Surface enhanced Raman spectroscopy of thiacyanine dye J-aggregates on single silver nanoaggregates

Dye-coated colloidal metal nanoparticles (NPs) exhibit interesting optical properties originating from the interaction between metal core and dye shell. Depending on the interaction mechanism between the two, optical properties of dyes or NPs can be changed separately or jointly within the dye-NP assembly [1]. Many of the recent studies are focused on dyes which are able to self-assemble in highly oriented structures called Jaggregates on the surface of metallic NPs [2,3]. Owing to the variety of mechanisms by which dyes and their J-aggregates can interact with metallic NPs, dye-NP assemblies can lead to applications ranging from nanoscale sensing [4] to advanced composite materials for novel active and nonlinear optical devices [5]. Here we study the influence of TC concentration on its J-aggregation on the surface of AgNPs assemblies using Raman mapping and atomic force microscopy (AFM). Aqueous solutions (colloids) of citrate stabilized AgNPs with an average diameter of ~10 nm are mixed with TC dye solution and then deposited onto freshly cleaved highly oriented pyrolytic graphite and mica surfaces. The spectral signature of citrate ions is identified by (i) the O-H band around 220 cm-1, (ii) the C-H band around 2950 cm-1 and (iii) pronounced blinking in the 1000-1800 cm-1 range. In contrast, dye molecules adsorbed on nanoparticles are recognized by several stable Raman bands between 200 and 1600 cm-1. In situ AFM measurements show that SERS 'hot spots' are formed either on large single nanoparticles (diameter > 100 nm) or within assemblies of small nanoparticles (with diameters in the 10 - 50 nm range). However, only the latter are found to yield a citrate or TC dye SERS signal. We find that the TC dye adsorbed on the surface of AgNP nanoassemblies always forms J-aggregates when the dye concentration in the TC-AgNP solution is varied between 0.5μM and 17μM. Even though, a clear SERS spectra of dye Jaggregates can be acquired for high dye concentration (17μM) the citrate ions always exist on the AgNP surface and so does their SERS signature in form of O-H (220 cm-1) and C-H (2960 cm-1) bands. Assemblies with low TC concentration (0.5μM) do not have a clear dye SERS spectra, but rather spectra similar to the one of citrate ions meaning that either not all AgNPs are dye coated, or rather that the amount of TC molecules adsorbed on the surface of the nanoparticle is small and hence not detectable. We are grateful to the Serbian Ministry of Education, Science and Technological Development for financial support through projects Nos. OI 171005, OI 172023. This work was performed in the context of the European COST Action MP1302 Nanospectroscopy.V International School and Conference on Photonics and COST actions: MP1204, BM1205 and MP1205 and the Second international workshop "Control of light and matter waves propagation and localization in photonic lattices" : PHOTONICA2015 : book of abstracts; August 24-28, 2015; Belgrad

Preparation of silver and copper nanoparticles in presence of ascorbic acid and investigation of their antibacterial activity

In this study, we present a synthesis of silver and copper nanoparticles (NPs) using ascorbic acid as stabilizing and sodium borohydride as reducing agents, respectively. Four colloidal dispersions were obtained, two of them additionally stabilized by gelatin. They were characterized by UV-Vis, AFM, DLS and zeta potential measurements. The size of both silver and copper NPs, determined by AFM measurements, was 10 nm before, and 15 nm after stabilization with gelatin. Antibacterial activity of synthesized NPs was tested using series of gram positive and gram negative bacteria. It was found that Ag and Cu NPs showed antibacterial activity in all case s

