Particle profiling of EV-lipoprotein mixtures by AFM nanomechanical imaging.

The widely overlapping physicochemical properties of lipoproteins (LPs) and extracellular vesicles (EVs) represents one of the main obstacles for the isolation and characterization of these pervasive biogenic lipid nanoparticles. We herein present the application of an atomic force microscopy (AFM)-based quantitative morphometry assay to the rapid nanomechanical screening of mixed LPs and EVs samples. The method can determine the diameter and the mechanical stiffness of hundreds of individual nanometric objects within few hours. The obtained diameters are in quantitative accord with those measured via cryo-electron microscopy (cryo-EM); the assignment of specific nanomechanical readout to each object enables the simultaneous discrimination of co-isolated EVs and LPs even if they have overlapping size distributions. EVs and all classes of LPs are shown to be characterised by specific combinations of diameter and stiffness, thus making it possible to estimate their relative abundance in EV/LP mixed samples in terms of stoichiometric ratio, surface area and volume. As a side finding, we show how the mechanical behaviour of specific LP classes is correlated to distinctive structural features revealed by cryo-EM. The described approach is label-free, single-step and relatively quick to perform. Importantly, it can be used to analyse samples which prove very challenging to assess with several established techniques due to ensemble-averaging, low sensibility to small particles, or both, thus providing a very useful tool for quickly assessing the purity of EV/LP isolates including plasma- and serum-derived preparations.

Surface functionalization of extracellular vesicle nanoparticles with antibodies: a first study on the protein corona "variable".

To be profitably exploited in medicine, nanosized systems must be endowed with biocompatibility, targeting capability, the ability to evade the immune system, and resistance to clearance. Currently, biogenic nanoparticles, such as extracellular vesicles (EVs), are intensively investigated as the platform that naturally recapitulates these highly needed characteristics. EV native targeting properties and pharmacokinetics can be further augmented by decorating the EV surface with specific target ligands as antibodies. However, to date, studies dealing with the functionalization of the EV surface with proteins have never considered the protein corona "variable", namely the fact that extrinsic proteins may spontaneously adsorb on the EV surface, contributing to determine the surface, and in turn the biological identity of the EV. In this work, we explore and compare the two edge cases of EVs modified with the antibody Cetuximab (CTX) by chemisorption of CTX (through covalent binding via biorthogonal click-chemistry) and by formation of a physisorbed CTX corona. The results indicate that (i) no differences exist between the two formulations in terms of binding affinity imparted by molecular recognition of CTX versus its natural binding partner (epidermal growth factor receptor, EGFR), but (ii) significant differences emerge at the cellular level, where CTX-EVs prepared by click chemistry display superior binding and uptake toward target cells, very likely due to the higher robustness of the CTX anchorage.

Microglial large extracellular vesicles propagate early synaptic dysfunction in Alzheimer's disease.

Synaptic dysfunction is an early mechanism in Alzheimer's disease that involves progressively larger areas of the brain over time. However, how it starts and propagates is unknown. Here we show that amyloid-ß released by microglia in association with large extracellular vesicles (Aß-EVs) alters dendritic spine morphology in vitro, at the site of neuron interaction, and impairs synaptic plasticity both in vitro and in vivo in the entorhinal cortex-dentate gyrus circuitry. One hour after Aß-EV injection into the mouse entorhinal cortex, long-term potentiation was impaired in the entorhinal cortex but not in the dentate gyrus, its main target region, while 24 h later it was also impaired in the dentate gyrus, revealing a spreading of long-term potentiation deficit between the two regions. Similar results were obtained upon injection of extracellular vesicles carrying Aß naturally secreted by CHO7PA2 cells, while neither Aß42 alone nor inflammatory extracellular vesicles devoid of Aß were able to propagate long-term potentiation impairment. Using optical tweezers combined to time-lapse imaging to study Aß-EV-neuron interaction, we show that Aß-EVs move anterogradely at the axon surface and that their motion can be blocked through annexin-V coating. Importantly, when Aß-EV motility was inhibited, no propagation of long-term potentiation deficit occurred along the entorhinal-hippocampal circuit, implicating large extracellular vesicle motion at the neuron surface in the spreading of long-term potentiation impairment. Our data indicate the involvement of large microglial extracellular vesicles in the rise and propagation of early synaptic dysfunction in Alzheimer's disease and suggest a new mechanism controlling the diffusion of large extracellular vesicles and their pathogenic signals in the brain parenchyma, paving the way for novel therapeutic strategies to delay the disease.

