A Turn-On Fluorescent Sensor for Sensitive and Selective Detection of Sodium Dodecyl Sulfate Based on the Eosin Y/Polyethyleneimine System

Placenta Powder-Infused Thiol-Ene PEG Hydrogels as Potential Tissue Engineering Scaffolds

Human placenta is a source of extracellular matrix for tissue engineering. In this study, placenta powder (PP), made from decellularized human placenta, was physically incorporated into synthetic poly(ethylene glycol) (PEG)-based hydrogels via UV-initiated thiol-ene coupling (TEC). The PP-incorporated PEG hydrogels (MoDPEG+) showed tunable storage moduli ranging from 1080 ± 290 to 51,400 ± 200 Pa. The addition of PP (1, 4, or 8 wt %) within the PEG hydrogels increased the storage moduli, with the 8 wt % PP hydrogels showing the highest storage moduli. PP reduced the swelling ratios compared with the pristine hydrogels (MoDPEG). All hydrogels showed good biocompatibility in vitro toward human skin cells and murine macrophages, with cell viability above 91%. Importantly, cells could adhere and proliferate on MoDPEG+ hydrogels due to the bioactive PP, while MoDPEG hydrogels were bio-inert as cells moved away from the hydrogel or were distributed in a large cluster on the hydrogel surface. To showcase their potential use in application-driven research, the MoDPEG+ hydrogels were straightforwardly (i) 3D printed using the SLA technique and (ii) produced via high-energy visible light (HEV-TEC) to populate damaged soft-tissue or bone cavities. Taking advantage of the bioactivity of PP and the tunable physicochemical properties of the synthetic PEG hydrogels, the presented MoDPEG+ hydrogels show great promise for tissue regeneration.

Whole-cell electric sensor for determination of sodium dodecyl sulfate

Linear alkyl sulfates are a major class of surfactants that have large-scale industrial application and thus wide environmental release. These organic pollutants threaten aquatic environments and other environmental compartments. We show the promise of the use of a whole-cell electric sensor in the analysis of low or residual concentrations of sodium dodecyl sulfate (SDS) in aqueous solutions. On the basis of bioinformatic analysis and alkylsulfatase activity determinations, we chose the gram-negative bacterium Herbaspirillum lusitanum, strain P6–12, as the sensing element. Strain P6–12 could utilize 0.01–400 mg/L of SDS as a growth substrate. The electric polarizability of cell suspensions changed at all frequencies used (50–3000 kHz). The determination limit of 0.01 mg/L is much lower than the official requirements for the content of SDS in potable and process water (0.5 and 1.0 mg/L, respectively), and the analysis takes about 1–5 min. The promise of H. lusitanum P6–12 for use in the remediation of SDS-polluted soils is discussed.

A ratiometric fluorescence strategy based on polyethyleneimine surface-modified carbon dots and Eosin Y for the ultrasensitive determination of protamine and trypsin

A ratiometric fluorescent nanoprobe for protamine and trypsin detection with excellent biocompatibility and high sensitivity was successfully constructed based on CDs-PEI and Eosin Y.

A cationic fluorescent probe for highly selective detection of sodium dodecyl sulfate (SDS) by electrostatic and hydrophobic self-assembly

Sodium dodecyl sulfate (SDS) has a wide range of applications in the chemical industry due to its excellent characteristics including good emulsification, foaming, water solubility and stability, easy synthesis and low price. However, it is a kind of anionic surfactant which is slightly toxic to the human body, and use of a large amount will cause potential pollution of the environment. Therefore, the development of a simple method to realize the monitoring of SDS in the environment is of great significance. Herein, a cationic fluorescent probe was prepared by the condensation reaction between 4-di-p-tolylamino-benzaldehyde and 3-ethylbenzothiazolium iodide. It can be used for the quantitative determination of SDS in the range of 5-50 μM showing red fluorescence and high selectivity by forming banded assemblies. This work provides an effective tool based on a new strategy for the detection of SDS.

