Biochips protein chips

Biochips can be used for either measuring differential expression between two populations or for testing for the presence of a DNA sequence (resequencing). Protein chips have been applied in expression profiling and antibody detection, binding specificities of a protein expression library and protein-protein interactions. 

The use of biochips in basic biological research has provided information that was heretofore inaccessible. Protein chips, especially functional microarrays, are used to... 

SELDI-TOF is beginning to offer an alternative to 2DGE. Surface-enhanced laser desorption/ionizitation (SELDI) is an affinity-based mass spectrometric method in which proteins of interest are selectively adsorbed to a chemically modified surface on a biochip (Ciphergen Protein Chip Arrays). 

Biological microchips (biochips) are revolutionizing gene expression analysis and classical genotyping as well as diagnostics and testing. Tlie worldwide markets for biochips are primarily composed of DNA chips, protein chips and laboratory chips. Generally, anays are differentiated from microfluidic systems, which can actively operate analysis, separation and synthetic processes by means of microscopic capillary systems, mini-pumps and mini-valves. Tliese are often called a Tab-on-a-chip . 

Tlie total market volume for biochips was estimated for 1999 to be approximately US 180 million, whereby the percentage of DNA chips is above 90%. Annual growth of more than 30% is expected for the years until 2005. In 2005, the total market volume is expected to amount to US 950 million (US 725 million DNA chips, US 157 milhon for lab chips and US 68 million for protein chips). 

Another important application field comprises biochips, such as DNA or protein chips. A DNA chip (Fig. 9) is a collection of microscopic DNA spots arrayed on a solid surface by covalent attachment to a chemical matrix, which utilize the selective nature of DNA-DNA or DNA-RNA hybridization and fluorophore-based detection for expression profiling, i.e. monitoring expression levels of thousands of genes simultaneously. Plasma polymerization techniques have been applied to achieve larger densities of the DNA probes attached, e.g. HMDS or allylamine coatings. ... 

In contrast to high density arrays low density arrays are made by deposition of pre-synthesized oligonucleotides or proteins on activated surfaces. There are several printing techniques for fabricating microarrays Non-contact biochip arrayers, commonly based on the piezoelectric effect, can apply controlled sub-nanoliter probe volumes to pre-specified locations on the chip surface. Due to the fact that the dispenser does not touch the surface, a non-contact arrayer provides low risk of contamination and is most suitable for printing on soft materials such as hydrogels. 

Zyomyx chip technology is based upon an atomically flat gold surface to which is attached a proprietary SAM (self-assembled monolayer) surface for optimal protein binding (Peluso et al., 2003). The company launched its Protein Profiling Biochip System and Human Cytokine Biochip products in February 2003. 

The Protein Profiling Biochip is composed of six chips assembled in a flow cell cassette device. Each chip provides 200 data points (200 pillars per chip) for a total of 1200 data points per cassette. Pillars are 50 p in diameter. The mesa on each pillar is covered with a self-assembled monolayer (20 to 25 A thickness) of biotin-derivatized PLL-g-PEG groups. A constant grafting ratio of 3.5 parts Lys to 1 part PEG is maintained with variable biotin-PEG content. sAV antibody is immobilized at 0.5 to 2 pmole/cm and Fab fragments at 4 pmole/cm. ... 

Along this line Matsue et al. [37,45,78,79] have developed a number of biochips. Among them are multi-analyte assays for human placental lactogen (HPL) and human chorionic gonadotropin (HCG) [45] and leukocidin, a toxic protein produced by methicillin-resistant Staphylococcus aureus [79]. Figure 37.8 shows an example of a dual immunoassay with SECM detection. The analyte is defined by the position on the chip and the amount of analyte is quantified via the collection current at the UME. The current originates from the reduction of ferrocinium methanol (Fc+) at the UME. Fc+ is produced locally at the chip surface by the enzyme HRP under consumption of H202. 

Bouaidat S, Berendsen C, Thomsen P et al (2004) Micro patterning of cell and protein nonadhesive plasma polymerized coatings for biochip applications. Lab on a Chip 4(6) 632-637... 

In this chapter, we will present different types of biochips, including protein and antibody arrays, as well as carbohydrate, peptide and living cell arrays. We will discuss recent progress and current bottlenecks in high-throughput generation of chip content, surface chemistry, molecule attachment, detection methods, and also applications in the proteomic field and in drug discovery. 

The importance of all this research is that it leads to (or gives ideas about) smaller and ever more intelligent biochips in our bodies, including our brains. Susan Lindquist, director of the MIT Whitehead Institute for Biomedical Research, is working on very small computer chips. She is doing the requisite nanotechnology for this with the help of aberrant shapes of proteins, the prions that are responsible for mad cow disease and Creuzfeldt-Jacob disease in... 

Biochip is a broad term indicating the use of microchip technology in molecular biology and can be defined as arrays of selected biomolecules immobilized on a surface. Most of the biochips use nucleic acids as information molecules but protein biochips are also proving to be useful. The basics of protein biochip construction are similar to those of DNA chip as the glass or the plastic surface is dotted with an array of molecules (these... 

Another application includes glass or silicon chips for DNA or protein detection where the biochemical immobilization of captiue (probe) molecules on the chip surface is based on a particular surface chemistry. The mostconunon surface chemistries on biochips are thiol and silane chemistries. With silane chemistry, the probe molecules are immobilized directly on the silicon or glass substrate. With thiol chemistry, the probe molecules are immobilized on metal spots or electrodes (e.g., gold) which are fabricated by photohthography on glass or silicon... 

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