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Recently, solution-based surface-enhanced Raman scattering (SERS) detection technique has been widely recognized due to its cost-effectiveness, simplicity, and ease of use. However, solution-based SERS is limited for practical applications mainly because of the weak adsorption affinity of the target biomolecules to the surface of plasmonic nanoparticles. Herein, we developed a highly sensitive solution-based SERS sensing platform based on mercaptopropionic acid (MPA)-capped silver-coated gold nanostars (SGNS@MPA), which allows efficient enrichment on the nanostars surface for improved detection of an analyte: creatinine, a potential biomarker of chronic kidney disease (CKD). The SGNS@MPA exhibited high enrichment ability towards creatinine molecules in alkaline medium (pH-9) through multiple hydrogen bonding interaction, which causes aggregation of the nanoparticles and enhances the SERS signal of creatinine. The detection limit for creatinine was achieved at 0.1 nM, with a limit of detection (LOD) value of 14.6 pM. As a proof-of-concept demonstration, we conducted the first quantitative detection of creatinine in noninvasive human fluids, such as saliva and sweat, under separation-free conditions. We achieved a detection limit of up to 1 nM for both saliva and sweat, with LOD values as low as 0.136 nM for saliva and 0.266 nM for sweat. Overall, our molecular enrichment strategy offers a new way to improve the solution-based SERS detection technique for real-world practical applications in point-of-care settings and low-resource settings., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

This study explores the principles of resonance energy transfer and adsorption modulation using composites of Cu 2 S-MPA/NGODs. These composites can efficiently control the quenching process of electrochemiluminescence (ECL). Mercaptopropionic acid (MPA) was added during the synthesis of Cu 2 S-MPA to enhance its attachment to nitrogen-doped graphene quantum dots (NGODs). The UV absorption peaks of NGODs coincided with the emission peaks of luminol ECL, enabling resonance energy transfer and enhancing the quenching capability of Cu 2 S-MPA. Meanwhile, there is another quenching strategy. When the readily reducible Cu + ions underwent partial reduction to Cu when they were bound to NGODs. This weakened the electrocatalytic effect on reactive oxygen species (ROS) and had a detrimental impact on electron transfer. Under optimal conditions, the immunosensor ECL intensity decreased linearly with the logarithm of carcinoembryonic antigen (CEA) concentration in the range of 0.00001-40 ng/mL, with a detection limit of 0.269 fg/mL. The sensor was effectively utilized for the identification of CEA in actual serum samples., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

3-mercaptopropionate (3MPA) dioxygenase (MDO) is a mononuclear nonheme iron enzyme that catalyzes the O 2 -dependent oxidation of thiol-bearing substrates to yield the corresponding sulfinic acid. MDO is a member of the cysteine dioxygenase family of small molecule thiol dioxygenases and thus shares a conserved sequence of active site residues (Serine-155, Histidine-157, and Tyrosine-159), collectively referred to as the SHY-motif. It has been demonstrated that these amino acids directly interact with the mononuclear Fe-site, influencing steady-state catalysis, catalytic efficiency, O 2 -binding, and substrate coordination. However, the underlying mechanism by which this is accomplished is poorly understood. Here, pulsed electron paramagnetic resonance spectroscopy [ 1 H Mims electron nuclear double resonance spectroscopy] is applied to validate density functional theory computational models for the MDO Fe-site simultaneously coordinated by substrate and nitric oxide (NO), (3MPA/NO)-MDO. The enhanced resolution provided by electron nuclear double resonance spectroscopy allows for direct observation of Fe-bound substrate conformations and H-bond donation from Tyr159 to the Fe-bound NO ligand. Further inclusion of SHY-motif residues within the validated model reveals a distinct channel restricting movement of the Fe-bound NO-ligand. It has been argued that the iron-nitrosyl emulates the structure of potential Fe(III)-superoxide intermediates within the MDO catalytic cycle. While the merit of this assumption remains unconfirmed, the model reported here offers a framework to evaluate oxygen binding at the substrate-bound Fe-site and possible reaction mechanisms. It also underscores the significance of hydrogen bonding interactions within the enzymatic active site., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Biobased films were synthesized from starch oleate (DS = 2.2) cross-linked with polyethylene glycol with M n = 2000 and 1000 g · mol -1 , and ethylene glycol, all of which were esterified with either lipoic acid (LA) or 3-mercaptopropionic acid (MPA). Cross-linking was achieved through a UV-initiated thiol-ene click, and confirmed by Fourier transform infrared spectroscopy and rheometry. The films exhibit higher degradation temperatures, and an increased degree of crystallinity as cross-linker length increased. The introduction of MPA-based cross-linkers resulted in hydrophilic films, while the contact angle was barely affected by the addition of LA-based cross-linkers. A reduction in maximum strength upon introducing the cross-linkers was observed, while an increase in elongation was observed for most of the LA-based cross-linkers. Our results demonstrate the potential for tuning the mechanical and thermal properties of starch-based films through the cross-linker choice, with some formulations exhibiting increased flexibility that may be well suited for packaging applications.

Lignin is abundant and contains a large number of aromatic groups. Herein, Cd x Zn 1-x S photocatalyst with tunable band gap energy was successfully synthesized by using 3-mercaptopropionic acid as a structure tuning additive. Cd x Zn 1-x S can depolymerize alkaline lignin to vanillin by the photocatalytic process. Each gram of alkaline lignin can produce 46.5 mg of vanillin. 2-Phenoxy-1-phenylethanol (PP-ol) and other model compounds were used to understand the depolymerizing process of lignin. Fine tuned Cd x Zn 1-x S can effectively cleave the C β -O-4 bond existed in PP-ol under simulated sunlight. The highest conversion of PP-ol was 89.5% with phenol and acetophenone yields of 66.2% and 33.5%, respectively. The mechanism studies confirm that the C α -H in PP-ol and lignin is firstly dehydrogenated to form C α radical intermediates, and then the photogenerated electrons break the adjacent C β -O bond. This research provides a new strategy to prepare valuable chemicals by virtue of renewable biomass and simulated sunlight., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Thiol dioxygenases are a subset of nonheme iron oxygenases that catalyze the formation of sulfinic acids from sulfhydryl-containing substrates and dioxygen. Among this class, cysteine dioxygenases (CDOs) and 3-mercaptopropionic acid dioxygenases (3MDOs) are the best characterized, and the mode of substrate binding for CDOs is well understood. However, the manner in which 3-mercaptopropionic acid (3MPA) coordinates to the nonheme iron site in 3MDO remains a matter of debate. A model for bidentate 3MPA coordination at the 3MDO Fe-site has been proposed on the basis of computational docking, whereas steady-state kinetics and EPR spectroscopic measurements suggest a thiolate-only coordination of the substrate. To address this gap in knowledge, we determined the structure of Azobacter vinelandii 3MDO (Av3MDO) in complex with the substrate analog and competitive inhibitor, 3-hydroxypropionic acid (3HPA). The structure together with DFT computational modeling demonstrates that 3HPA and 3MPA associate with iron as chelate complexes with the substrate-carboxylate group forming an additional interaction with Arg168 and the thiol bound at the same position as in CDO. A chloride ligand was bound to iron in the coordination site assigned as the O 2 -binding site. Supporting HYSCORE spectroscopic experiments were performed on the (3MPA/NO)-bound Av3MDO iron nitrosyl (S = 3/2) site. In combination with spectroscopic simulations and optimized DFT models, this work provides an experimentally verified model of the Av3MDO enzyme-substrate complex, effectively resolving a debate in the literature regarding the preferred substrate-binding denticity. These results elegantly explain the observed 3MDO substrate specificity, but leave unanswered questions regarding the mechanism of substrate-gated reactivity with dioxygen., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Injectable hydrogels with pH-sensitive and self-healing properties have great application potential in the field of anti-cancer drug carriers. In this work, an injectable hydrogel is prepared using 4armPEG-benzaldehyde (4armPEGDA) and N-carboxyethyl chitosan (CEC) as a new drug carrier. The gelation time, equilibrium swelling rate, degradation time, and dynamic modulus of the injectable hydrogels can be adjusted by merely changing the concentration of 4armPEGDA. The volume of the hydrogel shrinks at pH 5.6 and expands at pH 7.4, which helps to control the release of anti-cancer drug. At pH 5.6, the hydrogels show a fast and substantial Dox release effect, which is five times higher than that at pH 7.4. In vitro cumulative drug release of all the hydrogels reached equilibrium on about the fourth day, and the hydrogel is completely degraded within five days, which contributes to the Dox-loaded hydrogel to further release the remaining Dox. Moreover, the Dox-loaded hydrogel shows a strong inhibitory effect on the growth of human hepatocellular carcinoma cells (HepG2). Finally, the anti-tumor model experiment in vivo demonstrated that the Dox-loaded hydrogel can significantly inhibit tumor growth within five days. Therefore, such injectable hydrogels are excellent carriers for the potential treatment of hepatocellular carcinoma., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Death from tuberculosis has resulted in an increased need for early detection to prevent a tuberculosis (TB) epidemic, especially in closed and crowded populations. Herein, a sensitive electrochemical DNA biosensor based on functionalized iron oxide with mercaptopropionic acid (MPA-Fe 3 O 4 ) nanoparticle and nanocellulose crystalline functionalized cetyl trimethyl ammonium bromide (NCC/CTAB) has been fabricated for the detection of Mycobacterium tuberculosis (MTB). In this study, a simple drop cast method was applied to deposit solution of MPA-Fe 3 O 4 /NCC/CTAB onto the surface of the screen-printed carbon electrode (SPCE). Then, a specific sequence of MTB DNA probe was immobilized onto a modified SPCE surface by using the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling mechanism. For better signal amplification and electrochemical response, ruthenium bipyridyl Ru(bpy) 3 2+ was assigned as labels of hybridization followed by the characteristic test using differential pulse voltammetry (DPV). The results of this biosensor enable the detection of target DNA until a concentration as low as 7.96 × 10 -13 M with a wide detection range from 1.0 × 10 -6 to 1.0 × 10 -12 M. In addition, the developed biosensor has shown a differentiation between positive and negative MTB samples in real sampel analysis.

