Linear Polyethyleneimine-Based and Metal Organic Frameworks (DUT-67) Composite Hydrogels as Efficient Sorbents for the Removal of Methyl Orange, Copper Ions, and Penicillin V.

This research explores the integration of DUT-67 metal organic frameworks into polyethyleneimine-based hydrogels to assemble a composite system with enough mechanical strength, pore structure and chemical affinity to work as a sorbent for water remediation. By varying the solvent-to-modulator ratio in a water-based synthesis path, the particle size of DUT-67 was successfully modulated from 1 µm to 200 nm. Once DUT-67 particles were integrated into the polymeric hydrogel, the composite hydrogel exhibited enhanced mechanical properties after the incorporation of the MOF filler. XPS, NMR, TGA, FTIR, and FT Raman studies confirmed the presence and interaction of the DUT-67 particles with the polymeric chains within the hydrogel network. Adsorption studies of methyl orange, copper(II) ions, and penicillin V on the composite hydrogel revealed a rapid adsorption kinetics and monolayer adsorption according to the Langmuir's model. The composite hydrogel demonstrated higher adsorption capacities, as compared to the pristine hydrogel, showcasing a synergistic effect, with maximum adsorption capacities of 473 ± 21 mg L-1, 86 ± 6 mg L-1, and 127 ± 4 mg L-1, for methyl orange, copper(II) ions, and penicillin V, respectively. This study highlights the potential of MOF-based composite hydrogels as efficient adsorbents for environmental pollutants and pharmaceuticals.

Films of Poly(Hydroxybutyrate) (PHB) and Copper with Antibacterial Activity.

Poly(3-hydroxybutyrate), PHB, is a hydrophobic biopolymer with good mechanical and barrier properties. However, neat PHB is a semicrystalline polymer with a relative high degree of crystallinity and poor film properties. In this work, this biopolymer was plasticized with glycerol tributyrate and functionalized with copper (II) sulfate, allowing us to obtain biodegradable antimicrobial flexible films. Films with the minimum inhibitory concentration (MIC) of copper (II) sulfate presented a higher roughness than neat PHB films. The presence of plasticizer significantly improved the copper sulfate diffusion process, which was evidenced by a greater inhibition halo for plasticized materials compared to unplasticized ones, at the same salt concentration. Plasticized PHB with 2.5% copper (II) sulfate inhibited both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomona aeruginosa) bacteria, as determined by the bacterial inhibition halo. In addition, neat PHB films and PHB containing copper (II) sulfate did not show in vitro cytotoxicity in the L-929 cell line. Thus, plasticized PHB functionalized with copper (II) sulfate can be used as biodegradable antimicrobial flexible films for different applications.

Recycling of hyoscyamine 6ß-hydroxylase for the in vitro production of anisodamine and scopolamine.

The tropane alkaloids hyoscyamine, anisodamine, and scopolamine are extensively used medicines. In particular, scopolamine has the greatest value in the market. Hence, strategies to enhance its production have been explored as an alternative to traditional field-plant cultivation. In this work, we developed biocatalytic strategies for the transformation of hyoscyamine into its products utilizing a recombinant Hyoscyamine 6ß-hydroxylase (H6H) fusion protein to the chitin-binding domain of the chitinase A1 from Bacillus subtilis (ChBD-H6H). Catalysis was carried out in batch, and recycling of H6H constructions was performed via affinity-immobilization, glutaraldehyde crosslinking, and adsorption-desorption of the enzyme to different chitin matrices. ChBD-H6H utilized as free enzyme achieved complete conversion of hyoscyamine in 3- and 22-h bioprocesses. Chitin particles demonstrated to be the most convenient support for ChBD-H6H immobilization and recycling. Affinity-immobilized ChBD-H6H operated in a three-cycle bioprocess (3 h/cycle, 30 °C) yielded in the first and third reaction cycle 49.8% and 22.2% of anisodamine and 0.7% and 0.3% of scopolamine, respectively. However, glutaraldehyde crosslinking decreased enzymatic activity in a broad range of concentrations. Instead, the adsorption-desorption approach equaled the maximal conversion of the free enzyme in the first cycle and retained higher enzymatic activity than the carrier-bound strategy along the consecutive cycles. The adsorption-desorption strategy permitted the reutilization of the enzyme in a simple and economical manner while exploiting the maximal conversion activity displayed by the free enzyme. This approach is valid since other enzymes present in the E. coli lysate do not interfere with the reaction. KEY POINTS: • A biocatalytic system for anisodamine and scopolamine production was developed. • Affinity-immobilized ChBD-H6H in ChP retained catalytic activity. • Enzyme-recycling by adsorption-desorption strategies improves product yields.

