A highly sensitive fluorescent sensor for ammonia detection based on aggregation-induced emission luminogen-doped liquid crystals.

As a toxic substance, ammonia can cause serious irritation to the human respiratory system and lungs. Although many detection techniques have been reported, most of them have drawbacks, such as expensive devices and complex and time-consuming fabrication processes. Thus, it is important to develop a simple method for ammonia detection. In this paper, we demonstrate a highly sensitive fluorescent sensor for ammonia detection based on aggregation-induced emission luminogen-doped liquid crystals without the use of polarizers. The homeotropic orientation of the liquid crystals on a modified substrate can be disturbed by ammonia, resulting in the fluorescence intensity change of an aggregation-induced emission luminogen. This aggregation-induced emission luminogen-doped liquid crystal-based fluorescent sensor for ammonia detection exhibited a low detection limit of 5.4 ppm, which is 3 times lower than previously reported liquid crystal-based optical sensors. The detection range is also broad from 0 ppm to 1600 ppm. Meanwhile, this sensor can be applied to detect aqueous ammonia with a low limit of detection of 1.8 ppm. The proposed fluorescent sensor for ammonia detection based on an aggregation-induced emission luminogen-doped liquid crystal is highly sensitive, highly selective, simple, and low cost with wide potential applications in chemical and biological fields. This strategy of designing a liquid crystal fluorescent sensor provides an inspiring stage for other toxic chemical substrates by changing specific decorated molecules.

Nasality outcome in unilateral chronic rhinosinusitis following functional endoscopic sinus surgery.

BACKGROUND/PURPOSE: In this study we aimed to investigate the prevalence of abnormal nasality in patients with unilateral rhinosinusitis and their nasality outcomes following functional endoscopic sinus surgery (FESS). METHODS: A total of 42 patients with unilateral chronic rhinosinusitis who underwent unilateral FESS between April 2016 and November 2017 were enrolled. Questionnaires on sinonasal symptoms and nasality were recorded. The change in the nasalance score of vowels [a], [i] [u], nasal consonant [m], 2 nasal syllable repetitions, and 2 Chinese sentences were measured. The patients were evaluated preoperatively, 6 months, and 12 months after the operation. The patients were divided into two groups, wide opening surgery and limited surgery, according to the severity of the disease. RESULTS: Among 42 patients, the subjective reports showed that one-third of unilateral chronic rhinosinusitis (CRS) patients had abnormal nasality preoperatively and significant improvement following FESS. The Lund-Mackay score was significantly negatively correlated with preoperative nasalance of [i] and positively correlated with change of nasalance of [i]. The increase in the value of [i] is statistically significant (p = 0.01) following FESS. In the further subgroup analysis, the change in nasalance was significant in the wide opening surgery group, but not in the limited surgery group. CONCLUSION: Although only one side of the nasal airway was involved, one-third of the patients reported abnormal nasality. In patients with more disease severity who underwent wide opening surgery, the nasalance significantly increased 1 year after FESS. The increase in the objective nasalance score was corresponded to a significant improvement of subjective self-reported nasality assessment postoperatively.

Aptamer Laden Liquid Crystals Biosensing Platform for the Detection of HIV-1 Glycoprotein-120.

We report a label-free and simple approach for the detection of glycoprotein-120 (gp-120) using an aptamer-based liquid crystals (LCs) biosensing platform. The LCs are supported on the surface of a modified glass slide with a suitable amount of B40t77 aptamer, allowing the LCs to be homeotropically aligned. A pronounced topological change was observed on the surface due to a specific interaction between B40t77 and gp-120, which led to the disruption of the homeotropic alignment of LCs. This results in a dark-to-bright transition observed under a polarized optical microscope. With the developed biosensing platform, it was possible to not only identify gp-120, but obtained results were analyzed quantitatively through image analysis. The detection limit of the proposed biosensing platform was investigated to be 0.2 µg/mL of gp-120. Regarding selectivity of the developed platform, no response could be detected when gp-120 was replaced by other proteins, such as bovine serum albumin (BSA), hepatitis A virus capsid protein 1 (Hep A VP1) and immunoglobulin G protein (IgG). Due to attributes such as label-free, high specificity and no need for instrumental read-out, the presented biosensing platform provides the potential to develop a working device for the quick detection of HIV-1 gp-120.

Production of isopropyl and butyl esters by Clostridium mono-culture and co-culture.

