DOI: 10.1002/chem.200500709 Interaction of Bovine Serum Albumin with Chrysotile: Spectroscopic and Morphological Studies Giuseppe Falini, [a, b] Elisabetta Foresti, [b] IsidoroG. Lesci, [b] Bruno Lunelli, [b] Piera Sabatino, [b] and Norberto Roveri* [b] Introduction Chrysotile is the main form of asbestos, the commercial term referring to a group of fibrous silicates with high ten- sile strength, fire and heat resistance, chemical inertia, and electrical resistivity. Because of these properties, chrysotile fibers have been widely utilized for many industrial applica- tions and account for approximately 95% of manufactured asbestos. [1] The layered structure of chrysotile, (Mg 3 Si 2 O 5 (OH) 4 ), con- sists of linked (Si 2 O 5 ) n 2 sheets inserted between brucite- type octahedral layers. On one side, two from every three hydroxyl groups are replaced by apical oxygen of the tetra- hedral silica. The sheets of tetrahedral silica have a lateral dimension smaller than that of the magnesium hydroxide oc- tahedral sheets, resulting in a structural mismatch that is fully compensated by the curvature of the layers. The struc- ture of single crystals of chrysotile is thus characterized by tetrahedral and octahedral layers curled concentrically or spirally, usually around the x axis (orthochrysotile) and seldom around the y axis (parachrysotile), into a tubular structure of about 20–50 nm in diameter. The rolls possess hollow cores with a diameter of about 7–8 nm, because the layers cannot withstand a curvature that is too tight. [2] Mineral chrysotile fibers show different structures (coni- cal, cone-in-cone, cylinder-in-cylinder, polygonal, and spiral- ly concentric tube), depending on the ore growth conditions, which probably differ according to the mineral source loca- tion. The chrysotile morphologies and structures have been widely investigated by using X-ray diffraction, [3] electron mi- croscopy and electron diffraction. [4] Isomorphic substitutions of Mg and Si cations are favored and occur frequently; therefore, variable stoichiometry is characteristic of the nat- ural chrysotile. [5,6] Stoichiometric single nanocrystals of chrysotile were re- cently synthesized as a unique phase with definite structure, morphology, and chemical composition. They consist of nanocrystals showing single-cylinder and two-cylinders mor- phology, with a central hole diameter of 7  1 nm and an outer diameter of 20  2 nm (single cylinder) and 50  3 nm (two cylinders). [7,8] These chrysotile nanocrystals may be Abstract: The biodurability of chryso- tile fibers, which is related to their cy- totoxicity and mutagenic responses, is strongly affected by the surface chemi- cal adsorption of biological molecules. Natural chrysotile is a heterogeneous material in both structure and composi- tion. The availability of synthetic stoi- chiometric chrysotile of constant struc- ture and uniform morphology has al- lowed us to investigate its interaction with bovine serum albumin (BSA). By using transmission electron microscopy (TEM) and atomic force microscopy (AFM), we have obtained the first morphological evidence of albumin ad- sorption onto chrysotile nanocrystals. FTIR spectroscopy was used to quanti- fy modifications of BSA secondary structure that were induced by the sur- face interaction. The protein transition to b-turns allows a stronger interaction between the protein hydrophilic side- chains and the charged asbestos sur- face, which is consistent with hydrogen bonds involving the superficial OH groups. Synthetic stoichiometric chrys- otile nanocrystals were shown to be an ideal reference standard with which to study the interaction of asbestos fibers with biological systems, in order to elu- cidate the chemical mechanisms of as- bestos toxicity. Keywords: adsorption · asbestos · chrysotile · nanocrystals · protein modifications [a] Dr. G. Falini Environmental Chemistry Laboratory, University of Bologna via dell)Agricoltura 5, 48100 Ravenna (Italy) [b] Dr. G. Falini, Prof. E. Foresti, Dr. I. G. Lesci, Prof. B. Lunelli, Prof. P. Sabatino, Prof. N. Roveri Department of Chemistry “G. Ciamician”, Alma Mater Studiorum University of Bologna, via Selmi 2, 40126 Bologna (Italy) Fax: (+ 39) 051-209-9593 E-mail: norberto.roveri@unibo.it # 2006 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim Chem. Eur. J. 2006, 12, 1968 – 1974 1968