Feasibility of Valorization of Post-Consumer Recycled Flexible Polypropylene by Adding Fumed Nanosilica for Its Potential Use in Food Packaging toward Sustainability.

The food industry has a current challenge of increasing the recycling of post-consumer plastics to reduce plastic waste towards a circular economy, especially flexible polypropylene, which is highly demanded in food packaging. However, recycling post-consumer plastics is limited because service life and reprocessing degrade their physical-mechanical properties and modify the migration of components from the recycled material to the food. This research evaluated the feasibility of valorization of post-consumer recycled flexible polypropylene (PCPP) by incorporating fumed nanosilica (NS). For this purpose, the effect of concentration and type (hydrophilic and hydrophobic) of NS on the morphological, mechanical, sealing, barrier and overall migration properties of PCPP films was studied. Incorporating NS improved Young's modulus and, more significantly, tensile strength at 0.5 wt% and 1 wt%, where a better particle dispersion was confirmed by EDS-SEM, but it diminished elongation at breakage of the films. Interestingly, NS tended to increase the seal strength of PCPP nanocomposite films more significantly at higher NS content, showing a seal failure of the adhesive peel type which is preferred for flexible packaging. NS at 1 wt% did not affect the water vapor and oxygen permeabilities of the films. Overall migration of PCPP and nanocomposites exceeded the limit value of 10 mg dm-2 allowed by European legislation at the studied concentrations of 1% and 4 wt%. Nonetheless, NS reduced the overall migration of PCPP from 17.3 to 15 mg dm-2 in all nanocomposites. In conclusion, PCPP with 1 wt% of hydrophobic NS presented an improved overall performance of the studied packaging properties.

Developing Post-Consumer Recycled Flexible Polypropylene and Fumed Silica-Based Nanocomposites with Improved Processability and Thermal Stability.

Collection and mechanical recycling of post-consumer flexible polypropylene packaging is limited, principally due to polypropylene being very light-weight. Moreover, service life and thermal-mechanical reprocessing degrade PP and change its thermal and rheological properties according to the structure and provenance of recycled PP. This work determined the effect of incorporating two fumed nanosilica (NS) types on processability improvement of post-consumer recycled flexible polypropylene (PCPP) through ATR-FTIR, TGA, DSC, MFI and rheological analysis. Presence of trace polyethylene in the collected PCPP increased the thermal stability of the PP and was significantly maximized by NS addition. The onset decomposition temperature raised around 15 °C when 4 and 2 wt% of a non-treated and organically modified NS were used, respectively. NS acted as a nucleating agent and increased the crystallinity of the polymer, but the crystallization and melting temperatures were not affected. The processability of the nanocomposites was improved, observed as an increase in viscosity, storage and loss moduli with respect to the control PCPP, which were deteriorated due to chain scission during recycling. The highest recovery in viscosity and reduction in MFI were found for the hydrophilic NS due to a greater impact of hydrogen bond interactions between the silanol groups of this NS and the oxidized groups of the PCPP.

Comparison of three cyclodextrins to optimize bisphenol A extraction from source water: Computational, spectroscopic, and analytical studies.

