Sensitive and rapid detection of bacterial endotoxin with a functional carbon nanotube field-effect transistor biosensor.

Endotoxin in the blood can cause unexplained fever, and even death due to endotoxemia and bacteremia. Rapid and sensitive detection of endotoxin has become a priority event to intervene in the occurrence of dangerous diseases in time. In this context, a carbon nanotubes-based field-effect transistor (CNTs FET) nanosensor is developed to realize the rapid, label-free and sensitive detection of endotoxin. The CNTs FET was fabricated by assembling the polymer-sorted high-purity semiconductor CNT films onto the sensing channel. In order to improve the detection sensitivity, carboxylated graphene quantum dots (cGQDs) were coupled to the CNT surface via the poly-l-lysine (PLL). After that, polymyxin B (PMB), which is highly specific for endotoxin, was covalently combined with cGQDs, thus enabling the capture and detection of endotoxin. The method not only displayed an extremely low level of limitation of detection in PBS (4.6 fg/mL) and serum (30.3 fg/mL), respectively, with superior resistance to interference, but also enabled the analysis of Gram-negative bacterial infections in blood samples in a short duration of time. Meanwhile, the receiver operating characteristic curve (ROC) proved the superior diagnostic accuracy of this method (AUC = 0.990). Considering its excellent performance, the constructed CNTs FET biosensor is a promising tool to provide early warning of disease for clinical Gram-negative bacteremia and endotoxemia.

Electrochemical immunosensor based on hollow Pt@Cu2O as a signal label for dual-mode detection of procalcitonin.

As a reliable biomarker to evaluate the severity of sepsis, sensitive and accurate detection of procalcitonin (PCT) is essential. In this study, a dual-mode electrochemical immunosensor based on Au/ZIF-8 as substrate and Pt@Cu2O as signal label was constructed for the detection of PCT. By loading Au nanoparticles onto rhombic dodecahedral ZIF-8, the substrate (Au/ZIF-8) has large specific surface area and can immobilize antibody (Ab1) by Au-N bonds. Meanwhile, hollow Pt@Cu2O nanocomposite with excellent peroxidase-like activity and electrocatalytic activity were synthesized as signal label. In the process of electrochemical testing, Pt@Cu2O catalyzed the reduction of hydrogen peroxide (H2O2) and further promotes the oxidation of hydroquinone (HQ) to achieve the synergistic amplification of electrochemical signals. The proposed immunosensor detected PCT by amperometric i-t and differential pulse voltammetry (DPV) tests with a good linear response and low limit of detection (i-t: 0.70 fg/mL and DPV: 0.40 fg/mL) in the range of 10 fg/mL∼100 ng/mL. The immunosensor exhibited excellent sensitivity and accuracy, indicating the potential application of this method for PCT detection.

Laser-scribing graphene-based electrochemical biosensing devices for simultaneous detection of multiple cancer biomarkers.

In this study, a graphene electrochemical sensor based on laser graphene polymer material was proposed to induce graphene formation on polyimide substrates via fiber laser. The laser produces stable power and results to achieve the benefits of consistency, conductivity, and flexibility. The electrochemical three-electrodes were manufactured on polyimide to replace the traditional three-electrodes by achieving small size and portability. An electrode activation is the modification of laser-scribed graphene electrodes (LSG) to facilitate the binding of liver cancer sites. The evaluation is performed by differential pulse Voltammetry (DPV) to detect cancer proteins in the phosphate buffer saline (PBS) buffer and serum. In a serum environment, the concentrations of alpha-fetoprotein (AFP) and Carcinoembryonic antigen (CEA) were detected from 0.75 ng ml-1 to 100 ng ml-1, AFP and CEA electrodes have a good linear range (R2 = 0.96 and R2 = 0.98), indicating the sensor's sensitivity and specificity for cancer detection. In addition, two types of carcinogenic proteins were monitored in the PBS and successfully detected in this experiment. Based on the results, the appropriate LSG sensor may be used for monitoring with limited resources. Electrode manufacturing is simple, fast, low-cost, small in size, convenient to carry, stable, instant detection, and flexible.

Synergies of WO3 and Co3O4 intercalated ball milling exfoliated graphene 3D helix electrocatalyst: A highly sensitive electrochemical detection of mesotrione herbicide in vegetable samples.

