In vivo detection of glutathione disulfide and oxidative stress monitoring using a biosensor

Glutathione Fluorescence Sensing Based on a Co-Doped Carbon Dot/Manganese Dioxide Nanocoral Composite

Glutathione (GSH) is an antioxidant thiol that has a vital role in the pathogenesis of various human diseases such as cardiovascular disease and cancer. Hence, it is necessary to study effective methods of GSH evaluation. In our work, an effective GSH sensor based on a nitrogen and phosphorus co-doped carbon dot (NPCD)-MnO₂ nanocoral composite was fabricated. In addition to utilizing the strong fluorescence of the NPCDs, we utilized the reductant ability of the NPCDs themselves to form MnO₂ and then the NPCD-MnO₂ nanocoral composite from MnO₄^-. The characteristics of the nanocoral composite were analyzed using various electron microscopy techniques and spectroscopic techniques. The overlap between the absorption spectrum of MnO₂ and the fluorescence emission spectrum of the NPCDs led to effective fluorescence resonance energy transfer (FRET) in the nanocoral composite, causing a decrease in the fluorescent intensity of the NPCDs. A linear recovery of the fluorescent intensity of the NPCDs was observed with the GSH level raising from 20 to 250 µM. Moreover, our GSH sensor showed high specificity and sensing potential in real samples with acceptable results.

Marine Biological Macromolecules as Matrix Material for Biosensor fabrication

The Ocean covers two-third of our planet and has great biological heterogeneity. Marine organisms like algae, vertebrates, invertebrates, and microbes are known to provide many natural products with biological activities as well as potent sources of biomaterials for therapeutic, biomedical, biosensors, and climate stabilization. Over the years, the field of biosensors have gained huge attention due to their extraordinary ability to provide early disease diagnosis, rapid detection of various molecules and substances along with long term monitoring. This review aims to focus on the properties and employment of various biomaterials (Carbohydrate polymers, proteins, polyacids etc) of marine origin such as Alginate, Chitin, Chitosan, Fucoidan, Carrageenan, Chondroitin Sulfate (CS), Hyaluronic acid (HA), Collagen, marine pigments, marine nanoparticles, Hydroxyapatite (HAp), Biosilica, lectins, and marine whole cell in the design and development of biosensors. Further, this review also covers the source of such marine biomaterials and their promising evolution in the fabrication of biosensors that are potent to be employed in the biomedical, environmental science and agricultural sciences domains. The use of such fabricated biosensors harness the system with excellent specificity, selectivity, biocompatibility, thermally stable and minimal cost advantages. This article is protected by copyright. All rights reserved.

Ultrasensitive Aptasensors for the Detection of Viruses Based on Opto-Electrochemical Readout Systems

Viral infections are becoming the foremost driver of morbidity, mortality and economic loss all around the world. Treatment for diseases associated to some deadly viruses are challenging tasks, due to lack of infrastructure, finance and availability of rapid, accurate and easy-to-use detection methods or devices. The emergence of biosensors has proven to be a success in the field of diagnosis to overcome the challenges associated with traditional methods. Furthermore, the incorporation of aptamers as bio-recognition elements in the design of biosensors has paved a way towards rapid, cost-effective, and specific detection devices which are insensitive to changes in the environment. In the last decade, aptamers have emerged to be suitable and efficient biorecognition elements for the detection of different kinds of analytes, such as metal ions, small and macro molecules, and even cells. The signal generation in the detection process depends on different parameters; one such parameter is whether the labelled molecule is incorporated or not for monitoring the sensing process. Based on the labelling, biosensors are classified as label or label-free; both have their significant advantages and disadvantages. Here, we have primarily reviewed the advantages for using aptamers in the transduction system of sensing devices. Furthermore, the labelled and label-free opto-electrochemical aptasensors for the detection of various kinds of viruses have been discussed. Moreover, numerous globally developed aptasensors for the sensing of different types of viruses have been illustrated and explained in tabulated form.