Computationally and spectroscopically assisted analytical comparative investigation into the extraction of bisphenol A using three cyclodextrins, that is, α, ß, and γ respectively, were performed. A simple, self-tailored µ-solid-phase extraction podium was used to extract bisphenol A from water samples, and high-performance liquid chromatography-ultraviolet was used for the qualitative and quantitative analysis of bisphenol A. Density functional theory first principle calculations, attenuated total reflectance Fourier-transform infrared spectroscopy and Fourier-transform Raman spectroscopy data supports the analytical selection of ß-cyclodextrin as the adsorbent for bisphenol A extraction. Analytical optimization of various parameters including sample volume, sample pH, eluting solvent and its volume was performed to discover the most proper conditions for maximum extraction. Under the optimized conditions, a limit of detection value of 0.70 ng/ml and a limit of quantification value of 2.31 ng/ml was achieved with ß-cyclodextrin, with recovery (%) values over 98.40-102.50 in real source water samples. Overall, well assisted by comprehensive computational and spectroscopic studies, a novel, simple, sensitive and economic analytical method was developed for the extraction of bisphenol A from source water using cyclodextrin.

Solid phase extraction with rotating cigarette filter for determination of bisphenol A in source and drinking water: computational and analytical studies.

An ultrasound assisted solid phase extraction method using rotating cigarette filter is developed herein to preconcentrate and determine trace amount of bisphenol in source and drinking water. Qualitative and quantitative measurements were performed using high-performance liquid chromatography coupled with ultra violet detector. Sorbent-analyte interactions were thoroughly investigated computationally and experimentally using molecular dynamics simulations; and attenuated total reflectance Fourier transform infrared spectroscopy, and Raman spectroscopy, respectively. Various extraction parameters were investigated and optimized. Under the optimal conditions, the results were linear in a low scale range of 0.01-55 ng/mL with correlation coefficient of 0.9941 and a low limit of detection (0.04 ng/mL, signal/noise = 3:1). A good precision (intra-day relative standard deviation ≤ 6.05%, inter-day relative standard deviation ≤ 7.12%) and recovery (intra-day ≥ 98.41%, inter-day ≥ 98.04%)) are obtained. Finally, the proposed solid phase extraction method offered a low cost, simple, fast, and sensitive analytical method to determine trace amount of bisphenol A in source and drinking water samples with chromatographic detection.

Selective modulation of placental and fetal MDR transporters by chronic in utero exposure to NRTIs in Sprague-Dawley rats: Importance for fetoprotection.

Multidrug resistance (MDR) transporters present in placenta and fetal tissues reduce intracellular accumulation of their substrates. Consequently, induction of protein expression may further reduce toxic effects of specific xenobiotics. This work aimed to study whether sustained drug treatments in utero could modulate MDR transporters P-gp, BCRP, and MRP2 and thus impact their fetoprotective action. Pregnant Sprague-Dawley rats were daily treated by gavage with zidovudine (AZT, 60 mg/kg) or lamivudine (3TC, 30 mg/kg) from gestation day (GD) 11 to 20. On GD 21, DNA damage and MDR protein abundance were assessed by comet assay and western blotting, respectively. Moreover, a single IV dose of AZT or 3TC was administered on GD 21 and drug concentrations were measured in maternal blood and fetal liver by HPLC-UV. Chronic exposure to 3TC caused significantly higher DNA damage than AZT in fetal liver cells, whereas no differences were observed in maternal blood cells. Increased levels of BCRP protein were found in the placenta and fetal liver after AZT, but not 3TC, chronic in utero exposure. Contrarily, no modifications in the protein abundance of P-gp or MRP2 were found after sustained exposure to these drugs. The area under the curve of AZT in fetal liver was significantly lower in the AZT-pretreated rats than in the VEH or 3TC groups. Moreover, pre-administration of the BCRP inhibitor gefitinib (20 mg/kg, IP) increased AZT levels to the values observed in the VEH-treated group in this tissue. On the other hand, the disposition of 3TC in maternal blood or fetal liver was not modified after chronic treatment in either group. In conclusion, chronic exposure to AZT selectively induces BCRP expression in the placenta and fetal liver decreasing its own accumulation which may account for the lower DNA damage observed for AZT compared to 3TC in fetal liver cells.

