Guohai Liang

A novel nonenzymatic sensor based on CuO nanoneedle/graphene/carbon nanofiber modified electrode for probing glucose in saliva

Here, we report on a novel nonenzymatic amperometric glucose sensor based on CuO nanoneedle/graphene/carbon nanofiber modified electrode. The results of the scanning electron microscopy indicate that electronic network was formed through their direct binding with the graphene/carbon nanofiber, which leads to larger active surface areas and faster electron transfer for the glucose sensor. High electrocatalytic activity toward the oxidation of glucose was observed with a rapid response (<2 s), a low detection limit (0.1 µM), a wide and useful linear range (1-5.3 mM) as well as good stability and repeatability. Moreover, the common interfering species, such as ascorbic acid, uric acid, dopamine and so forth did not cause obvious interference. The sensor can also be used for quantification of glucose concentration in real saliva samples. Therefore, this work has demonstrated a simple and effective sensing platform for nonenzymatic detection of glucose.

MRI‐Visualized, Dual‐Targeting, Combined Tumor Therapy Using Magnetic Graphene‐Based Mesoporous Silica

Targeting peptide-modified magnetic graphene-based mesoporous silica (MGMSPI) are synthesized, characterized, and developed as a multifunctional theranostic platform. This system exhibits many merits, such as biocompatibility, high near-infrared photothermal heating, facile magnetic separation, large T2 relaxation rates (r2), and a high doxorubicin (DOX) loading capacity. In vitro and in vivo results demonstrate that DOX-loaded MGMSPI (MGMSPID) can integrate magnetic resonance imaging, dual-targeting recognition (magnetic targeting and receptor-mediated active targeting), and chemo-photothermal therapy into a single system for a visualized-synergistic therapy of glioma. In addition, it is observed that the MGMSPID system has heat-stimulated, pH-responsive, sustained release properties. All of these characteristics would provide a robust multifunctional theranostic platform for visualized glioma therapy.

One-pot synthesis of Gd3+-functionalized gold nanoclusters for dual model (fluorescence/magnetic resonance) imaging

Multimodal imaging that aims to advance imaging by strategically combining existing technologies with uniquely designed probes has attracted great interest in recent years. Here, Gd3+-functionalized gold nanoclusters (Gd-AuNCs) were synthesized for dual model (fluorescence/magnetic resonance) imaging. We designed a cyclodecapeptide that contained one tyrosine and two cysteines for the synthesis, and it biomineralized gold nanoclusters and chelated Gd3+ ions at the same time. The Gd-AuNC probes emit an intense red fluorescence under UV light, while exhibiting a high longitudinal relaxivity of 41.5 ± 2.5 mM-1 s-1 and a low r2/r1 ratio of 1.2 at 0.55 T. The versatility of the probes for dual model imaging has been demonstrated by means of cellular imaging and in vivo T1-weighted MRI. Thanks to the optimal size of the nanocluster, it can freely circulate in the blood pool without significant accumulation in the liver and spleen, but with a long circulation half-life (t1/2) of ∼128 min. Moreover, the nanoclusters can be noticeably excreted from the body within a period of 24 h through renal clearance, making it attractive for in vivo multimodal imaging.

Ultrasmall gadolinium hydrated carbonate nanoparticle: an advanced T1 MRI contrast agent with large longitudinal relaxivity

Inorganic nanoparticle-based T1 contrast agents with high longitudinal relaxivity (r1) and low r2/r1 ratio have attracted great interest in recent years. However, the r1 relaxivity of inorganic nanoparticles reported to date is relatively low. In this work, 2.3 ± 0.1 nm paramagnetic gadolinium hydrated carbonate nanoparticles (GHC-1) with a high r1 relaxivity of 34.8 mM-1 s-1 and low r2/r1 ratio of 1.17 are synthesized using a one-pot hydrothermal process. The r1 of GHC-1 is 9.4 times higher than that of Gd-DTPA at 0.55 T. The synthetic procedure is simple, cost effective, and easy to scale up. The nanoparticles have a small core size, an amorphous phase, and are well-coated by poly(acrylic acid). Due to the hydrophilic polymer coating, the particles are highly dispersible and stable in aqueous solution. No significant cellular or in vivo toxicity are observed for the nanoparticles, which guarantees the in vivo application of this material. Finally, we apply the nanoparticles to in vivo magnetic resonance imaging and study the biodistribution in organs. This study reveals GHC-1 as a potential candidate for a T1 contrast agent with extraordinary ability to enhance MR images.

