pH and ion-selective swelling behaviour of keratin and keratose 3D hydrogels

Investigation of adsorption properties of Periostracum serpentis as keratin-containing natural biowaste composite material for uranium

In this study, the interaction of waste snake skin (Periostracum serpentis), a keratin-based biowaste composite material, with uranyl ions, the predominant form of uranium in aqueous solutions, was investigated to determine whether it could be used as an adsorbent. SEM, FTIR, BET and EDX analyses were performed to elucidate the material's surface and structural properties. The effects of the amount of adsorbent, uranyl ion concentration, pH, temperature, and adsorption time were investigated to optimize uranium removal with this material. The results showed an adsorption capacity of 0.377 molkg-1. It was observed that the Elovich model determined the adsorption kinetics and the adsorption pH was maximum at approximately 4-5. It was found that adsorption was heat consuming, with increased orderliness and a spontaneous process. These results revealed that Periostracum serpentis, a waste material, is a potential adsorbent for removing and enriching uranium.

Composite Films Based on Linear Polyethyleneimine Polymer and Starch or Polysaccharides from DDGS: Synthesis, Characterization, and Antimicrobial Studies

Different films were synthesized from starch or polysaccharides extracted from distillers dried grains with soluble (DDGS) in combination with different percentages of linear polyethyleneimine (PEI) hydrochloride polymer to assess the mechanical and antimicrobial properties of the resulting composites. Moreover, a simple method for the extraction of the polysaccharide content from DDGS is reported. The materials obtained were characterized by ATR-FTIR, NMR, and XPS spectroscopy, swelling capacity, and by organic elemental analysis. In particular, the stability of the film prepared with only DDGS in copper ion solutions was improved by the incorporation of PEI. 13C HRMAS NMR studies evidenced the incorporation of the PEI polymer in the new films. Moreover, the release of PEI molecules from the films was studied by 1H NMR experiments in D2O to explain the antimicrobial properties of the PEI-based films against Staphylococcus aureus, with the DDGS-10% PEI films being the most active surface. Furthermore, the incorporation of copper ions into the different films enhanced their antimicrobial activity. Additionally, the starch-10% PEI film exhibited good swelling capacity in deionized water (~1500%), which decreased with the addition of salts (~250%). Instead, the DDGS-10% PEI film showed low swelling capacity in deionized water (~80%), with this capacity increasing with the addition of salts (~250%). The mechanical properties of the films improved considerably when 3% PEI was used.

Triblock Superabsorbent Polymer Nanocomposites with Enhanced Water Retention Capacities and Rheological Characteristics

Superabsorbent polymers (SAPs) are useful polymers in a wide range of application fields ranging from the hygiene industry to construction and agriculture. As versatility and high water absorption capacity are their important merits, SAPs usually suffer from low water retention capacity (fast release) and weak mechanical properties. To address these drawbacks, a set of new superabsorbent polymer-Halloysite nanotube (HNT) nanocomposites was synthesized via free radical polymerization of acrylamide, 2-acrylamido-2-methylpropane-1-sulfonic acid, and acrylic acid in the presence of vinyltrimethoxysilane (VTMS) as the crosslinker. FTIR and TGA characterizations confirm the polymerization of SAP and successful incorporation of HNTs into the SAP polymer matrix. The effect of the HNT nanofiller amount in the nanocomposite polymer matrix was investigated with swelling-release performance tests, crosslink density calculations, and rheology measurements. It was found that equilibrium swelling ratios are correlated and therefore can be tuned via the crosslink densities of nanocomposites, while water retention capacities are governed by storage moduli. A maximum swelling of 537 g/g was observed when 5 wt % HNT was incorporated, in which the crosslink density is the lowest. Among the SAP nanocomposites prepared, the highest storage modulus was observed when 1 wt % of nanofiller was incorporated, which coincides with the nanocomposite with the longest water retention. The water release duration of SAPs was prolonged up to 27 days with 1% HNT addition in parallel with the achieved maximum storage modulus. Finally, three different incorporation mechanisms of the HNT nanofiller into the SAP nanocomposite structure were proposed and confirmed with rheology measurements. This study provides a rapid synthesis method for SAP nanocomposites with enhanced water retention capacities and explains the relationship between swelling and crosslink density and water retention and mechanical properties of SAP nanocomposites.

Smart pH-Responsive Polyaniline-Coated Hollow Polymethylmethacrylate Microspheres: A Potential pH Neutralizer for Water Purification Systems

Smart materials with potential pH controllability are gaining widespread concern due to their versatile applicability in water purification systems. A study presented here demonstrates a successful synthesis of smart pH-responsive polyaniline (PANI)-coated hollow polymethylmethacrylate microspheres (PHPMs) using a combination of solvent evaporation and in situ coating techniques. The material was characterized by using conventional techniques. Images recorded by an optical microscope displayed clear evidence in support of the coating, which was further supported by the SEM images. Surface roughness due to the coating was distinct in the SEM images. The PANI coating has enabled the microsphere to effectively neutralize the pH of water in water purification systems, which is very important in tackling the excessive acidic or basic problem of water resources. This study introduces a simple, facile, and cost-effective synthetic route to develop polyaniline-coated hollow polymethylmethacrylate microspheres with high performance as a pH-responsive material for water purification. The low density of the material and relatively large surface area compared to conventionally used chemicals further enhance the application prospect of the material.

Effect of varied hair protein fractions on the gel properties of keratin/chitosan hydrogels for the use in tissue engineering

Keratin/chitosan composite is a readily available source for a hybrid hydrogel in tissue engineering. While human hair keratins could provide biological functions, chitosan could further enhance the mechanical strength of the hybrid hydrogels. However, hair keratin is a group of natural proteins, and the uncontrolled hair protein contents in a hydrogel may lead to the batch-to-batch inconsistent gel properties. The purpose of this study was to investigate the role of hair protein composition, including the keratin-associated proteins (KAPs, 6-30 kDa) and keratin intermediate filaments (KIFs, 45-60 kDa) on gel characteristics of the keratin/chitosan hydrogel. The various compressive and tensile modulus of the gel was observed based on the selection of different protein fractions as the significant gel components. These results thus suggest a straightforward method of preparing hair keratin/chitosan hydrogel with much more controllable gel properties by merely modulating the KAPs/KIFs ratios in a gel.

Dual adsorbent-photocatalytic keratin–TiO2 nanocomposite for trimethoprim removal from wastewater

A keratin hydrogel with immersed TiO₂ nanoparticles was developed for the adsorption-photocatalytic degradation of the emerging pollutant trimethoprim.