Nano-Bio-engineered Silk Matrix based Devices for Molecular Bioanalysis

Silk is a fibrous protein, has been a part of human lives for centuries and was used as suture and textile material. Silk is mainly produced by members of certain arthropods such as spiders, butterflies, mites, and moths. However, recent technological advances have revolutionized silk as a biomaterial for various applications ranging from heat sensors to robust fibers. The biocompatibility, mechanical resilience, and biodegradability of the material make it a suitable candidate for biomaterials. Silk can also be easily converted into several morphological forms, including fibers, films, sponges, and hydrogels. Provided these abilities, silk have received excellent traction from scientists worldwide for various developments, one of them being its use as a bio-sensor. The diversity of silk materials offers various options, giving scientists the freedom to choose from and personalize them as per their needs. In this review, we foremost look upon the composition, production, properties, and various morphologies of silk. The numerous applications of silk and its derivatives for fabricating biosensors to detect small molecules, macromolecules, and cells have been explored comprehensively. Also, the data from various globally developed sensors using silk have been described into organized tables for each category of molecules, along with their important analytical details. This article is protected by copyright. All rights reserved.

“Turn on” Fluorescence Sensor of Glutathione Based on Inner Filter Effect of Co-Doped Carbon Dot/Gold Nanoparticle Composites

Glutathione (GSH) is a thiol that plays a significant role in nutrient metabolism, antioxidant defense and the regulation of cellular events. GSH deficiency is related to variety of diseases, so it is useful to develop novel approaches for GSH evaluation and detection. In this study we used nitrogen and phosphorus co-doped carbon dot-gold nanoparticle (NPCD–AuNP) composites to fabricate a simple and selective fluorescence sensor for GSH detection. We employed the reductant potential of the nitrogen and phosphorus co-doped carbon dots (NPCDs) themselves to form AuNPs, and subsequently NPCD–AuNP composites from Au3+. The composites were characterized by using a range of spectroscopic and electron microscopic techniques, including electrophoretic light scattering and X-ray diffraction. The overlap of the fluorescence emission spectrum of NPCDs and the absorption spectrum of AuNPs resulted in an effective inner filter effect (IFE) in the composite material, leading to a quenching of the fluorescence intensity. In the presence of GSH, the fluorescence intensity of the composite was recovered, which increased proportionally to increasing the GSH concentration. In addition, our GSH sensing method showed good selectivity and sensing potential in human serum with a limit of detection of 0.1 µM and acceptable results.

Thiophene-Based Trimers and Their Bioapplications: An Overview

Certainly, the success of polythiophenes is due in the first place to their outstanding electronic properties and superior processability. Nevertheless, there are additional reasons that contribute to arouse the scientific interest around these materials. Among these, the large variety of chemical modifications that is possible to perform on the thiophene ring is a precious aspect. In particular, a turning point was marked by the diffusion of synthetic strategies for the preparation of terthiophenes: the vast richness of approaches today available for the easy customization of these structures allows the finetuning of their chemical, physical, and optical properties. Therefore, terthiophene derivatives have become an extremely versatile class of compounds both for direct application or for the preparation of electronic functional polymers. Moreover, their biocompatibility and ease of functionalization make them appealing for biology and medical research, as it testifies to the blossoming of studies in these fields in which they are involved. It is thus with the willingness to guide the reader through all the possibilities offered by these structures that this review elucidates the synthetic methods and describes the full chemical variety of terthiophenes and their derivatives. In the final part, an in-depth presentation of their numerous bioapplications intends to provide a complete picture of the state of the art.

Bioinspired dandelion-like silica nanoparticles modified with L-glutathione for highly efficient enrichment of N-glycopeptides in biological samples

The pretreatment of complicated biological samples to eliminate the interference of nonglycopeptides and improve the efficiency of glycopeptides detection is crucial in glycoproteomics research. Hydrophilic interaction chromatography (HILIC) has been adopted for enrichment of glycosylated peptides following identification with mass spectrometry, but it is still urgent to develop novel hydrophilic materials to save cost and improve enrichment efficiency. Scientists are pursuing to fabricate freestanding intelligent artificial materials. One promising approach is to use biomimic material. In our case, "one-pot" strategy was developed to prepare bioinspired nano-core-shell silica microspheres (CSSMs), employing tetrapropylorthosilicate as the silicon source and phenolic resin as the soft template. The pore structure of the obtained microspheres diverged from the center to the outside with diameter ranged from 150 to 340 nm, and shell layer ranged from 25 to 83 nm by adjusting the preparation parameters. Some of them showed dandelion-like morphology. After hydrophilic modification, these CSSMs exhibited great hydrophilicity and could be used as sorbents for enriching N-glycopeptides from complicated biological samples in HILIC. Up to 594 unique N-glycopeptides and 367 N-glycosylation sites from 182 N-glycoproteins were unambiguously identified from 2 μL of human serum, which was superior to the enrichment performance of many HILIC materials in reported papers, demonstrating great potential advantages in proteomic application.