In recent years, gold nanoclusters (AuNCs) have received considerable attention as optical transducers in chemo/biosensors. Herein, a facile and efficient assay for NO 2 - has been successfully developed based on the fluorescence quenching of AuNCs co-modified by bovine serum albumin and 3-mercaptopropionic acid (BSA/MPA-AuNCs). In the presence of NO 2 - under acidic conditions, Fe 2+ can be readily oxidized and transformed to Fe 3+ , which can significantly suppress the fluorescence of BSA/MPA-AuNCs via non-radiative electron-transfer mechanism. The linear range and detection limit for this system were found to be 5-30 μM (r = 0.9975) and 0.7 μM, respectively. Other common anions and cations showed only very minor interference with the NO 2 - detection. Furthermore, the effectiveness of the proposed sensing strategy was validated by the demonstration of good performance in the determination of the amount of NO 2 - in ham samples, rendering it a powerful tool for the assessment of food security and water quality., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

In this work, a novel, selective and sensitive fluorescent probe (sulfur doped graphene quantum dots, SGQDs) was designed for real-time detection of quercetin in red wine samples. SGQDs were synthesized by pyrolyzing citric acid (CA) and 3-Mercaptopropionic acid (MPA) and characterized through advanced techniques. It was observed that fluorescence intensity of SGQDs could be substantially quenched by the addition of quercetin through inner filter effect (IFE) mechanism. Additionally, a visual color change (colorless to light yellow) was also noticed after addition of quercetin into a solution of SGQDs. The change in SGQDs fluorescence intensity with varying quercetin content revealed good linearity in the 0-50.0 μM range with regression coefficient of 0.9943 and a lowest detection limit of 0.006 μg/mL. To authenticate the real-time application of SGQDs as a potential fluorescent probe, red wine samples having different quercetin concentrations were used for quantitative analysis, after the optimization of several analytical parameters., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Mercaptopropionic acid (MPA) capped CdTe quantum dots (MPA-CdTe QDs) were synthesized in aqueous medium by hydrothermal method, which modified by Fe 3+ could be used as a fluorescent probe to detect ascorbic acid (AA). MPA-CdTe QDs fluorescence probe could be used as successive sensor for metal ions and AA with "on-off-on" process. The fluorescence of QDs was quenched after adding Fe 3+ to MPA-CdTe QDs. Then, the fluorescence of the Fe 3+ @MPA-CdTe QDs can be sensitively turned on by AA to give an "on-off-on" fluorescence response according to the oxidation-reduction between Fe 3+ and AA. There was a linear relationship between fluorescence intensity quenching value and the concentration of Fe 3+ in the range of 2-10 μM since Fe 3+ sensitively reacted with CdTe QDs. The linear detection range for AA was 0.1-1 μM with a limit of detection of 6.6 nM. The principle is proved by fluorescence emission spectroscopy, nuclear magnetic resonance spectroscopy. The proposed method is successfully used to detect the AA in human plasma sample., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

The emission wavelength of organic-inorganic hybrid perovskite quantum dots (QDs) can be tuned by controlling reaction time relevant to the halide exchange. It is because halide exchange with different time would lead to different molar ratio of halides in perovskite QDs such as Cl and Br. Here, to research the ligand's effect on the halide exchange, this work synthesized 3-mercaptopropionic acid (MPA)-capped CH 3 NH 3 PbBr x Cl 3-x QDs. It was found that SH - of MPA appeared to inhibit the halide exchange during the reation. Moreover, although the MPA-capped CH 3 NH 3 PbBr x Cl 3-x QDs did not contain the chiral centre, they exhibit the optical rotation. This may provide a method for chirality manipulation of perovskite., (© 2019 John Wiley & Sons, Ltd.)

Herein, 10-fold electrochemiluminescence (ECL) enhancement from a porous SnO 2 nanocrystal (SnO 2 NC) xerogel (vs discrete SnO 2 NCs) was first observed with NO 3 - as a novel coreactant. This new booster phenomenon caused by pore characteristic was defined as "pore confinement-induced ECL enhancement", which originated from two possible reasons: First, the SnO 2 NC xerogel with hierarchically porous structure could not only localize massive luminophore near the electrode surface, more importantly, but could accelerate the electrochemical and chemiluminescence reaction efficiency because the pore channels of xerogel could promote the mass transport and electron transfer in the confined spaces. Second, the NO 3 - could be in situ reduced easily to the active nitrogen species by means of the pore confinement effect, which could be served as a new coreactant for nanocrystal-based ECL amplification with the excellent stability and good biocompatibility. As a proof of concept, a facile and sensitive sensing platform for SO 3 2- detection has been successfully constructed upon effectively quenching of SO 3 2- toward the SnO 2 NC xerogel/NO 3 - ECL system. The key feature about this work presented a grand avenue to achieve the strong ECL signal, especially from weak emitters, which gave a fresh impetus to the construction of new-generation of surface-confined ECL platform with potential applications in ECL imaging and sensing.

Photocatalytic water splitting using solar energy for hydrogen production offers a promising alternative form of storable and clean energy for the future. To design an artificial photosynthesis system that is cost-effective and scalable, earth abundant elements must be used to develop each of the components of the assembly. To develop artificial photosynthetic systems, we need to couple a catalyst for proton reduction to a photosensitizer and understand the mechanism of photo-induced electron transfer from the photosensitizer to the catalyst that serves as the fundamental step for photocatalysis. Therefore, our work is focused on the study of light driven electron transfer kinetics from the quantum dot systems made with inorganic chalcogenides in the presence of Ni-based reduction catalysts. Herein, we report the synthesis and characterization of four Ni(II) complexes of tetradentate ligands with amine and pyridine functionalities (N2/Py2) and their interactions with CdTe quantum dots stabilized by 3-mercaptopropionic acid. The lifetime of the quantum dots was investigated in the presence of the Ni complexes and absorbance, emission and electrochemical measurements were performed to gain a deeper understanding of the photo-induced electron transfer process.

