Nanoparticles In Aqueous Solution Research Articles

A facile and one-pot aqueous phase transfer of oleylamine capped Au NP with aminophenylboronic acid used as transfer and targeting ligand

Although various phase transfer techniques have been used to make hydrophobic nanoparticles (NPs) water-soluble. However, these techniques have been limited by inefficient surface modification strategy that often stable NPs in aqueous solutions. Herein, we report the use of 3-aminophenylboronic acid (3-APBA) as a hydrophilic ligand for phase transfer of oleylamine (OA) capped Au NPs (OA@Au NPs) from non-hydrolytic system into aqueous solutions. The 3-APBA capped Au NPs (3-APBA@Au NPs) was mainly characterized using different analytical techniques to substantiate the efficiency of the phase transfer procedure. In this simple procedure, 3-APBA molecule was simultaneously used as both phase transfer and targeting ligand for bacteria recognition in one step. In principle, while free electron pair of amin (:NH2) group of 3-APBAbind to surface of hydrophobic Au NPs for phase transfer, diol group can bind to glycan on the membrane of Staphylococcus aureus and Methicillin-resistant Staphylococcus aureus (MRSA) through proper cis-diol configuration. In addition, the resulting 3-APBA@Au NP can effectively catalyze the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) in the presence of sodium borohydride (NaBH4) in aqueous solution.

Evaluation of Sonocatalytic and Photocatalytic Processes Efficiency for Degradation of Humic Compounds Using Synthesized Transition-Metal-Doped ZnO Nanoparticles in Aqueous Solution

The existence of a humic substance in water causes the growth of microorganisms and reduces the quality of water; therefore, the removal of these materials is crucial. Here, the ZnO nanoparticles doped using transition metals, copper (Cu) and manganese (Mn), were used as an effective catalyst for photocatalytic removal of humic substances in an aqueous environment under ultraviolet, visible light, and light-emitting diode irradiations. Also, we study the effect of the sonocatalytic method. A solvothermal procedure is used for doping, and the Cu- and Mn-doped ZnO nanocatalyst were characterized by means of FTIR, XRD, AFM, SEM, and EDAX analyses. We investigate the effect of operational variables, including doping ratio, initial pH, catalyst dose, initial HS content, and illuminance on the removal efficiency of the processes. The findings of the analyses used for the characterization of the nanoparticles illustrate the appropriate synthesis of the Cu- and Mn-doped ZnO nanocatalysts. We observe the highest removal efficiency rate under acidic conditions and the process efficiency decreased with increasing solution pH, when we tested it in the range of 3–7. Photocatalytic decomposition of HS increases with a rise in catalyst dose, but an increase in initial HS content results in decreasing the removal efficiency. We observe the highest photocatalytic degradation of humic acid while using the visible light, and the highest removal efficiency is obtained using Cu.ZnO. The Cu.ZnO also shows better performance under ultraviolet irradiation compared to other agents.

Identification and application of a neutralizing epitope within alpha-hemolysin using human serum antibodies elicited by vaccination

Staphylococcus aureus (SA), especially the methicillin-resistant variant (MRSA), is becoming a serious threat to human health in hospitals and communities, making the development of an effective vaccine urgent. Alpha-hemolysin (Hla) is a key virulence factor and also a good target for the development of SA vaccines. However, the epitopes in Hla recognized by human immunity are not characterized in detail, which hinders the design of epitope-based human vaccines against SA. In this study, we collected sera from volunteers in a phase 1b clinical trial of a novel recombinant five-antigen SA vaccine (NCT03966040). Using a Luminex-based assay, we characterized the human serologic response against Hla, and identified Hla121-138 as a neutralizing epitope. In addition, we successfully produced ferritin nanoparticles carrying the neutralizing Hla121-138 epitope (EpNP) in E. coli. EpNP presented as homogenous nanoparticles in aqueous solution. Immunization with EpNP elicited potent hemolysis-neutralizing antibodies and conferred significant protection in a mouse model of SA skin infection. Our data suggest that EpNP, carrying the neutralizing epitope Hla121-138, is a good candidate for a vaccine against SA.