Overview and recent advances in electrochemical sensing of glutathione - A review

The present paper is aimed at providing an overview of the recent advances in the electrochemical sensing of glutathione (GSH), an important electrochemically and biologically active molecule, for the period 2012-2018. Herein, the analytical performances of newly developed electrochemical methods, procedures and protocols for GSH sensing are comprehensively and critically discussed with respect to the type of method, electrodes used (new electrode modifications, advanced materials and formats), sample matrices, and basic validation parameters obtained (limit of detection, linear dynamic range, precision, selectivity/evaluation of interferences). This paper considers electrochemical methods used alone as well as the hyphenated methods with electrochemical detection (ECD), such as HPLC-ECD or CE-ECD. The practical applicability of the platforms developed for GSH detection and quantification is mostly focused on pharmaceutical and biomedical analysis. The most significant electrochemical approaches for GSH detection in multicomponent analyte samples and multicomponent matrices and for real-time in vivo GSH analysis are highlighted. The great variability in the electrochemical techniques, electrode approaches, and obtainable performance parameters, discussed in this review, brought new insights not only on current GSH and glutathione disulfide (GSSG) determinations, but, along with this, on the advances in electrochemical analysis from a more general point of view.

Gold nanoparticle surface engineering strategies and their applications in biomedicine and diagnostics

Gold nanoparticles (AuNPs) have found a wide range of biomedical and environmental monitoring applications (viz. drug delivery, diagnostics, biosensing, bio-imaging, theranostics, and hazardous chemical sensing) due to their excellent optoelectronic and enhanced physico-chemical properties. The modulation of these properties is done by functionalizing them with the synthesized AuNPs with polymers, surfactants, ligands, drugs, proteins, peptides, or oligonucleotides for attaining the target specificity, selectivity and sensitivity for their various applications in diagnostics, prognostics, and therapeutics. This review intends to highlight the contribution of such AuNPs in state-of-the-art ventures of diverse biomedical applications. Therefore, a brief discussion on the synthesis of AuNPs has been summarized prior to comprehensive detailing of their surface modification strategies and the applications. Here in, we have discussed various ways of AuNPs functionalization including thiol, phosphene, amine, polymer and silica mediated passivation strategies. Thereafter, the implications of these passivated AuNPs in sensing, surface-enhanced Raman spectroscopy (SERS), bioimaging, drug delivery, and theranostics have been extensively discussed with the a number of illustrations.

Glutathione as a Marker for Human Disease

Glutathione (GSH), often referred to as "the master antioxidant," participates not only in antioxidant defense systems, but many metabolic processes, and therefore its role cannot be overstated. GSH deficiency causes cellular risk for oxidative damage and thus as expected, GSH imbalance is observed in a wide range of pathological conditions including tuberculosis (TB), HIV, diabetes, cancer, and aging. Consequently, it is not surprising that GSH has attracted the attention of biological researchers and pharmacologists alike as a possible target for medical intervention. Here, we discuss the role GSH plays amongst these pathological conditions to illuminate how it can be used as a marker for human disease.

Fluorescence detection of glutathione and oxidized glutathione in blood with a NIR-excitable cyanine probe

Cyanine has been widely utilized as a near infrared (NIR) fluorophore for detection of glutathione (GSH). However, the excitation of most of the reported cyanine-based probes was less than 800 nm, which inevitably induce biological background absorption and lower the sensitivity, limiting their use for detection of GSH in blood samples. To address this issue, here, a heptamethine cyanine probe (DNIR), with a NIR excitation wavelength at 804 nm and a NIR emission wavelength at 832 nm, is employed for the detection of GSH and its oxidized form (GSSG) in blood. The probe displays excellent selectivity for GSH over GSSG and other amino acids, and rapid response to GSH, in particular a good property for indirect detection of GSSG in the presence of enzyme glutathione reductase and the reducing agent nicotinamideadenine dinucleotide phosphate, without further separation prior to fluorescent measurement. To the best of our knowledge, this is the first attempt to explore NIR fluorescent approach for the simultaneous assay of GSH and GSSG in blood. As such, we expect that our fluorescence sensors with both NIR excitation and NIR emission make this strategy suitable for the application in complex physiological systems.

