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Alzheimer's disease (AD) is a degenerative disease of the central nervous system. The pathogenesis is still not fully clear. One of the main histopathological manifestations is senile plaques formed by β-amyloid (Aβ) accumulation. Aβ is generated from the sequential proteolysis of amyloid precursor protein (APP) by β-secretase [i.e. β-site APP cleaving enzyme 1 (BACE1)] and γ-secretase, with a rate-limiting step controlled by BACE1 activity. Therefore, inhibiting BACE1 activity has become a potential therapeutic strategy for AD. The development of reliable detection methods for BACE1 activity plays an important role in early diagnosis of AD and evaluation of the therapeutic effect of new drugs for AD. This article has reviewed the recent advances in BACE1 activity detection techniques. The challenges of applying these analysis techniques to early clinical diagnosis of AD and development trends of the detection techniques have been prospected.

Brain pH has been proven to be a key factor in maintaining normal brain function. The relationship between local pH fluctuation and brain disease has not been extensively studied due to lack of the accurate in situ analysis technology. Herein, we have for the first time proposed a voltammetric pH sensor by measuring the ratio of current signals instead of the previously reported potential based on the Nernst equation. Single-walled carbon nanotubes (CNT) were first self-assembled on the electrode surface of a carbon-fiber nanotip electrode (CFNE). Then, poly-o-phenylenediamine (PoPD) molecules were deposited as pH-responsive molecules through in situ electrochemical polymerization. The compact CFNE/CNT/PoPD exhibited a good redox process with the on-off-on ratiometric electrochemical response to pH ranging from 4.5 to 8.2, providing self-correction for in situ pH detection. Thus, the proposed sensor enabled the accurate measurement of pH with excellent selectivity even in the presence of proteins or electroactive species. In addition, the sensor showed high repeatability, reproducibility, and reversibility in measuring pH and even demonstrated good stability when it was exposed to air for 5 months. Finally, we successfully detected the fluctuation of pH in rat brains with cerebral ischemia and rat whole blood. Overall, this research not only provides a good tool for the detection of rat brain pH but also provides a new strategy for further designing nanosensors for intracellular or subcellular pH.

Accurate detection of hydrogen sulfide (H2S) is of great significance for environmental monitoring and protection. We propose a colorimetric method for the detection of H2S by the use of mixed-node Cu-Fe metal organic frameworks (Cu-Fe MOFs) as highly efficient mimic enzymes for target-induced deactivation. The Cu-Fe MOFs were synthesized by a simple solvothermal method and could catalyze the H2O2 mediated oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to oxTMB with a blue color. The presence of dissolved H2S would deactivate the mimic enzymes, and then the blue color disappeared. The mechanism of the sensor was discussed by steady-state kinetic analysis. The designed assay was highly sensitive for H2S detection with a linear range of 0−80 μmol/L and a detection limit of 1.6 μmol/L. Moreover, some potential substances in the water samples had no interference. This method with the advantages of low cost, high sensitivity, selectivity, and visual readout with the naked eye was successfully applied to the determination of H2S in industrial wastewater samples.

In this study, we developed an effective method to detect hypochlorite acid (HClO) by using methylene blue (MB) derivative (BPY1). BPY1 was selectively oxidized through HClO, and the solution color changed from colorless to blue. In the presence of HClO, the ultraviolet–visible (UV–vis) spectra and concentration of HClO had a linear relationship with a detection limit of 0.5 μM. Furthermore, a test paper for HClO monitoring was successfully prepared using the BPY1 probe, and the observed detection limit by the naked eye was estimated at 5 μM. Additionally, using the BPY1 probe, HClO could also be detected through smartphone colorimetry, and the method showed a good recovery ranging from 98.7 to 104.0% for HClO detection in an actual water sample. Especially for developing countries, such a low-cost and highly sensitive detection method provides a simple and practical method for monitoring HClO in water.

