Page - 41 - in Freshwater Microplastics - Emerging Environmental Contaminants?

5.2 DetectingandQuantifyingParticleUptake asaPrerequisite forAssessing theEffects ofNano- andMicroplastics Research on the biological effects of nano- andmicroplastics is currently at the stage of determining possible responses and thereby investigating the interactions oforganismsandplasticparticles.Formostorganisms, there isadirectandobvious linkbetween theuptakeofnano- andmicroplastics by ingestionorventilation and subsequent effects.Even so, knowledgeonuptake itself is very limited, especially when it comes toquantificationof this process, since thedetectionof small plastic particles is extremely challenging, as described earlier. Methods that have been used toquantifyparticleuptake includecountingusingamicroscopeandspectros- copy (Raman or FT-IR) of tissue samples. Furthermore, fluorescent particles are used for imageanalysis of gut sections, fluorescencemicroscopyand themeasure- mentoffluorescence intensityof tissuesasaproxyfor thequantityofparticles.All thesemethods have limitations and are either very difficult to use on a large scale (e.g. spectroscopy) or become increasingly challenged and even unusable with smaller particles and lower particle numbers. This ismajor drawback sincemost biological effects depend on the amount of plastic particles taken up into the organism. A possible way forward could be the use of plastic particles with a metal corewhich are easy tomeasure, even in small concentrations and sizes, by, for example,mass spectroscopy – using the same techniques as for nanoparticles. Such traceable nano- andmicroplastics do not reflect naturally occurring particles as found in the environment, but they could serve asmodel particles for investi- gating interactions of nano- andmicroplastics with biological systems. The tech- niquecouldbeusedforprecisequantificationofparticlesaswell as for localisation in tissues. Nanoparticleswith a gold core and a polymer coating have previously been used in a number of studies, aimed at gaining an insight into the uptake of engineerednanomaterials infish anddaphnids [107]. 6 LessonsLearned. . .and theWayAhead When the ecotoxicology of nanomaterials emerged as a scientific field around a decade ago, the already existing field of ‘colloidal science’was somewhat over- looked.Over theyears, it hasbecome increasinglyclear thatmanyparallels canbe drawnbetween the twofields.The links betweenparticle behaviour, exposure and ecotoxicological effects, ashighlightedhere,demonstrate thehighly interdisciplin- ary nature and complexity of this research field. Consequently, cooperation is required between scientists with backgrounds in biology, chemistry and colloidal science.Similarly, for studies of environmental behaviour and the effects of nano- andmicroplastics, it isclearly important todrawonexperiencefromecotoxicology of nanomaterials aswell as colloidal science. This is the key tomoving forwards AquaticEcotoxicity ofMicroplastics andNanoplastics: LessonsLearned from. . . 41