Paper based diagnostics for personalized health care: Emerging technologies and commercial aspects

Personalized health care (PHC) is being appreciated globally to combat clinical complexities underlying various metabolic or infectious disorders including diabetes, cardiovascular, communicable diseases etc. Effective diagnoses majorly depend on initial identification of the causes which are nowadays being practiced in disease-oriented approach, where personal health profile is often overlooked. The adoption of PHC has shown significantly improved diagnoses in various conditions including emergency, ambulatory, and remote area. PHC includes personalized health monitoring (PHM), which is its integral part and may provide valuable information's on various clinical conditions. In PHC, bio-fluids are analyzed using various diagnostic devices including lab based equipment and biosensors. Among all types of biosensing systems, paper based biosensors are commercially attracted due to its portability, easy availability, cheaper manufacturing cost, and transportability. Not only these, various intrinsic properties of paper has facilitated the development of paper based miniaturized sensors, which has recently gained ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment free, Deliverable to all end-users) status for point of care diagnosis in miniaturized settings. In this review, importance of paper based biosensors and their compatibility for affordable and low cost diagnostics has been elaborated with various examples. Limitations and strategies to overcome the challenges of paper biosensor have also been discussed. We have provided elaborated tables which describe the types, model specifications, sensing mechanisms, target biomarkers, and analytical performance of the paper biosensors with their respective applications in real sample matrices. Different commercial aspects of paper biosensor have also been explained using SWOT (Strength, Weakness, Opportunities, Threats) analysis.

Amperometric sensing of HIF1α expressed in cancer cells and the effect of hypoxic mimicking agents

Hypoxia inducible factor 1 alpha (HIF1α) overexpression was detected in cancerous cells using an amperometric immunosensor with a nano-bioconjugate. The sensor probe was fabricated by covalently immobilizing the antibody (anti-HIF1α) onto a composite layer of functionalized conducting polymer [2,2:5,2-terthiophene-3-(p-benzoic acid)] (pTTBA) formed on a layer of gold nanoparticles (AuNPs). A nano-bioconjugate with hydrazine and a secondary antibody of HIF1α (sec-Ab2) attached on AuNPs reveals the immunoreaction at the sensor probe through the catalytic reduction of H2O2 by hydrazine at -0.35V vs. Ag/AgCl. Morphology and performance of the sensor probe were characterized using FE-SEM, XPS, EIS, and cyclic voltammetry. The calibration plot at optimized experimental conditions shows a dynamic range of 25-350pM/mL with a detection limit of 5.35±0.02pM/mL. The reliability of the sensor was evaluated using non-cancerous Vero and cancerous MCF-7 cell lysates, where the HIF1α expression was compared with three cancerous cell lines MCF-7, PC-3, and A549. Furthermore, the sensor probe confirms the stable expression of HIF1α in the A549 lung cancer cells when exposing them to hypoxic mimicking agents Co, Ni, and Mn ions. Of these, Co ions show the highest stabilization effect on HIF1α followed by Ni and Mn ions, respectively.

Age-dependent detection of erythrocytes glucose-6-phosphate dehydrogenase and its correlation with oxidative stress

CONTEXT

Glucose-6-phosphate dehydrogenase (G6PD) is an important enzyme of hexose monophosphate shunt, involved in the biosynthesis of reduced nicotinamide adenine dinucleotide phosphate hydrogen (NADPH).

OBJECTIVE

This study was designed to investigate age-dependent changes in human erythrocyte G6PD activity. The G6PD activity pattern was correlated with reduced glutathione (GSH) and total antioxidant potential in terms of FRAP (ferric reducing ability of plasma) value.

MATERIALS AND METHODS

We analyzed normal, healthy subjects of both sexes between the ages of 20 and 80 years. G6PD activity was determined by Burties method.

RESULTS

We observe a significant age-dependent decrease in G6PD activity (p < 0.0001). It was positively correlated with GSH (r = 0.5706) and total antioxidant potential (r = 0.7723) as a function of human age.

DISCUSSION AND CONCLUSION

Our findings on erythrocyte G6PD and their correlation with GSH and FRAP provide evidence of a higher oxidative stress in old age population.

Phytofabricated metallic nanoparticles and their clinical applications

Metallic nanoparticles (MNPs) have seen myriad applications in various fields of science and technology.

Multi-target detection of oxidative stress biomarkers in quercetin and myricetin treated human red blood cells

Quercetin and myricetin help against oxidative stress in human red blood cells during aging, thereby has tremendous scope in medical diagnostics and therapeutics.

