Gold nanorods (NR) and asymmetric nanoparticles (ANP) capped with a biocompatible polymer bearing binding groups for molecules and metal cations: pharmacological and thermal antimicrobial action activated by near-IR irradiationNanorods (NR) e nanoparticelle asimmnetriche (NPA) d'oro ricoperte di polimero biocompatibile con funzioni leganti per molecole e ioni metallici: aziona antimicrobica farmacologica e termica attivata da irraggiamento nel vicino IR.

Progetto: Research project

Dettagli progetto

Description

The project will be realized in the follorwing steps: i) We will prepare gold NR and ANP with convenient shape, capable of absorbing in the NIR interval; ii) Gold NR e ANP must be stabilized against in-vivo aggregation and must be biocompatible. To this aim we will cover them with multifunctional poly(hydroxyethylaspartamide) (PHEA) polymers. These polymers, known for their bicompatibility, can be prepared with a versatile functionalization/purification step-by-step procedure, to obtain PHEA backbones bearing a tunable number of different functions. We plan to append polyethyleneglycol (PEG) chains, n-alkyl thiols and ligands for Mn+ and/or receptors for antibiotics. The –SH terminated alkyl chains will serve as anchoring point to gold nano-objects, the long hydrophilic PEG polymers will impart solubility and bicompatibility, the binding functions will allow the upload of antimicrobial metal cations and molecules. We plan to obtain a hyerarchical disposition: a core made of gold nanoobjects, an internal hydrophobic layer made by n-alkyl chains on the PHEA backbone, where alsobinding units are positioned, and an external hydrophilic PEG layer; iii) The binding functions that we will append to PHEA will be mainly chelating polyamines, aza-crown ethers, pyridines or combinations of the three. These ligands exothermalally interact with Ag+ and Cu2+, and the decrease of stability with increasing T (ΔT) will switch on their release. We will bind in the polymer layer antiobiotics such as Ampicillin, Vancomycin, Cyprofloxacin (bearing –COOH groups), or Gentamycin, Kanamycin, Neomycin (bearing several –NH2 groups), by appending to PHEA coordinatively unsaturated and kinetically inert metal complexes (like Cu2+ or Zn2+ complexes with small tetraazamacrocycles), that offer one or more free sites on the metal for carboxylate and amine coordination. Moreover, we will exploit less specific multipoint interactions for antibiotics, such as H-bond and electrostatic carboxylate/protonated amine interactions, and hydrophobic interactions (for the less hydrophilic antibiotics, interacting with the hydrophobic layer around the NR and ANP); iv) The ΔT by photoirradiation will be induced using NIR laser. v) We will measure the uptake and ΔT-induced release of Ag+, Cu2+ and antibiotics by means of an arsenal of separation, analytical, spectroscopic, imaging, and optical techniques, merging the know-hows of the chemical, physical-optical and biophysical components of the research team; vi) At every stage of the research, we will check the biocompatibility of our products with cell viability and cyotoxicity tests, and their anti-bacterial activity with in-vitro tests on several bacterial strains, including MDR. The rationale is that without light irradiation the studied nano-objects are ineffective against bacteria and not cytotoxic. Uncovered NR and ANP, the same covered with simple polymer (no binding functions), the same covered with polymers bearing binding functions and finally charged with Mn+ and antibiotics will be checked with and without light irradiation. We want to understand the separate contribution of heat, metal cations and antibiotics to bactericidal effect, as we plan to fine tuning the combination of the three to obtain maximum efficiency. We will also study the internalization and diffusion in the cell of NR and ANP by means of by means of fluorescence imaging and dynamic spectroscopy (including Fluorescence Recovery after Photobleaching, FRAP), and correlate the chemical features of the nano-objects, their shape and their antibacterial ef

Layman's description

Multidrug-resistant (MDR) bacterial strains are an important and increasing medical problem. They are often associated with wound infections but also with septic arthritis, osteomyelitis, endocarditis, i.e. deseases localized in deep tissues. Moreover, conventional antimicrobial therapies are often complicated by the in-vivo growth modalities of bacteria, forming organized, resistant communities (biofilms) e.g. on the surface of internalized devices such as catheters or prostheses. Conscious of the need of new, more efficient tools to solve the MDR problem, we reasoned that: i) the antimicrobial action of Ag+ (and to a minor extent of Cu2+) is used since centuries; ii) the photo-activated thermal action of gold nano-objects is an established phenomenon, intensely studied in the last 15 years for its potential anti-cancer activity. A recent interest has raised also for its use against bacteria where it seems a very promising tool although still far to be developed; iii) it has been shown by few recent papers that an enhanced antimicrobial effetc is observed by coupled pharmacological and thermal action with gold nano-objects carrying absorbed antibiotics; iv) almost 150 years of coordination chemistry and 30 years of supramolecular chemistry have shown how a temperature increase (ΔT) can be exploited to weaken the exothermal metal-ligand and substrate-receptor interactions (beside inducing an obviuos acceleration of the kinetics of any process).On these basis we choose the goal of obtaining polymer-coated gold NR and branched ANP, capable of absorbing radiation in the NearInfraRed (NIR, 750-1200 nm), and to exploit the consequent heat release both to exert a direct thermal antimicrobial action and to control the release of antimicrobial metal cations and/or antibiotics. The choice of NR and ANP instead of conventional spherical nanoparticles is due to the valued possibility of using NIR irradiation, as in this wavelength interval cell tissues and blood are quasi-transparent, so that a use of our products may be foreseen also for deep-positioned MDR infections. To fulfill our goal we have programmed these points:i) We will prepare gold NR and ANP with convenient shape, capable of absorbing in the NIR interval. Syntheses in aqueous solution will be adapted from literature for NR, while for ANP we will rely on the method originally elaborated in our labs; ii) Gold NR e ANP must be stabilized against in-vivo aggregation and must be biocompatible. To this aim we will cover them with multifunctional poly(hydroxyethylaspartamide) (PHEA) polymers. These polymers, known for their bicompatibility, can be prepared with a versatile functionalization/purification step-by-step procedure, to obtain PHEA backbones bearing a tunable number of different functions. We plan to append polyethyleneglycol (PEG) chains, n-alkyl thiols and ligands for Mn+ and/or receptors for antibiotics. The –SH terminated alkyl chains will serve as anchoring point to gold nano-objects, the long hydrophilic PEG polymers will impart solubility and bicompatibility, the binding functions will allow the upload of antimicrobial metal cations and molecules. We plan to obtain a hyerarchical disposition: a core made of gold nanoobjects, an internal hydrophobic layer made by n-alkyl chains on the PHEA backbone, where alsobinding units are positioned, and an external hydrophilic PEG layer; iii) The binding functions that we will append to PHEA will be mainly chelating polyamines, aza-crown ethers, pyridines or combinations of the three. These ligands exothermalally interact with Ag+ an
StatoAttivo
Data di inizio/fine effettiva1/1/11 → …