Journal of Physical Chemistry C publishes study from Laboratory of Research in Nanosciences and their Spanish and Russian colleagues on new platform for optical monitoring of medium's pH

The study pH-Sensing Platform Based on Light−Matter Coupling in Colloidal Complexes of Silver Nanoplates and J-Aggregates by Victor Krivenkov, Pavel Samokhvalov, Igor Nabiev, and Yury P. Rakovich presents the results of the development of a new method for monitoring the pH by using the effect of strong light–matter coupling in plasmon–exciton nanohybrid systems.

The authors have designed colloidal complexes of silver nanoplates coated with a shell of J-aggregates of the cyanine dye JC-1 (commercial name). Upon the exposure to external electromagnetic radiation, provided that resonance conditions are met, longitudinal oscillations of electron density (localized plasmons) are formed in silver nanoplates, which allows the electromagnetic field energy to be concentrated within the plasmon mode volume (approximately equal to the volume of the nanoplatelet itself). This ultra-high concentration of photon density states allows the light–matter coupling effect to occur, with optical transitions in molecules located within the plasmon mode volume. J-aggregates of cyanine dyes are characterized by a unique optical band (the so-called J-band), which corresponds to the formation of the excitonic state, and the corresponding excitonic transition has a very large dipole moment. The use of J-aggregates of the JC-1 cyanine dye with a uniquely high excitonic transition dipole moment allowed the researchers to obtain the regime of a strong light-matter coupling (between the plasmon mode and the excitonic transition). In the optical spectrum of the resultant complexes, both the Rabi splitting effect related to the formation of hybrid polariton bands in the extinction spectrum of the complexes and the effect of induced transparency representing a spectral dip in the region of the maximum of the plasmon mode spectrum were observed. The researchers have found that a change in the pH of the medium in which the complexes are located is accompanied by a dramatic change in the strength of the light–matter coupling effect on the extinction spectrum of the complexes. They attribute this effect to a change in the dipole moment of the excitonic transition due to a change in the structure of the J-aggregates when the pH changes. This characteristic behavior makes it possible to monitor the changes in the pH in a very wide range, from 11 to 2, which significantly exceeds the ranges covered by all other optical methods. These results can be used in various technological and economic applications, including agriculture and the fields of biomedicine, biochemistry, and environment monitoring.

Article: https://pubs.rsc.org/en/content/articlelanding/2021/NR/D0NR08893E#!divAbstract

Contact : Prof. Igor Nabiev, http://igor.nabiev@univ-reims.fr

The highly rated Nanoscale journal publishes study from Laboratory of Research in Nanosciences

A study performed by LRN-EA4682 together with collaborating foreign (Russian and Spanish) research centers has appeared in the Nanoscale, a prestigious international journal jointly published by the Royal Society of Chemistry (RSC) and the National Center for Nanoscience and Technology (NCNST) of China. The study Strong Increase in the Effective Two-Photon Absorption Cross-Section of Excitons in Quantum Dots Due to the Nonlinear Interaction with Localized Plasmons in Gold Nanorods by Victor Krivenkov, Pavel Samokhvalov, Ana Sánchez-Iglesias, Marek Grzelczak, Igor Nabiev,and Yury Rakovich describes the effect, discovered by the authors, of a substantial increase in quantum dots' capacity for two-photon absorption as a result of nonlinear resonance energy transfer from gold plasmonic nanoparticles.

The authors have developed a thin-film hybrid material composed of semiconductor quantum dots absorbing and emitting light in the visible wavelength range and gold plasmonic nanoparticles absorbing infrared radiation. The researchers have found that the two-photon absorption capacity of quantum dots in a nonlinear mode increases more than 12-fold in this material. Two-photon absorption essentially represents an optical transition upon simultaneous absorption of two photons, the energy of this transition being equal to the sum of energies of the two photons. In the case of quantum dots, two-photon absorption leads to energy energy upconversion; i.e., obtaining one high-energy photon of visible light from two infrared photons with low energy. The authors explain the observed increase in the probability of two-photon absorption in quantum dots located near gold plasmonic nanoparticles by nonlinear near-field dipole–dipole energy transfer. This has become possible because the gold plasmonic nanoparticles used can effectively interact with the exciting infrared radiation and concentrate its energy near its surface due to the localized resonant plasmon oscillations. As a result, the energy density of the electromagnetic field of the plasmonic mode is sufficient for effective simultaneous energy transfer from two quanta of the plasmonic mode to the exciton state in the quantum dot. The results of this study make it possible to significantly increase the efficiency of the use of quantum dots for upconversion of electromagnetic field energy, which can be widely used for high-contrast bioimaging and designing of nonlinear-optical photodetectors.

Article: https://pubs.rsc.org/en/content/articlelanding/2021/NR/D0NR08893E#!divAbstract

Contact : Prof. Igor Nabiev, http://igor.nabiev@univ-reims.fr

05.06.2020

Laboratory of Research in Nanosciences develops new molecular biology methods

The methods described in these chapters are related with the results of ongoing research and developments in the field of micro- and nanosystems for disease diagnosis and treatment using semiconductor nanocrystals (quantum dots). Their unique optical properties allow quantum dots to be used as labels in diagnostic probes, theranostic systems, and microarrays in order to make analyses more sensitive and "multiplexed" (with many biomarkers detected in a single biological sample).

The chapter "Stimulus-sensitive theranostic delivery systems based on microcapsules encoded with quantum dots and magnetic nanoparticles" (G. Nifontova, F. Ramos-Gomes, F. Alves, I. Nabiev, A. Sukhanova) describes a method for manufacturing optical–magnetic microcapsules, with both fluorescent quantum dots and magnetic particles integrated in the shell (Scheme 1). These microcapsules are sensitive to external stimuli (optical radiation and magnetic field) and can serve as a platform for designing theranostic systems with controlled drug release, as well as contrast agents detected be fluorescent microscopy and magnetic resonance methods, which make them promising components of diagnostic and therapeutic applications.

The chapter "Multiplexed detection of cancer serum antigens with a quantum dot-based lab-on-bead system" (T. Tsoy, A. Karaulov, I. Nabiev, A. Sukhanova) deals with the development of a suspension test system for the detection of circulating biomarkers in blood samples (Scheme 2). In this method, quantum dots with different optical properties are incorporated into the shell of microbeads, and antibodies recognizing the target biomarker of a specific disease (e.g., cancer) are attached to the microbead surface. The biomarker bound by the antibodies is imaged using an organic dye. This "lab-on-bead" provides high-precision quantitative detection of several cancer markers at a time using flow cytometry. Experiments have shown distinct advantage of the new diagnostic system over enzyme-linked immunosorbent assays routinely used in clinical laboratories.

The chapter "Comparative advantages and limitations of quantum dots in protein array applications" (N. Ayadi, F. Lafont, C. Charlier, H. Benhelli-Mokrani, P. Sokolov, A. Sukhanova, F. Fleury, I. Nabiev) describes the use of quantum dots as fluorescent labels in biochips intended for multiplexed analysis. In these biochips, quantum dots are conjugated with secondary antibodies recognizing the analyte that has been preliminarily bound by the primary antibody attached to the biochip surface (Scheme 3). The effectiveness of the test system has been demonstrated in experiments on (A) detecting DNA-protein kinases in cells and (B) estimating the level of protein phosphorylation caused by DNA damage.

The Methods in Molecular Biology book series has been published as part of Springer Protocols since 1983. The books of these series represent collections of new research methods and protocols in molecular biology and related areas described by the authors of the methods in detail sufficient for readers to reproduce the techniques in their labs.

17.02.2020

Top-rated ACS Photonics publishes paper from Laboratory of Research in Nanosciences: New method to measure fluorescent nanocrystals' two-photon absorption efficiency

The prestigious international journal ACS Photonics has published a study on the efficiency of two-photon light absorption by samples of fluorescent semiconductor nanocrystals with unknown concentrations, which is a challenging issue in a number of their practical applications (Victor Krivenkov, Pavel Samokhvalov, Darya Dyagileva, Igor Nabiev, Alexander Karaulov. Determination of the single-exciton two-photon absorption cross-sections of semiconductor nanocrystals through the measurement of saturation of their two-photon-excited photoluminescence) performed by the collaboration of LRN-EA4682; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russia; and Sechenov First Moscow State Medical University, Russia.

