PDF(Pubmed)
Abstract：
Recent studies show that biofilm substances in contact with nanoplastics play an important role in the aggregation and sedimentation of nanoplastics. Consequences of these processes are changes in biofilm formation and stability and changes in the transport and fate of pollutants in the environment. Having a deeper understanding of the nanoplastics-biofilm interaction would help to evaluate the risks posed by uncontrolled nanoplastic pollution. These interactions are impacted by environmental changes due to climate change, such as, e.g., the acidification of surface waters. We apply fluorescence correlation spectroscopy (FCS) to investigate the pH-dependent aggregation tendency of non-functionalized polystyrene (PS) nanoparticles (NPs) due to intermolecular forces with model extracellular biofilm substances. Our biofilm model consists of bovine serum albumin (BSA), which serves as a representative for globular proteins, and the polysaccharide alginate, which is a main component in many biofilms, in solutions containing Na+ with an ionic strength being realistic for fresh-water conditions. Biomolecule concentrations ranging from 0.5 g/L up to at maximum 21 g/L are considered. We use non-functionalized PS NPs as representative for mostly negatively charged nanoplastics. BSA promotes NP aggregation through adsorption onto the NPs and BSA-mediated bridging. In BSA-alginate mixtures, the alginate hampers this interaction, most likely due to alginate-BSA complex formation. In most BSA-alginate mixtures as in alginate alone, NP aggregation is predominantly driven by weaker, pH-independent depletion forces. The stabilizing effect of alginate is only weakened at high BSA contents, when the electrostatic BSA-BSA attraction is not sufficiently screened by the alginate. This study clearly shows that it is crucial to consider correlative effects between multiple biofilm components to better understand the NP aggregation in the presence of complex biofilm substances. Single-component biofilm model systems based on comparing the total organic carbon (TOC) content of the extracellular biofilm substances, as usually considered, would have led to a misjudgment of the stability towards aggregation.
摘要：
最近的研究表明，与纳米塑料接触的生物膜物质在纳米塑料的聚集和沉降中起着重要作用。这些过程的后果是生物膜形成和稳定性的变化以及污染物在环境中的迁移和归宿的变化。对纳米塑料-生物膜相互作用有更深入的了解将有助于评估不受控制的纳米塑料污染带来的风险。这些相互作用受到气候变化引起的环境变化的影响，例如,例如，地表水的酸化。我们应用荧光相关光谱（FCS）研究了非官能化聚苯乙烯（PS）纳米颗粒（NPs）的pH依赖性聚集趋势，这是由于分子间作用力与模型细胞外生物膜物质。我们的生物膜模型包括牛血清白蛋白（BSA），作为球状蛋白质的代表，和多糖藻酸盐，这是许多生物膜的主要成分，在含有Na的溶液中，离子强度对于淡水条件是现实的。考虑的生物分子浓度范围为0.5g/L至最高21g/L。我们使用非官能化的PSNP作为主要带负电荷的纳米塑料的代表。BSA通过吸附到NP上和BSA介导的桥接促进NP聚集。在BSA-藻酸盐混合物中，海藻酸盐阻碍了这种相互作用，很可能是由于藻酸盐-BSA复合物的形成。在大多数BSA-藻酸盐混合物中，如单独的藻酸盐中，NP聚集主要是由较弱的，与pH无关的消耗力。藻酸盐的稳定作用仅在高BSA含量下减弱，当静电BSA-BSA吸引力未被藻酸盐充分筛选时。这项研究清楚地表明，考虑多种生物膜成分之间的相关作用对于更好地了解复杂生物膜物质存在下的NP聚集至关重要。基于比较细胞外生物膜物质的总有机碳（TOC）含量的单组分生物膜模型系统，正如通常认为的那样，会导致对聚集稳定性的误判。
