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Natural organic matter (NOM) adsorption on nanoparticle (NP) surfaces in natural waters forms a corona that can alter NP properties and its environmental fate. Anthropogenic NPs are usually coated with an organic capping agent that may, in turn, influence the extent and molecular composition of the corona. Up-to-now, the molecular composition of the NOM corona can only be analyzed in controlled experiments due to a lack of appropriate direct surface analysis methods. Here, we introduce laser desorption ionization Fourier-transform ion cyclotron resonance mass spectrometry (LDI-FT-ICR-MS) to directly analyze Suwannee River Fulvic Acid (SRFA) after adsorption and sequential desorption on gold (Au) NPs capped with small molecules (citric acid (CA), tannic acid (TA), lipoic acid (LA)) and large polymers (polyvinylpyrrolidone (PVP), branched polyethylenimine (BPEI), methoxy polyethylene glycol sulfhydryl (m-PEG-SH)). LDI-FT-ICR-MS revealed differences in the molecular composition of the NP corona depending on the capping agents' chemistry. Positively charged BPEI efficiently adsorbed larger oxygen-rich aromatics whereas negatively charged CA and LA adsorbed oxygen-containing aromatics. The weak negative PVP adsorbed oxygen-containing aliphatics and non-charged m-PEG-SH small oxygen-depleted aliphatics, both with lower efficiency. However, TA preferentially adsorbed polyphenolic compounds from SRFA due to its similar chemistry. Further comparison of the Au-CA corona with the conventional indirect electrospray ionization (ESI)-FT-ICR-MS analysis largely confirmed the results of the new direct LDI analysis. Due to the higher sensitivity of the direct method, LDI-FT-ICR-MS can be applied to environmentally relevant NOM : NP ratios which was not possible before. LDI-FT-ICR-MS is a promising method to study the extent and molecular composition of NP coronas and suitable to better elucidate NP fate in the environment.

To better understand the physiology and acclimation capability of the cell, one of the great challenges of the future is to access the interior of a cell and unveil its chemical landscape (composition and distribution of elements and molecules). Chemical imaging has greatly improved in sensitivity and spatial resolution to visualize and quantify nutrients, metabolites, toxic elements, and drugs in single cells at the subcellular level. This review aims to present the current potential of these emerging imaging technologies and to guide biologists towards a strategy for interrogating biological processes at the nanoscale. We also describe various solutions to combine multiple imaging techniques in a correlative way and provide perspectives and future directions for integrative subcellular imaging across different disciplines.

Nowadays, high-resolution imaging techniques are extensively applied in a complementary way to gain insights into complex phenomena. For a truly complementary analytical approach, a common sample carrier is required that is suitable for the different preparation methods necessary for each analytical technique. This sample carrier should be capable of accommodating diverse analytes and maintaining their pristine composition and arrangement during deposition and preparation. In this work, a new type of sample carrier consisting of a silicon wafer with a hydrophilic polymer coating was developed. The robustness of the polymer coating toward solvents was strengthened by cross-linking and stoving. Furthermore, a new method of UV-ozone cleaning was developed that enhances the adhesion of the polymer coating to the wafer and ensures reproducible surface-properties of the resulting sample carrier. The hydrophilicity of the sample carrier was recovered applying the new method of UV-ozone cleaning, while avoiding UV-induced damages to the polymer. Noncontact 3D optical profilometry and contact angle measurements were used to monitor the hydrophilicity of the coating. The hydrophilicity of the polymer coating ensures its spongelike behavior so that upon the deposition of an analyte suspension, the solvent and solutes are separated from the analyte by absorption into the polymer. This feature is essential to limit the coffee-ring effect and preserve the native identity of an analyte upon deposition. The suitability of the sample carrier for various sample types was tested using nanoparticles from suspension, bacterial cells, and tissue sections. To assess the homogeneity of the analyte distribution and preservation of sample integrity, optical and scanning electron microscopy, helium ion microscopy, laser ablation inductively coupled plasma mass spectrometry, and time-of-flight secondary ion mass spectrometry were used. This demonstrates the broad applicability of the newly dev

To better understand the physiology and acclimation capability of the cell, one of the great challenges of the future is to access the interior of a cell and unveil its chemical landscape (composition and distribution of elements and molecules). Chemical imaging has greatly improved in sensitivity and spatial resolution to visualize and quantify nutrients, metabolites, toxic elements, and drugs in single cells at the subcellular level. This review aims to present the current potential of these emerging imaging technologies and to guide biologists towards a strategy for interrogating biological processes at the nanoscale. We also describe various solutions to combine multiple imaging techniques in a correlative way and provide perspectives and future directions for integrative subcellular imaging across different disciplines.

Microalgae biofilms may play an important role in the mitigation and prevention of eutrophication caused by domestic, agricultural and industrial wastewater effluents. Despite their potential, the biofilm development and role in nutrient removal are not well understood. Its clarification requires comprehensive studies of the complex three-dimensional architecture of the biofilm. In this study, we established a multimodal imaging approach to provide key information regarding architecture development and nutrient distribution in the biofilm of two green algae organisms: Chlorella pyrenoidosa and Chlorella vulgaris. Helium ion microscopy (HIM), scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM-EDX) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were employed for i) elucidation of spatial arrangement, ii) elemental mapping and iii) 3D chemical imaging of the biofilm. The fine structure of the algal biofilm was resolved by HIM, the evidence of the accumulation of phosphate in hot spots was provided by SEM-EDX and the localization of phosphate oxides granules throughout the whole sample was clarified by ToF-SIMS. The reported results shed light on the phosphorus distribution during Chlorella's biofilm formation and highlight the potential of such correlative approach to solve fundamental question in algal biotechnology research.