A sulfonated derivative of polybenzimidazole is reported, and its properties are analyzed in comparison with related polybenzimidazole proton‐conducting materials. Poly(2,5‐benzimidazole), poly(m‐phenylenebenzobisimidazole), and poly[m‐(5‐sulfo)‐phenylenebenzobisimidazole] were prepared by condensation of the corresponding monomers in polyphosphoric acid. Several adducts of these polymers with phosphoric acid were prepared. The resulting materials were characterized by chemical analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis; also, the dc conductivity of doped and undoped derivatives was measured. Similar to what has been observed for the commercial polybenzimidazole polymer (also examined here for comparison), the title polymers exhibit high thermal stability. Furthermore, their doping with phosphoric acid leads to a significant increase in conductivity from less than 10−11 Scm−1 for the undoped polymers to 10−4 Scm−1 (both at room temperature) for their acid‐loaded derivatives. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3703–3710, 2002

Preparation and characterization of membranes of poly͑2,5-benzimidazole͒ ͑ABPBI͒ ͑as thin as 20 m͒ for polymer electrolyte membrane fuel cells are reported. These membranes were prepared by solution casting and then impregnated in phosphoric acid baths. Their characterization included thermogravimetric analyses, conductivity measurements, Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. These membranes have high thermal stability and good proton conductivity at temperatures up to 200°C (6.2 ϫ 10 Ϫ2 S cm Ϫ1 at 150°C and 30% relative humidity͒, similar to the well-known commercial polybenzimidazole ͑PBI͒. ABPBI membrane-electrode assemblies ͑MEAs͒ using commercially available E-TEK Pt/C electrodes were tested in H 2 /O 2 cells, obtaining power densities similar to those of PBI MEAs studied here as reference at temperatures of up to 180°C, humidifying the reactants at room temperature.

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Polypyrrole (PPy) is of great potential importance due to its excellent conductive properties; however, a major obstacle to commercialization (like many synthetic metals) is its poor stability, especially to oxidation. Here is reported a new synthesis of PPy in the presence of the cobaltabisdicarbollide anion (see Figure), whose uniform distribution throughout the polymer leads to a dramatic improvement in the overoxidation threshold.

The encapsulation of mRNA in nanosystems as gene vaccines for immunotherapy purposes has experienced an exponential increase in recent years. Despite the many advantages envisaged within these approaches, their application in clinical treatments is still limited due to safety issues. These issues can be attributed, in part, to liver accumulation of most of the designed nanosystems and to the inability to transfect immune cells after an intravenous administration. In this context, this study takes advantage of the known versatile properties of the oligopeptide end-modified poly (β-amino esters) (OM-PBAEs) to complex mRNA and form discrete nanoparticles. Importantly, it is demonstrated that the selection of the appropriate end-oligopeptide modifications enables the specific targeting and major transfection of antigen-presenting cells (APC) in vivo, after intravenous administration, thus enabling their use for immunotherapy strategies. Therefore, with this study, it can be confirmed that OM-PBAE are appropriate systems for the design of mRNA-based immunotherapy approaches aimed to in vivo transfect APCs and trigger immune responses to fight either tumors or infectious diseases.

Of all the much hyped and pricy cancer drugs, the benefits from the promising siRNA small molecule drugs are limited. Lack of efficient delivery vehicles that would release the drug locally, protect it from degradation, and ensure high transfection efficiency, precludes it from fulfilling its full potential. This work presents a novel platform for local and sustained delivery of siRNA with high transfection efficiencies both in vitro and in vivo in a breast cancer mice model. siRNA protection and high transfection efficiency are enabled by their encapsulation in oligopeptide-terminated poly(β-aminoester) (pBAE) nanoparticles. Sustained delivery of the siRNA is achieved by the enhanced stability of the nanoparticles when embedded in a hydrogel scaffold based on polyamidoamine (PAMAM) dendrimer cross-linked with dextran aldehyde. The combination of oligopeptide-terminated pBAE polymers and biodegradable hydrogels shows improved transfection efficiency in vivo even when compared with the most potent commercially available transfection reagents. These results highlight the advantage of using composite materials for successful delivery of these highly promising small molecules to combat cancer.

abCationic polymers are promising delivery systems for RNAi due to their ease of manipulation, scale-up conditions and transfection efficiency. However, some properties, such as stability and targeting, remain challenging to overcome. In this report, different modifications in poly(β-amino ester) (pBAE) structures have been explored to overcome these limitations. Recent studies have demonstrated that hydrophobicity plays a key role in controlling electrostatic interactions of plasma proteins with nanoparticles. Results show that a slight increase in the polymer hydrophobicity increases its siRNA packaging capacity, stability, and transfection efficiency. Consequently, polyplexes prepared with these hydrophobic structures are functional after incubation times longer than 48 hours in serum-containing medium. In addition, newly designed polymers were end-modified using different oligopeptide moieties in order to confer cell-specificity, as previously reported. Therefore, it can be concluded that these newly optimized pBAE polymers present great potential as delivery vectors to specifically drive therapeutic RNA-based nucleic acids in a cell-specific manner under physiological conditions.