Chitin/Metal-Organic Framework Composites as Wide-Range Adsorbent.

Composites based on chitin (CH) biopolymer and metal-organic framework (MOF) microporous nanoparticles have been developed as broad-scope pollutant absorbent. Detailed characterization of the CH/MOF composites revealed that the MOF nanoparticles interacted through electrostatic forces with the CH matrix, inducing compartmentalization of the CH macropores that led to an overall surface area increase in the composites. This created a micro-, meso-, and macroporous structure that efficiently retained pollutants with a broad spectrum of different chemical natures, charges, and sizes. The unique prospect of this approach is the combination of the chemical diversity of MOFs with the simple processability and biocompatibility of CH that opens application fields beyond water remediation.

Supramolecular effect of acetate on chitin gelling medium: Structural properties and protein interaction.

In this work, the influence of Sodium Acetate Trihydrate (SAT) on the gelling stage of a chitin hydrogel was studied. Characterization techniques, such as FTIR, Raman, solid-state NMR, Dielectric Spectroscopy, Small-angle X-ray scattering (SAXS), Wide-angle X-ray scattering (WAXS), and X-ray diffraction (XRD) were used to study the effect of SAT on the micro and nanostructure of the material in the wet, dry and freeze-dried states. It was demonstrated that the amount of SAT in the gelling solution can induce a variation in the supramolecular interaction among the polysaccharide chains, which leads to a change in the structural characteristics. In addition, it was observed that the polymer-water interactions are also altered by this structural ordering. Also, the affinity interaction with lysozyme was evaluated and an influence on the adsorption capacity was evidenced with the use of SAT. This could be an advance for biotechnological, biomedical, and food applications.

Characterization of the Copper Transporters from Lotus spp. and Their Involvement under Flooding Conditions.

Forage legumes are an important livestock nutritional resource, which includes essential metals, such as copper. Particularly, the high prevalence of hypocuprosis causes important economic losses to Argentinian cattle agrosystems. Copper deficiency in cattle is partially due to its low content in forage produced by natural grassland, and is exacerbated by flooding conditions. Previous results indicated that incorporation of Lotus spp. into natural grassland increases forage nutritional quality, including higher copper levels. However, the biological processes and molecular mechanisms involved in copper uptake by Lotus spp. remain poorly understood. Here, we identify four genes that encode putative members of the Lotus copper transporter family, denoted COPT in higher plants. A heterologous functional complementation assay of the Saccharomyces cerevisiae ctr1∆ctr3∆ strain, which lacks the corresponding yeast copper transporters, with the putative Lotus COPT proteins shows a partial rescue of the yeast phenotypes in restrictive media. Under partial submergence conditions, the copper content of L. japonicus plants decreases and the expression of two Lotus COPT genes is induced. These results strongly suggest that the Lotus COPT proteins identified in this work function in copper uptake. In addition, the fact that environmental conditions affect the expression of certain COPT genes supports their involvement in adaptive mechanisms and envisages putative biotechnological strategies to improve cattle copper nutrition.

Pectin-decorated magnetite nanoparticles as both iron delivery systems and protective matrices for probiotic bacteria.