Binding of glutathione and melatonin to pepsin occurs via different binding mechanisms

Glutathione is a hydrophilic antioxidant and melatonin is a hydrophobic antioxidant, thus, the binding mechanism of the two antioxidants interacting with protease may be different. In this study, binding of glutathione and melatonin to pepsin has been studied using isothermal titration calorimetry (ITC), equilibrium microdialysis, UV-Vis absorption spectroscopy, circular dichroism (CD) spectroscopy, and molecular modeling. Thermodynamic investigations reveal that the binding of glutathione/melatonin to pepsin is driven by favorable enthalpy and unfavorable entropy, and the major driving forces are hydrogen bond and van der Waals force. ITC, equilibrium microdialysis, and molecular modeling reveal that the binding of glutathione to pepsin is characterized by a high number of binding sites. For melatonin, one molecule of melatonin combines with one molecule of pepsin. These results confirm that glutathione/melatonin interact with pepsin through two different binding mechanisms. In addition, the UV-Vis absorption and CD experiments indicate that glutathione and melatonin may induce conformational and microenvironmental changes of pepsin. The conformational changes of pepsin may affect its biological function as protease.

Ultrasensitive cytosensing based on an aptamer modified nanobiosensor with a bioconjugate: Detection of human non-small-cell lung cancer cells

A novel aptamer-based amperometric nanobiosensor was designed for the sensitive and selective detection of A549 human non-small-cell lung cancer (NSCLC) cells. The cytosensing was performed using a MUC1 aptamer probe with a bioconjugate, where the probe was fabricated by the covalent immobilization on a conducting polymer nanocomposite formed through the self-assembly of 4-([2,2':5',2''-terthiophen]-3'-yl) benzoic acid (TTBA) on AuNPs. A bioconjugate composed of hydrazine and aptamer attached on AuNPs was used to reveal the selectively amplified detection signal. The cells were quantitatively analyzed using chronoamperometric measurements, and the results were further compared and confirmed using microscopic and DPV methods based on silver staining cytosensing experiments. The proposed aptasensor showed a high affinity for MUC1 positive lung cancer cells (A549) compared with the other control cancer cells, including human prostate (PC3), MUC1 negative normal lung (MRC-5), and liver tumors (HepG2) cells. An excellent dynamic range of the proposed method was obtained from 15 to 1×10(6) cells/mL with a detection limit of 8 cells/mL.

Analysis of Phthalate Esters in Mammalian Cell Culture Using a Microfluidic Channel Coupled with an Electrochemical Sensor

An analytical tool to monitor trace phthalate was developed using a microfluidic channel device coupled with a novel electrochemical biosensor. At first, the electrochemical sensor was constructed with biomimetic layers to reveal a large hydrogen over potential by controlling the surface charge and hydrophobicity through assembling with a lipid (1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) and a cationic molecule (toluidine blue O) bonded to a conductive polymer. The modified electrode possessing a highly negative polarization potential (approximately -1.8 V vs Ag/AgCl) can uptake sparingly soluble phthalate ester (PEs) compounds in aqueous media. Each sensor probe material was characterized employing SEM, AFM, XPS, QCM, TEM, UV-visible, and impedance spectroscopy. The microfluidic channel is used first to concentrate and separate trace amounts of phthalates, and then the sensor probe is installed at the end of channel. Experimental variables affecting the PEs analysis were assessed and optimized in terms of biomimetic layer composition and analytical conditions. The linear dynamic range and detection limits of the PEs were 0.15 nM-10.0 μM and ∼12.5 pM with relative standard deviations <5%. The proposed method was applied to evaluate the effect of endocrine disruptors on mammalian kidney cells, where the cell samples show in-taking percentages between 1.8 and 7.0% to the total PEs according to the incubation time.

Ultrasensitive detection of drug resistant cancer cells in biological matrixes using an amperometric nanobiosensor

Multidrug resistance (MDR) is a key issue in the failure of cancer chemotherapy and its detection will be helpful to develop suitable therapeutic strategies for cancer patients and overcome the death rates. In this direction, we designed a new amperometric sensor (a medical device prototype) to detect drug resistant cancer cells by sensing "Permeability glycoprotein (P-gp)". The sensor probe is fabricated by immobilizing monoclonal P-gp antibody on the gold nanoparticles (AuNPs) conducting polymer composite. The detection relies on a sandwich-type approach using a bioconjugate, where the aminophenyl boronic acid (APBA) served as a recognition molecule which binds with the cell surface glycans and hydrazine (Hyd) served as an electrocatalyst for the reduction of H2O2 which are attached on multi-wall carbon nanotube (MWCNT) (APBA-MWCNT-Hyd). A linear range for the cancer cell detection is obtained between 50 and 100,000 cells/mL with the detection limit of 23±2 cells/mL. The proposed immunosensor is successfully applied to detect MDR cancer cells (MDRCC) in serum and mixed cell samples. Interferences by drug sensitive (SKBr-3 and HeLa), noncancerous cells (HEK-293 and OSE), and other chemical molecules present in the real sample matrix are examined. The sensitivity of the proposed immunosensor is excellent compared with the conventional reporter antibody based assay.

