Preparation and Characterization of a Sol−Gel Immunosorbent Doped with 2,4-D Antibodies

Abstract

An optimized sol-gel technique was used for the entrapment of 2,4-dichlorophenoxyacetic acid (2,4-D) antibodies in a silica matrix derived from tetraethoxysilane (TEOS). Immunoextraction cartridges with reproducible binding capacity for 2,4-D methyl ester (test solute) were prepared from the doped dry gels and wet hydrogels. Although the surface of these biomaterials was characterized by wide macropores, there was no evidence of antibody leakage, as demonstrated by the good precision of the results obtained from repeated extractions performed in the same cartridge. The 2,4-D antibody (commercially obtained), free or encapsulated, was highly selective toward the esterified 2,4-D molecule. Optimal extraction was achieved from samples containing phosphate buffer 0.01-0.15 M (pH ∼7), which were loaded at a maximal flow rate of 1 mL min -1 in cartridges left under buffer for at least 30 min between consecutive experiments. Recoveries of 100%, for loaded ester amounts lower than the cartridge capacity, were obtained under these conditions. A binding capacity of 130 ng of 2,4-D ester per mg of immobilized antibody, corresponding to 42% of the free antibody activity, was obtained with the best gels. The capacity of these immunosorbent cartridges remained practically constant during eight weeks or 50-60 adsorption-desorption cycles.

Recent bio-applications of sol–gel materials

“…Immunoaffinity chromatography is another major application of antibody doped sol-gel materials. 62,63 A very recent example is provided by the work of Cichna et al 64 which describes a simple HPLC method to prepare samples of canned food (such as beverages, fruits and vegetables) for the determination of bisphenol-A-a food-pollutant known to originate from packaging-using fluorescence detection. The sample preparation method makes use of bisphenol-A antibodies, which are immobilized in a silica matrix by the sol-gel technique.…”

Protein adsorption in static microsystems: effect of the surface to volume ratio

“…Antibody adsorption on bare substrates is the most simple and one of the most popular immobilization methods, even if it leads to low surface coverage and low activity of the physisorbed antibodies. 37 To overcome this limitations adsorption in gels, 39,40 porous media 31,41 or bead-beds 42 are often used to enhance the coverage.…”

Immunoassays for cortisol using antibody-doped sol–gel silica

“…Antibody-antigen reactions based on sol-gel encapsulated antibodies have been well documented in the literature. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] In general, specificity is retained although binding affinity is lower in the sol-gel material as compared to liquid buffer. 17,29 It is somewhat surprising that sol-gel based immunoassays in the area of health monitoring have received relatively little attention.…”