ABSTRACT
Poly(ethylene glycol)-stabilized poly(propylene sulfide) core (PEG-PPS) nanoparticles (NPs) smaller than 50 nm efficiently travel to draining lymph nodes and interact with antigen-presenting cells (APCs) to induce potent immune responses following intradermal immunization. To determine if a similar system could be developed that could be more easily and reproducibly prepared and eliminated faster in vivo, we created block copolymers of PEG-bl-PPS capable of self-assembling into 25-35 nm micelles (MCs). Biodistribution studies showed that these MCs were able to travel to draining lymph nodes, where they preferentially interacted with APCs. To couple cysteine-containing antigens to the surface of the MCs, a new polymer was synthesized with a terminal pyridyl disulfide (PDS), forming PDS-PEG-bl-PPS-benzyl. When mice were immunized in conjunction with free CpG as an adjuvant, ovalbumin-conjugated MCs (MC-Ova) generated more (2.4-fold) Ova-specific CD8(+) T cells in the blood and higher (1.7-fold) interferon-gamma levels from splenocytes upon restimulation than in mice immunized with free Ova and CpG. When comparing this MC platform to our PEG-PPS NPs with disulfide-linked Ova, no significant differences were found in the measured responses. These results indicate that PDS-functionalized MCs are efficient antigen delivery vehicles that enhance immune responses compared to immunization with free protein.
Subject(s)
Antigens/administration & dosage , Disulfides/chemistry , Lymphatic Vessels/metabolism , Micelles , Polymers , Pyridines/chemistry , Animals , Injections, Intradermal , Mice , Mice, Inbred C57BL , Tissue DistributionABSTRACT
By delivering immunomodulatory drugs in vivo directly to lymph nodes draining an injection site, an opportunity exists to increase drug bioavailability to local immune cells. Importantly, particles smaller than 100 nm are efficiently transported through lymphatic vessels to draining lymph nodes. To investigate whether this approach could be used for local delivery of immunomodulatory drugs, amphiphilic poly(ethylene glycol)-bl-poly(propylene sulfide) (PEG-bl-PPS) block copolymers forming 50 nm micelles were used to encapsulate hydrophobic drugs. Micelle drainage was determined using fluorescent micelles and showed effective targeting of multiple immune cell subsets in lymph nodes. For functional studies of our formulations, two approaches were considered. To evaluate the efficacy of anti-inflammatory drug delivery, dendritic cell activation was shown to be prevented when mice were pretreated with micelles loaded with the glucocorticoid mometasone and then challenged with the TLR9 ligand, CpG. To evaluate whether immunosuppressive drug-loaded micelles were effective in prolonging MHC-mismatched allograft survival, BALB/c mice were treated for 14 consecutive days with drug-loaded micelles following transplantation of allogenic C57BL/6 tail skin. Micelles loaded with a mixture of rapamycin and tacrolimus prolonged allograft survival by 2-fold. Our results indicate that the drug-loaded micelle approach effectively targets the draining lymph nodes and exhibits proper immune regulation.
Subject(s)
Drug Carriers/chemistry , Immunosuppressive Agents/administration & dosage , Lymph Nodes/drug effects , Polyethylene Glycols/chemistry , Sirolimus/administration & dosage , Skin Transplantation , Sulfides/chemistry , Tacrolimus/administration & dosage , Animals , Anti-Inflammatory Agents/administration & dosage , Anti-Inflammatory Agents/therapeutic use , Dendritic Cells/drug effects , Dendritic Cells/immunology , Immunosuppressive Agents/therapeutic use , Lymph Nodes/cytology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Micelles , Mometasone Furoate , Pregnadienediols/administration & dosage , Pregnadienediols/therapeutic use , Sirolimus/therapeutic use , Skin Transplantation/immunology , Tacrolimus/therapeutic use , Transplantation, Homologous/immunologyABSTRACT
The objective of this study was to synthesize and characterize a thermally responsive polymer-metal nanocomposite system comprised of a solid gold nanoparticle core and thermally responsive interpenetrating polymer network (IPN) shell, which was surface functionalized or PEGylated with a covalently bound linear poly(ethylene glycol) chain layer. Gold nanoparticles (50 nm diameter) were prepared using standard gold chloride and citrate reduction method. These particles were then encapsulated inside of a polyacrylamide (PAAm)/poly(acrylic acid) (PAA) IPN shell via an in situ inverse emulsion polymerization. The surface of the nanocomposite system was then PEGylated via covalent grafting of a linear methoxy-PEG-N-hydroxysuccinimide (M.W. 3400) to the primary amine groups of the PAAm network. Scanning and transmission electron microscopy were used to confirm the successful synthesis and encapsulation of gold nanoparticles within the IPN shell. Dynamic light scattering was used to examine the temperature swelling response of the IPN particles. Zeta-potential analysis was used to confirm the successful PEGylation of the final nanocomposite system.