Binding of glutathione and melatonin to human serum albumin: a comparative study

Binding of glutathione and melatonin to human serum albumin (HSA) has been studied using isothermal titration calorimetry (ITC) in combination with UV-vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and circular dichroism (CD) spectroscopy. Thermodynamic investigations reveal that glutathione/melatonin binds to HSA is driven by favorable enthalpy and unfavorable entropy, and the major driving forces are hydrogen bond and van der Waals force. For glutathione, the interaction is characterized by a high number of binding sites, which suggests that binding occurs by a surface adsorption mechanism that leads to coating of the protein surface. For melatonin, one molecule of melatonin combines with one molecule of HSA and no more melatonin binding to HSA occurs at concentration ranges used in this study. The UV-vis absorption, FT-IR, and CD spectroscopy suggest that glutathione and melatonin may induce conformational and microenvironmental changes of HSA.

Prospects and advancements in C-reactive protein detection

C-reactive protein (CRP) is one of the earliest proteins that appear in the blood circulation in most systemic inflammatory conditions and this is the reason for its significance, even after identification of many organ specific inflammatory markers which appear relatively late during the course of disease. Earlier methods of CRP detection were based on the classical methods of antigen-antibody interaction through precipitation and agglutination reactions. Later on, CRP based enzymatic assays came into the picture which were further modified by integration of an antigen-antibody detection system with surface plasma spectroscopy. Then came the time for the development of electrochemical biosensors where nanomaterials were used to make a highly sensitive and portable detection system based on silicon nanowire, metal-oxide-semiconductor field-effect transistor/bipolar junction transistor, ZnS nanoparticle, aptamer, field emission transmitter, vertical flow immunoassay etc. This editorial attempts to summarize developments in the field of CRP detection, with a special emphasis on biosensor technology. This would help in translating the latest development in CRP detection in the clinical diagnosis of inflammatory conditions at an early onset of the diseases.

A sensitive and selective chemosensor for GSSG detection based on the recovered fluorescence of NDPA-Fe₃O₄@SiO₂-Cu(II) nanomaterial

A sensitive and selective sensor for oxidized glutathione (GSSG) detection based on the recovered fluorescence of naphthalimide-DPA (NDPA)-Fe₃O₄@SiO₂-Cu(II) system is reported. NDPA-Fe3Fe₃O₄@SiO₂ was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR) and fluorophotometry. The fluorescence of NDPA-Fe₃O₄@SiO₂ could be quenched by Cu²⁺ due to the coordination of Cu²⁺ with the tridentate receptor DPA. This coordination process reduced the electron-donating ability of the nitrogen atom in the DPA moiety, thus suppressing the internal charge transfer (ICT) process in NDPA-Fe₃O₄@SiO₂. In the presence of GSSG, the fluorescence of NDPA-Fe₃O₄@SiO₂-Cu(II) was recovered because of strong coordination of Cu²⁺ with GSSG, which promoted the decomplexation between NDPA-Fe₃O₄@SiO₂ and Cu²⁺, and enhanced the ICT process. The NDPA-Fe₃O₄@SiO₂-Cu(II) nanomaterial exhibited high sensitivity towards GSSG, and a good linear relationship was obtained from 5 nM to 60 μM. The limit of detection, based on a signal-to-noise ratio of 3, was 50 pM. In addition, the presence of magnetic Fe₃O₄ nanoparticles (NPs) in NDPA-Fe₃O₄@SiO₂ NPs would also facilitate the magnetic separation of NDPA-Fe₃O₄@SiO₂ from the solution. Through the use of added internal standards, we successfully determined the concentration of GSSG in HEK 293 cell lysate to be 1.15 μM by the prepared chemsensor NDPA-Fe₃O₄@SiO₂-Cu(II). The proposed method is anticipated to fabricate other sensitive fluorescence sensors based on organic-inorganic hybrid magnetic nanoparticles.