Chiral Devices for Terahertz Waves Based on Tunable Metamaterials

There are exceptional advantages in the region where Terahertz (THz) frequency takes place that could be identified as; a non-ionizing bio-innocuous property, transparent characteristics in cardboard or textiles, and extremely discriminating absorption spectral lines which can provide a “genetic code” of various bio-materials. [1,2]. The resonant effects at various terahertz frequencies that were displayed by metamaterials have created to accomplish a very important situation. Metamaterials are virtually desirable platforms for investigating chiral effects. In order to enhance these effects, producing the tunable chiral devices attracted lots of attention. Among the phase change materials for chiral metamaterials, graphene is a promising candidate due to its astonishing properties specifically in the THz and far infrared region. In this study, a chiral metamaterial gammadion structure is designed and fabricated on both sides of the sapphire substrates. A commercial COMSOL and CST Microwave Studio programs are used to design and optimize the chiral metamaterial. Numerical simulations are based on the interaction of the chiral structure with linearly and circularly polarized light. In the experimental side, a resistive evaporation and dc magnetron sputtering method is used for the deposition of gold and Sb2Se3 films respectively. A single layer graphene is used, that is grown on a copper foil by chemical vapor deposition. The thin graphene layer transferred on the Sb2Se3 coated sapphire substrates. The conventional UV lithography and ion beam etching techniques are used for patterning process. The THz characterization measurements were performed in order to assess the THz frequency response and to demonstrate the dynamically tunable chiroptical response using optical pumping [3,4]. The active polarization manipulation capability of the Sb2Se3/graphene chiral metamaterial with frequency tunability are investigated both numerically and experimentally.XVI Photonics Workshop : Book of abstracts; March 12-15, 2023; Kopaonik, Serbi

Low-friction, wear-resistant, and electrically homogeneous multilayer graphene grown by chemical vapor deposition on molybdenum

Chemical vapour deposition (CVD) is a promising method for producing large-scale graphene (Gr). Nevertheless, microscopic inhomogeneity of Gr grown on traditional metal substrates such as copper or nickel results in a spatial variation of Gr properties due to long wrinkles formed when the metal substrate shrinks during the cooling part of the production cycle. Recently, molybdenum (Mo) has emerged as an alternative substrate for CVD growth of Gr, mainly due to a better matching of the thermal expansion coefficient of the substrate and Gr. We investigate the quality of multilayer Gr grown on Mo and the relation between Gr morphology and nanoscale mechanical and electrical properties, and spatial homogeneity of these parameters. With atomic force microscopy (AFM) based scratching, Kelvin probe force microscopy, and conductive AFM, we measure friction and wear, surface potential, and local conductivity, respectively. We find that Gr grown on Mo is free of large wrinkles that are common with growth on other metals, although it contains a dense network of small wrinkles. We demonstrate that as a result of this unique and favorable morphology, the Gr studied here has low friction, high wear resistance, and excellent homogeneity of electrical surface potential and conductivity.This is peer-reviewed version of the artcle: B. Vasić, U. Ralević, K.C. Zobenica, M.M. Smiljanić, R. Gajić, M. Spasenović, S. Vollebregt, Low-friction, wear-resistant, and electrically homogeneous multilayer graphene grown by chemical vapor deposition on molybdenum, Appl. Surf. Sci. (2019) 144792. [https://doi.org/10.1016/j.apsusc.2019.144792]Published version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3347

