Juan C. Frias

Detecting and assessing macrophages in vivo to evaluate atherosclerosis noninvasively using molecular MRI.

We investigated the ability of targeted immunomicelles to detect and assess macrophages in atherosclerotic plaque using MRI in vivo. There is a large clinical need for a noninvasive tool to assess atherosclerosis from a molecular and cellular standpoint. Macrophages play a central role in atherosclerosis and are associated with plaques vulnerable to rupture. Therefore, macrophage scavenger receptor (MSR) was chosen as a target for molecular MRI. MSR-targeted immunomicelles, micelles, and gadolinium–diethyltriaminepentaacetic acid (DTPA) were tested in ApoE−/− and WT mice by using in vivo MRI. Confocal laser-scanning microscopy colocalization, macrophage immunostaining and MRI correlation, competitive inhibition, and various other analyses were performed. In vivo MRI revealed that at 24 h postinjection, immunomicelles provided a 79% increase in signal intensity of atherosclerotic aortas in ApoE−/− mice compared with only 34% using untargeted micelles and no enhancement using gadolinium–DTPA. Confocal laser-scanning microscopy revealed colocalization between fluorescent immunomicelles and macrophages in plaques. There was a strong correlation between macrophage content in atherosclerotic plaques and the matched in vivo MRI results as measured by the percent normalized enhancement ratio. Monoclonal antibodies to MSR were able to significantly hinder immunomicelles from providing contrast enhancement of atherosclerotic vessels in vivo. Immunomicelles provided excellent validated in vivo enhancement of atherosclerotic plaques. The enhancement seen is related to the macrophage content of the atherosclerotic vessel areas imaged. Immunomicelles may aid in the detection of high macrophage content associated with plaques vulnerable to rupture.

MRI to detect atherosclerosis with gadolinium-containing immunomicelles targeting the macrophage scavenger receptor.

The ability to specifically image macrophages may enable improved detection and characterization of atherosclerosis. In this study we evaluated the in vitro uptake of gadolinium (Gd)‐containing immunomicelles (micelles linked to macrophage‐specific antibody), micelles, and standard contrast agents by murine macrophages, and sought to determine whether immunomicelles and micelles improve ex vivo imaging of apolipoprotein E knockout (ApoE KO) murine atherosclerosis. Murine RAW 264.7 macrophages were incubated with Gd‐DTPA, micelles, and immunomicelles. Cell pellets were prepared and imaged using a 1.5 T MR system with an inversion recovery spin‐echo sequence to determine the in vitro T1 values. Ex vivo analysis of mouse aortas was performed using a 9.4T MR system with a high‐spatial‐resolution sequence (78 × 39 × 78 μm3). The T1 value was significantly decreased in cells treated with micelles compared to Gd‐DTPA (P < 0.0001), and in cells incubated at 4°C with immunomicelles compared to micelles (P < 0.05). Ex vivo MRI signal intensity (SI) was significantly increased by 81% and 20% in aortas incubated with immunomicelles and micelles, respectively. Confocal microscopy demonstrated in vitro and ex vivo uptake of fluorescent immunomicelles by macrophages. Immunomicelles and micelles improve in vitro and ex vivo MR detection of macrophages, and may prove useful in the detection of macrophage‐rich plaques. Magn Reson Med, 2006.

Molecular imaging of macrophages in atherosclerotic plaques using bimodal PEG-micelles

Pegylated, fluorescent, and paramagnetic micelles were developed. The micelles were conjugated with macrophage scavenger receptor (MSR)‐specific antibodies. The abdominal aortas of atherosclerotic apoE‐KO mice were imaged with T1‐weighted high‐resolution MRI before and 24 h after intravenous administration of the contrast agent (CA). Pronounced signal enhancement (SE) (up to 200%) was observed for apolipoprotein E knockout (apoE‐KO) mice that were injected with MSR‐targeted micelles, while the aortic vessel wall of mice injected with nontargeted micelles showed little SE. To allow fluorescence microscopy and optical imaging of the excised aorta, the micelles were made fluorescent by incorporating either a quantum dot (QD) in the micelle corona or rhodamine lipids in the micelle. Ultraviolet (UV) illumination of the aorta allowed the identification of regions with high macrophage content, while MSR‐targeted rhodamine micelles could be detected with fluorescence microscopy and were found to be associated with macrophages. In conclusion, this study demonstrates that macrophages in apoE‐KO mice can be effectively and specifically detected by molecular MRI and optical methods upon administration of a pegylated micellar CA. Magn Reson Med 58:1164–1170, 2007.