Nanocrystal fluorescence induced by nonlinear absorption of two excitation photons at a time is increasingly widely used in imaging and detection of biological targets because it allows the excitation with infrared light instead of visible one. Nanocrystals are the best choice as fluorophores in these applications because they are capable of two-photon absorption varying for nanocrystals of different sizes, shapes, and compositions. The traditional methods of measuring the efficiency of two-photon absorption (two-photon absorption cross section) for emitting single-exciton states may be inaccurate in the case of large nanocrystals, as well as samples with unknown concentrations or low optical densities.

The authors solve this problem by analyzing the fluorescence signal saturation process with the use of their own theoretical model which takes into account incomplete relaxation of the fluorophores between laser pulses. Experiments have shown that the new method yields excellent results for samples with unknown concentrations of nanocrystals and samples with ultralow optical densities.

The results of the study extend the applications of fluorescent detection and imaging of biological objects with the use of two-photon excitation in the infrared spectral region and offer new possibilities in designing nonlinear optical photodetectors.

ACS Photonics is an interdisciplinary journal published by the American Chemical Society. The journal publishes empirical research and theoretical articles and reviews on various basic and applied aspects of photonics. ACS Photonics, first published as recently as 2014, soon became atop-rated journal. Since 2015, it has always been included in the first quartile of the SCImago journal ranking (SJR) in four categories: Atomic and Molecular Physics, and Optics; Biotechnology; Electrical and Electronic Engineering; and Electronic, Optical and Magnetic Materials.

25.01.2020

Laboratory of Research in Nanosciences comes up with a new approach to multiplexed detection of disease markers

The top-rated Scientific Reports journal has published a study on a new method for multiplexed detection performed by researchers from LRN-EA4682 and their foreign colleagues (Kage, D., Katrin Hoffmann, K., Nifontova, G., Krivenkov, V., Sukhanova, A., Nabiev, I., Resch-Genger, U. Tempo-spectral multiplexing in flow cytometry with lifetime detection using QD-encoded polymer beads. Scientific Reports, 10, 653).

Optically encoded polymer microbeads are promising tools for detecting molecular targets by means of flow cytometry, which are being intensely developed with a view to using them in molecular diagnoses of cancer and other diseases. The designing of such microbeads is an ongoing line of research at LRN and collaborating laboratories, where, e.g., an original method has been developed to obtain microcapsules with a multilayered shell in which layers of quantum dots of different colors and types are separated from one another by polyelectrolyte layers (https://doi.org/10.1002/cphc.201601274).

The approach used in the published paper is essentially new in that not only the wavelength, but also the fluorescence lifetime are used as optical codes. The recording of the fluorescence lifetime in the flow cytometry mode has become possible owing to a novel setup which measures both the fluorescence intensities at different wavelengths and the fluorescence lifetimes directly in the fluid flow.

Four types of microbeads were used in the study, two of them containing organic fluorophores and the other two ones containing quantum dots, which have a much longer fluorescence lifetime. The former microbeads served for color coding, and the latter, for fluorescence lifetime coding. The experiments have confirmed that the differences between quantum dots in fluorescence lifetime are distinctly detectable through recording their fluorescence decay kinetics using the new cytometric setup. Obviously, more types of microbeads containing each kind of fluorophores can be used in practical applications.

Thus, the use of fluorescence kinetic parameters as "another dimension in parameter space" has enhanced the potential of multiplexed fluorescence detection within one analysis of a single sample. This is important, in particular, for making the detection of disease markers quicker, more reliable, and less expensive and will undoubtedly increase the efficiency of medical diagnosis.

Scientific Reports is a top-rated international journal of the Nature group publishing only original studies and developments. The journal has permanently been in the first quartile of interdisciplinary journals in SCImago's Scientific Journal Ranking (SJR) almost since its foundation.