Uređenje, korišćenje i zaštita poljoprivrednog zemljišta opštine UB

The Ub municipality is located in the north-east end of the Podrinjsko-Kolubarski region. The total area of the Ub municipality is 45670 ha or 456.7 km2. The agricultural area takes 35471.55 ha or, approximately, 77.67% of the municipality’s territory. Cultivable agricultural land takes 32955.18 ha, or 71.16%, which is distinguished by relatively large amounts of arable areas, where fields and gardens take 29470.05 ha, or 89.42% of the cultivable areas, which is an indicator that the most common activity in the Ub municipality is grain cultivation (corn and wheat). Fruit-gardens and wineyards take an area of 1953.55 ha, or 4.65%. Meadows are on an area of 5.93%. Soils of the Ub municipality, according to existing data, are distinguished by unfavorable physical and mechanical characteristics, with needs for repairs by means of different types of soil reclamation techniques. Analysis of the usable structure of the agricultural lands shows that the estates are small, and the average area of a demesne is 3.4 ha per household. The average parcel size is 0.40 ha per each cultivated crop. There are no commasative areas and no arranged irrigation and drainage systems, according to data gathered by the Regional Unit of Ub, inclusive 31st of April, 2007. Possible positive results of arrangement, exploitation and protections of the agricultural land of the Ub municipality are many, of which the most important are: Switching from a traditional extensive agricultural production to an intense agricultural production; Increase of the number of registered and educated agriculturists, organizing of the business connecting of family households; agricultural products in compliance with high quality and safety standards; a skilled and developed consultative and informative agricultural service, which monitors agriculturist’s work; intensified sustainable development of the rural regions with the development of organic production; a reduced negative trend of the country-side to city migration; a created consciousness about the need for the protection of the environment from harmful effects of the agricultural production.Opština Ub se nalazi na severoistočnim delu Podrinjsko - Kolubarskog regiona. Ukupna površina opštine Ub je 45670 ha ili 456,7 km2. Poljoprivredne površine zauzimaju 35.471,55 ha ili, približno 77,67% teritorije opštine. Obradivog poljoprivrednog zemljišta ima 32955,18 ha ili 72,16%, koje se odlikuje relativno visokom zastupljenošću oraničnih površina, gde njive i vrtovi zauzimaju 29470,05 ha ili 89,42% obradivih površina, što ukazuje da je najzastupljenija delatnost u opštini Ub, ipak gajenje žitarica (kukuruz, pšenica). Voćnjaci i vinogradi su na površini od 1953,55 ha ili 4,65%. Livade se nalaze na površini 5,93%. Zemljišta opštine Ub prema postojećim podacima, odlikuju nepovoljne fizičko-mehaničke osobine, sa velikim potrebama za popravku sa primenom različitih pedo-meliorativnih mera. Analiza upotrebne strukture poljoprivrednog zemljišta daje karakteristike da su zemljišni posedi malih površina, gde je prosečna veličina poseda 3,4 ha po domaćinstvu. Prosečna veličina parcele je 0,40 ha po gajenoj poljoprivrednoj kulturi. Nema komasacionih površina, kao ni uređenih sistema za navodnjavanje i odvodnjavanje, prema podacima Područne jedinice Ub, zaključno sa 31. aprilom. 2007. godine. Mogući pozitivni rezultati uređenja, korišćenja i zaštite poljoprivrednog zemljišta Opštine Ub su mnogobrojni, od kojih su najvažniji: Prelazak sa tradicionalne ekstenzivne poljoprivredne proizvodnje, na intenzivnu poljoprivrednu proizvodnju; povećanje broja registrovanih i edukovanih poljoprivrednika, organizovanje odgovarajućih načina poslovnog povezivanja porodičnih gazdinstava; poljoprivredni proizvodi u skladu sa visokim standardima kvaliteta i bezbednosti; stručna i razvijena savetodavna i informaciona poljoprivredna služba koja prati rad poljoprivrednika; intenziviran održivi razvoj sela sa razvojem organske poljoprivredne proizvodnje; usporen negativni trend migracije selo - grad; i stvorena svest o potrebi zaštite životne sredine od štetnih efekata poljoprivredne proizvodnje

