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Microcystins are cyclic heptapeptide toxins produced by a number of genera of cyanobacteria. They are ubiquitous in bodies of water worldwide and pose significant hazard to human, plant, and animal health. Microcystins are primarily hepatotoxins known to inhibit serine-threonine phosphatases leading to the disruption of cascade of events important in the regulation and control of cellular processes. Covalent binding of microcystins with phosphatases is thought to be responsible for the cytotoxic and genotoxic effects of microcystins. In addition, microcystins can trigger oxidative stress in cells resulting in necrosis or apoptosis. Their cyclic structure and novel amino acids enhance their stability and persistence in the environment. Humans are primarily exposed to microcystins via drinking water consumption and accidental ingestion of recreational water. Recreational exposure by skin contact or inhalation to microcystins is now recognized to cause a wide range of acute illnesses which can be life-threatening. Microcystins are primarily degraded by microorganisms in the environment, while sunlight can cause the isomerization of the double bonds and hydroxylation in the presence of pigments. Attempts to utilize these organisms in sand and membrane filters to treat water contaminated with microcystins showed complete removal and detoxification. Conventional water treatment processes may not fully eliminate microcystins when there are high levels of organic compounds especially during harmful bloom events. Combination of conventional and advanced oxidation technologies can potentially remove 100% of microcystins in water even in turbid conditions. This review covers selected treatment technologies to degrade microcystins in water.

Aim To quantitatively assess the degree of conversion and the water-leaching targeted compound from 3D-printed aligners. Materials and methods 3D-printed aligners were made of photopolymerized resin (Tera Harz TC85A). The molecular structure and degree of conversion of the set resin were investigated by ATR-FTIR spectroscopy (n = 5). The aligners (n = 10) were immersed in double distilled water for 1 week at 37°C and the eluents were analysed using liquid chromatography/mass spectrometry methods (LC–ESI-MS/MS for urethane dimethacrylate [UDMA] and LC–APCI-MS/MS for bispenol-A [BPA]). Results The resin was composed of aliphatic vinyl ester-urethane monomers, with acrylate and/or methacrylate functionalization. The degree of conversion was estimated as to 83%. There was no detection of BPA in any of the assessed samples (0.25 µg/l). Quantifiable amounts of UDMA were detected in all the exposed samples, ranging from 29 to 96 µg/l. Conclusions Although efficiently polymerized and BPA free, the great variability in the amount of UDMA monomer leached from the examined samples may raise concerns on potential health hazards after repeated intraoral exposure, which is indicated for this class of materials.

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