Production of esters from the acetone-butanol-ethanol (ABE) fermentation by Clostridium often focuses on butyl butyrate, leaving acetone as an undesired product. Addition of butyrate is also often needed because ABE fermentation does not produce enough butyrate. Here we addressed the problems using Clostridium beijerinckii BGS1 that preferred to produce isopropanol instead of acetone, and co-culturing it with Clostridium tyrobutyricum ATCC 25,755 that produced butyrate. Unlike acetone, isopropanol could be converted into ester using lipase and acids. C. tyrobutyricum ATCC 25,755 produced acids at pH 6, while C. beijerinckii BGS1 produced mainly solvents at the same pH. When the two strains were co-cultured, more butyrate was produced, leading to a higher titer of esters than the mono-culture of C. beijerinckii BGS1. As the first study reporting the production of isopropyl butyrate from the Clostridium fermentation, this study highlighted the potential use of lipase and co-culture strategy in ester production.

Flow-driven disclination lines of nematic liquid crystals inside a rectangular microchannel.

For nematic liquid crystals (LCs), a disclination line is formed when the director of the LCs changes abruptly. In this study, we demonstrate an approach to form dynamic disclination lines by flowing the nematic liquid crystal 4-cyano-4'-pentylbiphenyl (5CB) in rectangular microchannels with a large aspect ratio. The dynamic disclination line moves gradually from the side toward the centre of the microchannel when the Ericksen number reaches 8.5. At the critical Ericksen number, influence of the anchoring energy on the side wall extends to the centre of the microchannel and determines the final position of the dynamic disclination line. As a result, the orientation of the LC is influenced by surface defects of the side wall. This phenomenon can be used to detect minute surface defects on the side wall and is potentially useful for visual sensing applications that require high sensitivity.

Immobilization of Enzymes on Flexible Tubing Surfaces for Continuous Bioassays.

Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it is more difficult to use them in a continuous process. Herein, we develop an enzyme immobilization technique for flexible tubing surfaces, which can be used to catalyze biochemical reactions in a continuous process. In this technique, the tubing is first treated with (3-aminopropyl)triethoxysilane at 50 °C and baked at 100 °C in vacuum to form a network of reactive amine functional group on the inner tubing surface. Subsequently, dextran polyaldehyde, a polymeric cross-linker, is used to immobilize crude protease extract and catalase for hydrolyzing casein and degrading H2O2, respectively, in a continuous process. The immobilized proteases are highly stable even after a long-term storage at 4 °C. After 12 weeks of storage, 90% of the original protease activity can be preserved. Meanwhile, the immobilized catalase is able to degrade 0.1% H2O2 solution flowing at 5 µL/min. The immobilization technique is potentially useful for bioassays and industrial wastewater treatments when continuous processes are preferred.

Graphene oxide conjugated with polymers: a study of culture condition to determine whether a bacterial growth stimulant or an antimicrobial agent?

BACKGROUND: The results showed that the deciding factor is the culture medium in which the bacteria and the graphene oxide (GO) are incubated at the initial manipulation step. These findings allow better use of GO and GO-based materials more and be able to clearly apply them in the field of biomedical nanotechnology. RESULTS: To study the use of GO sheets applied in the field of biomedical nanotechnology, this study determines whether GO-based materials [GO, GO-polyoxyalkyleneamine (POAA), and GO-chitosan] stimulate or inhibit bacterial growth in detail. It is found that it depends on whether the bacteria and GO-based materials are incubated with a nutrient at the initial step. This is a critical factor for the fortune of bacteria. GO stimulates bacterial growth and microbial proliferation for Gram-negative and Gram-positive bacteria and might also provide augmented surface attachment for both types of bacteria. When an external barrier that is composed of GO-based materials forms around the surface of the bacteria, it suppresses nutrients that are essential to microbial growth and simultaneously produces oxidative stress, which causes bacteria to die, regardless of whether they have an outer-membrane-Gram-negative-bacteria or lack an outer-membrane-Gram-positive-bacteria, even for high concentrations of biocompatible GO-POAA. The results also show that these GO-based materials are capable of inducing reactive oxygen species (ROS)-dependent oxidative stress on bacteria. Besides, GO-based materials may act as a biofilm, so it is hypothesized that they suppress the toxicity of low-dose chitosan. CONCLUSION: Graphene oxide is not an antimicrobial material but it is a general growth enhancer that can act as a biofilm to enhance bacterial attachment and proliferation. However, GO-based materials are capable of inducing ROS-dependent oxidative stress on bacteria. The applications of GO-based materials can clearly be used in antimicrobial surface coatings, surface-attached stem cells for orthopedics, antifouling for biocides and microbial fuel cells and microbial electro-synthesis.

