Minimizing cytosol dilution in whole-cell patch-clamp experiments

Repeated and On-Demand Intracellular Recordings of Cardiomyocytes Derived from Human-Induced Pluripotent Stem Cells

Pharmaceutical compounds may have cardiotoxic properties, triggering potentially life-threatening arrhythmias. To investigate proarrhythmic effects of drugs, the patch clamp technique has been used as the gold standard for characterizing the electrophysiology of cardiomyocytes in vitro. However, the applicability of this technology for drug screening is limited, as it is complex to use and features low throughput. Recent studies have demonstrated that 3D-nanostructured electrodes enable to obtain intracellular signals from many cardiomyocytes in parallel; however, the tedious electrode fabrication and limited measurement duration still remain major issues for cardiotoxicity testing. Here, we demonstrate how porous Pt-black electrodes, arranged in high-density microelectrode arrays, can be used to record intracellular-like signals of cardiomyocytes at large scale repeatedly over an extended period of time. The developed technique, which yields highly parallelized electroporations using stimulation voltages around 1 V peak-to-peak amplitude, enabled intracellular-like recordings at high success rates without causing significant alteration in key electrophysiological features. In a proof-of-concept study, we investigated electrophysiological modulations induced by two clinically applied drugs, nifedipine and quinidine. As the obtained results were in good agreement with previously published data, we are confident that the developed technique has the potential to be routinely used in in vitro platforms for cardiotoxicity screening.

Multiparametric ultrasound and micro-ultrasound in prostate cancer: a comprehensive review

Prostate cancer (PCa) is the most common non-cutaneous cancer diagnosed in males. Traditional tools for screening and diagnosis, such as prostate-specific antigen, digital rectal examination and conventional transrectal ultrasound (TRUS), present low accuracy for PCa detection. Multiparametric MRI has become a game changer in the PCa diagnosis pathway and MRI-targeted biopsies are currently recommended for males at risk of clinically significant PCa, even in biopsy-naïve patients. Recent advances in ultrasound have also emerged with the goal to provide a readily accessible and cost-effective tool for detection of PCa. These newer techniques include elastography and contrast-enhanced ultrasound, as well as improved B-mode and Doppler techniques. These modalities can be combined to define a novel ultrasound approach, multiparametric ultrasound. High frequency Micro-ultrasound has emerged as a promising imaging technology for PCa diagnosis. Initial results have shown high sensitivity of Micro-ultrasound in detecting PCa in addition to its potential in improving the accuracy of targeted biopsies, based on targeting under real-time visualization, rather than relying on cognitive/fusion software MRI-transrectal ultrasound-guided biopsy.

The role of potassium and host calcium signaling in Toxoplasma gondii egress

Toxoplasma gondii is an obligate intracellular parasite and replicates inside a parasitophorous vacuole (PV) within the host cell. The membrane of the PV (PVM) contains pores that permits for equilibration of ions and small molecules between the host cytosol and the PV lumen. Ca²⁺ signaling is universal and both T. gondii and its mammalian host cell utilize Ca²⁺ signals to stimulate diverse cellular functions. Egress of T. gondii from host cells is an essential step for the infection cycle of T. gondii, and a cytosolic Ca²⁺ increase initiates a Ca²⁺ signaling cascade that culminates in the stimulation of motility and egress. In this work we demonstrate that intracellular T. gondii tachyzoites are able to take up Ca²⁺ from the host cytoplasm during host cell signaling events. Both intracellular and extracellular Ca²⁺ sources are important in reaching a threshold of parasite cytosolic Ca²⁺ needed for successful egress. Two peaks of Ca²⁺ were observed in egressing single parasites with the second peak resulting from Ca²⁺ entry. We patched infected host cells to allow the delivery of precise concentrations of Ca²⁺ for the stimulation of motility and egress. Using this approach of patching infected host cells, allowed us to determine that increasing the host cytosolic Ca²⁺ to a specific concentration can trigger egress, which is further accelerated by diminishing the concentration of potassium (K⁺).

Synthetic Monopartite Peptide That Enables the Nuclear Import of Genes Delivered by the Neurotensin-Polyplex Vector

Neurotensin (NTS)-polyplex is a multicomponent nonviral vector that enables gene delivery via internalization of the neurotensin type 1 receptor (NTSR1) to dopaminergic neurons and cancer cells. An approach to improving its therapeutic safety is replacing the viral karyophilic component (peptide KPSV40; MAPTKRKGSCPGAAPNKPK), which performs the nuclear import activity, by a shorter synthetic peptide (KPRa; KMAPKKRK). We explored this issue and the mechanism of plasmid DNA translocation through the expression of the green fluorescent protein or red fluorescent protein fused with KPRa and internalization assays and whole-cell patch-clamp configuration experiments in a single cell together with importin α/β pathway blockers. We showed that KPRa electrostatically bound to plasmid DNA increased the transgene expression compared with KPSV40 and enabled nuclear translocation of KPRa-fused red fluorescent proteins and plasmid DNA. Such translocation was blocked with ivermectin or mifepristone, suggesting importin α/β pathway mediation. KPRa also enabled NTS-polyplex-mediated expression of reporter or physiological genes such as human mesencephalic-derived neurotrophic factor (hMANF) in dopaminergic neurons in vivo. KPRa is a synthetic monopartite peptide that showed nuclear import activity in NTS-polyplex vector-mediated gene delivery. KPRa could also improve the transfection of other nonviral vectors used in gene therapy.