Biosourced materials are gaining interest industrially, but there are still limitations on the library of available materials suitable for advanced manufacturing, especially using photopolymerization-based processing techniques. Terpenes, such as myrcene, are naturally produced materials possessing structural features, specifically alkenes, that avail themselves for such techniques. Free-radical and anionic polymerization techniques were used to explore molecular architecture, such as branching, as well as molecular weight and dispersity on physical properties prior to the production of 3D printing photopolymer resins. The polymyrcene resins were printed into dogbones and mold templates for soft materials. Model reactions with monofunctional thiols were used to demonstrate the potential for postpolymerization and fabrication functionalization, accompanying a physical demonstration where the surface hydrophobicity of polymyrcene could be tuned from superhydrophobic when using an alkyl chain monothiol (greater than 100° water contact angle) to a hydrophilic surface displaying a water contact angle of less than 45° compared with that of the unmodified surface (∼60°). Tunable bulk and surface properties are a unique feature for 3D printing materials and demonstrate the potential of polymyrcene and other biosourced photopolymers to a wide range of research applications.

A colorimetric method is described for the determination of As(III). It is based on the use of 3-mercaptopropionic acid (3-MPA) assisted active site and interlayer channel dual-masking of oxidase-like Fe-Co-layered double hydroxides (Fe-Co-LDH). The Fe-Co-LDH acts as an oxidase-mimicking nanozyme with high activity. It catalyzes the oxidation of colorless 3,3'5,5'-tetramethylbenzidine (TMB) to form a blue product (oxTMB) with an absorption maximum at 652 nm. It is found that As(III) firmly anchors onto the Fe* sites of the 3-MPA-modified Fe-Co-LDH via forming a stable Fe─As(III)─3-MPA─As(III)─Fe structure. This results in masking the active sites and interlayer channels of the Fe-Co-LDH nanozyme. As a result, the presence of As(III) as well as 3-MPA specifically inhibit the LDH-catalyzed chromogenic reaction. Based on the above principle, a colorimetric assay was designed for the determination of As(III). It provided linear response in the 0.10~8.33 μM As(III) concentration range and a detection limit as low as 35 nM. The assay was applied to the quantitation of As(III), even in the presence of potential interferents including As(V), Hg(II) and Pb(II), in environmental and drinking water samples. Graphical abstractSchematic illustration of the As(III) sensing mechanism based on 3-mercaptopropionic acid (3-MPA) assisted active site and interlayer channel dual-masking of Fe-Co-layered double hydroxides (Fe-Co-LDH) with oxidase-like activity. 3-MPA with sulfhydryl and carboxyl groups can assist As(III) to firmly anchor onto the Fe* sites inside the interlayer channels of the Fe-Co-LDH via forming a Fe─As(III)─3-MPA─As(III)─Fe structure, thus selectively resulting in a significant suppression of the chromogenic reaction.

Non-spherical structures are beneficial to advance drug delivery effectiveness compared with common spherical ones, due to increased drug loading capability, improved bonding to a vascular wall, enhanced cellular uptake efficacy and prolonged circulation times. In this study, flower-like Zinc oxide-βcyclodextrin (βCD) nanostructures functionalized by 3-mercaptopropionic acid (MPA) as a non-spherical delivery system was successfully synthesized for aqueous delivery of curcumin (CUR) to enhance its targeting, bioavailability, and release profile. Terminal carboxyl functional groups were used for the conjugation of folic acid (FA) with the aim of active targeting to folate overexpressing breast cancer cells. The in vitro experimental study and mathematical modeling of CUR release revealed a sustained release with Fickian diffusion as the major release mechanism. MTT, colony formation and Annexin-V FITC/PI assays showed the superior anticancer effect of the system compared to free CUR against breast cancer cell line MDA-MB-231 by promoting the apoptotic respond with no cytotoxic effect on HEK293 normal cells. The efficacy of targeting strategy with FA moieties was demonstrated using the augmented cellular uptake of the FA-conjugated system on overexpressed folate receptor alpha (FRα) cells (MDA-MB-468 breast cancer cell line). Furthermore, loading of CUR to the delivery systems significantly lowered the MIC values (2.5 to 5-fold) against S. aureus and E. coli the infections of which are serious problems in cancer patients. According to the results of this study, the system can serve as a promising non-spherical delivery vehicle for enhancing bioavailability and targeting of hydrophobic anticancer agents in the future., (Copyright © 2019 Elsevier B.V. All rights reserved.)

It has already been reported that incorporation of thiol-ene into methacrylate resin could reduce shrinkage stress significantly. However, the mass fraction of thiol-ene in thiol-ene-methacrylate resin system should be limited because of deterioration of mechanical properties. In order to increase mass fraction of thiol-ene in thiol-ene-methacrylate ternary resin system, a new fluorinated ally ether (FUAE) was synthesized and mixed with pentaerythritol tetra (3-mercaptopropionate) (PETMA) at molar ratio of 1:1 to form new thiol-ene resin system, and then the thiol-ene resin was incorporated into Bis-GMA/TEGDMA resin to prepare thiol-ene-methacrylate resin system. The results of neat resin system showed that incorporation of new thiol-ene resin into methacrylate resin could increase degree conversion of methacrylate functional group and decrease volumetric shrinkage. In order to achieve the similar mechanical properties as methacrylate resin, mass fraction of thiol-ene in ternary resin system should not exceed 30 wt%. Thiol-ene-methacrylate resin systems with 10 wt% to 30 wt% were chosen to prepare dental resin composites, and physiochemical properties such as degree of conversion, volumetric shrinkage, shrinkage stress, flexural properties, and water sorption and solubility of these composites were investigated. The results showed that, compared with methacrylate resin-based dental composite, ternary resin-based dental composites had several advantages, such as higher DC% of methacrylate functional group, lower volumetric shrinkage, lower shrinkage stress, lower water sorption and solubility. The flexural properties of ternary resin-based dental composites were comparable or even better than those of methacrylate resin-based dental composite., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Membrane-bound proteins can play a role in the binding of anionic gold nanoparticles (AuNPs) to model bilayers; however, the mechanism for this binding remains unresolved. In this work, we determine the relative orientation of the peripheral membrane protein cytochrome c in binding to a mercaptopropionic acid-functionalized AuNP (MPA-AuNP). As this is nonrigid binding, traditional methods involving crystallographic or rigid molecular docking techniques are ineffective at resolving the question. Instead, we have implemented a computational assay technique using a cross-correlation of a small ensemble of 200 ns long molecular dynamics trajectories to identify a preferred nonrigid binding orientation or pose of cytochrome c on MPA-AuNPs. We have also employed a mass spectrometry-based footprinting method that enables the characterization of the stable protein corona that forms at long time-scales in solution but remains in a dynamic state. Through the combination of these computational and experimental primary results, we have established a consensus result establishing the identity of the exposed regions of cytochrome c in proximity to MPA-AuNPs and its complementary pose(s) with amino-acid specificity. Moreover, the tandem use of the two methods can be applied broadly to determine the accessibility of membrane-binding sites for peripheral membrane proteins upon adsorption to AuNPs or to determine the exposed amino-acid residues of the hard corona that drive the acquisition of dynamic soft coronas. We anticipate that the combined use of simulation and experimental methods to characterize biomolecule-nanoparticle interactions, as demonstrated here, will become increasingly necessary as the complexity of such target systems grows.

