Siqi Xie

Bio: Siqi Xie is an academic researcher from Central South University. The author has contributed to research in topics: Fluorescence & Light emission. The author has an hindex of 6, co-authored 9 publications receiving 70 citations.

AIE-active metal–organic frameworks: facile preparation, tunable light emission, ultrasensitive sensing of copper(II) and visual fluorescence detection of glucose

Abstract: By binding aggregation-induced emission luminogens (AIEgens) with nanoscale ZIF-8, a series of novel luminescent metal–organic frameworks (LMOFs) with good photostability and excellent dispersibility have been facilely fabricated. The developed AIE-active MOFs not only inherit the intriguing AIE properties of AIEgens, including excited-state intramolecular proton transfer (ESIPT) properties, intense solid-state luminescence and large Stokes shifts (115–202 nm), but also show surprisingly boosted fluorescent emission efficiency (over 16 times) when compared with the original fluorescence of AIEgens. Meanwhile, the emission of AIE-active MOFs could also be finely engineered by varying the substituents on AIEgens. And as a proof of concept, the selected AIE-active MOF-2 (LMOF-2) served as a novel fluorescent probe for detecting copper ions (Cu2+), and a considerable response range (1–100 nM) and a sensitive picomolar detection limit (550 pM) were favorably obtained. More importantly, based on a glucose oxidase (GOD) catalyzed cascade redox reaction of LMOF-2/GOD nanocomposites, a fluorescent allochroic test strip was favourably developed for visual detection of glucose within a normal concentration range of fasting blood-glucose in human sera (3–8 mM), and has great potential to be applied in on-site assay of glucose in real serum samples due to its praiseworthy specificity and selectivity.

l-Pyroglutamic Acid-Modified CdSe/ZnS Quantum Dots: A New Fluorescence-Responsive Chiral Sensing Platform for Stereospecific Molecular Recognition.

Abstract: Stereoselective recognition of amino acids is extremely important due to its high chirality-dependent interactions and physiological activities in life activities. We herein report a novel functionalized chiral fluorescent nanosensor prepared from surface modification of CdSe/ZnS quantum dots (QDs) with pyroglutamic acid derivatives, which could serve as a chiral recognition module for fluorescence detection of chiral molecules. The sensor exhibited a unique stereoselective fluorescence response to histidine (His), glutamate (Glu), and dihydroxyphenylalanine (Dopa) and had preferable response performance to l-enantiomers. The enantiomeric fluorescence difference ratios of His, Glu, and Dopa enantiomers were 3.90, 3.40, and 2.49, respectively. The mechanism for the enantiomeric fluorescence recognition was systematically studied through a fluorescence spectrum, fluorescence life, and density functional theory (DFT) calculation. Presumably, the different hydrogen bonding capacity of the chiral recognition module with two enantiomers mainly contributed to the difference in fluorescence signals. As a result, a broader application of the pyroglutamic acid derivative-coated QDs as a fluorescence-responsive chiral sensing platform for enantiomeric detection would be expected.

Development of a “Dual Gates” Locked, Target-Triggered Nanodevice for Point-of-Care Testing with a Glucometer Readout

Abstract: Developing a facile and sensitive sensing platform is of importance for point-of-care testing (POCT). Herein, a sensitive and portable POCT platform based on “dual gates” aminated magnetic mesoporous silica nanocomposites (AMMS) bearing polydopamine (PDA)-aptamer (Apt) two-tier shells, as a novel nanodevice, is designed for target detection through a target-triggered glucose (GO) release from AMMS with personal glucometer (PGM) readout. In the absence of target, GO can be firmly captured in pores by the designed “dual gates”, which would decrease the high background signal of this system and ensure the accuracy of the detection results. Upon the introduction of the target molecules under acidic conditions (pH 5.5), the subsequent PDA self-degradation and the specific Apt-target reaction can cause the departure of “dual gates” and the opening of pores to release the loaded GO molecules, which could be quantitatively monitored by a portable PGM. It has been demonstrated that such POCT platform shows high se...

