Directional Immobilization of Proteins on Gold Nanoparticles Is Essential for Their Biological Activity: Leptin as a Case Study.

Gold nanomaterials hold great potential for biomedical applications. While this field is evolving rapidly, little attention has been paid to precise nanoparticle design and functionalization. Here, we show that when using proteins as targeting moieties, it is fundamental to immobilize them directionally to preserve their biological activity. Using full-length leptin as a case study, we have developed two alternative conjugation strategies for protein immobilization based on either a site-selective or a nonselective derivatization approach. We show that only nanoparticles with leptin immobilized site-selectively fully retain the ability to interact with the cognate leptin receptor. These results demonstrate the importance of a specified molecular design when preparing nanoparticles labeled with proteins.

Gold Nanoparticles Functionalized with RGD-Semipeptides: A Simple yet Highly Effective Targeting System for αV ß3 Integrins.

Effective and selective targeting of the αV ß3 integrin subtype is of high relevance in cancer research for the development of therapeutic systems with improved efficacy and of diagnostic imaging probes. We report here a new class of highly selective, αV ß3 -targeted gold nanoparticles (AuNPs), which carry cyclic 4-aminoproline-RGD semipeptides (cAmpRGD) as the targeting moiety immobilized at low surface density on the poly(ethylene glycol) (PEG)-based nanoparticle coating. We show that these nanoparticles are potent inhibitors of the integrin-mediated melanoma tumor cell adhesion to vitronectin and are selectively internalized via receptor-mediated endocytosis. Furthermore, we have developed bifunctional cAmpRGD-functionalized AuNPs by conjugation of a fluorophore (FAM or TAMRA) to a separate set of reactive groups on the PEG-based coating. These bifunctional AuNPs not only recapitulate the binding properties of cAmpRGD-AuNPs but also can be visualized via confocal laser microscopy, allowing direct observation of nanoparticle internalization. The peculiar molecular design of these nanoparticles and their precisely defined architecture at the molecular level accounts for their selective integrin binding with very low nonspecific background.

A new complex of curcumin with sulfobutylether-ß-cyclodextrin: characterization studies and in vitro evaluation of cytotoxic and antioxidant activity on HepG-2 cells.

Curcumin (CR) is a natural polyphenol with antioxidative, anti-inflammatory, and anticancer properties but its therapeutic potential is substantially hindered by the rather low-water solubility and bioavailability. Thus, in this work, a new soluble inclusion complex of CR with sulfobutylether-ß-cyclodextrin (SBE-ß-CD) was prepared in solution and at the solid state using different preparation techniques and characterized by Fourier transform infrared, nuclear magnetic resonance, differential scanning calorimetry, scanning electron microscopy, phase solubility studies, and Job's plot method. Results clearly indicate that CR reacts with SBE-ß-CD to form a host-guest complex with an apparent formation constant of 1455 M(-1) . Moreover, SBE-ß-CD strongly increases water solubility of CR (from 0.56 to 102.78 µg/mL, at 25°C), and lyophilization method seems to be the best preparation technique to obtain the complex at the solid state. Finally, an in vitro test on a human hepatic cancer cell line (HepG-2) shows that complexation positively influences CR anticancer and antioxidant activity.