Chitosan-Based Beads Incorporating Inorganic-Organic Composites for Copper Ion Retention in Aqueous Solutions.

In recent years, there has been a challenging interest in developing low-cost biopolymeric materials for wastewater treatment. In the present work, new adsorbents, based on different types of chitosan (commercial, commercial chitin-derived chitosan and chitosan synthesized from shrimp shell waste) and inorganic-organic composites have been evaluated for copper ions removal. The efficacy of the synthesis of chitosan-based composite beads has been determined by studying various characteristics using several techniques, including FTIR spectroscopy, X-ray diffraction, porosimetry (N2 adsorption), and scanning electron microscopy (SEM). Adsorption kinetics was performed using different adsorption models to determine the adsorption behavior of the materials in the aqueous media. For all composite beads, regardless of the type of chitosan used, good capacity to remove copper ions from simulated waters was observed (up to 17 mg/g), which proves that the new materials hold potential for heavy metal retention. However, the adsorption efficiency was influenced by the type of chitosan used. Thus, for the series where commercial chitosan (CC) was used, the removal efficiency was approximately 29%; for the series with chitosan obtained from commercial chitin (SC), the removal efficiency was approximately 34%; for the series with chitosan enriched with CaCO3 (SH), the removal efficiency was approximately 52%.

Synergistic Sustained Drug-Release System Based on Immobilized Rhamnus frangula L. Phytoextract into Layered Double Hydroxide Covered by Biocompatible Hydrogel.

This work focuses on the synergetic effect obtained by immobilization of Rhamnus frangula L. (RfL) phytoextract in layered double hydroxides (LDHs) matrixes and their subsequent encapsulation into biocompatible hydrogels (HG). In this respect, the LDHs were used as hosts for the immobilization of the phytoextract by a reconstruction method, after which the LDHsRfL were embedded into biocompatible hydrogel (HG) matrixes, based on polyethylene glycol diacrylate (PEGDA), by a radical polymerization reaction. The resulted biocompatible hydrogel composites were characterized by modern methods, while the swelling and rheology measurements revealed that the HG composites steadily improved as the content of RfL phytoextract immobilized on LDHs (LDHsRfL) increased. The following in vitro sustained release of the RfL phytoextract was highlighted by measurements at pH 6.8, in which case the composite HGs with LDHsRfL presented an improved release behavior over the LDHsRfL, thus, underlining the synergistic effect of PEGDA network and LDH particles on the slow-release behavior. The kinetic models used in the RfL release from composite HGs clearly indicate that the release is diffusion controlled in all the cases. The final composite HGs described here may find applications in the pharmaceutical field as devices for the controlled release of drugs.

The Influence of Potassium Salts Phase Stabilizers and Binder Matrix on the Properties of Novel Composite Rocket Propellants Based on Ammonium Nitrate.

The environmental impact and availability of ingredients are vital for the new generation of rocket propellants. In this context, several novel composite propellants were prepared based on the "greener" oxidizer phase-stabilized ammonium nitrate (PSAN), a micronized aluminum-magnesium alloy fuel, iron oxide powder burn rate modifier, triethylene glycol dinitrate (TEGDN) energetic plasticizer and a polyurethane (PU) binder. The novelty of this study is brought by the innovative procedure of synthesizing and combining the constituents of these heterogeneous compositions to obtain high-performance "eco-friendly" rocket propellants. The polymorphism shortcomings brought by ammonium nitrate in these energetic formulations have been solved by its co-crystallization with potassium salts (potassium nitrate, potassium chromate, potassium dichromate, potassium sulphate, potassium chlorate and potassium perchlorate). Polyester-polyol blends, resulting from recycled post-consumer polyethylene terephthalate (PET) glycolysis, were utilized for the synthesis of the polyurethane binder, especially designed for this type of application. To adjust the energetic output and tailor the mechanical properties of the propellant, the energetic plasticizer TEGDN was also involved. The performance and safety characteristics of the novel composites were evaluated through various analytical techniques (TGA, DTA, XRD) and specific tests (rate of combustion, heat of combustion, specific volume, chemical stability, sensitivity to thermal, impact and friction stimuli), according to NATO standards, providing promising preliminary results for further ballistics investigations.

A Top-Down Procedure for Synthesizing Calcium Carbonate-Enriched Chitosan from Shrimp Shell Wastes.

