Programmable RNA targeting with the single-protein CRISPR effector Cas7-11.

CRISPR-Cas interference is mediated by Cas effector nucleases that are either components of multisubunit complexes-in class 1 CRISPR-Cas systems-or domains of a single protein-in class 2 systems1-3. Here we show that the subtype III-E effector Cas7-11 is a single-protein effector in the class 1 CRISPR-Cas systems originating from the fusion of a putative Cas11 domain and multiple Cas7 subunits that are derived from subtype III-D. Cas7-11 from Desulfonema ishimotonii (DiCas7-11), when expressed in Escherichia coli, has substantial RNA interference effectivity against mRNAs and bacteriophages. Similar to many class 2 effectors-and unique among class 1 systems-DiCas7-11 processes pre-CRISPR RNA into mature CRISPR RNA (crRNA) and cleaves RNA at positions defined by the target:spacer duplex, without detectable non-specific activity. We engineered Cas7-11 for RNA knockdown and editing in mammalian cells. We show that Cas7-11 has no effects on cell viability, whereas other RNA-targeting tools (such as short hairpin RNAs and Cas13) show substantial cell toxicity4,5. This study illustrates the evolution of a single-protein effector from multisubunit class 1 effector complexes, expanding our understanding of the diversity of CRISPR systems. Cas7-11 provides the basis for new programmable RNA-targeting tools that are free of collateral activity and cell toxicity.

Silk Fibroin-Based Coatings for Pancreatin-Dependent Drug Delivery.

Triggerable coatings, such as pH-responsive polymethacrylate copolymers, can be used to protect the active pharmaceutical ingredients contained within oral solid dosage forms from the acidic gastric environment and to facilitate drug delivery directly to the intestine. However, gastrointestinal pH can be highly variable, which can reduce delivery efficiency when using pH-responsive drug delivery technologies. We hypothesized that biomaterials susceptible to proteolysis could be used in combination with other triggerable polymers to develop novel enteric coatings. Bioinformatic analysis suggested that silk fibroin is selectively degradable by enzymes in the small intestine, including chymotrypsin, but resilient to gastric pepsin. Based on the analysis, we developed a silk fibroin-polymethacrylate copolymer coating for oral dosage forms. In vitro and in vivo studies demonstrated that capsules coated with this novel silk fibroin formulation enable pancreatin-dependent drug release. We believe that this novel formulation and extensions thereof have the potential to produce more effective and personalized oral drug delivery systems for vulnerable populations including patients that have impaired and highly variable intestinal physiology.

Computationally guided high-throughput design of self-assembling drug nanoparticles.

Nanoformulations of therapeutic drugs are transforming our ability to effectively deliver and treat a myriad of conditions. Often, however, they are complex to produce and exhibit low drug loading, except for nanoparticles formed via co-assembly of drugs and small molecular dyes, which display drug-loading capacities of up to 95%. There is currently no understanding of which of the millions of small-molecule combinations can result in the formation of these nanoparticles. Here we report the integration of machine learning with high-throughput experimentation to enable the rapid and large-scale identification of such nanoformulations. We identified 100 self-assembling drug nanoparticles from 2.1 million pairings, each including one of 788 candidate drugs and one of 2,686 approved excipients. We further characterized two nanoparticles, sorafenib-glycyrrhizin and terbinafine-taurocholic acid both ex vivo and in vivo. We anticipate that our platform can accelerate the development of safer and more efficacious nanoformulations with high drug-loading capacities for a wide range of therapeutics.