Corrigendum: Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions.

[This corrects the article DOI: 10.3389/fbioe.2019.00452.].

MicroRNA­34a­5p expression in the plasma and in its extracellular vesicle fractions in subjects with Parkinson's disease: An exploratory study.

Parkinson's disease (PD) is an important disabling age­related disorder and is the second most common neurodegenerative disease. Currently, no established molecular biomarkers exist for the early diagnosis of PD. Circulating microRNAs (miRNAs), either vesicle­free or encapsulated in extracellular vesicles (EVs), have emerged as potential blood­based biomarkers also for neurodegenerative diseases. In this exploratory study, we focused on miR­34a­5p because of its well­documented involvement in neurobiology. To explore a differential profile of circulating miR­34a­5p in PD, PD patients and age­matched control subjects were enrolled. Serial ultracentrifugation steps and density gradient were used to separate EV subpopulations from plasma according to their different sedimentation properties (Large, Medium, Small EVs). Characterization of EV types was performed using western blotting and atomic force microscopy (AFM); purity from protein contaminants was checked with the colorimetric nanoplasmonic assay. Circulating miR­34a­5p levels were evaluated using qPCR in plasma and in each EV type. miR­34a­5p was significantly up­regulated in small EVs devoid of exogenous protein contaminants (pure SEVs) from PD patients and ROC analysis indicated a good diagnostic performance in discriminating patients from controls (AUC=0.74, P<0.05). Moreover, miR­34a­5p levels in pure SEVs were associated with disease duration, Hoehn and Yahr and Beck Depression Inventory scores. These results underline the necessity to examine the miRNA content of each EV subpopulation to identify miRNA candidates with potential diagnostic value and lay the basis for future studies to validate the overexpression of circulating miR­34a­5p in PD via the use of pure SEVs.

Fourier-transform Infrared (FT-IR) spectroscopy fingerprints subpopulations of extracellular vesicles of different sizes and cellular origin.

Identification of extracellular vesicle (EV) subpopulations remains an open challenge. To date, the common strategy is based on searching and probing set of molecular components and physical properties intended to be univocally characteristics of the target subpopulation. Pitfalls include the risk to opt for an unsuitable marker set - which may either not represent the subpopulation or also cover other unintended subpopulations - and the need to use different characterization techniques and equipment. This approach focused on specific markers may result inadequate to routinely deal with EV subpopulations that have an intrinsic high level of heterogeneity. In this paper, we show that Fourier-transform Infrared (FT-IR) spectroscopy can provide a collective fingerprint of EV subpopulations in one single experiment. FT-IR measurements were performed on large (LEVs, ~600 nm), medium (MEVs, ~200 nm) and small (SEVs ~60 nm) EVs enriched from two different cell lines medium: murine prostate cancer (TRAMP-C2) and skin melanoma (B16). Spectral regions between 3100-2800 cm-1 and 1880-900 cm-1, corresponding to functional groups mainly ascribed to lipid and protein contributions, were acquired and processed by Principal Component Analysis (PCA). LEVs, MEVs and SEVs were separately grouped for both the considered cell lines. Moreover, subpopulations of the same size but from different sources were assigned (with different degrees of accuracy) to two different groups. These findings demonstrate that FT-IR has the potential to quickly fingerprint EV subpopulations as a whole, suggesting an appealing complement/alternative for their characterization and grading, extendable to healthy and pathological EVs and fully artificial nanovesicles.

Extracellular vesicles from rat-bone-marrow mesenchymal stromal/stem cells improve tendon repair in rat Achilles tendon injury model in dose-dependent manner: A pilot study.

