1H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

Direct surface PEGylation of nanodiamond via RAFT polymerization

Nanodiamond (ND) is a novel class of carbon nanomaterials, which has been extensively investigated for biomedical applications because of its small size, high surface area and excellent biocompatibility. However, the biomedical applications of unmodified ND are still largely restricted because of their poor dispersibility in both aqueous and organic medium. In this work, we reported a novel strategy for the surface modification of ND via reversible addition fragmentation chain transfer (RAFT) polymerization. For preparation of the PEGylated ND (pPEGMA-ND), chain transfer agent (CTA) was immobilized onto ND through reaction between the hydroxyl group of ND and the carboxyl group of CTA, which was used as the initiator for surface-initiated RAFT polymerization. The successful preparation of pPEGMA-ND was characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectra and thermal gravimetric analysis in detail. Results demonstrated that pPEGMA-ND exhibited enhanced water dispersibility and desirable biocompatibility, making it promising for biomedical applications.

Nanodiamond Nanofluids for Enhanced Thermal Conductivity

Deaggregation of oxidized ultradispersed diamond (UDD) in dimethylsulfoxide followed by reaction with glycidol monomer, purification via aqueous dialysis, and dispersion in ethylene glycol (EG) base fluid affords nanodiamond (ND)-poly(glycidol) polymer brush:EG nanofluids exhibiting 12% thermal conductivity enhancement at a ND loading of 0.9 vol %. Deaggregation of UDD in the presence of oleic acid/octane followed by dispersion in light mineral oil and evaporative removal of octane gives ND·oleic acid:mineral oil dispersions exhibiting 11% thermal conductivity enhancement at a ND loading of 1.9 vol %. Average particle sizes of ND additives, determined by dynamic light scattering, are, respectively, ca. 11 nm (in H2O) and 18 nm (in toluene). Observed thermal conductivity enhancements outperform enhancement effects calculated using Maxwell's effective medium approximation by 2- to 4-fold. Covalent ND surface modification gives 2-fold greater thermal conductivity enhancement than ND surface modification via hydrogen-bonding interactions at similar concentrations. Stable, static ND:mineral oil dispersions are reported for the first time.

Surface Modification of Nanodiamond under Bingel–Hirsch Conditions

The Bingel-Hirsch reaction consists in the reaction of a bromomalonate with electron-poor π bonds, for example, of carbon materials, yielding cyclopropane derivatives. The reactive nucleophile is generated in situ from the respective malonate using CBr(4) and a base. The resulting cyclopropane moiety links the carbon material's surface atoms covalently with the functional side groups of the malonate. So far, the reaction was limited to fullerenes and carbon nanotubes. Herein, we report on the first application of this reaction type for the surface modification of diamond nanoparticles. The surface of thermally annealed nanodiamond consists of fullerene-like sp(2) carbon atoms which exhibit a similar reactivity as those in the all-sp(2) carbon nanomaterials. It was found that the reaction proceeds smoothly and enables the grafting of a large variety of functional groups to the surface of nanodiamond. The generated nucleophiles are also able to react with carbonyl species on the diamond. This reaction pathway enables the grafting of malonates even on oxidized nanodiamond without prior thermal annealing.

Functionality is Key: Recent Progress in the Surface Modification of Nanodiamond

AbstractNanoscale diamond has recently received considerable attention due to the various possible applications such as luminescence imaging, drug delivery, quantum engineering, surface coatings, seeding etc. For most of these fields a suitable surface termination and functionalization of the diamond materials are required. In this feature article we discuss recent achievements in the field of surface modification of nanoscale diamond including the establishment of a homogeneous initial surface termination, the covalent and non‐covalent immobilization of different functional moieties as well as the subsequent grafting of larger (bio)molecules onto previously functionalized nanodiamond.

Optical Detection of Charged Biomolecules: Towards Novel Drug Delivery Systems

This paper presents work done on developing optically-traceable intracellular nanodiamond sensors, where the photoluminescence can be changed by a biomolecular attachment/delivery event. Their high biocompatibility, small size and stable luminescence from their color centers make nanodiamond (ND) particles an attractive alternative to molecular dyes for drug-delivery and cell-imaging applications. In our work, we study how surface modification of ND can change the color of ND luminescence (PL). This method can be used as a novel detection tool for remote monitoring of chemical processes in biological systems. Recently, we showed that PL can be driven by atomic functionalization, leading to a change in the color of ND luminescence from red (oxidized ND) to orange (hydrogenated ND). In this work, we show how PL of ND changes similarly when interacting with positively and negatively charged molecules. The effect is demonstrated on fluorinated ND, where the high dipole moment of the C-F bond is favorable for the formation of non-covalent bonds with charged molecules. We model this effect using electrical potential changes at the diamond surface. The final aim of the work is to develop a “smart” optically traceable drug carrier, where the delivery event is optically detectable.

On the mechanism of charge transfer between neutral and negatively charged nitrogen-vacancy color centers in diamond

ABSTRACTThe presented work aims for the development of optically-traceable intracellular nanodiamond sensors, where photoluminescence can be changed by biomolecular attachment/delivery event. High biocompatibility, small size and stable luminescence from its color centers, makes nanodiamond (ND) particles an attractive alternative to molecular dyes for drug-delivery and cell-imaging applications. In our work we study how the surface modification of ND can change ND luminescence spectra. This method can be used as a novel detection tool for remote monitoring of chemical processes in biological systems. We discuss photoluminescence (PL) spectra of oxidized and hydrogenated ND and a single crystal diamond, containing engineered NV centers. The hydrogenation of ND leads to quenching of NV- related luminescence and a PL shift due to changing of occupation from NV- to NV0 states. We model this effect using electrical potential changes at the diamond surface.

Facile Surface Functionalization of Nanodiamonds

Nanodiamonds (NDs) have versatile applications in electro-optical devices, sensors, and biomedicine. Owing to the difficulty in activation of the inert sp(3) C-H bonds on the surface of NDs, it is not trivial to modify the surface functionalities on NDs. A few functionalization methods have been reported in the literature for surface modification of NDs. Many of them, however, are either multiple steps/time-consuming, or require the use of highly toxic/environmentally unfriendly reagents, such as fluorine gas and sulfuric acid. It is necessary to develop a simple process for surface functionalization of NDs to have both hydrophobic and hydrophilic functional groups. In this report, a facile process was developed to allow easy and rapid surface modification of NDs to become dispersible in either water or organic solvents using the same process. The process involves surface graphitization of NDs, followed by radical initiated surface grafting of oligomers with various functionalities, including -C(=O)OCH(3), -COOH, -NH(2), or aliphatic moieties.