As a vital gaseous signal molecule involved in various physiological and pathological processes, nitric oxide (NO) has attracted extensive attention in the last few decades. In this work, a copper and cobalt element-doped, biphenyl-(3, 4', 5)-tricarboxylic acid (H

White-light emitting lanthanide(iii) metal-organic coordination polymers (LMOCPs) were prepared via a green synthesis method performed in pure aqueous solution at room temperature without using toxic solvent and reagents. This kind of LMOCP, denoted as adenosine monophosphate (AMP)/Ln-CIP, was composed of Ln3+ {Ln = Tb (1), Eu (2), and Gd (3)}, hydrosoluble biomolecule of AMP, and nonpoisonous antenna ligand of CIP (ciprofloxacin). The complex of Tb(1), Eu(2), and Gd(3) in AMP/Ln-CIP emits strong green, red, and blue light, respectively. With careful adjustment of the doping mole ratio of the three lanthanide ions {Ln = Tb:Eu:Gd = 0.1:0.9:99.0} in one framework, white light-emission can indeed be achieved. AMP/Ln-CIP is network-structural and amorphous by transmission electron microscope and X-ray diffraction analysis. The fluorescence lifetime and quantum yield of AMP/Ln-CIP are 4.36 ms and 36.5%, respectively.

Metal organic frameworks (MOFs) used to effective immobilization of enzymes was generally thought as an efficient and economical method to enhance the activity and stability of enzymes and improve their reusability. Here we report a solvent-free approach to prepare Fe3O4-embedded zeolite imidazolate framework-8 (ZIF-8) composite. The embedment of Fe3O4 was successfully accomplished during the crystal growth process of ZIF-8 through solid reaction, exhibiting high lipase loading about 95.5 mg/g. To improve catalytic efficiency for water-insoluble substrate, the Fe3O4@ZIF-8@lipase with an appropriate water contact angel (θow) was explored as a stabilizer of Pickering emulsion on the oil/water interface. Then a Pickering emulsion was quickly formed for controllable hydrolysis based on interfacial activation of lipase through the magnetic-responsive bionanoparticles with high surface activity and biocompatibility. In this interfacial biocatalytic system, Fe3O4@ZIF-8@lipase showed 2.48 times higher catalytic efficiency than free lipase and strong tolerance for organic media. Therefore, simple preparation and versatile catalysis endow this system potential application for realizing the biocatalysis of typical organic syntheses and the revolution of production.

Rapid, simple, accurate and highly sensitive detection of enzymes is essential for early screening and clinical diagnosis of many diseases. In this study, we report the fabrication of a turn-on ratiometric electrochemical sensor for the in situ determination of β-Galactosidase (β-Gal) based on surface engineering and the design of a molecular probe (Pygal) specific for β-Gal recognition. First, Pygal probe was synthesized and characterized, and then co-assembled with the methylene blue (MB) internal reference probe on the surface of single-wall carbon nanotubes (SWCNT)-modified carbon fiber microelectrode (CFME). The resulting CFME/SWCNT/MB + Pygal sensor is activated in the presence of β-Gal giving one peak at 0.33 V originating from the oxidation of the product of Pygal enzymatic hydrolysis (PyOH). Another oxidation peak attributed to MB appears simultaneously at -0.28 V allowing the construction of a ratiometric electrochemical sensor for β-Gal detection with improved sensitivity and accuracy. The sensor showed a linear response to β-Gal in a wide concentration range from 1.5 to 30 U L

Nitric oxide is one of the atmospheric pollutants and an important gas messenger molecule in the human body, involved in many physiological and pathological processes. Therefore, detecting nitric oxide rapidly and accurately has been one of the popular topics in recent decades. In this study, we synthesized CuCo-PTC MOF materials using a solvothermal method based on the mechanism of triazole ring formation from o-phenylenediamine (OPD) and nitric oxide. The synthesized CuCo-PTC MOF materials show high sensitivity and good selectivity for detecting nitric oxide in vitro and in cell lysates. The results indicate the potential for applying this sensing strategy to detect nitric oxide in the internal environment.

Small-molecule photosensitizers have great application prospects in photoelectrochemical (PEC) sensing due to their defined composition, diversified structure, and adjustable photophysical properties. Herein, we propose a new strategy for PEC analysis based on the target-induced in situ formation of the organic photosensitizer. Taking thiophenol (PhSH) as a model analyte, we designed and synthesized a 2,4-dinitrophenyl (DNP)-caged coumarin precursor (Dye-PhSH), which was then covalently coupled onto the TiO

Interferon-gamma (IFN-γ) is one kind of crucial inflammatory cytokines, and its expression level is closely associated with various disease progressions. This work addresses the development of a sensitive and specific electrochemical assay for detection of IFN-γ by combing the recognition unit of aptamer with the signal reporter of target-induced silver nanoclusters (AgNCs). For biosensor preparation, the gold nanoparticles (AuNPs) immobilized on the amine-terminated electrode surface provided electrochemical interfaces for the self-assembly of C-rich modified aptamers. Then, the aptamer recognized IFN-γ and the free aptamer hybridized with conjugated DNA sequences. After the nuclease-catalyzed cleavage of DNA duplex, in situ-generated AgNCs in the C-rich template was utilized as the electrochemical indicator for IFN-γ detection. The present method demonstrated a good performance for detection of IFN-γ with a low detection limit of 1.7 pg mL

