Zhiyong Poon

Controlling in Vivo Stability and Biodistribution in Electrostatically Assembled Nanoparticles for Systemic Delivery

This paper demonstrates the generation of systemically deliverable layer-by-layer (LbL) nanoparticles for cancer applications. LbL-based nanoparticles designed to navigate the body and deliver therapeutics in a programmable fashion are promising new and alternative systems for drug delivery, but there have been very few demonstrations of their systemic delivery in vivo due to a lack of knowledge in building LbL nanofilms that mimic traditional nanoparticle design to optimize delivery. The key to the successful application of these nanocarriers in vivo requires a systematic analysis of the influence of film architecture and adsorbed polyelectrolyte outer layer on their pharmacokinetics, which has thus far not been examined for this new approach to nanoparticle delivery. Herein, we have taken the first steps in stabilizing and controlling the systemic distribution of multilayer nanoparticles. Our findings highlight the unique character of LbL systems; the electrostatically assembled nanoparticles gain increased stability in vivo with larger numbers of deposited layers, and the final layer adsorbed generates a critical surface cascade, which dictates the surface chemistry and biological properties of the nanoparticle. This outer polyelectrolyte layer dramatically affects not only the degree of nonspecific particle uptake, but also the nanoparticle biodistribution. For hyaluronic acid (HA) outer layers, a long blood elimination half-life (∼9 h) and low accumulation (∼10-15% recovered fluorescence/g) in the liver were observed, illustrating that these systems can be designed to be highly appropriate for clinical translation.

Hydrogen-bonded multilayer of pH-responsive polymeric micelles with tannic acid for surface drug delivery

We report the design of a platform for the delivery of hydrophobic drugs conjugated to block copolymer micelles via pH-responsive linkage that are assembled within hydrogen-bonded polymer multilayer thin films.

Ligand-Clustered “Patchy” Nanoparticles for Modulated Cellular Uptake and In Vivo Tumor Targeting†

Despite the evident success of using a multivalent approach to increase efficacy of targeted delivery, a clear understanding of how multiple ligands behave collectively to influence the uptake of nanoparticle cell-targeting agents has not been reached. Although when present in large quantity, multivalent ligands can increase binding avidities to cells, it is also conceivable, that the manner in which these ligands are presented to the cell may have a significant effect on uptake. Here we examine this parameter using a linear dendritic polymer construct that enabled us to pattern the surfaces of nanoparticles with variable sized ligand clusters in different spatial arrangements. We demonstrate for the first time the clear impact of folate presentation on intracellular uptake both in vitro and in vivo. The findings presented here suggest that the nature of ligand presentation on a nanoparticle surface may play an important role in drug targeting; the results suggest potential impact for other targeting moieties and provide a framework for further refinement of future multivalent targeting strategies.

MAD (multiagent delivery) nanolayer: delivering multiple therapeutics from hierarchically assembled surface coatings.

We present hydrolytically degradable polymeric multilayer films that can codeliver multiple therapeutics of differing chemical characteristics (charged biomacromolecules and neutral hydrophobic small molecules) from a surface. This multiagent-delivery (MAD) nanolayer system integrates the hydrolytically degradable poly(beta-amino ester) as a structural component to control the degradation of the multilayers to release active therapeutic macromolecules as well as hydrophobic drugs imbedded within amphiphilic block copolymer micellar carriers within layer-by-layer (LbL) films, which would otherwise be difficult to include within the multilayers. By varying the anionic therapeutic agents (heparin and dextran sulfate) within the multilayer, we examine how different structural components can be used to control the release kinetics of multiple therapeutics from MAD nanolayers. Controlled release profiles and the in vitro efficacy of the MAD nanolayers in suppressing the growth of human smooth muscle cell lines were evaluated. The dual delivery of a charged macromolecular heparin and a small hydrophobic drug, paclitaxel, is found to be synergistic and beneficial toward effective therapeutic activity. Furthermore, we compared the classical dipping method that we employed here with an automated spray-LbL technique. Spray-LbL significantly facilitates film processing time while preserving the characteristic release profiles of the MAD nanolayers. With the highly versatile and tunable nature of LbL assembly, we anticipate that MAD nanolayers can provide a unique platform for delivering multiple therapeutics from macromolecules to small molecules with distinct release profiles for applications in biological and biomedical surface coatings.