An insight into cyclocurcumin cis–trans isomerization: Kinetics in solution and in the presence of silver nanoparticles

Cyclocurcumin (CyCUR) is a non-diarylheptanoid curcuminoid characterized by an α,β-unsaturated dihydropyranone moiety generally existing as trans isomer in the ground state but able to convert into the cis form by photoisomerization. Herein the kinetics of thermal cis–trans isomerization of cyclocurcumin was spectroscopically determined in ethanol, pure water and silver nanoparticles (AgNPs) aqueous solution. Energetic parameters were calculated by Arrhenius and Eyring plots in the temperature range 294–314 K. The presence of AgNPs increases the rate of the reaction, according to the polarizability of the environment. The solvatochromism of cyclocurcumin was also studied by using the Catalán empirical solvent parameters scale in a series of organic solvents. The bathochromic shift of CyCUR suggests that polarizability of the medium plays the major role in the investigated conditions.

Encapsulation and Delivery of Dimethylcurcumin by Using Nanoparticles of a Polyethylene‐Glycol‐Based Dimethylcurcumin Prodrug

AbstractDimethylcurcumin (DMC) is a synthetic curcuminoid which can enhance androgen receptor (AR) degradation to suppress AR‐associated cancers. However, the extremely poor water solubility and low biocompatibility of DMC significantly limit its biomedical applications. Herein, a water soluble DMC prodrug mPEG‐DMC (7.4 %) with DMC loading content of 7.4 % was synthesized and further used for preparation of free DMC loaded nanoparticles (NPs) for delivery of both covalently bound and free DMC. mPEG‐DMC (7.4 %) can self‐assemble into nanoparticles in aqueous solution and can encapsulate free DMC with high drug loading content and encapsulation efficiency. The average hydrodynamic diameters of the prepared NPs are between 90 and 140 nm, and increase with increasing DMC loading content. The in vitro drug release study shows that the DMC@mPEG‐DMC (15.5 %) and DMC@mPEG‐DMC (18.6 %) NPs exhibit pH‐triggered DMC release behaviors. The cellular uptake study shows that DMC@mPEG‐DMC (18.6 %) NPs exhibit enhanced cellular uptake as compared to free DMC and DMC@mPEG‐DMC (15.5 %) NPs. DMC@mPEG‐DMC (15.5 %) and DMC@mPEG‐DMC (18.6 %) NPs exhibit similar cytotoxicity and AR protein suppression effect on HepG2 cells and 22Rv1 cells as compared to free DMC. The DMC@mPEG‐DMC (15.5 %) and DMC@mPEG‐DMC (18.6 %) NPs developed in this work provide two water soluble and effective nanoformulations of DMC.

Enzymatic enhancing of triplet\u2013triplet annihilation upconversion by breaking oxygen quenching for background-free biological sensing

Triplet-triplet annihilation upconversion nanoparticles have attracted considerable interest due to their promises in organic chemistry, solar energy harvesting and several biological applications. However, triplet-triplet annihilation upconversion in aqueous solutions is challenging due to sensitivity to oxygen, hindering its biological applications under ambient atmosphere. Herein, we report a simple enzymatic strategy to overcome oxygen-induced triplet-triplet annihilation upconversion quenching. This strategy stems from a glucose oxidase catalyzed glucose oxidation reaction, which enables rapid oxygen depletion to turn on upconversion in the aqueous solution. Furthermore, self-standing upconversion biological sensors of such nanoparticles are developed to detect glucose and measure the activity of enzymes related to glucose metabolism in a highly specific, sensitive and background-free manner. This study not only overcomes the key roadblock for applications of triplet-triplet annihilation upconversion nanoparticles in aqueous solutions, it also establishes the proof-of-concept to develop triplet-triplet annihilation upconversion nanoparticles as background free self-standing biological sensors.

Oral delivery of antioxidant enzymes for effective treatment of inflammatory disease

Oral administration of protein is very challenging for therapeutic applications due to its instability and easy degradation in the gastrointestinal tract. Herein, we reported an approach to encapsulate native anti-inflammatory proteins in wind chimes like cyclodextrin (WCC) for efficient oral protein delivery. The amphiphilic WCC can self-assemble into nanoparticles in aqueous solution and achieve superior encapsulation of two antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) by simply mixing with protein solution, avoiding any extra cumbersome steps that might inactivate protein. WCC nanovehicles can effectively protect enzyme activity and enhance their intracellular delivery. SOD and CAT co-loaded WCC nanoparticles (SC/WCC) can integrate the synergistic effect of SOD and CAT for enhancing the removal of reactive oxygen species (ROS), effectively inhibit the inflammatory response by reducing the secretion of proinflammatory factors and protect cells from ROS-induced oxidative damage. In the mouse colitis model, SC/WCC administered orally was able to efficiently accumulate in the inflamed colon, significantly inhibited the expression of proinflammatory mediators and notably alleviated the symptoms related to colitis. Therefore, we believe that the strategies we described here may provide a convenient and powerful platform for the treatment of other inflammatory diseases.