Dipeptidyl peptidase IV (DPP-IV) is a transmembrane glycoprotein known to regulate T cell activation, which is related to various pathological processes and has become a potential target to treat type 2 diabetes mellitus. Therefore, it is significant for the evaluation of endogenous DPP-IV activity in various biological systems. Herein, a water-soluble near-infrared (NIR) fluorescent probe HCA-D based on cyanine dyes as the fluorophore and glycyl-prolyl peptide as the specific recognition sequence was developed for the assay of dipeptidyl peptidase IV (DPP-IV) activity. Upon addition of DPP-IV, HCA-D can emit a significant turn-on NIR fluorescence signal under physiological conditions and exhibit high selectivity toward DPP-IV. This feature was available for quantifying DPP-IV in the range from 0.62 to 10 ng mL-1 with a detection limit of 0.19 ng mL-1. Furthermore, the present probe was successfully employed for monitoring DPP-IV in serum samples from diabetic and healthy people, and imaging of DPP-IV in living cells and tumor mice models. These results demonstrate that the designed probe provides a promising tool to explore the relationship between DPP-IV and diabetes mellitus or other diseases. Perhaps, it may become a prospective image-guided tumor resection indicator based on the abnormal expression of DPP-IV activity in the future.

Herein, we present the synthesis and electrochemiluminescence (ECL) sensing applications of the Au-Co/GO nanocomposite. Au-Co/GO nanocomposite was prepared for the first time by decorating graphene oxide (GO) with alloy-structured Au-Co bimetallic nanoparticles (BNPs) via one-step on site chemical reduction. The obtained nanocomposite was comprehensively characterized and the results showed that alloy-structured Au-Co nanoparticles (NPs) have an average size of 4 nm and are highly dispersed on GO layers. ECL measurement revealed that the as-synthesized Au-Co/GO nanocomposite displays a synergistic effect of the GO and the Au-Co BNPs on luminol-H2O2 ECL signal. Further immobilization of glucose oxidase (GOD) onto the Au-Co/GO modified electrode afforded a effective ECL glucose sensor which displayed a dynamic range of 1–100 µM with a satisfactory detection limit of 0.18 μM. Furthermore, the developed enzymatic sensors were successfully applied for monitoring glucose in real human samples.

Redox homeostasis between hypochlorous acid (HClO/ClO-) and ascorbic acid (AA) significantly impacts many physiological and pathological processes. Herein, we report a new electrochemical sensor for the simultaneous determination of HClO and AA in body fluids. We first coated a carbon fiber microelectrode (CFME) with a three-dimensional nanocomposite consisting of graphene oxide (GO) and carbon nanotubes (CNTs) to fabricate the CFME/GO-CNT electrode. After the electrochemical reduction of GO (ERGO), we integrated a latent 1-(3,7-bis(dimethylamino)-10H-phenothiazin-10-yl)-2-methylpropan-1-one (MBS) electrochemical molecular recognition probe to monitor HClO and employed anthraquinone (AQ) as an internal reference. The compact CFME/ERGO-CNT/AQ + MBS sensor enabled the accurate and simultaneous measurement of HClO and AA with excellent selectivity and sensitivity. Measurements were highly reproducible, and the sensor was stable and exceptionally biocompatible. We successfully detected changes in the redox cycles of HClO and AA in human body fluids. This sensor is a significant advance for the investigation of reactions involved in cellular redox regulation. More importantly, we have devised a strategy for the design and construction of ratiometric electrochemical biosensors for the simultaneous determination of various bioactive species.

Photodynamic therapy (PDT) is a promising and minimally invasive modality for the treatment of cancers. The use of a self-illuminating system as a light source provides an intriguing solution to the light penetration issues of conventional PDT, which have gained considerable research interest in the past few years. This mini review aimed to present an overview of self-illuminating PDT systems by using internal light sources (chemiluminescence, bioluminescence, and Cerenkov radiation) and to give a brief discussion on the current challenges and future perspectives.

