Da-Peng Yang

Folic acid-conjugated silica-modified gold nanorods for X-ray/CT imaging-guided dual-mode radiation and photo-thermal therapy.

Multifunctional nanoprobes are designed to own various functions such as tumor targeting, imaging and selective therapy, which offer great promise for the future of cancer prevention, diagnosis, imaging and treatment. Herein, silica was applied to replace cetyltrimethylammonium bromide (CTAB) molecules on the surface of gold nanorods (GNRs) by the classic Stöber method, thus eliminating their cytotoxicity and improving their biocompatibility. Folic acid molecule was covalently anchored on the surface of GNRs with silane coupling agent. The resultant folic acid-conjugated silica-modified GNRs show highly selective targeting, enhanced radiation therapy (RT) and photo-thermal therapy (PTT) effects on MGC803 gastric cancer cells, and also exhibited strong X-ray attenuation for in vivo X-ray and computed tomography (CT) imaging. In conclusion, the as-prepared nanoprobe is a good candidate with excellent imaging and targeting ability for X-ray/CT imaging-guided targeting dual-mode enhanced RT and PTT.

Photosensitizer-conjugated magnetic nanoparticles for in vivo simultaneous magnetofluorescent imaging and targeting therapy.

A major challenge in nanotechnology and nanomedicine is to integrate tumor targeting, imaging, and selective therapy functions into a small single nanoparticle (<50 nm). Herein, photosensitizer-conjugated magnetic nanoparticles with ∼20 nm in diameter were strategically designed and prepared for gastric cancer imaging and therapy. The second generation photosensitizer chlorin e6 (Ce6) was covalently anchored on the surface of magnetic nanoparticles with silane coupling agent. We found that the covalently incorporated Ce6 molecules retained their spectroscopic and functional properties for near-infrared (NIR) fluorescence imaging and photodynamic therapy (PDT), and the core magnetic nanoparticles offered the functions of magnetically guided drug delivery and magnetic resonance imaging (MRI). The as-prepared single particle platform is suitable for simultaneous targeting PDT and in vivo dual-mode NIR fluorescence imaging and MRI of nude mice loaded with gastric cancer or other tumors.

Bacteria-template synthesized silver microspheres with hollow and porous structures as excellent SERS substrate

Template-driven strategy is widely explored for the synthesis of nano/micro materials. Of all the templates studied, naturally occurring biological systems such as proteins, viruses and bacteria have attracted more attention due to the prolific sources and complex structural diversities. Herein, we report a simple bacteria templated synthesis of silver microspheres over a bottom-up controlled route. These as-prepared silver microspheres not only have narrow size distribution but possess hollow and porous structures. Surface enhanced Raman scattering (SERS) experiments using 2-mercaptopyridine (2-Mpy) as probing molecules show that these hollow porous microspheres can act as excellent substrate for ultrasensitive detecting. The detection limit is as low as 10−15 M and the enhancement factor reaches to 1011. Compared with other conventional SERS substrates, the reproducible, high sensitive and cost-effective Ag microspheres could become an ideal substrate choice for practical SERS application.

Improved EIS performance of an electrochemical cytosensor using three-dimensional architecture Au@BSA as sensing layer.

An ultrasensitive electrochemical cytosensor for quantitative determination of carcinoembryonic antigen (CEA)-positive tumor cells was developed using three-dimensional (3D) architecture Au@BSA microspheres as sensing layer with the conjugation of targeting molecule monoclonal anti-CEA antibody (anti-CEA). The prepared Au@BSA microspheres exhibited satisfactory biocompatibility for cell proliferation via evaluation from thiazolyl blue tetrazolium bromide (MTT) assay, providing a suitable platform for cell adhesion study. Attributed to the excellent electroconductivity of Au@BSA, amplified electrochemical signals could be obtained and resulted in the greatly enhanced detection sensitivity. Electrochemical testing techniques including electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV), and cyclic voltammetry (CV) were applied to assess the optimal conditions, specificity, and detection performance of as-fabricated cytosensor. The attachment of CEA-positive BXPC-3 cells onto the anti-CEA immobilized sensing layer led to the increased EIS responses, which changed linearly in the cell concentration range from 5.2 × 10(1) to 5.2 × 10(7) cells mL(-1) with a detection limit of 18 cells mL(-1). This proposed cytosensing strategy revealed high specificity to CEA-positive cells, acceptable intra-assay precision, excellent fabrication reproducibility with the RSD of 3.5%, and good stability owing to the outside BSA biocompatible layer, developing a promising technique for early monitoring of tumor cells at a lower level.