Chitosan is used in medicine, pharmaceuticals, cosmetics, agriculture, water treatment, and food due to its superior biocompatibility and biodegradability. Nevertheless, the complex and relatively expensive extraction costs hamper its exploitation and, implicitly, the recycling of marine waste, the most abundant source of chitosan. In the spirit of developing environmental-friendly and cost-effective procedures, the present study describes one method worth consideration to deliver calcium-carbonate-enriched chitosan from shrimp shell waste, which proposes to maintain the native minerals in the structure of chitin in order to improve the thermal stability and processability of chitosan. Therefore, a synthesis protocol was developed starting from an optimized deacetylation procedure using commercial chitin. The ultimate chitosan product from shrimp shells, containing native calcium carbonate, was further compared to commercial chitosan and chitosan synthesized from commercial chitin. Finally, the collected data during the study pointed out that the prospected method succeeded in delivering calcium-carbonate-enriched chitosan with high deacetylation degree (approximately 75%), low molecular weight (Mn ≈ 10.000 g/ mol), a crystallinity above 59 calculated in the (020) plane, high thermal stability (maximum decomposition temperature over 300 °C), and constant viscosity on a wide range of share rates (quasi-Newtonian behavior), becoming a viable candidate for future chitosan-based materials that can expand the application horizon.

Molecularly Imprinted Ligand-Free Nanogels for Recognizing Bee Venom-Originated Phospholipase A2 Enzyme.

In this study, ligand-free nanogels (LFNGs) as potential antivenom mimics were developed with the aim of preventing hypersensitivity and other side effects following massive bee attacks. For this purpose, poly (ethylene glycol) diacrylate was chosen as a main synthetic biocompatible matrix to prepare the experimental LFNGs. The overall concept uses inverse mini-emulsion polymerization as the main route to deliver nanogel caps with complementary cavities for phospholipase A2 (PLA2) from bee venom, created artificially with the use of molecular imprinting (MI) technologies. The morphology and the hydrodynamic features of the nanogels were confirmed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. The following rebinding experiments evidenced the specificity of molecularly imprinted LFNG for PLA2, with rebinding capacities up to 8-fold higher compared to the reference non-imprinted nanogel, while the in vitro binding assays of PLA2 from commercial bee venom indicated that such synthetic nanogels are able to recognize and retain the targeted PLA2 enzyme. The results were finally collaborated with in vitro cell-viability experiments and resulted in a strong belief that such LFNG may actually be used for future therapies against bee envenomation.

Eco-Friendly Peelable Active Nanocomposite Films Designed for Biological and Chemical Warfare Agents Decontamination.

In the context of imminent threats concerning biological and chemical warfare agents, the aim of this study was the development of a new method for biological and chemical decontamination, employing non-toxic, film-forming, water-based biodegradable solutions, using a nano sized reagent together with bentonite as trapping agents for the biological and chemical contaminants. Bentonite-supported nanoparticles of Cu, TiO2, and Ag were successfully synthesized and dispersed in a polyvinyl alcohol (PVA)/glycerol (GLY) aqueous solution. The decontamination effectiveness of the proposed solutions was evaluated by qualitative and quantitative analytical techniques on various micro-organisms, with sulfur mustard (HD) and dimethyl methylphosphonate (DMMP) as contaminants. The results indicate that the peelable active nanocomposite films can be successfully used on contaminated surfaces to neutralize and entrap the hazardous materials and their degradation products. Mechanical and thermal characterization of the polymeric films was also performed to validate the decontamination solution's potential as peelable-film generating materials. The removal efficacy from the contaminated surfaces for the tested micro-organisms varied between 93% and 97%, while for the chemical agent HD, the highest decontamination factor obtained was 90.89%. DMMP was almost completely removed from the contaminated surfaces, and a decontamination factor of 99.97% was obtained.

Mitigating Antibiotic Resistance Genes in Wastewater by Sequential Treatment with Novel Nanomaterials.