Layer-by-Layer Assembled Antisense DNA Microsponge Particles for Efficient Delivery of Cancer Therapeutics

Antisense oligonucleotides can be employed as a potential approach to effectively treat cancer. However, the inherent instability and inefficient systemic delivery methods for antisense therapeutics remain major challenges to their clinical application. Here, we present a polymerized oligonucleotides (ODNs) that self-assemble during their formation through an enzymatic elongation method (rolling circle replication) to generate a composite nucleic acid/magnesium pyrophosphate sponge-like microstructure, or DNA microsponge, yielding high molecular weight nucleic acid product. In addition, this densely packed ODN microsponge structure can be further condensed to generate polyelectrolyte complexes with a favorable size for cellular uptake by displacing magnesium pyrophosphate crystals from the microsponge structure. Additional layers are applied to generate a blood-stable and multifunctional nanoparticle via the layer-by-layer (LbL) assembly technique. By taking advantage of DNA nanotechnology and LbL assembly, functionalized DNA nanostructures were utilized to provide extremely high numbers of repeated ODN copies for efficient antisense therapy. Moreover, we show that this formulation significantly improves nucleic acid drug/carrier stability during in vivo biodistribution. These polymeric ODN systems can be designed to serve as a potent means of delivering stable and large quantities of ODN therapeutics systemically for cancer treatment to tumor cells at significantly lower toxicity than traditional synthetic vectors, thus enabling a therapeutic window suitable for clinical translation.

The architecture and biological performance of drug-loaded LbL nanoparticles.

Layer-by-Layer (LbL) nanoparticles are an emerging class of therapeutic carriers that afford precise control over key design parameters that facilitate improved drug and carrier pharmacokinetics, and enhanced molecular-targeting capabilities. This paper advances the development of these systems by establishing them as drug carriers, with the means to control drug release in a systemic environment and retard particle clearance from circulation, promoting improved biodistribution of the drug-containing system. Using dual-fluorescent tracking in vivo, this work establishes a robust means of screening libraries of LbL systems generated, affording simultaneous resolution over persistence and biodistribution of both the drug and carrier following systemic administration of a single particle formulation. Employing a PLGA drug-containing core as a substrate for LbL deposition, a range of coated systems were fabricated to investigate the abilities of these films to stabilize drug for delivery as well as to improve the pharmacokinetics of both the drug and carrier. Significant reductions in liver accumulation were observed for different formulations of the layered architectures within the first 30 min of systemic circulation. LbL architectures diminished liver localization of the surrogate drug, cardiogreen, by 10-25% ID/g relative to native PLGA nanoparticles and modulated carrier accumulation in the liver >50% ID/g. Further, enhanced persistence of the drug was observed with the coated systems, significantly increasing the drug half-life from 2 to 3 min for free drug and 1.87 h for the uncoated core to 4.17 h and 4.54 h for the coated systems. These systems provide an exciting, modular platform that improves the pharmacokinetic properties of the therapeutic, reduces bolus release of drug from nanoparticles, and enhances the safety and circulation half-life of the drug in vivo, proving them to be highly clinically-relevant and a promising approach for future development of molecularly-targeted and combination therapeutics.

Osteotropic Therapy via Targeted Layer-by-Layer Nanoparticles

Current treatment options for debilitating bone diseases such as osteosarcoma, osteoporosis, and bone metastatic cancer are suboptimal and have low efficacy. New treatment options for these pathologies require targeted therapy that maximizes exposure to the diseased tissue and minimizes off-target side effects. This work investigates an approach for generating functional and targeted drug carriers specifically for treating primary osteosarcoma, a disease in which recurrence is common and the cure rate has remained around 20%. This approach utilizes the modularity of Layer-by-Layer (LbL) assembly to generate tissue-specific drug carriers for systemic administration. This is accomplished via surface modification of drug-loaded nanoparticles with an aqueous polyelectrolyte, poly(acrylic acid) (PAA), side-chain functionalized with alendronate, a potent clinically used bisphosphonate. Nanoparticles coated with PAA-alendronate are observed to bind and internalize rapidly in human osteosarcoma 143B cells. Encapsulation of doxorubicin, a front-line chemotherapeutic, in an LbL-targeted liposome demonstrates potent toxicity in vitro. Active targeting of 143B xenografts in NCR nude mice with the LbL-targeted doxorubicin liposomes promotes enhanced, prolonged tumor accumulation and significantly improved efficacy. This report represents a tunable approach towards the synthesis of drug carriers, in which LbL enables surface modification of nanoparticles for tissue-specific targeting and treatment.

Chapter 12:Applications of Janus and Anisotropic Particles for Drug Delivery

The interactions of micro- and nanoparticles with various cells inside the body determine their effectiveness as carriers for drug delivery.1–6 These interactions are governed by the nanoparticle’s inactive or active material properties,2,7–13 which include surface chemistry,14–16 size,9,17,18 shape...