Noncoding small RNAs, such as microRNAs, are becoming the biomarkers of choice for multiple diseases in clinical diagnostics. A dysregulation of these microRNAs can be associated with many different diseases, such as cancer, dementia, and cardiovascular conditions. The key for effective treatment is an accurate initial diagnosis at an early stage, improving the patient's survival chances. In this work, the first clustered regularly interspaced short palindromic repeats (CRISPR)/Cas13a‐powered microfluidic, integrated electrochemical biosensor for the on‐site detection of microRNAs is introduced. Through this unique combination, the quantification of the potential tumor markers microRNA miR‐19b and miR‐20a is realized without any nucleic acid amplification. With a readout time of 9 min and an overall process time of less than 4 h, a limit of detection of 10 pm is achieved, using a measuring volume of less than 0.6 µL. Furthermore, the feasibility of the biosensor platform to detect miR‐19b in serum samples of children, suffering from brain cancer, is demonstrated. The validation of the obtained results with a standard quantitative real‐time polymerase chain reaction method shows the ability of the electrochemical CRISPR‐powered system to be a low‐cost, easily scalable, and target amplification‐free tool for nucleic acid based diagnostics.

Heterologous mammalian gene regulation systems for adjustable expression of multiple transgenes are necessary for advanced human gene therapy and tissue engineering, and for sophisticated in vivo gene-function analyses, drug discovery, and biopharmaceutical manufacturing. The antibiotic-dependent interaction between the repressor (E) and operator (ETR) derived from an Escherichia coli erythromycin-resistance regulon was used to design repressible (E(OFF)) and inducible (E(ON)) mammalian gene regulation systems (E.REX) responsive to clinically licensed macrolide antibiotics (erythromycin, clarithromycin, and roxithromycin). The E(OFF) system consists of a chimeric erythromycin-dependent transactivator (ET), constructed by fusing the prokaryotic repressor E to a eukaryotic transactivation domain that binds and activates transcription from ETR-containing synthetic eukaryotic promoters (P(ETR)). Addition of macrolide antibiotic results in repression of transgene expression. The E(ON) system is based on E binding to artificial ETR-derived operators cloned adjacent to constitutive promoters, resulting in repression of transgene expression. In the presence of macrolides, gene expression is induced. Control of transgene expression in primary cells, cell lines, and microencapsulated human cells transplanted into mice was demonstrated using the E.REX (E(OFF) and E(ON)) systems. The macrolide-responsive E.REX technology was functionally compatible with the streptogramin (PIP-regulated and tetracycline (TET-regulated expression systems, and therefore may be combined for multiregulated multigene therapeutic interventions in mammalian cells and tissues.

In multicellular systems cell identity is imprinted by epigenetic regulation circuits, which determine the global transcriptome of adult cells in a cell phenotype-specific manner. By combining two repressors, which control each other's expression, we have developed a mammalian epigenetic circuitry able to switch between two stable transgene expression states after transient administration of two alternate drugs. Engineered Chinese hamster ovary cells (CHO-K1) showed toggle switch-specific expression profiles of a human glycoprotein in culture, as well as after microencapsulation and implantation into mice. Switch dynamics and expression stability could be predicted with mathematical models. Epigenetic transgene control through toggle switches is an important tool for engineering artificial gene networks in mammalian cells.

Synthetic biology aims to create functional devices, systems and organisms with novel and useful functions on the basis of catalogued and standardized biological building blocks. Although they were initially constructed to elucidate the dynamics of simple processes, designed devices now contribute to the understanding of disease mechanisms, provide novel diagnostic tools, enable economic production of therapeutics and allow the design of novel strategies for the treatment of cancer, immune diseases and metabolic disorders, such as diabetes and gout, as well as a range of infectious diseases. In this Review, we cover the impact and potential of synthetic biology for biomedical applications.

Growth and differentiation of multicellular systems is orchestrated by spatially restricted gene expression programs in specialized subpopulations. The targeted manipulation of such processes by synthetic tools with high-spatiotemporal resolution could, therefore, enable a deepened understanding of developmental processes and open new opportunities in tissue engineering. Here, we describe the first red/far-red light-triggered gene switch for mammalian cells for achieving gene expression control in time and space. We show that the system can reversibly be toggled between stable on- and off-states using short light pulses at 660 or 740 nm. Red light-induced gene expression was shown to correlate with the applied photon number and was compatible with different mammalian cell lines, including human primary cells. The light-induced expression kinetics were quantitatively analyzed by a mathematical model. We apply the system for the spatially controlled engineering of angiogenesis in chicken embryos. The system’s performance combined with cell- and tissue-compatible regulating red light will enable unprecedented spatiotemporally controlled molecular interventions in mammalian cells, tissues and organisms.