Wednesday, April 20, 2011

Lab on chip technics--- Metal nanoparticles and mini systems

Lab on chip is now. Chip as you know is really small so the agents for detection or reaction should be small too. So lots kinds of nanoparticles are widely used in those minisystems for disease diagnose, pathogen detection and microbiology purification.

First the name of Nano is formally use as prefix to indicate unit multiplication by 10-9. And nanoparticles are size between 1 to 100 nm. Because of their sizes, they have many unique size-depended properties like large surface area and unexpected optical properties as they are small enough to confine their electrons and produce quantum effects. For example gold nanoparticles appear deep red to black in solution which is usually yellow in bulk. And metal nanoparticles which with high surface area, high mechanical strength but ultra- weight, rich electronic properties and excellent chemical, thermal stability and high sensitivity are common used for detection assays. AuNPs (gold nanoparticles) due to those properties like it can be synthesized in a various forms and sizes using different chemical methods which can be attached to many traditional biological probes such as antibodies, ion, DNA and receptors. Here are some examples of how attached nanoparticle works in different detection assays. As what I worte gold nanoparticle has property of scatting and absorbing light. Many cancer cells have unique receptors called EGFR over the cells’ surface and the receptors can be used as the target for the cancers. When the nanoparticle is attached the antibody of EGFR called anti-EGFR the nanoparticle can attach to the surface of the cancer cell. Once it attached, the gold nanoparticle can flashed and make the cancer cell distinguished from the healthy cell. Like the last picture. Here is another example of how gold nanoparticle works to detect DNA. The DNA detection is utilized in a chip-based system based on a sandwich assay. This assay consists of an oligonucleotide-modified glass slide, a NP probe and target DNA. The immobilized DNA strand recognizes the DNA of interest and changes the melting profiles of the targets from an array substrate. This change gave the differentiation of an oligonucleotide sequence from targets with single nucleotide mismatches with a high selectivity.

Those nanoparticles are just like researchers in lab and now I will talk a little about the minibiosensor system like microfluidic chips which is like lab rooms. Recently, miniaturized systems and analyses have become powerful tools in chemical and biological systems due to their high performance, design flexibility, reagent and sample economy, high throughput, miniaturization and automation. Thus, microfluidic devices can dramatically alter the speed and scale of analyses. In biosensing systems in particular, the use of microfluidic chip-based sensors has outstanding advantages, small volumes (nl, pl, fl), small size, low energy consumption, cheap and disposable , high selectivity and sensitivity. There is widely known commercial which tell people a microfluidic device to detect STDs on cellphone kit with is based on this principle.

The integration of metal-NP-based electrochemical detection with microfluidic chips offers a significant advantage because it combines sensitive electrochemical detection with a compact microfluidic platform, thus using the benefits of both technologies. Those two tiny things get together which both have high sensitivity and quick and accurate properties. Therefore, the fabrication of a new platform of miniaturized devices for bioanalysis is a great challenge that will likely be applied in diverse fields, including clinical diagnosis, food analysis, process control and environmental monitoring, in the near future.

Posted by Minhui Dai

1 comment: