Use of nanoparticle-coated bacteria for the bioremediation of organic pollution: A mini review

Nanoparticle (NP)-coated (immobilized) bacteria are an effective method for treating environmental pollution due to their multifarious benefits. This review collates a vast amount of existing literature on organic pollution treatment using NP-coated bacteria. We discuss the features of bacteria, NPs, and decoration techniques of NP-bacteria assemblies, with special attention given to the surface modification of NPs and connection mechanisms between NPs and cells. Furthermore, the performance of NP-coated bacteria was examined. We summarize the factors that affect bioremediation efficiency using coated bacteria, including pH, temperature, and agitation, and the possible mechanisms involving them are proposed. From future perspectives, suitable surface modification of NPs and wide application in real practice will make the NP-coated bacterial technology a viable treatment strategy.

Fabrication of glutathione functionalized self-assembled magnetite nanochains for effective removal of crystal violet and phenol red dye from aqueous matrix

A novel fabrication of magnetite (Fe₃O₄) nanochains, surface functionalized with glutathione (GSH), has been attempted through a basic wet reduction method, coalesced with oxidative etching for the removal of crystal violet (CV) and phenol red (PR) from an aqueous solution. The structural and functional characterizations of GSH@Fe₃O₄ MNPs were performed using SEM-EDX, DLS, XRD, and FTIR. The nanochain-structured adsorbent was found to have an average size of 24 ± 1.29 nm and a zeta potential value of - 6.44 mV. The batch experiments showed that GSH@Fe₃O₄ MNPs have a brilliant removal efficiency of 97% and 79% for CV and PR dyes, respectively, within a period of 60 min. The influence of different operational parameters like adsorbent dosage, pH, temperature, reaction time, and initial dye concentration on the removal behaviour of the adsorbent was studied in detail. The adsorbate-adsorbent reaction was tested over isotherm models, and the reaction fitted well for Langmuir isotherm with an excellent q_max value of 1619.5 mg/g and 1316.16 mg/g for CV and PR dye, respectively. The experimental results were also validated using different reaction kinetics, and it was found that the pseudo-first-order model fits well for PR dye adsorption (R² = 0.91), while adsorption of CV dye was in best agreement with the pseudo-second-order kinetic model (R² = 0.98). Thermodynamic studies revealed that the adsorption reaction was spontaneous and endothermic in nature. Furthermore, GSH@Fe₃O₄ MNPs can be reused effectively up to 5 cycles of dye removal. Major mechanisms involved in the adsorption reaction were expected to be electrostatic attraction, hydrogen bonding, and π-interactions. The efficiency of GSH@Fe₃O₄ MNPs in real water samples suggested that it has a high potential for dye removal from complex aqueous systems and could be used as an effective alternative for remediation of dyes contaminated water.

Development of magnetic solid phase extraction based on magnetic chitosan-graphene oxide nanoparticles and deep eutectic solvents for the determination of flavonoids by high performance liquid chromatography

An environmentally friendly magnetic solid phase extraction method was developed based on magnetic chitosan-graphene oxide nanoparticles and deep eutectic solvents (DESs) for the pre-concentration and isolation of flavonoids (apigenin, morin, naringenin, and quercetin) of natural orange juice, commercial apple juice, onion juice, green tea, and natural apple juice samples. DESs via hydrophilic and π-π interactions could increase the extraction performance. The immobilization of chitosan-graphene oxide on the surface of Fe₃O₄ nanoparticles improved their chemical properties and mechanical stability. In addition, the prepared magnetic nanoparticles with the hydrophilic polymeric network and the high surface area of the graphene oxide increased the access of binding sites and extraction performance. The use of DESs as desorption of solvent and the individual properties of MANPs provided the ability for high extraction recovery and accelerates the time to reach equilibrium. The principal variables that influence microextraction efficiency, including the extraction time, type of DES, stirring rate, desorption time, type of eluent solvent, and pH of the sample solution, were screened via the Plackett-Burman design and then the variables were optimized by the Box-Behnken design. Under the optimum conditions obtained, the developed method showed a good working range (R² ≥ 0.9962). The limit of detection (LOD) and the limit of quantification (LOQ) ranged from 0.03 μg L^-1 (morin) to 0.14 μg L^-1 (naringenin) and from 0.09 μg L^-1 (morin) to 0.46 μg L^-1 (naringenin) variables, respectively. The intraday precision was in the range of 4.1-4.8. In order to experiment with the precision and applicability of the MSPE-DES method, spiking recovery studies were performed in beverages and vegetable samples (natural orange juice, onion juice, commercial apple juice, natural apple juice, and green tea). The recovery results for real samples were calculated as 90-102%.

