Lipid Coating Modulates Effects of Nanoceria on Oxidative Metabolism in Human Embryonic Lung Fibroblasts: A Case of Cardiolipin

The unique redox properties of nanoscale cerium dioxide determine its diverse application in biology and medicine as a regulator of oxidative metabolism. Lipid modifiers of the nanoparticle surface change their biochemical properties and bioavailability. Complexes with lipids can be formed upon contact of the nanoparticles with the membrane. The effects of lipid coating on nanoceria have not been studied yet. Here, we assessed the effect of bare and cardiolipin-coated CeO2 on the expression of oxidative metabolism genes in human embryonic lung fibroblasts. Cell viability, mitochondrial activity, intracellular reactive oxygen species, NOX4, NRF2, and NF-κB expression, oxidative DNA damage/repair, autophagy, and cell proliferation were studied. We used an MTT assay, fluorescence microscopy, real-time reverse transcription polymerase chain reaction, and flow cytometry. At a concentration of 1.5 μM, bare and cardiolipin-coated nanoceria penetrated into cells within 1-3 h. Cell survival, mitochondrial activity, and the proliferative effect were similar for bare and cardiolipin-coated nanoceria. Intracellular ROS, activation of NOX4, NRF2, and NF-kB, DNA oxidative damage, and DNA break/repair were different. Cardiolipin-coated nanoceria induced intracellular oxidative stress and short-term activation of these genes and DNA damage/break/repair. Unlike bare nanoceria, cardiolipin-coated nanoceria induced autophagy. Thus, the effects of cardiolipin-coated nanoceria are determined by both the nanoceria itself and cardiolipin. Presumably, the differences in properties are due to lipid peroxidation of cardiolipin. This effect needs to be taken into account when developing nanoceria-based drugs targeting mitochondria.

Croix CM, Mao G, Kapralov A, Bayir H, Kagan VE, Yang D. Visualizing Cardiolipin In Situ with HKCL-1M, a Highly Selective and Sensitive Fluorescent Probe

Reliable probing of cardiolipin (CL) content in dynamic cellular milieux presents significant challenges and great opportunities for understanding mitochondria-related diseases, including cancer, neurodegeneration, and diabetes mellitus. In intact respiring cells, selectivity and sensitivity for CL detection are technically demanding due to structural similarities among phospholipids and compartmental secludedness of the inner mitochondrial membrane. Here, we report a novel "turn-on" fluorescent probe HKCL-1M for detecting CL in situ. HKCL-1M displays outstanding sensitivity and selectivity toward CL through specific noncovalent interactions. In live-cell imaging, its hydrolyzed product HKCL-1 efficiently retained itself in intact cells independent of mitochondrial membrane potential (Δψm). The probe robustly co-localizes with mitochondria and outperforms 10-N-nonyl acridine orange (NAO) and Δψm-dependent dyes with superior photostability and negligible phototoxicity. Our work thus opens up new opportunities for studying mitochondrial biology through efficient and reliable visualization of CL in situ.

Fluorescence 'turn-on' probe for Al3+ detection in water based on ZnS/ZnO quantum dots with excellent selectivity and stability

In this work, an efficient and stable fluorescent probe for Al³⁺was established. The fluorescent probe based on the fluorescence 'turn-on' mode of zinc sulfide crystal composite zinc oxide quantum dots (ZnS/ZnO QDs). The ZnS/ZnO QDs were synthesized via two-step method using L-Cysteine (L-Cys) as a sulfur source and stabilizer. In the synthesis of ZnS/ZnO QDs, the fluorescence of zinc oxide quantum dots (ZnO QDs) decreased and its stability increased in aqueous solution after the addition of L-Cys. In addition, the as-synthesized ZnS/ZnO QDs shows fluorescent enhancement to Al³⁺. The ZnS/ZnO QDs based fluorescence 'turn-on' probe presented wide linear ranges (1 nM-8μM and 8-100μM). The availability of as-established sensing probe was also estimated by real water sample tests. Furthermore, the fluorescent enhancing mechanism was carried out by recording the fluorescent lifetime of samples, which might be related to the QDs dispersion and charge transfer weaken.