Nanoskopija i primene dvodimenzionalnih i kvazi dvodimenzionalnih sistema

This thesis addresses some of the fundamental and technological aspects of two- or quasi-two-dimensional systems realised within novel materials or metallic nanoparticle clusters. In particular, charge density modulations of the quasi-two-dimensional electron system in CeTe3, the two-dimensional electron system in graphene, twodimensional excitons in MoS2, and surface plasmons in metallic nanoparticle clusters were probed by a number of scanning probe microscopy and optical spectroscopy techniques. The optical properties, spectroscopic data and some potential applications of two-dimensional systems were investigated by numerically solving the macroscopic Maxwell equations by the nite element or re ection pole methods. The charge density waves in CeTe3 were investigated at room temperature by scanning tunneling microscopy, scanning tunneling spectroscopy and Raman spectroscopy. The modulation wavevector and the induced energy gap, which are crucial for describing these excitations, were assessed. The mixing of the modulation's wavevector with the wavevectors of the underlaying lattice was also observed. The charge density modulation was found to be followed by periodic rearrangement of tellurium atoms in planar layers hosting the modulation. The in uence of the environment on the two-dimensional charge carriers in graphene was investigated by Kelvin probe force microcopy and electrostatic force microscopy. This study was done for bare and isolated electrically gated graphene samples in which the concentration of charge carriers can be tuned via the electric eld eect. The results of this study, based on the analysis of the measured contact potential dierence, showed that the environment induces instabilities in doping levels of graphene even upon application of the gate voltage. The stability of gateinduced changes of the doping level in graphene is crucial for graphene based devices. Therefore this result indicates that improved performance of graphene based devices can be expected if graphene is isolated from the environment. Interaction between graphene and guided modes of optical waveguides was studied by means of exact numerical simulations and a convenient perturbation theory. The conclusion reached in this study is that graphene modies the modal propagation constants and that this eect can be used in construction of graphene based optical modulators. Investigation of the in uence of metallic nanoparticle clusters on two- dimensional excitons in MoS2 has showed that these nanoobjects do not alter the spectral position or width of the exciton photoluminescence but rather induce a small enhancement of the A excitonic peak. The reason for the weak interaction was found in the misalignment of the MoS2 plane and the dominant cluster's electric eld component, as well as in the fact that the electric elds are weak near the MoS2 plane. The electric elds were found to be the strongest within nano-gaps between the adjacent nanoparticles. This was utilized for the surface enhanced Raman spectroscopy study of the adsorption of thin aggregated dye layers on the cluster surface...U ovoj tezi razmatrani su neki od fundamentalnih i tehnoloskih aspekata dvodimenzionalnih ili kvazi dvodimenzionalnih sistema, koji su realizovani u novim materijalima ili klasterima metalnih nanocestica. Tehnikama skenirajuce mikroskopije i opticke spektroskopije proucavani su modulacija gustine naelektrisanja u kvazi dvodimenzionalnom elektronskom sistemu u CeTe3, dvodimenzionalni elektronski sistem u grafenu, dvodimenzionalni ekscitoni u MoS2 i povrsinski plazmoni u klasterima metalnih nanocestica. Opticke osobine, spektroskopski podaci i potencijalne primene dvodimenzionalnih sistema proucavani su numerickim resavanjem makroskopskih Maksvelovih jednacina pomocu metoda re eksije polova i konacnih elemenata. Pomocu skenirajuce mikroskopije, skenirajuce spektroskopije i Ramanove spektroskopije proucavan je talas gustine naelektrisanja u CeTe3 na sobnoj temperaturi. Kao rezultat ove studije odredeni su talasni vektor modulacije elektronske gustine stanja i energetski procep kojima se talas gustine naelektrisanja moze opisati. Uocena je i pojava mesanja talasnog vektora modulacije sa talasnim vektorima atomske resetke u ravni u kojoj se formira talas gustine naelektrisanja. Utvrdeno je da modulacija elektronske gustine stanja postoji zajedno sa periodicnom modulacijom atomske resetke telurovih atoma u kojima se talas gustine naelektrisanja formira. Uticaj faktora iz spoljasnje sredine na dvodimenzionalne nosioce naelektrisanja u grafenu proucavan je pomocu skenirajuce Kelvinove mikroskopije i mikroskopije elektrostatickih sila. Ova studija je realizovana u slucajevima kada je grafen izlozen odnosno izolovan od uticaja iz okolne sredine. Proucavani su uzorci pripremljeni u takozvanoj gejt konguraciji koja omogucava promenu koncentarcije nosilaca u grafenu primenom napona gejta. Na osnovu analize izmerene kontaktne potencijalne razlike nadeno je da faktori iz spoljasnje sredine dovode do nestabilnosti koncentracije elektrona u grafenu, cak i kada je napon gejta primenjen. Posto je stabilnost nivoa dopiranja neophodna za rad naprava na bazi grafena, ova studija pokazuje da se bolje performanse mogu ocekivati kada je grafen izolovan od uticaja iz spoljasnje sredine. Razmatrana je i interakcija grafena sa vodenim modovima optickih talasovoda. Za analizu ovog problema upotrebljeni su razliciti numericki alati. Zakljuceno je da grafen dovodi do modikacije propagacione konstante vodenih modova i da se ova pojava moze iskoristiti u konstrukciji optickih modulatora. Ispitivanjem uticaja klastera metalnih nanocestica na fotoluminescenciju ekscitona u MoS2 nadeno je da metalni nanosistemi ne uticu na poziciju i spektralnu sirinu fotoluminescencije, ali da ipak dovode do slabog pojacanja ekscitonskog A pika. Razlozi su slabo sprezanje elektricnog polja metalnih klastera i MoS2 kao i slab intenzitet ovih polja u blizini MoS2. Cinjenica da je elektricno polje u okviru metalnih klastera jako u supljinama izmedu nanocestica iskoriscena je za proucavanje mehanizma adsorpcije tankih slojeva organske boje na povrsinu klastera, pomocu povrsinom podstaknute Ramanove spektroskopije..

