Nanomolar Concentration Level Research Articles

Gadolinium-Sensitive Artificial Nanochannel Membrane for Information Encryption.

Inspired from ion channels in the myelinated axon of Xenopus laevis found to be affected by gadolinium on axonal currents, we present a solid nanochannel membrane sensitive to gadolinium (Gd3+), which can be achieved via the use of the macrocyclic triacetic acid derivative in the host-guest chemistry approach. The macrocyclic nanochannel has good responsiveness toward Gd3+, even at the nanomolar concentration level, evidenced by discernible changes in rectification, ionic conductance, and XPS analyses. Notably, the Gd3+-sensitive nanochannel membrane can be switched by the addition of a diethylenetriaminepentaacetic acid (DTPA) derivative. Further studies have indicated that the gated behavior of Gd3+ in the nanochannel can be attributed to the strong binding strength between DO3A and Gd3+, which induces a surface charge reversal within the nanochannel. The mechanism has been confirmed through several experimental techniques, including isothermal titration calorimetry (ITC) experiments, fluorescence titration experiments, and finite element analysis. Based on its Gd3+ responsiveness of the constructed ion channel, we successfully developed an advanced multilevel information encryption application of the artificial solid nanochannel membrane. Furthermore, it is anticipated that a more effective encryption system will be built by utilizing the bionic ion channel system's ease of use and straightforward functionalization.

Click Chemistry Derived Hexa-ferrocenylated 1,3,5-Triphenylbenzene for the Detection of Divalent Transition Metal Cations.

The 1,3-dipolar cycloaddition reaction (click chemistry approach) was employed to create a hexa-ferrocenylated 1,3,5-triphenylbenzene derivative. Leveraging the presence of metal-chelating sites associated with 1,2,3-triazole moieties and 1,4-dinitrogen systems (ethylenediamine-like), as well as tridentate chelating sites (1,4,7-trinitrogen, diethylene triamine-like) systems, the application of this molecule as a chemosensor for divalent transition metal cations was investigated. The interactions were probed voltammetrically and spectrofluorimetrically against seven selected cations: iron(II) (Fe2+), cobalt(II) (Co2+), nickel(II) (Ni2+), copper(II) (Cu2+), zinc(II) (Zn2+), cadmium(II) (Cd2+), and manganese(II) (Mn2+). Electrochemical assays revealed good detection properties, with very low limits of detection (LOD), for Co2+, Cu2+, and Cd2+ in aqueous solution (0.03-0.09 μM). Emission spectroscopy experiments demonstrated that the title compound exhibited versatile detection properties in solution, specifically turn-off fluorescence behavior upon the addition of each tested transition metal cation. The systems were characterized by satisfactory Stern-Volmer constant values (105-106 M-1) and low LOD, especially for Zn2+ and Co2+ (at the nanomolar concentration level).

Photosubstitution and photoreduction of a diazido platinum(IV) anticancer complex.

The hyphenation of HPLC with its high separation ability and ICP-MS with its excellent sensitivity, allows the analysis of Pt drugs in biological samples at the low nanomolar concentration levels. On the other hand, LC-MS provides molecular structural confirmation for each species. Using a combination of these methods, we have investigated the speciation of the photoactive anticancer complex diazido Pt(IV) complex trans, trans, trans-[Pt(N3)2(OH)2(py)2] (FM-190) in aqueous solution and biofluids at single-digit nanomolar concentrations before and after irradiation. FM-190 displays high stability in human blood plasma in the dark at 37 °C. Interestingly, the polyhydroxido species [{PtIV(py)2(OH)4} + Na]+ and [{PtIV(py)2(N3)(OH)3} + Na]+ resulting from the replacement of azido ligands, as determined by LC-MS, were the major products after photoirradiation of FM-190 with blue light (463 nm). This finding suggests that such photosubstituted Pt(IV) tri- and tetra-hydroxido species could play important roles in the biological activity of this anticancer complex. Density Functional Theory (DFT) and Time-Dependent DFT (TDDFT) calculations show that these Pt(IV) species arising from FM-190 in aqueous media can be formed directly from a singlet excited state. The results highlight how speciation analysis (metallomics) can shed light on photoactivation pathways for FM-190 and formation of potential excited-state pharmacophores. The ability to detect and identify photoproducts at physiologically-relevant concentrations in cells and tissues will be important for preclinical development studies of this class of photoactivatable platinum drugs.

