ABSTRACT
A new series of alkaline earthides based on Cryptand [2.2.2] (C222) containing nine complexes is designed by carefully placing alkali metals and alkaline earth metals inside and outside the C222 complexant, respectively i.e., M1(C222)M2 (M1 = Li, Na, K; M2 = Be, Mg, Ca). The designed complexes are reasonably stable both electronically and thermodynamically, as revealed through their vertical ionization potentials (VIPs) and interaction energies, respectively. Moreover, the true alkaline earthide nature of the complexes is confirmed through NBO and FMO analyses showing the negative charges and HOMOs over the alkaline earth metals, respectively. The further validity of true earthide characteristic is represented graphically by the spectra of partial density of states (PDOS). HOMO-LUMO gaps of the compounds are also very small (from 2.23 to 2.83 eV) when compared with pure cage's (C222) H-L gap i.e., 5.63 eV. All these features award these complexes with very small values of transition energies (ΔE) ranging from 0.68 to 2.06 eV ultimately resulting in remarkably high hyperpolarizability values up to 2.7 × 105 au (for Na+(C222)Mg-). Furthermore, applying external electric field (EEF) on the complexes enhances hyperpolarizability further. A remarkable increase of 1000 folds has been seen when hyperpolarizability of K+(C222)Ca- is calculated after EEF application i.e., from 8.79 × 104 au to 2.48 × 107 au; when subjected to 0.001 au external electric field.
ABSTRACT
A molybdenum sulfide/zirconium oxide/Nafion (MoS2/ZrO2/Naf) based electrochemiluminescence (ECL) aptasensor for the selective and ultrasensitive detection of ApoA1 is proposed, with Ru(bpy)3 2+ as the luminophore. The chitosan (CS) modification on the nanocomposite layer allowed glutaraldehyde (GLUT) cross-linking, resulting in the immobilization of ApoA1 aptamers. Scanning electron microscopy, tunneling electron microscopy, and energy dispersive X-ray spectroscopy were used to characterize the nanocomposite, while electrochemiluminescence (ECL), cyclic voltammetry, and electrochemical impedance spectroscopy were used to analyze the aptasensor assembly. The nanocomposite was used as an electrode modifier, which increased the intensity of the ECL signal. Due to the anionic environment produced on the sensor surface following the specific interaction of the ApoA1 biomarker with the sensor, more Ru(bpy)3 2+ were able to be electrostatically attached to the aptamer-ApoA1 complex, resulting in enhanced ECL signal. The ECL aptasensor demonstrated outstanding sensitivity for ApoA1 under optimal experimental conditions, with a detection limit of 53 fg/mL and a wide linear dynamic range of 0.1-1000 pg/mL. The potential practical applicability of this aptasensor was validated by analyzing ApoA1 in human serum samples, with recovery rates of 94-108% (n = 3). The proposed assay was found to be substantially better compared to the commercially available enzyme-linked immunosorbent assay method, as reflected from over 1500 times improvement in the detection limit for ApoA1.
ABSTRACT
Magnetic resonance imaging (MRI) is an excellent imaging modality. However the low sensitivity of the technique poses a challenge to achieving an accurate image of function at the molecular level. To overcome this, contrast agents are used; typically gadolinium based agents for T1 weighted imaging, or iron oxide based agents for T2 imaging. Traditionally, only one imaging mode is used per diagnosis although several physiological situations are known to interfere with the signal induced by the contrast agents in each individual imaging mode acquisition. Recently, the combination of both T1 and T2 imaging capabilities into a single platform has emerged as a tool to reduce uncertainties in MR image analysis. To date, contradicting reports on the effect on the contrast of the coupling of a T1 and T2 agent have hampered the application of these specialised probes. Herein, we present a systematic experimental study on a range of gadolinium-labelled magnetite nanoparticles envisioned to bring some light into the mechanism of interaction between T1 and T2 components, and advance towards the design of efficient (dual) T1 and T2 MRI probes. Unexpected behaviours observed in some of the constructs will be discussed. In this study, we demonstrate that the relaxivity of such multimodal probes can be rationally tuned to obtain unmatched potentials in MR imaging, exemplified by preparation of the magnetite-based nanoparticle with the highest T2 relaxivity described to date.
