A dual-responsive biosensor for blood lead detection

Fluorescence-colorimetric dual detection method for quantitative detection of uric acid in urine based on the competitive oxidation between cerium (IV) and o-phenylenediamine induced by target substances

A dual detection method combining fluorescence and colorimetry used for measuring uric acid (UA) has been developed. Ce4+ can undergo an oxidation reaction with o-phenylenediamine (OPD) to generate 2,3-diaminophenazine (oxOPD), which exhibits a yellow color and has UV-visible light absorption properties. When UA is introduced into the reaction system, it effectively inhibits the oxidation process between Ce4+ and OPD, simultaneously resulting in the emergence of a new emission peak at 500 nm in the solution. It is worth noting that both the degree of enhancement in the fluorescence signal intensity at 500 nm and the decrease in the absorbance of oxOPD in the detection system are directly related to the concentration of UA added. Based on this phenomenon, we have successfully designed and implemented a sensitive, simple, and economically applicable fluorescence and colorimetric dual detection method for UA detection. The linear range of the fluorescence detection method is 160-400 μM, with a limit of detection (LOD) of 11.31 μM, while the colorimetric method exhibits a linear range of 5-150 μM and an LOD of 3.55 μM. The fluorescence and colorimetric dual detection method has been successfully applied to the quantitative detection of UA in spiked human urine samples. The recovery rate of fluorescence detection is 95.32-104.08 %, and the relative standard deviation (RSD) is 1.48-5.37 %. The recovery rate of colorimetric detection is 94.40-103.69 %, and the RSD is 1.30-4.11 %. This achievement indicates that it has broad potential application prospects in the field of clinical testing.

Biosynthesis of Indigo Dyes and Their Application in Green Chemical and Visual Biosensing for Heavy Metals

Fermentative production of natural colorants using microbial strains has emerged as a cost-effective and sustainable alternative to chemical synthesis. Visual pigments are used as signal outputs in colorimetric bacterial biosensors, a promising method for monitoring environmental pollutants. In this study, we engineered four self-sufficient indigo-forming enzymes, including HbpAv, bFMO, cFMO, and rFPMO, in a model bacterium E. coli. TrxA-bFMO was chosen for its strong ability to produce indigo under T7 lac and mer promoters' regulation. The choice of bacterial hosts, the supplementation of substrate l-tryptophan, and ventilation were crucial factors affecting indigo production. The indigo reporter validated the biosensors for Hg(II), Pb(II), As(III), and Cd(II). The biosensors reported Hg(II) as low as 14.1 nM, Pb(II) as low as 1.5 nM, and As(III) as low as 4.5 nM but increased to 25 μM for Cd(II). The detection ranges for Hg(II), Pb(II), As(III), and Cd(II) were quantified from 14.1 to 225 nM, 1.5 to 24.4 nM, 4.5 to 73.2 nM, and 25 to 200 μM, respectively. The sensitivity, responsive concentration range, and selectivity are comparable to β-galactosidase and luciferase reporter enzymes. This study suggests that engineered enzymes for indigo production have great potential for green chemical synthesis. Additionally, heterologous biosynthesis of indigo production can lead to the development of novel, low-cost, and mini-equipment bacterial biosensors with zero background noise for visual monitoring of pollutant heavy metals.

Pb2+ Ion Sensors Employing Gold Etching Process: Comparative Investigation on Au Nanorods and Au Nanotriangles

The leaching phenomenon of gold (Au) nanomaterials by Pb2+ ions in the presence of 2-mercaptoethanol (2-ME) and thiosulfate (S2O32- ion) has been systematically applied to a Pb2+ ion sensor. To further investigate the role of Pb2+ ions in sensors containing Au nanomaterials, we revisited the leaching conditions for Au nanorods and compared them with the results for Au nanotriangles. By monitoring the etching rate, it was revealed that Pb2+ ions were important for the acceleration of the etching rate mainly driven by 2-ME and S2O32- pairs, and nanomolar detection of Pb2+ ions were shown to be promoted through this catalytic effect. Using the etchant, the overall size of the Au nanorods decreased but showed an unusual red-shift in UV-Vis spectrum indicating increase of aspect ratio. Indeed, the length of Au nanorods decreased by 9.4% with the width decreasing by 17.4% over a 30-min reaction time. On the other hand, the Au nanotriangles with both flat sides surrounded mostly by dense Au{111} planes showed ordinary blue-shift in UV-Vis spectrum as the length of one side was reduced by 21.3%. By observing the changes in the two types of Au nanomaterials, we inferred that there was facet-dependent alloy formation with lead, and this difference resulted in Au nanotriangles showing good sensitivity, but lower detection limits compared to the Au nanorods.