Sulfur Vacancies‐Triggered High SERS Activity of Molybdenum Disulfide for Ultrasensitive Detection of Trace Diclofenac

AbstractDue to the efficient photoinduced charge transfer properties of nonmetals, nonmetallic surface‐enhanced Raman scattering (SERS) substrates have been advanced rapidly these years. And among of these, molybdenum disulfide (MoS2) is perceived as one of the most representative nonmetallic SERS substrates due to its abundant active sites. However, its progress in SERS field is severely hindered because of the lower SERS activity. Herein, one type of vacancies‐triggered highly sensitive SERS substrate based on nanostructured MoS2 with sulfur vacancies (VS) is proposed. The VS‐MoS2 substrates are intended to promote the SERS performance through the VS density regulation. Intrinsically, moderate VS can change the bandgap structure of MoS2, thus promoting the separation of internal carriers and enhancing the interaction with target species. Externally, the presence of VS can bring abundant adsorption sites on MoS2 surface, which greatly improves its ability to enrich target molecules. Both internal and external properties make VS‐MoS2 a high SERS activity substrate. Moreover, with the antibiotic contaminant diclofenac as a model probe molecule, the VS‐MoS2 substrate can accurately perceive its nanomolar concentration level with an enhancement factor up to 5.85 × 103. This work demonstrates exciting potential for analysis in real water environments based on nonmetallic SERS applications.

SiN-Microring-Resonator-Based Optical Biosensor for Neuropeptide Y Detection

We report the design, fabrication, and characterization of a silicon-nitride (SiN) microring-resonator-based label-free biosensor for the purpose of neuropeptide Y (NPY) protein detection. NPY is commonly associated with stress in human body. The device uses evanescent field sensing, its geometry is optimized for 1550-nm signal, and it is fabricated by following standard CMOS processes. Top surface of the device is designed to function in aqueous environment and appropriately functionalized to ensure the biomaterial-specific attachment. The time-dependent spectral response to the biomaterial attachment is observed by scanning a tunable laser source around 1550 nm and measuring the resonance shift in the transmission spectrum. We experimentally achieve the detection into nanomolar concentration level in a regular assay system with 0.1 nm/( μg/mL) of sensitivity and ~ 30 mins of analysis time. This sensitivity is further amplified by a factor of three with a sandwiched assay technique, with which ~ 58 nM ( 0.25 μg/mL) concentration of NPY is successfully detected.

Core-shell magnetic Ag-molecularly imprinted composite for surface enhanced Raman scattering detection of carbaryl

Surface-enhanced Raman scattering (SERS) is a promising technique for rapid detection of pesticide residues. However, conventional SERS substrates require extraction processes which are time consuming and they also lack selectivity, stability and reproducibility. Herein, we present a multifunctional stable zero-valent iron based core-shell substrate. It combines magnetic separation, selective adsorption by molecular imprinting technique and sensitive detection of carbaryl by SERS. The core-shell substrate was successfully prepared by immobilizing silver on the surface of zero-valent iron microspheres. Subsequent molecular imprinting on the bimetallic magnetic silver microspheres ensured selective removal and detection. The substrate exhibited magnetization saturation of 8.89 emu/g providing efficient analyte separation. It showed high sensitivity and selectivity toward carbaryl detection to nanomolar concentration level. Linear regression models for peaks at Raman shift 1599 cm−1 and 2233 cm−1 demonstrated a good linear fit with R2=0.9738 and R2=0.8952 respectively. The composite was successfully applied on spiked water samples resulting in average recovery rate of 89%. The findings of this study demonstrate great substrate potential for application in separation and detection of trace quantities of chemical contaminants for environment safety and protection.

