Optical microalgal biosensors for aqueous contaminants using organically doped silica as cellular hosts

Highly selective molecularly imprinted-electrochemiluminescence sensor based on perovskite/Ru(bpy)32+ for simazine detection in aquatic products

A novel molecularly imprinted electrochemiluminescence (MIECL) sensor based on the luminescence of molecularly imprinted polymer-perovskite (MIP-CsPbBr₃) layer and Ru(bpy)₃²⁺ was fabricated for simazine detection. MIP-CsPbBr₃ layers were immobilized onto the surface of glassy carbon electrode as the capture and signal amplification probe, and Ru(bpy)₃²⁺ and co-reactant tripropylamine exhibited stronger electrochemiluminescence (ECL) emission. Under optimal conditions, the ECL signal of the MIECL sensor was linearly quenched, with the logarithm of simazine concentration ranging from 0.1 μg/L to 500.0 μg/L, correlation coefficient of 0.9947, and limit of detection of 0.06 μg/L. The practicality of the developed MIECL sensor method for simazine determination in aquatic samples was validated. Excellent recoveries of 86.5 %-103.9 % with relative standard deviation below 1.6 % were obtained for fish and shrimp samples at three different spiked concentrations. The MIECL sensor exhibited excellent selectivity, sensitivity, reproducibility, accuracy, and precision for simazine determination in actual aquatic samples.

Silica Hydrogels as Entrapment Material for Microalgae

Despite being a promising feedstock for food, feed, chemicals, and biofuels, microalgal production processes are still uneconomical due to slow growth rates, costly media, problematic downstreaming processes, and rather low cell densities. Immobilization via entrapment constitutes a promising tool to overcome these drawbacks of microalgal production and enables continuous processes with protection against shear forces and contaminations. In contrast to biopolymer gels, inorganic silica hydrogels are highly transparent and chemically, mechanically, thermally, and biologically stable. Since the first report on entrapment of living cells in silica hydrogels in 1989, efforts were made to increase the biocompatibility by omitting organic solvents during hydrolysis, removing toxic by-products, and replacing detrimental mineral acids or bases for pH adjustment. Furthermore, methods were developed to decrease the stiffness in order to enable proliferation of entrapped cells. This review aims to provide an overview of studied entrapment methods in silica hydrogels, specifically for rather sensitive microalgae.

Carbon black nanoparticles to sense algae oxygen evolution for herbicides detection: Atrazine as a case study

A novel amperometric algae-based biosensor was developed for the detection of photosynthetic herbicides in river water. The green photosynthetic algae Chlamydomonas reinhardtii was immobilized on carbon black modified screen-printed electrodes, exploiting carbon black as smart nanomaterial to monitor changes in algae oxygen evolution during the photosynthetic process. The decrease of oxygen evolution, occurring in the presence of herbicides, results in a decrease of current signals by means of amperometric measurements, in an analyte concentration dependent manner. Atrazine as case study herbicide was detected in a concentration range of 0.1 and 50 μM, with a linear range from 0.1 to 5 μM and a detection limit of 1 nM. No interference was observed in presence of 100 ppb arsenic, 20 ppb copper, 5 ppb cadmium, 10 ppb lead, 10 ppb bisphenol A, and 1 ppb paraoxon, tested as safety limits. A ~25% matrix effect and satisfactory recovery values of 107 ± 10% and 96 ± 8% were obtained in river water for 3 and 5 μM of atrazine, respectively. Stability studies were also performed obtaining a high working stability up to 10 h and repeatability with an RSD of 1.1% (n = 12), as well as a good storage stability up to 3 weeks.

Probing Contaminant-Induced Alterations in Chlorophyll Fluorescence by AC-Dielectrophoresis-Based 2D-Algal Array

The investigation of contaminant impact on algae requires rapid and reliable cell collection and optical detection. The capability of alternative current (AC) dielectrophoresis (DEP) collection of whole cell arrays with combined fluorescence microscopy detection to follow the alterations of chlorophyll fluorescence during environmental contaminant exposure was explored. The application of an AC-field of 100 V cm^-1, 100 Hz for 30 min to capture and immobilize the cells of green alga Chlamydomonas reinhardtii in two-dimensional (2D) arrays does not induce changes in chlorophyll fluorescence. The results demonstrate that DEP-based 2D-arrays allow non-invasive detection of chlorophyll fluorescence change upon exposure to high concentrations of copper oxide nanoparticles and ionic copper. These results were in agreement with data obtained by flow cytometry used as a comparative method. The tool was also applied to follow the effect of a number of ubiquitous contaminants such as inorganic mercury, methylmercury, and diuron. However, a statistically significant short-term effect was observed only for mercury. Overall, DEP-based 2D-arrays of algal cells with fluorescence detection appear to be suitable for stain-free probing the effects on the photosynthetic microorganisms in highly polluted environment.