Biomedical applications of engineered heparin-based materials

Heparin is a negatively charged polysaccharide with various chain lengths and a hydrophilic backbone. Due to its fascinating chemical and physical properties, nontoxicity, biocompatibility, and biodegradability, heparin has been extensively used in different fields of medicine, such as cardiovascular and hematology. This review highlights recent and future advancements in designing materials based on heparin for various biomedical applications. The physicochemical and mechanical properties, biocompatibility, toxicity, and biodegradability of heparin are discussed. In addition, the applications of heparin-based materials in various biomedical fields, such as drug/gene delivery, tissue engineering, cancer therapy, and biosensors, are reviewed. Finally, challenges, opportunities, and future perspectives in preparing heparin-based materials are summarized.

Designed bacteria based on natural pbr operons for detecting and detoxifying environmental lead: A mini-review

Lead (Pb), a naturally occurring element, is redistributed in the environment mainly due to anthropogenic activities. Pb pollution is a crucial public health problem worldwide due to its adverse effects. Environmental bacteria have evolved various protective mechanisms against high levels of Pb. The pbr operon, first identified in Cupriavidus metallidurans CH34, encodes a unique Pb(II) resistance mechanism involving transport, efflux, sequestration, biomineralization, and precipitation. Similar pbr operons are gradually found in diverse bacterial strains. This review focuses on the pbr-encoded Pb(II) resistance system. It summarizes various whole-cell biosensors harboring artificially designed pbr operons for Pb(II) biomonitoring with fluorescent, luminescent, and colorimetric signal output. Optimization of genetic circuits, employment of pigment-based reporters, and screening of host cells are promising in improving the sensitivity, selectivity, and response range of whole-cell biosensors. Engineered bacteria displaying Pb(II) binding and sequestration proteins, including PbrR and its derivatives, PbrR2 and PbrD, for adsorption are involved. Although synthetic bacteria show great potential in determining and removing Pb at the nanomolar level for environmental protection and food safety, some challenges must be addressed to meet demanding application requirements.

Target-triggered 'colorimetric-fluorescence' dual-signal sensing system based on the versatility of MnO2 nanosheets for rapid detection of uric acid

A simple dual-signal assay that combined colorimetric and fluorometric strategy for uric acid (UA) rapid detection was designed based on the versatility of facile synthesized MnO2 nanosheet. The oxidization of 3,3',5,5'-tetramethylbenzidine (TMB) and the fluorescence quenching of quantum dots (QDs) occurred simultaneously in the presence of MnO2 nanosheet. UA could decompose MnO2 nanosheet into Mn2+, resulting in the fluorescence recovery of QDs, along with the fading of the blue color of ox TMB. Based on the principles above, the detection of UA could be realized by the change of the dual signals (colorimetric and fluorometric). The linear range of the colorimetric mode was 5-60 μmol L-1, and the limit of detection (LOD) was 2.65 μmol L-1; the linear range of the fluorescence mode was wide at 5-120 μmol L-1, and the LOD could be as low as 1.33 μmol L-1. The method was successfully used for analyzing UA levels in human serum samples, indicating that this new dual-signal method could be applied in clinical diagnosis.