A long-wavelength turn-on fluorescent probe for intracellular nanomolar level peroxynitrite sensing with second-level response

As a typical kind of endogenous reactive nitrogen species, peroxynitrite (ONOO−) is believed heavily involved in the pathogenesis of many diseases such as inflammation, neurodegenerative conditions, and cardiovascular disorders. Precisely estimating ONOO− level in cell compartments is crucial for unraveling the biological relevance of ONOO− and enabling effective control of ONOO−-associated pathogenicity but suffers from serious difficulty owing to the daunting elusive features of ONOO−, namely nanomolar level physiological concentration and millisecond level biological half-life. A new fluorescent probe capable of detecting ONOO− with limit of detection down to 1.2 nM, response time less than 1s, and high recognition specificity over other similarly interfering species was developed in this work. For the probe constructed by conjugating an isatin moiety with an electron-withdrawing tricyanofuran (TCF) moiety, the former enabled a highly selective ONOO−-mediated oxidative decarbonylation reaction while the latter significantly improved the electrophilicity of the 3-position carbonyl group of isatin moiety and therefore accelerate the ONOO−-mediated nucleophilic attack, which eventually enabled prompt and efficient recognition reaction. For the decarbonylated product featured with a released primary aniline moiety, TCF acted as an acceptor for enabling an intramolecular charge transfer (ICT) process and the remarkable change in electronic feature upon reaction with ONOO−, which generated turn-on fluorescence with large contrast and therefore the basis for ONOO− sensing. The cell fluorescence imaging performed in this work definitely verified the capability of the probe for mapping intracellular ONOO−, despite the daunting elusive features of such physiological species.

Rapid biomonitoring of perfluoroalkyl substance exposures in serum by multisegment injection-nonaqueous capillary electrophoresis-tandem mass spectrometry.

Perfluoroalkyl substances (PFASs) are a major contaminant class due to their ubiquitous prevalence, persistence, and putative endocrine disrupting activity that may contribute to chronic disease risk notably with exposures early in life. Herein, multisegment injection-nonaqueous capillary electrophoresis-tandem mass spectrometry (MSI-NACE-MS/MS) is introduced as a high throughput approach for PFAS screening in serum samples following a simple methyl-tert-butyl ether (MTBE) liquid extraction. Separation and ionization conditions were optimized to quantify low nanomolar concentration levels of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) from serum extracts when using multiple reaction monitoring under negative ion mode conditions. Multiplexed separations of PFOA and PFOS were achieved with excellent throughput(<3min/sample), adequate concentration sensitivity (LOD ∼ 20nM, S/N=3) and good technical precision over three consecutive days of analysis (mean CV=9.1%, n=84). Accurate quantification of PFASs was demonstrated in maternal serum samples (n=16) when using MSI-CE-MS/MS following pre-column sample enrichment with median concentrations of 3.46nM (0.7-9.0nM) and 3.29nM (1.5-6.6nM) for PFOA and PFOS, respectively. This was lower than average PFAS exposures measured in pregnant women who had serum collected prior to 2009 likely due to subsequent phase out of their production. Overall, this method offers a convenient approach for large-scale biomonitoring of environmental exposures to legacy PFASs and their emerging replacements that is relevant to maternal health and chronic disease risk assessment in children.

New trends in single-molecule bioanalytical detection

Single-molecule sensing is becoming a major driver in biomarker assays as it is foreseen to enable precision medicine to enter into everyday clinical practice. However, among the single-molecule detection methods proposed so far, only a few are fully exploitable for the ultrasensitive label-free assay of biofluids. Firstly introduced single-molecule sensing platforms encompass low-background-noise fluorescent microscopy as well as plasmonic and electrical nanotransducers; these are generally able to sense at the nanomolar concentration level or higher. Label-based single-molecule technologies relying on optical transduction and microbeads that can scavenge and detect a few biomarkers in the bulk of real biofluids, reaching ultralow detection limits, have been recently commercialized. These assays, thanks to the extremely high sensitivity and convenient handling, are new trends in the field as they are paving the way to a revolution in early diagnostics. Very recently, another new trend is the label-free, organic bioelectronic electrolyte-gated large transistors that can potentially be produced by means of large-area low-cost technologies and have been proven capable to detect a protein at the physical limit in real bovine serum. This article offers a bird’s-eye view on some of the more significant single-molecule bioanalytical technologies and highlights their sensing principles and figures-of-merit such as limit of detection, need for a labelling step, and possibility to operate, also as an array, directly in real biofluids. We also discuss the new trend towards single-molecule proof-of-principle extremely sensitive technologies that can detect a protein at the zeptomolar concentration level involving label-free devices that potentially offer low-cost production and easy scalability.

