It is believed that mucoadhesive surface properties on particles delivered to the gastrointestinal (GI) tract improve oral absorption or local targeting of various difficult-to-deliver drug classes. To test the effect of nanoparticle mucoadhesion on distribution of nanoparticles in the GI tract, we orally and rectally administered nano- and microparticles that we confirmed possessed surfaces that were either strongly mucoadhesive or non-mucoadhesive. We found that mucoadhesive particles (MAP) aggregated in mucus in the center of the GI lumen, far away from the absorptive epithelium, both in healthy mice and in a mouse model of ulcerative colitis (UC). In striking contrast, water absorption by the GI tract rapidly and uniformly transported non-mucoadhesive mucus-penetrating particles (MPP) to epithelial surfaces, including reaching the surfaces between villi in the small intestine. When using high gavage fluid volumes or injection into ligated intestinal loops, common methods for assessing oral drug and nanoparticle absorption, we found that both MAP and MPP became well-distributed throughout the intestine, indicating that the barrier properties of GI mucus were compromised. In the mouse colorectum, MPP penetrated into mucus in the deeply in-folded surfaces to evenly coat the entire epithelial surface. Moreover, in a mouse model of UC, MPP were transported preferentially into the disrupted, ulcerated tissue. Our results suggest that delivering drugs in non-mucoadhesive MPP is likely to provide enhanced particle distribution, and thus drug delivery, in the GI tract, including to ulcerated tissues.

Per-butanoylated N-acetyl-D-mannosamine (Bu 4 ManNAc), a SCFA-hexosamine cancer drug candidate with activity manifest through intact n-butyrate-carbohydrate linkages, reduced the invasion of metastatic MDA-MB-231 breast cancer cells unlike per-butanoylated-D-mannose (Bu 5 Man), a clinically-tested compound that did not alter cell mobility. To gain molecular-level insight, therapeutic targets implicated in metastasis were investigated. The active compound Bu 4 ManNAc reduced both MUC1 expression and MMP-9 activity (via down-regulation of CXCR4 transcription) whereas 'inactive' Bu 5 Man had counterbalancing effects on these oncogenes. This divergent impact on transcription was linked to interplay between HDACi activity (held by both Bu 4 ManNAc and Bu 5 Man) and NF-κB activity, which was selectively down-regulated by Bu 4 ManNAc. Overall, these results establish a new therapeutic endpoint (control of invasion) for SCFA-hexosamine hybrid molecules, define relative contributions of molecular players involved in cell mobility, and demonstrate that Bu 4 ManNAc breaks the confounding link between beneficial HDACi activity and the simultaneous deleterious activation of NF-κB often found in epigenetic drug candidates.

Aims We previously demonstrated that nanoparticles (NPs) densely coated with low molecular weight (MW, 2-5 kDa) polyethylene glycol (PEG) rapidly diffused through various mucus secretions, whereas NPs coated with 10 kDa PEG were mucoadhesive due to presumed polymer interpenetration and entanglement with mucins. Here, we demonstrate that PEG with MW as high as 40 kDa can be used as a mucoinert NP surface coating if sufficient surface density is achieved. Materials and Methods We compared two sets of reaction conditions for coating model polystyrene NPs with 10 kDa PEG and used the optimized reaction conditions to coat various sized NPs with PEG with MW as high as 40 kDa. We then characterized NP transport in human cervicovaginal mucus (CVM) ex vivo. We further administered PEG-coated NPs to the mouse cervicovaginal tract and colorectum to assess mucosal distribution in vivo. Results and Conclusions We demonstrate here that PEG with MW as high as 40 kDa can be densely grafted to the surface of NP to prevent interactions with mucus. NP coated with 10-40 kDa PEG rapidly diffused through human CVM ex vivo, and uniformly lined the mouse colorectal and vaginal epithelium in vivo. This not only suggests that the density of PEG on the NP surface, and thus the conformation, is key for preventing interactions with mucus, but also redefines and broadens the design criteria for drug and gene delivery systems for improved mucosal delivery.

Mucosal epithelia use osmotic gradients for fluid absorption and secretion. We hypothesized that administration of hypotonic solutions would induce fluid uptake that could be advantageous for rapidly delivering drugs through mucus to the vaginal epithelium. We found that hypotonic formulations markedly increased the rate at which small molecule drugs and muco-inert nanoparticles (mucus-penetrating particles, or MPP), but not conventional mucoadhesive nanparticles (CP), reached the vaginal epithelial surface in vivo in mice. Additionally, hypotonic formulations greatly enhanced drug and MPP delivery to the entire epithelial surface, including deep into the vaginal folds (rugae) that drugs or MPP in isotonic formulations failed to reach efficiently. However, hypotonic formulations caused unencapsulated “free” drugs to be drawn through the epithelium, reducing vaginal retention. In contrast, hypotonic formulations caused MPP to accumulate rapidly and uniformly on vaginal surfaces, ideally positioned for localized sustained drug delivery. Using a mouse model of vaginal genital herpes (HSV-2) infection, we found that hypotonic delivery of free drug led to improved immediate protection, but diminished longer-term protection. In contrast, as we previously demonstrated, hypotonic delivery of drug via MPP led to better long-term retention and protection in the vagina. Importantly, we demonstrate that slightly hypotonic formulations provided rapid and uniform delivery of MPP to the entire vaginal surface, thus enabling formulations with minimal risk of epithelial toxicity. Hypotonic formulations for vaginal drug delivery via MPP may significantly improve prevention and treatment of reproductive tract diseases and disorders.

Lymphatic vessels are the primary route of communication from peripheral tissues to the immune system; as such, they represent an important component of local immunity. In addition to their transport functions, new immunomodulatory roles for lymphatic vessels and lymphatic endothelial cells have come to light in recent years, demonstrating that lymphatic vessels help shape immune responses in a variety of ways: promoting tolerance to self-antigens, archiving antigen for later presentation, dampening effector immune responses, and resolving inflammation, among others. In addition to these new biological insights, the growing field of immunoengineering has begun to explore therapeutic approaches to utilize or exploit the lymphatic system for immunotherapy.

Sustained drug delivery to mucosal surfaces has the potential to improve the effectiveness of prophylactic and therapeutic treatments for numerous diseases and conditions, including inflammatory bowel disease, sexually transmitted diseases, cystic fibrosis, glaucoma, dry eye and various cancers. Sustained delivery systems such as nanoparticles can be useful for mucosal delivery, but recent work suggests they should penetrate the rapidly cleared mucus barrier that overlies all mucosal epithelia to achieve uniform distribution on epithelial surfaces and enhanced residence time. Thus, it is important to evaluate mucus-penetrating ability of nano-sized delivery systems in preclinical animal studies, and for administration to humans. We describe a simple ex vivo method to visualize and quantify nanoparticle transport in mucus on fresh mucosal tissues. Using this method in murine models, we observed variations in the mucus mesh at various anatomical locations, as well as cyclical variations that may have implications for mucosal delivery.

The rise of bacterial antibiotic resistance has created a demand for alternatives to traditional antibiotics. Attractive possibilities include pro- and anti-quorum sensing therapies that function by modulating bacterial chemical communication circuits. We report the use of Flash NanoPrecipitation to deliver the Vibrio cholerae quorum-sensing signal CAI-1 ((S)-3-hydroxytridecan-4-one) in a water dispersible form as nanoparticles. The particles activate V. cholerae quorum-sensing responses five orders of magnitude higher than does the identically administered free CAI-1, and are diffusive across in vivo delivery barriers such as intestinal mucus. This work highlights the promise of combining quorum-sensing strategies with drug delivery approaches for the development of next-generation medicines.

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