Wastewater (WW) has been widely recognized as the major sink of a variety of emerging pathogens (EPs), antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs), which may disseminate and impact wider environments. Improving and maximizing WW treatment efficiency to remove these microbial hazards is fundamentally imperative. Despite a variety of physical, biological and chemical treatment technologies, the efficiency of ARG removal is still far from satisfactory. Within our recently accomplished M-ERA.NET project, novel functionalized nanomaterials, i.e., molecularly imprinted polymer (MIP) films and quaternary ammonium salt (QAS) modified kaolin microparticles, were developed and demonstrated to have significant EP removal effectiveness on both Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB) from WW. As a continuation of this project, we took the further step of exploring their ARG mitigation potential. Strikingly, by applying MIP and QAS functionalized kaolin microparticles in tandem, the ARGs prevalent in wastewater treatment plants (WWTPs), e.g., blaCTXM, ermB and qnrS, can be drastically reduced by 2.7, 3.9 and 4.9 log (copies/100 mL), respectively, whereas sul1, tetO and mecA can be eliminated below their detection limits. In terms of class I integron-integrase I (intI1), a mobile genetic element (MGE) for horizontal gene transfer (HGT), 4.3 log (copies/100 mL) reduction was achieved. Overall, the novel nanomaterials exhibit outstanding performance on attenuating ARGs in WW, being superior to their control references. This finding provides additional merit to the application of developed nanomaterials for WW purification towards ARG elimination, in addition to the proven bactericidal effect.

Poly(ß-cyclodextrin)-Activated Carbon Gel Composites for Removal of Pesticides from Water.

Pesticides are widely used in agriculture to increase and protect crop production. A substantial percentage of the active substances applied is retained in the soil or flows into water courses, constituting a very relevant environmental problem. There are several methods for the removal of pesticides from soils and water; however, their efficiency is still a challenge. An alternative to current methods relies on the use of effective adsorbents in removing pesticides which are, simultaneously, capable of releasing pesticides into the soil when needed. This reduces costs related to their application and waste treatments and, thus, overall environmental costs. In this paper, we describe the synthesis and preparation of activated carbon-containing poly(ß-cyclodextrin) composites. The composites were characterized by different techniques and their ability to absorb pesticides was assessed by using two active substances: cymoxanil and imidacloprid. Composites with 5 and 10 wt% of activated carbon showed very good stability, high removal efficiencies (>75%) and pesticide sorption capacity up to ca. 50 mg g-1. The effect of additives (NaCl and urea) was also evaluated. The composites were able to release around 30% of the initial sorbed amount of pesticide without losing the capacity to keep the maximum removal efficiency in sorption/desorption cycles.

Molecularly imprinted films and quaternary ammonium-functionalized microparticles working in tandem against pathogenic bacteria in wastewaters.

Despite major efforts to combat pollution, the presence of pathogenic bacteria is still detected in surface water, soil and even crops due to poor purification of domestic and industrial wastewaters. Therefore, we have designed molecularly imprinted polymer films and quaternary ammonium-functionalized- kaolin microparticles to target specifically Gram-negative bacteria (GNB) and Gram-positive bacteria (GPB) in wastewaters and ensure a higher purification rate by working in tandem. According to the bacteriological indicators, a reduction by 90 % was registered for GNB (total coliforms and Escherichia coli O157) and by 77 % for GPB (Clostridium perfringens) in wastewaters. The reduction rates were confirmed when using pathogen genetic markers to quantify particular types of GNB and GPB, like Salmonella typhimurium (reduction up to 100 %),Campylobacter jejuni (reduction up to 70 %), Enterococcus faecalis (reduction up to 81 %), Clostridium perfringens (reduction up to 97 %) and Shiga toxin-producing Escherichia coli (reduction up to 64 %). In order to understand the bactericidal activity of prepared films and microparticles, we have performed several key analyses such as Cryo-TEM, to highlight the auto-assembly mechanism of components during the films formation, and 29 Si/13 C CP/MAS NMR, to reveal the way quaternary ammonium groups are grafted on the surface of kaolin microparticles.

Composite Nanogels Based on Zeolite-Poly(ethylene glycol) Diacrylate for Controlled Drug Delivery.

This study presents the design of novel composites nanogels, based on poly(ethylene glycol) diacrylate and natural zeolite particles, that are able to act as materials with controlled drug delivery properties. Natural zeolite‒nanogels composite, with varying zeolite contents, were obtained by an inverse mini-emulsion technique and loaded with 5-fluorouracil, a widely used chemotherapeutic drug. Herein, the possibility of adjusting final properties by means of modifying the preparation conditions was investigated. The prepared composite nanogels are characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). In light of this tunable drug-loading capability, swelling behaviour, and cytotoxicity, these composite nanogels could be highly attractive as drug reservoirs.