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Ene-reductase (ER) has been widely applied for asymmetrical synthesis of chiral intermediates due to its substrate promiscuity, photoexcited reactivity, and excellent property with producing two chiral centers at a time. Natural ERs often exhibit the same stereoselectivity, and they need to be engineered for opposite configuration of chiral compounds. The hydrogenation process toward activated alkenes by ERs is composed of reductive half reaction and oxidative half reaction, which are dependent upon two cofactors NAD(P)H and flavin mononucleotide. The catalytic activity of ERs will be affected by the size of the substrate, the activating strength of the electron-withdrawing groups, redox potential of cofactors, and the loop flexibility around catalytic cavity. Currently, protein engineering to ERs has been successfully employed to enhance various catalytic properties, including photoexcited asymmetric synthesis. This review summarizes the approaches to reverse the stereoselectivity and enhance catalytic activity of ERs and new applications of the engineered ERs in photobiocatalytic asymmetric synthesis, besides the discussion with the existing molecular mechanisms of mutants regarding the improved catalytic performance.
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Lanthanide-doped scintillators have the ability to convert the absorbed X-ray irradiation into ultraviolet (UV), visible (Vis), or near-infrared (NIR) light. Lanthanide-doped scintillators with excellent persistent luminescence (PersL) are emerging as a new class of PersL materials recently. They have attracted great attention due to their unique "self-luminescence" characteristic and potential applications. In this review, we comb through and focus on current developments of lanthanide-doped persistent luminescent scintillators (PersLSs), including their PersL mechanism, synthetic methods, tuning of PersL properties (e. g. emission wavelength, intensity, and duration time), as well as their promising applications (e. g. information storage, encryption, anti-counterfeiting, bio-imaging, and photodynamic therapy). We hope this review will provide valuable guidance for the future development of PersLSs.
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Förster or fluorescence resonance energy transfer (FRET) enables to probe biomolecular interactions, thus playing a vital role in bioassays. However, conventional FRET platforms suffer from limited sensitivity due to the low FRET efficiency and poor anti-interference of existing FRET pairs. Here we report a NIR-II (1000-1700 nm) FRET platform with extremely high FRET efficiency and exceptional anti-interference capability. This NIR-II FRET platform is established based on a pair of lanthanides downshifting nanoparticles (DSNPs) by employing Nd3+ doped DSNPs as an energy donor and Yb3+ doped DSNPs as an energy acceptor. The maximum FRET efficiency of this well-engineered NIR-II FRET platform reaches up to 92.2%, which is much higher than most commonly used ones. Owing to the all-NIR advantage (λex = 808 nm, λem = 1064 nm), this highly efficient NIR-II FRET platform exhibits extraordinary anti-interference in whole blood, and thus enabling background-free homogeneous detection of SARS-CoV-2 neutralizing antibodies in clinical whole blood sample with high sensitivity (limit of detection = 0.5 µg/mL) and specificity. This work opens up new opportunities for realizing highly sensitive detection of various biomarkers in biological samples with severe background interference.
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Förster resonance energy transfer (FRET)-based homogeneous immunoassay obviates tedious washing steps and thus is a promising approach for immunoassays. However, a conventional FRET-based homogeneous immunoassay operating in the visible region is not able to overcome the interference of complex biological samples, thus resulting in insufficient detection sensitivity and poor accuracy. Here, we develop a near-infrared (NIR)-to-NIR FRET platform (Ex = 808 nm, Em = 980 nm) that enables background-free high-throughput homogeneous quantification of various biomarkers in complex biological samples. This NIR-to-NIR FRET platform is portable and easy to operate and is mainly composed of a high-performance NIR-to-NIR FRET pair based on lanthanide-doped nanoparticles (LnNPs) and a custom-made microplate reader for readout of NIR luminescence signals. We demonstrate that this NIR-to-NIR FRET platform is versatile and robust, capable of realizing highly sensitive and accurate detection of various critical biomarkers, including small molecules (morphine and 1,25-dihydroxyvitamin D), proteins (human chorionic gonadotropin), and viral particles (adenovirus) in unprocessed complex biological samples (urine, whole blood, and feces) within 5-10 min. We expect this NIR-to-NIR FRET platform to provide low-cost healthcare for populations living in resource-limited areas and be widely used in many other fields, such as food safety and environmental monitoring.
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Luminescence concentration quenching exists widely in lanthanide-doped luminescent nanomaterials, and significantly hinders their emission intensity. In this work, we report the concentration-quenching-free properties of the 406 nm emission in Pr3+-doped nanoscintillators, which is attributed to the large energy gap between the 1S0 and 1I6 states (ΔE = â¼25 000 cm-1) of Pr3+ ions, preventing the concentration quenching effects caused by both cross-relaxation and energy migration to surface quenchers. This work provides further understanding about the concentration quenching effect of lanthanide-doped luminescent nanomaterials and a new perspective for avoiding detrimental concentration quenching. In addition, we also demonstrate the potential use of Pr3+-doped nanoscintillators as anti-counterfeiting materials.
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Near-infrared (NIR) refers to the section of the spectrum from 650 to 2500 nm. NIR luminescent materials are widely employed in organic light-emitting diodes (OLEDs), fiber optic communication, sensing, biological detection, and medical imaging. This paper reviews organic NIR electroluminescent materials, including organic NIR electrofluorescent materials and organic NIR electrophosphorescent materials that have been investigated in the past 6 years. Small-molecule, polymer NIR fluorescent materials and platinum(II) and iridium(III) complex NIR phosphorescent materials are described, and the limitations of the development of NIR luminescent materials and future prospects are discussed.