Carboxylic (-COOH) functionalized silica nanopartices or silica microbeads from Nanocs are made from well controlled proprietary process to enure their narrow size distribution and controlled surface functionality. Carboxylic acid groups on these silica beads can be used to react with amine or hydroxyl groups. Size of our silica beads ranges from 5 nm to 50 microns. Standard deviation of these silica particles is in the range of 10% of listed size parameter. Nanocs also offers various fluorescently labeled and surface functionalized silica particles for wide biomedical research and bioassay development.