Mesenchymal stromal/stem cells (MSCs) are increasingly employed for tissue regeneration, largely mediated through paracrine actions. Currently, extracellular vesicles (EVs) released by MSCs are major mediators of these paracrine effects. We evaluated whether rat-bone-marrow-MSC-derived EVs (rBMSCs-EVs) can ameliorate tendon injury in an in vivo rat model. Pro-collagen1A2 and MMP14 protein are expressed in rBMSC-EVs, and are important factors for extracellular-matrix tendon-remodeling. In addition, we found pro-collagen1A2 in rBMSC-EV surface-membranes by dot blot. In vitro on cells isolated from Achilles tendons, utilized as rBMSC -EVs recipient cells, EVs at both low and high doses induce migration of tenocytes; at higher concentration, they induce proliferation and increase expression of Collagen type I in tenocytes. Pretreatment with trypsin abrogate the effect of EVs on cell proliferation and migration, and the expression of collagen I. When either low- or high-dose rBMSCs-EVs were injected into a rat-Achilles tendon injury-model (immediately after damage), at 30 days, rBMSC-EVs were found to have accelerated the remodeling stage of tendon repair in a dose-dependent manner. At histology and histomorphology evaluation, high doses of rBMSCs-EVs produced better restoration of tendon architecture, with optimal tendon-fiber alignment and lower vascularity. Higher EV-concentrations demonstrated greater expression of collagen type I and lower expression of collagen type III. BMSC-EVs hold promise as a novel cell-free modality for the management of tendon injuries.

[Corrigendum] Analysis of a nanoparticle­enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis.

After the publication of the above paper, the authors noted that the names of a couple of the authors listed on the paper were associated with the wrong affliation: Specifically, the eighth and ninth listed authors, Francesca Antonaros and Allison Piovesan, are located at DIMES at the University of Florence (fourth affiliation address), not at CSGI, the Research Center for Colloids and Nanoscience in Florence (third affliation address). Therefore, the author and affiliation details for this paper should have been presented as follows: ALESSANDRO SALVI1, MARIKA VEZZOLI2, SARA BUSATTO1, LUCIA PAOLINI1,3, TERESA FARANDA1, EDOARDO ABENI1, MARIA CARACAUSI4, FRANCESCA ANTONAROS4, ALLISON PIOVESAN4, CHIARA LOCATELLI5, GUIDO COCCHI5,6, GUALTIERO ALVISI7, GIUSEPPINA DE PETRO1, DORIS RICOTTA1, PAOLO BERGESE1,3 and ANNALISA RADEGHIERI1,3. 1Department of Molecular and Translational Medicine, University of Brescia; 2Unit of Biostatistics, Department of Molecular and Translational Medicine, University of Brescia, I­25123 Brescia; 3CSGI, Research Center for Colloids and Nanoscience, Sesto Fiorentino, I­50019 Florence; 4Department of Experimental, Diagnostic and Specialty Medicine (DIMES), Unit of Histology, Embryology and Applied Biology, University of Bologna; 5Neonatology Unit, St. Orsola­Malpighi Polyclinic; 6Department of Medical and Surgical Sciences (DIMEC), University of Bologna, I­40138 Bologna; 7Department of Molecular Medicine, University of Padua, I­35121 Padua, Italy. The authors regret that this error with the author affiliations for Francesca Antonaros and Allison Piovesan was not noticed prior to the publication of their paper, and apologize for any inconvenience caused. [the original article was published in International Journal of Molecular Medicine 43: 2303­2318, 2018; DOI: 10.3892/ijmm.2019.4158].

Analysis of a nanoparticle­enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis.

Down syndrome (DS) is caused by the presence of part or all of a third copy of chromosome 21. DS is associated with several phenotypes, including intellectual disability, congenital heart disease, childhood leukemia and immune defects. Specific microRNAs (miRNAs/miR) have been described to be associated with DS, although none of them so far have been unequivocally linked to the pathology. The present study focuses to the best of our knowledge for the first time on the miRNAs contained in nanosized RNA carriers circulating in the blood. Fractions enriched in nanosized RNA­carriers were separated from the plasma of young participants with DS and their non­trisomic siblings and miRNAs were extracted. A microarray­based analysis on a small cohort of samples led to the identification of the three most abundant miRNAs, namely miR­16­5p, miR­99b­5p and miR­144­3p. These miRNAs were then profiled for 15 pairs of DS and non­trisomic sibling couples by reverse transcription­quantitative polymerase chain reaction (RT­qPCR). Results identified a clear differential expression trend of these miRNAs in DS with respect to their non­trisomic siblings and gene ontology analysis pointed to their potential role in a number of typical DS features, including 'nervous system development', 'neuronal cell body' and certain forms of 'leukemia'. Finally, these expression levels were associated with certain typical quantitative and qualitative clinical features of DS. These results contribute to the efforts in defining the DS­associated pathogenic mechanisms and emphasize the importance of properly stratifying the miRNA fluid vehicles in order to probe biomolecules that are otherwise hidden and/or not accessible to (standard) analysis.

