Multifaceted ligand design facilitates chemical- or peptide-mediated linking of hollow gold nanoshells with tuned interparticle distance, interference and cytotoxicities

ABSTRACT: We report a versatile methodology to covalently link hollow gold nanoshells (HAuNS) through modular design of multi-tasking ligands and bio-adaptable chemistry. The biocompatible ligand composition includes strategically placed two polyethylene glycol (PEG) chains, protected thiol-terminated tetraethylene glycol, and a reactive functional group, on a core. HAuNS are functionalized through an in situ one-pot deprotection/thiol-Au binding. The ligand-functionalized HAuNS with surface exposed COOH or OH entities are employed in constructing linked-HAuNS conjugated through a short chemical- or a longer bio-spacer (GPLGVRG peptide), in which (i) the length of the PEG chains plays an important role in minimizing oligomerization during covalent linking of HAuNS; (ii) inter-particle distance and interference of HAuNS surface plasmon resonance are regulated through chemical/peptide junctions, with UV-Vis-NIR absorption maxima red-shifted in chem-linked HAuNS; and (iii) chem-linked HAuNS-to-monomer conversion leads to amplification of the photoacoustic signal. Ligand stabilized monomeric and linked-HAuNS are less cytotoxic than citrate protected HAuNS. The synthetic tools and facile chemistry described here provide opportunities in designing linked metal nanoparticles for broad applications in biology

Fabricating water dispersible superparamagnetic iron oxide nanoparticles for biomedical applications through ligand exchange and direct conjugation

Stable superparamagnetic iron oxide nanoparticles (SPIONs), which can be easily dispersed in an aqueous medium and exhibit high magnetic relaxivities, are ideal candidates for biomedical applications including contrast agents for magnetic resonance imaging. We describe a versatile methodology to render water dispersibility to SPIONs using tetraethylene glycol (TEG)-based phosphonate ligands, which are easily introduced onto SPIONs by either a ligand exchange process of surface-anchored oleic-acid (OA) molecules or via direct conjugation. Both protocols confer good colloidal stability to SPIONs at different NaCl concentrations. A detailed characterization of functionalized SPIONs suggests that the ligand exchange method leads to nanoparticles with better magnetic properties but higher toxicity and cell death, than the direct conjugation methodology

Validating intravascular imaging with serial optical coherence tomography and confocal fluorescence microscopy

Atherosclerotic cardiovascular diseases are characterized by the formation of a plaque in the arterial wall. Intravascular ultrasound (IVUS) provides high-resolution images allowing delineation of atherosclerotic plaques. When combined with near infrared fluorescence (NIRF), the plaque can also be studied at a molecular level with a large variety of biomarkers. In this work, we present a system enabling automated volumetric histology imaging of excised aortas that can spatially correlate results with combined IVUS/NIRF imaging of lipid-rich atheroma in cholesterol-fed rabbits. Pullbacks in the rabbit aortas were performed with a dual modality IVUS/NIRF catheter developed by our group. Ex vivo three-dimensional (3D) histology was performed combining optical coherence tomography (OCT) and confocal fluorescence microscopy, providing high-resolution anatomical and molecular information, respectively, to validate in vivo findings. The microscope was combined with a serial slicer allowing for the imaging of the whole vessel automatically. Colocalization of in vivo and ex vivo results is demonstrated. Slices can then be recovered to be tested in conventional histology

Synthetic Methodologies to Gold Nanoshells: An Overview

Gold nanostructures that can be synthetically articulated to adapt diverse morphologies, offer a versatile platform and tunable properties for applications in a variety of areas, including biomedicine and diagnostics. Among several conformational architectures, gold nanoshells provide a highly advantageous combination of properties that can be fine-tuned in designing single or multi-purpose nanomaterials, especially for applications in biology. One of the important parameters for evaluating the efficacy of gold nano-architectures is their reproducible synthesis and surface functionalization with desired moieties. A variety of methods now exist that allow fabrication and chemical manipulation of their structure and resulting properties. This review article provides an overview and a discussion of synthetic methodologies to a diverse range of gold nanoshells, and a brief summary of surface functionalization and characterization methods employed to evaluate their overall composition

Thrombospondin-1-derived peptide RFYVVMWK improves the adhesive phenotype of CD34sup+/sup cells from atherosclerotic patients with type 2 diabetes

International audienceBackground: CD34(+) progenitor cells are growingly used for vascular repair. However, in diabetic individuals with cardiovascular diseases, these cells have dysfunctional engraftment capabilities, which compromise their use for autologous cell therapy. The thrombospondin-1-derived peptide RFYVVMWK has previously been reported to stimulate cell adhesiveness through CD47 and integrin activation pathways.Objectives: Our aim was to test whether RFYVVMWK preconditioning could modulate CD34(+) cells phenotype and enhance its pro-adhesive properties in diabetic patients.Patients/methods: Peripheral blood mononuclear CD34(+) cells isolated from 40 atherosclerotic patients with (T2D; n=20) or without (NonT2D; n=20) type 2 diabetes were pre-conditioned with 30µM of RFYVVMWK (or truncated peptide RFYVVM. CD34(+) cell adhesion was assessed on a vitronectin-collagen matrix and on a TNFα or IL-1β- stimulated HUVEC monolayers. Adhesion receptors, platelet/CD34(+) cell conjugates, and cell viability were analyzed by flow cytometry and confocal microscopy.Results: RFYVVMWK increased by 8 folds the adhesion of T2D CD34(+) cells to the vitronectin-collagen matrix (p Conclusions: Priming CD34(+) cells with RFYVVMWK may enhance their vascular engraftment during autologous pro-angiogenic cell therapy.