A low cost and open access system for rapid synthesis of large volumes of gold and silver nanoparticles

Rapid synthesis of nanomaterials in scalable quantities is critical for accelerating the discovery and commercial translation of nanoscale-based technologies. The synthesis of metal nanogold and silver in volumes larger than 100 mL is not automatized and might require of the use of harsh conditions that in most cases is detrimental for the production of nanoparticles with reproducible size distributions. In this work, we present the development and optimization of an open-access low-cost NanoParticle Flow Synthesis System (NPFloSS) that allows for the rapid preparation of volumes of up to 1 L of gold and silver nanoparticle aqueous solutions.

Influence of optical radiation on the silver nanoparticles formation

In this work, the synthesis of spherical silver nanoparticles in aqueous solution was performed by photostimulated reduction. A research of the laser exposure time effect of silver colloids on the optical response and nanoparticles concentration in the studied solution was carried out. The influence of long time exposure (up to 6 days) of silver colloid by LEDs with radiation wavelengths of 525 and 633 nm on their geometric, spatial and optical parameters was studied. It has been shown that prolonged irradiation of silver colloid leads to changes in the nanoparticles morphology, which is confirmed by a change in the colloidal color and appearance of additional plasmon absorption peaks on the spectral scale. The formation of silver nanoparticles and nanoprisms in aqueous solution was confirmed by spectrophotometry and transmission electron microscopy. Modelling of absorption spectra of triangular silver nanoparticles by the discrete dipole approximation approach, implemented in DDSCAT software, was carried out.. The electromagnetic radiation of the optical range is a promising tool that can be effectively used for both synthesis and modification of optical and spatial parameters of silver nanoparticles.

Co-delivery of antibiotic and baicalein by using different polymeric nanoparticle cargos with enhanced synergistic antibacterial activity

To evaluate the effect of polymer structures on their unique characteristics and antibacterial activity, this study focused on developing amphiphilic copolymers by using three different molecules through RAFT polymerization. Three amphiphilic copolymers, namely, PBMA-b-(PDMAEMA-r-PPEGMA) (BbDrE), (PBMA-r-PDMAEMA)-b-PPEGMA (BrDbE), and PBMA-r-PDMAEMA-r-PPEGMA (BrDrE), are successfully self-assembled into spherical or oval shaped nanoparticles in aqueous solution and remain stable in PBS, LB, and 10% FBS solutions for at least 3 days. The critical micelle concentrations are 0.012, 0.025, and 0.041 mg/mL for BbDrE, BrDbE, and BrDrE, respectively. The zeta potential values under pH 5.5 and pH 7.4 conditions are 3.18/0.19, 8.57/0.046, and 2.54/-0.69 mV for BbDrE, BrDbE, and BrDrE nanoparticles, respectively. The three copolymers with similar monomer compositions show similar molecular weight and thermostability. Baicalein (BA) and ciprofloxacin (CPX) are encapsulated into the three nanoparticles to obtain BbDrE@BA/CPX, BrDbE@BA/CPX, and BrDrE@BA/CPX nanocomposites, with LC values of 63.9/78.3, 63.9/74.7, and 55.3/64.8, respectively. The two drugs are released from the three drug-loaded nanocomposites with 60%–95% release in pH 5.5 over 24 h and 15%–30% release in pH 7.4. The drug-loaded nanocomposites show synergistic antibacterial activity than the naked drug (2–8 fold reduction for CPX) or single drug-loaded nanocomposites (4–8 fold reduction for CPX) against Pseudomonas aeruginosa and Staphylococcus aureus. The drug-loaded nanocomposites inhibit the formation of bacterial biofilms above their MIC values and eliminate bacterial biofilms observed by fluorescent microscope. Finally, the nanocomposites improve the healing of infection induced by P. aeruginosa and S. aureus on rat dermal wounds. These results indicate that antimicrobial agents with different structures could be an alternative treatment strategy for bacteria-induced infection.