Nanoskopija i primene dvodimenzionalnih i kvazi dvodimenzionalnih sistema

This thesis addresses some of the fundamental and technological aspects of two- or quasi-two-dimensional systems realised within novel materials or metallic nanoparticle clusters. In particular, charge density modulations of the quasi-two-dimensional electron system in CeTe3, the two-dimensional electron system in graphene, twodimensional excitons in MoS2, and surface plasmons in metallic nanoparticle clusters were probed by a number of scanning probe microscopy and optical spectroscopy techniques. The optical properties, spectroscopic data and some potential applications of two-dimensional systems were investigated by numerically solving the macroscopic Maxwell equations by the nite element or re ection pole methods. The charge density waves in CeTe3 were investigated at room temperature by scanning tunneling microscopy, scanning tunneling spectroscopy and Raman spectroscopy. The modulation wavevector and the induced energy gap, which are crucial for describing these excitations, were assessed. The mixing of the modulation's wavevector with the wavevectors of the underlaying lattice was also observed. The charge density modulation was found to be followed by periodic rearrangement of tellurium atoms in planar layers hosting the modulation. The in uence of the environment on the two-dimensional charge carriers in graphene was investigated by Kelvin probe force microcopy and electrostatic force microscopy. This study was done for bare and isolated electrically gated graphene samples in which the concentration of charge carriers can be tuned via the electric eld eect. The results of this study, based on the analysis of the measured contact potential dierence, showed that the environment induces instabilities in doping levels of graphene even upon application of the gate voltage. The stability of gateinduced changes of the doping level in graphene is crucial for graphene based devices. Therefore this result indicates that improved performance of graphene based devices can be expected if graphene is isolated from the environment. Interaction between graphene and guided modes of optical waveguides was studied by means of exact numerical simulations and a convenient perturbation theory. The conclusion reached in this study is that graphene modies the modal propagation constants and that this eect can be used in construction of graphene based optical modulators. Investigation of the in uence of metallic nanoparticle clusters on two- dimensional excitons in MoS2 has showed that these nanoobjects do not alter the spectral position or width of the exciton photoluminescence but rather induce a small enhancement of the A excitonic peak. The reason for the weak interaction was found in the misalignment of the MoS2 plane and the dominant cluster's electric eld component, as well as in the fact that the electric elds are weak near the MoS2 plane. The electric elds were found to be the strongest within nano-gaps between the adjacent nanoparticles. This was utilized for the surface enhanced Raman spectroscopy study of the adsorption of thin