Dianjun Liu

Functional gold nanoparticle-peptide complexes as cell-targeting agents.

In this paper, we report a novel approach using peptide CALNN and its derivative CALNNGGRRRRRRRR (CALNNR(8)) to functionalize gold nanoparticles for intracellular component targeting. The translocation is effected by the nanoparticle diameter and CALNNR(8) surface coverage. The intracellular distributions of the complexes are change from the cellular nucleus to the endoplasmic reticulum by increasing the density of CALNNR(8) at a constant nanoparticle diameter. Additionally, increasing the nanoparticle diameter at a constant density of CALNNR(8) leads to less cellular internalization. These translocations of the complexes cause unique colorimetric expressions of the cell structure. The cell viability is affected by the internalized gold nanoparticle-peptide complexes in terms of quantities of particles per cell. In addition, the intracellular distribution of the fluorescence quenching is investigated by a fluorescent confocal scanning laser microscopy, which also gives further evidence of intracellular distribution of the gold nanoparticle-peptide complexes.

Microarray-Based Study of Carbohydrate-Protein Binding by Gold Nanoparticle Probes

In order to develop a novel high-throughput tool for monitoring carbohydrate-protein interactions, we prepared carbohydrate or glycoprotein microarrays by immobilizing amino modified carbohydrates on aldehyde-derivatized glass slides or glycoprotein on epoxide-derivatized glass slides and carried out lectin binding experiments by using these microarrays, respectively. The interaction events are marked by attachment of gold nanoparticles followed by silver deposition for signal enhancement. The attachment of the gold nanoparticles is achieved by standard avidin-biotin chemistry. The detection principle is resonance light scattering (RLS). The well-defined recognition systems, namely, three monosaccharides (Man-alpha, Glc-beta and Gal-beta) or three glycoproteins (Asf, RNase A and RNase B) with two lectins (ConA and RCA120), were chosen here to establish the RLS assay, respectively. Highly selective recognition of carbohydrate-protein down to 25.6 pg/mL for RCA120 in solution and 8 microM for Gal-beta and 32 ng/mL for Asf on the microarray spots is demonstrated.

Resonance light scattering as a powerful tool for sensitive detection of β-amyloid peptide by gold nanoparticle probes.

A novel biosensing strategy has been developed for sensitive detection of β-amyloid 1-42 (Aβ(1-42)) down to the ng mL(-1) level in both aqueous solution and diluted human plasma, which is based on measuring changes in resonance light scattering of streptavidin functionalized gold nanoparticles as a function of the concentration of Aβ(1-42) with a conventional spectrofluorometer.

Nanoparticle-based systems for T(1)-weighted magnetic resonance imaging contrast agents.

Because magnetic resonance imaging (MRI) contrast agents play a vital role in diagnosing diseases, demand for new MRI contrast agents, with an enhanced sensitivity and advanced functionalities, is very high. During the past decade, various inorganic nanoparticles have been used as MRI contrast agents due to their unique properties, such as large surface area, easy surface functionalization, excellent contrasting effect, and other size-dependent properties. This review provides an overview of recent progress in the development of nanoparticle-based T1-weighted MRI contrast agents. The chemical synthesis of the nanoparticle-based contrast agents and their potential applications were discussed and summarized. In addition, the recent development in nanoparticle-based multimodal contrast agents including T1-weighted MRI/computed X-ray tomography (CT) and T1-weighted MRI/optical were also described, since nanoparticles may curtail the shortcomings of single mode contrast agents in diagnostic and clinical settings by synergistically incorporating functionality.

Gold nanoparticle based dot-blot immunoassay for sensitively detecting Alzheimer's disease related β-amyloid peptide

A simple, sensitive gold nanoparticle (GNP)-based dot-blot immunoassay has been developed for detecting Alzheimers disease related β-amyloid peptide 1-42 (Aβ(1-42)) down to a 50 pg mL(-1) level in aqueous solution. Practical samples (cerebrospinal fluid (CSF), cell culturing mediums and cell lysates) have been used to demonstrate the ability of the assay.

Preparation of graphene oxide-silver nanoparticle nanohybrids with highly antibacterial capability

A simple method based on electrostatic interactions was utilized to assemble silver nanoparticles (AgNPs) to graphene oxide (GO) sheets. This method allows conjugation of AgNPs with desired morphologies (densities, sizes and shapes) onto GO. In this process, poly(diallyldimethylammonium chloride) (PDDA) was introduced as an adhesive agent. The as-prepared graphene oxide-AgNPs composites (GO-AgNPs) have enhanced colloid stability and photo-stability than that of AgNPs. After conjugating to GO sheets, the antibacterial activities of AgNPs against Gram negative (G-) bacterial strain (Escherichia coli, E. coli) and Gram positive (G+) bacterial strain (Bacillus subtilis, B. subtilis) have been improved significantly. The antibacterial activity of GO-AgNPs is dependent on the size of AgNPs, i.e. the small AgNPs modified GO sheets show more effective antibacterial capability than that of large AgNPs modified GO sheets. Compared with AgNPs, the enhanced antibacterial activity of GO-AgNPs might not only be due to high stability of AgNPs anchored on GO sheets, but also the positive charged surface of hybrids which increases the electrostatic interaction of bacterial cell membrane with nanohybrids.