The goal of this work was to investigate biophysical stability of iron-pectin nanoparticles and analyze the feasibility of using them as delivery systems for the probiotic strain Lactobacillus plantarum CIDCA 83114. Iron oxide (Fe3O4) nanoparticles were synthesized from 0.25M FeCl2/0.5 M FeCl3.6H2O, and coated with citrus pectins. Their physico-chemical properties [FTIR, X-ray diffraction (XRD), ζ-potential, particle size, SEM, TEM] and their effect on bacterial stabilization (viability after freeze-drying/storage, stability when exposed to simulated gastro-intestinal conditions) were assessed. XRD indicated the almost exclusive presence of magnetite crystalline phases. FTIR spectra confirmed the adsorption of pectin on magnetite nanoparticles surface. SEM and TEM images evidenced agglomerated nanoparticles, and a morphological surface change after adsorption of pectin. DLS and ζ-potential results proved the solvation of the ionizable groups in the hydrophilic network which induced chain expansion and agglomeration. Iron from nanoparticles demonstrated to be non-toxic for microorganisms up to 1.00 mg/mL. Simulated saliva and gastric solutions prevented nanoparticles from dissolution. The higher pH of the intestinal conditions (solvated -COO- and Fe-O- groups) facilitated the dispersion and partial dissolution of nanoparticles. Pectins adsorption on magnetite nanoparticles significantly enhanced electrostatic repulsion, which aided the solvation of ionized iron forms. The soluble species diffused out from the aggregates, being detected in the simulated intestinal fluid. Regarding bacterial viability, no decays were observed neither when pectin-decorated nanoparticles were exposed to simulated fluids nor when stored at 4 °C for 60 days. The composites engineered in this work appear as adequate delivery systems for probiotic bacteria, whose target is the gut.

Smart release of antimicrobial ZnO nanoplates from a pH-responsive keratin hydrogel.

A smart antibacterial biomaterial based on a keratin hydrogel with pH-dependent behavior and Zinc Oxide nanoplates as biocide agent has been developed. The pH of a chronic wound is basic due to bacterial metabolism. Originally shrank at acid pH, keratin hydrogels swell upon contact with a bacterial contaminated media leading to the release of the nanoparticles. The material has been thoroughly characterized by infrared spectroscopy, Raman, scanning electron microscope, swelling behavior, Differential scanning calorimetry, Small-angle X-ray scattering, rheology, antimicrobial activity and cytotoxicity. The results show that 5% of Zinc Oxide nanoparticles concentration is the optimum for wound dressing applications.

Continuous flow adsorption of ciprofloxacin by using a nanostructured chitin/graphene oxide hybrid material.

A novel nanostructured material was successfully developed by combining a chitin matrix with graphene oxide nanosheets (Chi:nGO) and then used for the continuous flow adsorption of ciprofloxacin. The spectroscopic characterization indicated that none covalent interaction between both components would be occurring and the introduction of nGO did not interfere in chitin nanostructure rearrangement during gelling and later drying. SEM images and Mercury Intrusion Porosimetry results showed a wide pore size distribution ranging from nano to micrometers. The continuous flow adsorption was observed to be dependent on the pH which affects the electrostatic interaction. The flow rate, Na+ concentration and water hardness were evaluated to describe the adsorption process. The resistance to alkali allowed to regenerate and reuse the column for subsequent adsorption cycles. Finally, ciprofloxacin spiked real water samples were assessed and the results confirmed that the medium pH was the main parameter that defines the adsorption behavior.

Induction of ABCG2/BCRP restricts the distribution of zidovudine to the fetal brain in rats.