Augmented COlorimetric NANoplasmonic (CONAN) Method for Grading Purity and Determine Concentration of EV Microliter Volume Solutions.

This protocol paper describes how to assign a purity grade and to subsequently titrate extracellular vesicle (EV) solutions of a few microliters in volume by microplate COlorimetric NANoplasmonic (CONAN) assay. The CONAN assay consists of a solution of gold nanoparticles (AuNPs) into which the EV preparation is added. The solution turns blue if the EV preparation is pure, whereas it stays red if soluble exogenous single and aggregated proteins (SAPs; often referred to as protein contaminants) are present. The color change is visible by the naked eye or can be quantified by UV-Vis spectroscopy, providing an index of purity (a unique peculiarity to date). The assay specifically targets SAPs, and not the EV-related proteins, with a detection limit <50 ng/µl (an order of magnitude higher resolution than that of the Bradford protein assay). For pure solutions, the assay also allows for determining the EV number, as the color shift is linearly dependent on the AuNP/EV molar ratio. Instead, it automatically reports if the solution bears SAP contaminants, thus avoiding counting artifacts. The CONAN assay proves to be robust and reliable and displays very interesting performances in terms of cost (inexpensive reagents, run by standard microplate readers), working volumes (1-2 µl of sample required), and time (full procedure takes <1 h). The assay is applicable to all classes of natural and artificial lipid microvesicles and nanovesicles.

Molecular Requirements for Self-Interaction of the Respiratory Syncytial Virus Matrix Protein in Living Mammalian Cells.

Respiratory syncytial virus (RSV) is an important human pathogen, which infects respiratory tract epithelial cells causing bronchiolitis and pneumonia in children and the elderly. Recent studies have linked RSV matrix (M) ability to self-interaction and viral budding. However, RSV M has been crystalized both as a monomer and a dimer, and no formal proof exists to date that it forms dimers in cells. Here, by using a combination of confocal laser scanning microscopy and bioluminescent resonant energy transfer applied to differently tagged deletion mutants of RSV M, we show that the protein can self-interact in living mammalian cells and that both the N and C-terminus of the protein are strictly required for the process, consistent with the reported dimeric crystal structure.

Intersectin goes nuclear: secret life of an endocytic protein.

Intersectin 1-short (ITSN1-s) is a 1220 amino acid ubiquitously expressed scaffold protein presenting a multidomain structure that allows to spatiotemporally regulate the functional interaction of a plethora of proteins. Besides its well-established role in endocytosis, ITSN1-s is involved in the regulation of cell signaling and is implicated in tumorigenesis processes, although the signaling pathways involved are still poorly understood. Here, we identify ITSN1-s as a nucleocytoplasmic trafficking protein. We show that, by binding to importin (IMP)α, a small fraction of ITSN1-s localizes in the cell nucleus at the steady state, where it preferentially associates with the nuclear envelope and interacts with lamin A/C. However, upon pharmacological ablation of chromosome region maintenance 1 (CRM-1)-dependent nuclear export pathway, the protein accumulates into the nucleus, thus revealing its moonlighting nature. Analysis of deletion mutants revealed that the coiled coil (CC) and Src homology (SH3) regions play the major role in its nucleocytoplasmic shuttling. While no evidence of nuclear localization signal (NLS) was detected in the CC region, a functional bipartite NLS was identified within the SH3D region of ITSN1-s (RKKNPGGWWEGELQARGKKRQIGW-1127), capable of conferring energy-dependent nuclear accumulation to reporter proteins and whose mutational ablation affects nuclear import of the whole SH3 region. Thus, ITSN1-s is an endocytic protein, which shuttles between the nucleus and the cytoplasm in a CRM-1- and IMPα-dependent fashion.

Biophysical properties of extracellular vesicles in diagnostics.