aggregated dye layers on the cluster surface...U ovoj tezi razmatrani su neki od fundamentalnih i tehnoloskih aspekata dvodimenzionalnih ili kvazi dvodimenzionalnih sistema, koji su realizovani u novim materijalima ili klasterima metalnih nanocestica. Tehnikama skenirajuce mikroskopije i opticke spektroskopije proucavani su modulacija gustine naelektrisanja u kvazi dvodimenzionalnom elektronskom sistemu u CeTe3, dvodimenzionalni elektronski sistem u grafenu, dvodimenzionalni ekscitoni u MoS2 i povrsinski plazmoni u klasterima metalnih nanocestica. Opticke osobine, spektroskopski podaci i potencijalne primene dvodimenzionalnih sistema proucavani su numerickim resavanjem makroskopskih Maksvelovih jednacina pomocu metoda re eksije polova i konacnih elemenata. Pomocu skenirajuce mikroskopije, skenirajuce spektroskopije i Ramanove spektroskopije proucavan je talas gustine naelektrisanja u CeTe3 na sobnoj temperaturi. Kao rezultat ove studije odredeni su talasni vektor modulacije elektronske gustine stanja i energetski procep kojima se talas gustine naelektrisanja moze opisati. Uocena je i pojava mesanja talasnog vektora modulacije sa talasnim vektorima atomske resetke u ravni u kojoj se formira talas gustine naelektrisanja. Utvrdeno je da modulacija elektronske gustine stanja postoji zajedno sa periodicnom modulacijom atomske resetke telurovih atoma u kojima se talas gustine naelektrisanja formira. Uticaj faktora iz spoljasnje sredine na dvodimenzionalne nosioce naelektrisanja u grafenu proucavan je pomocu skenirajuce Kelvinove mikroskopije i mikroskopije elektrostatickih sila. Ova studija je realizovana u slucajevima kada je grafen izlozen odnosno izolovan od uticaja iz okolne sredine. Proucavani su uzorci pripremljeni u takozvanoj gejt konguraciji koja omogucava promenu koncentarcije nosilaca u grafenu primenom napona gejta. Na osnovu analize izmerene kontaktne potencijalne razlike nadeno je da faktori iz spoljasnje sredine dovode do nestabilnosti koncentracije elektrona u grafenu, cak i kada je napon gejta primenjen. Posto je stabilnost nivoa dopiranja neophodna za rad naprava na bazi grafena, ova studija pokazuje da se bolje performanse mogu ocekivati kada je grafen izolovan od uticaja iz spoljasnje sredine. Razmatrana je i interakcija grafena sa vodenim modovima optickih talasovoda. Za analizu ovog problema upotrebljeni su razliciti numericki alati. Zakljuceno je da grafen dovodi do modikacije propagacione konstante vodenih modova i da se ova pojava moze iskoristiti u konstrukciji optickih modulatora. Ispitivanjem uticaja klastera metalnih nanocestica na fotoluminescenciju ekscitona u MoS2 nadeno je da metalni nanosistemi ne uticu na poziciju i spektralnu sirinu fotoluminescencije, ali da ipak dovode do slabog pojacanja ekscitonskog A pika. Razlozi su slabo sprezanje elektricnog polja metalnih klastera i MoS2 kao i slab intenzitet ovih polja u blizini MoS2. Cinjenica da je elektricno polje u okviru metalnih klastera jako u supljinama izmedu nanocestica iskoriscena je za proucavanje mehanizma adsorpcije tankih slojeva organske boje na povrsinu klastera, pomocu povrsinom podstaknute Ramanove spektroskopije..

