Three-Dimensional Nanocomposites: Fluidics Driven Assembly of Metal Nanoparticles on Protein Nanostructures and Their Cell-Line-Dependent Intracellular Trafficking Pattern

Engineering biomolecular systems: Controlling the self-assembly of gelatin to form ultra-small bioactive nanomaterials

The size of nanocarriers determines the biological property of the materials, especially as it relates to intratumoral distribution. Previous research has shown that sizes of 10–50 nm penetrate deep inside the tumor, resulting in better efficacy. On the other hand, studies have shown that gelatin exhibits excellent biological properties, including compatibility, degradability, and toxicity. Therefore, FDA approved gelatin as a safe material to use as an excipient in injectables. The bottleneck is the nonexistence of smaller-sized gelatin nanoparticles (GNPs) to realize the full potential of these biomaterials. Yet, GNPs with sizes of less than 50 nm have not been reported; the synthetic strategy reported in the literature uses “uncontrolled crosslinking coupled with nanoprecipitation”, resulting in larger particle size. We have developed a new method to self-assemble gelatin strands by using an anionic, phosphate-based crosslinker and controlled precipitation. The method we developed produced ultra-small gelatin nanoparticles (G^X) of size 10 nm with a high degree of reproducibility, and it was characterized using dynamic light scattering (DLS), Energy-dispersive X-ray spectroscopy (EDS), High-resolution transmission, and scanning electron microscopy (HR-TEM/STEM). We also explored G^X as a bioactive platform to encapsulate imaging and therapy agents within the cavity. Interestingly, we were able to encapsulate 2 nm size gold nanoparticles within the void of G^X. The versatile nature of the G^X particles was further demonstrated by surface functionalizing with larger size gelatin nanoparticles to form core-satellite nanocomposites. Additionally, we studied the tumor penetrability of dye-tagged 10, 50, and 200 nm gelatin nanoparticles. The study showed that smaller size gelatin nanoparticles penetrate deeper tumor regions than larger particles. In general, G^X was efficient in penetrating the inner region of the spheroids. The results demonstrate the potential capabilities of ultra-small G^X nanoparticles for multi-staged payload delivery, diagnostics, and cancer therapy.

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Synthesized 10 nm-size gelatin nanoparticles (G^X) using controlled self-assembly process.

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G^X was used as a platform to encapsulate imaging and therapeutic agents. In addition, smaller size gold nanoparticles also were encapsulated.

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The surface of G^X was used to attach with gold or larger size gelatin nanoparticles.

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Using tumor spheroids, we demonstrated that G^X show enhanced enhancedtumor penetrability.

Cells Undergo Major Changes in the Quantity of Cytoplasmic Organelles after Uptake of Gold Nanoparticles with Biologically Relevant Surface Coatings

Here, we use cryo soft X-ray tomography (cryo-SXT), which delivers 3D ultrastructural volumes of intact cells without chemical fixation or staining, to gain insight about nanoparticle uptake for nanomedicine. We initially used dendritic polyglycerol sulfate (dPGS) with potential diagnostic and therapeutic applications in inflammation. Although dPGS-coated gold nanoparticle (dPGS-AuNP) uptake followed a conventional endocytic/degradative pathway in human lung epithelial cell lines (A549), with cryo-SXT, we detected ∼5% of dPGS-AuNPs in the cytoplasm, a level undetectable by confocal light microscopy. We also observed ∼5% of dPGS-AuNPs in a rarely identified subcellular site, namely, lipid droplets, which are important for cellular energy metabolism. Finally, we also found substantial changes in the quantity of cytoplasmic organelles upon dPGS-AuNP uptake over the 1-6 h incubation period; the number of small vesicles and mitochondria significantly increased, and the number of multivesicular bodies and the number and volume of lipid droplets significantly decreased. Although nearly all organelle numbers at 6 h were still significantly different from controls, most appeared to be returning to normal levels. To test for generality, we also examined cells after uptake of gold nanoparticles coated with a different agent, polyethylenimine (PEI), used for nucleic acid delivery. PEI nanoparticles did not enter lipid droplets, but they induced similar, albeit less pronounced, changes in the quantity of cytoplasmic organelles. We confirmed these changes in organelle quantities for both nanoparticle coatings by confocal fluorescence microscopy. We suggest this cytoplasmic remodeling could reflect a more common cellular response to coated gold nanoparticle uptake.

Silencing AXL by covalent siRNA-gelatin-antibody nanoconjugate inactivates mTOR/EMT pathway and stimulates p53 for TKI sensitization in NSCLC

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality with the 5-year survival rate at a dismal 16% for the past 40 years. Drug resistance is a major obstacle to achieving long-term patient survival. Identifying and validating molecular biomarkers responsible for resistance and thereby adopting multi-directional therapy is necessary to improve the survival rate. Previous studies indicated ~20% of tyrosine kinase inhibitor (TKI) resistant NSCLC patients overexpress AXL with increase in EMT and decrease in p53 expression. To overcome the resistance, we designed gelatin nanoparticles covalently conjugated with EGFR targeting antibody and siRNA (GAbsiAXL). GAbsiAXL efficiently silences AXL, decreases mTOR and EMT signaling with concomitant increase in p53 expression. Because of the molecular changes, the AXL silencing sensitizes the cells to TKI. Our results show AXL overexpression has an important role in driving TKI resistance through close association with energy-dependent mitochondrial pathways.

Cytosolic Transport of Nanoparticles through Pressurized Plasma Membranes for Molecular Delivery and Amplification of Intracellular Fluorescence

Transporting nanoparticles into live cells is important for drug delivery and other related applications. We found that cells exposed to hypoosmotic pressures can internalize substantial quantities of gold nanoparticles. Importantly, these nanoparticles can circumvent normal intracellular traffic and be transported directly into the cytosol, without the need for surface functionalization. In contrast, nanoparticles endocytosed at physiological osmolality are segregated inside endocytic organelles and are not able to reach the cytosol. Cytosolic internalization was observed for nanoparticles of various sizes and materials, with minimal short- or long-term damage induced by the internalized particles. Thus, our strategy can be used as a delivery platform for a range of applications from therapeutics to medical imaging. As examples, we demonstrated rapid delivery of membrane-impermeable molecules to the cytosol by using nanoparticles as carriers and the use of nanoparticles assembled within the cytosol as plasmonic nanoantenna to enhance intracellular fluorescence. We propose a model for the mechanisms behind nanoparticle internalization through pressurized plasma membranes via the release of lateral pressures. Such characterizations may constitute a foundation for developing new technologies, including nanoparticle-based drug delivery.