Nanomolar detection of lead using electrochemical methods based on a novel phthalocyanine

4-4-[(Bromo-phenylimino)-methyl]-2-methoxy-phenoxy-phthalocyanine (CoTBrIMPPc) complex was synthesized and characterized by different spectroscopic as well as analytical techniques for the first time. The iminephthalocyanine derivative displayed redox peaks ascribed to cobalt (Co+2/Co+1) metal and phthalocyanine ligand (Pc−2/Pc−3). The (CoTBrIMPPc) complex was immobilized by drop coating method on the glassy carbon surface and the modified electrode was utilised for detecting lead (Pb) at nanomolar concentration level by voltammetry and amperometric methods. The cyclic voltammetric method showed linearity in the 100–1000 nmol L−1 range with the limit of detection (LOD) 37 nmol L−1. The addition of lead species did not show the considerable amperometric current response under normal amperometric conditions and hence experiments were performed by the modified methodology. Amperometry technique showed linearity in the 500 to 3000 nmol L−1 range, LOD value of 180 nmol L−1. The current response vs. Lead (Pb) concentration in graph by amperometric method exhibited correlation coefficient of 0.9991 and sensitivity of 0.0035 µA nM−1. The fabricated iminephthalocyanine based sensor is stable, reproducible and free of interference from other metal ion impurities in the electrolyte. The designed sensor has been employed for practical application.

CdSe quantum dots capped with a deep eutectic solvent as a fluorescent probe for copper(II) determination in various drinks.

The present study shows that copper(II) ions can be determined with a new fluorescent probe that is based on the use of CdSe quantum dots capped with deep eutectic solvent (DES-CdSe QDs). The capped QDs were prepared in aqueous phase by a one-step procedure under ambient atmosphere using selenium dioxide as a stable precursor for selenium, and ascorbic acid as non-toxic reducing agent. The deep eutectic solvent is composed of choline chloride and thioglycolic acid and acts as stabilizing and functionalizing agent. The fluorescent probe undergoes an increase in the fluorescence intensity (with excitation/emission wavelengths at 380/560nm) in the presence of Cu(II). Other ions display no significant effect on fluorescence. The effects of sample pH value, concentration of buffer, and volume of QDs solution were optimized by response surface methodology using a Box-Behnken statistical design. Under the optimal conditions, the response of the probe is linear in the 10-600nM Cu(II) concentration range, with a 5.3nM limit of detection. This is lower than the allowable maximum Cu(II) concentration in drinking water. The relative standard deviation of the method for five replicate measurements of Cu(II) at a 100nM concentration level is 2.0%. The probe was successfully applied to the determination of Cu(II) in various drinks. Graphical abstractSchematic representation of a fluorometric method for the determination of Cu(II) at nanomolar concentration levels. The fluorescent system consists of deep eutectic solvent-capped cadmium selenide quantum dots (DES-CdSe QDs). Fluorescence is strongly enhanced by copper(II).

Au nano-urchins enabled localized surface plasmon resonance sensing of beta amyloid fibrillation

Early stage detection of neurodegenerative diseases such as Alzheimer's disease (AD) is of utmost importance, as it has become one of the leading causes of death of millions of people. The gradual intellectual decline in AD patients is an outcome of fibrillation of amyloid beta 1–42 (Aβ1–42) peptides in the brain. In this paper, we present localized surface plasmon resonance (LSPR) based sensing of Aβ1–42 fibrillation using Au nano-urchins. Strongly localized field confinement at the spiky nanostructures of nano-urchin surfaces enables them to detect very low concentrations of Aβ1–42. In addition, the LSPR peak of Au nano-urchins, which is very sensitive to ambient conditions, shows significant responses at different fibrillation stages of Aβ1–42. Reduction in LSPR peak intensity with an increase in the fibrillation is chosen as the sensing parameter here. This paper in this context provides LSPR based highly sensitive, label-free and real-time sensing of Aβ1–42 fibrillation that is highly advantageous compared to the existing techniques which require binding additives or fluorescent biomarkers.

Self-assembly of pyrene boronic acid-based chemodosimeters for highly efficient mercury(II) ion detection

A new chemodosimeter consisting of pyrene and boronic acid (1) for the detection of Hg2+ ions is described. The amphiphilic nature of 1 leads to self-assembly in aqueous solution and the high electron density throughout the aggregated pyrene units provides an outstanding platform for energy and electron transport. Self-assembled 1 exhibits a selective and sensitive fluorescence response to Hg2+ ions, where the Hg2+ ion allows a fast transmetallation of 1, which drastically reduces its fluorescence. The Stern-Volmer (SV) quenching constant for the fluorescence quenching of self-assembled 1 by Hg2+ ions is approximately 1.8 × 106 M−1, and Hg2+ ions can be sensed with a detection limit of 6.6 × 10−9 M. In addition, self-assembled 1 exhibits excellent sensing performance at nano-molar concentration levels for Hg2+ ion contamination of tap water, fresh water, and seawater.

