Subcutaneous nanotherapy repurposes the immunosuppressive mechanism of rapamycin to enhance allogeneic islet graft viability.

Standard oral rapamycin (that is, Rapamune) administration is plagued by poor bioavailability and broad biodistribution. Thus, this pleotropic mammalian target of rapamycin (mTOR) inhibitor has a narrow therapeutic window and numerous side effects and provides inadequate protection to transplanted cells and tissues. Furthermore, the hydrophobicity of rapamycin limits its use in parenteral formulations. Here, we demonstrate that subcutaneous delivery via poly(ethylene glycol)-b-poly(propylene sulfide) polymersome nanocarriers significantly alters rapamycin's cellular biodistribution to repurpose its mechanism of action for tolerance, instead of immunosuppression, and minimize side effects. While oral rapamycin inhibits T cell proliferation directly, subcutaneously administered rapamycin-loaded polymersomes modulate antigen presenting cells in lieu of T cells, significantly improving maintenance of normoglycemia in a clinically relevant, major histocompatibility complex-mismatched, allogeneic, intraportal (liver) islet transplantation model. These results demonstrate the ability of a rationally designed nanocarrier to re-engineer the immunosuppressive mechanism of a drug by controlling cellular biodistribution.

The Combination of Morphology and Surface Chemistry Defines the Immunological Identity of Nanocarriers in Human Blood.

Upon exposure to blood, a corona of proteins adsorbs to nanocarrier surfaces to confer a biological identity that interfaces with the immune system. While the nanocarrier surface chemistry has long been the focus of protein corona formation, the influence of nanostructure has remained unclear despite established influences on biodistribution, clearance, and inflammation. Here, combinations of nanocarrier morphology and surface chemistry are engineered to i) achieve compositionally distinct protein coatings in human blood and ii) control protein-mediated interactions with the immune system. A library of nine PEGylated nanocarriers differing in their combination of morphology (spheres, vesicles, and cylinders) and surface chemistry (methoxy, hydroxyl, and phosphate) are synthesized to represent properties of therapeutic and biomimetic delivery vehicles. Analysis by quantitative label-free proteomic techniques reveal that specific surface chemistry and morphology combinations adsorb unique protein signatures from human blood, resulting in differential complement activation and elicitation of distinct proinflammatory cytokine responses. Furthermore, nanocarrier morphology is shown to primarily influence uptake and clearance by human monocytes, macrophages, and dendritic cells. This comprehensive analysis provides mechanistic insights into rational design choices that impact the immunological identity of nanocarriers in human blood, which can be leveraged to engineer drug delivery vehicles for precision medicine and immunotherapy.

Immune checkpoint inhibition in syngeneic mouse cancer models by a silicasome nanocarrier delivering a GSK3 inhibitor.

Checkpoint blocking antibodies that interfere in the PD-1/PD-L1 axis provide effective cancer immunotherapy for tumors that are immune inflamed or induced to become "hot". It has also been demonstrated that a small molecule inhibitor of the signaling hub kinase GSK3 can interfere in the PD-1/PD-L1 axis in T-cells by suppressing PD-1 expression. This provides an alternative approach to intervening in the PD-1/PD-L1 axis to provide cancer immunotherapy. In this communication, we demonstrate the remote loading of GSK3 inhibitor AZD1080 into the porous interior of mesoporous silica nanoparticles coated with a lipid bilayer (a.k.a. silicasomes). In a MC38 colon cancer model, intravenous injection (IV) of silicasome-encapsulated AZD1080 significantly improved biodistribution and drug delivery to the tumor site. The improved drug delivery was accompanied by cytotoxic MC38 tumor cell killing by perforin-releasing CD8+ T-cells, exhibiting reduced PD-1 expression. IV injection of encapsulated AZD1080 also resulted in significant tumor shrinkage in other syngeneic mouse tumor models, including another colorectal tumor (CT26), as well as pancreas (KPC) and lung (LLC) cancer models. Not only was the therapeutic efficacy of encapsulated AZD1080 similar or better than anti-PD-1 antibody, but the treatment was devoid of treatment toxicity. These results provide proof-of-principal demonstration of the feasibility of using encapsulated delivery of a GSK3 inhibitor to provide cancer immunotherapy, with the possibility to be used as a monotherapy or in combination with chemotherapy or other immunomodulatory agents.

Antigen- and Epitope-Delivering Nanoparticles Targeting Liver Induce Comparable Immunotolerance in Allergic Airway Disease and Anaphylaxis as Nanoparticle-Delivering Pharmaceuticals.

