ABSTRACT
Spherical colloidal polymeric particles, often called nanospheres (particles with diameters from a few nanometers to 100 nm) or microspheres (particles with diameters larger than those of nanospheres but usually smaller than 10 µm), were found to be suitable for attachment (adsorption and/or covalent immobilization) of various proteins, nucleic acids, and their fragments, as well as larger subcellular structures (cf. examples in Ref. 1). Micro-and nanospheres, onto whose surface it was possible to attach these biocompounds in their active form, have found many applications in medical diagnostic tests. Traditional tests (called agglutination tests) allow for the detection and/or semiquantitative determination of chosen compounds without using any special equipment, usually within a few minutes. Agglutination tests directed toward the determination of a given antigen consist of mixing a drop of liquid to be analyzed, usually on a plastic slide, with a drop of suspension containing microspheres with attached antibodies. (Due to the similarity of the colloidal properties of suspensions of polymeric particles to the properties of natural latex from the rubber tree Hevea brasilisensis, the former suspensions are often also called latexes.) As a result of antibody-antigen interactions the microspheres form aggregates. This type of test is illustrated schematically in Figure 1.