Low Temperature Greatly Enhancing Responses of Aptamer Electrochemical Sensor for Aflatoxin B1 Using Aptamer with Short Stem

Abstract: Aflatoxin B1 (AFB1), one of the most toxic mycotoxins, poses great health risks. Rapid and sensitive detection of AFB1 is important for food safety, environment monitoring, and health risk assessment. We report here the development of a simple and reusable electrochemical aptasensor for rapid and sensitive detection of AFB1. Main improvements were achieved through engineering an aptamer containing a short stem-loop structure and enhancing the binding affinity at a lower temperature. The DNA aptamer with a methylene blue (MB) label at one end was immobilized on a gold electrode. Upon AFB1 binding, the aptamer folded into a stem-loop structure and brought MB close to the electrode surface, resulting in increases in electric current. The aptamer having a shorter stem (2-4 bp) underwent a larger conformation change upon target binding. The sensors built with the aptamer containing a 2 bp stem generated much higher signal-on responses to AFB1 at 4 °C than at room temperature (25 °C). The improvements resulted in a detection limit of 6 pM, enabling the determination of trace AFB1 in a complex sample matrix. This study demonstrates that low temperature greatly enhances the performance of aptamer electrochemical sensors. This aptasensor is simple to construct and readily regenerated by washing with deionized water for reuse. This aptasensor strategy could be applied to the development of an electrochemical aptasensor for other targets.

Design and Property Modulation of Metal–Organic Frameworks with Aggregation-Induced Emission

Abstract: Fluorogens with aggregation-induced emission (AIEgens) are a unique type of luminescent materials for sensing and imaging applications. The integration of AIE characteristics into metal–organic fra...

Multifunctional aptasensors based on mesoporous silica nanoparticles as an efficient platform for bioanalytical applications: Recent advances

Abstract: Mesoporous silica nanoparticles (MSNs) are an essential and inseparable part of scientific application in today's world. These materials garnered more attention, in biosensing, catalysis, bioimaging, energy storage, and disease diagnosis due to their privileged futures. The unique physiochemical properties have been made these nanomaterials an excellent candidate for drug delivery applications as well as electrochemical and optical biosensing. MSNs are able to encapsulate enormous materials in their structural pores and deliver those materials to target, more meticulously. Aptasensor is type of biosensors that use aptamer for increasing selectivity and sensitivity. These are capture by nanomaterials by covalent and non-covalent linking for many different purpose such as diagnosis and target therapy. The aim of this review is introducing the most recent research progress on aptasensors based on MSNs, including various optical and electrochemical aptasensors, their strategy, and procedure, limit of detection, as well as their advantages and limitation. Moreover, different types of aptasensors based on MSNs is highlighted in this review for targeting and treatment of cancer cells. Although encouraging and interesting investigations have been achieved in this filed, design and mass production and effective biological application of aptasensors and MSNs based aptasensors are still challenging.

Ultrasensitive, Specific, and Rapid Fluorescence Turn-On Nitrite Sensor Enabled by Precisely Modulated Fluorophore Binding.

Abstract: The precise regulation of fluorophore binding sites in an organic probe is of great significance toward the design of fluorescent sensing materials with specific functions. In this study, a probe with specific fluorescence properties and nitrite detection ability is designed by precisely modulating benzothiazole binding sites. Only the fluorophore bond at the ortho-position of the aniline moiety can specifically recognize nitrite, which ensures that the reaction products displays a robust green emission. The unique 2-(2-amino-4-carboxyphenyl) benzothiazole (ortho-BT) shows superior nitrite detection performance, including a low detection limit (2.2 fg), rapid detection time ( 40 types of strong redox active, colored substances, nitro compounds, and metal ions. Moreover, the probe is highly applicable for the rapid on-site and semiquantitative measurement of nitrite. The proposed probe design strategy is expected to start a new frontier for the exploration of probe design methodology.