Exosomes are non-invasive biomarkers for cancer diagnosis. Herein, we describe an electrochemiluminescent (ECL) aptasensor for the detection of exosomes from breast tumor cells. Mercaptopropionic acid (MPA)-modified Eu 3+ -doped CdS nanocrystals (MPA-CdS:Eu NCs) and H 2 O 2 were used as ECL emitters and coreactant, respectively. The exosomes are recognized and captured by the CD63 aptamer, and then form a G-quadruplex/hemin DNAzyme, which efficiently catalyzes the decomposition of H 2 O 2 , resulting in the decreased ECL signal of MPA-CdS:Eu NCs. The exosomes from breast tumor cells (MCF-7 cells) can be detected in the range of 3.4 × 10 5 to 1.7 × 10 8 particles per mL. The limit of detection (LOD) was estimated to be 7.41 × 10 4 particles per mL at a signal-to-noise ratio of 3. The aptasensor has been successfully used to detect exosomes in the serum.

In the present study, (E)-2,2'-(4,4'-dioxo-2,2'-dithioxo-2H,2'H-[5,5'-bithiazolylidene]-3,3'(4H,4'H)-diyl) bis(3-mercaptopropanoic acid) (DTM) as a new derivative of thiazolidine was synthesis and characterized for the detrtmination of Hg 2+ ions. Then, the CdTe@CdS QDs and DTM capped CdTe@CdS QDs were produced. The DTM-CdTe@CdS/QDs used as an effective fluorescence sensing material due to the selective interaction of DTM with Hg (II). The results indicated that the DTM-CdTe@CdS/QDs shows strong fluorescence emissions in the absence of mercury ions and efficiently quenched in presence of Hg 2 , with the formation of a strong and stable complex between Hg 2+ and DTM. Experimental results showed that under optimal conditions, Hg 2+ could be detected with a detection limit of 0.08 nM in a linear range from 0.3 nM to 21 nM. The constructed aptasensor illustrated the high selectivity for mercury ions even in the presence of the other interfering metal ions when their concentration ratio was more than 300 times. The satisfactory results illustrated that the designed fluorescence sensor as a sensitive, reliable and easy to use approach could be applied for the facile and rapid determination of Hg 2+ in tap water., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A luminescence resonance energy transfer (LRET) system was successfully developed using near-infrared (NIR) Ag 2 S nanodots (NDs) as the energy acceptors and upconversion nanoparticles (UCNPs) as the energy donors. The system possessing the properties of NIR excitation (980 nm) and NIR emission (795 nm) was used for the ratiometric detection and bioimaging of pH in tumor cells and zebrafish. Glutathione and mercaptopropionic acid (MPA) co-modified Ag 2 S NDs (GM-Ag 2 S NDs) were prepared by ligand exchange with an excellent pH-responsive property over a pH range of 4.0 to 9.0. The NIR GM-Ag 2 S NDs were covalently grafted with silica coated UCNPs, and an efficient LRET platform was developed via modulation of the thickness of the silica coating. Due to the LRET process between UCNPs and GM-Ag 2 S NDs, a ratiometric luminescence nanoprobe with the properties of NIR excitation-NIR emission was constructed for pH biosensing and bioimaging. On the basis of high contrast bioimaging, the nanoplatform can distinguish between tumor and normal tissue in the zebrafish model.

A fluorescent nanoprobe consisting of CdTe quantum dots (QDs) and coated with molecularly imprinted layers was prepared and successfully applied to the determination of norfloxacin (NOR) in seawater and wastewater samples. The 3-mercaptopropionic acid capped QDs were prepared and then covered with a protective silica shell. A molecularly imprinted layer was finally synthesized around the silanized QDs using 3-aminopropyltriethoxysilane as functional monomer and norfloxacin as the template. Compared with the non-imprinted polymer, the fluorescence of the nanoprobe with imprinted polymer (measured at excitation/emission wavelengths of 300/596 nm) is strongly reduced in the presence of NOR, and the imprinting factor is 8.8. Under the optimal experimental conditions, the detection limit of the nanoprobe is 0.18 μM, and response is linear between 0.5 - 28 μM of NOR. The relative standard deviation of the detection of NOR is <7.2%. In order to evaluate the practicality of the probe, wastewater and seawater samples spiked with norfloxacin were analyzed by this method, and recoveries ranged from 96.2 - 106.0%. Graphical abstract Schematic presentation and fluorescence spectrum of fluorescent nanoprobe with selectivity for norfloxacin (NOR). CdTe quantum dots (QDs) are used as fluorescent carriers, 3-aminopropyltriethoxysilane (APTES) as template molecules, tetraethyl orthosilicate (TEOS) as crosslinking agent, and aqueous ammonia as initiator.

The analysis of protein in algal biomass is one of the most critical areas of commercial development of algae characterization for nutritional or other high value applications. A new rapid and accurate method is required that can be widely implemented and that is free from interferences from the complex algal biomass matrix. We developed a simple spectrophotometric method for primary amino acid quantification bulk measurement in an acid hydrolyzed algal biomass preparation, as an alternative to the more labor-intensive amino HPLC acid analysis or less specific nitrogen-to-protein conversion. We have validated an O-phthalaldehyde (OPA)-based derivatization method, showing accurate and linear quantification for standard reference amino acids as well as mixtures, mimicking the amino acid complexity found in algal biomass. The presence of interferences that may be derived from the complex biomass biochemical composition was tested during the method validation phase. We document the application of a novel method of OPA derivatization with 3-mercaptopropionic acid (3MPA) to determine the total amino acid content of harvested algal biomass collected from different, controlled cultivation conditions and demonstrated a within 10% accuracy against a reference measurement of amino acid content in at least 4 species and 10 algal biomass samples, across early, mid, and late-stages of cultivation.

Thiol dioxygenases make up a class of ferrous iron-dependent enzymes that oxidize thiols to their corresponding sulfinates. X-ray diffraction structures of cysteine-bound cysteine dioxygenase show how cysteine is coordinated via its thiolate and amine to the iron and oriented correctly for O atom transfer. There are currently no structures with 3-mercaptopropionic acid or mercaptosuccinic acid bound to their respective enzymes, 3-mercaptopropionate dioxygenase or mercaptosuccinate dioxygenase. Sequence alignments and comparisons of known structures have led us to postulate key structural features that define substrate specificity. Here, we compare the rates and reactivities of variants of Rattus norvegicus cysteine dioxygenase and 3-mercaptopropionate dioxygenases from Pseudomonas aureginosa and Ralstonia eutropha (JMP134) and show how binary variants of three structural features correlate with substrate specificity and reactivity. They are (1) the presence or absence of a cis-peptide bond between residues Ser158 and Pro159, (2) an Arg or Gln at position 60, and (3) a Cys or Arg at position 164 (all RnCDO numbering). Different permutations of these features allow sulfination of l-cysteine, 3-mercaptopropionic acid, and ( R)-mercaptosuccinic acid to be promoted or impeded.