Facile synthesis of fluorescent Au@SiO2 nanocomposites for application in cellular imaging.

A novel fluorescent Au@SiO(2) nanocomposite, with average size of ca. 30 nm in the diameter, was prepared via a simple microemulsion method. Additionally, transmission electron microscopy (TEM), UV-Vis absorption spectra, Fourier transform infrared (FT-IR) spectra and fluorescence spectra were used to characterize this nanocomposite. This newly synthesized, silica-wrapped, gold nanocluster has the following advantages: good water solubility, exceptional biocompatibility, favorable surface properties and excellent fluorescence properties. Because of these advantages, a Au@SiO(2) nanocomposite is exceptionally suitable for biological applications. In this study, cellular imaging, as a form of biological application, has been fully investigated, and it was discovered, after covalent conjugation of folic acid (FA), that the nanocomposite effectively recognized over expressed folic acid receptors (FARs) on the HeLa cells surface. Therefore, this fluorescent Au@SiO(2) nanocomposite could be used as a new fluorescent probe for selective biological imaging.

An efficient strategy for unmodified nucleotide-mediated dispersion of magnetic nanoparticles, leading to a highly sensitive MRI-based mercury ion assay.

It is highly attractive to develop a detection system that is not only sensitive and selective but also simple, rapid, practical and cost-effective in operation. Here, we report an interesting observation that single-stranded oligonucleotide (ssDNA) can adsorb efficiently on carboxylic acid-functionalized magnetic nanoparticles (CAMNPs) and stabilize the nanoparticles against aggregation in weakly acidic solution. The adsorbing rate closely correlates with the pH of the solution, the temperature and the sequence length of ssDNA. On the basis of this observation, we have designed a highly sensitive, non-sandwich type magnetic relaxation-based detection system for quantitatively probing mercury ion. The assay is independent of the samples optical properties, requires no covalent modification of the ssDNA or the CAMNPs surfaces, and can be used for high-throughput analysis. By varying the concentration of CAMNPs, four orders of dynamic response range and a detection limit of 0.3 nM for Hg(2+) are achieved. Moreover, we developed a multi-sample assay to detect Hg(2+) in real environmental samples with high sensitivity, selectivity and efficiency.

A miniature chip for protein detection based on magnetic relaxation switches

A miniature multi-sample chip for protein detection with a bench-top magnetic resonance imager was created on the basis of magnetic relaxation switches. The chip was assessed with two protein systems. Both qualitative and quantitative results for the target proteins were obtained by image analysis and relaxation time measurement, respectively. The detection of prostate specific antigen, the serum marker of human prostate cancer, showed a linear concentration range of 17.3-43.2 ng mL(-1) and a detection limit of 13.7 ng mL(-1). As proof of concept, the analysis of 18 samples with a volume of 6.37 μL each was completed in 26 min by this chip. This technique may become an easy and efficient approach for rapid and high-throughput protein assay and protein-protein interaction screening.

Label-free, nucleotide-mediated dispersion of magnetic nanoparticles for “non-sandwich type” MRI-based quantification of enzyme

In the present work, we demonstrate that nucleotide can adsorb efficiently on the surface of carboxylic acid-functionalized nanoparticles and stabilize the particles against aggregation. In the present study we take magnetic nanoparticles (MNPs), manganese oxide nanoparticles (MnO), and upconversion nanophosphors (UCNPs) as models. The result shows that not only MNPs, but also other kinds of nanoparticles that have similar surface properties can be dispersed and stabilized by nucleotides. Interestingly, adenosine bearing different numbers of phosphate groups has distinct stabilizing effect. On the basis of this observation, we developed a magnetic relaxation-based enzyme assay for quantitative analysis of alkaline phosphatase. A detection limit of 0.002 U/μL for calf intestine alkaline phosphatase (CIAP) could be obtained, which is lower than the gold nanoparticle-based colorimetric method. In contrast to the conventional magnetic relaxation switches (MRSw), this assay was achieved without covalent modification and separation steps, sandwich type binding was not required as well, which would potentially expand the application of magnetic relaxation-based analysis.