Ultrastructural Characteristics of Myocardial Reperfusion Injury and Effect of Selective Intracoronary Hypothermia: An Observational Study in Isolated Beating Porcine Hearts.

In acute myocardial infarction (AMI), myocardial reperfusion injury may undo part of the recovery after revascularization of the occluded coronary artery. Selective intracoronary hypothermia is a novel method aimed at reducing myocardial reperfusion injury, but its presumed protective effects in AMI still await further elucidation. This proof-of-concept study assesses the potential protective effects of selective intracoronary hypothermia in an ex-vivo, isolated beating heart model of AMI. In four isolated Langendorff perfused beating pig hearts, an anterior wall myocardial infarction was created by inflating a balloon in the mid segment of the left anterior descending (LAD) artery. After one hour, two hearts were treated with selective intracoronary hypothermia followed by normal reperfusion (cooled hearts). In the other two hearts, the balloon was deflated after one hour, allowing normal reperfusion (control hearts). Biopsies for histologic and electron microscopic evaluation were taken from the myocardium at risk at different time points: before occlusion (t = BO); 5 minutes before reperfusion (t = BR); and 10 minutes after reperfusion (t = AR). Electron microscopic analysis was performed to evaluate the condition of the mitochondria. Histological analyses included evaluation of sarcomeric collapse and intramyocardial hematoma. Electron microscopic analysis revealed intact mitochondria in the hypothermia treated hearts compared to the control hearts where mitochondria were more frequently damaged. No differences in the prespecified histological parameters were observed between cooled and control hearts at t = AR. In the isolated beating porcine heart model of AMI, reperfusion was associated with additional myocardial injury beyond ischemic injury. Selective intracoronary hypothermia preserved mitochondrial integrity compared to nontreated controls.

Programmable Bivalent Peptide-DNA Locks for pH-Based Control of Antibody Activity.

The ability to control antibody activity by pH has important applications in diagnostics, therapeutic antibody targeting, and antibody-guided imaging. Here, we report the rational design of bivalent peptide-DNA ligands that allow pH-dependent control of antibody activity. Our strategy uses a pH-responsive DNA triple helix to control switching from a tight-binding bivalent peptide-DNA lock into a weaker-binding monovalent ligand. Different designs are introduced that allow antibody activation at both basic and acidic pHs, either autonomously or in the presence of an additional oligonucleotide trigger. The pH of antibody activation could be precisely tuned by changing the DNA triple helix sequence. The peptide-DNA locks allowed pH-dependent antibody targeting of tumor cells both in bulk and for single cells confined in water-in-oil microdroplets. The latter approach enables high-throughput antibody-mediated detection of single tumor cells based on their distinctive metabolic activity.