RESEARCH ARTICLE Copyright © 2011 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 11, 1–5, 2011 Toward Preserving the Structure of the Antigenic Peptide p17-1 from the HIV-1 p17 Protein in Nanostructured Films Laís Petri, Marystela Ferreira, and Marli L. Moraes ∗ Universidade Federal de São Carlos, campus de Sorocaba, 18052-780, Sorocaba, SP, Brazil Antigenic peptides may be immobilized in nanostructured films in order to build highly specific immunosensors and other devices that require molecular recognition, with no need to use complex molecules. A major challenge for such endeavors, however, is to preserve the secondary structure of the peptides after immobilization. In this study, we show that the peptide p17-1 (LSGGELDR- WEKIRLRPGG), derived from the HIV-1 p17 protein, may be immobilized in Layer-by-Layer (LbL) films made with polyelectrolytes. Its structure was preserved only if incorporated into phospholipid liposomes, according to fluorescence and circular dichroism (CD) spectroscopy. The lack of sec- ondary structure for the peptide in the LbL film may be associated with the film-forming procedure in which p17-1 was adsorbed from an aqueous solution, where it does not form alpha helices. The importance of structure preservation was clear in the attempts to produce electrochemical immunosensors with the p17-1 peptide without being protected in liposomes in an LbL film. There was no detectable influence of the presence of anti-p17 antibodies, though some molecular inter- action could be inferred from the voltammograms. In contrast, for p17-1 incorporated in liposomes electrochemical immunosensors could be obtained with the voltamogramms showing strong molec- ular recognition with the antibodies. These results indicated that phospholipids serve as a suitable matrix for immobilization of peptides, and confirmed the importance of structure preservation in electrochemical immunosensors. Keywords: 1. INTRODUCTION The human immunodeficiency virus (HIV) has been a problem for decades. According to recent surveys, there are ca. 33.3 million people infected, with 2.6 million new HIV infections in 2009. 1 In order to determine the rate of new infections and provide an adequate therapy, selective diagnostics are required such as the PCR (Poly- merase Chain Reaction) based detection 2 3 or those tests based on detection of antibodies 3 as the Western blotting 4 and enzyme-linked immunosorbent assays (ELISAs). 3 5 6 These methods are considered the most important to detect the HIV antibody. However, new strategies have been reported for the rapid diagnostics of HIV, which are sensitive, cheap, robust, and simple to use. 7 Sapsford et al. investigated a colorimetric/fluorescent sensing for the detection of HIV-1 specific antibodies. The interac- tion between peptide of the HIV-1 p17 protein and anti- p17 antibody resulted in an increase in dye absorption ∗ Author to whom correspondence should be addressed. and fluorescent emission, with a limit of detection about 73 pM. This study demonstrated that a sensor could poten- tially be produced for rapid detection requiring minimal equipment and reagents. Peptide sequences corresponding to well-defined regions of a protein have been shown to possess specific func- tions such as promoting membrane fusion, changing the bilayer curvature and generating immunoresponse, among others. 8–15 Antigenic peptides are a sequence of amino acids (epitopes) of an antigen which are able to recognize specific antibodies. 16 These peptides can be determined by mapping epitopes 17 and be prepared with high purity via chemical synthesis. 18 Synthetic peptides are advanta- geous not only for being safer than using a virus, but also due to the higher operational stability, being uniform and chemically well-defined. 16 The sequence and structure of amino acids in a peptide are crucial to identify spe- cific recognition sites of antigenic proteins that may indeed mimic the natural peptides from p17. 19 This structural con- formation depends on the solvent or the medium where J. Nanosci. Nanotechnol. 2011, Vol. 11, No. xx 1533-4880/2011/11/001/005 doi:10.1166/jnn.2011.4216 1