Nanomaterials for non-viral gene delivery
In addition to insufficient delivery efficiency, traditional non-viral vectors, due to bearing a high density of positive charge, often have significant toxicity. Our initial efforts in developing non-viral gene delivery carriers focused on engineering negatively charged nanoparticles (NPs) for enhanced gene material encapsulation, cell penetration, and endosomal escape (Zhou J. et al. Biomaterials, 2012; Ediriwickrema A. et al. Biomaterials, 2014). Although we showed those heavily engineered NPs enabled gene delivery in high efficiency, the complicated nature of those NPs may limit their potential for clinical translation. To simplify the formulation, we synthesized a family of novel terpolymers using enzyme-catalyzed polymerization chemistry. This synthetic approach allows tuning four important parameters in a single molecule: positive charge, molecular weight, hydrophobicity, and solidity. We demonstrated that those polymers, a balance of positive charge, molecular weight, and hydrophobicity, enable gene delivery with high efficiency and minimal toxicity (Zhou J. et al. Nature Materials, 2012; Han L. et al. ACS Nano, 2016). Recently, we further refined the chemistry to synthesized grafted terpolymers, which can form core-shell nanostructure and deliver genes more efficiently than the first generation terpolymer NPs. This surprising discovery may further advance our technology for gene delivery.
We also developed NPs for targeted delivery of CRISPR/Cas9. To maximize gene editing efficiency and reduce off-target effects, we synthesized liposome-templated hydrogel nanoparticles (LHNPs) to co-deliver Cas9 in protein form with sgRNAs. We demonstrated that LHNPs allow delivery of CRISPR/Cas9 in high efficiency to peripheral as well as intracranial tumors (Chen Z. et al.Adv Funct Mater. 2017). Now, we are working on synthesizing novel materials that form single component NPs for CRISPR/Cas9 delivery.
Nanomaterials for oral drug delivery
Due to its convenience and high patient compliance, oral drug delivery remains ideal for most patients. To develop approaches for oral drug delivery, we took an unusual approach to seek nanomaterials in the nature. Through this approach, we have identified a group of small molecules that form supramolecular nanoparticles (SNPs), some of which are capable of efficient drug encapsulation and gastrointestinal (GI) penetration. Inspired by this discovery, we have synthesized a group of novel polymeric materials that are optimal for oral drug delivery. We found that those novel materials enable oral delivery of a range of therapeutics, including protein drugs such as insulin and antibodies, for disease treatment.
Nanotechnology approaches for drug delivery to the brain
Drug delivery to the brain is a major challenge because of the blood-brain barrier (BBB), which limits the penetration of most therapeutics to the brain. Currently, Gliadel wafer is the only drug delivery system approved by the FDA for drug delivery to the brain. Clinically, Gliadel wafer is placed into tumor cavity after tumor resection. However, with this approach, cargo therapeutic agents diffuse only in a few millimeters from the wafers and do not reach distant tumor cells located several centimeters away, which limits its therapeutic benefit. To improve drug distribution and retain the controlled release property, we developed an array of techniques for synthesis of brain-penetrating NPs (BP NPs), fabrication of stepped catheters, and delivery via convection-enhanced delivery (CED). The combination of these advances allows the delivery of NPs over a clinically relevant volume and significantly enhanced the treatment of brain cancer in animal models (Zhou J. et al. PNAS, 2013; Strohbehn G. et al. J Neurooncol. 2015). To enable non-invasive delivery of therapeutics to the brain through intravenous administration, we developed an autocatalytic brain-targeted (ABT) delivery mechanism, which is achieved through surface conjugation of a brain-targeting ligand and internal encapsulation of a BBB modulator. After intravenous administration, a small fraction of NPs enter the brain through ligand-receptor interaction, where NPs locally release the BBB modulator, which in turn enhances BBB permeability to allow additional NPs to enter the brain. As a result, the delivery efficiency autocatalytically increases with time. We validated this mechanism by testing ABT-engineered NPs in mice bearing brain tumors, stroke, or traumatic brain injury (TBI) (Han L. et al. ACS Nano, 2016; Han L. et al. Nanomedicine. 2016; and Chen Z. et al. Adv Funct Mater. 2017).
In addition to synthesizing NPs for drug delivery to the brain, we are also developing approaches to engineering neural stem cells (NSCs) to mediate drug delivery to the brain. Moreover, we have designed and synthesized activatable protein NPs that can be employed for targeted delivery of therapeutic peptides to the brain (Yu X. et al. Advanced Materials, 2018).
Biology of brain cancer stem cells (BCSCs)
I was among the first pioneering group of scientists studying cancer stem cells in solid tumors. My early stage work not only provided substantial evidence about the importance of cancer stem cells in cancer treatment, but also suggested directions in achieving their preferential elimination (Zhou J. et al. PNAS, 2007, Zhou J. et al, BCRT, 2008, Zhou J. et al, BCRT, 2009). We recently processed over 50 human glioblastoma specimens and established an array of BCSC lines. Many of them have been characterized for their molecular signatures and tumorigenicity and pathology in mice. With this resource, we are taking a combinatory approaches to target BCSCs. By now, we have completed a genome-wide screen on selected BCSC lines and validated a few candidate genes that regulate BCSC differentiation (manuscript in submission). We have also completed a large scale drug screen on BCSCs and are currently evaluating lead drug candidates. We plan to validate the molecular targets identified through the genomic and chemical genomic approaches using proteomic approaches (Zhou J. et al. PNAS). When any promising molecular target or drug candidate emerges, we will evaluate it in mouse xenografts by delivering them using those systems described above.