Gold nanoparticle-based colorimetric sensor for studying the interactions of β-amyloid peptide with metallic ions

In this paper, a kind of beta-amyloid peptide (Abeta1-16) conjugated gold nanoparticles (Abeta1-16@GNPs) are prepared and employed as colorimetric indicator for studying the interaction of beta-amyloid peptide with metallic ions (e.g. Zn(2+) and Ca(2+)). In the presence of Zn(2+), mono-dispersing Abeta1-16@GNPs enable to form aggregates or attach on the SHG-44 (human glioma cell) cellular surface which results in significant color change of the solution. The experimental results indicate that Zn(2+) can interact with Abeta1-16 and form Zn(2+)-beta-amyloid peptide complexes. In particular, in the presence of Zn(2+), a time-dependent interaction of cells with Abeta1-16@GNPs has been observed that may suggest different expression levels of beta-amyloid peptide related proteins in various cell cycles. In addition, the aggregating/binding process can be easily reversed by adding EDTA, a good chelated ligand of Zn(2+), which gives further proof of the interaction mechanism.

Sensitive detection of protein kinase A activity in cell lysates by peptide microarray-based assay.

In the present work, the activities of protein kinase A (PKA) in cell lysates have been detected by a peptide microarray-based resonance light scattering assay with gold nanoparticle probes. Highly sensitive detection of PKA activity in 0.1 μg total cell proteins of SHG-44 cell lysate (corresponding to 200 cells) is achieved by a selected peptide substrate. The experimental results also demonstrate that the assay can be employed to evaluate expression levels of PKA activity in different cell lines and chemical (e.g., Forskolin )-mediated PKA activity fluctuation in living cells. In addition, PKA inhibition by the inhibitor (H89) is shown, suggesting the potential for screening PKA inhibitors at the living cell level.

Screening lectin-binding specificity of bacterium by lectin microarray with gold nanoparticle probes.

To develop a novel high-throughput tool for monitoring specific affinity of microbes with lectins, a kind of lectin microarray has been fabricated by immobilizing lectins on epoxide-derivatized glass slides and used to capture microbes. The capturing events are marked by attachment of lectin-conjugated gold nanoparticles followed by silver deposition to enhance the resonance light scattering (RLS) of the particles. The interactions of 16 lectins with four bacteria and one fungus were profiled by this approach. We demonstrated that the gold-nanoparticle-labeled array was suitable for identifying the binding affinity of lectin with bacterium, as well as determining the bacterium with high sensitivity. More importantly, we found that the growth of microbial strains in different culture media resulted in significant changes in their binding affinities with lectins, which might be important to the pathogenesis of the organisms.

Highly selective recognition of naphthol isomers based on the fluorescence dye-incorporated SH-β-cyclodextrin functionalized gold nanoparticles.

In present work, a rhodamine 6G (Rh 6G)-incorporated β-cyclodextrin functionalized gold nanoparticle (Rh 6G-CD-AuNP) based fluorescent assay has been successfully developed for recognizing/detecting the structural isomers, α-naphthol and β-naphthol, in aqueous solution. The β-cyclodextrin functionalized gold nanoparticles (CD-AuNPs) are achieved by conjugating the thiolated β-cyclodextrin (SH-β-CD) with AuNPs via S-Au covalent bonds. Rhodamine 6G (Rh 6G) is chosen as a fluorescent probe in this approach because it can be strongly absorbed on the surface of AuNP by noncovalent interaction. After binding with β-CD cavity, the naphthols enable to act as electron transfer quenchers of Rh 6G, which lead to significant fluorescence quenching of the dye. Because of different association ability of naphthol isomers with the β-CD cavity, the assay can selectively distinguish α-naphthol and β-naphthol with reasonable sensitivity. Detection of naphthols down to 8 nM with a dynamic range of nearly three orders of magnitude (0.01-8 μM) for α-naphthol and 50 nM with two orders of magnitude (0.1-20 μM) for β-naphthol is demonstrated, respectively. The ability of the method for detecting the content of α-naphthol or β-naphthol in the different naphthol mixtures has also been evaluated.