© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

3.5.7.1 Imprint Model

Molecular imprinting^421,422 is an existing technique in which a cocktail of functionalized monomers interacts reversibly with a target molecule using only noncovalent forces. The complex is then crosslinked and polymerized in a casting procedure, leaving behind a polymer with recognition sites complementary to the target molecule in both shape and functionality (Fig. 3.11). Each such site constitutes an induced molecular "memory," capable of selectively binding the target species. In one experiment involving an amino acid derivative target, one artificial binding site per (3.8 nm)³ polymer block was created, only slightly larger than the (2.7 nm)³ sorting rotor receptors described by Drexler¹⁰ (Section 3.4.2). Chiral separations, enzymatic transition state activity, and high receptor affinities up to K_d ~ 10^-7 have been demonstrated, with specificity against closely competing ligands up to DK_d ~ 10^-2 (~20 zJ).

Several difficulties with this approach from a diamondoid engineering perspective include:

1. A sample of the target molecule is required to make each mold.

2. It is currently unknown how to prepare diamondoid castings.

3. Once the imprint has been taken, the site cannot easily be further modified.

Last updated on 7 February 2003