Investigation of Commercial Iron Oxide Nanoparticles: Structural and Magnetic Property Characterization.

Magnetic nanoparticles (MNPs) have been extensively used as tiny heating sources in magnetic hyperthermia therapy, contrast agents in magnetic resonance imaging, tracers in magnetic particle imaging, carriers for drug/gene delivery, etc. There have emerged many MNP/microbead suppliers since the past decade, such as Ocean NanoTech, Nanoprobes, US Research Nanomaterials, Miltenyi Biotec, micromod Partikeltechnologie GmbH, nanoComposix, and so forth. In this paper, we report the physical and magnetic characterizations on iron oxide nanoparticle products from Ocean NanoTech. Standard characterization tools such as vibrating-sample magnetometry, X-ray diffraction, dynamic light scattering, transmission electron microscopy, and zeta potential analysis are used to provide MNP customers and researchers with an overview of these iron oxide nanoparticle products. In addition, the dynamic magnetic responses of these iron oxide nanoparticles in aqueous solutions are investigated under low- and high-frequency alternating magnetic fields, giving a standardized operating procedure for characterizing the MNPs from Ocean NanoTech, thereby yielding the best of MNPs for different applications.

Development of an Innovative and Green Method to Obtain Nanoparticles in Aqueous Solution from Carbon-Based Waste Ashes.

In this study, an original and green procedure to produce water-based solutions containing nanometric recycled carbon particles is proposed. The nanometric particles are obtained starting from carbon waste ashes, produced by the wooden biomass pyro-gasification plant CMD (Costruzioni motori diesel) ECO20. The latter is an integrated system combining a downdraft gasifier, a spark-ignition internal combustion engine, an electric generator and syngas cleaning devices, and it can produce electric and thermal power up to 20 kWe and 40 kWth. The carbon-based ashes (CA) produced by the CMD ECO20 plant were, first, characterized by using differential scanning calorimetry (DSC) and microcomputed tomography (microCT). Afterward, they were reduced in powder by using a milling mortar and analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectrometry, thermogravimetric analysis (TGA), X-ray diffraction (WAXD) and Fourier-transform infrared (FTIR) spectroscopy. The optimization of an original procedure to reduce the dimensions of the ashes in an aqueous solution was then developed by using ball milling and sonication techniques, and the nanometric dimensions of the particles dispersed in water were estimated by dynamic light scattering (DLS) measurements in the order of 300 nm. Finally, possible industrial applications for the nanomaterials obtained from the waste ashes are suggested, including, for example, inks for Aerosol Jet® Printing (AJ® P).

High-speed continuous production of polymeric nanoparticles with improved stability using a self-aligned coaxial turbulent jet mixer

Continuous synthesis of polymeric nanoparticles (NPs) has been intensively studied due to its great potential to produce NPs with the physicochemical properties of reproducibility and controllability. Here, we developed a self-aligned coaxial turbulent jet mixer for high-speed continuous synthesis of polymeric NPs. The coaxial turbulent jet mixer can be constructed using commercial tube fittings and tubes. Since those fluidic components are self-aligned coaxially, leak-free jet mixers can be assembled without the use of tools or specialized skills in robust manner. Using the jet mixer with polystyrene (PS) solution, uniform polymeric NPs can be synthesized in a fully continuous manner, for which diaphragm pumps and pulsation dampers are used for continuous control of the flow. We also improved the dispersion stability of the PS NPs in aqueous solution against centrifugation by introducing polystyrene-poly(ethylene oxide) diblock copolymer (PS-b-PEO) as steric stabilizer. The NPs prepared using the coaxial turbulent jet mixer were smaller and more uniform in size compared to NPs synthesized by a bulk nanoprecipitation method.

Preparation and invitro evaluation of amphiphilic paclitaxel small molecule prodrugs and enhancement of oral absorption.