Supramolecular complexation for environmental control

Supramolecular complexes offer a new and efficient way for the monitoring and removal of many substances emanating from technical processes, fertilization, plant and animal protection, or e.g. chemotherapy. Such pollutants range from toxic or radioactive metal ions and anions to chemical side products, herbicides, pesticides to drugs including steroids, and include degradation products from natural sources. The applications involve usually fast and reversible complex formation, due to prevailing non-covalent interactions. This is of importance for sensing as well as for separation techniques, where the often expensive host compounds can then be reused almost indefinitely. Immobilization of host compounds, e.g. on exchange resins or on membranes, and their implementation in smart new materials hold particular promise. The review illustrates how the design of suitable host compounds in combination with modern sensing and separation methods can contribute to solve some of the biggest problems facing chemistry, which arise from the everyday increasing pollution of the environment.

Macrophage-specific lipid-based nanoparticles improve cardiac magnetic resonance detection and characterization of human atherosclerosis.

OBJECTIVES We sought to determine whether gadolinium (Gd)-containing lipid-based nanoparticles (NPs) targeting the macrophage scavenger receptor-B (CD36) improve cardiac magnetic resonance (CMR) detection and characterization of human atherosclerosis. BACKGROUND Gd-containing lipid-based NPs targeting macrophages have improved MR detection of murine atherosclerosis. METHODS Gadolinium-containing untargeted NPs, anti-CD36 NPs, and nonspecific Fc-NPs were created. Macrophages were incubated with fluorescent targeted and nontargeted NPs to determine uptake via confocal microscopy and inductively coupled plasma mass spectroscopy (ICP-MS) quantified Gd uptake. Human aortic specimens were harvested at autopsy. With a 1.5-T scanner, T1, T2, and PDW 3-dimensional scans were performed along with post-contrast scans after 24 h incubation. The T1 and cluster analyses were performed and compared with immunohistopathology. RESULTS The NPs had a mean diameter of 125 nm and 14,900 Gd-ions, and relaxivity was 37 mmol/l(-1)s(-1) at 1.5-T and 37 degrees C. Confocal microscopy and ICP-MS demonstrated significant in vitro macrophage uptake of targeted NPs, whereas non-targeted NPs had minimal uptake. On T1 imaging, targeted NPs increased contrast-to-noise ratio (CNR) by 52.5%, which was significantly greater than Fc-NPs (CNR increased 17.2%) and nontargeted NPs (CNR increased 18.7%) (p = 0.001). Confocal fluorescent microscopy showed that NPs target resident macrophages, whereas the untargeted NPs and Fc-NPs are found diffusely throughout the plaque. Targeted NPs had a greater signal intensity increase in the fibrous cap compared with non-targeted NPs. CONCLUSIONS Macrophage-specific (CD36) NPs bind human macrophages and improve CMR detection and characterization of human aortic atherosclerosis. Thus, macrophage-specific NPs could help identify high-risk human plaque before the development of an atherothrombotic event.

Modulation of DNA binding by reversible metal-controlled molecular reorganizations of scorpiand-like ligands.

DNA interaction with scorpiand azamacrocycles has been achieved through modulation of their binding affinities. Studies performed with different experimental techniques provided evidence that pH or metal-driven molecular reorganizations of these ligands regulate their ability to interact with calf thymus DNA (ctDNA) through an intercalative mode. Interestingly enough, metal-driven molecular reorganizations serve to increase or decrease the biological activities of these compounds significantly.

