Protein-nanoparticle co-assembly supraparticles for drug delivery: Ultrahigh drug loading and colloidal stability, and instant and complete lysosomal drug release.

Two frequent problems hindering clinical translation of nanomedicine are low drug loading and low colloidal stability. Previous efforts to achieve ultrahigh drug loading (>30 %) introduce new hurdles, including lower colloidal stability and others, for clinical translation. Herein, we report a new class of drug nano-carriers based on our recent finding in protein-nanoparticle co-assembly supraparticle (PNCAS), with both ultrahigh drug loading (58 % for doxorubicin, i.e., DOX) and ultrahigh colloidal stability (no significant change in hydrodynamic size after one year). We further show that our PNCAS-based drug nano-carrier possesses a built-in environment-responsive drug release feature: once in lysosomes, the loaded drug molecules are released instantly (<1 min) and completely (∼100 %). Our PNCAS-based drug delivery system is spontaneously formed by simple mixing of hydrophobic nanoparticles, albumin and drugs. Several issues related to industrial production are studied. The ultrahigh drug loading and stability of DOX-loaded PNCAS enabled the delivery of an exceptionally high dose of DOX into a mouse model of breast cancer, yielding high efficacy and no observed toxicity. With further developments, our PNCAS-based delivery systems could serve as a platform technology to meet the multiple requirements of clinical translation of nanomedicines.

Mechanism-Driven Technology Development for Solving the Intracellular Delivery Problem of Hard-To-Transfect Cells.

The so-called "hard-to-transfect cells" are well-known to present great challenges to intracellular delivery, but detailed understandings of the delivery behaviors are lacking. Recently, we discovered that vesicle trapping is a likely bottleneck of delivery into a type of hard-to-transfect cells, namely, bone-marrow-derived mesenchymal stem cells (BMSCs). Driven by this insight, herein, we screened various vesicle trapping-reducing methods on BMSCs. Most of these methods failed in BMSCs, although they worked well in HeLa cells. In stark contrast, coating nanoparticles with a specific form of poly(disulfide) (called PDS1) nearly completely circumvented vesicle trapping in BMSCs, by direct cell membrane penetration mediated by thiol-disulfide exchange. Further, in BMSCs, PDS1-coated nanoparticles dramatically enhanced the transfection efficiency of plasmids of fluorescent proteins and substantially improved osteoblastic differentiation. In addition, mechanistic studies suggested that higher cholesterol content in plasma membranes of BMSCs might be a molecular-level reason for the greater difficulty of vesicle escape in BMSCs.

Improving crossing of multiple bio-delivery barriers by a novel bio-interface design based on hydrophobic nanoparticle surfaces.

Biological delivery remains a major challenge in biotechnology, partly because it is often not enough to overcome a single delivery barrier. It is highly desirable, yet rarely available, to design delivery carriers with both simple structures and the ability to cross multiple delivery barriers with high efficiency. Herein, we describe a distinct design (dubbed 'SDot') of delivery carriers with a single structural feature that can enhance the crossing of multiple delivery barriers. The bio-interface (the interface with a biological environment) of an SDot nanoparticle is highly hydrophobic, thus enhancing its interactions with lipid membranes, which are the primary components of many bio-delivery barriers. We used quantum dots (QDs) as the model core material of SDots and conjugated them with a RGD peptide. Thus-formed SDots-RGD demonstrated greatly improved abilities of cellular uptake and transcytosis in a brain tumor cell line, U87MG, compared with the conventional nanoparticle counterpart with a hydrophilic bio-interface (wQDs-RGD). Further, after loading a microtubule-binding anticancer drug, paclitaxel (PTX), onto the nanoparticle surface of SDots-RGD, the resulting drug formulation PTX@SDots-RGD displayed excellent ability of intracellular targeting to microtubules in U87MG cells. In a small animal cancer model, PTX@SDots-RGD exhibited significantly higher ability to slow down brain tumor growth than that of PTX@wQDs-RGD and free PTX. Taken together, these experimental results indicated the significant potential of SDots-RGD for bio-delivery, although the possible long-term toxicity of QDs used as the core material needs to be addressed in future work by replacing QDs with clinically approved materials.

Remote neurostimulation with physical fields at cellular level enabled by nanomaterials: Toward medical applications.

Most neurological diseases have no cure today; innovations in neurotechnology are in urgent need. Nanomaterial-based remote neurostimulation with physical fields (NNSPs) is an emerging class of neurotechnologies that has generated tremendous interest in recent years. This perspective focuses on the clinical translation of this new class of neurotechnologies, an issue that so far has not received enough attention. We outline the major barriers in their clinical translation. We highlight our recent efforts to tackle these translational barriers, with a focus on the biological delivery problem. In particular, for the first time, we have shown that it is feasible to use noninvasive brain delivery to generate significant physiological responses in living animals by NNSP. However, much more work is needed to overcome the translational barriers.