Smart phone assisted, rapid, simplistic, straightforward and sensitive biosensing of cysteine over other essential amino acids by β-cyclodextrin functionalized gold nanoparticles as a colorimetric probe

Herein, we have attempted the synthesis of β-CD functionalized AuNPs and then applied them as a colorimetric assay for the quantification of Cys over other different essential amino acids.

A novel and sensitive chemosensor based on a KMnO4–rhodamine B–CdS quantum dot chemiluminescence system for meropenem detection

The reaction of a KMnO₄–Rh B–l-cysteine capped CdS QD system is described as a novel chemiluminescence (CL) reaction. Meropenem exhibits a quenching effect on KMnO₄–Rh B–l-cysteine capped CdS QDs.

Comparison of two methods for selegiline determination: A flow-injection chemiluminescence method using cadmium sulfide quantum dots and corona discharge ion mobility spectrometry

Two analytical approaches including chemiluminescence (CL) and corona discharge ionization ion mobility spectrometry (CD-IMS) were developed for sensitive determination of selegiline (SG). We found that the CL intensity of the KMnO4-Na2S2O3 CL system was significantly enhanced in the presence of L-cysteine capped CdS quantum dots (QDs). A possible CL mechanism for this CL reaction is proposed. In the presence of SG, the enhanced CL system was inhibited. Based on this inhibition, a simple and sensitive flow-injection CL method was proposed for the determination of SG. Under optimum experimental conditions, the decreased CL intensity was proportional to SG concentration in the range of 0.01 to 30.0 mg L(-1). The detection limit (3σ) was 0.004 mg L(-1). Also, SG was determined using CD-IMS, and under optimum conditions of CD-IMS, calibration curves were linear in the range of 0.15 to 42.0 mg L(-1), with a detection limit (3σ) of 0.03 mg L(-1). The precision of the two methods was calculated by analyzing samples containing 5.0 mg L(-1) of SG (n=11). The relative standard deviations (RSDs%) of the flow-injection CL and CD-IMS methods are 2.17% and 3.83%, respectively. The proposed CL system exhibits a higher sensitivity and precision than the CD-IMS method for the determination of SG.

A simple and sensitive flow injection method based on the catalytic activity of CdS quantum dots in an acidic permanganate chemiluminescence system for determination of formaldehyde in water and wastewater

The intensity of emitted light from KMnO₄–HCHO–CdS QDs system is linearly proportional to HCHO concentration.

pH-Driven Ordering Transitions in Liquid Crystal Induced by Conformational Changes of Cardiolipin

We report an investigation of interfacial phenomena occurring at aqueous-liquid crystal (LC) interfaces that triggers an orientational ordering transition of the LC in the presence of cardiolipin (CL) by varying pH, salt concentration and valence. In particular, the effects of three different conformational isomeric forms of the CL are observed to cause the response of the LC ordering to vary significantly from one to another at those interfaces. An ordering transition of the LC was observed when the CL is mostly in undissociated (at pH 2) and/or in bicyclic (at pH 4) conformation in which LC shows changes in the optical appearance from bright to dark. By contrast, no change in the optical appearance of the LC was observed when the pH of the system increases to 8 or higher in which the CL mostly exists in the open conformation. Fluorescence microscopy measurements further suggest that pH-dependent conformational forms of the CL have different ability to self-assemble (thus different packing efficiency) at aqueous-LC interfaces leading to dissimilar orientational behavior of the LC. Specifically, we found that change in headgroup-headgroup repulsion of the central phosphatidyl groups of the CL plays a key role in tuning the lipid packing efficiency and thus responses to interfacial phenomena. Orientational ordering transition of the LC was also observed as a function of increasing the ionic strength (buffer capacity) and strongly influenced in the presence of mono and divalent cations. Langmuir-Blodgett (LB) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements provide further insight in modulation of the lipid packing efficiency and alkyl chain conformation of the CL at different pH and ionic conditions. Overall, the results presented in this paper establish that LCs offer a promising approach to differentiate different conformations (label free detection) of the CL through ordering transition of the LC at aqueous-LC interfaces.

A study of optical absorption of cysteine-capped CdSe nanoclusters using first-principles calculations

Optical absorption of cysteine-capped CdSe nanoclusters varies with cluster size, ligands and solvents.

