Targeting nanosystems to human DCs via Fc receptor as an effective strategy to deliver antigen for immunotherapy.

Dendritic cells (DCs) are increasingly being explored as cellular vaccines for tumor immunotherapy, since they provide an effective system of antigen presentation both in vitro and in vivo. An additional advantage of this cell type is that it is possible to target specific antigens through the activation of receptors, such as FcR (the receptor for the IgG Fc fragment) and TLR (toll-like Receptor). Thus, the uptake capacity of DCs can be improved, thereby increasing antigen presentation. This, in turn, would lead to an enhanced immune response, and, in some instances, the tolerance/anergy of immune effector cells present in cancer patients could be reverted. Here we studied various nanotargeting systems, including liposomes and gold nanoparticles of a peptide-based immunotherapeutic vaccine for the treatment of androgen-responsive prostate cancer. Building blocks of the immunogenic peptide consisted of the luteinizing hormone-releasing hormone (LHRH), also known as gonadotropin-releasing hormone (GnRH) peptide (B- and T-cell epitope), in tandem with a T-helper epitope corresponding to the 830-844 region of tetanus toxoid. Three new peptides with several modifications at the N-terminal (palmitoyl, acetyl, and FITC) were synthesized. These peptides also contained a Cys as C-terminal residue to facilitate grafting onto gold nanoparticles. To target different antigen formulations to human DCs, the Fc was activated with a cross-linking spacer to generate a free thiol group and thus facilitate conjugation onto gold nanoparticles, liposomes, and peptide. Our results show that gold nanoparticles and liposomes targeted to FcRs of human DCs are effective antigen delivery carriers and induce a strong immune response with respect to nontargeted LHRH-TT-nanoparticle conjugates and a superior response to that of naked antigens. In addition, dual labeling using gold and FITC-peptide allowed DC tracking by flow cytometry as well as transmission electron microscopy. Nanoparticles were observed to show a homogeneous distribution throughout the cytoplasm. These results open up a new approach to the development of a novel strategy for cancer vaccines.

Conjugation of Kahalalide F with gold nanoparticles to enhance in vitro antitumoral activity.

Two Cys-containing analogues of the anticancer drug Kahalalide F are synthesized and conjugated to 20 and 40 nm gold nanoparticles (GNPs). The resulting complexes are characterized by different analytical techniques to confirm the attachment of peptide to the GNPs. The self-assembly capacity of a peptide dramatically influences the final ratio number of molecules per nanoparticle, saturating the nanoparticle surface and prompting multilayered capping on the surface. In such way, the nanoparticle could act as a concentrator for the delivery of drugs, thereby increasing bioactivity. The GNP sizes and the conjugation have influence on the biological activities. Kahalalide F analogues conjugated with GNPs are located subcellularly at lysosome-like bodies, which may be related to the action mechanism of Kahalalide F. The results suggest that the selective delivery and activity of Kahalalide F analogues can be improved by conjugating the peptides to GNPs.

Peptides and metallic nanoparticles for biomedical applications.

In this review, we describe the contribution of peptides to the biomedical applications of metallic nanoparticles. We also discuss strategies for the preparation of peptide-nanoparticle conjugates and the synthesis of the peptides and metallic nanoparticles. An overview of the techniques used for the characterization of the conjugates is also provided. Mainly for biomedical purposes, metallic nanoparticles conjugated to peptides have been prepared from Au and iron oxide (magnetic nanoparticles). Peptides with the capacity to penetrate the plasma membrane are used to deliver nanoparticles to the cell. In addition, peptides that recognize specific cell receptors are used for targeting nanoparticles. The potential application of peptide-nanoparticle conjugates in cancer and Alzheimer's disease therapy is discussed. Several peptide-nanoparticle conjugates show biocompatibility and present a low degree of cytotoxicity. Furthermore, several peptide-metallic nanoparticle conjugates are used for in vitro diagnosis.