Chun-Hua Lu

A Graphene Platform for Sensing Biomolecules

Sensitive platform: The use of graphene oxide (GO) as a platform for the sensitive and selective detection of DNA and proteins is presented. The interaction of GO and dye-labeled single-stranded DNA leads to quenching of the dye fluorescence. Conversely, the presence of a target DNA or protein leads to the binding of the dye-labeled DNA and target, releasing the DNA from GO, thereby restoring the dye fluorescence (see picture).

Using graphene to protect DNA from cleavage during cellular delivery

We have proved that functionalized nanoscale graphene oxide can protect oligonucleotides from enzymatic cleavage and efficiently deliver oligonucleotides into cells.

Bioresponsive controlled release using mesoporous silica nanoparticles capped with aptamer-based molecular gate.

This communication describes the design of a novel and general bioresponsive controlled-release mesoporous silica (MS) nanoparticles system based on aptamer-target interactions. In this system, the pores of MS were capped with Au nanoparticles modified with aptamer (ATP aptamer in this case). By a competitive displacement reaction, the Au nanoparticles were uncapped in the presence of ATP molecule, and the cargo was released. Our results demonstrated that the aptamer-target interaction may be a promising route for the design of custom-made controlled-release nanodevices specifically governed by target biomolecules. Since aptamers have been obtained for a broad range of targets, including several cancer biomarkers, we believe that this aptamer-based controlled-release system should have an equally broad spectrum of applications.

Mussel-inspired molecularly imprinted polymer coating superparamagnetic nanoparticles for protein recognition

In this work, we report a facile approach for imprinting protein based on self-polymerization of dopamine in the presence of template protein on the Fe3O4 nanoparticles (NPs) surface. Dopamine, commonly known as a neurotransmitter, is also a small-molecule mimic of the adhesive proteins of mussels. Self-polymerization of dopamine can produce a thin polydopamine (PDA) layer on Fe3O4 NPs surface. During the self-polymerization of dopamine, some template protein molecules were embedded in the PDA layer. After the removal of these embedded protein molecules, the protein imprinted sites are created. The prepared imprinted Fe3O4@PDA NPs shows high binding capacity and acceptable specific recognition behavior towards template proteins.

pH‐Stimulated DNA Hydrogels Exhibiting Shape‐Memory Properties

Nucleic acid-functionalized polyacrylamide chains that are cooperatively cross-linked by i-motif and nucleic acid duplex units yield, at pH 5.0, DNA hydrogels exhibiting shape-memory properties. Separation of the i-motif units at pH 8.0 dissolves the hydrogel into a quasi-liquid phase. The residual duplex units provide, however, a memory code in the quasi-liquid allowing the regeneration of the hydrogel shape at pH 5.0.

Sensing HIV related protein using epitope imprinted hydrophilic polymer coated quartz crystal microbalance

We have developed a biomimetic sensor for the detection of human immunodeficiency virus type 1 (HIV-1) related protein (glycoprotein 41, gp41) based on epitope imprinting technique. gp41 is the transmembrane protein of HIV-1 and plays an important role in membrane fusion between viruses and infected cells. It is an important index for determining the extent of HIV-1 disease progression and the efficacy of therapeutic intervention. In this work, dopamine was used as the functional monomer and polymerized on the surface of quartz crystal microbalance (QCM) chip in the presence of template, a synthetic peptide with 35 amino acid residues, analogous to residues 579-613 of the gp41. This process resulted in grafting a hydrophilic molecularly imprinted polymer (MIP) film on the QCM chip. QCM measurement showed that the resulting MIP film not only had a great affinity towards the template peptide, but also could bind the corresponding gp41 protein specifically. The dissociation constant (K(d)) of MIP for the template peptide was calculated to be 3.17 nM through Scatchard analysis, which was similar to those of monoclonal antibodies. Direct detection of the gp41 was achieved quantitatively using the resulting MIP-based biomimetic sensor. The detection limit of gp41 was 2 ng/mL, which was comparable to the reported ELISA method. In addition, the practical analytical performance of the sensor was examined by evaluating the detection of gp41 in human urine samples with satisfactory results.

