Construction and heterologous expression of the di-AFN A biosynthetic gene cluster in Streptomyces model strains.

Natural cyclohexapeptide AFN A fromStreptomyces alboflavus 313 has moderate antibacterial and antitumor activities. An artificial designed AFN A homodimer, di-AFN A, is an antibiotic exhibiting 10 to 150 fold higher biological activities, compared with the monomer. Unfortunately, the yield of di-AFN A is very low (0.

Novel switchable ECF sigma factor transcription system for improving thaxtomin A production in .

The application of the valuable natural product thaxtomin A, a potent bioherbicide from the potato scab pathogenic strains, has been greatly hindered by the low yields from its native producers. Here, we developed an orthogonal transcription system, leveraging extra-cytoplasmic function (ECF) sigma (σ) factor 17 (ECF17) and its cognate promoter P, to express the thaxtomin gene cluster and improve the production of thaxtomin A. The minimal P promoter was determined, and a P promoter library with a wide range of strengths was constructed.

Multiplexed Promoter Engineering for Improving Thaxtomin A Production in Heterologous Hosts.

Thaxtomin A is a potent bioherbicide in both organic and conventional agriculture; however, its low yield hinders its wide application. Here, we report the direct cloning and heterologous expression of the thaxtomin A gene cluster in three well-characterized hosts. Then, we present an efficient, markerless and multiplex large gene cluster editing method based on in vitro CRISPR/Cas9 digestion and yeast homologous recombination.

Synthetic robust perfect adaptation achieved by negative feedback coupling with linear weak positive feedback.

Unlike their natural counterparts, synthetic genetic circuits are usually fragile in the face of environmental perturbations and genetic mutations. Several theoretical robust genetic circuits have been designed, but their performance under real-world conditions has not yet been carefully evaluated. Here, we designed and synthesized a new robust perfect adaptation circuit composed of two-node negative feedback coupling with linear positive feedback on the buffer node.

A tight cold-inducible switch built by coupling thermosensitive transcriptional and proteolytic regulatory parts.

Natural organisms have evolved intricate regulatory mechanisms that sense and respond to fluctuating environmental temperatures in a heat- or cold-inducible fashion. Unlike dominant heat-inducible switches, very few cold-inducible genetic switches are available in either natural or engineered systems. Moreover, the available cold-inducible switches still have many shortcomings, including high leaky gene expression, small dynamic range (<10-fold) or broad transition temperature (>10°C).

pH and redox dual responsive carrier-free anticancer drug nanoparticles for targeted delivery and synergistic therapy.

Advanced drug delivery systems often employ nanomaterials as carriers to deliver drugs to desirable disease sites for enhanced efficacy. However, most systems have low drug loading capacity and cause safety concerns. Therefore, many anticancer therapeutics have recently been assembled to NPs form without using any additional nanocarrier to achieve high drug loading.

Paired Design of dCas9 as a Systematic Platform for the Detection of Featured Nucleic Acid Sequences in Pathogenic Strains.

We developed an in vitro DNA detection system using a pair of dCas9 proteins linked to split halves of luciferase. Luminescence was induced upon colocalization of the reporter pair to a ∼44 bp target sequence defined by sgRNAs. We used the system to detect Mycobacterium tuberculosis DNA with high specificity and sensitivity.

Real-time imaging and tracking of ultrastable organic dye nanoparticles in living cells.

Semiconductor quantum dots and upconversion nanoparticles have been broadly used for live cell imaging due to their color tunability and photostability etc. However, these inorganic materials often contain heavy metals and potentially have metabolism problems. To overcome these issues, herein, we report a type of organic dye nanoparticles (NPs) with coating of a thin silica layer and folic acid targeting molecules on the surface for live cell imaging.

Smart surface coating of drug nanoparticles with cross-linkable polyethylene glycol for bio-responsive and highly efficient drug delivery.

Many drug molecules can be directly used as nanomedicine without the requirement of any inorganic or organic carriers such as silica and liposome nanostructures. This new type of carrier-free drug nanoparticles (NPs) has great potential in clinical treatment because of its ultra-high drug loading capacity and biodegradability. For practical applications, it is essential for such nanomedicine to possess robust stability and minimal premature release of therapeutic molecules during circulation in the blood stream.

Smart doxorubicin nanoparticles with high drug payload for enhanced chemotherapy against drug resistance and cancer diagnosis.

Considering the obvious advantages in efficacy and price, doxorubicin (DOX) has been widely used for a range of cancers, which is usually encapsulated in various nanocarriers for drug delivery. Although effective, in most nanocarrier-based delivery systems, the drug loading capacity of DOX is rather low; this can lead to undesired systemic toxicity and excretion concern. Herein, we report for the first time the usage of pure doxorubicin nanoparticles (DOX NPs) without addition of any carriers for enhanced chemotherapy against drug-resistance.