Rapid and Accurate Quantification of Paramylon Produced from Euglena gracilis Using an ssDNA Aptamer

On-site microfluidic aptasensor for rapid and highly selective detection of microcystin-LR

To detect microcystin-LR (MC-LR), a potent cyanotoxin harmful to human health, fast and precise monitoring tools are essential, particularly for on-site applications. In this study, we developed a novel on-site microfluidic aptasensor system that utilizes a fluorescence-tagged aptamer for the rapid and selective detection of MC-LR. By employing a target non-immobilized aptamer selection technique, high-affinity DNA aptamers for MC-LR were identified, and then further optimized through sequence truncation to enhance detection efficiency. The developed aptamer was designed such that its fluorescence is quenched in the absence of MC-LR, but recovered in its presence, enabling a clear signal detection that correlates with a toxin concentration. The developed system achieved a detection limit of 1.9 ppb, significantly lower than the safety threshold suggested by world health organization (WHO) for recreational waters, demonstrating sufficient sensitivity for reliable on-site monitoring. In addition, the microfluidic aptasensor system demonstrated high specificity, exhibiting the strongest response to MC-LR compared to other cyanotoxins. This system is the first portable MC-LR detection tool that allows for on-site environmental monitoring with the advantages of its fast response time and ease of operation. Combining a low detection limit with high accuracy, the microfluidic aptasensor system presents a promising alternative to conventional laboratory-based methods, providing a practical and reliable solution for water quality assessment.

The need for smart microalgal bioprospecting

Microalgae's adaptability and resilience to Earth's diverse environments have evolved these photosynthetic microorganisms into a biotechnological source of industrially relevant physiological functions and biometabolites. Despite this, microalgae-based industries only exploit a handful of species. This lack of biodiversity hinders the expansion of the microalgal industry. Microalgal bioprospecting, searching for novel biological algal resources with new properties, remains a low throughput and time-consuming endeavour due to inefficient workflows that rely on non-selective sampling, monoalgal culture status and outdated, non-standardized characterization techniques. This review will highlight the importance of microalgal bioprospecting and critically explore commonly employed methodologies. We will also explore current advances driving the next generation of smart algal bioprospecting focusing on novel workflows and transdisciplinary methodologies with the potential to enable high-throughput microalgal biodiscoveries. Images adapted from (Addicted04 in Wikipedia File: Australia on the globe (Australia centered).svg. 2014.; Jin et al. in ACS Appl Bio Mater 4:5080-5089, 2021; Kim et al. in Microchim Acta 189:88, 2022; Tony et al. in Lab on a Chip 15, 19:3810-3810; Thermo Fisher Scientific INC. in CTS Rotea Brochure).

A review of paramylon processing routes from microalga biomass to non-derivatized and chemically modified products

Paramylon is a linear β-1,3-glucan, similar to curdlan, produced as intracellular granules by the microalga Euglena gracilis, a highly versatile and robust strain, able to grow under various trophic conditions, with valorization of CO_2, wastewaters, or food byproducts as nutrients. This review focuses in particular on the various processing routes leading to new potential paramylon based products. Due to its crystalline structure, involving triple helices stabilized by internal intermolecular hydrogen bonds, paramylon is neither water-soluble nor thermoplastic. The few solvents able to disrupt the triple helices, and to fully solubilize the polymer as random coils, allow non derivatizing shaping into films, fibers, and even nanofibers by a specific self-assembly mechanism. Chemical modification in homogeneous or heterogeneous conditions is also possible. The non-selective or regioselective substitution of the hydroxyl groups of glucosidic units leads to water-soluble ionic derivatives and thermoplastic paramylon esters with foreseen applications ranging from health to bioplastics.

Selection and characterization of toxic Aspergillus spore-specific DNA aptamer using spore-SELEX

As airborne spores of toxic Aspergillus species cause mild symptoms to invasive fungal infections, their indoor concentration should be controlled through real-time management. Aptamer-based biosensors could provide economical and simple solutions for point-of-care. In this study, we isolated aptamers binding to the spores of three representative toxic Aspergillus species (A. fumigatus, A. flavus, and A. niger) for the first time, using cell-SELEX (systematic evolution of ligands through exponential enrichment). Among the aptamer candidates, Asp-3 showed a broad and high binding affinity for the Aspergillus spores. Considering the low binding affinity with proteinase-treated spores, we speculated that the Asp-3 binding sites could be possibly associated with cell surface proteins. The high Asp-3 specificity was confirmed by comparing the binding affinity between the Aspergillus target species and other common indoor fungal species. Moreover, we also established quantitative linear relationships between Asp-3 and the spore concentration of each Aspergillus species. Therefore, the selected Asp-3 aptamer, conjugated with detection sensors, could be an effective biorecognition element for the spores of three toxic Aspergillus species.

Selection of Specific DNA Aptamers for Hetero-Sandwich-Based Colorimetric Determination of Campylobacter jejuni in Food

Herein, a high-affinity single-stranded DNA aptamer (59 nt) against Campylobacter jejuni, defined as CJA1, was obtained using the whole-bacterium-based systemic evolution of ligands by exponential enrichment procedure. CJA1 was analyzed with a stable secondary structure and low dissociation constant (K_d) value of 1.37 ± 0.28 nM. The potential use of CJA1 was exemplified by the construction of a hetero-sandwich platform, in which C. jejuni was bound with a biotin-tagged CJA1 to perform a colorimetric reaction that is associated with visible color changes and detectable optical responses. Dependent upon this sensing platform, C. jejuni can be detected from 1.7 × 10¹ to 1.7 × 10⁶ colony-forming units (CFU)/mL. The limit of detection (LOD) is obtained as 10 CFU/mL in PBS. The specificity study showed that the sensing platform is easy to distinguish C. jejuni from other common pathogens. Moreover, the C. jejuni-contaminated milk samples can also be accurately probed (LOD = 13 CFU/mL) without sacrificing its assay abilities, indicating the promising prospect of CJA1 in the fields of biosensing and diagnostics.