Development of magnetic dispersive micro-solid phase extraction based on magnetic agarose nanoparticles and deep eutectic solvents for the isolation and pre-concentration of three flavonoids in edible natural samples

In the present study, an environmentally friendly magnetic dispersive micro-solid phase extraction was developed based on magnetic agarose nanoparticles and deep eutectic solvents for the isolation and pre-concentration of three flavonoids (morin, quercetin, and kaempferol) from dark tea, chocolate, vegetable, and fruit juice samples. In this method, deep eutectic solvents were synthesized from less toxic and low-cost substances under feasible conditions and used as eluents in the desorption process. These solvents can be considered as a green alternative to traditional organic reagents to increase the adsorption capacity and reduce the matrix interferences, dangerous waste generation and environmental pollution. A Plackett-Burman design was employed for screening the experimental variables. The effective variables were then optimized by Box-Behnken design (BBD). Under the optimial conditions, the presented method demonstrated wide linear ranges of 1-500 μg. L^-1 for morin and quercetin, and 5-500 μg. L^-1 for kaempferol with satisfactory recoveries above 91%. Limit of detections (LODs) and quantifications (LOQs) of flavonoids varied in 0.2-1.1 μg. L^-1 and 0.66-3.63 μg. L^-1, respectively. The precision of the proposed method was the range of 2.6-5.7%.

Recent applications of magnetic solid phase extraction in sample preparation for phytochemical analysis

Sample preparation such as isolation and pre-concentration is a crucial step for the phytochemical analysis. Magnetic solid-phase extraction (MSPE) has received considerable attention, mainly due to its phase separation more conveniently by facile magnetic decantation as compared to traditional SPE. This review focused on the recent applications of MSPE in sample preparation for the analysis of phytochemical compounds in plants, biological samples and Chinese herbal preparations. In addition, the enzymes immobilized on the magnetic materials and used for the biospecific extraction of enzyme inhibitors were also discussed. The information summarized in this article may provide a reference to the further applications of MSPE in phytochemical analysis.

Effective degradation of Di-n-butyl phthalate by reusable, magnetic Fe3O4 nanoparticle-immobilized Pseudomonas sp. W1 and its application in simulation

Di-n-butyl phthalate (DBP), one of the most widely used plasticizers, has been listed as a priority pollutant because of its toxicity to both humans and animals. In this study, Pseudomonas sp. W1, isolated from activated sludge, was capable of degrading 99.88% of DBP (1000 mg L^-1) within 8 days. We immobilized the W1 strain using Fe₃O₄ iron nanoparticles (IONPs) coated with poly-dopamine (PDA), and further evaluated its DBP degradation efficiency. The DBP degradation performance of W1 was improved by immobilization, exhibiting 99.69% of DBP degradation efficiency on the 6th day, which was 25.68% higher than un-immobilized W1. After three cycles of magnetic recycling and utilization, W1-PDA-IONPs retained 99.6% of their original efficiency. W1-PDA-IONPs were then used to degrade DBP in landfill leachate. When the proportion of raw leachate was ≤50%, DBP could be all degraded by W1-PDA-IONPs within 6 days. In 100% landfill leachate, DBP degradation efficiency after 10 days of incubation reached 66.40%. Furthermore, W1-PDA-IONPs cells in a simulated aeration system could be effectively magnetically separated at aeration rates from 60 to 600 mL min^-1. These results highlight the potential of W1-PDA-IONPs in the bioremediation of DBP-contaminated waste water.

Preparation of novel molecularly imprinted magnetic graphene oxide and their application for quercetin determination

In this work, quercetin (Que) molecular imprinted polymer (MIP) material decorated on magnetic graphene oxide (MGO) with high performance was prepared for the first time using a surface-imprinting technique. Magnetic graphene oxide was synthesized using the solvothermal route. Methacrylic acid (MAA) was used as functional monomer, ethylene glycol dimethyl acrylate (EGDMA) as cross-linker; Que. was used as template, for the decoration with MIP. The prepared nanocomposite was examined by different characterization methods including fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM). The adsorption performance was investigated. MGO-MIP was found to have high loading (369 mg g^-1) and selective capacity making the nanomaterial more performant than previous similar reported nanomaterials. The determination of Que. was carried out by mean of magnetic solid phase extraction method coupled with high-performance liquid chromatography (HPLC) and the extraction conditions studies were also performed out. Under the optimized conditions, MGO-MIP showed great performance for the extraction, separation and determination of Que. in green tea and serum samples, compared to the flavonoid analogs luteolin (Lut) and rutin (Rut) in the same matrix samples.

Preferential adsorption of flavonoids from peanut shell by amino-modified Fe3 O4 nanoparticles (MNP-NH2 )

BACKGROUND

The highly selective capture of individual components of complex systems such as Chinese medicine extracts is a great challenge. With the rapid development of nanoscience, magnetic materials have attracted increased attention as suitable candidates for use in drug transport vehicles.