Detection Techniques for Lead Ions in Water: A Review

Lead pollution has increasingly become the focus of environmental pollution, which is a great harm to the ecological environment and human health. Strict control of the emission of lead pollutants and accurate monitoring of lead are very important. The lead ion detection technologies are introduced here, including spectrophotometry, electrochemical method, atomic absorption spectrometry, and other detection methods, and the methods' applicability, the advantages, and disadvantages are discussed. The detection limits of voltammetry and atomic absorption spectrometry are as low as 0.1 μg/L, and those of atomic absorption spectrometry are as low as 2 μg/L. The detection limit of photometry is higher (0.01 mg/L), but this method can be achieved in most laboratories. The application of different extraction pretreatment technologies in lead ion detection is introduced. The new technologies develop at home and abroad, such as precious metal nanogold technology, paper microfluidic technology, fluorescence molecular probe technology, spectroscopy, and other emerging technologies in recent years, are reviewed, and the principle and application of various technologies are expounded.

Advances from conventional to real time detection of heavy metal(loid)s for water monitoring: An overview of biosensing applications

The rapid growth of the industrial sector has expedited the accumulation of heavy metal(loid)s in the environment at hazardous levels. The elements such as arsenic, lead, mercury, cadmium and chromium are lethal in terms of toxicity with severe health impacts. With issues like water scarcity, limitations in wastewater treatment, and costs pertaining to detection in environmental matrices; their rapid and selective detection for reuse of effluents is of the utmost priority. Biosensors are the futuristic tool for the accurate qualitative and quantitative analysis of a specific analyte and integrate biotechnology, microelectronics and nanotechnology to fabricate a miniaturized device without compromising the sensitivity, specificity and accuracy. The characteristic features of supporting matrix largely affect the biosensing ability of the device and incorporation of highly sensitive and durable metal organic frameworks (MOFs) are reported to enhance the efficiency of advanced biosensors. Electrochemical biosensors are among the most widely developed biosensors for the detection of heavy metal(loids), while direct electron transfer approach from the recognition element to the electrode has been found to decrease the chances of interference. This review provides an insight into the recent progress in biosensor technologies for the detection of prevalent heavy metal(loid)s; using advanced support systems such as functional metal-based nanomaterials, carbon nanotubes, quantum dots, screen printed electrodes, glass beads etc. The review also delves critically in comparison of various techno-economic studies and the latest advances in biosensor technology.

Electrochemical sensor based on micromotor technology for detection of Ox-LDL in whole blood

Detecting the concentration of oxidized low-density lipoprotein (Ox-LDL) in whole blood is of great significance for monitoring the development of atherosclerosis. In order to simplify the complex processing steps of blood sample before the detection, an electrochemical sensor based on micromotor technology was designed, which was called magnesium (Mg)-Fe₃O₄@ prussian blue (PB)@ antibody of Ox-LDL (Ab)@ bovine serum albumin (BSA). The active capture of Ox-LDL in whole blood can be realized by the help of the movement of Mg microsphere with the driving force of H₂. Then the captured Ox-LDL was collected on the surface of the magnetic glassy carbon electrode (MGCE) by self-made funnel device, and the content of Ox-LDL was detected by electrochemical workstation in the way of chronoamperometry (i-t). Due to the application of micromotor, the electrochemical sensor proposed in this study had good detection efficiency for Ox-LDL in whole blood with range from 1 × 10^-2 μg/mL to 10 μg/mL, and the limit of detection (LOD) towards Ox-LDL was 9.80 × 10^-4 μg/mL. The electrochemical sensor based on micromotor technology provides a rapid, effective, and sensitive method for the detection of Ox-LDL in whole blood.

Non-invasive electrochemistry-driven metals tracing in human biofluids

Wearable analytical devices represent the future for fast, de-centralized, and human-centered health monitoring. Electrochemistry-based platforms have been highlighted as the role model for future developments amid diverse strategies and transduction technologies. Among the various relevant analytes to be real-time and non-invasively monitored in bodily fluids, we review the latest wearable achievements towards determining essential and toxic metals. On-skin measurements represent an excellent possibility for humankind: real-time monitoring, digital/fast communication with specialists, quick interventions, removing barriers in developing countries. In this review, we discuss the achievements over the last 5 years in non-invasive electrochemical platforms, providing a comprehensive table for quick visualizing the diverse sensing/technological advances. In the final section, challenges and future perspectives about wearables are deeply discussed.

