Spermine Oxidase-Substrate Electrostatic Interactions: The Modulation of Enzyme Function by Neighboring Colloidal ɣ-Fe2O3.

Protein-nanoparticle hybridization can ideally lead to novel biological entities characterized by emerging properties that can sensibly differ from those of the parent components. Herein, the effect of ionic strength on the biological functions of recombinant His-tagged spermine oxidase (i.e., SMOX) was studied for the first time. Moreover, SMOX was integrated into colloidal surface active maghemite nanoparticles (SAMNs) via direct self-assembly, leading to a biologically active nano-enzyme (i.e., SAMN@SMOX). The hybrid was subjected to an in-depth chemical-physical characterization, highlighting the fact that the protein structure was perfectly preserved. The catalytic activity of the nanostructured hybrid (SAMN@SMOX) was assessed by extracting the kinetics parameters using spermine as a substrate and compared to the soluble enzyme as a function of ionic strength. The results revealed that the catalytic function was dominated by electrostatic interactions and that they were drastically modified upon hybridization with colloidal ɣ-Fe2O3. The fact that the affinity of SMOX toward spermine was significantly higher for the nanohybrid at low salinity is noteworthy. The present study supports the vision of using protein-nanoparticle conjugation as a means to modulate biological functions.

Thiol functionalised gold nanoparticles loaded with methotrexate for cancer treatment: From synthesis to in vitro studies on neuroblastoma cell lines.

HYPOTHESIS: Colloidal gold nanoparticles (AuNPs) functionalised with hydrophilic thiols can be used as drug delivery probes, thanks to their small size and hydrophilic character. AuNPs possess unique properties for their use in nanomedicine, especially in cancer treatment, as diagnostics and therapeutic tools. EXPERIMENTS: Thiol functionalised AuNPs were synthesised and loaded with methotrexate (MTX). Spectroscopic and morphostructural characterisations evidenced the stability of the colloids upon interaction with MTX. Solid state (GISAXS, GIWAXS, FESEM, TEM, FTIR-ATR, XPS) and dispersed phase (UV-Vis, DLS, ζ-potential, NMR, SAXS) experiments allowed to understand structure-properties correlations. The nanoconjugate was tested in vitro (MTT assays) against two neuroblastoma cell lines: SNJKP and IMR5 with overexpressed n-Myc. FINDINGS: Molar drug encapsulation efficiency was optimised to be >70%. A non-covalent interaction between the π system and the carboxylate moiety belonging to MTX and the charged aminic group of one of the thiols was found. The MTX loading slightly decreased the structural order of the system and increased the distance between the AuNPs. Free AuNPs showed no cytotoxicity whereas the AuNPs-MTX nanoconjugate had a more potent effect when compared to free MTX. The active role of AuNPs was evidenced by permeation studies: an improvement on penetration of the drug inside cells was evidenced.

Acidic Shift of Optimum pH of Bovine Serum Amine Oxidase upon Immobilization onto Nanostructured Ferric Tannates.

Protein-nanoparticle hybrids represent entities characterized by emerging biological properties that can significantly differ from those of the parent components. Herein, bovine serum amine oxidase (i.e., BSAO) was immobilized onto a magnetic nanomaterial constituted of surface active maghemite nanoparticles (i.e., SAMNs, the core), surface-modified with tannic acid (i.e., TA, the shell), to produce a biologically active ternary hybrid (i.e., SAMN@TA@BSAO). In comparison with the native enzyme, the secondary structure of the immobilized BSAO responded to pH variations sensitively, resulting in a shift of its optimum activity from pH 7.2 to 5.0. Conversely, the native enzyme structure was not influenced by pH and its activity was affected at pH 5.0, i.e., in correspondence with the best performances of SAMN@TA@BSAO. Thus, an extensive NMR study was dedicated to the structure-function relationship of native BSAO, confirming that its low activity below pH 6.0 was ascribable to minimal structural modifications not detected by circular dichroism. The generation of cytotoxic products, such as aldehydes and H2O2, by the catalytic activity of SAMN@TA@BSAO on polyamine oxidation is envisaged as smart nanotherapy for tumor cells. The present study supports protein-nanoparticle conjugation as a key for the modulation of biological functions.

Bovine Serum Amine Oxidase and Polyamine Analogues: Chemical Synthesis and Biological Evaluation Integrated with Molecular Docking and 3-D QSAR Studies.

Natural polyamines (PAs) are key players in cellular homeostasis by regulating cell growth and proliferation. Several observations highlight that PAs are also implicated in pathways regulating cell death. Indeed, the PA accumulation cytotoxic effect, maximized with the use of bovine serum amine oxidase (BSAO) enzyme, represents a valuable strategy against tumor progression. In the present study, along with the design, synthesis, and biological evaluation of a series of new spermine (Spm) analogues (1-23), a mixed structure-based (SB) and ligand-based (LB) protocol was applied. Binding modes of BSAO-PA modeled complexes led to clarify electrostatic and steric features likely affecting the BSAO-PA biochemical kinetics. LB and SB three-dimensional quantitative structure-activity relationship (Py-CoMFA and Py-ComBinE) models were developed by means of the 3d-qsar.com portal, and their analysis represents a strong basis for future design and synthesis of PA BSAO substrates for potential application in oxidative stress-induced chemotherapy.