Biomedical subjects

Yougen Li

Publications and source records attributed to Yougen Li.

7 recordsLinked to original sources

PubMed2006

A dendrimer-like DNA-based vector for DNA delivery: a viral and nonviral hybrid approach.

DNA can be used as a generic delivery vector in addition to its genetic role as a antigen expression vector. This is inspired in part by the fact that DNA molecules are true polymers. Surprisingly, DNA molecules have not been used as a delivery vector material. This is probably due to the fact that almost all DNA have only two shapes: linear or circular. This chapter details our efforts in fabricating highly branched dendrimer-like DNA (DL-DNA) that may serve as a multivalent DNA delivery vector. Just like chemical dendrimers, DL-DNA is multi-valent and monodisperse. However, unlike traditional chemical dendrimers, DL-DNA is much larger (~100 nm, generation 4) and can be designed to be nonsymmetric as well. Most importantly, DL-DNA possesses two unique properties: anisotropicity and biodegradability, making multiple, specific conjugations of viral peptides possible. Our method suggests that viral-pep-tide conjugated DL-DNA vectors can deliver genes into cells without any other transfection reagents. This viral-nonviral hybrid system can be further tailored to specific cells by conjugating specific ligands. We believe that such a DL-DNA-based, viral, and nonviral hybrid assembly will provide a new platform for drug delivery in general and gene delivery in particular.

Dendrimers↗

PubMed2006

Multiplexed molecular detection using encoded microparticles and nanoparticles.

Signal-encoded microparticles and nanoparticles have been used to label many reactions simultaneously for target identification in assays, and thus are an indispensable part of multiplex technologies. With the increasing demand for multiplexed molecular detection, encoded particles have evolved from pattern encoding to signal-intensity encoding, and also from signal-molecule encapsulation to signal-molecule tagging. The fabrication and utilization of such nano- and microparticles should advance multiplexed analysis. This short review focuses on how these encoded particles work and briefly touches on their applications in multiplexed molecular detection.

Biological Assay↗

PubMed2005

Nucleoside phosphocholine amphiphile for in vitro DNA transfection.

A new transfection reagent based on nucleoside phosphocholine amphiphile leading to high transfection efficacy and low cytotoxicity is described. TEM, ethidium bromide displacement assays, agarose gel electrophoresis and SAXS studies support the formation of lipoplexes for the transfection of CHO cells.

Animals↗

PubMed2005

Multiplexed detection of pathogen DNA with DNA-based fluorescence nanobarcodes.

Rapid, multiplexed, sensitive and specific molecular detection is of great demand in gene profiling, drug screening, clinical diagnostics and environmental analysis. One of the major challenges in multiplexed analysis is to identify each specific reaction with a distinct label or 'code'. Two encoding strategies are currently used: positional encoding, in which every potential reaction is preassigned a particular position on a solid-phase support such as a DNA microarray, and reaction encoding, where every possible reaction is uniquely tagged with a code that is most often optical or particle based. The micrometer size, polydispersity, complex fabrication process and nonbiocompatibility of current codes limit their usability. Here we demonstrate the synthesis of dendrimer-like DNA-based, fluorescence-intensity-coded nanobarcodes, which contain a built-in code and a probe for molecular recognition. Their application to multiplexed detection of the DNA of several pathogens is first shown using fluorescence microscopy and dot blotting, and further demonstrated using flow cytometry that resulted in detection that was sensitive (attomole) and rapid.

Bacillus anthracis↗

PubMed2005

Diffusion of single star-branched dendrimer-like DNA.

We report a single-molecule fluorescence study on the diffusion of star-branched polymer dendrimer-like DNA (DL-DNA). The DL-DNA molecules were synthesized from ligating Y-shaped DNA to the fourth generation. It was found through single particle tracking that the diffusion coefficient of DL-DNA changes in a nonmonotonic fashion with its increased concentration possibly due to arm arrest and arm retraction. The diffusion of DL-DNA in linear lambda DNA solution displayed a monotonic concentration dependence 1 order of magnitude greater than the diffusion of DL-DNA in DL-DNA solution. This difference is attributed to the different conformation of DL-DNA and lambda DNA and the entanglement of lambda DNA with a large radius of gyration. Our diffusion study facilitates DL-DNA transportation for drug delivery.

Benzoxazoles↗

PubMed2004

Charge-reversal amphiphiles for gene delivery.

Delivering a missing gene or a functional substitute of a defective gene has the potential to revolutionize current medical care. Of the two gene delivery approaches, viral and synthetic vectors, synthetic cationic vectors possess several practical advantages but suffer from poor transfection efficiency. A new approach to gene delivery using charge-reversal amphiphiles is described. This synthetic vector transforms from a cationic to an anionic amphiphile intracellularly. This amphiphile performs two roles: first, it binds and then releases DNA, and second, as an anionic multicharged amphiphile, it destabilizes lipid bilayers. A charge-reversal amphiphile was synthesized and fully characterized, including the supramolecular complex it forms with DNA. Enhanced gene transfection was observed using these vectors compared to current cationic amphiphiles.

Animals↗

PubMed2003

Controlled assembly of dendrimer-like DNA.

DNA possesses many desirable chemical/physical properties as a polymeric material. With the myriad of tools available to manipulate DNA, there is great potential for using DNA as a generic instead of a genetic material. Although much progress has been made in DNA computing and DNA nanotechnology, the full achievement of DNA-based materials has not yet been realized. As almost all DNA molecules are either linear or circular, to rationally construct DNA materials one must first create additional shapes of DNA as basic building blocks. In addition, these DNA building blocks must be readily incorporated into larger structures in a controlled manner. Here, we show the controlled assembly of dendrimer-like DNA (DL-DNA) from Y-shaped DNA (Y-DNA). The synthesis of Y-DNA and controlled assembly of DL-DNA were robust and efficient; the resulting DL-DNA was stable and almost monodisperse. The multivalent DNA dendrimers can be either isotropic or anisotropic, providing great potential to link other entities.

Base Sequence↗