Enhancement of MHC-I antigen presentation via architectural control of pH-responsive, endosomolytic polymer nanoparticles

Protein-based vaccines offer a number of important advantages over organism-based vaccines but generally elicit poor CD8(+) T cell responses. We have previously demonstrated that pH-responsive, endosomolytic polymers can enhance protein antigen delivery to major histocompatibility complex class I (MHC-I) antigen presentation pathways thereby augmenting CD8(+) T cell responses following immunization. Here, we describe a new family of nanocarriers for protein antigen delivery assembled using architecturally distinct pH-responsive polymers. Reversible addition-fragmentation chain transfer (RAFT) polymerization was used to synthesize linear, hyperbranched, and core-crosslinked copolymers of 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) that were subsequently chain extended with a hydrophilic N,N-dimethylacrylamide (DMA) segment copolymerized with thiol-reactive pyridyl disulfide (PDS) groups. In aqueous solution, polymer chains assembled into 25 nm micellar nanoparticles and enabled efficient and reducible conjugation of a thiolated protein antigen, ovalbumin. Polymers demonstrated pH-dependent membrane-destabilizing activity in an erythrocyte lysis assay, with the hyperbranched and cross-linked polymer architectures exhibiting significantly higher hemolysis at pH ≤ 7.0 than the linear diblock. Antigen delivery with the hyperbranched and cross-linked polymer architecture enhanced in vitro MHC-I antigen presentation relative to free antigen, whereas the linear construct did not have a discernible effect. The hyperbranched system elicited a four- to fivefold increase in MHC-I presentation relative to the cross-linked architecture, demonstrating the superior capacity of the hyperbranched architecture in enhancing MHC-I presentation. This work demonstrates that the architecture of pH-responsive, endosomolytic polymers can have dramatic effects on intracellular antigen delivery, and offers a promising strategy for enhancing CD8(+) T cell responses to protein-based vaccines.

Emerging methods for the fabrication of polymer capsules

Hollow polymer capsules are attracting increasing research interest due to their potential application as drug delivery vectors, sensors, biomimetic nano- or multi-compartment reactors and catalysts. Thus, significant effort has been directed toward tuning their size, composition, morphology, and functionality to further their application. In this review, we provide an overview of emerging techniques for the fabrication of polymer capsules, encompassing: self-assembly, layer-by-layer assembly, single-step polymer adsorption, bio-inspired assembly, surface polymerization, and ultrasound assembly. These techniques can be applied to prepare polymer capsules with diverse functionality and physicochemical properties, which may fulfill specific requirements in various areas. In addition, we critically evaluate the challenges associated with the application of polymer capsules in drug delivery systems.

Poly(methacrylic acid)-based AB and ABC block copolymer nano-objects prepared via RAFT alcoholic dispersion polymerization

A series of well-defined amphiphilic methacrylic AB diblock and ABC triblock copolymers are synthesized via polymerization-induced self-assembly using an alcoholic dispersion polymerization formulation.

Polymerization-induced self-assembly: ethanolic RAFT dispersion polymerization of 2-phenylethyl methacrylate

Reversible addition-fragmentation chain transfer (RAFT) radical dispersion polymerization (RAFTDP) has been employed to polymerize 2-phenylethyl methacrylate (PEMA) using poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) macromolecular chain transfer agents (macro-CTAs) of varying average degree of polymerization (X̄_n).

Manganese(iii) acetylacetonate initiated RAFT polymerizations: an alternative and versatile RAFT initiator

Manganese(iii) acetylacetonate (Mn(acac)₃) was demonstrated to be a versatile and superior RAFT initiator for different kinds of monomers, RAFT agents and noticeably, for a wide range of temperatures.

RAFT copolymerization of acid chloride-containing monomers

Controlled radical copolymerization of acid chloride-containing monomers via RAFT enabled direct synthesis of well-defined reactive polymers and their block polymers which can be readily functionalized further by postpolymerization modification.