Extracellular vesicles (EVs) are cell-derived nanoparticles, involved in cell-to-cell communication, in both normal and pathological processes. Originating by the outward budding of the plasma membrane or released by exocytosis, they are natural cargoes for lipids, carbohydrates, proteins and nucleic acids. EV-based diagnostics promises unique advantages compared with conventional strategies involving whole body fluid analysis, including the reduction of biofluids complexity and more specific and sensitive detection of low abundance biomacromolecules. Besides EV cargoes, new breakthrough technologies are addressing EV 'colloidal properties' - including particle content, size and membrane mechanical properties - directly experienced by researchers to be critical factors in biomarkers discovery. This article focuses on the progresses in EV biophysical properties characterization as diagnostic tools for different pathological conditions.

Impact of the strategy adopted for drug loading in nonporous silica nanoparticles on the drug release and cytotoxic activity.

Nanoparticles are normally classified as "hard", mainly consisting of metal or metal oxide cores, or "soft", including polymer-based, liposomes and biomimetic nanoparticles. Soft nanoparticles have been studied in depth for drug formulation and therapeutic delivery applications, albeit hard nanoparticles may offer easier synthesis, smaller size and more effective tumor penetration. Among them, silica nanoparticles maintain excellent biocompatibility and biodegradability and can be finely adjusted in size and shape, easily produced in a large scale and functionalized or loaded with active molecules. To help filling the gap of a poor clinical translation of hard nanoparticles, we have designed and developed three different nonporous silica nanocarriers loading the chemotherapeutic doxorubicin within the core matrix, on the surface or both inside and outside, respectively. A comparative study was performed on drug loading and drug release, silica matrix degradation and nanodrug cytotoxic activity, highlighting unexpected correlation between the strategy adopted for drug incorporation and nanoparticle behavior in a physiological environment. This study offers a new insight on the impact of the choice of the prodrug nanoparticles on the kinetics and efficacy of drug delivery, which may encourage the scientific community in developing a new generation of drug delivery systems based on hard nanocarriers.

RNA-seq reveals distinctive RNA profiles of small extracellular vesicles from different human liver cancer cell lines.

Liver cancer (LC) is one of the most common cancers and represents the third highest cause of cancer-related deaths worldwide. Extracellular vesicle (EVs) cargoes, which are selectively enriched in RNA, offer great promise for the diagnosis, prognosis and treatment of LC. Our study analyzed the RNA cargoes of EVs derived from 4 liver-cancer cell lines: HuH7, Hep3B, HepG2 (hepato-cellular carcinoma) and HuH6 (hepatoblastoma), generating two different sets of sequencing libraries for each. One library was size-selected for small RNAs and the other targeted the whole transcriptome. Here are reported genome wide data of the expression level of coding and non-coding transcripts, microRNAs, isomiRs and snoRNAs providing the first comprehensive overview of the extracellular-vesicle RNA cargo released from LC cell lines. The EV-RNA expression profiles of the four liver cancer cell lines share a similar background, but cell-specific features clearly emerge showing the marked heterogeneity of the EV-cargo among the individual cell lines, evident both for the coding and non-coding RNA species.

Exosomes Secreted by HeLa Cells Shuttle on Their Surface the Plasma Membrane-Associated Sialidase NEU3.

Sialidases are glycohydrolases that remove terminal sialic acid residues from oligosaccharides, glycolipids, and glycoproteins. The plasma membrane-associated sialidase NEU3 is involved in the fine-tuning of sialic acid-containing glycans directly on the cell surface and plays relevant roles in important biological phenomena such as cell differentiation, molecular recognition, and cancer transformation. Extracellular vesicles are membranous structures with a diameter of 0.03-1 µm released by cells and can be detected in blood, urine, and culture media. Among extracellular vesicles, exosomes play roles in intercellular communication and maintenance of several physiological and pathological conditions, including cancer, and could represent a useful diagnostic tool for personalized nanomedicine approaches. Using inducible expression of the murine form of NEU3 in HeLa cells, a study of the association of the enzyme with exosomes released in the culture media has been performed. Briefly, NEU3 is associated with highly purified exosomes and localizes on the external leaflet of these nanovesicles, as demonstrated by enzyme activity measurements, Western blot analysis, and dot blot analysis using specific protein markers. On the basis of these results, it is plausible that NEU3 activity on exosome glycans enhances the dynamic biological behavior of these small extracellular vesicles by modifying the negative charge and steric hindrance of their glycocalyx. The presence of NEU3 on the exosomal surface could represent a useful marker for the detection of these nanovesicles and a tool for improving our understanding of the biology of these important extracellular carriers in physiological and pathological conditions.