Ag@BSA Core/Shell Microspheres As an Electrochemical Interface for Sensitive Detection of Urinary Retinal-Binding Protein

The level of urinary retinol-binding protein (RBP) can be estimated as a significant index of renal tubular injury. In this work, we used Ag@BSA microspheres as a sensing interface to cross-link RBP monoclonal antibody (RBP mAb) via glutaraldehyde for sensitive detection of RBP. The Ag@BSA microspheres covered on a Au electrode could provide a larger surface area and multifunctional substrate for the effective immobilization of RBP mAb, and the outside BSA layer acted as a biocompatible support to maintain the bioactivity and stability of immobilized immunogen. Electrochemical measurements containing electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) were employed to evaluate the analytical performance of the fabricated immunosensor and a higher detection sensitivity was obtained by DPV attributed to the excellent electrical conductivity of Ag@BSA which could enhance the peak current response. This immunosensor had a best detection limit (DL) of 18 ng mL(-1) and a linear response range between 50 and 4500 ng mL(-1). The proposed approach showed high specificity for RBP detection, acceptable reproducibility with an RSD of 5.6%, and good precision with the RSD of 4.5% and 6.3% at the RBP concentrations of 500 and 1500 ng mL(-1). Compared with the ELISA method by analyzing real urine samples from a patient, this immunosensor revealed acceptable accuracy with a relative deviation lower than 6.5%, indicating a potential alternative method for RBP detection in clinical diagnosis.

Hierarchically assembled Au microspheres and sea urchin-like architectures: formation mechanism and SERS study.

The hierarchically assembled Au microspheres/sea urchin-like structures have been synthesized in aqueous solution at room temperature with and without proteins (bovine serum albumin, BSA) as mediators. The average diameter of an individual Au microsphere is 300-600 nm, which is composed of some compact nanoparticles with an average diameter of about 15 nm. Meanwhile, the sea urchin-like Au architecture exhibits an average diameter of 600-800 nm, which is made up of some nanopricks with an average length of 100-200 nm. These products are characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electronic microscopy (TEM). It is found that the BSA and ascorbic acid (AA) have great effects on the morphology of the resulting products. Two different growth mechanisms are proposed. The study on surface enhanced Raman scattering (SERS) activities is also carried out between Au microspheres and Au sea urchin-like architectures. It is found that Au urchin-like architectures possess much higher SERS activity than the Au microspheres. Our work may shed light on the design and synthesis of hierarchically self-assembled 3D micro/nano-architectures for SERS, catalysis and biosensors.

Bio-mimetically synthesized Ag@BSA microspheres as a novel electrochemical biosensing interface for sensitive detection of tumor cells

The use of a novel cytosensor, comprised of bio-mimetically synthesized Ag@BSA composite microspheres, for the detection of KB cells (a model system) is described. The Ag@BSA composite microspheres were immobilized on Au electrodes via Au-thiol bonds. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM) images revealed that the Ag@BSA were well-dispersed microspheres with an average diameter of 500 nm, including the monolayer of BSA. The immobilization of Ag@BSA composite microspheres onto Au electrodes is thought to increase the electrode surface area and accelerate the electron transfer rate while providing a highly stable matrix for the convenient conjugation of target molecules (such as folic acid) and the prolonged incubation of cells. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) studies showed that the fabricated cytosensor was able to detect KB cells ranging from 6.0×10(1) to 1.2×10(8) cells mL(-1) with a lower detection limit of 20 cells mL(-1). Due to its facile synthesis, high stability and reproducibility and cytocompatibility, the novel cytosensor described here could find multifarious uses in applications, such as cancer diagnosis, drug screening and cell adhesion studies.

Protein-directed solution-phase green synthesis of BSA-conjugated M(x)Se(y) (M = Ag, Cd, Pb, Cu) nanomaterials.

Bovine serum albumin (BSA)-conjugated M(x)Se(y) (M = Ag, Cd, Pb, Cu) nanomaterials with different shapes and sizes were synthesized in water at room temperature by a protein-directed, solution-phase, green synthetic method. The method features very low energy consumption and nontoxic reagents with high yields of concentrated nanoparticles. The obtained bioconjugated nanoparticles have good dispersibility, bioactivity, and biocompatibility. In addition, various functional groups of protein on the surface of the nanocrystals are suitable for further biological interactions or couplings, which is very important for further biological applications.

Microwave Rapid Synthesis of Nanoporous Fe3O4 Magnetic Microspheres

Nanoporous Fe3O4 magnetic microspheres have been successfully synthesized by the way of microwave heating. The experi- mental process is expeditious, simple and environmentally friendly. The obtained sample is characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmett-Teller analysis (BET), Fourier transform infrared (FT-IR), high-resolution transmission electron microscopy (HRTEM) and magnetic measurements. The average size of Fe3O4 microspheres is ~100nm and shows well-dispersed quality in aqueous solution. More importantly, the microspheres possess both nanoporous structure and superparamagnetic behaviour, which endow them powerful application potentials in chemical, biological/biomedical, physical and environmental engineer- ing fields, for example, catalyst or drug carrier, absorption, separation and contrast agents, etc.

Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H2O2.