ABSTRACT
Peptides have enormous potential as therapeutic agents for the treatment of infection, in immunomodulation and for other medical applications, but their hydrolytic degradation in biological fluids is a serious limitation to their in vivo performance. Here we demonstrate the potential utility of polyelectrolyte nanoparticle complexes of novel self-assembling anionic graft copolymers for protecting peptides from degradation in human plasma. The anionic graft copolymers are synthesized by covalently attaching pendent polyetheramine chains to poly(alkylacrylic acid) backbones by carbodiimide coupling. The peptide:copolymer nanocomplexes' particle size, zeta-potential, peptide binding, and controlled release of the peptide are shown to be dependent upon the pendent chain graft density, polymer backbone alkyl groups (propyl vs. methyl), and the nanocomplexes' electrostatic charge ratio. The nanocomplexes can provide substantial protection to the bound peptides from degradation in human plasma for at least 24 h and, in standard microbiological assays are shown to retain some or all of the peptide's antimicrobial activity against a clinically relevant strain of Staphylococcus aureus.
Subject(s)
Antimicrobial Cationic Peptides/administration & dosage , Biocompatible Materials/chemistry , Drug Delivery Systems , Polymers/chemistry , Antimicrobial Cationic Peptides/blood , Electrolytes/chemistry , Humans , Materials Testing , Nanoparticles/administration & dosage , Nanoparticles/chemistry , Particle Size , Staphylococcus aureus/drug effectsABSTRACT
In this work, living/controlled radical polymerization (LRP) is compared with conventional free radical polymerization in the creation of highly and weakly cross-linked imprinted poly(methacrylic acid-co-ethylene glycol dimethacrylate) networks. It elucidates, for the first time, the effect of LRP on the chain level and begins to explain why the efficiency of the imprinting process is improved using LRP. Imprinted polymers produced via LRP exhibited significantly higher template affinity and capacity compared with polymers prepared using conventional methods. The use of LRP in the creation of highly cross-linked imprinted polymers resulted in a fourfold increase in binding capacity without a decrease in affinity; whereas weakly cross-linked gels demonstrated a nearly threefold increase in binding capacity at equivalent affinity when LRP was used. In addition, by adjusting the double bond conversion, we can choose to increase either the capacity or the affinity in highly cross-linked imprinted polymers, thus allowing the creation of imprinted polymers with tailorable binding parameters. Using free radical polymerization in the creation of polymer chains, as the template-monomer ratio increased, the average molecular weight of the polymer chains decreased despite a slight increase in the double bond conversion. Thus, the polymer chains formed were shorter but greater in number. Using LRP neutralized the effect of the template. The addition of chain transfer agent resulted in slow, uniform, simultaneous chain growth, resulting in the formation of longer more monodisperse chains. Reaction analysis revealed that propagation time was extended threefold in the formation of highly cross-linked polymers when LRP techniques were used. This delayed the transition to the diffusion-controlled stage of the reaction, which in turn led to the observed enhanced binding properties, decreased polydispersity in the chains, and a more homogeneous macromolecular architecture.
Subject(s)
Free Radicals/chemistry , Molecular Imprinting , Polymerization , Acetates/chemistry , Acetates/isolation & purification , Adenine/analogs & derivatives , Adenine/chemistry , Adenine/isolation & purification , Cross-Linking Reagents/chemistry , Disulfiram/chemistry , Disulfiram/isolation & purification , Ethylene Glycols/chemical synthesis , Ethylene Glycols/chemistry , Gels/chemical synthesis , Gels/chemistry , Kinetics , Methacrylates/chemical synthesis , Methacrylates/chemistry , Nitriles/chemistry , Polymethacrylic Acids/chemical synthesis , Polymethacrylic Acids/chemistryABSTRACT
Molecular imprinting provides a rational design strategy for the development of controlled release drug delivery systems. We demonstrate that imprinting a network results in macromolecular memory for the template molecule, indicated by the two or more times greater partitioning into these networks as compared to non-imprinted networks. Partitioning of drug into networks synthesized from multiple functional monomers was 8 times greater than networks synthesized from single monomers. One-dimensional permeation studies showed that the gel with maximum incorporated chemical functionality had the lowest diffusion coefficient, which was at least an order of magnitude lower than all other gels studied. All imprinted networks had significantly lower diffusion coefficients than non-imprinted networks, in spite of comparable mesh sizes and equilibrium polymer volume fractions in the swollen state. This work also demonstrates molecular imprinting using a "living/controlled" polymerization strategy to enhance template loading/affinity and delay release in weakly crosslinked gels. Recognition studies revealed more than a 50% increase in template loading and dynamic template release studies showed that imprinting via "living" polymerization extends or delays the template release profile by two-fold over that of imprinting via conventional free-radical polymerization techniques and four-fold over the control network. The imprinted gel and imprinted gel prepared via "living/controlled" polymerization release profiles were less Fickian and moved toward zero-order release with profile coefficients of 0.68 and 0.70, respectively.
