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Biomedical subjects

Jwa-Min Nam

Publications and source records attributed to Jwa-Min Nam.

15 recordsLinked to original sources
PubMed2006

A bio-barcode assay for on-chip attomolar-sensitivity protein detection.

Functionalized nanoparticles hold great promise in realizing highly sensitive and selective biodetection. We report a single disposable chip which is capable of carrying out a multi-step process that employs nanoparticles--a bio-barcode assay (BCA) for single protein marker detection. To illustrate the capability of the system, we tested for the presence of prostate specific antigen (PSA) in buffer solution and goat serum. Detection was accomplished at PSA concentrations as low as 500 aM. This corresponds to only 300 copies of protein analytes using 1 microL total sample volume. We established that the on-chip BCA for PSA detection offers four orders of magnitude higher sensitivity compared to commercially available ELISA-based PSA tests.

Animals↗
PubMed2005

Colorimetric bio-barcode amplification assay for cytokines.

The bio-barcode amplification assay has become a powerful tool in detecting tens to hundreds of biological targets such as proteins and nucleic acids in the entire sample. However, current bio-barcode detection schemes still require many experimental steps including microarrayer-based immobilization of oligonucleotides on a glass chip, silver enhancement of immobilized gold nanoparticles on a chip, and light-scattering measurement. Here, we report a colorimetric bio-barcode method that minimizes the above requirements while detecting 30 aM concentrations of cytokines (approximately 3 orders of magnitude more sensitive than conventional nonenzymatic cytokine detection assays). The assay is based on porous microparticles, which enable loading of a large number of barcode DNA per particle, and gold nanoparticle-based colorimetric barcode detection method.

Colorimetry↗
PubMed2005

A modular microfluidic architecture for integrated biochemical analysis.

Microfluidic laboratory-on-a-chip (LOC) systems based on a modular architecture are presented. The architecture is conceptualized on two levels: a single-chip level and a multiple-chip module (MCM) system level. At the individual chip level, a multilayer approach segregates components belonging to two fundamental categories: passive fluidic components (channels and reaction chambers) and active electromechanical control structures (sensors and actuators). This distinction is explicitly made to simplify the development process and minimize cost. Components belonging to these two categories are built separately on different physical layers and can communicate fluidically via cross-layer interconnects. The chip that hosts the electromechanical control structures is called the microfluidic breadboard (FBB). A single LOC module is constructed by attaching a chip comprised of a custom arrangement of fluid routing channels and reactors (passive chip) to the FBB. Many different LOC functions can be achieved by using different passive chips on an FBB with a standard resource configuration. Multiple modules can be interconnected to form a larger LOC system (MCM level). We demonstrated the utility of this architecture by developing systems for two separate biochemical applications: one for detection of protein markers of cancer and another for detection of metal ions. In the first case, free prostate-specific antigen was detected at 500 aM concentration by using a nanoparticle-based bio-bar-code protocol on a parallel MCM system. In the second case, we used a DNAzyme-based biosensor to identify the presence of Pb(2+) (lead) at a sensitivity of 500 nM in <1 nl of solution.

Biochemistry↗
PubMed2005

Nanoparticle-based detection in cerebral spinal fluid of a soluble pathogenic biomarker for Alzheimer's disease.

The recently developed ultrasensitive bio-barcode assay was used to measure the concentration of amyloid-beta-derived diffusible ligands (ADDLs), a potential soluble pathogenic Alzheimer's disease (AD) marker, in the cerebrospinal fluid (CSF) of 30 individuals. ADDL concentrations for the subjects diagnosed with AD were consistently higher than the levels in the CSF taken from nondemented age-matched controls. Studies of ADDLs or for any other potential pathogenic AD markers in CSF have not been possible because of their low concentration in CSF (<1 pM). This study is a step toward a diagnostic tool, based on soluble pathogenic markers for the debilitating disease.

Alzheimer Disease↗
PubMed2003

Raman dye-labeled nanoparticle probes for proteins.

In this paper, we demonstrate how one can chemically design Raman dye-functionalized nanoparticle probes with specific protein-binding affinities and use these probes, coupled with surface-enhanced Raman scattering (SERS) spectroscopy, to perform multiplexed screening of protein-small molecule interactions and protein-protein interactions in a protein microarray format.

2,4-Dinitrophenol↗
PubMed2003

Real-time multicolor DNA detection with chemoresponsive diffraction gratings and nanoparticle probes.

We report a real-time DNA detection method that utilizes single-strand DNA-modified nanoparticle probes and micropatterned chemoresponsive diffraction gratings interrogated simultaneously at multiple laser wavelengths. The surface-bound nanoparticle probe based assay with the chemoresponsive diffraction grating signal transduction scheme results in an experimentally simple DNA detection protocol, displaying attributes of both detection methodologies: the high sensitivity and selectivity afforded by nanoparticle probes and the experimental simplicity, wavelength-dependent resonant enhancement features, and miniaturization potential provided by the diffraction-based sensing technology.

Antigens, Bacterial↗
PubMed2003

Nanoparticle-based bio-bar codes for the ultrasensitive detection of proteins.

An ultrasensitive method for detecting protein analytes has been developed. The system relies on magnetic microparticle probes with antibodies that specifically bind a target of interest [prostate-specific antigen (PSA) in this case] and nanoparticle probes that are encoded with DNA that is unique to the protein target of interest and antibodies that can sandwich the target captured by the microparticle probes. Magnetic separation of the complexed probes and target followed by dehybridization of the oligonucleotides on the nanoparticle probe surface allows the determination of the presence of the target protein by identifying the oligonucleotide sequence released from the nanoparticle probe. Because the nanoparticle probe carries with it a large number of oligonucleotides per protein binding event, there is substantial amplification and PSA can be detected at 30 attomolar concentration. Alternatively, a polymerase chain reaction on the oligonucleotide bar codes can boost the sensitivity to 3 attomolar. Comparable clinically accepted conventional assays for detecting the same target have sensitivity limits of approximately 3 picomdar, six orders of magnitude less sensitive than what is observed with this method.

Antibodies↗
PubMed2002

Bio-barcodes based on oligonucleotide-modified nanoparticles.

By utilizing oligonucleotide-modified Au nanoparticles encoded with sequences that act as biobarcodes, one can screen for multiple target polyvalent proteins simultaneously in one solution. This novel concept was demonstrated with two types of detection formats, a homogeneous assay and one based on oligonucleotide microarrays. With such an approach, one can prepare an extraordinarily large number of barcodes from synthetically accessible oligonucleotides (e.g., a 12-mer sequence offers 4(12) possible barcodes).

Biosensing Techniques↗