Advances in aptamer-based biosensors for monitoring foodborne pathogens.

Biosensors are analytical devices for detecting a wide range of targets, including cells, proteins, DNA, enzymes, and chemical and biological compounds. They mostly rely on using bioprobes with a high binding affinity to the target for specific detection. However, low specificity and effectiveness of the conventional biosensors has led to the search for novel materials, that can specifically detect biomolecules. Aptamers are a group of single-stranded DNA or RNA oligonucleotides, that can bind to their targets with high specificity and serve as effective bioprobes for developing aptamer-based biosensors. Aptamers have a shorter production time, high stability, compared to traditional bioprobes, and possess ability to develop them for specific target molecules for tailored applications. Thus, various aptasensing approaches, including electrochemical, optical, surface plasmon resonance and chip-dependent approaches, have been investigated in recent times for various biological targets, including foodborne pathogens. Hence, this article is an overview of various conventional foodborne pathogen detection methods, their limitations and the ability of aptamer-based biosensors to overcome those limitations and replace them. In addition, the current status and advances in aptamer-based biosensors for the detection of foodborne pathogens to ensure food safety were also discussed. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05889-8.

Multi-membrane formation in chitosan hydrogel shell by the addition of goethite nanoparticles.

In this study, chitosan (an abundant natural biopolymer) was used as a polysaccharide source to synthesize multi-membrane hydrogel capsules (MHC) using a novel approach. The MHC material was formed in a single step self-assembly approach by an in-situ immobilization of goethite nanoparticles (GNP) during the chitosan-anionic surfactant complex formation reaction. The pivotal role of GNP in the formation of multi-membrane was thoroughly discussed herein. Some important factors effecting the formation and property of MHC were explored. The results of adsorption study (Co ≈ 1000 mg/L, 30 °C, and pH ≈ 7.0) demonstrated that MHC (1321 ±â€¯35.6 mg/g) exhibited excellent adsorptive capacity for Congo red dye compared to HC (244 ±â€¯35.6 mg/g) and GNP (91.1 ±â€¯19.6 mg/g). Therefore, the unique characteristics of multi-membranes structures breeds an exciting prospect of application in diverse fields, especially wastewater treatment because of its excellent adsorption capacity for dye contaminants.

Facile magnetic biochar production route with new goethite nanoparticle precursor.

This study developed a green and novel magnetic biochar via the co-pyrolysis of firwood biomass pre-treated with 10% (w/w) of either solid-phase (admixing; G10BCA) or liquid-phase (impregnation; G10BCI) goethite mineral (α-FeOOH). Newly fabricated magnetic biochars were characterized by inductively coupled plasma-optical emission spectroscopy (ICP-OES), Brunauer-Emmett-Teller (BET) equipment, X-ray powder diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), proximate and elemental analyzer, and vibrating sample magnetometry. The effects of magnetic precursor, iron loading, and aqua-treatments on recoverability, magnetic property, and stability (resistance to α-FeOOH reconstructive crystallization/dissolution reactions) were explored and compared to those of magnetic biochar derived from conventional ferric chloride precursor (F10BCI). Results confirmed a direct correlation between biochar yields and ash contents with iron loading, irrespective of the used types of magnetic precursors (α-FeOOH or FeCl3). Although FeCl3 can generate magnetic biochar (F10BCI) with higher total carbon content (83.6%) and surface area (299 m2/g), α-FeOOH proved to be more effective at yielding magnetic biochars with nanostructured surfaces, lower water extractable components (thus green; G10BCA = 0.21 mg/mL and G10BCI = 0.16 mg/mL), higher magnetic saturation (G10BCA = 10.0 emu/g and G10BCI = 20.8 emu/g), higher ferromagnetic susceptibility, and excellent recoverability. α-FeOOH was undetected on the surface of G10BCA, post-aqua-treatments (over 30 days), and this demonstrated its stability in the face of demagnetization via α-FeOOH reformation reactions. Consequently, this study demonstrated that the admixing solid-phase α-FeOOH (10%) with firwood biomass offered a green, facile, and efficient way to thermochemically produce magnetic biochar. The produced biochar exhibited a superb stability to α-FeOOH reconstructive crystallization/dissolution reactions in aquatic (aqua) media, green attributes, good magnetic properties, and great potential applications in many areas of the economy.

Preparation and characterization of alginate-kelp biochar composite hydrogel bead for dye removal.

The alginate-kelp biochar composite hydrogel bead (Alg-KBC) was successfully developed via physical crosslinking with Ca2+. The composite material was characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectrometry (ICP-OES), and elemental analyzer. The Alg-KBC showed high removal capacity for crystal violet (CV), from aqueous solution (33.8% more than that of the pristine alginate bead). The adsorption isotherm data were fitted to the nonlinear forms of the Langmuir, Freundlich, and Redlich-Peterson isotherm models. Also, the adsorption kinetics data were analyzed with the nonlinear forms of the pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. Both chemisorption and physisorption with an indispensable role of external mass transfer and stagewise pore diffusion were essential in the adsorption process. Thus, by impregnating biochar powder in alginate, a bio-platform, a composite hydrogel bead which has higher affinity for cationic dye in aqueous medium and also eliminates the onerous task of separating biochar powder from the adsorbate solution, was obtained. Hence, the Alg-KBC can be considered for efficient dye removal in the wastewater treatment process.

Characterization and adsorption performance evaluation of waste char by-product from industrial gasification of solid refuse fuel from municipal solid waste.

This study investigated the effect of steam and air flowrate combinations on the syngas efflux, physicochemical properties and adsorption performances (on congo red, CR and crystal violet, CV removal) of waste char by-product from the industrial gasification of solid refuse fuel from municipal solid waste. The BET surface area (11.4 m2/g), porosity (74.7%), fixed carbon content (25.8 wt%) and hydrophilicity (0.09) were enhanced with lower steam rate and higher air supply rate combination (MSWC-L) than for the higher steam rate and lower air supply rate combination (MSWC-H). Adsorption performances were higher for MSWC-L than MSWC-H on both CR (35.7-49.7 mg/g) and CV (235 to 356 mg/g) removal, suggesting that, higher air supply rate (214 Nm3/h; at 0.36 equivalence ratio) with lower steam rate (37 kg/h) were more effective gasification process conditions. Results showed that, syngas efflux was more sensitive to air supply rate than steam supply rate. Reactions in the combustion zone were not only limited to the pyrolysis gas vapours but to the char also. In conclusion, the waste chars from municipal solid waste gasification showed good potential as adsorbents in wastewater treatment.