Evaluation of links between high-density lipoprotein genetics, functionality, and aortic valve stenosis risk in humans

Objective—Studies have shown that high-density lipoprotein (HDL)–raising compounds induce regression of aortic valve stenosis (AVS) in animal models. However, whether patients with AVS have an impaired HDL metabolism is unknown. Approach and Results—A total of 1435 single nucleotide polymorphisms in genes associated with HDL cholesterol levels (in or around GALNT2, LPL, ABCA1, APOA5, SCARB1, LIPC, CETP, LCAT, LIPG, APOC4, and PLTP) were genotyped in 382 patients with echocardiography-confirmed AVS (aortic jet velocity =2.5 m/s) and 401 controls. After control for multiple testing, none of the genetic variants showed a positive association with case/control status (adjusted P=0.05 for all single nucleotide polymorphisms tested). In a subsample of this cohort, HDL cholesterol levels, apolipoprotein AI levels, lecithin-cholesterol acyltransferase activity, pre–ß-HDL, HDL size, and 4 parameters of cholesterol efflux capacity were measured in apolipoprotein B–depleted serum samples from 86 patients with and 86 patients without AVS. Cholesterol efflux capacity was measured using J774 macrophages with and without stimulation of ATP-binding cassette A-1 expression by cAMP, and HepG2 hepatocytes for scavenger receptor class B type 1–mediated efflux. None of these parameters were different between cases and controls. However, compared with patients without coronary artery disease, sera from patients with coronary artery disease had lower HDL cholesterol levels, scavenger receptor class B type 1–mediated efflux, and HDL size (P=0.003), independently of the presence or absence of AVS. Conclusions—Results of the present study suggest that, based on HDL genetics and HDL functionality, HDL metabolism does not seem to predict the risk of AVS. Because of our limited sample size, additional studies are needed to confirm these findings

Validating Intravascular Imaging with Serial Optical Coherence Tomography and Confocal Fluorescence Microscopy

Atherosclerotic cardiovascular diseases are characterized by the formation of a plaque in the arterial wall. Intravascular ultrasound (IVUS) provides high-resolution images allowing delineation of atherosclerotic plaques. When combined with near infrared fluorescence (NIRF), the plaque can also be studied at a molecular level with a large variety of biomarkers. In this work, we present a system enabling automated volumetric histology imaging of excised aortas that can spatially correlate results with combined IVUS/NIRF imaging of lipid-rich atheroma in cholesterol-fed rabbits. Pullbacks in the rabbit aortas were performed with a dual modality IVUS/NIRF catheter developed by our group. Ex vivo three-dimensional (3D) histology was performed combining optical coherence tomography (OCT) and confocal fluorescence microscopy, providing high-resolution anatomical and molecular information, respectively, to validate in vivo findings. The microscope was combined with a serial slicer allowing for the imaging of the whole vessel automatically. Colocalization of in vivo and ex vivo results is demonstrated. Slices can then be recovered to be tested in conventional histology

In Vivo Near-Infrared Fluorescence Imaging of Atherosclerosis Using Local Delivery of Novel Targeted Molecular Probes

Abstract This study aimed to evaluate the feasibility and accuracy of a technique for atherosclerosis imaging using local delivery of relatively small quantities (0.04–0.4 mg/kg) of labeled-specific imaging tracers targeting ICAM-1 and unpolymerized type I collagen or negative controls in 13 rabbits with atheroma induced by balloon injury in the abdominal aorta and a 12-week high-cholesterol diet. Immediately after local infusion, in vivo intravascular ultrasonography (IVUS)-NIRF imaging was performed at different time-points over a 40-minute period. The in vivo peak NIRF signal was significantly higher in the molecular tracer-injected rabbits than in the control-injected animals (P < 0.05). Ex vivo peak NIRF signal was significantly higher in the ICAM-1 probe-injected rabbits than in controls (P = 0.04), but not in the collagen probe-injected group (P = 0.29). NIRF signal discrimination following dual-probe delivery was also shown to be feasible in a single animal and thus offers the possibility of combining several distinct biological imaging agents in future studies. This innovative imaging strategy using in vivo local delivery of low concentrations of labeled molecular tracers followed by IVUS-NIRF catheter-based imaging holds potential for detection of vulnerable human coronary artery plaques