The targeting of natural tolerogenic liver sinusoidal endothelial cells (LSEC) by nanoparticles (NPs), decorated with a stabilin receptor ligand, is capable of generating regulatory T-cells (Tregs), which can suppress antigen-specific immune responses, including to ovalbumin (OVA), a possible food allergen. In this regard, we have previously demonstrated that OVA-encapsulating poly(lactic-co-glycolic acid) (PLGA) nanoparticles eliminate allergic airway inflammation in OVA-sensitized mice, prophylactically and therapeutically. A competing approach is a nanocarrier platform that incorporates pharmaceutical agents interfering in mTOR (rapamycin) or NF-κB (curcumin) pathways, with the ability to induce a tolerogenic state in nontargeted antigen-presenting cells system-wide. First, we compared OVA-encapsulating, LSEC-targeting tolerogenic nanoparticles (TNPs) with nontargeted NPs incorporating curcumin and rapamycin (Rapa) in a murine eosinophilic airway inflammation model, which is Treg-sensitive. This demonstrated roughly similar tolerogenic effects on allergic airway inflammation by stabilin-targeting NPOVAversus nontargeted NPs delivering OVA plus Rapa. Reduction in eosinophilic inflammation and TH2-mediated immune responses in the lung was accompanied by increased Foxp3+ Treg recruitment and TGF-ß production in both platforms. As OVA incorporates IgE-binding as well as non-IgE-binding epitopes, the next experiment explored the possibility of obtaining immune tolerance by non-anaphylactic T-cell epitopes. This was accomplished by incorporating OVA323-339 and OVA257-264 epitopes in liver-targeting NPs to assess the prophylactic and therapeutic impact on allergic inflammation in transgenic OT-II mice. Importantly, we demonstrated that the major histocompatibility complex (MHC)-II binding (former) but not the MHC-I binding (latter) epitope interfered in allergic airway inflammation, improving TNPOVA efficacy. The epitope-specific effect was transduced by TGF-ß-producing Tregs. In the final phase of experimentation, we used an OVA-induced anaphylaxis model to demonstrate that targeted delivery of OVA and its MHC-II epitope could significantly suppress the anaphylaxis symptom score, mast cell release, and the late-phase inflammatory response. In summary, these results demonstrate comparable efficacy of LSEC-targeting versus pharmaceutical PLGA nanoparticles, as well as the ability of T-cell epitopes to achieve response outcomes similar to those of the intact allergens.

Employing bicontinuous-to-micellar transitions in nanostructure morphology for on-demand photo-oxidation responsive cytosolic delivery and off-on cytotoxicity.

Bicontinuous nanospheres (BCNs) are underutilized self-assembled nanostructures capable of simultaneous delivery of both hydrophilic and hydrophobic payloads. Here, we demonstrate that BCNs assembled from poly(ethylene glycol)-block-poly(propylene sulfide) (PEG-b-PPS), an oxidation-sensitive copolymer, are stably retained within cell lysosomes following endocytosis, resisting degradation and payload release for days until externally triggered. The oxygen scavenging properties and enhanced stability of the bicontinuous PEG-b-PPS nanoarchitecture significantly protected cells from typically cytotoxic application of pro-apoptotic photo-oxidizer pheophorbide A and chemotherapeutic camptothecin. The photo-oxidation triggered transition from a bicontinuous to micellar morphology overcame this stability, allowing on-demand cytosolic delivery of camptothecin for enhanced control over off-on cytotoxicity. These results indicate that inducible transitions in the nanostructure morphology can influence intracellular stability and toxicity of self-assembled nanotherapeutics.

Celastrol-loaded PEG-b-PPS nanocarriers as an anti-inflammatory treatment for atherosclerosis.

In this work, the hydrophobic small molecule NF-κB inhibitor celastrol was loaded into poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) micelles. PEG-b-PPS micelles demonstrated high loading efficiency, low polydispersity, and no morphological changes upon loading with celastrol. Encapsulation of celastrol within these nanocarriers significantly reduced cytotoxicity compared to free celastrol, while simultaneously expanding the lower concentration range for effective inhibition of NF-κB signaling by nearly 50 000-fold. Furthermore, celastrol-loaded micelles successfully reduced TNF-α secretion after LPS stimulation of RAW 264.7 cells and reduced the number of neutrophils and inflammatory monocytes within atherosclerotic plaques of ldlr-/- mice. This reduction in inflammatory cells was matched by a reduction in plaque area, suggesting that celastrol-loaded nanocarriers may serve as an anti-inflammatory treatment for atherosclerosis.