In this work, a turn-on near-infrared fluorescent probe, hemicyanine derivative (CyB), for the highly selective and sensitive detection of chymotrypsin was developed. The probe is fabricated by incorporating a recognition group of 4-bromobutyryl into the hemicyanine skeleton. Upon the nucleophilic substitution reaction of chymotrypsin and the probe, the probe displayed a remarkable fluorescence enhancement and a visible color change under natural light. This property can be utilized for the detection of chymotrypsin with a detection limit (LOD) of 0.013 U mL−1. Moreover, the cell and in vivo imaging experiments validated that this probe has the potential ability to detect chymotrypsin in biological systems and can provide a promising application prospect for screening chymotrypsin inhibitors.

Oxidative stress plays an important role in the pathogenesis of many diseases, while the exact mechanism that hydrogen peroxide (H

A strategy for amplifying the signal of surface plasmon resonance (SPR) biosensors is reported. Biotinylated phenylalanine (Biotin-Phe) monomers were rapidly self-assembled into nanoparticles in a mild environment. The self-assembled nanoparticles were then used as the carriers of streptavidin-antibody complexes by the streptavidin-biotin interaction. The signal was amplified because of the high molecular weight of the nanoparticle-streptavidin-antibody conjugate. With prostate-specific antigen as a model analyte, the target concentration as low as 1 pg mL−1 was readily measured. The results of the nanoparticle-enhanced SPR biosensor for analysis of serum samples are well consistent with those achieved by the enzyme-linked immunosorbent assays. This work is valuable for designing of various optical and electronic biosensors through the streptavidin-biotin interaction.

Insulin, a peptide hormone secreted by pancreatic β cells, affects the development of diabetes and associated complications. Herein, we propose an electrochemical aptasensor for sensitive and selective detection of insulin using laser-scribed graphene electrodes (LSGEs). Before using disposable LSGEs, the development and proof-of-concept sensing experiments were firstly carried out on research-grade glassy carbon electrode (GCE). The aptasensor is based on using Exonuclease I (Exo I) that catalyses the hydrolysis of single-stranded aptamers attached to the electrode surface; however, the hydrolysis does not occur if the insulin is bound to the aptamer. Therefore, the unbound aptamers are cleaved by Exo I while insulin-bound aptamers remain on the electrode surface. In the next step, the gold nanoparticle - aptamer (AuNPs-Apt) probes are introduced to the electrode surface to form a 'sandwich' structure with the insulin on the surface-attached aptamer. The redox probe, methylene blue (MB), intercalates into the aptamers' guanine bases and the sandwich structure of AuNPs-Apt/insulin/surface-bound aptamer amplifies electrochemical signal from MBs. The signal can be well-correlated to the concentrations of insulin. A limit of detection of 22.7 fM was found for the LSGE-based sensors and 9.8 fM for GCE-based sensors used for comparison and initial sensor development. The results demonstrate successful fabrication of the single-use and sensitive LSGEs-based sensors for insulin detection.

Herein, a label-free electrochemiluminescence (ECL) biosensor for sensitive determination of carcinoembryonic antigen (CEA) was fabricated based on metal organic framework enriched CdS quantum dots (CdS QDs@MOF) and triethanolamine-modified gold nanoparticles (TEOA@AuNPs) as bi-coreactants of Ru(bpy)32+ ECL system. The TEOA@AuNPs served as not only coreactant of Ru(bpy)32+ but also nanocarrier for CEA aptamer which was bonded to the TEOA@AuNPs through Au−S bond. After incubated in CEA solution, the ECL signals decreased due to the poor conductivity of CEA and there was a linear correlation between the ECL intensity and log(CCEA). Based on this result, a label-free ECL biosensor has been developed successfully and used to detect CEA with a detection limit of 85 fg/mL. The proposed ECL aptasensor had good analytical performance in the detection of CEA in human serum samples.

Hypochlorous acid (HOCl) is one of the most potent reactive oxygen species and plays a vital role in many biological processes. Chemical probes for HOCl have proven to be valuable tools in understanding its contributions to healthy and disease states. Herein, a new ratiometric fluorescent probe (1), which composed of a coumarin scaffold bearing a phenothiazine moiety as the electron-donating group and a pyridine unit as the electron-accepting group, was rationally designed and synthesized for sensing HOCl. Probe 1 exhibited a distinct deep-red emission (∼630 nm), while displayed a completely different emission in the cyan region (∼500 nm) upon the addition of HOCl, thereby allowing the ratiometric detection of HOCl without spectral crosstalk interference. In addition, the presented probe has several other advantages for HOCl detection, including rapid response, high signal to noise ratio, excellent selectivity and sensitivity. Furthermore, the probe has shown the utility for visualizing HOCl in cells and organisms.