A resonance Rayleigh scattering and fluorescence quenching dual-channel sensor for sensitive detection of chitosan based on Eosin Y

The sensitive chitosan (CTS) detection methods based on the resonance Rayleigh scattering (RRS) quenching method and fluorescence quenching of Eosin Y were put forward. In the HAC-NaAC buffer solution, Eosin Y interacted with Triton X-100 to generate the binary complex which served as the RRS spectral probe. When CTS was interacted with the binary complex, the RRS intensity decreased with the increase of CTS. At the same time, the fluorescence intensity of Eosin Y decreased in the presence of Triton X-100, and the fluorescence intensity of "Eosin Y+Triton X-100" system further decreased when CTS was added. So it was further proved that there was a forming complex in "Eosin Y+Triton X100+CTS" system. The interaction was characterized by zeta potential, RRS, fluorescence spectrum, and UV-Vis spectroscopy. Under optimal conditions, there was a good linear relationship between the RRS decreased intensity (ΔI) and the concentration of CTS in the range of 0.05-1.30 μg/mL, with a regression equation of ΔI = 1325c + 73.66 and correlation coefficient (R²) of 0.9907. The detection limit was 0.0777 μg/mL. Likewise, the linear range of the fluorescence quenching was 0.03-1.30 μg/mL; the regression equation was ΔF = 1926c + 294.0 with R² = 0.9800 under fluorescence quenching. The detection limit was 0.0601 μg/mL. Therefore, the dual-channel sensor for the determination of CTS was applied to the health products, and the results were satisfactory. The t test result showed that there was no statistical difference between the two methods.

Transcription factor based whole-cell biosensor for specific and sensitive detection of sodium dodecyl sulfate

Extensive use of Sodium Dodecyl Sulfate (SDS) in households, agricultural operations, and industries is leading to its subsequent disposal in waterways. There is an apprehension of the adverse effect of such detergents on various living organisms. Thus, an efficient, specific, and simple detection method to monitor SDS reliably in the environment is needed. We used sdsB1 activator protein and SDS-responsive promoter of sdsA1 gene along with Green Fluorescent Protein (GFP) to construct a novel SDS biosensor in Pseudomonas aeruginosa chassis. The GFP intensity of the biosensor showed a linear relationship (R² = 0.99) from 0.4 to 62.5 ppm of SDS with a detection limit of 0.1 ppm. This biosensor is highly specific for SDS and has minimal interference from other detergents, metals, and inorganic ions. The biosensor showed a satisfactory and reproducible recovery rate for the detection of SDS in real samples. Overall, this is a low cost, easy-to-use, selective, and reliable biosensor for monitoring SDS in the environment.

A ratiometric fluorometric heparin assay based on the use of CdTe and polyethyleneimine-coated carbon quantum dots

CdTe quantum dots (QDs) were integrated with polyethyleneimine-coated carbon dots (PEI-CDs) to form a dually emitting probe for heparin. The red fluorescence of the CdTe QDs is quenched by the PEI-CDs due to electrostatic interactions. In the presence of heparin, the blue fluorescence of PEI-CDs remains unaffected, while its quenching effect on the fluorescence of CdTe QDs is strongly reduced. A ratiometric fluorometric assay was worked out. The ratio of the fluorescences at 595 and 436 nm serves as the analytical signal. Response is linear in the concentration range of 50-600 ng·mL^-1 (0.1-1.2 U·mL^-1) of heparin. The limit of detection is 20 ng·mL^-1 (0.04 U·mL^-1). This makes the method a valuable tool for heparin monitoring during postoperative and long-term care. This assay is relatively free from the interference by other analogues which commonly co-exist with heparin in samples, and it is more robust than single-wavelength based assays. Graphical abstract In the presence of heparin, the fluorescence of polyethyleneimine-coated carbon dots (PEI-CDs) at 436 nm remains unaffected, while its quenching effect on the fluorescence of CdTe at 595 nm is strongly reduced.

