Taylor dispersion analysis of metallic-based nanoparticles - A short review.

Taylor dispersion analysis (TDA) is an interesting tool for nanoparticle (NP) size determination, feasible using simple capillary electrophoresis apparatus. Based upon the radial diffusion of analytes upon a laminar stream, the diffusion coefficient of species is easily estimable. Moreover, TDA is generally more adequate than conventional dynamic light scattering methodologies as it is less dependent on the polydispersity of the sample, leading to accurate measurement and reliable results. This review provides every paper mentioning the use of TDA for metallic-based NPs size determination. Diverse strategies for the detection of metallic NPs (like UV-visible and inductively coupled plasma-mass spectrometry - ICP-MS - for instance) and interpretation of the Taylorgrams are discussed. Based upon the literature, advices on future prospects are also indicated, especially for the comparison of TDA results with other classical techniques.

Analytical strategy for studying the formation and stability of multilayered films containing gold nanoparticles.

The design of layer-by-layer (LbL) polyelectrolyte films including nanoparticles is a growing field of innovation in a wide range of biomedical applications. Gold nanoparticles (AuNPs) are very attractive for further biomolecule coupling to induce a pharmacological effect. Nanostructured LbL films coupled with such metallic species show properties that depend on the conditions of construction, i.e. the polymer nature and dissolution buffer. Tripartite LbL films (polycation, AuNP, and polyanion) were evaluated using two different polycationic polymers (poly(allylamine hydrochloride) (PAH), poly(ethylene imine) (PEI)) and various medium conditions (salts, i.e. phosphate, Tris or Tris-NaCl buffers, and concentration). AuNP incorporation and film stability were analysed by visible spectrophotometry, capillary zone electrophoresis, a quartz crystal microbalance, and high-performance liquid chromatography. The ideal compromise between AuNP loading and film stability was obtained using PAH prepared in Tris-NaCl buffer (0.01-0.15 M). This condition allowed the formation of a LbL film that was more stable than the film with PEI and provided an AuNP quantity that was 4.8 times greater than that of the PAH-PBS-built film. In conclusion, this work presents an analytical strategy for the characterization of nanostructured multilayer films and optimization of LbL films enriched with AuNPs to design biomedical device coatings.

Albumin as a carrier for NO delivery: preparation, physicochemical characterization, and interaction with gold nanoparticles.

BACKGROUND: Nitric oxide (NO) is a gaseous transmitter playing numerous physiological roles and characterized by a short half-life. Its binding to endogenous thiols increases its stability, facilitating its storage and transport. The purpose of this study was to investigate the nitrosated serum albumin (SA-SNO) and to provide a reference for its easy preparation for further use in in vitro studies. METHODS: Serum albumin (SA) was S-nitrosated by reacting with (i) NaNO2 in acidic medium; (ii) different low-molecular weight S-nitrosothiols (RSNO) (S-nitrosocysteine (CysNO), S-nitrosoglutathione (GSNO), and S,S'-dinitrosobucillamine (Buc(NO)2)); and (iii) diethylamine NONOate (DEA/NO). SA-SNO was purified by size exclusion chromatography and the S-nitrosation site and the rate were studied by mass spectrometry and Griess-Saville assay, respectively. Then, SA-SNO was characterized by spectrofluorimetry, dynamic light scattering, and circular dichroism. Finally, SA-SNO reactivity with citrate stabilized gold nanoparticles (AuNP-citrate) was investigated via determination of NO release. RESULTS: S-nitrosation rates of SA were 90.1 ± 3.3, 76.8 ± 2.7, 80.3 ± 3.2, 84.8 ± 5.0, and 15.4 ± 1.9% (n = 5), when SA was reacted with acidified NaNO2, CysNO, GSNO, Buc(NO)2, and DEA/NO, respectively. The physicochemical characterization indicated that the resulting product corresponded to a mono-S-nitrosothiol (on cysteine-34), and the conformational construction remained unchanged. Stability studies showed that the NO content was preserved over 1 week. AuNP-citrate reacted with SA-SNO with increase of its hydrodynamic diameter but preservation of SNO bond. CONCLUSIONS: SA-SNO prepared and stored under the reported conditions affords a well-defined reference suitable for in vitro studies.

Cross-frontal mode: An alternative methodology for Taylor dispersion analysis of monomodal sample.

Taylor dispersion analysis (TDA) is a technique dedicated to the determination of the molecular diffusion coefficient (D) of species, using band broadening of an analyte in a laminar flow. Two modes are commonly used to perform TDA: pulse and frontal modes. In each case, a fitting of the signal is required. We propose here a third mode denoted as cross-frontal mode, combining two crossed sample fronts without modification of a classical CE device for the rapid and accurate determination of D of caffeine, reduced glutathione (GSH), insulin from bovine pancreas, bovine serum albumin (BSA) and citrate-capped gold nanoparticles (AuNP). Theoretical aspects and methodology are described, showing a good correlation between the so-called cross-frontal mode and usual frontal mode. Limitations of the techniques are also assessed, and are similar to regular modes while no fitting is required. This new methodology allows improving the sensitivity toward low concentrated sample compared to pulse mode, and an alternative mathematical treatment compared to regular TDA modes.

Gold nanostructured membranes to concentrate low molecular weight thiols, a proof of concept study.

