Ischemic stroke, a major cause of mortality in the United States, often contributes to disruption of the blood-brain barrier (BBB). The BBB along with its supportive cells, collectively referred to as the “neurovascular unit,” is the brain’s multicellular microvasculature that bi-directionally regulates the transport of blood, ions, oxygen, and cells from the circulation into the brain. It is thus vital for the maintenance of central nervous system homeostasis. BBB disruption, which is associated with the altered expression of tight junction proteins and BBB transporters, is believed to exacerbate brain injury caused by ischemic stroke and limits the therapeutic potential of current clinical therapies, such as recombinant tissue plasminogen activator. Accumulating evidence suggests that endothelial mechanobiology, the conversion of mechanical forces into biochemical signals, helps regulate function of the peripheral vasculature and may similarly maintain BBB integrity. For example, the endothelial glycocalyx (GCX), a glycoprotein-proteoglycan layer extending into the lumen of bloods vessel, is abundantly expressed on endothelial cells of the BBB and has been shown to regulate BBB permeability. In this review, we will focus on our understanding of the mechanisms underlying BBB damage after ischemic stroke, highlighting current and potential future novel pharmacological strategies for BBB protection and recovery. Finally, we will address the current knowledge of endothelial mechanotransduction in BBB maintenance, specifically focusing on a potential role of the endothelial GCX.

Early detection of viruses can prevent the uncontrolled spread of viral infections. Determination of viral infectivity is also critical for determining the dosage of gene therapies, including vector-based vaccines, CAR T-cell therapies, and CRISPR therapeutics. In both cases, for viral pathogens and viral vector delivery vehicles, fast and accurate measurement of infectious titer is desirable. The most common methods for virus detection are antigen-based (rapid but not sensitive) and reverse transcription polymerase chain reaction (RT-PCR)-based (sensitive but not rapid). Current viral titer methods heavily rely on cultured cells, which introduces variability within labs and between labs. Thus, it is highly desirable to directly determine the infectious titer without using cells. Here, we report the development of a direct, fast, and sensitive assay for virus detection (dubbed rapid-aptamer FISH or raptamer FISH) and cell-free determination of infectious titers. Importantly, we demonstrate that the virions captured are infectious, thus serving as a more consistent proxy of infectious titer. This assay is unique because it first captures viruses bearing an intact coat protein using an aptamer, then detects genomes directly in individual virions using fluorescence in situ hybridization (FISH) thus, it is selective for infectious particles (i.e., positive for coat protein and positive for genome).

Early detection of viruses can prevent the uncontrolled spread of viral infections. Determination of viral infectivity is also critical for determining the dosage of gene therapies, including vector-based vaccines, CAR T-cell therapies, and CRISPR therapeutics. In both cases, for viral pathogens and viral vector delivery vehicles, fast and accurate measurement of infectious titers is desirable. The most common methods for virus detection are antigen-based (rapid but not sensitive) and polymerase chain reaction (PCR)-based (sensitive but not rapid). Current viral titration methods heavily rely on cultured cells, which introduces variability within labs and between labs. Thus, it is highly desirable to directly determine the infectious titer without using cells. Here, we report the development of a direct, fast, and sensitive assay for virus detection (dubbed rapid capture fluorescence in situ hybridization (FISH) or rapture FISH) and cell-free determination of infectious titers. Importantly, we demonstrate that the virions captured are “infectious,” thus serving as a more consistent proxy of infectious titers. This assay is unique because it first captures viruses bearing an intact coat protein using an aptamer and then detects genomes directly in individual virions using fluorescence in situ hybridization (FISH); thus, it is selective for infectious particles (i.e., positive for coat proteins and positive for genomes).

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Of the various conjugation strategies for cellular biomolecules, Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is the preferred click chemistry approach due to its fast reaction rate and the commercial availability of a wide range of conjugates. While extracellular labeling of biomolecules using CuAAC has been widely adopted, intracellular labeling in live cells has been challenging; the high copper concentration required for CuAAC reaction can be toxic to biological systems. As a critical first step towards achieving intracellular labeling with CuAAC, an ultrasensitive CuAAC ligand is needed to reduce the required copper concentration while maintaining fast reaction kinetics. Here, we develop a new DNA oligomer-conjugated CuAAC ligand for click reaction biomolecular labeling. The DNA oligo attachment serves several purposes: 1. Increases availability of local copper atoms in proximity to the ligand, which drives up reaction rates, 2. Enables the ligation of azide tags with up to 10-fold lower copper concentrations as compared to commercially available CuAAC ligands, 3. Allows nucleic acid template-driven proximity ligation through the choice of the attached DNA sequence and 4. Allows the CuAAC ligand and copper to traverse the cell and nuclear membrane. We demonstrate that this ligand enhances the intracellular 5-ethynyl uridine labeling of nascent RNAs using fluorogenic dyes. We also show that our DNA-enhanced CuAAC ligand enables the ligation of fluorogenic dyes to label both sialylated glycans on the surface on live cells as well as the live-cell intracellular labeling of nascent RNAs. This new ligand advances our efforts toward the final goal of applying CuAAC for live-cell applications.