Over the past several years, the biomedical applications of fluorescent organic nanoparticles (FONs) with aggregation-induced emission (AIE) feature have been extensively explored because the AIE-active FONs could effectively overcome the aggregation caused quenching (ACQ) effect of FONs based on conventional organic dyes. The development of novel methods for synthesis of AIE-active FONs plays a centre role for their biomedical applications. In this work, we reported a facile one-step thiol-ene click reaction for fabrication of AIE-active FONs through conjugation of acrylated PEG and AIE-active tetraphenylethylene (TPE) with two ene bonds using pentaerythritol tetra(3-mercaptopropionate) as the linkage. The successful synthesis of TPE containing AIE-active copolymers was evidenced by various characterization techniques. The particle size and fluorescence properties of the resultant TPE-S-PEG copolymers were evaluated by transmission electronic microscopy and fluorescence spectroscopy. Moreover, the cell viability and cell uptake behavior was also examined to evaluate their potential for biological imaging. We demonstrated that the cross-linked TPE-S-PEG show small size, high water dispersibility, low cytotoxicity and strong fluorescence for tracing. All of these advantages endow the TPE-S-PEG FONs great potential for biological imaging applications. Furthermore, this novel click reaction can take place under mild experimental conditions with high efficiency. It could be also further expanded for preparation of multifunctional AIE-active materials due to the universality of the thiol-ene click reaction and good precursor applicapability. Taken together, we have developed a novel and effective thiol-ene click reaction to fabricate the cross-linked AIE-active FONs, which display excellent physicochemical and biological properties and are promising for biomedical applications., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In this work core/shell cadmium-free zinc‑copper‑indium sulfide ZnCuInS/ZnS quantum dots (QDs) originally stabilized with hydrophilic alkanethiol were modified with 3-mercaptopropionic acid (MPA) or 6-mercaptohexanoic acid (MHA) via two-step ligand exchange method. The obtained QDs were further characterized by TEM, UV Vis, and fluorescence spectroscopy. Both types of QDs were non-toxic in a wide range of concentrations. To our knowledge, our studies are the first attempt to determine the type of cell death and reactive oxygen species production level as a result of incubation of cell cultures with ZnCuInS/ZnS QDs. Furthermore, the accumulation of QDs in vitro was examined on three human cell lines by fluorescence intensity measurements and visualized by confocal microscopy. The modification of QDs with a ligand characterized by slightly longer aliphatic chain (MHA), instead of typically used MPA turns out to be beneficial both from the point of colloidal stability, preservation of optical properties during ligand exchange as well as reflects in a higher cellular uptake. This contribution can be beneficial from the point of view of the selection of the optimal ligands and concentrations in the case of ZnCuInS/ZnS core-shell QDs for biological applications., (Copyright © 2018 Elsevier B.V. All rights reserved.)

This paper reports a simple, facile and rapid preparation of 3‑mercapto‑propanoic acid (MPA) modified cellulose filter paper (MPA-Cell paper) for arsenate removal from drinking water. The MPA was covalently grafted to the cellulose filter paper (Cell) by esterification process through the formation of O‑acylisourea intermediate and characterized by the FTIR, SEM, EDS and XPS analyses. The arsenate adsorption efficiency was studied for batch and semi-continuous systems while exploring the adsorption kinetics, isotherm and the effect of pH for the former. The experimental data fitted well with Langmuir, Dubinin-Radushkevich (DR) and pseudo second order kinetic models. The mechanism of adsorption was studied by FTIR spectroscopy utilizing the adsorption isotherm, kinetic model and XPS results. The modified filter paper performed well at nearly neutral pH in arsenate removal through adsorption and demonstrated a significant arsenate uptake capacity of 92.59 mg/g. The DR and FTIR results indicated that the adsorption of arsenate ion occurred through ion exchange process. The MPA-Cell paper could have a potential use as low-cost but efficient commercial adsorbent for arsenate abatement from contaminated drinking water by both batch as well as semi-continuous operating systems. The MPA-Cell paper could purify ground water containing high level of arsenate., (Copyright © 2018. Published by Elsevier B.V.)

Magnolol, a neolignan natural product with antioxidant properties, contains inherent, orthogonal, phenolic, and alkenyl reactive groups that were used in both direct thermoset synthesis, as well as the stepwise synthesis of a small library of monomers, followed by transformation into thermoset materials. Each monomer from the small library was prepared via a single step functionalization reaction of the phenolic groups of magnolol. Thermoset materials were realized through solvent-free, thiol-ene reactions, and the resulting cross-linked materials were each comprised of thioether and ester linkages, with one retaining the hydrophilic phenols from magnolol, another having the phenols protected as an acetonide, and two others incorporating the phenols into additional cross-linking sites via hydrolytically labile carbonates or stable ether linkages. With this diversity of chemical compositions and structures, the thermosets displayed a range of thermomechanical properties including glass transition temperatures, T g , 29-52 °C, onset of thermal degradation, T d , from about 290-360 °C, and ultimate strength up to 50 MPa. These tunable materials were studied in their degradation and biological properties with the aim of exploiting the antioxidant properties of the natural product. Hydrolytic degradation occurred under basic conditions (pH = 11) in all thermosets, but with kinetics that were dependent upon their chemical structures and mechanical properties: 20% mass loss was observed at 5, 7, 27, and 40 weeks for the thermosets produced from magnolol directly, acetonide-protected magnolol, bis(allyl carbonate)-functionalized magnolol, and bis(allyl ether)-functionalized magnolol, respectively. Isolated degradation products and model compounds displayed antioxidant properties similar to magnolol, as determined by both UV-vis and in vitro reactive oxygen species (ROS) assays. As these magnolol-based thermosets were found to also allow for extended cell culture, these materials may serve as promising degradable biomaterials.

Adenosine triphosphate-binding cassette (ABC) transporters, including P-glycoprotein (Pgp) and multi-resistance associated proteins (Mrps), have been considered important participants in the self-protection of zebrafish embryos against environmental pollutants, but their possible involvement in the efflux and detoxification of quantum dots (QDs), as well as their regulation mechanism are currently unclear. In this work, gene expression alterations of ABC transporters, nuclear receptors, and oxidative stress signaling in zebrafish embryos after the treatment of mercaptopropionic acid (MPA)CdTe QDs and MPA-CdSCdTe QDs were investigated. It was observed that both QDs caused concentration-dependent delayed hatching effects and the subsequent induction of transporters like mrp1&2 in zebrafish embryos, indicating the protective role of corresponding proteins against CdTe QDs. Accompanying these alterations, expressions of nuclear receptors including the pregnane X receptor (pxr), aryl hydrocarbon receptor (ahr) 1b, and peroxisome proliferator-activated receptor (ppar)-β were induced by QDs in a concentration- and time-dependent manner. Moreover, elevated oxidative stress, reflected by the reduction of glutathione (GSH) level and superoxide dismutase (SOD) activities, as well as the dramatic induction of nuclear factor E2 related factor (nrf) 2, was also found. More importantly, alterations of pxr and nrf2 were more pronounced than that of mrps, and these receptors exhibited an excellent correlation with delayed hatching rate in the same embryos (R 2  > 0.8). Results from this analysis demonstrated that the induction of mrp1 and mrp2 could be important components for the detoxification of QDs in zebrafish embryos. These transporters could be modulated by nuclear receptors and oxidative stress signaling. In addition, up-regulation of pxr and nrf2 could be developed as toxic biomarkers of CdTe QDs., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Thrombin plays an important role in the blood coagulation cascade and it stimulates the process of platelet aggregation. Herein, we developed a highly efficient and sensitive phosphorescent aptasensor system for the quantitative analysis of thrombin. The phosphorescence of 3-mercaptopropionic acid capped Mn-doped ZnS quantum dots (MPA-Mn:ZnS QDs) was gradually quenched with the addition of thrombin binding aptamers-BHQ2 (TBA-BHQ2) based on phosphorescence resonance energy transfer (PRET). With the addition of the target analyte thrombin into the system, TBA-BHQ2 could change its spatial structure from a random coil to an antiparallel G-quadruplex which resulted from the combination of thrombin and TBA-BHQ2, leading to the phosphorescence recovery. Finally, the concentration of thrombin could be accurately determined by means of measuring the phosphorescence intensity change value (ΔP). The limit of detection (LOD) was obtained as low as 15.26 pM with wide linear ranges both from 60 to 2000 pM and from 2 to 900 nM. The proposed strategy was also successfully applied for thrombin detection in human serum samples and plasma samples with satisfactory recoveries from 96% to 99% and 95% to 104%, respectively. The long lifetime of phosphorescent QDs possessed a suitable time delay to eliminate autofluorescence and scattered light interference from biological matrices effectively. Thus, the signal to noise ratio of the phosphorescent aptasensor was improved visibly for the analysis of target analytes.