Loss of the ssrA genome island led to partial debromination in the PBDE respiring Dehalococcoides mccartyi strain GY50.

Polybrominated diphenyl ethers (PBDEs), chemicals commonly used as flame-retardants in consumer products, are emerging persistent organic pollutants that are ubiquitous in the environment. In this study, we report a PBDE-respiring isolate - Dehalococcoides mccartyi strain GY50, which debrominates the most toxic tetra- and penta-BDE congeners (∼1.4 µM) to diphenyl ether within 12 days with hydrogen as the electron donor. The complete genome sequence revealed 26 reductive dehalogenase homologous genes (rdhAs), among which three genes (pbrA1, pbrA2 and pbrA3) were highly expressed during PBDE debromination. After 10 transfers of GY50 with trichloroethene or 2,4,6-trichlorophenol as the electron acceptor instead of PBDEs, the ssrA-specific genome island (ssrA-GI) containing pbrA1 and pbrA2 was deleted from the genome of strain GY50, leading to two variants (strain GY52 with trichloroethene, strain GY55 with 2,4,6-trichlorophenol) with identically impaired debromination capabilities (debromination of penta-/tetra-BDEs ceased at di-BDE 15). Through analysis of Illumina paired-end sequencing data, we identified read pairs that probably came from variants that contain ssrA-GI deletions, indicating their possible presence in the original strain GY50 culture. The two variant strains provide real-time examples on rapid evolution of organohalide-respiring organisms. As PBDE-respiring organisms, GY50-like strains may serve as key players in detoxifying PBDEs in contaminated environments.

Quantitative proteome profiles help reveal efficient xylose utilization mechanisms in solventogenic Clostridium sp. strain BOH3.

Development of sustainable biobutanol production platforms from lignocellulosic materials is impeded by inefficient five carbon sugar uptake by solventogenic bacteria. The recently isolated Clostridium sp. strain BOH3 is particularly advantaged in this regard as it serves as a model organism which can simultaneously utilize both glucose and xylose for high butanol (>15 g/L) production. Strain BOH3 was, therefore, investigated for its metabolic mechanisms for efficient five carbon sugar uptake using a quantitative proteomics based approach. The proteomics data show that proteins within the CAC1341-1349 operon play a pivotal role for efficient xylose uptake within the cells to produce butanol. Furthermore, up-regulation of key enzymes within the riboflavin synthesis pathway explained that xylose could induce higher riboflavin production capability of the bacteria (e.g., ∼80 mg/L from glucose vs. ∼120 mg/L from xylose). Overall results from the present experimental approach indicated that xylose-fed BOH3 cultures are subjected to high levels of redox stress which coupled with the solvent stress-trigger a sporulation response within the cells earlier than the glucose-fed cultures. The study lays the platform for metabolic engineering strategies in designing organisms for efficient butanol and other value-added chemicals such as riboflavin production. Biotechnol. Bioeng. 2017;114: 1959-1969. © 2017 Wiley Periodicals, Inc.

Recent developments in protease activity assays and sensors.

Proteases play a pivotal role in regulating important physiological processes from food digestion to blood clotting. They are also important biomarkers for many diseases such as cancers. The importance of proteases has led to extensive efforts in the screening of proteases and their inhibitors as potential drug molecules. For example, human immunodeficiency virus (HIV) patients have been treated with HIV-1 protease inhibitors to prolong the life expectancy of patients. Such a close relationship between diseases and proteases provides a strong motivation for developing sensitive, selective, and robust protease assays and sensors, which can be exploited to discover new proteases and inhibitors. In this aspect, protease assays based on levels of proteolytic activities are more relevant than protease affinity assays such as immunoassays. In this review, recent developments of protease activity assays based on different detection principles are discussed and compared. For homogenous assays, fluorescence-based techniques are the most popular due to their high sensitivity and quantitative results. However, homogeneous assays have limited multiplex sensing capabilities. In contrast, heterogeneous assays can be employed to detect multiple proteases simultaneously, given the microarray technology that is already available. Among them, electrochemical methods, surface spectroscopy techniques, and enzyme-linked peptide protease assays are commonly used. Finally, recent developments in liquid crystal (LC)-based protease assays and their applications for detecting proteases and their inhibitors are discussed.