Size distribution of extracellular vesicles by optical correlation techniques.

Understanding the colloidal properties of extracellular vesicles (EVs) is key to advance fundamental knowledge in this field and to develop effective EV-based diagnostics, therapeutics and devices. Determination of size distribution and of colloidal stability of purified EVs resuspended in buffered media is a complex and challenging issue - because of the wide range of EV diameters (from 30 to 2000nm), concentrations of interest and membrane properties, and the possible presence of co-isolated contaminants with similar size and densities, such as protein aggregates and fat globules - which is still waiting to be fully addressed. We report here a fully detailed protocol for accurate and robust determination of the size distribution and stability of EV samples which leverages a dedicated combination of Fluorescence Correlation Spectroscopy (FCS) and Dynamic Light Scattering (DLS). The theoretical background, critical experimental steps and data analysis procedures are thoroughly presented and finally illustrated through the representative case study of EV formulations obtained from culture media of B16 melanoma cells, a murine tumor cell line used as a model for human skin cancers.

Cultured human amniocytes express hTERT, which is distributed between nucleus and cytoplasm and is secreted in extracellular vesicles.

BACKGROUND: An increasing number of studies on stem cells suggests that the therapeutic effect they exert is primarily mediated by a paracrine regulation through extracellular vesicles (EVs) giving solid grounds for stem cell EVs to be exploited as agents for treating diseases or for restoring damaged tissues and organs. Due to their capacity to differentiate in all embryonic germ layers, amniotic fluid stem cells (AFCs), represent a highly promising cell type for tissue regeneration, which however is still poorly studied and in turn underutilized. In view of this, we conducted a first investigation on the expression of human hTERT gene - known to be among the key triggers of organ regeneration - in AFCs and in the EVs they secrete. METHODS: Isolated AFCs were evaluated by RT-qPCR for hTERT expression. The clones expressing the highest levels of transcript, were analyzed by Immunofluorescence imaging and Nuclear/cytoplasmic fractionation in order to evaluate hTERT subcellular localization. We then separated EVs from FBS depleted culture medium by serial (ultra) centrifugations steps and characterized them using Western blotting, Atomic force Microscopy and Nanoplasmonic assay. RESULTS: We first demonstrated that primary cultures of AFCs express the gene hTERT at different levels. Then we evidenced that in AFCs with the higher transcript levels, the hTERT protein is present in the nuclear and cytoplasmic compartment. Finally, we found that cytosolic hTERT is embodied in the EVs that AFCs secrete in the extracellular milieu. CONCLUSIONS: Our study demonstrates for the first time the expression of the full protein hTERT by AFCs and its release outside the cell mediated by EVs, indicating a new extra telomeric role for this protein. This finding represents an initial but crucial evidence for considering AFCs derived EVs as new potential sources for tissue regeneration.

Residual matrix from different separation techniques impacts exosome biological activity.

Exosomes are gaining a prominent role in research due to their intriguing biology and several therapeutic opportunities. However, their accurate purification from body fluids and detailed physicochemical characterization remain open issues. We isolated exosomes from serum of patients with Multiple Myeloma by four of the most popular purification methods and assessed the presence of residual contaminants in the preparations through an ad hoc combination of biochemical and biophysical techniques - including Western Blot, colloidal nanoplasmonics, atomic force microscopy (AFM) and scanning helium ion microscopy (HIM). The preparations obtained by iodixanol and sucrose gradients were highly pure. To the contrary, those achieved with limited processing (serial centrifugation or one step precipitation kit) resulted contaminated by a residual matrix, embedding the exosomes. The contaminated preparations showed lower ability to induce NfkB nuclear translocation in endothelial cells with respect to the pure ones, probably because the matrix prevents the interaction and fusion of the exosomes with the cell membrane. These findings suggest that exosome preparation purity must be carefully assessed since it may interfere with exosome biological activity. Contaminants can be reliably probed only by an integrated characterization approach aimed at both the molecular and the colloidal length scales.