A resonance Rayleigh scattering sensor for sensitive differentiation of telomere DNA length and monitoring special motifs (G-quadruplex and i-motif) based on the Ag nanoclusters and NAND logic gate responding to chemical input signals

Background

Differentiation of telomere length is of vital importance because telomere length is closely related with several deadly diseases such as cancer. Additionally, G-quadruplex and i-motif formation in telomeric DNA have been shown to act as a negative regulator of telomere elongation by telomerase in vivo and are considered as an attractive drug target for cancer chemotherapy.

Results

In this assay, Ag nanoclusters templated by hyperbranched polyethyleneimine (PEI–Ag NCs) are designed as a new novel resonance Rayleigh scattering (RRS) probe for sensitive differentiation of telomere length and monitoring special motifs (G-quadruplex and i-motif). In this assay, free PEI–Ag NC probe or DNA sequence alone emits low intensities of RRS, while the formation of PEI–Ag NCs/DNA complexes yields greatly enhanced RRS signals; however, when PEI–Ag NCs react with G-quadruplex or i-motif, the intensities of RRS exhibit slight changes. At the same concentration, the enhancement of RRS signal is directly proportional to the length of telomere, and the sensitivity of 64 bases is the highest with the linear range of 0.3–50 nM (limit of detection 0.12 nM). On the other hand, due to the conversion of telomere DNA molecules among multiple surrounding conditions, a DNA logic gate is developed on the basis of two chemical input signals (K⁺ and H⁺) and a change in RRS intensity as the output signal.

Conclusion

Our results indicate that PEI–Ag NCs can serve as a novel RRS probe to identify DNA length and monitor G-quadruplex/i-motif through the different increasing degrees of RRS intensity. Meanwhile, the novel attributes of the nanoprobe stand superior to those involving dyes or labeled DNA because of no chemical modification, low cost, green, and high efficiency.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0407-5) contains supplementary material, which is available to authorized users.

Engineered polymeric amphiphiles self-assembling into nanostructures and acting as efficient gene and drug carriers

Nonviral gene delivery systems are finding widespread use due to their safety, rapid and economical production, and ease of modification. In this work, series of N-alkyl-substituted linear polyethylenimine (CP) polymers have been synthesized, characterized, and investigated about how degree of substitution (hydrophobic-hydrophilic balance) (i.e. N-alkylation) influenced the transfection efficiency. Mobility shift assay demonstrated efficient binding of plasmid DNA (pDNA). Transfection efficiency and cytotoxicity of CP polymers were assessed in vitro, which revealed that all the formulations exhibited higher transfection activity than linear polyethylenimine (lPEI) and commercial transfection reagents, Lipofectamine and Superfect, with negligible toxicity (MTT assay). In the projected series, one of the formulations, CP-3-pDNA complex, displayed the highest transfection efficiency (∼1.6-12 folds vs. lPEI and commercial transfection reagents) and effectively carried GFP-specific siRNA inside the cells as monitored by measuring the suppression in the gene expression of the target gene. Further, flow cytometry experiments confirmed that CP-3-pDNA complex transfected the highest number of cells. Besides, CP-3 was also evaluated in terms of its capability to entrap hydrophobic drug molecules. The results showed that it efficiently encapsulated an anti-cancer drug, etoposide, and released it in a controlled fashion over a period of time. Altogether, the data support that CP-3 is a promising vector for nucleic acid as well as hydrophobic drug delivery.