Characterization of L-cysteine capped CdTe quantum dots and application to test Cu(II) deficiency in biological samples from critically ill patients

The catalytic activity of copper ion gives, from the physiological point of view, a central role in many biological processes. Variations in the composition and location of cellular copper have been addressed given their physiological and pathological consequences. In this paper L-cysteine capped CdTe quantum dots is used for the fluorimetric determination of Cu(II) in biological samples from healthy individuals and patients admitted to the Intensive Care Units (ICU). An acceptable homogeneity in the CdTe QDs size has been obtained with an average value of 3 nm. No significant alterations in the spectral properties were observed for 2 months when stored in vacutainers at 6°C and a concentration of approximately 2 μM. Data from oxidative stress markers such superoxide dismutase, total antioxidant capacity and DNA damage can be correlated with a Cu(II) deficiency for the ICU patients as measured by flame-atomic absorption spectroscopy (FAAS) and inductively coupled plasma source mass spectrometry (ICP-MS). Aqueous solutions 0.3 μM of L-cysteine capped CdTe QDs in MOPS buffer (6 mM, pH 7.4) used at 21°C in the range 15-60 min after preparation of the sample for the measurements of fluorescence gives contents in Cu(II) for erythrocytes in good agreement with those obtained in FAAS and ICP-MS but the comparative ease of use makes the fluorimetric technique more suitable than the other two techniques for routine analysis.

Determination of lapachol in the presence of other naphthoquinones using 3MPA-CdTe quantum dots fluorescent probe

3MPA-CdTe QDs in aqueous dispersion was used as a fluorescent probe for the determination of lapachol, a natural naphthoquinone found in plants of the Bignoniaceae family genus Tabebuia. Working QDs dispersions (4.5×10(-8) mol L(-1) of QDs) was prepared in aqueous media containing Tris-HCl buffer pH 7.4 and methanol (10% in volume). The excitation was made at 380 nm with signal measurement at 540 nm. To establish a relationship between fluorescence (corrected to inner filter effect) and concentration of lapachol, a Stern-Volmer model was used. The linear range obtained was from 1.0×10(-5) to 1.0×10(-4) mol L(-1). The limit of detection (x(b)-3s(b)) was 8.0×10(-6) mol L(-1). The 3MPA-CdTe QDs probe was tested in the determination of lapachol in urine, previously cleansed in an acrylic polymer. The average recovery was satisfactory.

Facile aqueous synthesis of functionalized CdTe nanoparticles and their application as fluorescence probes for determination of adenine and guanine

Thioglycolic acid (TGA)-capped CdTe nanoparticles (NPs) were synthesized in aqueous medium, and their application as fluorescence probes in the detection of adenine and guanine was studied. The TGA-capped CdTe NPs were characterized by transmission electron microscopy, X–ray diffraction spectrometry, spectrofluorometry, Fourier transform infrared, and ultraviolet-visible spectrometry. Based on the significant enhancement of fluorescence emission of these CdTe fluorescence probes in the presence of adenine or guanine, a quantitative analysis method for these purines was proposed. Experimental conditions that govern the extent of fluorescence enhancement were optimized. Under the optimal conditions, the relative fluorescence intensity versus adenine or guanine concentrations gave a linear response, permitting the dynamic range of 7.0 × 10−7–1.0 × 10−4 mol/L and 6.0 × 10−7–9.0 × 10−5 mol/L for adenine and guanine, respectively. The method has also been applied successfully to the detection of adenine and guanine in synthetic samples with satisfactory results.

Biotin-modified glutathione as a functionalized coating for bioconjugation of CdTe-based quantum dots

In this study, biotin-conjugated glutathione was synthesized using peptide bonding of the biotin carboxy group and amino group of the γ-glutamic acid to prepare an alternative coating for CdTe quantum dots (QDs). This type of coating combines the functionality of the biotin with the fluorescent properties of the QDs to create a specific, high-affinity fluorescent probe able to react with avidin, streptavidin and/or neutravidin. Biotin-functionalized glutathione-coated CdTe QDs were prepared by a simple one-step method using Na₂ TeO₃ and CdCl₂. Obtained QDs were separated from the excess of the biotin-conjugated glutathione by CE employing 300 mM borate buffer with pH 7.8 as a background electrolyte. The detection of sample components was performed by the photometric detection at 214 nm and LIF employing Ar⁺ ion laser (488 nm).