Synthetic polymer nanoparticles conjugated with FimH(A) from E. coli pili to emulate the bacterial mode of epithelial internalization.

Amphiphilic block copolymer nanoparticles are conjugated with uropathogenic Escherichia coli type 1 pilus adhesin FimH(A) through amidation chemistry to enable bladder epithelial cell binding and internalization of the nanoparticles in vitro.

Paclitaxel-loaded SCK nanoparticles: an investigation of loading capacity and cell killing abilities in vitro.

Block copolymer nanoparticles having two different hydrodynamic diameters (120 nm vs 50 nm) and core diameters (60 nm vs 20 nm) with variable paclitaxel loading (5 to 20 wt % with respect to polymer weight, 4.4 µg/mL to 21.7 µg/mL paclitaxel concentrations in ultrapure water) were prepared for their in vitro cytotoxicity evaluation. Empty nanoparticles did not show any inherent cytotoxicity even at their highest concentration, whereas paclitaxel-loaded nanoparticles resulted in IC50 values that were better than free paclitaxel at 2 h (0.021 µM vs 0.046 µM) incubation periods, and approximately equal to free paclitaxel at 72 h (0.004 µM vs 0.003 µM) continuous incubation. Confocal fluorescence microscopy images demonstrated that the drug-loaded nanoparticles internalized into KB cells within 2 h and released their payload, resulting in cytotoxicity as evident from the fragmented nuclei present. Functionalization of the nanoparticle surfaces with poly(ethylene oxide) (2 kDa PEO, 5 PEO per block copolymer chain) did not affect the loading of paclitaxel or cell kill ability. No free paclitaxel was found in these nanoparticle formulations indicated by analytical assays.

Multicompartment polymer nanostructures with ratiometric dual-emission pH-sensitivity.

Pyrazine-labeled multicompartment nanostructures are shown to exhibit enhanced pH-responsive blue-shifted fluorescence emission intensities compared to their simpler core-shell spherical analogs. An amphiphilic linear triblock terpolymer of ethylene oxide, N-acryloxysuccinimide, and styrene, PEO(45)-b-PNAS(105)-b-PS(45), which lacks significant incompatibility for the hydrophobic block segments and undergoes gradual hydrolysis of the NAS units, underwent supramolecular assembly in mixtures of organic solvent and water to afford multicompartment micelles (MCMs) with a narrow size distribution. The assembly process was followed over time and found to evolve from individual polymer nanodroplets containing internally phase segregated domains, of increasing definition, and ultimately to dissociate into discrete micelles. Upon covalent cross-linking of the MCMs with pH-insensitive pyrazine-based diamino cross-linkers, pH-responsive, photonic multicompartment nanostructures (MCNs) were produced. These MCNs exhibited significant enhancement of overall structural stability, in comparison with the MCMs, and internal structural tunability through the cross-linking chemistry. Meanwhile, the complex compartmentalized morphology exerted unique pH-responsive fluorescence dual-emission properties, indicating promise in ratiometric pH-sensing applications.

Treatment of otitis media by transtympanic delivery of antibiotics.

Otitis media is the most common reason U.S. children receive antibiotics. The requisite 7- to 10-day course of oral antibiotics can be challenging to deliver in children, entails potential systemic toxicity, and encourages selection of antimicrobial-resistant bacteria. We developed a drug delivery system that, when applied once to the tympanic membrane through the external auditory canal, delivers an entire course of antimicrobial therapy to the middle ear. A pentablock copolymer poloxamer 407-polybutylphosphoester (P407-PBP) was designed to flow easily during application and then to form a mechanically strong hydrogel on the tympanic membrane. U.S. Food and Drug Administration-approved chemical permeation enhancers within the hydrogel assisted flux of the antibiotic ciprofloxacin across the membrane. This drug delivery system completely eradicated otitis media from nontypable Haemophilus influenzae (NTHi) in 10 of 10 chinchillas, whereas only 62.5% of animals receiving 1% ciprofloxacin alone had cleared the infection by day 7. The hydrogel system was biocompatible in the ear, and ciprofloxacin was undetectable systemically (in blood), confirming local drug delivery and activity. This fast-gelling hydrogel could improve compliance, minimize side effects, and prevent systemic distribution of antibiotics in one of the most common pediatric illnesses, possibly minimizing the development of antibiotic resistance.

Shell crosslinked knedel-like nanoparticles for delivery of cisplatin: effects of crosslinking.

Polymeric micelles and shell crosslinked knedel-like (SCK) nanoparticles were loaded with up to 48% (w/w) cisplatin. These spherical cisplatin-loaded nanoparticles displayed sustained platinum release over 5 days in PBS, enhanced stability over free cisplatin in aqueous milieu, and significant antitumor activity in vitro against two cancer cell lines.

Synthesis, characterization, and in vivo efficacy of shell cross-linked nanoparticle formulations carrying silver antimicrobials as aerosolized therapeutics.

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.

Facile Synthesis of Clickable, Water-soluble and Degradable Polyphosphoesters.

"Click" chemistry is a library of efficient and reliable reactions, which have been used to functionalize various classes of bio- and synthetic macromolecular systems for the incorporation of designed properties and functions. In this report, azide-alkyne Huisgen cycloaddition and thiol-yne reactions, two classical "click" chemistries, were employed to functionalize biodegradable, clickable polyphosphoester homopolymers and their water-soluble copolymers. A stable alkyne-functionalized phospholane monomer was synthesized, its organocatalyzed polymerization kinetics were evaluated, and the resulting (co)polymers were utilized to develop this facile method that provides the synthesis of clickable, water-soluble and degradable polyphosphoesters, which can be adapted for various applications.