10.07.2019

Study from Laboratory of Research in Nanosciences on nanotoxicity issues published by Frontiers in Chemistry, top-rated international journal

The Frontiers in Chemistry has published a study performed by researchers from the Laboratory of Research in Nanosciences in collaboration with their colleagues from the National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Russia; University of Tübingen, Germany; and Sechenov First Moscow State Medical University, Russia (Sukhanova, A., Poly, S., Bozrova, S., Lambert, E., Ewald, E., Molinari, M., Karaulov, A.V., Nabiev, I. Nanoparticles with a specific size and surface charge promote disruption of the secondary structure and amyloid-like fibrillation of human insulin under physiological conditions. doi: 10.3389/fchem.2019.00480).

The study deals with nanotoxicity, a problem that has become urgent now that the prospect arises of using fluorescent nanocrystals (quantum dots) in medicine as components of diagnostic and therapeutic nanosystems. Nanotoxicity is one of the main problems precluding the introduction of nanoparticles into the body of a patient. Its solution would, in particular, take cancer diagnosis and treatment to a whole new level.

One of the causes of potential "molecular" toxicity of nanoparticles is their interaction with proteins leading to an altered conformation of the biological molecules. As a result, the function of the protein (e.g., and enzyme or a hormone) is disturbed, and, in addition, an autoimmune response occurs.

The authors of the published study analyzed how the nanoparticles' toxic effect depends on their size and surface charge under physiological conditions. They found that the toxicity depended much more on the nanoparticle size and charge than on their chemical composition. Moreover, it turned out that the degree of nanoparticle's toxicity could be controlled by varying their size and surface charge. This task has been solved by the authors. It has been demonstrated that technologies developed in LRN and collaborating organizations make it possible to either increase or almost entirely cancel the toxicity of nanoparticles of any chemical composition, irrespective of their structure.

Figure 1. The time course of the interaction between insulin and quantum dots imaged by atomic force microscopy.

The Frontiers in Chemistry publishes breakthrough studies in various fields of chemistry, biology, and medicine and at interfaces with other sciences. The journal was founded six years ago and has been included in the first quartile of journals on Chemistry in SJR.

14.05.2019

Study from Laboratory of Research in Nanosciences published in top-rated Materials Science and Engineering C

The international journal Materials Science and Engineering C has published a study on a medical application of nanomaterials performed at the Laboratory of Research in Nanosciences in collaboration with Brazilian and Russian research centers—de Menezes, F.D., dos Reis, S.R.R., Pinto, S.R., Portilho, F.L., do Vale Chaves e Mello, F., Helal-Neto, E., da Silva de Barros, A.O., Alencar, L.M.R., de Menezes, A.S., Santos, C.C., Saraiva-Souza, A., Perini, J.A., Machado, D.E., Felzenswalb, I., Araujo-Lima, C.F., Sukhanova, A., Nabiev, I., Santos-Oliveira, R. Graphene quantum dots unraveling: Green synthesis, characterization, radiolabeling with ^99mTc, in vivo behavior and mutagenicity. MaterialsScience and Engineering C, 2019, 102, 405–414.

The study deals with the use of graphene nanoparticles for diagnosis and treatment of diseases. Graphene-based nanolabels are considered promising innovative tools for medical diagnosis and in loco therapy; however, their behavior in the body and potential mutagenicity remain insufficiently understood.

The authors have developed a new green method for synthesizing graphene nanoparticles and a technique for their radioactive labeling. Experiments on mice have demonstrated that the distribution of these nanoparticles in living systems and their accumulation in different organs in healthy state and during inflammation can be traced. Tests on tissue cultures have shown that graphene nanoparticles labeled with radioactive isotopes are mutagenic.

The Elsevier journal Materials Science and Engineering C: Materials for Biological Applications publishes studies at the interface of biomedical sciences and materials engineering. According to the SCImago ranking, this prestigious international journal is in the first quartile in a number of subject categories: https://www.scimagojr.com/journalsearch.php?q=17813&tip=sid&clean=0