Gold nanoparticles stabilized with four kinds of amino acid-derived carbon dots for colorimetric and visual discrimination of proteins and microorganisms.

A colorimetric array is described for the sensitive discrimination of proteins and microorganisms. Carbon dots (CDs) were prepared from citric acid and one of the amino acids glycine, lysine, serine or aspartic acid. They act as stabilizers for gold nanoparticles (AuNPs). The interactions between target protein and the CD/AuNPs induce a different aggregation behavior. This provides the basis for colorimetric discrimination of protein species and results in color changes from red/purple to purple/blue. Specific response patterns are analyzed by linear discriminant analysis. Twelve kinds of proteins with different pI and molecular weight were visually discriminated at nanomolar concentration levels. Alternatively, discrimination can be performed by measurement of the ration of absorbance at 525nm and 620nm. The discrimination sensitivity is as low as 2nM. The method can differentiate between BSA and HSA. Twelve proteins were successfully distinguished in (spiked) urine samples. The discrimination accuracy is 100% at the 500nM protein concentration level. In addition, different strains of microorganisms (E. coli O157:H7, E.coli ER2738, P. aeruginosa CICC10204; P. aeruginosa CICC21954; B.subtilis CICC10071; B.subtilis CICC10275) can be discriminated successfully via this array. Graphical abstract A CD/AuNPs-based colorimetric array sensor is proposed for the discrimination of protein, offering a discrimination sensitivity low down to 2nM. The accurate differentiations of microorganisms originated from same species are achieved.

A high-affinity fluorescence probe for copper(II) ions and its application in fluorescence lifetime correlation spectroscopy.

Copper is one of the most important transition metals in many organisms where it catalyzes a manifold of different processes. As a result of copper's redox activity, organisms have to avoid unbound ions, and a dysfunctional copper homeostasis may lead to multifarious pathological processes in cells with very severe ramifications for the affected organisms. In many neurodegenerative diseases, however, the exact role of copper ions is still not completely clarified. In this work, a high-affinity and highly selective copper probe molecule, based on the naturally occurring tetrapeptide DAHK is synthesized. The sensor (log KD = - 12.8 ± 0.1) is tagged with a fluorescent BODIPY dye whose fluorescence lifetime distinctly decreases from 5.8ns ± 0.2ns to 0.4ns ± 0.1ns on binding to copper(II) cations. It is shown by using fluorescence lifetime correlation spectroscopy that the concentration of both probe and probe-copper complex can be simultaneously measured even at nanomolar concentration levels. This work presents a possible starting point for a new type of probe and method for future in vivo studies to further reveal the exact role of copper ions in organisms. Graphical abstract.

A Simple SERS-Based Trace Sensing Platform Enabled by AuNPs-Analyte/AuNPs Double-Decker Structure on Wax-Coated Hydrophobic Surface.

In this work, a simple and versatile SERS sensing platform enabled by AuNPs-analyte/AuNPs double-decker structure on wax-coated hydrophobic surface was developed using a portable Raman spectrometer. Wax-coated silicon wafer served as a hydrophobic surface to induce both aggregation and concentration of aqueous phase AuNPs mixed with analyte of interest. After drying, another layer of AuNPs was drop-cast onto the layer of AuNPs-analyte on the substrate to form double-decker structure, thus introducing more “hot spots” to further enhance the Raman signal. To validate the sensing platform, methyl parathion (pesticide), and melamine (a nitrogen-enrich compound illegally added to food products to increase their apparent protein content) were employed as two model compounds for trace sensing demonstration. The as-fabricated sensor showed high reproducibility and sensitivity toward both methyl parathion and melamine detection with the limit of detection at the nanomolar and sub-nanomolar concentration level, respectively. In addition, remarkable recoveries for methyl parathion spiked into lake water samples were obtained, while reasonably good recoveries for melamine spiked into milk samples were achieved. These results demonstrate that the as-developed SERS sensing platform holds great promise in detecting trace amount of hazardous chemicals for food safety and environment protection.