Thiols are very important molecules in the biomedical field involved for example in redox homeostasis. Their detection and quantification remain difficult due to their poor stability (oxidation) linked to their strong reactivity towards other thiols (by the formation of S-S bonds) or other interfering molecules in the medium. Cellulose membranes with immobilized gold nanoparticles (AuNP) were developed to capture and quantify thiols in simple and complex matrices. This device was first optimized and characterized in terms of nanostructuration and thiol adsorption. N-Acetylcysteine (NAC) and reduced glutathione (GSH), chosen as model molecules, were filtered through the device demonstrating a maximal adsorption capacity of 270 and 60 nmol respectively. In a second step, the adsorbed species were subjected to ligand exchange using a more reactive thiol, dithiothreitol. The results showed release rates of approximately 90% for NAC and GSH. Finally, the amount of endogenous GSH in rat plasma was determined without any pretreatment. For the first time to our knowledge, a nanostructured device for the capture, selective and sensitive quantification of thiols is proposed. This device is easy to handle and overcomes matrix effects. Moreover, the very large concentration factor induced by this technology will be a valuable asset to decrease the quantification limits of analytical methods.

Design of surface ligands for blood compatible gold nanoparticles: Effect of charge and binding energy.

Gold nanoparticle (AuNP) interaction with the blood compartment as a function of their charge and the binding energy of their surface ligand was explored. Citrate, polyallylamine and cysteamine stabilized AuNP along with dihydrolipoic acid and polyethylene glycol capped AuNP were synthesized and fully characterized. Their interactions with model proteins (human albumin and human fibrinogen) were studied. Complexes formed between AuNP and protein revealed several behaviors ranging from corona formation to aggregation. Protein fluorescence quenching as a function of temperature and AuNP concentration allowed the determination of the thermodynamic parameters describing these interactions. The hemolysis induced by AuNP was also probed: an increasing or a decreasing of hemolysis ratio induced by AuNP was observed as of function of protein corona formation. Taken together, our results drew up a composite sketch of an ideal surface ligand for blood compatible AuNP. This capping agent should be strongly bound to the gold core by one or more thiol groups and it must confer a negative charge to the particles.

Nanotechnologies for Medical Devices: Potentialities and Risks.

Many novel medical devices (implantable or not) include nanomaterials through either surface-coating by nanoparticles or by direct nanostructuration of the surface. In this review, we have identified several medical devices currently on the market in various health domains (wound healing, prevention or treatment of infectious diseases, cardio-vascular diseases, organ or joint replacement, and finally medical devices associated with nanomedicines). The very peculiar physicochemical characterization of the nanostructured medical devices is described. Keys to understand their possible interaction with the organism (positive or negative via toxicity) are given. Finally, as a conclusion, we discuss the specific quality control as well as the regulatory issues arising from the lack of regulation for approving nanomaterial combining medical devices.

Quality control of gold nanoparticles as pharmaceutical ingredients.

Nanoparticles are being developed for a wide range of medical applications such as, controlled release, drug delivery systems or imagery, theranostics, implants…. For the moment, there is no legal definition of nanoparticles or nanomaterials for therapeutic use. The specific case of gold nanoparticles is not an exception: their current definition as nanoparticle material does not correspond to classic pharmaceutical ingredients as described in Pharmacopoeias. In this study, more than 30 different batches of citrate stabilized gold nanoparticles (AuNP) were synthesized and analyzed thanks to both classical approaches (UV-Vis spectrophotometry, dynamic light scattering coupled or not to electrophoresis …) and capillary zone electrophoresis (CZE) coupled to diode array detection to assess their purity and impurity profiles. These techniques led to the beginning of defined specifications, a key step for the use of gold nanoparticles as pharmaceutical ingredients. CZE was demonstrated suitable to evaluate a batch-to-batch quality control, to monitor the purification processes and to follow the stability of 18 different batches for 20 days. Finally, commercially available AuNP samples were tested and the results compared to the provided certificates of analysis.

Highly sensitive and simple liquid chromatography assay with ion-pairing extraction and visible detection for quantification of gold from nanoparticles.

A simple isocratic HPLC method using visible detection was developed and validated for the quantification of gold in nanoparticles (AuNP). After a first step of oxidation of nanoparticles, an ion-pair between tetrachloroaurate anion and the cationic dye Rhodamine B was formed and extracted from the aqueous media with the help of an organic solvent. The corresponding Rhodamine B was finally quantified by reversed phase liquid chromatography using a Nucleosil C18 (150mm × 4.6mm, 3µm) column and with a mobile phase containing acetonitrile and 0.1% trifluoroacetic acid aqueous solution (25/75, V/V) at 1.0mLmin-1.and at a wavelength of 555nm. The method was validated using methodology described by the International Conference on Harmonization and was shown to be specific, precise (RSD < 11%), accurate and linear in the range of 0.1 - 30.0µM with a lower limit of quantification (LLOQ) of 0.1µM. This method was in a first time applied to AuNP quality control after their synthesis. In a second time, the absence of gold leakage (either as AuNP or gold salt form) from nanostructured multilayered polyelectrolyte films under shear stress was assessed.

Characterization and stability of gold nanoparticles depending on their surface chemistry: Contribution of capillary zone electrophoresis to a quality control.

Four kinds of gold nanoparticles (AuNP) quite similar in terms of gold core size (ca. 5nm) and shape (spherical) but differing by their surface chemistry (either negatively, or positively charged, or neutral) were synthesized. They were analyzed using both the classical physicochemical approach (spectrophotometry, dynamic light scattering coupled or not to electrophoresis and transmission electron microscopy) and capillary zone electrophoresis equipped with photodiode array detection. The results obtained by both methodologies (related to Surface Plasmon Band-maximal absorbance wavelength-, and zeta potential and electrophoretic mobilities) were well correlated. Moreover, taking advantage of the separation method, the sample heterogeneity was evaluated and an impurity profile was extracted. This allowed setting some specifications which were then applied on the one hand to a batch-to-batch survey to declare NP as conform or not after production and on the other hand to a stability study.