Hongjian Zhou

Nanoscale hydroxyapatite particles for bone tissue engineering

Hydroxyapatite (HAp) exhibits excellent biocompatibility with soft tissues such as skin, muscle and gums, making it an ideal candidate for orthopedic and dental implants or components of implants. Synthetic HAp has been widely used in repair of hard tissues, and common uses include bone repair, bone augmentation, as well as coating of implants or acting as fillers in bone or teeth. However, the low mechanical strength of normal HAp ceramics generally restricts its use to low load-bearing applications. Recent advancements in nanoscience and nanotechnology have reignited investigation of nanoscale HAp formation in order to clearly define the small-scale properties of HAp. It has been suggested that nano-HAp may be an ideal biomaterial due to its good biocompatibility and bone integration ability. HAp biomedical material development has benefited significantly from advancements in nanotechnology. This feature article looks afresh at nano-HAp particles, highlighting the importance of size, crystal morphology control, and composites with other inorganic particles for biomedical material development.

Various preparation methods of highly porous hydroxyapatite/polymer nanoscale biocomposites for bone regeneration.

Tissue engineering utilizes expertise in the fields of materials science, biology, chemistry, transplantation medicine, and engineering to design materials that can temporarily serve in a structural and/or functional capacity during regeneration of a defect. Hydroxyapatite (HAp) scaffolds are among the most extensively studied materials for this application. However, HAp has been reported to be too weak to treat such defects and, therefore, has been limited to non-load-bearing applications. To capitalize the advantages of HAp and at the same time overcome the drawbacks nanocrystalline HAp (nHAp) is combined with various types of bioactive polymers to generate highly porous biocomposite materials that are used for osteoconduction in the field of orthopedic surgery. In this study we have reviewed nanosized HAp-based highly porous composite materials used for bone tissue engineering, introduced various fabrication methods to prepare nHAp/polymer composite scaffolds, and characterized these scaffolds on the basis of their biodegradability and biocompatibility through in vitro and in vivo tests. Finally, we provide a summary and our own perspectives on this active area of research.

Green synthesis of phytochemical-stabilized Au nanoparticles under ambient conditions and their biocompatibility and antioxidative activity

Green chemical synthesis of Au nanoparticles (NPs) has been of great interest because of its potential biomedical applications. In this study, we successfully produced phytochemical-induced Au NPs cofunctionalized with gallic acid, protocatechuic acid, and isoflavone. They have a strong antioxidant effect and serve as effective reducing agents, inducing the immediate passivation of Au NPs. The properties of these green chemical Au NPs were characterized by TEM, UV/Vis and FT-IR spectroscopy, and ζ-potential measurements, and the Au NPs exhibited excellent homogeneity with an average diameter of 20 nm and high dispersity at all pH ranges, with long-term stability as well as excellent cytocompatibility. Molecular dynamics (MD) simulations were also carried out in order to reveal the surface stability of the Au NPs. The computational results indicate that there are strong interactions between the phytochemicals and Au NPs, especially in the Au/protocatechuic acid–isoflavone model. Phytochemical-stabilized Au NPs allowed about 40% H2O2 to be removed at an NP concentration of 50 μg mL−1; this removal rate is the same as that achieved by 3000 units per mg catalase. Therefore, this novel synthesis route for Au NPs using phytochemical reducing agents may be effectively exploited for nonthermal-assisted reactions and one-pot processes of biological applications.

Dual-Mode SERS-Fluorescence Immunoassay Using Graphene Quantum Dot Labeling on One-Dimensional Aligned Magnetoplasmonic Nanoparticles.

A novel dual-mode immunoassay based on surface-enhanced Raman scattering (SERS) and fluorescence was designed using graphene quantum dot (GQD) labels to detect a tuberculosis (TB) antigen, CFP-10, via a newly developed sensing platform of linearly aligned magnetoplasmonic (MagPlas) nanoparticles (NPs). The GQDs were excellent bilabeling materials for simultaneous Raman scattering and photoluminescence (PL). The one-dimensional (1D) alignment of MagPlas NPs simplified the immunoassay process and enabled fast, enhanced signal transduction. With a sandwich-type immunoassay using dual-mode nanoprobes, both SERS signals and fluorescence images were recognized in a highly sensitive and selective manner with a detection limit of 0.0511 pg mL(-1).