Sensing and bioimaging of lead ions in intracellular cancer cells and biomedical media using amine-functionalized silicon quantum dots fluorescent probe

A novel amine-functionalized silica quantum dots (SiQDs) fluorescent nanoprobe was developed for sensing of lead concentration in water, plasma and cell lysate. In addition, the developed probe was utilized for bioimaging of intracellular lead ions in HT 29 cancer cells. The amine-functionalized nanoprobe exhibited fluorescence emission at 445 nm under excitation at 355 nm. Upon addition of lead ions, the fluorescence of SiQDs linearly enhanced from 50 ng/mL to 5 µg/mL and 50 ng/mL to 25 µg/mL for plasma and standard media, respectively. The synthesis and fabrication of this probe are simple and serves high sensitivity with a limit of detection down to around 20 ng/mL. In the presence of various molecular and ion interfering, reliable results are obtained, confirming the specificity of the nanoprobe for lead ion detection. Meanwhile, amine-functionalized SiQD-based nanoprobe exhibits excellent cell membrane-permeability and biocompatibility. Thus, this probe is utilized for lead tracing in HT 29 cancer live cells. Fluorescent microscopy results confirmed the attachment of the produced nanomaterials to the HT 29 cancer cells.

Versatile artificial mer operons in Escherichia coli towards whole cell biosensing and adsorption of mercury

Mercury exists naturally and mainly as a man-made pollutant in the environment, where it exerts adverse effects on local ecosystems and living organisms. It is important to develop an appropriate synthetic biological device that recognizes, detects and removes the bioavailable fraction of environmental mercury. Both single-signal and double-signal output mercury biosensors were assembled using a natural mer operon as a template. Selectivity and sensitivity of whole-cell biosensors based on artificial mer operons were determined. Three whole-cell biosensors were highly stable at very high concentrations of mercuric chloride, and could detect bioavailable Hg(II) in the concentration range of 6.25-200 μM HgCl2. A novel Hg(II) bioadsorption coupled with biosensing artificial mer operon was assembled. This would allow Hg(II)-induced Hg(II) binding protein cell surface display and green fluorescence emission to be achieved simultaneously while retaining the linear relationship between fluorescent signal and Hg(II) exposure concentration. The present study provides an innovative way to simultaneously detect, quantify, and remove bioavailable heavy metal ions using an artificially reconstructed heavy metal resistance operon.

Research progress of using micro/nanomotors in the detection and therapy of diseases related to the blood environment

Micro/nanomotors bring new possibilities for the detection and therapy of diseases related to the blood environment with their unique motion effect. This work reviews the research progress of using micro/nanomotors in the detection and therapy of diseases related to the blood environment. First, we outline the advantages of using micro/nanomotors in blood-related disease detection. To be specific, the motion capability of micro/nanomotors can increase plasma or blood fluid convection and accelerate the interaction between the sample and the capture probe. This allows the effective reduction of the amount of reagents and treatment steps. Therefore, the application of micro/nanomotors significantly improves the analytical performance. Second, we discuss the key challenges and future prospects of micro/nanomotors in the treatment of blood-environment related diseases. It is very important to design a unique treatment plan according to the etiology and specific microenvironment of the disease. The next generation of micro/nanomotors is expected to bring exciting progress to the detection and therapy of blood-environment related diseases.

Recent Advances in Nanotechnology-Based Biosensors Development for Detection of Arsenic, Lead, Mercury, and Cadmium