Surface engineered polymersomes for enhanced modulation of dendritic cells during cardiovascular immunotherapy.

The principle cause of cardiovascular disease (CVD) is atherosclerosis, a chronic inflammatory condition characterized by immunologically complex fatty lesions within the intima of arterial vessel walls. Dendritic cells (DCs) are key regulators of atherosclerotic inflammation, with mature DCs generating pro-inflammatory signals within vascular lesions and tolerogenic DCs eliciting atheroprotective cytokine profiles and regulatory T cell (Treg) activation. Here, we engineered the surface chemistry and morphology of synthetic nanocarriers composed of poly(ethylene glycol)-b-poly(propylene sulfide) copolymers to selectively target and modulate DCs by transporting the anti-inflammatory agent 1, 25-Dihydroxyvitamin D3 (aVD) and ApoB-100 derived antigenic peptide P210. Polymersomes decorated with an optimized surface display and density for a lipid construct of the P-D2 peptide, which binds CD11c on the DC surface, significantly enhanced the cytosolic delivery and resulting immunomodulatory capacity of aVD in vitro. Intravenous administration of the optimized polymersomes achieved selective targeting of DCs in atheroma and spleen compared to all other cell populations, including both immune and CD45- cells, and locally increased the presence of tolerogenic DCs and cytokines. aVD-loaded polymersomes significantly inhibited atherosclerotic lesion development in high fat diet-fed ApoE-/- mice following 8 weeks of administration. Incorporation of the P210 peptide generated the largest reductions in vascular lesion area (~33%, p<0.001), macrophage content (~55%, p<0.001), and vascular stiffness (4.8-fold). These results correlated with an ~6.5-fold increase in levels of Foxp3+ regulatory T cells within atherosclerotic lesions. Our results validate the key role of DC immunomodulation during aVD-dependent inhibition of atherosclerosis and demonstrate the therapeutic enhancement and dosage lowering capability of cell-targeted nanotherapy in the treatment of CVD.

On the advancement of polymeric bicontinuous nanospheres toward biomedical applications.

Self-assembled soft nanocarriers that are capable of simultaneous encapsulation of both lipophilic and water soluble payloads have significantly enhanced controlled delivery applications in biomedicine. These nanoarchitectures, such as liposomes, polymersomes and cubosomes, are primarily composed of either amphiphilic polymers or lipids, with the polymeric variants generally possessing greater stability and control over biodistribution and bioresponsive release. Polymersomes have long demonstrated such advantages over their lipid analogs, liposomes, but only recently have bicontinuous nanospheres emerged as a polymeric cubic phase alternative to lipid cubosomes. In this review, we summarize the current state of the field for bicontinuous nanosphere formulation and characterization and suggest future directions for this nascent delivery platform as it is adopted for biomedical applications.

Benchmarking Bicontinuous Nanospheres against Polymersomes for in Vivo Biodistribution and Dual Intracellular Delivery of Lipophilic and Water-Soluble Payloads.

Bicontinuous nanospheres (BCNs) are polymeric analogs to lipid cubosomes, possessing cubic liquid crystalline phases with high internal surface area, aqueous channels for loading hydrophilic molecules, and high hydrophobic volume for lipophilic payloads. Primarily due to difficulties in scalable and consistent fabrication, neither controlled delivery of payloads via BCNs nor their organ or cellular biodistributions following in vivo administration have been demonstrated or characterized. We have recently validated flash nanoprecipitation as a rapid method of assembling uniform monodisperse 200-300 nm diameter BCNs from poly(ethylene glycol) -b-poly(propylene sulfide) (PEG -b-PPS) co-polymers. Here, we compare these BCNs both in vitro and in vivo to 100 nm PEG -b-PPS polymersomes (PSs), which have been well characterized as nanocarriers for controlled delivery applications. Using a small molecule fluorophore and a fluorescently tagged protein as respective lipophilic and water-soluble model cargos, we demonstrate that BCNs can achieve significantly higher encapsulation efficiencies for both payloads on a per unit mass basis. At time points of 4 and 24 h after intravenous administration to mice, we found significant differences in organ-level uptake between BCNs and PSs, with BCNs showing reduced accumulation in the liver and increased uptake in the spleen. Despite these organ-level differences, BCNs and PSs displayed strikingly similar uptake profiles by immune cell populations in vitro and in the liver, spleen, and blood, as assayed by flow cytometry. In conclusion, we have found PEG -b-PPS BCNs to be well suited for dual loading and delivery of molecular payloads, with a favorable organ biodistribution and high cell uptake by therapeutically relevant immune cell populations.