A β-diketonate−europium(III) complex-based time-gated luminescence probe for selective visualization of peroxynitrite in living cells

Herein, we designed and synthesized a new β-diketonate−Eu3+ complex-based luminescent probe for peroxynitrite (ONOO−), Eu(hdph)3(tpy), by using a 2,4-dimethoxyphenyl-substituted β-diketone ligand 1,1,1,2,2,3,3-hetafluoro-6-(2,4-dimethoxyphenyl)-4,6-hexanedione (hdph) and a coligand 2,2′,2″-terpyridine (tpy). The probe exhibits strong fluorescence with a great quantum yield of 25.6%. Upon the addition of ONOO−, the luminescence of Eu(hdph)3(tpy) at 607 nm was dramatically quenched due to the interaction of the 2,4-dimethoxyphenyl moiety with ONOO−, which leads to the deactivation of the excited Eu3+ complex and a 71-fold luminescence decrease. The dose-dependent luminescence decrease showed good linear relationship against the ONOO− concentration with the detection limit at nano-molar concentration level. In addition, the luminescence response of Eu(hdph)3(tpy) to ONOO− displayed high specificity over various reactive oxygen/nitrogen species. Taking advantage of the high sensitivity and specificity, Eu(hdph)3(tpy) was applied for the time-gated luminescence imaging of ONOO− in HepG2 cells. The results demonstrated the practical applicability of Eu(hdph)3(tpy) as a luminescent probe for the long-term visualization of intracellular ONOO−.

Enantioseparation of phenothiazines through capillary electrophoresis with solid phase extraction and polymer based stacking

This study developed a sensitive method involving capillary electrophoresis (CE) coupled with ultraviolet absorption for the simultaneous separation of chiral phenothiazine drugs at nanomolar concentration levels. The method consists of hydroxypropyl-γ-cyclodextrin (Hp-γ-CD) as a chiral selector and poly (diallyldimethylammonium chloride) (PDDAC)-based CE. Five pairs of d,l-phenothiazines were baseline separated using a background electrolyte containing 0.9% PDDAC, 5 mM Hp-γ-CD, and 100 mM tris(hydroxymethyl)aminomethane (Tris)-formate (pH 3.0). The five pairs were successfully stacked on the basis of the difference in viscosity between the PDDAC-containing background electrolyte and the sample solution, with almost no loss of resolution. The combination of a solid-phase extraction and PDDAC-mediated CE can efficiently improve the sensitivity of the phenothiazine enantiomers. Under optimal conditions, calibration graphs displayed the linear range between 6 and 1500 nM, with relative standard deviation values lower than 3.5% (n = 5). Detection limit ranged from 2.1 to 6.3 nM for target analytes, and 607- to 1555-fold enhancement was achieved. The practicality of using the proposed method to determine five pairs of d,l-phenothiazines in urine is also validated, in which recoveries between recoveries of all phenothiazines from urine ranged from 89% to 101%.

Cathodic electrogenerated chemiluminescence of aromatic Tb(III) chelates at polystyrene-graphite composite electrodes

Tb(III) chelates exhibit intense hot electron-induced electrogenerated chemiluminescence during cathodic polarization of metal/polystyrene-graphite (M/PG) electrodes in fully aqueous solutions. The M/PG working electrode provides a sensitive means for the determination of aromatic Tb(III) chelates at nanomolar concentration levels with a linear log-log calibration curve spanning more than five orders of magnitude. The charge transport and other properties of these novel electrodes were studied by electrochemiluminescence measurements and cyclic voltammetry. The present composite electrodes can by utilized both under pulse polarization and DC polarization unlike oxide-coated metal electrodes which do not tolerate cathodic DC polarization. The present cost-effective electrodes could be utilized e.g. in immunoassays where polystyrene is extensively used as a solid phase for various bioaffinity assays by using electrochemiluminescent Tb(III) chelates or e.g. Ru(bpy)32+as labels.

Micro-Raman spectroscopy as an enabling tool for long-term intracellular studies of nanomaterials at nanomolar concentration levels.

Given the importance of nanomaterials for medicine, health and biological sciences, a method for reliable intra-cellular tracking of nanocarbon materials at ultra-low concentrations was investigated. Namely, hyperspectral imaging of DNA-functionalized single-walled carbon nanotubes inside neural stem cells was demonstrated, over several mitosis cycles, also in a 3D z-stacking mode.