Carbon Monoxide-Releasing Micelles for Immunotherapy

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Functionalization of Framboidal Phenylboronic Acid-Containing Nanoparticles via Aqueous Suzuki–Miyaura Coupling Reactions

Polymeric nanoparticles with reactive functional groups are an attractive platform for drug carriers that can be conjugated with drugs through a cleavable covalent linkage. Since the required functional groups vary depending on the drug molecule, there is a need for development of a novel post-modification method to introduce different functional groups to polymeric nanoparticles. We recently reported phenylboronic acid (PBA)-containing nanoparticles (BNP) with a unique framboidal morphology created via one-step aqueous dispersion polymerization. Since BNPs have high surface area due to their framboidal morphology and contain a high density of PBA groups, these particles can be used as nanocarriers for drugs that can bind to PBA groups such as curcumin and a catechol-bearing carbon monoxide donor. To further explore the potential of BNPs, in this article we report a novel strategy to introduce different functional groups to BNPs via the palladium-catalyzed Suzuki–Miyaura cross-coupling reaction between the PBA groups and iodo- and bromo-coupling partners. We developed a new catalytic system that efficiently catalyzes Suzuki–Miyaura reactions in water without the need for an organic solvent, as confirmed by NMR. Using this catalyst system, we show that BNPs can be functionalized with carboxylic acids, aldehyde, and hydrazide groups while keeping their original framboidal morphology as confirmed via IR, alizarin red assay, and TEM. Furthermore, the potential of the functionalized BNP in drug delivery applications was demonstrated by conjugating the hydrogen sulfide (H2S)-releasing compound anethole dithiolone to carboxylic acid-functionalized BNPs and show their H2S-releasing capability in cell lysate

Design and Synthesis of Polymeric Hydrogen Sulfide Donors

Hydrogen sulfide (H₂S) is a gaseous signaling molecule that has several important biological functions in the human body. Because of the difficulties of handling H₂S gas, small organic compounds that release H₂S under physiological conditions have been developed. The observed bioactivities of these H₂S donors have generally been directly correlated with their H₂S release properties. However, apart from H₂S release, these H₂S donors also exert biological effects by direct interaction with intracellular components within the cytoplasm after passive diffusion across cellular membranes. Here we report polymeric H₂S donors based on ADT–OH which would alter cellular trafficking of ADT–OH to minimize the unfavorable interactions with intracellular components. We designed and synthesized a poly­(ethylene glycol)–ADT (PEG–ADT) conjugate having ADT linked via an ether bond. Whereas ADT–OH significantly reduced cell viability in murine macrophages, the PEG–ADT conjugate did not show obvious cytotoxicity. The PEG–ADT conjugate released H₂S in murine macrophages but not in the presence of serum proteins. The PEG–ADT conjugate was taken up by the cell through the endocytic pathway and stayed inside endolysosomes, which is different from the small amphiphilic donor ADT–OH that can directly enter the cytoplasm. Furthermore, PEG–ADT was capable of potentiating LPS-induced inflammation. This polymeric H₂S donor approach may help to better understand the H₂S bioactivities of the H₂S donor ADT–OH

Reduction-Sensitive Tioguanine Prodrug Micelles

Colloidal drug and prodrug conjugates have unique targeting characteristics for tumor vasculature from the blood and for the lymphatics draining a tissue injection site. Tioguanine and tioguanine-generating prodrugs have been investigated as anticancer and immunosuppressive agents, including use in cancer immunotherapy. Recently we developed block copolymers of poly(ethylene glycol)-bl-poly(propylene sulfide) that self-assemble in aqueous solutions to form micellar structures. Since the polymers carry a free terminal thiol group resulting from the ring-opening polymerization of the propylene sulfide monomer, we sought to prepare prodrug block copolymers with tioguanine linked by a reduction-sensitive disulfide bond. The synthesis involved a disulfide exchange between the oxidized form of tioguanine and the polymer. Spectroscopic data is presented to support the proposed reaction. The polymers self-assembled when dispersed in water to form tioguanine prodrug micelles with a size range between 18 and 40 nm that released tioguanine in response to cysteine and serum as shown spectroscopically. In comparison with a poly(ethylene glycol) prodrug polymer, we show that the rate of tioguanine release can be controlled by changing the poly(propylene sulfide) block length and that the tioguanine remains bioactive with cultured cells

NMR spectra and electrochemical behavior of catechol-bearing block copolymer micelles

Here, we provide the NMR spectra and AFM data for antioxidant micelles prepared from amphiphilic PAM-PDA block copolymers composed of a poly(N-acryloyl morpholine) and a redox-active catechol-bearing block with different catechol content. We also provide details of the electrochemical analysis that showed micelles higher catechol content had a similar redox potential with the small catechol compound dopamine, but slowed down the redox reaction (Hasegawa et al., Polymer (in press))

Preparation of Well-Defined Ibuprofen Prodrug Micelles by RAFT Polymerization

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to treat acute pain, fever, and inflammation and are being explored in a new indication in cancer. Side effects associated with long-term use of NSAIDs such as gastrointestinal damage and elevated risk of stroke, however, can limit their use and exploration in new indications. Here we report a facile method to prepare well-defined amphiphilic diblock copolymer NSAID prodrugs by direct reversible addition-fragmentation transfer (RAFT) polymerization of the acrylamide derivative of ibuprofen (IBU), a widely used NSAID. The synthesis and self-assembling behavior of amphiphilic diblock copolymers (PEG-PIBU) having a hydrophilic poly(ethylene glycol) block and a hydrophobic IBU-bearing prodrug block were investigated Release profiles of IBU from the micelles by hydrolysis were evaluated. Furthermore, the antiproliferative action of the IBU-containing micelles in human cervical carcinoma (HeLa) and murine melanoma (B16-F10) cells was assessed