An "off-on" phosphorescent aptasensor based on the 3-mercaptopropionic acid (MPA) capped Mn-doped ZnS quantum dots (MPA-Mn:ZnS QDs)/aptamer hybrid system was developed to detect adenosine triphosphate (ATP) in biological fluids. The phosphorescence of MPA-Mn:ZnS QDs was obviously quenched when ATP aptamer was added due to the aggregation induced effect. ATP aptamer, adsorbed on the surface of the phosphorescent MPA-Mn:ZnS QDs, has a high affinity for ATP. And then, with the addition of ATP, phosphorescence was gradually recovered because of the stronger special binding interaction between ATP and ATP aptamer than that between QDs and ATP aptamer. In this case, a high sensitivity and selectivity of phosphorescent aptasensor for the detection of ATP has constructed with a low detection limit of 0.9 nM and a wide linear range from 2 nM to 9 µM. What's more, the phosphorescent aptasensor does not require complex pretreatments and can effectively eliminate the interference from auto fluorescence and scattering light., (Copyright © 2018 Elsevier B.V. All rights reserved.)

We studied the influence of magnetite nanoparticles (FeO•Fe 2 O 3 ) and quantum dots (CdSe/ZnS coated with mercaptopropionic acid) on the expression of 5 common reference genes (BA, B2M, PPIA, UBC, and YWHAZ) in peripheral blood cells from 20 volunteers by reverse transcription PCR method. The stability of the expression of reference genes varied depending of the cells type and chemical structure of nanoparticles. The level of YWHAZ mRNA after exposure by nanoparticles demonstrated highest stability in lymphocytes, neutrophils, and monocytes. Stability of YWHAZ expression was confirmed by Western blotting. Our findings suggest that YWHAZ is the most suitable as the reference gene.

We present here the correlation of picomolar affinities between surface-plasmon and electrochemical immunoassays for the binding of serum glutamic acid decarboxylase 65 autoantibody (GADA), a biomarker of type 1 diabetes (T1D), to its antigen GAD-65. Carboxylated (∼5.0%)-graphene-modified immunoassembly on a gold surface-plasmon chip or on an electrochemical array provided significantly larger binding affinity, higher sensitivity, and lower detection limits than a self-assembled monolayer surface of mercaptopropionic acid (MPA). Estimation of the relative surface -COOH groups by covalent tagging of an electroactive aminoferrocene showed that the graphenyl surface displayed a greater number of -COOH groups (9-fold) than the MPA surface. X-ray-photoelectron-spectroscopy analysis showed more C-O and C═O functionalities on the graphene-COOH surface than on the MPA surface. The graphene-COOH coating on gold exhibited ∼5.5-fold enhancement of plasmon signals compared with a similar coating on a plain glass surface. In summary, this article provides a quantitative comparison of carboxylated graphene with a mercapto-monolayer immunoassembly. Additionally, we propose that the binding-constant value can be useful as a quality-control checkpoint for reproducible and reliable production of large-scale biosensors for clinical bioassays.

Quantum dots (QDs) have significant potentials in biomedical applications of bioimaging and biosensing. Spontaneous adsorption of proteins on QDs surface is a common phenomenon, which occurred to serum proteins in biological samples, and has been observed to enhance QDs fluorescence. In this study, fluorescence alteration of 3-mercaptopropionic acid (MPA) capped CdSe quantum dots by four individual biomarker proteins was investigated. By monitoring the fluorescence emission of QDs, the biomarker protein adsorbed spontaneously on QDs surface was recognized and quantified. When alpha fetoprotein (AFP) or heat shock protein 90 alpha (HSP90α) were present, the QDs became brighter. The presence of cytochrome C (CytoC) or lysozyme (Lyz) made the QDs dimmer first, and then brighter. Within five minutes response time all four biomarker proteins were detected individually with the estimated detection limit in the range of 1-10 ng/mL and good linear dynamic ranges. The results suggested that the fluorescence of QDs was responsive to not only serum proteins but also biomarker proteins. The fluorescence response was able to correlate quantitatively with the amount of biomarker proteins in relatively low concentrations. These results provide more information to understand QDs and support their applications in biomedical fields., (Published by Elsevier Inc.)

As a promising biolabeling biomaterials, quantum dots (QDs) present a great potential. However, the toxicity of QDs to organisms has attracted wide attention. In our research, we introduced an in vitro method to study the molecular mechanisms for the structure and activity alterations of Candida rugosa lipase (CRL) with the binding of 3-mercaptopropionic acid-capped CdTe QDs. Multiple spectroscopic methods, isothermal titration calorimetry, and enzyme activity measurements were used in this paper. QDs statically quenched the intrinsic fluorescence of CRL with the quenching constant decreases from 2.46 × 10 13 to 1.64 × 10 13  L mol -1  second -1 (298 to 310 K). It binds to CRL through hydrophobic force with 1 binding site, unfolding and loosening the skeleton and changed its secondary structure. Rather than aggregating on the surface, it enters the pocket of the CRL to interact with Ser-209 (2.43 Å) and the residues surrounding Ser-209, making the catalytic triad more exposed. Furthermore, the activity of CRL was inhibited by approximately 15%. This work demonstrates that 3-mercaptopropionic acid-capped CdTe QDs may cause negative effects to CRL and obtains a molecular mechanism on QD-induced toxicity to proteins in vitro., (Copyright © 2018 John Wiley & Sons, Ltd.)

Under conditions with or without linker molecules, the effects of acidic pH on the conformation of yeast iso-1-cytochrome c coated onto gold nanoparticles (AuNPs) in correlation with color changes of a Cyt c-coated AuNPs solution/suspension were examined by Fourier transform infrared (FT-IR) spectroscopy and correlated to color change. The results of detailed secondary structural analysis revealed that although the color changes coincide with acid-induced conformational changes in Cyt c coated onto AuNPs, the pH-related conformational unfolding of Cyt c coated onto AuNPs differed dramatically from that of its counterpart in solution. For Cyt c free in solution, the acid-induced unfolding did not occur until the pH was below 3.0, whereas for Cyt c coated onto AuNPs via C102 coordination near the C-terminal, a partial unfolding was observed even at near neutral pH which continuously intensified as pH decreased. Insertion of a short alkanethiol (3-mercaptoproprionic acid, 3-MPA) molecule between Cyt c and AuNP, which changes the interaction mode from a thiol coordination between Cyt c and AuNP to an electrostatic interaction between Cyt c and 3-MPA, which stabilized the conformation of Cyt c significantly, but did not prevent the acid-induced aggregation of Cyt c-3MPA-AuNPs., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Water-soluble ZnS:Mn quantum dots (QDs) were synthesized using a hydrothermal method with 3-mercaptopropionic acid as stabilizer. The optical properties of ZnS:Mn QDs were thoroughly investigated by tuning the doping concentration of Mn 2+ and the Zn/S precursor ratio, to obtain an optimal parameter for QDs with excellent fluorescence characteristics. ZnS:Mn QDs excited at only one wavelength, however, which seriously limited their further application. Here, a trace Cd ion was doped into a ZnS host, resulting in QD excitation covering a wide adjustable waveband. Furthermore, when a ZnS shell was coated onto the surface of the ZnCdS:Mn QDs, photoluminescence intensity and stability were further enhanced. After coupling with an anti-CK 19 antibody, the ZnCdS:Mn/ZnS core/shell QDs were able to function by labeling cancer cells, indicating that they could be considered as a suitable bio-probe for cells and tissue imaging., (Copyright © 2018 John Wiley & Sons, Ltd.)

Peptide-based molecular electronic devices are promising due to the large diversity and unique electronic properties of biomolecules. These electronic properties can change considerably with peptide structure, allowing diverse design possibilities. In this work, we explore the effect of the side-chain of the peptide on its electronic properties, by using both experimental and computational tools to detect the electronic energy levels of two model peptides. The peptides include 2Ala and 2Trp as well as their 3-mercaptopropionic acid linker which is used to form monolayers on an Au surface. Specifically, we compare experimental ultraviolet photoemission spectroscopy measurements with density functional theory based computational results. By analyzing differences in frontier energy levels and molecular orbitals between peptides in gas-phase and in a monolayer on gold, we find that the electronic properties of the peptide side-chain are maintained during binding of the peptide to the gold substrate. This indicates that the energy barrier for the peptide electron transport can be tuned by the amino acid compositions, which suggests a route for structural design of peptide-based electronic devices.