Tuning core vs. shell dimensions to adjust the performance of nanoscopic containers for the loading and release of doxorubicin.

Detailed studies were performed to probe the effects of the core and shell dimensions of amphiphilic, shell crosslinked, knedel-like polymer nanoparticles (SCKs) on the loading and release of doxorubicin (DOX), a widely-used chemotherapy agent, in aqueous buffer, as a function of the solution pH. Effects of the nanoparticle composition were held constant, by employing SCKs constructed from a single type of amphiphilic diblock copolymer, poly(acrylic acid)-b-polystyrene (PAA-b-PS). A series of four SCK nanoparticle samples, ranging in number-average hydrodynamic diameter from 14-30 nm, was prepared from four block copolymers having different relative block lengths and absolute degrees of polymerization. The ratios of acrylic acid to styrene block lengths ranged from 0.65 to 3.0, giving SCKs with ratios of shell to core volumes ranging from 0.44 to 2.1. Although the shell thicknesses were calculated to be similar (1.5-3.1 nm by transmission electron microscopy (TEM) calculations and 3.5-4.9 nm by small angle neutron scattering (SANS) analyses), two of the SCK nanoparticles had relatively large core diameters (19±2 and 20±2 nm by TEM; 17.4 and 15.3 nm by SANS), while two had similar, smaller core diameters (11±2 and 13±2 nm by TEM; 9.0 and 8.9 nm by SANS). The SCKs were capable of being loaded with 1500-9700 DOX molecules per each particle, with larger numbers of DOX molecules packaged within the larger core SCKs. Their shell-to-core volume ratio showed impact on the rates and extents of release of DOX, with the volume occupied by the poly(acrylic acid) shell relative to the volume occupied by the polystyrene core correlating inversely with the diffusion-based release of DOX. Given that the same amount of polymer was used to construct each SCK sample, SCKs having smaller cores and higher acrylic acid vs. styrene volume ratios were present at higher concentrations than were the larger core SCKs, and gave lower final extents of release., Higher final extents of release and faster rates of release were observed for all DOX-loaded particle samples at pH 5.0 vs. pH 7.4, respectively, ca. 60% vs. 40% at 60 h, suggesting promise for enhanced delivery within tumors and cells. By fitting the data to the Higuchi model, quantitative determination of the kinetics of release was made, giving rate constants ranging from 0.0431 to 0.0540 h⁻¹/² at pH 7.4 and 0.106 to 0.136 h⁻¹/² at pH 5.0. In comparison, the non-crosslinked polymer micelle analogs exhibited rate constants for release of DOX of 0.245 and 0.278 h⁻¹/² at pH 7.4 and 5.0, respectively. These studies point to future directions to craft sophisticated devices for controlled drug release.

Tunable dual-emitting shell-crosslinked nano-objects as single-component ratiometric pH-sensing materials.

Dual-emitting photonic nano-objects that can sense changes in the environmental pH are designed based on shell-crosslinked micelles assembled from amphiphilic block copolymers and crosslinked with pH-insensitive chromophores. The chromophoric crosslinkers are tetra-functionalized pyrazine molecules that bear a set of terminal aliphatic amine groups and a set of anilino amine groups, which demonstrate morphology-dependent reactivities towards the poly(acrylic acid) shell domain of the nano-objects. The extent to which the anilino amine groups react with the nano-object shell is shown to affect the hypsochromic shift (blue-shift). The ratio of fluorescence intensity at 496 nm over that of 560 nm is dependent upon the solution pH. We report, herein, observations on the pH-sensitive dual-emission photophysical properties of rod-shaped or spherical nano-objects, whose shell domains offer two distinct platforms for amidation reactions to occur-through formation of activated esters upon addition of carbodiimide or pre-installation of activated ester groups. We demonstrate that physical manipulations (changes in morphology or particle dimensions) or chemical manipulations of the crosslinking reaction (the order of installation of activated esters) lead to fine tuning of dual-emission over ca. 60 nm in a physiologically relevant pH range. Rod-shaped shell-crosslinked nanostructures with poly(p-hydroxystyrene) core show blue-shift as a function of increasing pH while spherical shell-crosslinked nanostructures with polystyrene core and poly(ethylene oxide) corona exhibit blue-shift as a function of decreasing pH.

Evaluation of Isoprene Chain Extension from PEO Macromolecular Chain Transfer Agents for the Preparation of Dual, Invertible Block Copolymer Nanoassemblies.

Two RAFT-capable PEO macro-CTAs, 2 and 5 kDa, were prepared and used for the polymerization of isoprene which yielded well-defined block copolymers of varied lengths and compositions. GPC analysis of the PEO macro-CTAs and block copolymers showed remaining unreacted PEO macro-CTA. Mathematical deconvolution of the GPC chromatograms allowed for the estimation of the blocking efficiency, about 50% for the 5 kDa PEO macro-CTA and 64% for the 2 kDa CTA. Self assembly of the block copolymers in both water and decane was investigated and the resulting regular and inverse assemblies, respectively, were analyzed with DLS, AFM, and TEM to ascertain their dimensions and properties. Assembly of PEO-b-PIp block copolymers in aqueous solution resulted in well-defined micelles of varying sizes while the assembly in hydrophobic, organic solvent resulted in the formation of different morphologies including large aggregates and well-defined cylindrical and spherical structures.