PLGA Microspheres Coated with Cancer Cell-Derived Vesicles for Improved Internalization into Antigen-Presenting Cells and Immune Stimulation.

Microspheres (MS; 1-3 µm) with different degrees of surface roughness were prepared to assess the effects of surface topology on internalization into antigen-presenting cells (APCs; macrophages and dendritic cells). In this study, we demonstrated that the intracellular uptake of MS is readily enhanced by surface modification with nanoparticles or cancer cell-derived vesicles (VE) to modulate their surface topology. MS coated with nanovesicles (MS-VE) with high surface roughness was more successfully and efficiently engulfed by APCs, compared with bare MS and those with low surface roughness. Incorporated MPLA within MS-VEs (M/MS-VE) triggered greatly elevated release of immune stimulating cytokines, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), from macrophages and dendritic cells, compared to free MPLA. Taken together, this MS-VE could serve as a platform system for the delivery of immune stimulators and antigens to APCs with negligible toxicity.

Platelet-derived nanovesicles for hemostasis without release of pro-inflammatory cytokines.

Natural platelet-derived nanovesicles with a vacant core were prepared by hypotonic sonication. The nanovesicles efficiently formed platelet-like aggregates using membrane protein in the presence of thrombin and calcium chloride without a notable release of pro-inflammatory cytokines. These natural and biocompatible platelet-derived nanovesicles have great potential as biomaterials for inflammation-free injectable hemostasis.

Mannose-Modified Serum Exosomes for the Elevated Uptake to Murine Dendritic Cells and Lymphatic Accumulation.

The surface of bovine serum-derived exosomes (EXOs) are modified with α-d-mannose for facile interaction with mannose receptors on dendritic cells (DCs) and for efficient delivery of immune stimulators to the DCs. The surface of the EXOs is modified with polyethylene glycol (PEG) without particle aggregation (≈50 nm) via the incorporation of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE) into the lipid layer of the EXO, compared to chemical conjugation by N-hydroxysuccinimide activated PEG (NHS-PEG). PEG modification onto the exosomal surface significantly decreases the non-specific cellular uptake of the EXOs into the DCs. However, the EXOs with mannose-conjugated PEG-DSPE (EXO-PEG-man) exhibit excellent intracellular uptake into the DCs and boost the immune response by the incorporation of adjuvant, monophosphoryl lipid A (MPLA) within the EXO. After an intradermal injection, a higher retention of EXO-PEG-man is observed in the lymph nodes, which could be used for the efficient delivery of immune stimulators and antigens to the lymph nodes in vivo.

Current preclinical small interfering RNA (siRNA)-based conjugate systems for RNA therapeutics.

Recent promising clinical results of RNA therapeutics have drawn big attention of academia and industries to RNA therapeutics and their carrier systems. To improve their feasibility in clinics, systemic evaluations of currently available carrier systems under clinical trials and preclinical studies are needed. In this review, we focus on recent noticeable preclinical studies and clinical results regarding siRNA-based conjugates for clinical translations. Advantages and drawbacks of siRNA-based conjugates are discussed, compared to particle-based delivery systems. Then, representative siRNA-based conjugates with aptamers, peptides, carbohydrates, lipids, polymers, and nanostructured materials are introduced. To improve feasibility of siRNA conjugates in preclinical studies, several considerations for the rational design of siRNA conjugates in terms of cleavability, immune responses, multivalent conjugations, and mechanism of action are also presented. Lastly, we discuss lessons from previous preclinical and clinical studies related to siRNA conjugates and perspectives of their clinical applications.

Submicron-sized hydrogels incorporating cyclic dinucleotides for selective delivery and elevated cytokine release in macrophages.

Despite the emerging evidences supporting the potential of cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) as a vaccine adjuvant, few properly designed micro-/nanocarriers for the delivery of cyclic dinucleotides have been developed. In this study, we formulated cGAMP within linear polyethyleneimine (LPEI)/hyaluronic acid (HA) hydrogels via inverse water-in-oil (W/O) emulsion/crosslinking. Spherical and cationic LPEI/HA hydrogels (LH gels) with a size of 455.3±3.1nm and a surface charge of 48.7±3.7mV were selectively and efficiently delivered into phagocytic macrophage cells, which are one type of antigen-presenting cells (APCs), but not into non-phagocytic fibroblast cells. LH gels incorporating cGAMP (LH/cGAMP gels) elicited excellent induction of the cytokines interferon-ß (IFN-ß) and interleukin-6 (IL-6). In particular, the amount of IFN-ß released by LH hydrogels was significantly increased by 2.5-fold compared to that released by conventional cationic liposomes, such as Lipofectamine. In addition, fabricated LH gels showed superior biocompatibility in phagocytic cell lines and primary bone marrow-derived macrophages (BMDMs). After intramuscular injection with ovalbumin into C57BL/6 mice, LH/cGAMP gels exhibited significantly elevated levels of anti-ovalbumin total IgG in serum and IFN-ß mRNA in spleens. Thus, the newly designed cGAMP-incorporating hydrogels can serve as safe and potent adjuvants for vaccination and immunotherapy. STATEMENT OF SIGNIFICANCE: Since cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) was first found as a second messenger of immune signaling in human systems in February 2013 (Science, 15, 826), several scientific studies have been reported related to the potential of cGAMP as a vaccine adjuvant or additive for immunotherapy. However, only naked cGAMP without carriers were studied via intramuscular or intranasal administration so far. In our study, we first investigated the feasibility of polymeric hydrogels incorporating cGAMP in terms of selective uptake into phagocytic antigen presenting cells (APCs), induction of cytokines, production of target antibodies, and biocompatibility for vaccination and immunotherapy in vitro and in vivo. Therefore, we believe this manuscript would be of great interest to the biomaterial communities especially who are studying immunotherapy.