The purpose of this study was to determine the toxicity of two different sources of cadmium, i.e. CdCl 2 and Cd-based Quantum Dots (QDs), for freshwater model plant Lemna minor L. Cadmium telluride QDs were capped with two coating ligands: glutathione (GSH) or 3-mercaptopropionic acid (MPA). Growth rate inhibition and final biomass inhibition of L. minor after 168-h exposure were monitored as toxicity endpoints. Dose-response curves for Cd toxicity and EC50 168h values were statistically evaluated for all sources of Cd to uncover possible differences among the toxicities of tested compounds. Total Cd content and its bioaccumulation factors (BAFs) in L. minor after the exposure period were also determined to distinguish Cd bioaccumulation patterns with respect to different test compounds. Laser-Induced Breakdown Spectroscopy (LIBS) with lateral resolution of 200µm was employed in order to obtain two-dimensional maps of Cd spatial distribution in L. minor fronds. Our results show that GSH- and MPA-capped Cd-based QDs have similar toxicity for L. minor, but are significantly less toxic than CdCl 2 . However, both sources of Cd lead to similar patterns of Cd bioaccumulation and distribution in L. minor fronds. Our results are in line with previous reports that the main mediators of Cd toxicity and bioaccumulation in aquatic plants are Cd 2+ ions dissolved from Cd-based QDs., (Copyright © 2017 Elsevier Inc. All rights reserved.)

pH-sensitive nanogels with ortho ester linkages were conveniently prepared through reaction of thiol-ene click chemistry. Through adjusting feed reactant ratios and concentrations of ortho ester diacrylamide (OEAM), pentaerythritol tetra(3-mercaptopropionate) (PT), and methoxyl poly(ethyleneglycol) acrylate (mPEGA), the size of the nanogels could be controlled at 100-200nm with relatively narrow size distributions. The nanogels with size of 149.1±17.7nm (designed as NG) were verified by proton nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), dynamic laser scattering (DLS) and transmission electron microscopy (TEM). Doxorubicin (DOX) was loaded into NG with high drug loading efficiency up to 73.7%. In vitro drug release studies showed that up to 75.9% DOX from NG was released in 24h at pH 5.0 because of hydrolysis of ortho ester. Cellular uptake studies confirmed that DOX-loaded NG (NG/DOX) could be readily internalized by two-dimensional cells, resulting in efficient antitumor efficiency of cancer cells. Three-dimensional (3D) multicellular tumor spheroids (MCTS) as in vitro tumor model was used to further evaluate the antitumor effect of NG/DOX. The results demonstrated that NG/DOX showed a significantly enhanced penetration and growth inhibition in 3D multicellular tumor spheroids (MCTS), compared to free DOX., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Colloidal semiconductor quantum dots (QDs) have been extensively researched and developed for biomedical applications, including drug delivery and biosensing assays. Hence, it is pivotal to understand their behavior in terms of intracellular transport and toxicological effects. In this study, we focused on 3-mercaptopropionic acid-coated CdSe-CdS/ZnS core-multishell quantum dots (3MPA-QDs) converted from the as-grown octadecylamine-coated quantum dots (ODA-QDs) and their direct and dynamic interactions with human umbilical vein endothelial cells (HUVECs). Live cell imaging using confocal fluorescence microscopy showed that 3MPA-QDs first attached to and subsequently aggregated on HUVEC plasma membrane ~25 min after QD deposition. The aggregated QDs started being internalized at ~2 h and reached their highest internalization degree at ~24 h. They were released from HUVECs after ~48 h. During the 48 h period, the HUVECs responded normally to external stimulations, grew, proliferated and wound healed without any perceptible apoptosis. Furthermore, 1) 3MPA-QDs were internalized in newly formed LysoTracker-stained early endosomes; 2) adenosine 5'-triphosphate-induced [Ca 2+ ] i modulation caused a transient decrease in the fluorescence of 3MPA-QDs that were attached to the plasma membrane but a transient increase in the internalized 3MPA-QDs; and 3) fluorescence signal modulations of co-stained LysoTracker and QDs induced by the lysosomotropic agent Gly-Phe-β-naphthylamide were spatially co-localized and temporally synchronized. Our findings suggest that 3MPA-QDs converted from ODA-QDs are a potential nontoxic fluorescent probe for future use in clinical applications. Moreover, the photophysical strategy and techniques reported in this work are easily applicable to study of direct interactions between other nanoparticles and live cells; contributing to awareness and implementation of the safe applications of nanoparticles., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

The increasingly wide use of semiconductor nanocrystals inevitably leads to their release into aquatic environment. The aggregation behaviors of 3-mercaptopropionic acid-capped CdSe/CdS core-shell quantum dots (MPA-QDs) under various water chemistry conditions were examined and their removal using Fe 3+ and Al 3+ coagulants was evaluated. Cationic species rather than concentrations affected the stability of MPA-QDs. Adding 2 mM Ca 2+ led to a much larger ζ-potential decrease and particle size increase than adding 150 mM K + at each tested solution pH. This indicated that complexation and depletion of surface-bound carboxyl groups by divalent Ca 2+ has a more pronounced effect than compression of the electrical double layer by high concentrations of monovalent K + . The presence of humic acid increased the stability of MPA-QDs, which might increase negative surface charging via overcoating or bind to the surface of MPA-QDs. The nanoparticles exhibited similar aggregation kinetics patterns in tap water and seawater, but varying patterns in the lake water because of the co-existence of 2.3 mM total of Ca 2+ and Mg 2+ . MPA-QDs (5 mg L -1 ) were readily coagulated by 2.4 mM Al 3+ or 1.2 mM Fe 3+ in tap water. Al 3+ and Fe 3+ can bind with carboxyl groups of the surface capping ligands, neutralize the negative charges on the surface of MPA-QDs and decrease the electrostatic repulsion forces to induce MPA-QDs aggregation. In addition, MPA-QDs could be bound with and wrapped into the flocs of hydrolysis products of coagulants. The results reported here could help broaden our understanding of the impacts and remediation of water-dispersed core-shell QD nanoparticles., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

One-step thiol-maleimide polymerization reaction was firstly adopted for direct preparation of polymeric monoliths via alkaline-catalyzed reaction of 4,4'-bis(maleimidophenyl)methane (BMI) and trimethylolpropane tris(3-mercaptopropionate) (3SH)/pentaerythriol tetra(3-mercaptopropionate) (4SH) in the presence of a small amount of triethylamine (TEA). The polymerization could be performed within 3h, which was faster than thermal-initiated free radical polymerization. Two kinds of monoliths, poly(BMI-co-3SH) (marked as I) and poly(BMI-co-4SH) (marked as II), were characterized with scanning electron microscopy (SEM), attenuated total reflection Fourier-transformed infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA) and mercury intrusion porosimetry (MIP). Satisfactory chromatographic separation ability and column efficiency were gained for analysis of small molecular compounds such as alkylbenzenes, polynuclear aromatic hydrocarbons (EPA 610) and phenols in reversed-phase capillary liquid chromatography (cLC). High column efficiency (180,500N/m) for butylbenzene was acquired on poly(BMI-co-3SH) column I-2, which was higher than those on most reported polymeric monoliths. A retention-independent efficient performance of small molecules was obtained by plotting of plate height (H) of alkylbenzenes versus the linear velocity (u). A term values in van Deemter equation of I-2 (1.72-0.24μm) and poly(BMI-co-4SH) column II-2 (5.28-4.14μm) were smaller than those of traditional organic/hybrid monoliths. Finally, as a practical application, 53 and 2184 unique peptides from the tryptic digests of bovine serum albumin (BSA) and HeLa cell proteins were positively identified with poly(BMI-co-3SH) monolith in cLC-MS., (Copyright © 2017. Published by Elsevier B.V.)

