Abdominal twitches due to ICD lead dislodgement; A case report.

Malfunctions of implantable cardiac devices have the potential to be catastrophic. A 63-year-old patient was admitted to our emergency department with new-onset abdominal pain and sensation of twitching on his abdominal wall. One month ago, an implantable cardioverter-defibrillator (ICD) was implanted in him to prevent malignant ventricular arrhythmias. An electrocardiogram was obtained that showed pace spikes unrelated to QRS complexes. The patient was diagnosed with ICD lead dislodgement and the lead was repositioned in another procedure. In conclusion, emergency physicians should be familiar with the problems of implantable cardiac devices.

In Vivo Targeting Using Arylboronate/Nopoldiol Click Conjugation.

Bioorthogonal click reactions yielding stable and irreversible adducts are in high demand for in vivo applications, including in biomolecular labeling, diagnostic imaging, and drug delivery. Previously, we reported a novel bioorthogonal "click" reaction based on the coupling of ortho-acetyl arylboronates and thiosemicarbazide-functionalized nopoldiol. We now report that a detailed structural analysis of the arylboronate/nopoldiol adduct by X-ray crystallography and 11B NMR reveals that the bioorthogonal reactants form, unexpectedly, a tetracyclic adduct through the cyclization of the distal nitrogen into the semithiocarbazone leading to a strong B-N dative bond and two new 5-membered rings. The cyclization adduct, which protects the boronate unit against hydrolytic breakdown, sheds light on the irreversible nature of this polycondensation. The potential of this reaction to work in a live animal setting was studied through in vivo capture of fluorescently labeled molecules in vivo. Arylboronates were introduced into tissues through intradermal injection of their activated NHS esters, which react with amines in the extracellular matrix. Fluorescently labeled nopoldiol molecules were administered systemically and were efficiently captured by the arylboronic acids in a location-specific manner. Taken together, these in vivo proof-of-concept studies establish arylboronate/nopoldiol bioorthogonal chemistry as a candidate for wide array of applications in chemical biology and drug delivery.

Boronic Acids as Bioorthogonal Probes for Site-Selective Labeling of Proteins.

Over the past two decades, bioorthogonal chemistry has become a preferred tool to achieve site-selective modifications of proteins. However, there are only a handful of commonly applied bioorthogonal reactions and they display some limitations, such as slow rates, use of unstable or cytotoxic reagents, and side reactions. Hence, there is significant interest in expanding the bioorthogonal chemistry toolbox. In this regard, boronic acids have recently been introduced in bioorthogonal chemistry and are exploited in three different strategies: 1) boronic ester formation between a boronic acid and a 1,2-cis diol; 2) iminoboronate formation between 2-acetyl/formyl-arylboronic acids and hydrazine/hydroxylamine/semicarbazide derivatives; 3) use of boronic acids as transient groups in a Suzuki-Miyaura cross-coupling or other reactions that leave the boronyl group off the conjugation product. In this Review, we summarize progress made in the use of boronic acids in bioorthogonal chemistry to enable site-selective labeling of proteins and compare these methods with the most commonly utilized bioorthogonal reactions.

Synergic "Click" Boronate/Thiosemicarbazone System for Fast and Irreversible Bioorthogonal Conjugation in Live Cells.

Fast, high-yielding, and selective bioorthogonal "click" reactions employing nontoxic reagents are in high demand for their great utility in the conjugation of biomolecules in live cells. Although a number of click reactions were developed for this purpose, many are associated with drawbacks and limitations that justify the development of alternative systems for both single- or dual-labeling applications. Recent reports have highlighted the potential of boronic ester formation as a bioorthogonal click reaction between abiotic boronic acids and diols. Boronic ester formation is a fast dehydrative process; however it is intrinsically reversible in aqueous medium. We designed and optimized a synergic system based on two bifunctional reagents, a thiosemicarbazide-functionalized nopoldiol and an ortho-acetyl arylboronic acid. Both reagents were shown to be chemically stable and nontoxic to HEK293T cells at concentrations as high as 50 µM. The resulting boronate/thiosemicarbazone adduct is a medium-sized ring that forms rapidly and irreversibly without any catalyst at low µM concentrations, in neutral buffer, with a rate constant of 9 M-1 s-1 as measured by NMR spectroscopy. Control experiments in the presence of competing boronic acids showed no crossover side-products and confirmed the stability and lack of reversibility of the boronate/thiosemicarbazone conjugates. Formation of the conjugates is not affected by the presence of biological diols such as fructose, glucose, and catechol, and the thiosemicarbazide-functionalized nopoldiol is inert to aldehyde electrophiles of the sort found on protein-bound glyoxylyl units. The suitability of this system in the cell-surface labeling of live cells was demonstrated using a SNAP-tag approach to install the boronic acid reagent onto the extracellular domain of the Beta-2 adrenergic receptor in HEK293T cells, followed by incubation with the optimal thiosemicarbazide-functionalized nopoldiol reagent labeled with fluorescein dye. Successful visualization by fluorescence microscopy was possible with a reagent concentration as low as 10 µM, thus confirming the potential of this system in biological applications.

Fast and Tight Boronate Formation for Click Bioorthogonal Conjugation.

A new click bioorthogonal reaction system was devised to enable the fast ligation (k(ON) ≈340 m(-1) s(-1)) of conjugatable derivatives of a rigid cyclic diol (nopoldiol) and a carefully optimized boronic acid partner, 2-methyl-5-carboxymethylphenylboronic acid. Using NMR and fluorescence spectroscopy studies, the corresponding boronates were found to form reversibly within minutes at low micromolar concentration in water, providing submicromolar equilibrium constant (K(eq) ≈10(5) -10(6) m(-1)). Efficient protein conjugation under physiological conditions was demonstrated with model proteins thioredoxin and albumin, and characterized by mass spectrometry and gel electrophoresis.