HDL as a contrast agent for medical imaging

Abstract Contrast-enhanced MRI of atherosclerosis can provide valuable additional information on a patient’s disease state. As a result of the interactions of HDL with atherosclerotic plaque and the flexibility of its reconstitution, it is a versatile candidate for the delivery of contrast-generating materials to this pathogenic lesion. We herein discuss the reports of HDL modified with gadolinium to act as an MRI contrast agent for atherosclerosis. Furthermore, HDL has been modified with fluorophores and nanocrystals, allowing it to act as a contrast agent for fluorescent imaging techniques and for computed tomography. Such modified HDL has been found to be macrophage specific, and, therefore, can provide macrophage density information via noninvasive MRI. As such, modified HDL is currently a valuable contrast agent for probing preclinical atherosclerosis. Future developments may allow the application of this particle to further diseases and pathological or physiological processes in both preclinical models as well as in patients.

Intravenously Delivered Mesenchymal Stem Cells

Rationale: Virtually all mesenchymal stem cell (MSC) studies assume that therapeutic effects accrue from local myocardial effects of engrafted MSCs. Because few intravenously administered MSCs engraft in the myocardium, studies have mainly utilized direct myocardial delivery. We adopted a different paradigm. Objective: To test whether intravenously administered MSCs reduce left ventricular (LV) dysfunction both post–acute myocardial infarction and in ischemic cardiomyopathy and that these effects are caused, at least partly, by systemic anti-inflammatory activities. Methods and Results: Mice underwent 45 minutes of left anterior descending artery occlusion. Human MSCs, grown chronically at 5% O2, were administered intravenously. LV function was assessed by serial echocardiography, 2,3,5-triphenyltetrazolium chloride staining determined infarct size, and fluorescence-activated cell sorting assessed cell composition. Fluorescent and radiolabeled MSCs (1×106) were injected 24 hours post–myocardial infarction and homed to regions of myocardial injury; however, the myocardium contained only a small proportion of total MSCs. Mice received 2×106 MSCs or saline intravenously 24 hours post–myocardial infarction (n=16 per group). At day 21, we harvested blood and spleens for fluorescence-activated cell sorting and hearts for 2,3,5-triphenyltetrazolium chloride staining. Adverse LV remodeling and deteriorating LV ejection fraction occurred in control mice with large infarcts (≥25% LV). Intravenous MSCs eliminated the progressive deterioration in LV end-diastolic volume and LV end-systolic volume. MSCs significantly decreased natural killer cells in the heart and spleen and neutrophils in the heart. Specific natural killer cell depletion 24 hours pre–acute myocardial infarction significantly improved infarct size, LV ejection fraction, and adverse LV remodeling, changes associated with decreased neutrophils in the heart. In an ischemic cardiomyopathy model, mice 4 weeks post–myocardial infarction were randomized to tail-vein injection of 2×106 MSCs, with injection repeated at week 3 (n=16) versus PBS control (n=16). MSCs significantly increased LV ejection fraction and decreased LV end-systolic volume. Conclusions: Intravenously administered MSCs for acute myocardial infarction attenuate the progressive deterioration in LV function and adverse remodeling in mice with large infarcts, and in ischemic cardiomyopathy, they improve LV function, effects apparently modulated in part by systemic anti-inflammatory activities.

Diazatetraester 1H-pyrazole crowns as fluorescent chemosensors for AMPH, METH, MDMA (ecstasy), and dopamine.

The synthesis and steady-state fluorescence studies on the interaction with AMPH, METH, MDMA, and DA of two diazatetraester pyrazole crowns containing appended N-(9H-fluoren-9-yl) and N-(naphth-2-ylmethyl) functions, in a water/ethanol 70:30 mixture at physiological pH, are described.

Crystalline self-assembly induced by aromatic edge-to-face interactions: the crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide

The crystal structure of 2,6,6,10-tetrabenzyl-2,10-diaza-6-azonia[11]paracyclophane bromide reveals several intermolecular aromatic edge-to-face interactions which are important in the three-dimensional growing of the crystalline structure. Molecular dynamics and semiempirical studies indicate that the conformer found in the crystal is not the most stable in solution confirming the important role that edge-to-face interactions play in the structural arrangement found in the solid state.