A series of novel amphiphilic paclitaxel (PTX) small molecule prodrugs, PTX-succinic anhydride-cystamine (PTX-Cys), PTX-dithiodipropionic anhydride (PTX-SS-COOH) and PTX-succinic anhydride-cystamine-valine (PTX-SS-Val) were designed, synthesized and evaluated against cancer cell lines. Compared with paclitaxel, these prodrugs contained water-soluble groups such as amino, carboxyl and amino acid, which improved the aqueous solubility of the prodrugs. More importantly, the valine was introduced in PTX-SS-Val molecule and made the molecule conform to the structural characteristics of intestinal oligopeptide transporter PEPT1 substrate. Thus the oral bioavailability of prodrug could be improved because of the mediation of PEPT1 transporter. These small molecule paclitaxel prodrugs could self-assemble into nanoparticles in aqueous solution, which effectively improved the solubility of paclitaxel, and had certain stability in pH 6.5, pH 7.4 buffer solutions and simulated gastrointestinal fluids. Some of these prodrugs, especially for PTX-Cys and PTX-SS-Val, exhibited nearly equal or slightly better anticancer activity when compared to paclitaxel. Further studies on PTX-Cys and PTX-SS-Val showed that both had good intestinal absorption in the rat single-pass intestinal perfusion (SPIP) experiments. Oral pharmacokinetic experiments showed that PTX-SS-Val could effectively improve the oral bioavailability of PTX.

Electrolytic synthesis of metallic zinc nanoparticles

The present paper describes fabrication of metallic zinc (Zn) nanoparticles in aqueous solution. An aqueous colloidal solution containing metallic Zn nanoparticles was prepared by electrolysis of Zn salt aqueous solution using two metallic Zn plate electrodes. In methods A and B, sonication was performed after and during the electrolysis, respectively. As a result, method B was found to be suitable for synthesis of metallic Zn nanoparticles without producing large particles with sizes from a few micrometers to a few tens of micrometers. Investigation of the effect of electrolysis time revealed that the metallic Zn nanoparticles were produced in three steps: (1) the hexagonal plate-shaped particles were produced on the cathode, (2) the particles were peeled off the cathode and dispersed in the solution, and (3) the dispersed particles were broken apart in the solution phase by sonication to form smaller particles. Particle size decreased with decreasing ultrasonic wave frequency based on attenuation in medium and/or cavitation stability and decreasing current based on a decrease in reduction rate. As a result, metallic Zn nanoparticles as small as 19.1 ± 5.1 nm were fabricated in 1 h at 28 kHz and 0.03 A.

Synthesis of gold nanoparticles in aqueous solutions not containing additional interfering components using sulfite method: the effect of thiol-containing acid additives

Stable solutions of gold nanoparticles with an average diameter of 13 nm and CAu = 5×10–4 M were obtained by the reduction of HAuCl4 with an equivalent amount of sodium sulfite at 80–100 °C in the presence of 2% PEG 6000 as a stabilizer: AuCl4– + 3/2 SO32– + 3/2 H2O → Au0 + 3/2 SO42– + 3 H+ + 4 Cl–. The resulting solutions of nanoparticles do not contain additional components capable of complexation, redox, and acid-based interactions. The effect of additives of thiourea, cysteine, thiomalate, and glutathione at various pH on the stability of such solutions to the aggregation has been studied. It was shown that the values of the protonation constants and charges of species of a thiol-containing component are not the only factors determining stability. Using thiomalate (HTM2–) as an example, it was shown also that at pH 7–8, the chemisorption is not followed by the release of H+ ions into the solution.

Rational Design of a Polymer-Based Ratiometric K+ Indicator for High-Throughput Monitoring Intracellular K+ Fluctuations.

Highly selective fluorescent K+ sensors are of great importance for monitoring K+ fluctuations in various biological processes. In particular, highly efficient ratiometric K+ sensors that can emit in dual wavelengths and facilitate the quantitative determination of K+ are highly anticipated. Herein, we present the first polymer-based ratiometric fluorescent K+ indicator (PK1) for quantitatively detecting K+ in aqueous solutions and high-throughput monitoring K+ fluctuations in living cells. PK1 was synthesized by conjugating a small molecular K+ probe and a red emission reference dye to a hydrophilic polymer skeleton. The newly synthesized PK1 can form highly stable nanoparticles in aqueous solutions and work in 100% water without the aid of any organic solvents or surfactants. PK1 is sensitive to K+ with a fluorescence enhancement of sevenfold after interactions with K+ at 1000 mM and inert to other metal ions, physiological pH, or dye concentration vibrations. More importantly, the fluorescence intensity ratio at 572 and 638 nm is linearly correlated with log [K+] in the range of 2-500 mM (R2 = 0.998), which will facilitate the quantitative detection of K+. Practical application of PK1 in detecting different K+-rich samples demonstrates its great potential in quantitative detection of K+. PK1 can be quickly internalized by live cells and shows no obvious cytotoxicity. We also demonstrate that PK1 could be used for monitoring K+ fluctuations under different stimulations by using a confocal microscope and especially a microplate reader, which is high throughput and time saving. The rational design of PK1 will broaden the design concept of ratiometric fluorescent K+ sensors and facilitate the quantitative detection of K+.