Genomic characterization of three unique Dehalococcoides that respire on persistent polychlorinated biphenyls.

Fastidious anaerobic bacteria play critical roles in environmental bioremediation of halogenated compounds. However, their characterization and application have been largely impeded by difficulties in growing them in pure culture. Thus far, no pure culture has been reported to respire on the notorious polychlorinated biphenyls (PCBs), and functional genes responsible for PCB detoxification remain unknown due to the extremely slow growth of PCB-respiring bacteria. Here we report the successful isolation and characterization of three Dehalococcoides mccartyi strains that respire on commercial PCBs. Using high-throughput metagenomic analysis, combined with traditional culture techniques, tetrachloroethene (PCE) was identified as a feasible alternative to PCBs to isolate PCB-respiring Dehalococcoides from PCB-enriched cultures. With PCE as an alternative electron acceptor, the PCB-respiring Dehalococcoides were boosted to a higher cell density (1.2 × 10(8) to 1.3 × 10(8) cells per mL on PCE vs. 5.9 × 10(6) to 10.4 × 10(6) cells per mL on PCBs) with a shorter culturing time (30 d on PCE vs. 150 d on PCBs). The transcriptomic profiles illustrated that the distinct PCB dechlorination profile of each strain was predominantly mediated by a single, novel reductive dehalogenase (RDase) catalyzing chlorine removal from both PCBs and PCE. The transcription levels of PCB-RDase genes are 5-60 times higher than the genome-wide average. The cultivation of PCB-respiring Dehalococcoides in pure culture and the identification of PCB-RDase genes deepen our understanding of organohalide respiration of PCBs and shed light on in situ PCB bioremediation.

Identification of peptide inhibitors of penicillinase using a phage display library.

There is a constant need to identify novel inhibitors to combat ß-lactamase-mediated antibiotic resistance. In this study, we identify three penicillinase-binding peptides, P1 (DHIHRSYRGEFD), P2 (NIYTTPWGSNWS), and P3 (SHSLPASADLRR), using a phage display library. Surface plasmon resonance (SPR) is utilized for quantitative determination and comparison of the binding specificity of selected peptides to penicillinase. An SPR biosensor functionalized with P3-GGGC (SHSLPASADLRRGGGC) is developed for detection of penicillinase with excellent sensitivity (15.8 RU nM(-1)) and binding affinity (KD = 0.56 nM). To determine if peptides can be good inhibitors for penicillinase, these peptides are mixed with penicillinase and their inhibition efficiency is determined by measuring the hydrolysis of substrate penicillin G using UV-vis spectrophotometry. Peptide P2 (NIYTTPWGSNWS) is found to be a promising penicillinase inhibitor with a Ki of 9.22 µM and a Ki' of 33.12 µM, suggesting that the inhibition mechanism is a mixed pattern. This peptide inhibitor (P2) can be used as a lead compound to identify more potent small molecule inhibitors for penicillinase. This study offers a potential approach to both detection of ß-lactamases and development of novel inhibitors of ß-lactamases.

Quantitative serine protease assays based on formation of copper(II)-oligopeptide complexes.

A quantitative protease assay based on the formation of a copper-oligopeptide complex is developed. In this assay, when a tripeptide GGH fragment is cleaved from an oligopeptide chain by serine proteases, the tripeptide quickly forms a pink GGH/Cu(2+) complex whose concentration can be determined quantitatively by using UV-Vis spectroscopy. Therefore, activities of serine proteases can be determined from the formation rate of the GGH/Cu(2+) complex. This principle can be used to detect the presence of serine protease in a real-time manner, or measure proteolytic activities of serine protease cleaving different oligopeptide substrates. For example, by using this assay, we demonstrate that trypsin, a model serine protease, is able to cleave two oligopeptides GGGGKGGH () and GGGGRGGH (). However, the specificity constant (kcat/Km) for is higher than that of (6.4 × 10(3) mM(-1) min(-1)vs. 1.3 × 10(3) mM(-1) min(-1)). This result shows that trypsin is more specific toward arginine (R) than lysine (K) in the oligopeptide sequence.

DNA microarrays on ultraviolet-modified surfaces for speciation of bacteria.