Plasmon-induced photoluminescence immunoassay for tuberculosis monitoring using gold-nanoparticle-decorated graphene.

Metal-nanoparticle-functionalized graphene, in particular, graphene sheets containing Au nanoparticles (Au NPs), have generated considerable interest because of their unique optical and electrical characteristics. In this study, we successfully produced graphene sheets decorated with Au NPs (AuGrp) using phytochemicals as reducing agents. During this reaction, Au ions intercalated into the layered graphene flakes and were then reduced into NPs, exfoliating the graphene sheets. The physicochemical properties of the AuGrp nanocomposites were characterized, and the exfoliation process was investigated using a molecular dynamics simulation of Au NPs between graphene sheets. Our proposed technique is advantageous because the phytochemicals are mild reducing agents that preserve the graphene structure during exfoliation and NP decoration. The dispersity of the NPs on the graphene sheets was drastically improved due to the use of metal-ion intercalation. Moreover, the electrical conductivity was 6-30 times higher than that of bare graphene and reduced graphene oxide. Using antibody (Ab) modified AuGrp sheets and quantum dots, a plasmonic-induced photoluminescence immunoassay of tuberculosis (TB) antigen (aG) CFP-10 was demonstrated for a potential application of these materials. The enhancement of photoluminescence (PL) response was monitored depending on the various TB aG concentrations from 5.1 pg/mL to 51 μg/mL, and the detection limit for CFP-10 was 4.5 pg/mL. Furthermore, the selectivity was demonstrated with Ag85 as the other TB aG, and PL enhancement was not observed in this case. Therefore, AuGrp-based immunoassay showed the potential for biosensor application.

Small molecule induced self-assembly of Au nanoparticles

Interest in one dimensional assemblies of metallic nanomaterials, particularly Au nanoparticles (NPs), has grown due to the optical properties and various applications of NPs in optoelectronics, biosensors, and nano-electronics. In general, one-dimensional alignments of Au nanostructures have been accomplished by using soft or hard templates, such as polymers, DNA, anodized aluminum oxide or even molecular templates. However, difficulties of nanoscale control and remnant byproducts through unwanted chemical reactions have become a limitation. In this paper, a no-template assembly was successfully carried out to produce one dimensional nanochains of Au NPs through N-ethyl-N′-(dimethylaminopropyl) carbodiimide (EDC) chemistry, where carboxylates on the surface of Au NPs are activated by EDC at room temperature. EDC is a fascinating candidate for nanomaterials assembly due to its easily chemical-activating ability as well as well-known biocompatibility. Physiochemical properties of the nanochains were characterized by TEM, AFM, UV/Vis, and FT-IR spectrophotometers, as well as zeta potential. Molecular dynamics (MD) simulations were also carried out in order to reveal the structuring mechanisms of the chains. Experimental and computational results indicate that the strong interaction between citrate-EDC-citrate and Au NPs was related to van der Waals forces and the Coulomb force of the functional groups, inducing delicate manipulation of the main bonding energy for self-assembly those NPs.

Magnetic-Assembly Mechanism of Superparamagneto-Plasmonic Nanoparticles on a Charged Surface

One-dimensional magnetoplasmonic nanochains (MPNCs) were self-assembled using Au-coated Fe3O4 core-shell superparamagnetic nanoparticles (Fe3O4@Au NPs) by applying an external static magnetic field. The assembly mechanism of the Fe3O4@Au NPs was investigated thoroughly, revealing that substrate-particle interactions, van der Waals forces, and magnetic forces play important roles in the formation and control of the MPNCs. Magnetic force microscopy (MFM) and vibrating sample magnetometry (VSM) were used to study the magnetic properties of the MPNCs, which were compared with those of Fe3O4 nanochains.

