(740c) Integrated Rapid Purification of Polymeric Nanoparticles for Drug Delivery In Microfluidic Channels

Minsoung Rhee^1,2, Jong-min Lim¹, Robert S. Langer¹, Omid C. Farokhzad^1,2, Rohit Karnik¹

¹Massachusetts Institute of Technology, USA.

²Brigham and Women’s Hospital, Harvard Medical School, USA.

We report here the development of an integrated microfluidic system that performs polymeric NP synthesis for drug delivery followed by rapid in-line purification in a continuous manner. Polymeric nanoparticles (NPs) comprised of poly(lactide-co-glycolide)-b-polyethyleneglycol (PLGA-PEG) block copolymers have attracted much attention as targeted nanocarriers for delivery of chemotherapeutic agents [1] due to their promising physicochemical characteristics such as easy incorporation of various targeting agents, enhanced stability, tunable drug release, and the ability to carry a payload of thousands of drug molecules per NP [2]. To optimize such characteristics that are not independent of each other, systematic synthesis of such targeted NPs and screening have become very important since precise control of the physicochemical parameters of NPs is required to achieve optimal therapeutic efficacy [3]. Regardless of whether the NPs are synthesized in the microfluidic system [4-5], NP synthesis procedures involve a large quantity of organic solvents and potentially toxic or non-biocompatible materials like unencapsulated drug molecules, large polymer aggregates, and stabilizing agents that substantially limit direct use of synthesized NPs without purification for the following in vitro and in vivo screening. Most of conventional NP purification method typically relying on centrifugation are highly labor-intensive or require extended processing time to achieve desirable concentration and purification of NPs. Besides, separate batch-to-batch procedures, which can significantly retard the overall preparation process, often becomes a bottleneck for screening and optimization of NPs. Therefore, the development of efficient NP purification system has been a common issue in the field of NP synthesis.

 We have designed a microfluidic technology that performs counter-current flow dilution where prepared NPs solution with impurities and washing deionized water are oppositely directed in the microchannel network. This counter-current flow maintains maximum concentration gradients of impurities that in turn facilitate diffusive dilution by washing flow. Since the organic solvent and non-encapsulated drug molecules have higher diffusivities than that of polymeric NPs, the impurities are washed out and NPs can be purified and concentrated with the specially designed microfluidic system where convection between two opposite flows is minimized by imposing high hydrodynamic resistance in connecting bridges. The device operates with input polymer precursors along with drug molecules at programmed flow rates by syringe pumps, and drug-encapsulated NPs assembled in the channel will flow into the purification microchannel network where organic solvent and non-encapsulated drug will be rapidly removed. Such integration of purification functionality eliminates the need for manual collection, delivery, and filtration and thus accelerates the NP preparation and screening process by orders of magnitude. Reduction in processing time also results in faster stabilization of NPs, minimizing the possibility of premature release of encapsulated drug molecules or NP aggregation.

To ensure sufficient time for diffusive dilution, the system may run at a low flow rate, which potentially reduces the throughput. Parallelization of microfluidic purification channels is thus pursued to achieve higher purification capacity. Using the parallel channel architecture constructed by using the multilayer microfluidic device fabrication technique, By simulations and experiments, we propose and examine a microfluidic purification system to achieve 99.9% v/v removal of organic solvent and 99% w/w removal of free drug molecules. We believe that this approach will lead to a platform technology for fully automated and high throughput preparation of NPs that can be directly used for screening without further processing steps. Consequently, development of an integrated microfluidic system for single-step NP preparation will have a substantial impact on current NP research in our lab and other labs by enabling high throughput and increased stability of purified NPs.

REFERENCES:

[1] “Formulation of functionalized PLGA-PEG nanoparticles for in vivo targeted drug delivery,” J. Cheng et al., Biomaterials, 28, 869 (2007).

[2] “Targeted nanoparticles for cancer therapy,” F. Gu et al., Nano Today, 2, 14 (2007).

[3] “Translational Nanomedicine: Status. Assessment and Opportunities,” J. S. Murday, R. W. Siegel, J. Stein, J. F. Wright, Nanomedicine, 5, 251 (2009).

[4] “Microfluidic Platform for Controlled Synthesis of Polymeric Nanoparticles,” R. Karnik et al., Nano Lettlers, 8, 2906 (2008).

[5] “Synthesis of Size-Tunable Polymeric Nanoparticles Enabled by 3D Hydrodynamic Flow Focusing in Single-Layer Microchannels”, M. Rhee et al., Advanced Materials, 23, H78 (2011).