Carbon nanotube-protein carriers enhance size-dependent self-adjuvant antibody response to haptens

Carbon nanotubes (CNTs) are nanomaterials with interesting emerging applications. Their properties make CNTs excellent candidates for use as new nanovehicles in drug delivery, immunization and diagnostics. In the current study, we assessed the immune-response-amplifying properties of CNTs to haptens by using azoxystrobin, the first developed strobilurin fungicide, asamodel analyte. Anazoxystrobin derivative bearingacarboxylated spacer arm (hapten AZc6) was covalently coupled to bovine serum albumin (BSA), and the resulting BSA-AZc6 conjugate was covalently linked to four functionalized CNTs of different shapes and sizes, varying in diameter and length. These four types of CNT-based constructs were obtained using efficient, fast, and easy functionalization procedures based on microwave-assisted chemistry. New Zealand rabbits and BALB/c mice were immunized with BSA-AZc6 alone and with the four CNT-BSA-AZc6 constructs, both with and without Freund's adjuvant. The IgG-type antibody responses were assessed in terms of the titer and affinity, paying special attention to the relationship between the immune response and the size and shape of the employed CNTs. Immunization with CNT-BSA-AZc6 resulted in enhanced titers and excellent affinities for azoxystrobin. More important, remarkable IgG responses were obtained even in the absence of an adjuvant, thus proving the self-adjuvanting capability of CNTs. Immunogens were able to produce strong anti-azoxystrobin immune responses in rabbits even when administered at a BSA-AZc6 conjugate dose as low as 0.05 μg. The short and thick CNT-BSA-AZc6 construct produced the best antibody response under all tested conditions. © 2013 Elsevier B.V. All rights reserved.

This work was supported by the Ministerio de Educación y Ciencia (AGL2009-12940-C02-01/02/ALI) and cofinanced by the FEDER funds. J.P. was hired by Consejo Superior de Investigaciones Científicas (CSIC) under a predoctoral I3P contract. J.V.M. was also hired by CSIC with a postdoctoral contract under the Ramón y Cajal Program. All contracts were cofinanced by the Ministerio de Ciencia e Innovación and the European Social Fund. TEM images were obtained in the SCSIE Microscopy Service of the University of Valencia.

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