Potential Applications of Conducting Polymers to Reduce Secondary Bacterial Infections among COVID-19 Patients: a Review

The COVID-19 pandemic is a motivation for material scientists to search for functional materials with valuable properties to alleviate the risks associated with the coronavirus. The formulation of functional materials requires synergistic understanding on the properties of materials and mechanisms of virus transmission and disease progression, including secondary bacterial infections that are prevalent in COVID-19 patients. A viable candidate in the struggle against the pandemic is antimicrobial polymer, due to their favorable properties of flexibility, lightweight, and ease of synthesis. Polymers are the base material for personal protective equipment (PPE), such as gloves, face mask, face shield, and coverall suit for frontliners. Conducting polymers (CPs) are polymers with electrical properties due to the addition of dopant in the polymer structure. The conductivity of polymers augments their antiviral and antibacterial properties. This review discusses the types of CPs and how their properties could be exploited to ward off bacterial infections in hospital settings, specifically in cases involving COVID-19 patients. This review also covers common CPs fabrication techniques. The key components to produce CPs at several possibilities to fit the current needs in fighting secondary bacterial infections are also discussed.

Development of an electrospun polycaprolactone/silk scaffold for potential vascular tissue engineering applications

Long-distance (⩾10 mm) arterial vascular defect injury was a massive challenge affecting human health. Compared with autologous transplantation, tissue-engineered scaffolds such as biocompatible silk fibroin (SF) scaffolds have been developed because they exhibit equivalent functional repair effects without adverse reactions. However, its mechanical strength and structural stability needed to be further improved to match the longer repair cycle of blood vessels while maintaining the original biological safety. Hence, we designed and prepared SF and hydrophobic polycaprolactone (PCL) composite microfibers by an improving electrospinning method. It was found that when the weight ratio of PCL to SF was 1: 1, a microfiber scaffold with high strength (6.16 N) and minimum degradability can be obtained. More importantly, compared with natural silk fibroin, the novel composite microfiber scaffolds can slightly inhibit cell infiltration and inflammation through co-culture with HUVECs in vitro and rabbit back transplantation in vivo. Furthermore, the fabricated scaffolds also demonstrated excellent structural stability in vivo because of the well-organized PCL doping in the structure. All these results indicated that the novel PCL/SF composite microfiber scaffolds were promising candidates for vascular tissue engineering applications.

Polyanilines as New Sorbents for Hydrocarbons Removal from Aqueous Solutions

Water remediation from hydrocarbons is crucial to reduce health risks. Numerous costly and, sometimes, sophisticated methods were proposed over the years. Herein, an innovative green procedure for porous polyanilines preparation is reported. Polyaniline (PANI) was synthesized by three different approaches ranging from traditional to more eco-friendly ones. Thermal, optical and morphological features of the resulting materials were investigated along with their surface properties. Finally, PANIs were tested as sorbents for hydrocarbons removal from waterbodies. Although an overall fast and high sorption efficiency is always observed, the effective hydrocarbons abatement performed by 'green' PANIs is particularly welcome in the context of environmental protection. Moreover, the sorption efficiency retention after five-run recycling tests suggests potential applications in wastewater remediation.

Photocatalytic and Oxidative Synthetic Pathways for Highly Efficient PANI-TiO2 Nanocomposites as Organic and Inorganic Pollutant Sorbents

Polyaniline (PANI)-materials have recently been proposed for environmental remediation applications thanks to PANI stability and sorption properties. As an alternative to conventional PANI oxidative syntheses, which involve toxic carcinogenic compounds, an eco-friendly procedure was here adopted starting from benign reactants (aniline-dimer and H₂O₂) and initiated by ultraviolet (UV)-irradiated TiO₂. To unlock the full potential of this procedure, we investigated the roles of TiO₂ and H₂O₂ in the nanocomposites synthesis, with the aim of tailoring the properties of the final material to the desired application. The nanocomposites prepared by varying the TiO₂:H₂O₂:aniline-dimer molar ratios were characterized for their thermal, optical, morphological, structural and surface properties. The reaction mechanism was investigated via mass analyses and X-ray photoelectron spectroscopy. The nanocomposites were tested on both methyl orange and hexavalent chromium removal. A fast dye-sorption was achieved also in the presence of interferents and the recovery of the dye was obtained upon eco-friendly conditions. An efficient Cr(VI) abatement was obtained also after consecutive tests and without any regeneration treatment. The fine understanding of the reaction mechanism allowed us to interpret the pollutant-removal performances of the different materials, leading to tailored nanocomposites in terms of maximum sorption and reduction capability upon consecutive tests even in simulated drinking water.

Conductive Bicomponent Fibers Containing Polyaniline Produced via Side-by-Side Electrospinning

In this study, using a barbed Y-connector as the spinneret, camphoric acid (CSA) doped polyaniline (PANI) and polyethylene oxide (PEO) were electrospun into side-by-side bicomponent fibers. Fiber mats obtained from this side-by-side spinneret were compared with those mats electrospun from blended PEO and PANI in terms of fiber morphology, electrical conductivity, thermal stability, mechanical properties, and relative resistivity under tensile strain. The influence of different content ratio of insulating PEO (3/4/5 w/v% to solvent) and conductive PANI-CSA (1.5/2.5/3.5 w/v% to solvent) on the abovementioned properties was studied as well. Results showed that this side-by-side spinning was capable of overcoming the poor spinnability of PANI to produce fibers with PEO carrying PANI on the surface of the bicomponent fibers, which demonstrated higher electrical conductivity than blends. Although the addition of PANI deteriorated mechanical properties for both side-by-side and blended fibers when compared to the pure PEO fibers, the side-by-side fibers showed much better fiber strength and elongation than blends. In addition, the superior ductility and decent relative electrical resistivity of the side-by-side fibers imparted them great potential for flexible sensor applications.

Polyaniline (PANI): an innovative support for sampling and removal of VOCs in air matrices

Polyaniline (PANI)-based materials for both removal and sampling of volatile organic compounds (VOCs) from air by rapid adsorption/desorption processes have been developed. The polymer was synthesized in form of emeraldine as both salt and base using different synthetic approaches, a traditional one and a "green" one. VOCs adsorption/desorption efficiency was evaluated for all the materials analyzing the desorbed VOCs fractions by GC/MS technique and obtaining results similar to the presently adopted method employing commercial activated carbon. Most important, in this work it has been demonstrated for the first time that the use of PANI-based sorbents allowed the substitution of the toxic CS₂, recommended in official methods, with the less hazardous CH₃OH as the VOCs extraction solvent. Moreover, a complete regeneration of the polymers could be realized by a few rapid washing steps. Finally, the best PANI-based material was subjected to recycling tests thereby showing a high adsorption/desorption efficiency retention up to four runs.

Triply green polyaniline: UV irradiation-induced synthesis of a highly porous PANI/TiO2 composite and its application in dye removal

An eco-friendly synthesis of polyaniline/TiO₂ composites with good crystallinity and tailored morphology is reported for dye removal from an aqueous matrix.