Redox-sensitive carrier-free nanoparticles self-assembled by disulfide-linked paclitaxel-tetramethylpyrazine conjugate for combination cancer chemotherapy.

Rationale: Combinations of two or more therapeutic agents targeting different signaling pathways involved in tumor progression can have synergistic anticancer effects. However, combination chemotherapies are greatly limited by the different pharmacokinetics, tumor targeting, and cellular uptake capacities of the combined drugs. We have previously demonstrated the potential synergistic efficacy of paclitaxel (PTX) and the natural anti-angiogenic agent tetramethylpyrazine (TMP) for suppressing ovarian carcinoma growth. An efficient, facile, and smart nanosystem to deliver PTX and TMP simultaneously in vivo is greatly desired.Methods: We constructed a redox-sensitive nanosystem based on the amphiphilic PTX-ss-TMP conjugate, in which PTX and TMP are linked by a disulfide bond. We characterized the structure of the drug conjugate by 1H NMR and LC-MS, and then prepared PTX-ss-TMP NPs by a one-step nanoprecipitation method. We investigated the redox sensitivity, tumor-targeting ability, anticancer efficacy, and anti-angiogenesis activity of PTX-ss-TMP NPs in vitro and in vivo.Results: The amphiphilic PTX-ss-TMP conjugate readily self-assembled into stable nanoparticles in aqueous solution with a low critical association concentration of 1.35 µg/mL, well-defined spherical structure, small particle size (152 nm), high drug loading, redox-responsive drug release, high biocompatibility, and high storage stability. In cancer cells pretreated with GSH-OEt, PTX-ss-TMP NPs exhibited higher cytotoxicity, apoptosis rate, and cell-cycle arrest than monotherapy or combination therapy with free drugs, which was attributed to their improved cellular uptake and rapid intracellular drug release. Additionally, PTX-ss-TMP NPs also had a stronger anti-angiogenesis effect in HUVECs than free drug, which was mediated by VEGFR2-involved downstream signals. Finally, PTX-ss-TMP NPs showed tumor-specific accumulation and excellent antitumor activity in A2780 xenograft mice compared with free drug.Conclusions: These in vitro and in vivo results provide clear evidence that this redox-responsive carrier-free nanosystem with intrinsic amphiphilicity has great potential for combination cancer chemotherapy.

Catalytic hydrogenation of CO2 from air via porous silica-supported Au nanoparticles in aqueous solution

A one-pot, two-step process catalyzed by Au/SiO2 is able to convert CO2 to C1 products in the absence of an organic solvent.

Determination of the valence band edge of Fe oxide nanoparticles dispersed in aqueous solution through resonant photoelectron spectroscopy from a liquid microjet.

We use X-ray photoemission and a near ambient pressure with a liquid microjet setup to investigate the electronic structure of FeOOH nanoparticles dispersed in aqueous solution. In particular, we show that by using X-ray resonant photoemission in dilute solutions, we can overcome the limits of conventional photoemission such as low nanoparticle-to-solvent signal ratio, and local nanoparticle charging and measure the valence band structure of FeOOH nanoparticles in aqueous solution with chemical specificity. The resonant photoemission signal across the Fe 2p3/2 absorption edge is measured for 2 wt% aqueous solutions of FeOOH nanoparticles (NPs) and the valence band maximum (VBM) of the hydrated FeOOH nanoparticles is determined. We compare the obtained VBM value in aqueous solution to that of FeOOH NPs in the dry phase. We show that the valence band edge position of NPs in the liquid phase can be accurately predicted from the values obtained in the dry phase provided that a simple potential shift due to solution chemistry is applied. Our results demonstrate the suitability of resonant photoemission in measuring the electronic structure of strongly diluted nanosystems where the conventional non-resonant photoemission technique fails.