A convenient method for determination of quizalofop-p-ethyl based on the fluorescence quenching of eosin Y in the presence of Pd(II)

A convenient fluorescence quenching method for determination of Quizalofop-p-ethyl(Qpe) was proposed in this paper. Eosin Y(EY) is a red dye with strong green fluorescence (λex/λem=519/540nm). The interaction between EY, Pd(II) and Qpe was investigated by fluorescence spectroscopy, resonance Rayleigh scattering(RRS) and UV-Vis absorption. Based on changes in spectrum, Pd(II) associated with Qpe giving a positively charged chelate firstly, then reacted with EY through electrostatic and hydrophobic interaction formed ternary chelate could be demonstrated. Under optimum conditions, the fluorescence intensity of EY could be quenched by Qpe in the presence of Pd(II) and the RRS intensity had a remarkable enhancement, which was directly proportional to the Qpe concentration within a certain concentration range, respectively. Based on the fluorescence quenching of EY-Pd(II) system by Qpe, a novel, convenient and specific method for Qpe determination was developed. To our knowledge, this is the first fluorescence method for determination of Qpe was reported. The detection limit for Qpe was 20.3ng/mL and the quantitative determination range was 0.04-1.0μg/mL. The method was highly sensitive and had larger detection range compared to other methods. The influence of coexisting substances was investigated with good anti-interference ability. The new analytical method has been applied to determine of Qpe in real samples with satisfactory results.

Carbon quantum dots prepared with polyethyleneimine as both reducing agent and stabilizer for synthesis of Ag/CQDs composite for Hg2+ ions detection

A stable silver nanoparticles/carbon quantum dots (Ag/CQDs) composite was prepared by using CQDs as reducing and stabilizing agent. The CQDs synthesized with polyethyleneimine (PEI) showed an extraordinary reducibility. When Hg²⁺ was presented in the Ag/CQDs composite solution, a color change from yellow to colorless was observed, accompanied by a shift of surface plasmon resonance (SPR) band and decrease in absorbance of the Ag/CQDs composite. On the basis of the further studies on TEM, XPS and XRD analysis, the possible mechanism is attributed to the formation of a silver-mercury amalgam. Hence, a two dimensional sensing platform for Hg²⁺ detection was constructed upon the Ag/CQDs composite. Based on the change of absorbance, a good linear relationship was obtained from 0.5 to 50μM for Hg²⁺. And the limit of detection for Hg²⁺ was as low as 85nM, representing high sensitivity to Hg²⁺. More importantly, the proposed method also exhibits a good selectivity toward Hg²⁺ over other metal ions. Besides, this strategy demonstrates practicability for the detection of Hg²⁺ in real water samples with satisfactory results.

A novel electrochemical sensing platform based on Pt/PPy/Eosin-Y for the determination of cadmium

In this research work, a novel sensing platform has been designed for the determination of cadmium (Cd²⁺) based on the modification of a bare platinum (Pt) electrode with pyrrole (Py) and Eosin-Y (yellowish) using electro-polymerization and electro-deposition procedures.

Quantitative determination and toxicity evaluation of 2,4-dichlorophenol using poly(eosin Y)/hydroxylated multi-walled carbon nanotubes modified electrode

This study aimed at developing simple, sensitive and rapid electrochemical approach to quantitatively determine and assess the toxicity of 2,4-dichlorophenol (2,4-DCP), a priority pollutant and has potential risk to public health through a novel poly(eosin Y, EY)/hydroxylated multi-walled carbon nanotubes composite modified electrode (PEY/MWNTs-OH/GCE). The distinct feature of this easy-fabricated electrode was the synergistic coupling effect between EY and MWNTs-OH that enabled a high electrocatalytic activity to 2,4-DCP. Under optimum conditions, the oxidation peak current enhanced linearly with concentration increasing from 0.005 to 0.1 μM and 0.2 to 40.0 μM, and revealed the detection limit of 1.5 nM. Moreover, the PEY/MWNTs-OH/GCE exhibited excellent electrocatalytic activity toward intracellular electroactive species. Two sensitive electrochemical signals ascribed to guanine/xanthine and adenine/hypoxanthine in human hepatoma (HepG2) cells were detected simultaneously. The sensor was successfully applied to evaluate the toxicity of 2,4-DCP to HepG2 cells. The IC₅₀ values based on the two electrochemical signals are 201.07 and 252.83 μM, respectively. This study established a sensitive platform for the comprehensive evaluation of 2,4-DCP and posed a great potential to simplify environmental toxicity monitoring.