Dual Stimuli-Responsive Phenylboronic Acid-Containing Framboidal Nanoparticles by One-Step Aqueous Dispersion Polymerization

Phenylboronic acid-containing nanomaterials have found applications in various fields including biomedical engineering due to their unique stimuli-responsive characteristics. Contrary to the many reports on spherical nanoparticles, we are interested in nanostructures with different morphology which could potentially exhibit additional morphology-related effects. Here, phenylboronic acid-containing nanoparticles (PBANPs) in the size range of 80–250 nm in diameter were synthesized via aqueous dispersion polymerization of <i>N</i>-acryloyl-3-aminophenyl­boronic acid (PBAAM) using methoxy poly­(ethylene glycol) acrylamide (PEGAM) as a polymerizable dispersant and <i>N</i>,<i>N</i>′-methylenebis­(acrylamide) (MBAM) as a cross-linker. Microscopic analysis revealed that PBANPs were clusters, composed of smaller primary nanoparticles of ∼20 nm in diameter, possessing a framboidal morphology. The size of the PBANPs was significantly affected by the concentrations of PBAAM and PEGAM. Furthermore, PBANPs showed reversible swelling behavior in response to the changes in pH and fructose concentration. PBANPs could be used for fructose detection by the PBA-Alizarin Red S displacement assay. The unique framboidal morphology together with the characteristic properties of phenylboronic acid groups may be useful in biosensing applications

Carbon Monoxide-Releasing Micelles for Immunotherapy

With the discovery of important biological roles of carbon monoxide (CO), the use of this gas as a therapeutic agent has attracted attention. However, the medical application of this gas has been hampered by the complexity of the administration method. To overcome this problem, several transition-metal carbonyl complexes, such as Ru(CO)(3)Cl(glycinate), [Ru(CO)(3)Cl-2](2), and Fe(eta(4)-2-pyrone)(CO)(3), have been used as CO-releasing molecules both in vitro and in vivo. We sought to develop micellar forms of metal carbonyl complexes that would display slowed diffusion in tissues and thus better ability to target distal tissue drainage sites. Specifically, we aimed to develop a new CO-delivery system using a polymeric micelle having a Ru(CO)(3)Cl(amino acidate) structure as a CO-releasing segment. The CO-releasing micelles were prepared from triblock copolymers composed of a hydrophilic poly(ethylene glycol) block, a poly(ornithine acrylamide) block bearing Ru(CO)(3)Cl(ornithinate) moieties, and a hydrophobic poly(n-butylacrylamide) block. The polymers formed spherical micelles in the range of 30-40 nm in hydrodynamic diameter. Further characterization revealed the high CO-loading capacity of the micelles. CO-release studies showed that the micelles were stable in physiological buffer and serum and released CO in response to thiol-containing compounds such as cysteine. The CO release of the micelles was slower than that of Ru(CO)(3)Cl(glycinate). In addition, the CO-releasing micelles efficiently attenuated the lipopolysaccharide-induced NF-kappa B activation of human monocytes, while Ru(CO)(3)Cl(glycinate) did not show any beneficial effects. Moreover, cell viability assays revealed that the micelles significantly reduced the cytotoxicity of the Ru(CO)(3)Cl(amino acidate) moiety. This novel CO-delivery system based on CO-releasing micelles may be useful for therapeutic applications of CO

Data in support of preparation and functionalization of a clickable polycarbonate monolith

This data article provides supplementary figures to the research article entitled, “Phase separation approach to a reactive polycarbonate monolith for “click” modifications” (Xin et al., Polymer, 2015, doi:10.1016/j.polymer.2015.04.008). Here, the nitrogen adsorption/desorption isotherms of the prepared porous polycarbonate monolith are shown to classify its inner structure and calculate the specific surface area. The monoliths were modified by using the thiol-ene click chemistry and the olefin metathesis, which was examined by contact angle measurements, FT-IR, solid state 13C NMR spectroscopy as well as thermogravimetric analysis

Dual Stimuli-Responsive Phenylboronic Acid-Containing Framboidal Nanoparticles by One-Step Aqueous Dispersion Polymerization

Phenylboronic acid-containing nanomaterials have found applications in various fields including biomedical engineering due to their unique stimuli-responsive characteristics. Contrary to the many reports on spherical nanoparticles, we are interested in nanostructures with different morphology which could potentially exhibit additional morphology-related effects. Here, phenylboronic acid-containing nanoparticles (PBANPs) in the size range of 80–250 nm in diameter were synthesized via aqueous dispersion polymerization of <i>N</i>-acryloyl-3-aminophenyl­boronic acid (PBAAM) using methoxy poly­(ethylene glycol) acrylamide (PEGAM) as a polymerizable dispersant and <i>N</i>,<i>N</i>′-methylenebis­(acrylamide) (MBAM) as a cross-linker. Microscopic analysis revealed that PBANPs were clusters, composed of smaller primary nanoparticles of ∼20 nm in diameter, possessing a framboidal morphology. The size of the PBANPs was significantly affected by the concentrations of PBAAM and PEGAM. Furthermore, PBANPs showed reversible swelling behavior in response to the changes in pH and fructose concentration. PBANPs could be used for fructose detection by the PBA-Alizarin Red S displacement assay. The unique framboidal morphology together with the characteristic properties of phenylboronic acid groups may be useful in biosensing applications