RESULTS

In this work, amino-modified Fe₃ O₄ nanoparticles (MNP-NH₂ ) have been synthesized and successfully used to selectively isolate luteolin, a type of flavonoid, from peanut shell, coupled with high-performance liquid chromatography. MNP-NH₂ were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and vibrating sample magnetometer analysis, which showed that the amino functional groups were successfully bound to the surface of the magnetic particles. Adsorption of six different flavonoids by MNP-NH₂ showed that the mechanism of adsorption was related to the number of ortho-phenolic hydroxyl groups. The optimized adsorption conditions were extraction for 40 min at 30 °C by single-factor experiments and the final elution conditions were determined to be 5 mL of 20% glacial acetic acid (methanol:water = 60:40) and ultrasonication for 40 min by L9 (3⁴ ) orthogonal test.

CONCLUSION

Based on these findings, we first created a method for separating luteolin from peanut shell extract by MNP-NH₂ . This newly developed magnetic method of extracting chemical compounds from herbal foodstuffs and medicines provides new ideas for the utilization of a cash crop. © 2018 Society of Chemical Industry.

Secondary Metabolites in the Green Synthesis of Metallic Nanoparticles

The ability of organisms and organic compounds to reduce metal ions and stabilize them into nanoparticles (NPs) forms the basis of green synthesis. To date, synthesis of NPs from various metal ions using a diverse array of plant extracts has been reported. However, a clear understanding of the mechanism of green synthesis of NPs is lacking. Although most studies have neglected to analyze the green-synthesized NPs (GNPs) for the presence of compounds derived from the extract, several studies have demonstrated the conjugation of sugars, secondary metabolites, and proteins in these biogenic NPs. Despite several reports on the bioactivities (antimicrobial, antioxidant, cytotoxic, catalytic, etc.) of GNPs, only a handful of studies have compared these activities with their chemically synthesized counterparts. These comparisons have demonstrated that GNPs possess better bioactivities than NPs synthesized by other methods, which might be attributed to the presence of plant-derived compounds in these NPs. The ability of NPs to bind with organic compounds to form a stable complex has huge potential in the harvesting of precious molecules and for drug discovery, if harnessed meticulously. A thorough understanding of the mechanisms of green synthesis and high-throughput screening of stabilizing/capping agents on the physico-chemical properties of GNPs is warranted to realize the full potential of green nanotechnology.

Platform construction and extraction mechanism study of magnetic mixed hemimicelles solid-phase extraction

Simple, accurate and high-throughput pretreatment method would facilitate large-scale studies of trace analysis in complex samples. Magnetic mixed hemimicelles solid-phase extraction has the power to become a key pretreatment method in biological, environmental and clinical research. However, lacking of experimental predictability and unsharpness of extraction mechanism limit the development of this promising method. Herein, this work tries to establish theoretical-based experimental designs for extraction of trace analytes from complex samples using magnetic mixed hemimicelles solid-phase extraction. We selected three categories and six sub-types of compounds for systematic comparative study of extraction mechanism, and comprehensively illustrated the roles of different force (hydrophobic interaction, π-π stacking interactions, hydrogen-bonding interaction, electrostatic interaction) for the first time. What’s more, the application guidelines for supporting materials, surfactants and sample matrix were also summarized. The extraction mechanism and platform established in the study render its future promising for foreseeable and efficient pretreatment under theoretical based experimental design for trace analytes from environmental, biological and clinical samples.

Removal of endocrine disruptor di-(2-ethylhexyl)phthalate by modified polythiophene-coated magnetic nanoparticles: characterization, adsorption isotherm, kinetic study, thermodynamics

Superparamagnetic nanosorbent poly(phenyl(4-(6-thiophen-3-yl-hexyloxy)-benzylidene)-amine)/Fe₃O₄ nanoparticles (Fe₃O₄@P3TArH) were successfully synthesized via a simplistic method for the enhanced extraction of potent endocrine disruptor, di-(2-ethylhexyl)phthalate (DEHP).

Determination of losartan potassium in the presence of hydrochlorothiazide via a combination of magnetic solid phase extraction and fluorometry techniques in urine samples

A sensitive and highly efficient method for the determination of losartan potassium (LOS) in the presence of hydrochlorothiazide (HCTZ) via a combination of magnetic solid phase extraction (MSPE) and fluorometry techniques is suggested.

Improvement of heat dissipation in agarose gel electrophoresis by metal oxide nanoparticles

Joule heating is a primary limitation in slab gel electrophoresis which is a gold standard method in biochemistry and biotechnology.