Safety concerns for fetus development of zidovudine (AZT) administration as prophylaxis of vertical transmission of HIV persist. We evaluated the participation of the ATP-binding cassette efflux transporter ABCG2 in the penetration of AZT into the fetal brain and the relevance for drug safety. Oral daily doses of AZT (60mg/kg body weight) or its vehicle were administered between post gestational days 11 (E11) and 20 (E20) to Sprague-Dawley pregnant rats. At E21, animals received an intravenous bolus of 60mg AZT/kg body weight in the presence or absence of the ABCG2 inhibitor gefitinib (20mg/kg body weight, ip) and AZT in maternal plasma and fetal brain were measured by HPLC-UV. ABCG2 protein expression in placenta and fetal brain, as well as mitochondrial function and ultrastructure in fetal brain were also analyzed. In utero chronic exposure to AZT markedly induced ABCG2 expression in placenta and fetal brain whereas did not significantly alter mitochondrial functionality in the fetal brain. The area-under-the-concentration-time-curve of AZT significantly decreased in fetal brains isolated from AZT-exposed fetuses compared to control group, but this effect was abolished by ABCG2 inhibition. Our results suggest that the absence of mitochondrial toxicity in the fetal brain after chronic in utero administration of AZT could be attributed to its low accumulation in the tissue caused, at least in part, by ABCG2 overexpression. We propose that any interference with ABCG2 activity due to genetic, pathological or iatrogenic factors would increase the amount of AZT reaching the fetal brain, which could increase the risk of toxicity of this drug on the tissue.

Sustainable and smart keratin hydrogel with pH-sensitive swelling and enhanced mechanical properties.

Protein based hydrogels are a very interesting type of biomaterials with many probed strengths related to their source and chemical structure. Biocompatibility and biodegradability are accompanied by affordability when it comes to low cost sources. The main keratin source is agroindustrial waste, such as feathers, horns, hooves, hair and wool. Thus, the main cost of keratin hydrogels derives from their processing. Here is presented a new strategy for the obtaining of a keratin hydrogel with enhanced mechanical properties using low cost reagents. This keratin hydrogel is stiff enough to allow handling without special cares and also presenting a reversible pH-responsive behavior. The minimum swelling is observed at low pH due to a collapsed and disordered protein network with water tightly adsorbed to the hydrophilic sites. The swelling rises significantly above pH6 and the maximum swelling appears above pH8 where an expanded network allows water to enter to the pores.

Antimicrobial Activity of Starch Hydrogel Incorporated with Copper Nanoparticles.

In order to obtain an antimicrobial gel, a starch-based hydrogel reinforced with silica-coated copper nanoparticles (Cu NPs) was developed. Cu NPs were synthesized by use of a copper salt and hydrazine as a reducing agent. In order to enhance Cu NP stability over time, they were synthesized in a starch medium followed by a silica coating. The starch hydrogel was prepared by use of urea and water as plasticizers and it was treated with different concentrations of silica-coated copper nanoparticles (Si-Cu NPs). The obtained materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, scanning electron microscopy (SEM), and rheometry. FT-IR and EPR spectra were used for characterization of Cu NPs and Si-Cu NPs, confirming that a starch cap was formed around the Cu NP and demonstrating the stability of the copper nanoparticle after the silica coating step. SEM images showed Cu NP, Si-Cu NP, and hydrogel morphology. The particle size was polydisperse and the structure of the gels changed along with particle concentration. Increased NP content led to larger pores in starch structure. These results were in accordance with the rheological behavior, where reinforcement by the Si-Cu NP was seen. Antimicrobial activity was evaluated against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacterial species. The hydrogels were demonstrated to maintain antimicrobial activity for at least four cycles of use. A dermal acute toxicity test showed that the material could be scored as slightly irritant, proving its biocompatibility. With these advantages, it is believed that the designed Si-Cu NP loaded hydrogel may show high potential for applications in various clinical fields, such as wound dressings and fillers.

Innovative Immobilization Matrices.

We present a brief survey of some of the recent work of Professor Luis E. Díaz, performed together with his students and collaborators at the University of Buenos Aires. Dr Luis E. Díaz has been involved in research on biochemical and pharmaceutical sciences solving scientific and industry problems for over 40 years until he passed away. Prof. Díaz scientific interests included various topics from NMR spectroscopy to biomedicine but fundamentally he focused in various aspects of chemistry (analytical, organic, inorganic and environmental). This is not a complete survey but a sampling of prominent projects related to sol-gel chemistry with a focus on some of his recent publications.