Rapid Lipid Modification of Endothelial Cell Membranes in Cardiac Ischemia/Reperfusion Injury: a Novel Therapeutic Strategy to Reduce Infarct Size.

PURPOSE: Plasma membranes constitute a gathering point for lipids and signaling proteins. Lipids are known to regulate the location and activity of signaling proteins under physiological and pathophysiological conditions. Membrane lipid therapies (MLTs) that gradually modify lipid content of plasma membranes have been developed to treat chronic disease; however, no MLTs have been developed to treat acute conditions such as reperfusion injury following myocardial infarction (MI) and percutaneous coronary intervention (PCI). A fusogenic nanoliposome (FNL) that rapidly incorporates exogenous unsaturated lipids into endothelial cell (EC) membranes was developed to attenuate reperfusion-induced protein signaling. We hypothesized that administration of intracoronary (IC) FNL-MLT interferes with EC membrane protein signaling, leading to reduced microvascular dysfunction and infarct size (IS). METHODS: Using a myocardial ischemia/reperfusion swine model, the efficacy of FNL-MLT in reducing IS following a 60-min coronary artery occlusion was tested. Animals were randomized to receive IC Ringer's lactate solution with or without 10 mg/mL/min of FNLs for 10 min prior to reperfusion (n = 6 per group). RESULTS: The IC FNL-MLT reduced IS (25.45 ± 16.4% vs. 49.7 ± 14.1%, P < 0.02) and enhanced regional myocardial blood flow (RMBF) in the ischemic zone at 15 min of reperfusion (2.13 ± 1.48 mL/min/g vs. 0.70 ± 0.43 mL/min/g, P < 0.001). The total cumulative plasma levels of the cardiac injury biomarker cardiac troponin I (cTnI) were trending downward but were not significant (999.3 ± 38.7 ng/mL vs. 1456.5 ± 64.8 ng/mL, P = 0.1867). However, plasma levels of heart-specific fatty acid binding protein (hFABP), another injury biomarker, were reduced at 2 h of reperfusion (70.3 ± 38.0 ng/mL vs. 137.3 ± 58.2 ng/mL, P = 0.0115).  CONCLUSION: The IC FNL-MLT reduced IS compared to vehicle in this swine model. The FNL-MLT maybe a promising adjuvant to PCI in the treatment of acute MI.

Gold Nanoparticle-Based Fluorescent Contrast Agent with Enhanced Sensitivity.

Gold nanoparticle (GNP) based contrast agents that are highly specific and sensitive for both optical and X-ray/CT imaging modalities are being developed for detecting the cancer expressing nucleolin and matrix metallo-proteinase 14 (MMP-14) on the cell membrane: Nucleolin is normally present in the nucleus. For many cancer cells, however, it is over-expressed on the cell membrane, having it to be a good cancer marker. Aptamer AS1411 is known to be an excellent target for nucleolin and also known to treat several cancer types; and MMP-14 in cancer is involved in tumor angiogenesis, blood vessel re-organization, and metastasis. In the proposed agent, AS1411 is selected as the cancer targeting molecule; and the unique property of GNPs of modulating fluorescence are utilized to allow the agent to trigger its fluorescence upon reacting with MMP-14, at an enhanced fluorescence level. GNPs are also natural X-ray/CT contrast agent. Here, as a part of on-going development of the dual-modality contrast agent, we report that conjugating a safe, NIR fluorophore Cypate at a precisely determined distance from the GNP enhanced the Cypate fluorescence up to two times. In addition, successful conjugation of the nucleolin target AS1411 onto the GNP was confirmed and among the GNPs size range 5-30 nm tested, 10 nm GNPs showed the highest X-ray/CT enhancement.

MMP-14 Triggered Fluorescence Contrast Agent.

Matrix metalloproteinase-14 (MMP-14) is involved in cancer invasion, metastasis, and angiogenesis. Therefore, it is considered to be a biomarker for aggressive cancer types, including some of the triple-negative breast cancer. Accurate (i.e., specific) and sensitive detection of MMP-14 can, thus, be important for the early diagnosis of and accurate prognosis for aggressive cancer, including the breast cancer caused by cell line MDA-MB 231. Fluorophore-mediated molecular sensing has been used for detecting biomarkers, for a long time. One way to increase the specificity of the sensing is designing the fluorophore to emit its fluorescence only when it encounters the biomarker of interest. When a fluorophore is placed on the surface of, or very close to a gold nanoparticle (GNP), its fluorescence is quenched. Applying this relationship between the GNP and fluorophore, we have developed a GNP-based, near-infrared fluorescent contrast agent that is highly specific for MMP-14. This agent normally emits only 14-17 % fluorescence of the free fluorophore. When the agent encounters MMP-14, its fluorescence gets fully restored, allowing MMP-14 specific optical signal emission.