Three-dimensional honeycomb-like structured zero-valent iron/chitosan composite foams for effective removal of inorganic arsenic in water

A facile freeze-drying method was presented to fabricate three dimensional (3D) honeycomb-like structured nanoscale zero-valent iron/chitosan composite foams (ICCFs) for effective removal of inorganic arsenic in water. It was found that freezing temperature has important influence on the formation of 3D network structure of ICCFs. The ICCFs obtained at freeze temperature of -80°C exhibits oriented porous structure with good mechanical property than that at -20°C, thus improved excellent removal capability of As(III) and As(V) up to 114.9mgg(-1) and 86.87mgg(-1), respectively. Further, the adsorption kinetics of ICCFs on As(III) and As(V) can be described by pseudo-second order model and their adsorption isotherms follow Langmuir adsorption model. The superior removal performance of ICCFs on As(III) and As(V) can be ascribed to its oriented porous structure with abundant adsorption active sites resulted from nZVI and O, N-containing functional groups in ICCFs. Importantly, it was found that the O, N-containing functional groups of chitosan in ICCFs can adequately bind with the dissolved Fe(3+) ions from oxidation of nZVI to form Fe(3+)-Chitosan complex during removal of As(III) and As(V), thus effectively avoiding the dissolved Fe(3+) ions into solution to produce secondary pollution. A possible adsorption-coupled reduction mechanism of ICCFs on As(III) and As(V) was also proposed based on the experimental results. We believe that this work would be helpful to develop low-cost and abundant chitosan-based materials as high performance adsorbents for environmental remediation applications.

Magnetically recyclable catalytic activity of spiky magneto-plasmonic nanoparticles

Spiky magnetoplasmonic nanoparticles (NPs) with an Fe3O4 core and epitaxial Au branches have been successfully fabricated for the magnetically recyclable catalysis of the 4-nitrophenol reduction. The epitaxial Au branches in the spiky magnetoplasmonic NPs lead to enhanced catalytic activity. Because of high magnetization, the spiky NPs exhibit good separation ability and reusability, which can be repeatedly applied for the nearly complete reduction of 4-nitrophenol for at least four successive cycles. The unique properties make spiky magnetoplasmonic NPs an ideal platform to study various heterogeneous catalytic processes that can be potentially applied in a wide variety of fields in bio-separation, catalysis, and sensing devices.

Europium-based infinite coordination polymer nanospheres as an effective fluorescence probe for phosphate sensing

Although phosphate plays important roles in aquatic ecosystems as an indispensible nutrient, excessive levels are responsible for severe environmental issues. Hence, it is of considerable significance to develop highly sensitive and reliable probes for the detection of phosphate with the purpose of monitoring of water quality security and early-warning of eutrophication occurrence. In this work, uniform europium-based infinite coordination polymer (Eu-ICP) nanospheres are rationally constructed by a facile one-step solvothermal treatment. It is demonstrated that the newly developed sensing platform features excellent fluorescence properties, which can be efficiently quenched by the presence of phosphate ions (Pi). Typically, a good linearity exists between the decrease in fluorescence intensities and the Pi analyte content ranging from 2–100 μM, allowing the reliable determination of Pi concentration. Accordingly, the detection limit is estimated to be 0.83 μM, which is far below the detection requirement of phosphate discharge criteria in the water environment. It is noteworthy that the prepared Eu-ICP probe displays a specific recognition towards Pi, and is hardly affected by other possible existing species in natural water. More importantly, the proposed fluorescent probe can be utilized for reliable determination of Pi concentration in real water with acceptable recoveries, highlighting its feasibility in complicated environmental samples. Further research suggests that the underlying sensing mechanism is based on the strong affinity between europium centers and Pi, resulting in the collapse of the inherent structure of Eu-ICP and the corresponding fluorescence quenching. These findings show that the developed Eu-ICP probe holds great prospect in monitoring water quality and early warning of eutrophication based on the unique features associated with this simple preparation procedure, high selectivity, and excellent sensitivity.