Dependence of loss parameters on circularly polarized terahertz wave propagation through graphene gated metamaterial

Polarization is an important characteristic of electromagnetic waves and manipulation of polarization plays pivotal role in different areas such as communications, imaging and sensing. On the other hand, the ability to dynamically modify the state of polarization with metamaterials enables control of circular dichroism and optical activity in terahertz frequency range [1,2]. This dynamic control can be realized by incorporating graphene layer into the metasurface, whose conductivity can be controlled by applying gate voltage. In this work, the effect of graphene conductivity on chiral effects of the metasurface will be analyzed using temporal coupled-mode theory [3,4]. In this frame, each resonant mode is characterized with its resonant frequency, radiative and non-radiative coupling coefficients. These parameters will be retrieved from simulated reflection and transmission spectra for left and right circular polarizations. In such way, theoretical model for tunable chiral effects in graphene metasurface will be given, enabling further improvement of its properties.VIII International School and Conference on Photonics and HEMMAGINERO workshop : PHOTONICA2021 : book of abstracts; August 23-27, 2021; Belgrad

Active terahertz metamaterial for polarization manipulation and biosensing

Controlling states of circular polarization with metamaterials [1] enables diverse applications in information processing, spectroscopy and communications. Furthermore, strong modulation of polarization of terahertz (THz) electromagnetic waves can be achieved by integrating active material (such as graphene) with metamaterials [2,3]. The chiral effects can be tuned and metamaterial sensing capabilities can be improved by dynamical modulation of the graphene conductivity. Nowadays, there is a need for rapid and reliable detection of biological samples, especially viruses. The advantage of active metamaterials is precise distinction in between viruses, which is challenging due to their nearly comparable refractive indices. This makes them appropriate for biosensor applications [4,5]. In this work, we numerically investigate THz electromagnetic wave propagation through metamaterial composed of resonant elements based on metallic strips embedded with gated graphene layer. The analysis is provided by calculation of cross- and co-reflection coefficients and efficiency of linear to circular polarization conversion with the change of the Fermi energy of graphene. In addition, the sensitivity of reflection spectra is tested for variations of refractive index, using the data available in the literature for several types of viruses, which is indicative for performance of the proposed metamaterial as a potential biosensor. We expect that proposed structure will enable easier biosensor fabrication with enhanced detection sensitivity compared to previously numerically investigated structures.VIII International School and Conference on Photonics and HEMMAGINERO workshop : PHOTONICA2021 : book of abstracts; August 23-27, 2021; Belgrad

A Single-Cell Raman Spectroscopy Analysis of Bone Marrow Mesenchymal Stem/Stromal Cells to Identify Inter-Individual Diversity

The heterogeneity of stem cells represents the main challenge in regenerative medicine development. This issue is particularly pronounced when it comes to the use of primary mesenchymal stem/stromal cells (MSCs) due to a lack of identification markers. Considering the need for additional approaches in MSCs characterization, we applied Raman spectroscopy to investigate inter-individual differences between bone marrow MSCs (BM-MSCs). Based on standard biological tests, BM-MSCs of analyzed donors fulfill all conditions for their characterization, while no donor-related specifics were observed in terms of BM-MSCs morphology, phenotype, multilineage differentiation potential, colony-forming capacity, expression of pluripotency-associated markers or proliferative capacity. However, examination of BM-MSCs at a single-cell level by Raman spectroscopy revealed that despite similar biochemical background, fine differences in the Raman spectra of BM-MSCs of each donor can be detected. After extensive principal component analysis (PCA) of Raman spectra, our study revealed the possibility of this method to diversify BM-MSCs populations, whereby the grouping of cell populations was most prominent when cell populations were analyzed in pairs. These results indicate that Raman spectroscopy, as a label-free assay, could have a huge potential in understanding stem cell heterogeneity and sorting cell populations with a similar biochemical background that can be significant for the development of personalized therapy approaches