Controlling and Predicting Nanoparticle Formation by Block Copolymer Directed Rapid Precipitations.

Nanoparticles have shown promise in several biomedical applications, including drug delivery and medical imaging; however, quantitative prediction of nanoparticle formation processes that scale from laboratory to commercial production has been lacking. Flash NanoPrecipitation (FNP) is a scalable technique to form highly loaded, block copolymer protected nanoparticles. Here, the FNP process is shown to strictly obey diffusion-limited aggregation assembly kinetics, and the parameters that control the nanoparticle size and the polymer brush density on the nanoparticle surface are shown. The particle size, ranging from 40 to 200 nm, is insensitive to the molecular weight and chemical composition of the hydrophobic encapsulated material, which is shown to be a consequence of the diffusion-limited growth kinetics. In a simple model derived from these kinetics, a single constant describes the 46 unique nanoparticle formulations produced here. The polymer brush densities on the nanoparticle surface are weakly dependent on the process parameters and are among the densest reported in the literature. Though modest differences in brush densities are observed, there is no measurable difference in the amount of protein adsorbed within this range. This work highlights the material-independent and universal nature of the Flash NanoPrecipitation process, allowing for the rapid translation of formulations to different stabilizing polymers and therapeutic loads.

Sustained release of peptides and proteins from polymeric nanocarriers produced by inverse Flash NanoPrecipitation.

Peptide and protein therapeutics generally exhibit high potency and specificity and are increasingly important segments of the pharmaceutical market. However, their clinical applications are limited by rapid clearance and poor membrane permeability. Encapsulation of the peptide or protein into a nano-scale carrier can modify its pharmacokinetics and biodistribution. This might be employed to promote uptake in desired cell types or tissues, to limit systemic exposure, or to reduce the need for frequent injections. We have recently described inverse Flash NanoPrecipitation (iFNP), a scalable technique to encapsulate water-soluble therapeutics into polymeric nanocarriers, and have demonstrated improvements in therapeutic loading of an order of magnitude over comparable approaches. Here, we describe the formulation parameters that control release rates of encapsulated model therapeutics polymyxin B, lysozyme, and bovine serum albumin from nanocarriers produced using iFNP. Using a neutropenic lung infection mouse model with a multi-drug resistant Acinetobacter baumannii clinical isolate, we demonstrate enhanced therapeutic effect and safety profile afforded by nanocarrier-encapsulated polymyxin B following pulmonary administration. The encapsulated formulation reduced toxicity observed at elevated doses and resulted in up to 2.7-log10 reduction in bacterial burden below that of unencapsulated polymyxin B. These results establish the promise of iFNP as a platform for nanocarrier delivery of water-soluble therapeutics.

Polymeric Nanocarrier Formulations of Biologics Using Inverse Flash NanoPrecipitation.

The encapsulation of water-soluble therapeutics and biologics into nanocarriers to produce novel therapeutics has been envisioned for decades, but clinical translation has been hampered by complex synthesis strategies. The methods that have been developed are often limited by poor encapsulation efficiency/loading or complex processing to achieve therapeutic loadings high enough to be medically relevant. To address this unmet need, we introduce a solubility-driven self-assembly process to form polymeric nanocarriers comprising a biologic in a hydrophilic core, encapsulated by a poly(lactic acid) shell, and stabilized by a poly(ethylene glycol) brush. Called "inverse Flash NanoPrecipitation (iFNP)," the technique achieves biologic loadings (wt% of total formulation) that are 5-15× higher than typical values (9-27% versus < 2%). In contrast to liposomes and polymersomes, we sequentially assemble the polymer layers to form the final nanocarrier. Installation of the poly(lactic acid) shell before water exposure sequesters the biologic in the core and results in the improved loadings that are achieved. We demonstrate the broad applicability of the process and illustrate its implementation by formulating over a dozen different oligosaccharides, antibiotics, peptides, proteins, and RNA into nanocarriers with narrow size distributions, at high loadings, and with high reproducibility. Lysozyme and horseradish peroxidase are shown to retain 99% activity after processing. These results demonstrate the potential for commercial implementation of this technology, enabling the translation of novel treatments in immunology, oncology, or enzyme therapies.

Flash NanoPrecipitation for the Encapsulation of Hydrophobic and Hydrophilic Compounds in Polymeric Nanoparticles.

