Cellular Computational Logic Using Toehold Switches.

The development of computational logic that carries programmable and predictable features is one of the key requirements for next-generation synthetic biological devices. Despite considerable progress, the construction of synthetic biological arithmetic logic units presents numerous challenges. In this paper, utilizing the unique advantages of RNA molecules in building complex logic circuits in the cellular environment, we demonstrate the RNA-only bitwise logical operation of XOR gates and basic arithmetic operations, including a half adder, a half subtractor, and a Feynman gate, in Escherichia coli. Specifically, de-novo-designed riboregulators, known as toehold switches, were concatenated to enhance the functionality of an OR gate, and a previously utilized antisense RNA strategy was further optimized to construct orthogonal NIMPLY gates. These optimized synthetic logic gates were able to be seamlessly integrated to achieve final arithmetic operations on small molecule inputs in cells. Toehold-switch-based ribocomputing devices may provide a fundamental basis for synthetic RNA-based arithmetic logic units or higher-order systems in cells.

Detection of pks Island mRNAs Using Toehold Sensors in Escherichia coli.

Synthetic biologists have applied biomolecular engineering approaches toward the goal of novel biological devices and have shown progress in diverse areas of medicine and biotechnology. Especially promising is the application of synthetic biological devices towards a novel class of molecular diagnostics. As an example, a de-novo-designed riboregulator called toehold switch, with its programmability and compatibility with field-deployable devices showed promising in vitro applications for viral RNA detection such as Zika and Corona viruses. However, the in vivo application of high-performance RNA sensors remains challenging due to the secondary structure of long mRNA species. Here, we introduced 'Helper RNAs' that can enhance the functionality of toehold switch sensors by mitigating the effect of secondary structures around a target site. By employing the helper RNAs, previously reported mCherry mRNA sensor showed improved fold-changes in vivo. To further generalize the Helper RNA approaches, we employed automatic design pipeline for toehold sensors that target the essential genes within the pks island, an important target of biomedical research in connection with colorectal cancer. The toehold switch sensors showed fold-changes upon the expression of full-length mRNAs that apparently depended sensitively on the identity of the gene as well as the predicted local structure within the target region of the mRNA. Still, the helper RNAs could improve the performance of toehold switch sensors in many instances, with up to 10-fold improvement over no helper cases. These results suggest that the helper RNA approaches can further assist the design of functional RNA devices in vivo with the aid of the streamlined automatic design software developed here. Further, our solutions for screening and stabilizing single-stranded region of mRNA may find use in other in vivo mRNA-sensing applications such as cas13 crRNA design, transcriptome engineering, and trans-cleaving ribozymes.

Cell-Free Synthetic Biology Platform for Engineering Synthetic Biological Circuits and Systems.

Synthetic biology brings engineering disciplines to create novel biological systems for biomedical and technological applications. The substantial growth of the synthetic biology field in the past decade is poised to transform biotechnology and medicine. To streamline design processes and facilitate debugging of complex synthetic circuits, cell-free synthetic biology approaches has reached broad research communities both in academia and industry. By recapitulating gene expression systems in vitro, cell-free expression systems offer flexibility to explore beyond the confines of living cells and allow networking of synthetic and natural systems. Here, we review the capabilities of the current cell-free platforms, focusing on nucleic acid-based molecular programs and circuit construction. We survey the recent developments including cell-free transcription-translation platforms, DNA nanostructures and circuits, and novel classes of riboregulators. The links to mathematical models and the prospects of cell-free synthetic biology platforms will also be discussed.

Pseudoaneurysm of uterine artery causing intra-abdominal and vaginal bleeding after cervical conization.

Uterine arterial pseudoaneurysm is a very rare condition usually associated with postpartum hemorrhage. It almost never occurs after cervical conization; however, since ruptured pseudoaneurysm could be life threatening, we should consider the possibility of vascular injury such as pseudoaneurysm when we find a patient with vaginal bleeding after the process of surgical operation. Emergency arterial embolization is a well established therapeutic option to control the ruptured pseudoaneurysm. This is a case report of uterine arterial pseudoaneurysm causing intra-abdominal bleeding followed by cervical conization, which was successfully treated by uterine artery embolization.

Risk factors for complications in patients undergoing myomectomy at the time of cesarean section.

AIM: The aim of this study was to evaluate the risk factors for complications of myomectomy at cesarean section (CS). METHODS: The subjects were a non-complicated group (n = 100) and a complicated group (n = 10) of patients aged between 20 and 43 years who underwent CS and simultaneous myomectomy at our institution from January 2006 until December 2008. Complications were defined as blood transfusion greater than three packed red blood cells, postoperative ileus, and two days longer than average hospitalization. RESULTS: The complicated group (n = 10) had (i) a myoma larger than 10 cm and no secondary change; and (ii) intramural myoma type. CONCLUSION: Myomectomy during CS can be performed in selected cases, but some patients had significant complications like ileus and postoperative atonic bleeding.