Molecular imprinting of Ricin and its A and B chains to organic silanes: fluorescence detection

The stable physical properties of molecular imprints make them ideal artifi cial receptors, i.e., biosensor sensing elements, for detection systems aga inst chemical and biological toxins, drugs, and environmental contaminants [B. Dave, B. Dunn, J. Selverstone Valentine, J. Zink, Anal. Chem. 66 (1994) 1120-1127; O. Lev, M. Tsionsky, L. Rabinovich, V. Glezer, S. Sampath, I. P ankratov, J. Gun, Anal. Chem. 67 (1995) 22-30; R. Wang, U. Narang, P. Prasa d, F. Bright, Anal. Chem. 65 (1993) 2671-2675; S.A. Piletsky, Y.P. Parhomet z, N.V. Lavryk, T.L. Panasyuk, A.V. El'skaya, Sens. Actuators, B 18-19 (199 4) 629-631; M.P. Byfield, R.A. Abuknesha, Biosens. Bioelectron. 9 (1994) 37 3-400] and afford them advantages over traditional screening techniques suc h as purified receptors and antibodies which require elaborate preparative techniques and complex environments. Molecular imprints to the deadly casto r bean Pectin Ricin (Ricinus communis, Toxin RCA(60)) and its 'A' and 'B' c hains were prepared, and their respective binding constants determined usin g steady-state fluorescence. Stern-Volmer fluorescence quenching plots usin g iodide and acrylamide suggest imprint associated Ricin B chain tryptophan s are more accessible to the solvent environment than those of the Ricin A chain. Scatchard analysis revealed two affinities for Ricin binding to Rici n imprints, i.e., K-d = 34 nM and 319 nM. Similarly, high affinity interact ion of Ricin A and B chains with their respective imprints were observed (K -d congruent to 100 nM). Interestingly, Scatchard analysis of Ricin B chain binding to Ricin imprints revealed two apparent affinities (K-d = 0.23 and 25 nM) whereas, Ricin B chain binding to A chain imprints exhibited one hi gh affinity constant (K-d = 8.9 nM). These data support the usefulness of i ntrinsic fluorescence and molecular imprints for detection of large protein s and biological toxins. (C) 2000 Elsevier Science B.V. All lights reserved .