A novel strategy was proposed for the construction of photoelectrochemical (PEC) sensing platform based on multifunctional photosensitizer which can simultaneously achieve photo-sensitization, target-recognition and interface conjugation. Herein, N3 dye, bis(4,4′-dicarboxy-2,2′-bipyrid ine) dithiocyanato ruthenium (II), was employed as a model multifunctional molecule and covalently tethered on amino-functionalized TiO2 nanowires. The obtained photoanode can produce a sensitive photocurrent response towards Hg2+ under visible illumination (∼540 nm). The decrease in photocurrent can be attributed the larger HOMO-LUMO gap, the higher LUMO energy level and the reduced electron cloud density of N3–Hg2+ complex compared with the free N3 dye, which is demonstrated by DFT calculations. Under optimized conditions, the PEC assay displayed a linear dynamic range of 0.5–50 μM for Hg2+ with a detection limit of 0.13 nM. Moreover, the long-term stability of the PEC sensor was achieved due to the covalent conjugation of the photosensitizer to the TiO2 nanowire. The proposed sensing strategy, by utilizing the multifunctional molecule photosensitizers for direct responding to targets, presents a novel methodology for the development of high performance PEC sensors in future.

In this work, a gold nanoparticle-based label-free homogeneous phase colorimetric bioassay was developed for the detection of Aβ1–40 oligomers (AβO), important biomarkers for diagnosis and monitoring progression of Alzheimer's disease (AD). The prepared AβO-aptamer decorated AuNPs tended to aggregate in a solution with high concentrations of salt, and displayed a purple color with a maximum absorption peak at 650 nm, a characteristic absorption of aggregated AuNPs. In the presence of AβO, the specific binding of the target with the aptamer generated folded aptamer structures, which can stabilize AuNPs towards the salt-induced aggregation more effectively than AuNPs stabilized by the aptamer alone, and thus achieved a hypsochromic shift in the absorption spectra. On the basis of this sensitive spectral transformation, the proposed aptasensor was successfully applied for the detection of AβO with a dynamic range of 1–600 nM and a low detection limit of 0.56 nM. The reliability and practicality of this aptasensor was demonstrated by analysis of AβO in artificial cerebrospinal fluid (aCSF). We anticipate that the proposed facile colorimetric assay for AβO will provide applicable information for early diagnosis of AD.

A new naphthalimide-based probe was designed and synthesized for the rationmetric detection of hydrazine. The probe is designed in such a way that the intramolecular charge transfer (ICT) of the 4-hydroxynaphthalimide was masked by the 4-bromobutyrate moiety, and the selective deprotection of the 4-bromobutyrate group of the probe by hydrazine through a substitution-cyclisation-elimination process results in the recovery of the ICT of 4-hydroxynaphthalimide. Thus the probe can realize both colorimetric and fluorimetric detection of hydrazine in a ratiometric manner. The probe is highly selective toward hydrazine over other abundant interferences. The LOD (limit of detection) of the probe for N 2 H 4 was calculated to be 0.27 μM which is well below the safety level (10 ppb, 0.31 μM) set by EPA. Notable, the probe loaded thin-layer-chromatography (TLC) plate could be successfully used to detect gaseous hydrazine. Moreover, the cell imaging studies demonstrated that the probe can be exploited to detect hydrazine in biological systems.

A novel magnetic organic porous polymer (denoted as Fe3O4@PC-POP) was developed for magnetic solid-phase extraction (MSPE) of two gastric cancer biomarkers (P-cresol and 4-hydroxybenzoic acid) from urine samples prior to high-performance liquid chromatographic analysis. The adsorbent was characterized by scanning electron microscope, transmission electron microscope, FTIR, powder X-ray diffraction, and other techniques. The result of dynamic light scattering shows that the particle size of the adsorbent is mainly distributed around 400 nm. Based on the design concept of the Fe3O4@PC-POP, the proposed material can effectively capture the target analytes through electrostatic and hydrophobic interaction mechanism. Furthermore, the enrichment conditions were optimized by the response surface method, and the method was utilized for the determination of P-cresol and 4-hydroxybenzoic acid in real urine samples from health and gastric cancer patients with high enrichment factors (34.8 times for P-cresol and 38.7 times for 4-hydroxybenzoic acid), low limit of detection (0.9–5.0 μg L−1), wide linear ranges (3.0–1000 μg L−1), satisfactory relative standard deviation (2.5%–8.5%), and apparent recoveries (85.3–112% for healthy people’s and 86.0–112% for gastric cancer patients’ urine samples). This study provides a guided principle for design of the versatile polymer with specific capturing of the target compounds from complex biological samples.