Quantum dots (QDs) have been considered to be promising probes for biosensing, bioimaging, and diagnosis. However, their toxicity issues caused by heavy metals in QDs remain to be addressed, in particular for their in vivo biomedical applications. In this study, a parallel comparative investigation in vitro and in vivo is presented to disclose the impact of synthetic methods and their following surface modifications on the toxicity of QDs. Cellular assays after exposure to QDs were conducted including cell viability assessment, DNA breakage study in a single cellular level, intracellular reactive oxygen species (ROS) receptor measurement, and transmission electron microscopy to evaluate their toxicity in vitro. Mice experiments after QD administration, including analysis of hemobiological indices, pharmacokinetics, histological examination, and body weight, were further carried out to evaluate their systematic toxicity in vivo. Results show that QDs fabricated by the thermal decomposition approach in organic phase and encapsulated by an amphiphilic polymer (denoted as QDs-1) present the least toxicity in acute damage, compared with those of QDs surface engineered by glutathione-mediated ligand exchange (denoted as QDs-2), and the ones prepared by coprecipitation approach in aqueous phase with mercaptopropionic acid capped (denoted as QDs-3). With the extension of the investigation time of mice respectively injected with QDs, we found that the damage caused by QDs to the organs can be gradually recovered. This parallel comparative investigation suggests that synthetic methods and their resulting surface microenvironment play vital roles in the acute toxicity profiles of QDs. The present study provides updated insights into the fabrication and surface engineering of QDs for their translational applications in theranostics., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

The effect of 3-mercaptopropionic acid (MPA)-capped CdTe quantum dots (QDs) on lysozyme was systematically investigated by spectroscopic methods, enzyme activity assay, and calorimetry techniques. Results show that the MPA-capped CdTe QDs binded to lysozyme through van der Walls forces and hydrogen bondings, causing the decrement of α-helical content (∼7%) and increment of β-sheet content (∼11%) of lysozyme. The binding caused static quenching of the fluorescence, while the microenvironment of aromatic amino acid residues did not show any significant alteration. The lysozyme activity was affected by the increasing exposure of QDs, it was inhibited to 53.77% under a 6 × 10 -7  M exposure compared with the control group. This work will provide direct evidence about enzyme toxicity of QDs to lysozyme in vitro., (© 2017 Wiley Periodicals, Inc.)

The development of a simple and accurate quantitative method for the determination of 6-mercaptopurine (6-MP) is of great importance because of its serious side effects. Ratiometric fluorescence (RF) sensors are not subject to interference from environmental factors, and exhibit enhanced precision and accuracy. Therefore, a novel RF sensor for the selective detection of 6-MP was developed based on a dual-emission nanosensor. The nanosensor was fabricated by combining a blue-emission metal-organic framework (MOF) NH 2 -MIL-53(Al) (λ em =425nm) with green-emission 3-mercaptopropionic acid-capped CdTe quantum dots (MPA-CdTe QDs) (λ em =528nm) under a single excitation wavelength (335nm). Upon addition of 6-MP, the fluorescence of NH 2 -MIL-53(Al) in the nanohybrid was selectively quenched due to strong inner filter effects, while the fluorescence of the MPA-CdTe QDs was enhanced. The novel RF sensor exhibited higher selectivity towards 6-MP than CdTe QDs alone, and higher sensitivity than MOFs alone. 6-MP could be detected in the range of 0-50μM with a detection limit of 0.15μM (S/N=3). The developed sensor was applied for the determination of 6-MP in human urine samples and satisfactory results were obtained. Overall, a novel and efficient fluorescence-based method was developed for the detection of 6-MP in biosamples., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this work, a porous structure and good permeability monolithic column was polymerized in UV transparent fused-silica capillaries via photo-initiated thiol-ene click polymerization of 2,4,6,8-tetravinyl-2,4,6,8-tetramethylcyclotetrasiloxane (TMTVS), pentaerythritol tetra(3-mercaptopropionate)(PETMP), itaconic acid, respectively, in the presence of porogenic solvents (tetrahydrofuranand methanol) and an initiator (2,2-dimethoxy-2-phenylacetophenone) (DMPA) within 30 min. The physical properties of this monolith were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and nitrogen adsorption/desorption measurements. For an overall evaluation of the monolith in chromatographic application, separations of polycyclic aromatic hydrocarbons (PAHs), phenols, amides and bases were carried out. The column efficiency of this monolith could be as high as 112 560 N/m. It also possesses a potential application in fabrication of monoliths with high efficiency for c-LC. In addition, the resulting monolithic column demonstrated the potential use in analysis of environment waters., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Understanding the mechanism of nanosilver-dependent antibacterial activity against microorganisms helps optimize the design and usage of the related nanomaterials. In this study, we prepared four kinds of 10 nm-sized silver nanoparticles (AgNPs) with dictated surface chemistry by capping different ligands, including citrate, mercaptopropionic acid, mercaptohexanoic acid, and mercaptopropionic sulfonic acid. Their surface-dependent chemistry and antibacterial activities were investigated. Owing to the weak bond to surface Ag, short carbon chain, and low silver ion attraction, citrate-coated AgNPs caused the highest silver ion release and the strongest antibacterial activity against Escherichia coli , when compared to the other tested AgNPs. The study on the underlying antibacterial mechanisms indicated that cellular membrane uptake of Ag, NAD + /NADH ratio increase, and intracellular reactive oxygen species (ROS) generation were significantly induced in both AgNP and silver ion exposure groups. The released silver ions from AgNPs inside cells through a Trojan-horse-type mechanism were suggested to interact with respiratory chain proteins on the membrane, interrupt intracellular O 2 reduction, and induce ROS production. The further oxidative damages of lipid peroxidation and membrane breakdown caused the lethal effect on E. coli . Altogether, this study demonstrated that AgNPs exerted antibacterial activity through the release of silver ions and the subsequent induction of intracellular ROS generation by interacting with the cell membrane. The findings are helpful in guiding the controllable synthesis through the regulation of surface coating for medical care purpose., Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Flavonoids are polyphenols that help the maintenance of health, aiding the prevention of diseases. In this work, CdTe QDs coated with 3-mercaptopropionic acid (3MPA), with an average size of 2.7nm, were used as photoluminescence probe for flavonoids in different conditions. The interaction between 14 flavonoids and QDs was evaluated in aqueous dispersions in the absence and in the presence of cetyltrimethylammonium bromide (CTAB). To establish a relationship between photoluminescence quenching and the concentration of flavonoids, the Stern-Volmer model was used. In the absence of CTAB, the linear ranges for quercetin, morin and rutin were from 5.0×10 -6 molL -1 to 6.0×10 -5 molL -1 and from 1.0×10 -5 molL -1 to 6.0×10 -4 molL -1 for kaempferol. The sensibility of the Stern-Volmer curves (K s ) indicated that quercetin interacts more strongly with the probe: K s quercetin >K s kaempferol >K s rutin >K s morin . The conjugation extension in the 3 rings, and the acidic hydroxyl groups (positions 3'and 4') in the B-ring enhanced the interaction with 3MPA-CdTe QDs. The other flavonoids do not interact with the probe at 10 -5 molL -1 level. In CTAB organized dispersions, K s 3-hydroxyflavone >K s 7-hydroxyflavone >K s flavona >K s rutin in the range from 1.0×10 -6 molL -1 to 1.2×10 -5 molL -1 for flavones and of 1.0×10 -6 molL -1 to 1.0×10 -5 molL -1 for rutin. Dynamic light scattering, conductometric measurements and microenvironment polarity studies were employed to elucidate the QDs-flavonoids interaction in systems containing CTAB. The quenching can be attributed to the preferential solubility of hydrophobic flavonoid in the palisade layer of the CTAB aggregates adsorbed on the surface of the 3MPA CdTe QDs., (Copyright © 2016 Elsevier B.V. All rights reserved.)