Construction of Vinyl Polymer and Polyester or Polyamide Units in a Single Polymer Chain via Metal-catalyzed Simultaneous Chain- and Step-growth Radical Polymerization of Various Monomers

Metal-catalyzed simultaneous chain- and step-growth radical polymerization was examined to combine common conjugated vinyl monomers, such as various acrylates and styrene, as chain-growth monomers and various ester- or amide-linked monomers bearing both an unconjugated C=C bond and an active C–Cl bond as step-growth monomers. The CuCl/1,1,4,7,10,10-hexamethyltriethylenetetramine-catalyzed copolymerization of alkyl acrylates and various step-growth monomers at a 1 : 1-monomer feed ratio resulted in almost linear random copolymers that consisted of vinyl polymer and polyester units. Additional functional groups, such as oxyethylene and disulfide units, can be introduced into the main chain using a step-growth monomer that possesses the functional units between the unconjugated C=C bond and the active C–Cl bond. Copolymerization at a higher feed ratio of chain-growth monomers, such as alkyl acrylates and styrene, can provide multiblock vinyl polymers connected to the functionalized step-growth monomer units.

New dialkoxyamine-trithiocarbonate for the synthesis of multiblock copolymers through in tandem RAFT/NMP

A new strategy for synthesizing multiblock copolymers comprising polystyrene, polyacrylates, poly(N-isopropylacrylamide), etc. is described.

Comparison of pseudo-living character of RAFT polymerizations conducted under homogeneous and heterogeneous conditions

Evidence is presented for (i) the greater pseudo-living character of RAFT dispersion polymerization compared to the equivalent solution polymerization and (ii) the presence of monomer-swollen micelles in the former formulation.

One pot synthesis of higher order quasi-block copolymer librariesviasequential RAFT polymerization in an automated synthesizer

The utility of automated high-throughput methods for the one pot synthesis of functional polymers of increased complexity is reported.

Synthesis of RAFT polymers as bivalent inhibitors of cholera toxin

We report a new strategy to develop low molecular weight (18–28 kDa) poly(N-acryloylmorpholine) (PNAM) polymers as bivalent inhibitors of cholera toxin (CT) using Reversible Addition–Fragmentation chain Transfer (RAFT) technology.

Inhibition of influenza virus in vivo by siRNA delivered using ABA triblock copolymer synthesized by reversible addition-fragmentation chain-transfer polymerization

AIM

Influenza virus remains a major threat, with outbreaks continuing to occur. Few treatment options are available and drug resistance can emerge rapidly. New drugs that can quickly be adapted to virus mutations are needed. Several highly effective siRNAs targeting influenza that inhibit virus replication are known; however, effective delivery of these siRNAs remains a challenge. The aim of this study was to demonstrate the safety and efficacy of ABA triblock copolymer-delivered siRNA to inhibit influenza virus replication in vivo.

MATERIALS & METHODS

We report on the delivery of a siRNA targeting the influenza virus in chicken embryos using an ABA triblock copolymer prepared by reversible addition-fragmentation chain-transfer polymerization, containing a central cationic block and two outer hydrophilic polyethylene glycol blocks.

RESULTS

A significant reduction of virus titer was observed with the polymer/anti-influenza siRNA complexes, whereas the control with polymer/control siRNA complexes showed no effect.

CONCLUSION

These data suggest that a reversible addition-fragmentation chain transfer-based siRNA delivery platform may be suitable for combating infectious diseases in vivo.

Precisely tunable engineering of sub-30 nm monodisperse oligonucleotide nanoparticles

Advancement of RNAi therapies is mainly hindered by the development of efficient delivery vehicles. The ability to create small size (<30 nm) oligonucleotide nanoparticles is essential for many aspects of the delivery process but is often overlooked. In this report, we describe diblock star polymers that can reproducibly complex double-stranded oligonucleotides into monodisperse nanoparticles with 15, 23, or 30 nm in diameter. The polymer-nucleic acid nanoparticles have a core-shell architecture with dense PEG brush coating. We characterized these nanoparticles using ITC, DLS, FRET, FCS, TIRF, and TEM. In addition to small size, these nanoparticles have neutral zeta-potentials, making the presented polymer architecture a very attractive platform for investigation of yet poorly studied polyplex size range for siRNA and antisense oligonucleotide delivery applications.