Highly sensitive and selective fluorescent assay for guanine based on the Cu(2+)/eosin Y system

A fluorescent probe has been developed for the determination of guanine based on the quenched fluorescence signal of Cu(2+)/eosin Y. Cu(2+) interacted with eosin Y, resulting in fluorescence quenching. Subsequently, with the addition of guanine to the Cu(2+)/eosin Y system, guanine reacted with Cu(2+) to form 1:1 chelate cation, which further combined with eosin Y to form a 1:1 ternary ion-association complex by electrostatic attraction and hydrophobic interaction, resulting in significant decrease of the fluorescence. Hence, a fluorescent system was constructed for rapid, sensitive and selective detection of guanine with a detection limit as low as 1.5 nmol L(-1) and a linear range of 3.3-116 nmol L(-1). The method has been applied satisfactorily to the determination of guanine in DNA and urine samples with the recoveries from 98.7% to 105%. This study significantly expands the realm of application of ternary ion-association complex in fluorescence probe.

Investigation of the fluorescence quenching behavior of PEI-doped silica nanoparticles and its applications

A simple and feasible method for overcoming the fluorescence quenching effect of PEI on fluorophores (eosin Y was chosen as the model dye) was designed for the first time.

Polyethyleneimine as a novel desorbent for anionic organic dyes on layered double hydroxide surface

Polyethyleneimine (PEI) is a positively charged polymer with hydrogen-bonding sites and hydrophobic chains. Therefore, it has been clearly established as an efficient adsorbent by means of these native properties in the literatures. However, there is apparently no good reason to disregard the use of PEI as a desired desorbent. Herein, using methyl orange as a model anionic dye, we investigated the desorption performances of PEI toward anionic dyes adsorbed on the surface of CO3-layered double hydroxides (LDHs) in a wide range of pH values. The experiment results showed that the positively charged PEI had very strong desorption capacity for anionic dyes at low pH values (<9.5) through electrostatic attraction between PEI and methyl orange because of the high degree of protonation of PEI. At high pH values (>9.5), PEI existed as neutral molecule, it could desorb methyl orange via hydrogen bonding between the amino groups of it and sulfonate group of methyl orange; simultaneously, the anion-exchange process occurred between abundant hydroxyl anions and anionic methyl orange. The adsorption capacity of the used LDH adsorbent was about 80% after five cycles of adsorption-desorption-regeneration, which was much higher than that conducted by 0.1M NaOH solution. These findings suggested that PEI could be regarded as a promising desorbent for enriching anionic dyes in wastewater and regenerating LDHs through surface adsorption-desorption cycles.

An eosin Y-based "turn-on" fluorescent sensor for detection of perfluorooctane sulfonate

In this paper, a novel sensing method with a higher sensitivity of perfluorooctane sulfonate (PFOS) than perfluorooctanoic acid (PFOA) has been proposed detection of PFOS in aqueous solution replying on the "off-on" switch of eosin Y/polyethyleneimine (PEI)/PFOS fluorescence system due to the higher affinity of PEI to PFOS than eosin Y. In pH 7.0 Britton-Robinson buffer solution, eosin Y reacts with protonated PEI to form complex by electrostatic attraction, which leads to a strong fluorescence quenching of the eosin Y. When PFOS presents, the fluorescence of eosin Y is recover due to the electrostatic and hydrophobic interactions between PFOS and PEI. The recovered fluorescence intensity is proportional to the concentration of PFOS in the ranging from 0 to 2.0×10(-6) mol/L with the limit of detection (LOD, 3σ) being 1.5×10(-8) mol/L without preconcentration. In this study, the optimum reaction conditions and the interferences of foreign substances were investigated. In addition, the effects of PFOA, the analog of PFOS, on the fluorescence recovery of the system were also studied. The presented approach has been successfully used to detect PFOS in real samples with RSD ⩽2.9%.