In this study, we report an approach to activate inert hydrocarbon monolayers with ultraviolet (UV) light to fabricate DNA microarrays. Unlike traditional microarrays that require reactive functional groups on the surface, our DNA microarray is built on an inert layer of N,N-dimethyl-N-octadecyl(3-aminopropyl)trimethoxysilyl chloride silane (DMOAP). This layer is activated by UV (254 nm) just prior to the immobilization of oligonucleotide probes. Our X-ray photoelectron spectroscopy (XPS) results show that new functional groups such as alcohol (C--O), aldehyde (C=O), and carboxylic acid (O--C=O) form on the surface after the UV exposure. Among them, aldehyde groups are responsible for the immobilization of amine-label oligonucleotides. By using this approach, we further optimize UV exposure time and oligonucleotide concentration and also reduce agent concentration to achieve a high density of immobilized oligonucleotides up to 0.16 pmol/mm². As a proof of concept, we demonstrate that this microarray can be used for differentiation of different Clostridium species such as Clostridium acetobutylicum, Clostridium butylicum, and Clostridium beijerinkii.

Isolation and characterization of a novel Dehalobacter species strain TCP1 that reductively dechlorinates 2,4,6-trichlorophenol.

Chlorophenols are widely used as biocides, leading them to being prevalent environmental contaminants that pose toxic threats to ecosystems. In this study, a Dehalobacter species strain TCP1 was isolated from a digester sludge sample, which is able to dechlorinate 2,4,6-trichlorophenol (2,4,6-TCP) to 4-monochlorophenol (4-MCP) with H2 as the sole electron donor and acetate as the carbon source. Strain TCP1 also distinguishes itself from other Dehalobacter species with its capability to dechlorinate tetrachloroethene or trichloroethene (TCE) to both cis- and trans-dichloroethenes in a ratio of 5.6 (±0.2):1. The growth yields of strain TCP1 on TCE and 2,4,6-TCP were 4.14 × 10(13) and 5.77 × 10(13) cells mol(-1) of Cl(-) released, respectively. Strain TCP1 contains five unusually long 16S rRNA gene copies per genome, and the extra length is due to the ~110 bp insertion sequences at their 5'-ends. This suggests that strain TCP1 may represent a novel Dehalobacter species. A putative chlorophenol reductive dehalogenase gene-debcprA-was identified to catalyze the ortho-chlorine removal from 2,4,6-TCP. Both the culture-dependent and housekeeping rpoB gene-based approaches indicate the purity of the culture. Strain TCP1 can serve as a promising candidate for the bioremediation of 2,4,6-TCP contaminated sites, and its discovery expands our understanding of metabolic capabilities of Dehalobacter species.

Using medaka embryos as a model system to study biological effects of the electromagnetic fields on development and behavior.

The electromagnetic fields (EMFs) of anthropogenic origin are ubiquitous in our environments. The health hazard of extremely low frequency and radiofrequency EMFs has been investigated for decades, but evidence remains inconclusive, and animal studies are urgently needed to resolve the controversies regarding developmental toxicity of EMFs. Furthermore, as undersea cables and technological devices are increasingly used, the lack of information regarding the health risk of EMFs to aquatic organisms needs to be addressed. Medaka embryos (Oryzias latipes) have been a useful tool to study developmental toxicity in vivo due to their optical transparency. Here we explored the feasibility of using medaka embryos as a model system to study biological effects of EMFs on development. We also used a white preference test to investigate behavioral consequences of the EMF developmental toxicity. Newly fertilized embryos were randomly assigned to four groups that were exposed to an EMF with 3.2kHz at the intensity of 0.12, 15, 25, or 60µT. The group exposed to the background 0.12µT served as the control. The embryos were exposed continually until hatch. They were observed daily, and the images were recorded for analysis of several developmental endpoints. Four days after hatching, the hatchlings were tested with the white preference test for their anxiety-like behavior. The results showed that embryos exposed to all three levels of the EMF developed significantly faster. The endpoints affected included the number of somites, eye width and length, eye pigmentation density, midbrain width, head growth, and the day to hatch. In addition, the group exposed to the EMF at 60µT exhibited significantly higher levels of anxiety-like behavior than the other groups did. In conclusion, the EMF tested in this study accelerated embryonic development and heightened anxiety-like behavior. Our results also demonstrate that the medaka embryo is a sensitive and cost-efficient in vivo model system to study developmental toxicity of EMFs.

[Transperitoneal laparoscopic ureteral reimplantation with extracorporeal tailoring and direct nipple ureteroneocystostomy for adult obstructive megaureter].

