Holistic Assessment of Covalently Labeled Core–Shell Polymeric Nanoparticles with Fluorescent Contrast Agents for Theranostic Applications

The successful development of degradable polymeric nanostructures as optical probes for use in nanotheranostic applications requires the intelligent design of materials such that their surface response, degradation, drug delivery and imaging properties are all optimized. In the case of imaging, optimization must result in materials that allow differentiation between unbound optical contrast agents and labeled polymeric materials as they undergo degradation. In this study, we have shown that use of traditional electrophoretic gel-plate assays for determination of the purity of dye-conjugated degradable nanoparticles is limited, due to polymer degradation characteristics. To overcome these limitations, we have outlined a holistic approach to evaluating dye-and peptide-polymer nanoparticle conjugation by utilizing steady-state fluorescence, anisotropy, and emission and anisotropy life-time decay profiles, through which nanoparticle-dye binding can be assessed independent of perturbations, such as those presented during the execution of electrolyte gel-based assays. This approach has been demonstrated to provide an overall understanding of the spectral signature-structure-function relationship, ascertaining key information on interactions between the fluorophore, polymer and solvent components that have a direct and measurable impact on the emissive properties of the optical probe. The use of these powerful techniques provides feedback that can be utilized to improve nanotheranostics by evaluating dye emissivity in degradable nanotheranostic systems, which has become increasingly important as modern platforms transition to architectures intentionally reliant on degradation and built-in environmental responses

Synthesis and In Vivo

Nanoparticles with tunable pharmacokinetics are desirable for various biomedical applications. Poly(ethylene glycol) (PEG) is well known to create “stealth” effects to stabilize and extend the blood circulation of nanoparticles. In this work, poly(carboxybetaine) (PCB), a new non-fouling polymer material, was incorporated as surface-grafted coatings, conjugated onto degradable shell crosslinked knedel-like nanoparticles (dSCKs) composed of poly(acrylic acid)- based shells and poly(lactic acid) (PLA) cores, to compare the in vivo pharmacokinetics to their PEG-functionalized analogs. A series of five dSCKs was prepared from amphiphilic block copolymers, having different numbers and lengths of either PEG or PCB grafts, by supramolecular assembly in water followed by shell crosslinking, and then studied by a lactate assay to confirm their core hydrolytic degradabilities. Each dSCK was also conjugated with 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) macrocyclic chelators and tyramine moieties to provide for (64)Cu and/or radiohalogen labeling. The high specific activity of (64)Cu radiolabeling ensured nanogram administration of dSCKs for in vivo evaluation of their pharmacokinetics. Biodistribution studies demonstrated comparable in vivo pharmacokinetic profiles of PCB-grafted dSCKs to their PEG-conjugated counterparts. These results indicated that PCB-functionalized dSCKs have great potential as a theranostic platform for translational research

A Simple and Efficient Synthesis of an Acid-Labile Polyphosphoramidate by Organobase-Catalyzed Ring-Opening Polymerization and Transformation to Polyphosphoester Ionomers by Acid Treatment

The direct synthesis of an acid-labile polyphosphoramidate by organobase-catalyzed ring-opening polymerization and an overall two-step preparation of polyphosphodiester ionomers (PPEI) by acid-assisted cleavage of the phosphoramidate bonds along the backbone of the polyphosphoramidate were developed in this study. The ultrafast organobase-catalyzed ring-opening polymerization of a cyclic phospholane methoxyethyl amidate monomer initiated by benzyl alcohol allowed for the preparation of well-defined polyphosphoramidates (PPA) with predictable molecular weights, narrow molecular weight distributions (PDI<1.10), and well-defined chain ends. Cleavage of the acid-labile phosphoramidate bonds on the polyphosphoramidate repeat units was evaluated under acidic conditions over a pH range of 1–5, and the complete hydrolysis produced polyphosphodiesters. The thermal properties of the resulting polyphosphoester ionomer acid and polyphosphoester ionomer sodium salt exhibited significant thermal stability. The parent PPA and both forms of the PPEIs showed low cytotoxicities toward HeLa cells and RAW 264.7 mouse macrophage cells. The synthetic methodology developed here has enriched the family of water-soluble polymers prepared by rapid and convenient organobase-catalyzed ring-opening polymerizations and straightforward chemical medication reactions, which are designed to be hydrolytically degradable and have promise for numerous biomedical and other applications

Synthesis, Characterization, and In Vivo

[Image: see text] The use of nebulizable, nanoparticle-based antimicrobial delivery systems can improve efficacy and reduce toxicity for treatment of multi-drug-resistant bacteria in the chronically infected lungs of cystic fibrosis patients. Nanoparticle vehicles are particularly useful for applying broad-spectrum silver-based antimicrobials, for instance, to improve the residence time of small-molecule silver carbene complexes (SCCs) within the lung. Therefore, we have synthesized multifunctional, shell cross-linked knedel-like polymeric nanoparticles (SCK NPs) and capitalized on the ability to independently load the shell and core with silver-based antimicrobial agents. We formulated three silver-loaded variants of SCK NPs: shell-loaded with silver cations, core-loaded with SCC10, and combined loading of shell silver cations and core SCC10. All three formulations provided a sustained delivery of silver over the course of at least 2–4 days. The two SCK NP formulations with SCC10 loaded in the core each exhibited excellent antimicrobial activity and efficacy in vivo in a mouse model of Pseudomonas aeruginosa pneumonia. SCK NPs with shell silver cation-load only, while efficacious in vitro, failed to demonstrate efficacy in vivo. However, a single dose of core SCC10-loaded SCK NPs (0.74 ± 0.16 mg Ag) provided a 28% survival advantage over sham treatment, and administration of two doses (0.88 mg Ag) improved survival to 60%. In contrast, a total of 14.5 mg of Ag(+) delivered over 5 doses at 12 h intervals was necessary to achieve a 60% survival advantage with a free-drug (SCC1) formulation. Thus, SCK NPs show promise for clinical impact by greatly reducing antimicrobial dosage and dosing frequency, which could minimize toxicity and improve patient adherence