The formulation of a therapeutic compound into nanoparticles (NPs) can impart unique properties. For poorly water-soluble drugs, NP formulations can improve bioavailability and modify drug distribution within the body. For hydrophilic drugs like peptides or proteins, encapsulation within NPs can also provide protection from natural clearance mechanisms. There are few techniques for the production of polymeric NPs that are scalable. Flash NanoPrecipitation (FNP) is a process that uses engineered mixing geometries to produce NPs with narrow size distributions and tunable sizes between 30 and 400 nm. This protocol provides instructions on the laboratory-scale production of core-shell polymeric nanoparticles of a target size using FNP. The protocol can be implemented to encapsulate either hydrophilic or hydrophobic compounds with only minor modifications. The technique can be readily employed in the laboratory at milligram scale to screen formulations. Lead hits can directly be scaled up to gram- and kilogram-scale. As a continuous process, scale-up involves longer mixing process run time rather than translation to new process vessels. NPs produced by FNP are highly loaded with therapeutic, feature a dense stabilizing polymer brush, and have a size reproducibility of ± 6%.

Efficient preparation of size tunable PEGylated gold nanoparticles.

A facile, one-step self-assembly of polymer nanoreactors is reported for the fabrication of uniform PEGylated gold nanoparticles. Nanoreactor assembly occurs within milliseconds and gold nanoparticles are produced within minutes at room temperature. The presented approach enables continuous synthesis of size tunable gold nanoparticles with tailorable surface chemistry.

Polymeric nanoparticles and microparticles for the delivery of peptides, biologics, and soluble therapeutics.

Biologically derived therapeutics, or biologics, are the most rapidly growing segment of the pharmaceutical marketplace. However, there are still unmet needs in improving the delivery of biologics. Injectable polymeric nanoparticles and microparticles capable of releasing proteins and peptides over time periods as long as weeks or months have been a major focus in the effort to decrease the frequency of administration. These particle systems fit broadly into two categories: those composed of hydrophilic and those composed of hydrophobic polymeric scaffolds. Here we review the factors that contribute to the slow and controlled release from each class of particle, as well as the effects of synthesis parameters and product design on the loading, encapsulation efficiency, biologic integrity, and release profile. Generally, hydrophilic scaffolds are ideal for large proteins while hydrophobic scaffolds are more appropriate for smaller biologics without secondary structure. Here we also introduce a Flash NanoPrecipitation method that has been adopted for encapsulating biologics in nanoparticles (40-200nm) at high loadings (50-75wt.%) and high encapsulation efficiencies. The hydrophilic gel interior and hydrophobic shell provide an opportunity to combine the best of both classes of injectable polymeric depots.

Single-Step Assembly of Multimodal Imaging Nanocarriers: MRI and Long-Wavelength Fluorescence Imaging.

Magnetic resonance imaging (MRI)- and near-infrared (NIR)-active, multimodal composite nanocarriers (CNCs) are prepared using a simple one-step process, flash nanoprecipitation (FNP). The FNP process allows for the independent control of the hydrodynamic diameter, co-core excipient and NIR dye loading, and iron oxide-based nanocrystal (IONC) content of the CNCs. In the controlled precipitation process, 10 nm IONCs are encapsulated into poly(ethylene glycol) (PEG) stabilized CNCs to make biocompatible T2 contrast agents. By adjusting the formulation, CNC size is tuned between 80 and 360 nm. Holding the CNC size constant at an intensity weighted average diameter of 99 ± 3 nm (PDI width 28 nm), the particle relaxivity varies linearly with encapsulated IONC content ranging from 66 to 533 × 10(-3) m(-1) s(-1) for CNCs formulated with 4-16 wt% IONC. To demonstrate the use of CNCs as in vivo MRI contrast agents, CNCs are surface functionalized with liver-targeting hydroxyl groups. The CNCs enable the detection of 0.8 mm(3) non-small cell lung cancer metastases in mice livers via MRI. Incorporating the hydrophobic, NIR dye tris-(porphyrinato)zinc(II) into CNCs enables complementary visualization with long-wavelength fluorescence at 800 nm. In vivo imaging demonstrates the ability of CNCs to act both as MRI and fluorescent imaging agents.