Biomolecular recognition at phospholipid-covered polystyrene microspheres

Cholera toxin and its receptor (the monosialoganglioside GM1) are used as a model pair to evaluate phospholipid-covered polystyrene microspheres regarding their suitability as a matrix to promote biomolecular recognition. Toxin binding to GM1/phosphatidylcholine-covered polystyrene microspheres occurs in a molar proportion of 1:1 (toxin/GM1) and is strictly dependent on GM1 incorporation in the phospholipid-covered latex. Phospholipid coverage on latex offers a proper environment to GM1/toxin recognition. Phospholipid assembly on the latex surface depends on the physical state of the bilayer. A dipalmitoylphosphatidylcholine (DPPC) monolayer coverage on latex at room temperature can be obtained by incubating latex and DPPC vesicles in buffer solution for 1 h at 65 degrees C. Nonspecific physical adsorption of cholera antitoxin on latex surfaces can be controlled by covering latex with phospholipids. Upon increasing dipalmitoylphosphatidylcholine (DPPC) concentration in latex dispersions, nonspecific cholera antitoxin adsorption on latex decreases. This provides a way of modulating protein adsorption on the DPPC-covered latex. Changing the hydrophobic-hydrophilic character of the antitoxin itself by covalent attachment of an N-acyl residue increases physical adsorption on bare latex and decreases it on phospholipid-covered latex. The results may be of importance in development of immunoassays and biosensors for amplification of biomolecular recognition.