This paper focuses on a novel modified technique about the treatment of adult obstructed megaureter by the transperitoneal laparoscopic procedure. With the improvement of the laparoscopic surgery, many urological surgeries can be safely and effectually performed by laparoscopic approach. The previously reported laparoscopic methods for treatment of adult obstructed megaureter were complex and time-consuming. To simplify the method, we modified the laparoscopic approach based on the previous methods. The innovative points of our novel technique are the extracorporeal tailoring of ureter and nipple ureteroneocystostomy. By this modified procedure, the time of operation can be obviously reduced while the procedure is effective. We hope this modified procedure will be accepted by more urologists.

Amperometry for real-time and on-site monitoring of phenol and H2O2 during the treatments.

In conventional wastewater treatment processes, a predetermined quantity of chemicals is introduced at the onset, without ongoing monitoring of the treatment progress. Thus, it is difficult to perform timely intervention in the treatment process. Herein, we develop an amperometry-guided wastewater treatment strategy based on a green oxidation process with H2O2 and an iron-tetraamidomacrocyclic ligand (Fe-TAML) catalyst. During the process, users can monitor both phenol and H2O2 concentrations in real time and then intervene by adding more H2O2 to accelerate the reaction. As a proof of concept, a wastewater sample containing 9.3 ppm of phenol is treated by using the amperometry-guided strategy with 1 dosage of Fe-TAML (0.45 ppm) and 3 dosages of H2O2 (1.86 ppm). After the treatment, phenol concentration in the wastewater decreases to 0 ppm after 21 min. In contrast, with only 1 dosage of Fe-TAML (0.45 ppm) and 1 dosage of H2O2 (1.86 ppm), the reaction slows down after 5 min and stops prematurely. After that, the reaction kinetics of ppb-level phenol are investigated, in which the phenol rate and the rate constant are estimated. Compared to conventional detections, the designed amperometry shows faster response, lower limit of detection (LOD, phenol: 11 ppb, H2O2: 80 ppb) and consumable cost, easier operation, and no pollution generated. This example demonstrates the importance of early intervention during wastewater treatment with the help of real-time information.

Highly efficient treatment of tetracycline using coupled electro-Fenton and electrocoagulation process: Mechanism and toxicity assessment.

In this study, a novel carbon fiber brush (CFB) electrode was designed using carbon fiber filaments and conductive metals. It was used as the cathode to construct an efficient coupled electro-Fenton and electrocoagulation (EF-EC) process for tetracycline (TC) treatment. An optimal 97.9% removal rate of 10 mg L-1 TC was achieved within 20 min. The coupled process is less pH-dependent and more effective in treating TC compared to the traditional individual electro-Fenton (EF) or electrocoagulation (EC) process, achieving efficient TC removal under neutral pH conditions. The removal rate of 10 mg L-1 TC consistently remained above 92% at 20 min after ten cycle experiments using the same electrodes in a Fe-CFB system (92.7-97.9%), indicating excellent reusability and stability of the CFB cathode. Mechanism analysis showed both EF and EC processes were involved in the system. Radicals (such as •OH and SO4-•) generated by EF contributed to the degradation of TC, yielding nine intermediates. Coagulants (such as Fe(OH)3) generated by EC contributed to the removal of TC. Toxicity prediction results indicated that over half of the nine intermediates exhibited lower biotoxicity compared to TC. This study provides a feasible alternative cathode for the efficient treatment of TC using EF-EC process.

A novel strategy for enhancing the stability of aptamer conformations in heavy metal ion detection.

BACKGROUND: Detection methods based on aptamer probes have great potential and progress in the field of rapid detection of heavy metal ions. However, the unstable conformation of aptamers often results in poor sensitivity due to the dissociation of aptamer-target complex in real environments. RESULTS: In this study, we developed a locking aptamer probe and combined it with AgInZnS quantum dots for the first time to detect cadmium ions. When cadmium ions are combined with the probe, the cadmium ions are fixed in the core-locking position, forming a stable cavity structure. The limit of detection (LOD) was achieved at a concentration of 6.9 nmol L-1, with a broad detection range from 10 nmol L-1 to 1000 µmol L-1, and good recovery rates (92.93%-102.8 %) were achieved in aquatic product testing. The locking aptamer probe with stable conformation effectively enhances the stability of the aptamer-target complex and remains good stability in four buffer environments as well as a 600 mmol L-1 salt solution; it also exhibits good stability at pH 6.5-7.5 and temperatures ranging from 25 °C to 35 °C. SIGNIFICANCE: Overall, our study presented a general, simple, and cost-effective strategy for stabilizing aptamer conformations, and used for highly sensitive detection of cadmium ions.