Biodegradable nanoparticles composed entirely of safe materials that rapidly penetrate human mucus.

Mucus is a highly viscoelastic and adhesive substance that protects against infection and injury at nearly all entry points to the body not covered by skin. However, mucus also traps potentially life-saving drugs and nucleic acids delivered by synthetic nanoparticles, including those composed of poly(lactic-co-glycolic acid) (PLGA) and poly(e-caprolactone) (PCL), two FDA-approved polymers commonly used in drugdelivery applications. Trapped particles, with diffusivities in mucus several-thousand-fold lower than in water, do not efficiently reach the deeper mucus layers that are cleared much more slowly, or the underlying epithelium, and are thus eliminated by mucus clearance mechanisms (on the order of seconds to a few hours depending on anatomical site). For sustained or targeted drug delivery to mucosal surfaces, nanoparticles must quickly penetrate mucus gels, a longstanding challenge in drug delivery. We recently demonstrated that covalently coating particles with a high density of low-molecular-weight (low MW) poly(ethylene glycol) (PEG), a hydrophilic and uncharged polymer widely used in pharmaceuticals, can reduce particle affinity to mucus constituents. Densely coated particles were able to rapidly penetrate fresh, undiluted human mucus, with speeds only a few-fold lower than in water, by diffusing within the low-viscosity interstitial fluid between mucin fibers without experiencing the bulk viscosity of mucus. However, current methods of producing mucus-penetrating particles (MPPs) require covalent conjugation of PEG to polymers or pre-fabricated particles, resulting in new chemical entities (NCEs), which are subject to a lengthy and expensive FDA regulatory process. We sought to develop a simple noncovalent coating process to produce MPPs composed entirely of generally recognized as safe (GRAS) materials. Uncharged amphiphilic GRAS materials, such as triblock copolymers of poly(ethylene glycol)-poly(propylene oxide)-poly(ethylene glycol) (PEG-PPO-PEG; known as Pluronics), may coat hydrophobic particle surfaces by adsorption through the hydrophobic PPO segments, leaving a dense brush of uncharged, hydrophilic PEG segments protruding from the particle surface. Here, we show that a number of Pluronics molecules, containing PPO segments with MW 3 kDa, can effectively coat PLGA, PCL, and latex nanoparticles, thereby enabling the formulation of MPPs composed entirely of GRAS materials, with no NCEs generated. Synthetic MPPs composed entirely of GRAS materials will likely facilitate rapid translation of nanomaterials-based products into humans for the treatment of numerous diseases and conditions that affect mucosal tissues. Pluronics of differentMWand PPO/PEG ratios have been adopted for various biomedical applications. We first sought to identify which Pluronics may coat normally mucoadhesive polymeric nanoparticles sufficiently to transform them into MPPs. As a proof-of-concept, we formulated fluorescently labeled PLGA nanoparticles, and incubated separate batches with Pluronic P65, F38, P103, P105, F68, or F127 (listed in order of increasing MW) followed by purification. We then observed nanoparticle transport dynamics in freshly obtained, undiluted human cervicovaginal mucus (CVM). Uncoated PLGA nanoparticles were extensively immobilized in CVM (Figure 1a). Three of the Pluronics (F38, P65, and F68) tested did not enhance the transport of PLGA particles, as evident by the highly constrained, non-Brownian time-lapse traces of the particles in mucus (Figure 1b). In contrast, coating PLGA particles with P103, P105, or F127 allowed them to readily penetrate CVM, as evident by their diffusive, Brownian trajectories that covered large distances over the course of 20 s movies (Figure 1c). The effectiveness of the Pluronic coatings was critically dependent on the MW of the PPO [*] Prof. Dr. J. Hanes Departments of Ophthalmology, Biomedical Engineering, Chemical & Biomolecular Engineering and Oncology Center for Cancer Nanotechnology Excellence Institute for NanoBioTechnology and Center for Nanomedicine Johns Hopkins University School of Medicine 400 North Broadway, Baltimore, MD 21287 (USA) Fax: (+1)410-614-6509 E-mail: [email protected] Homepage: http://www.jhu.edu/haneslab/ M. Yang, Y.-Y. Wang, W. Zhong Department of Biomedical Engineering Johns Hopkins University, Baltimore (USA) Dr. S. K. Lai, [+] C. Happe, M. Zhang Department of Chemical & Biomolecular Engineering Johns Hopkins University, Baltimore (USA)