Thiophenol (PhSH) is an important sulfhydryl compound in organic synthesis, but it is also a volatile environmental pollutant with high toxicity to organisms. Herein, we reported a novel near-infrared (NIR) probe (1) for turn-on fluorescence detection of PhSH. The probe was prepared by coupling 2,4-dinitrophenyl (DNP) to a dicyanoisophorone-based fluorophore (2). PhSH can specifically perform a nucleophilic aromatic substitution on probe 1 and result in the release of fluorophore 2, thus achieving a turn-on fluorescence response (λem = 693 nm). A dramatic color change from red (λabs = 525 nm) to blue (λabs = 668 nm) was also observed. This fluorescent assay displayed a large Stokes shift (∼133 nm) and a high sensitivity for PhSH, as well as a low detection limit (34 nM). Moreover, probe 1 was successfully applied to monitor PhSH in real water samples and image PhSH in living cells.

Thiophenol (PhSH) belongs to a class of highly reactive and toxic aromatic thiols with widespread applications in the chemical industry for preparing pesticides, polymers, and pharmaceuticals. In this review, we comprehensively summarize recent progress in the development of fluorescent probes for detecting and imaging PhSH. These probes are classified according to recognition moieties and are detailed on the basis of their structures and sensing performances. In addition, prospects for future research are also discussed.

DNA 3'-phosphatase is an essential enzyme, which plays a pivotal role in repairing DNA damage. The peculiar activity of DNA 3'-phosphatase has been proved to associate with a variety of human pathologies. Therefore, sensitive determination of DNA 3'-phosphatase is necessary for clinical diagnosis and therapy. Here, we develop a simple, sensitive, and specific fluorescent biosensor including three DNA chains of hairpin DNA1, hairpin DNA2 and fluorescence probe DNA (FP) for detecting the activity of DNA 3'-phosphatase. First, biotin-modified hairpin DNA1 binds with streptavidin-modified magnetic beads (MB) to get MB-DNA1. DNA 3'-phosphatase can hydrolyze phosphate groups on MB-DNA1 to form hydroxyl groups, which leads to the polymerization extension and nicking endonuclease cleavage reaction to obtain the trigger DNA1 fragment (tDNA1). Next, two cyclic amplification reactions are designed. In cycle I, the tDNA1 hybridizes with the hairpin DNA2, which leads the hairpin structure of DNA2 opened and the fluorescence signal of 6-carboxy-fluorescein (FAM) labeled on hairpin DNA2 turned on. This cyclic reaction is amplified by exonuclease III (Exo III). At the same time, the trigger DNA2 fragment (tDNA2) is obtained. In cycle II, similarly, the tDNA2 hybridizes with FP. Thus, the fluorescence signal of FAM labeled on FP released, which multiplies with the fluorescence signal from cycle I. Finally, this strategy is applied to determine two typical DNA 3'-phosphatases including T4 polynucleotide kinase (T4 PNK) and alkaline phosphatase (ALP) with the detection limit (LOD) of 0.0033 and 0.00037 U/mL, respectively. The method provides a promising platform to evaluate the DNA 3'-phosphatase activity in the complicated biological samples and can be potentially applied in the relevant fields such as biomedical research, drug discovery and clinical diagnosis.

We investigate the deformation dynamics in pre-twinned Mg-3Al-1Zn alloy under uniaxial compression based on in situ synchrotron X-ray diagnostics. Stress-strain curves, strain field mapping and X-ray diffraction are achieved simultaneously. The same measurements are conducted on the as-received Mg alloy for comparison. Massive { 1 0 1 ¯ 2 } – { 1 0 1 ¯ 2 } double twinning is observed in preexisting twins of the pre-twinned specimen, and abundant { 1 0 1 ¯ 2 } extension twins are activated in the as-received specimen. The { 1 0 1 ¯ 2 } extension twinning in the as-received specimen can rapidly boost strain hardening rate by slowing down the process of strain localization. The { 1 0 1 ¯ 2 } – { 1 0 1 ¯ 2 } double twinning does not lead to significant reduction in the rate of strain localization, and thus the corresponding increase in strain hardening rate is modest.