###### Abstract  
In this work, nanoboib hybrids of plasmonic gold nanoparticles (AuNP, anti-angiogenic) and a peptide mimicking the vascular endothelial growth factor (VEGF, pro-angiogenic) were assembled and scrutinized in terms of physicochemical characterization, including optical properties, surface charge, surface chemical structure and morphology of the bioengineered metal nanoparticles, for their potential application as multifunctional theranostic (i.e., therapy + sensing) nanoplatform (AuNP/VEGF). Specifically, a peptide sequence encompassing the VEGF cellular receptor domain 73-101 (VEGF3-101) and its single point cysteine mutated were immobilized onto AuNP by physi- and chemi-sorption, respectively. The new hybrid systems were characterized by means of a multitechnique approach, including dynamic light scattering (DLS) analyses, zeta potential (ZP), spectroscopic (UV-Vis, FT-IR, XPS), spectrometric (TOF-SIMS) and microscopic (AFM, SEM) techniques. Proof-of-work cellular experiments in human umbilical vein endothelial cells (HUVEC) upon the treatment with AuNP/VEGF samples, demonstrated no toxicity up to 24 h (MTT assay) as well an effective internalization (laser confocal microscopy, LSM). plasmonics; thermostatics; TOF-SIMS; XPS; FT-IR; TEM; DLS; zeta potential; HUVEC, theranostics +
Footnote †: journal: Applied Sciences  
Four isoforms of VEGF-A, having 121, 165, 189, and 206 amino acids, are produced from a single gene because of alternate splicing [8; 9]. The most abundantly expressed splice variant is VEGF165, a heparin binding glycoprotein cleaved by plasmin to yield VEGF110, which is equipotent to VEGF121 with respect to mitogenic activity on endothelial cells [10]. The 121 amino acid form of VEGF induces the proliferation of endothelial cells but, in contrast to VEGF165, lacks the heparin binding ability. Only a small number of VEGF residues are important for the binding to VEGF receptors. Particularly, the positively charged domain of VEGF encompassing Arg82, Lys84 and His86, located in a hairpin loop, and a negatively charged residues Asp63, Glu64 and Glu67 resulted responsible for the respectively binding of VEGFR-1 and VEGFR-2 receptors [11], and then for the angiogenic response [12]. Different antiangiogenic approaches have been developed to block the interaction of VEGFs with their receptors to inhibit angiogenesis and tumour growth. Small molecules and peptides have been synthesized as agonist or antagonist agents for potential application in many pathologies [13]. It is to note that many VEGF mimetic peptides with antiangiogenic activity have been described [14], while very few molecules with pro-angiogenic activity have been reported [15]. A relevant issue in the application of anti- or pro-angiogenic molecules is the large amount that generally has to be administered, which could determine unspecific binding, side effects and toxicity [16]. To overcome these shortcomings, nanoparticles (NPs) have been utilized to delivery angiogenic modulators. An advantage is the requirement for low doses due to increased reactivity that derives from the large concentration of active molecules confined in the small volume of NPs [16]. In addition to acting as a delivery system, NPs can protect molecules and in particular peptides from degradation due to enzymatic action. Furthermore, NPs display pro- or anti-angiogenic properties based on their nature [17; 18]. Different sizes and surface charges influenced the intracellular signalling events. Particularly, gold and silver nanoparticles seemed to inhibit the function of pro-angiogenic heparin-binding growth factors (HB-GFs), such as VEGF165 and basic fibroblast growth factor (bFGF) [19; 20; 21]. VEGF121, which do not have a heparin binding domain, was not inactivated by gold nanoparticles, so AuNP selectively inhibited VEGF165-induced proliferation of HUVECs cells [23]. Gold NPs may act as an effective inhibitor of VEGF-induced choroid-retina endothelial cells migration without affecting cells viability and their adhesion to fibronectin [24].