Heavy metals cause considerable environmental pollution due to their extent and non-degradability in the environment. Analysis and trace levels of arsenic, lead, mercury, and cadmium as the most toxic heavy metals show that they can cause various hazards in humans' health. To achieve rapid, high-sensitivity methods for analyzing ultra-trace amounts of heavy metals in different environmental and biological samples, novel biosensors have been designed with the participation of strategies applied in nanotechnology. This review attempted to investigate the novel, sensitive, efficient, cost-benefit, point of care, and user-friendly biosensors designed to detect these heavy metals based on functional mechanisms. The study's search strategies included examining the primary databases from 2015 onwards and various keywords focusing on heavy metal biosensors' performance and toxicity mechanisms. The use of aptamers and whole cells as two important bio-functional nanomaterials is remarkable in heavy metal diagnostic biosensors' bioreceptor design. The application of hybridized nanomaterials containing a specific physicochemical function in the presence of a suitable transducer can improve the sensing performance to achieve an integrated detection system. Our study showed that in addition to both labeled and label-free detection strategies, a wide range of nanoparticles and nanocomposites were used to modify the biosensor surface platform in the detection of heavy metals. The detection limit and linear dynamic range as an essential characteristic of superior biosensors for the primary toxic metals are studied. Furthermore, the perspectives and challenges facing the design of heavy metal biosensors are outlined. The development of novel biosensors and the application of nanotechnology, especially in real samples, face challenges such as the capability to simultaneously detect multiple heavy metals, the interference process in complex matrices, the efficiency and stability of nanomaterials implemented in various laboratory conditions.

Nanomotor-based adsorbent for blood Lead(II) removal in vitro and in pig models

Blood lead (Pb(II)) removal is very important but challenging. The main difficulty of blood Pb(II) removal currently lies in the fact that blood Pb(II) is mainly complexed with hemoglobin (Hb) inside the red blood cells (RBCs). Traditional blood Pb(II) removers are mostly passive particles that do not have the motion ability, thus the efficiency of the contact between the adsorbent and the Pb(II)-contaminated Hb is relatively low. Herein, a kind of magnetic nanomotor adsorbent with movement ability under alternating magnetic field based on Fe₃O₄ nanoparticle modified with meso-2, 3-dimercaptosuccinic acid (DMSA) was prepared and a blood Pb(II) removal strategy was further proposed. During the removal process, the nanomotor adsorbent can enter the RBCs, then the contact probability between the nanomotor adsorbent and the Pb(II)-contaminated Hb can be increased by the active movement of nanomotor. Through the strong coordination of functional groups in DMSA, the nanomotor adsorbent can adsorb Pb(II), and finally be separated from blood by permanent magnetic field. The in vivo extracorporeal blood circulation experiment verifies the ability of the adsorbent to remove blood Pb(II) in pig models, which may provide innovative ideas for blood heavy metal removal in the future.

Erythrocyte Membrane-Wrapped Magnetic Nanotherapeutic Agents for Reduction and Removal of Blood Cr(VI)

The hazard of hexavalent chromium (Cr(VI)) from environmental pollution and medical implanted metal has been recognized widely. However, removal of trace amount of Cr(VI) in the blood circumstance faces tremendous difficulties for that most of Cr(VI) located in erythrocytes, thus there is almost no literature to report the removal of Cr(VI) in blood. Herein, a removal strategy, named as reduction-adsorption-separation, is proposed to realize the removal of Cr(VI) in blood. First, magnetic core-shell mesoporous nanocomposite is fabricated by using Fe₃O₄ nanoparticles as magnetic core and mesoporous silica (MS) as shell, hyperbranched polyamide (HPA) as mesoporous channel modifier and ascorbic acid (ASC) as the reductant drug loaded in the mesoporous channels, which is also denoted as Fe/MS/HPA/ASC. Then, on the basis of the bionic idea, the erythrocyte membrane (EM)-wrapped Fe/MS/HPA/ASC to protect ASC from deactivation is obtained and named as the therapeutic agent (Fe/MS/HPA/ASC@EM). During removal process, the therapeutic agent can enter in erythrocytes to use ASC to reduce Cr(VI) to Cr(III) and HPA in mesoporous channels to adsorb Cr(III) and can then be recollected from blood by magnetic separation. Finally, an animal model of blood Cr(VI) poisoning is constructed and used to test the removal ability of Cr(VI) from pig blood in vivo, verifying the effectiveness of this blood Cr(VI) removal strategy, providing a possible way to design more efficient and biosafe therapeutic agents for blood purification.