Person:

Lo, Justin H.

Tumor-targeted delivery of siRNA remains a major barrier in fully realizing the therapeutic potential of RNA interference. While cell-penetrating peptides (CPP) are promising siRNA carrier candidates, they are universal internalizers that lack cell-type specificity. Herein, we design and screen a library of tandem tumor-targeting and cell-penetrating peptides that condense siRNA into stable nanocomplexes for cell type-specific siRNA delivery. Through physiochemical and biological characterization, we identify a subset of the nanocomplex library of that are taken up by cells via endocytosis, trigger endosomal escape and unpacking of the carrier, and ultimately deliver siRNA to the cytosol in a receptor-specific fashion. To better understand the structure–activity relationships that govern receptor-specific siRNA delivery, we employ computational regression analysis and identify a set of key convergent structural properties, namely the valence of the targeting ligand and the charge of the peptide, that help transform ubiquitously internalizing cell-penetrating peptides into cell type-specific siRNA delivery systems.

Antithrombotic therapy is a critical portion of the treatment regime for a number of life-threatening conditions, including cardiovascular disease, stroke, and cancer; yet, proper clinical management of anticoagulation remains a challenge because existing agents increase the propensity for bleeding in patients. Here, we describe the development of a bioresponsive peptide–polysaccharide nanocomplex that utilizes a negative feedback mechanism to self-titrate the release of anticoagulant in response to varying levels of coagulation activity. This nanoscale self-titrating activatable therapeutic, or nanoSTAT, consists of a cationic thrombin-cleavable peptide and heparin, an anionic polysaccharide and widely used clinical anticoagulant. Under nonthrombotic conditions, nanoSTATs circulate inactively, neither releasing anticoagulant nor significantly prolonging bleeding time. However, in response to life-threatening pulmonary embolism, nanoSTATs locally release their drug payload and prevent thrombosis. This autonomous negative feedback regulator may improve antithrombotic therapy by increasing the therapeutic window and decreasing the bleeding risk of anticoagulants.

Chronic lower respiratory disease afflicts over 5% of the United States population, leading to over 145,000 deaths annually. There remains a need for safer and more durable alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, though harnessing their potential depends on efficient and biocompatible design. Incorporating biomimetic materials into such devices can help replicate efficient native gas exchange function and additionally support cellular components. In this work, we developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in membrane remodeling, reflected by reductions in membrane thickness. Functionally, these collagen-membrane lung devices in the acellular configuration mediated effective gas exchange up to rates of ~288 mL/min/m^2 O2 transfer and ~685 mL/min/m^2 CO2 transfer, approaching the gas exchange efficiency measured in the native lung. After testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects were relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate – limited primarily by shear forces experienced by blood components. Finally, collagen-membrane devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions.