Can the antibodies be directly attached or some other polymeric/protein based materials must be used on the surface of metallic nanoparticles.
Gold particles (AuNP's) are the most commonly used colloids, and when prepped, already are coated with a lightly bound surface molecule like tannic acid or citrate. Most proteins will bind to these particles as is, because AuNP's are very reactive to SH, NH2 and CN groups. It is usually a better idea to use an intermediate crosslinking molecule like capture proteins of interest. This will help you target your proteins better, control their orientation, and preserve their function (proteins stuck flat to gold can't fold really). Generally, one need to choose a coating molecule that is reactive to a region of the protein of interest. For example, a molecule like SH----NHS will bind to gold through the SH, and to primary amines on proteins through the NHS. THere is an entire subject on crosslinking:
http://www.piercenet.com/browse.cfm?fldID=0203
And if you do use gold, you can find a lot of information in Biacore's manual or other group who would bind stuff to gold. If it binds to bare gold, then should also work on colloids (so we hope)
Gold particles (AuNP's) are the most commonly used colloids, and when prepped, already are coated with a lightly bound surface molecule like tannic acid or citrate. Most proteins will bind to these particles as is, because AuNP's are very reactive to SH, NH2 and CN groups. It is usually a better idea to use an intermediate crosslinking molecule like capture proteins of interest. This will help you target your proteins better, control their orientation, and preserve their function (proteins stuck flat to gold can't fold really). Generally, one need to choose a coating molecule that is reactive to a region of the protein of interest. For example, a molecule like SH----NHS will bind to gold through the SH, and to primary amines on proteins through the NHS. THere is an entire subject on crosslinking:
http://www.piercenet.com/browse.cfm?fldID=0203
And if you do use gold, you can find a lot of information in Biacore's manual or other group who would bind stuff to gold. If it binds to bare gold, then should also work on colloids (so we hope)
Our experience of preparation of colloidal dispersions, based on various peptides and gold or silver nanoparticles, showes that peptides reduce gold ions from the HAuCl4 acid and stabilize the surface of the nanoparticles.The reducing Au 3+ ions by peptide results in a moderate peptide degradation. In this case, according to IR-data, the peptide bonds split. Also, there is a transition from trans-configuration of the original peptide to cis-configuration of the peptide group in colloidal dispersions. It can be assumed that ionized carboxyl groups of the terminal sites and side chains of peptide molecules, participated in the stabilization of highly reactive gold nanoparticles, form hydrogen bridges with the surface of the metal. This results in a change of the structure of solid composite layers. As for antibodies, probably better pre-coat the surface of nanoparticles by a stabilizer, such as polyethylene glycol. In this case, the properties of antibody are not affected.
One way is presented in this publication:
Article Magnetic Gold Nanoparticles in SERS-Based Sandwich Immunoass...
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