Cysteine-Mediated Aggregation of Au Nanoparticles: The Development of a H2O2 Sensor and Oxidase-Based Biosensors

The cysteine-stimulated aggregation of Au nanoparticles (Au NPs) is used as an auxiliary reporting system for the optical detection of H2O2, for optical probing of the glucose oxidase (GOx) and the catalyzed oxidation of glucose, for probing the biocatalytic cascade composed of acetylcholine esterase/choline oxidase (AChE/ChOx), and for following the inhibition of AChE. The analytical paradigm is based on the I(-)-catalyzed oxidation of cysteine by H2O2 to cystine, a process that prohibits the cysteine-triggered aggregation of the Au NPs. The system enabled the analysis of H2O2 with a detection limit of 2 μM. As the GOx-biocatalyzed oxidation of glucose yields H2O2, and the AChE/ChOx cascade leads to the formation of H2O2, the two biocatalytic processes could be probed by the cysteine-stimulated aggregation of the Au NPs. Since AChE is inhibited by 1,5-bis(4-allyldimethylammonium phenyl)pentane-3-one dibromide, the biocatalytic AChE/ChOx cascade is inhibited by the inhibitor, thus leading to the enhanced cysteine-mediated aggregation of the NPs. The results suggest the potential implementation of the cysteine-mediated aggregation of Au NPs in the presence of AChE/ChOx as a sensing platform for the optical detection of chemical warfare agents.

Amplified and multiplexed detection of DNA using the dendritic rolling circle amplified synthesis of DNAzyme reporter units.

The amplified, highly sensitive detection of DNA using the dendritic rolling circle amplification (RCA) is introduced. The analytical platform includes a circular DNA and a structurally tailored hairpin structure. The circular nucleic acid template includes a recognition sequence for the analyte DNA (the Tay-Sachs mutant gene), a complementary sequence to the Mg(2+)-dependent DNAzyme, and a sequence identical to the loop region of the coadded hairpin structure. The functional hairpin in the system consists of the analyte-sequence that is caged in the stem region and a single-stranded loop domain that communicates with the RCA product. The analyte activates the RCA process, leading to DNA chains consisting of the Mg(2+)-dependent DNAzyme and sequences that are complementary to the loop of the functional hairpin structure. Opening of the coadded hairpin releases the caged analyte sequence, resulting in the dendritic RCA-induced synthesis of the Mg(2+)-dependent DNAzyme units. The DNAzyme-catalyzed cleavage of a fluorophore/quencher-modified substrate leads to a fluorescence readout signal. The method enabled the analysis of the target DNA with a detection limit corresponding to 1 aM. By the design of two different circular DNAs that include recognition sites for two different target genes, complementary sequences for two different Mg(2+)-dependent DNAzyme sequences and two different functional hairpin structures, the dendritic RCA-stimulated multiplexed analysis of two different genes is demonstrated. The amplified dendritic RCA detection of DNA is further implemented to yield the hemin/G-quadruplex horseradish peroxidase (HRP)-mimicking DNAzyme as catalytic labels that provide colorimetric or chemiluminescent readout signals.

Stimuli-responsive DNA-functionalized nano-/microcontainers for switchable and controlled release.

Stimuli-responsive DNA-functionalized nano- and microcontainers composed of mesoporous SiO2 nanoparticles (MP SiO2 NPs), microcapsules, or micelles/vesicles act as carriers for the transport and release of drugs. The information encoded in the DNA sequences provides instructive information for the gating of drug-loaded pores of MP SiO2 NPs, for the assembly and degradation of microcapsules or lipid-DNA micelles/vesicles, and for the targeting of nano-/microcontainers to cancer cells. Different triggers are applied to release the drugs loaded in the nano-/microcontainers by unlocking the pores of the MP SiO2 NPs or by degradation of the containers. These include the use of switchable DNA nanostructures (nucleic acid hairpins, i-motif, G-quadruplexes) and the implementation of chemical, thermal, or photonic stimuli. Also, catalytic processes stimulated by DNAzymes or enzymes are used to release drugs from the nano-/microcontainers.

A Three-Station DNA Catenane Rotary Motor with Controlled Directionality

The assembly of DNA machines represents a central effort in DNA nanotechnology. We report on the first DNA rotor system composed of a two-ring catenane. The DNA rotor ring rotates in dictated directions along a wheel, and it occupies three distinct sites. Hg(2+)/cysteine or pH (H(+)/OH(-)) act as fuels or antifuels in positioning the rotor ring. Analysis of the kinetics reveals directional clockwise or anticlockwise population of the target-sites (>85%), and the rotors direction is controlled by the shortest path on the wheel.