In the booming global population, monitoring of mesotrione (MTN) like agricultural pollutants is crucial for human safety. Herein, the research reports the synthesis of tungsten trioxide (WO3) and cobalt oxide (Co3O4) nanostructures intercalated ball milling exfoliated graphene (WO3/Co3O4/graphene) 3D helix electrocatalyst for the electrochemical detection of MTN herbicide. The proposed WO3/Co3O4/graphene sensor material achieved a wide range of MTN detection from 0.001 µM to 1885 µM. In addition, the estimated limit of sensing and sensitivity values are 0.42 nM and 0.802 µAµM-1 cm-2 respectively. The real sample experiment was accomplished in MTN-added vegetables (corn, sugar cane, tomato, green soybean) and environmental samples (sewage water, river water). At most, the recorded minimum MTN response recovery in vegetables and water samples is about 95% and 98% respectively. Furthermore, the designed sensor electrode achieved storage stability of 98.7% after three weeks.

Pt nanoparticles/laser-engraved graphene-based integrated electrochemical platform for point-of-use determination of ponceau 4R, amaranth and tartrazine in food.

This study presents the first integrated electrochemical platform (IEP) with point-of-use and portable features for on-site determination of ponceau 4R (RP), amaranth (AM), and tartrazine (TZ) in food by integrating a mass-producible Pt nanoparticles/laser-engraved graphene (Pt NPs/LEG)-based sensing chip and a reusable electrochemical miniaturized workstation. The sensing chip utilizes Pt NPs/LEG with unique architectures as electrode material and exhibits desirable analytical performance towards RP, AM, or TZ with satisfied linear range (0.25-50 µM for RP, AM, and TZ), high sensitivity (7.29 µA µM-1 cm-2, 7.18 µA µM-1 cm-2, and 2.02 µA µM-1 cm-2 for RP, AM, and TZ, respectively) and low limit of detection (50 nM, 58 nM, and 204 nM for RP, AM, and TZ, respectively). The sensing chip shows excellent selectivity, high stability, outstanding reproducibility, and acceptable mechanical stability. IEP can be implemented to test RP, AM, or TZ in real samples with satisfactory accuracy and recoveries.

Graphene-wrapped petal-like gap-enhanced Raman tags for enhancing photothermal conversion and Raman imaging.

Multifunctional nanoplatform that combine imaging, diagnostic, and therapeutic functions into a single agent have great significance for the early diagnosis and efficient treatment of diseases, particularly tumors. In this study, we report on a novel graphene-wrapped petal-like gap-enhanced Raman tags with mesoporous silica shells (MS-GP-GERTs). These MS-GP-GERTs have 4-NBT Raman reporters embedded in the gap between the gold nanocore and the petal-shaped shell and are wrapped in graphene and mesoporous silica. The results of photothermal measurement experiments show that graphene layers significantly enhanced the photothermal effect of gap-enhanced Raman tags (GERTs). The photothermal conversion efficiency of MS-GP-GERTs reaches 40.8%, comparable to pure graphene. Moreover, MS-GP-GERTs show good photothermal performance in agarose phantoms, heating the phantom to 47 °C within 5 min under a low power density laser (0.5 W/cm2). MS-GP-GERTs also exhibit excellent photothermal stability and physiological environment stability, making them a promising candidate for repeated photothermal therapy. Raman spectra and mapping imaging experiments demonstrate MS-GP-GERTs' low detection limit (100 fM), large imaging depth (2.74 mm), and excellent ability to image simulated biological tissue and cells. This novel Raman tag has the potential to become a multifunctional nano platform for integrating Raman imaging diagnosis and photothermal therapy.

A novel electrochemical sensor based on dual-functional MMIP-CuMOFs for both target recognition and signal reporting and its application for sensing bisphenol A in milk.

In this work, novel magnetic molecularly imprinted CuMOFs (MMIP-CuMOFs) were synthesized and applied to construct an electrochemical bisphenol A sensor. The constructed sensor used an electrode modified with reduced graphene oxide (RGO/GCE) as the sensing platform to improve its stability and sensitivity. The Fe3O4 nanoparticles in magnetic MOFs simplified the preparation process. Moreover, the combination of CuMOFs and molecular imprinting methodology was beneficial for improving the detection specificity, and the electroactive copper hexacyanoferrate generated by the reaction of Cu2+ in CuMOFs with potassium ferricyanide was used as the signal probe. The sensor showed a good linear relationship in the range of 0.5 to 500 nmol/L, with a low detection limit of 0.18 nmol/L. In addition, the sensor had good selectivity, repeatability (RSD = 2.59 %), and a good recovery rate for actual milk sample detection (99.8-102.49 %). This technique holds great promise for the detection of detrimental substances in food.

Graphene oxide-enhanced colorimetric detection of Mec A gene based on toehold-mediated strand displacement.

Mec A, as a representative gene mediating resistance to ß-lactam antibiotics in methicillin-resistant Staphylococcus aureus (MRSA), allows a new genetic analysis for the detection of MRSA. Here, a sensitive, prompt, and visual colorimetry is reported to detect the Mec A gene based on toehold-mediated strand displacement (TMSD) and the enrichment effect of graphene oxide (GO). The Mec A triggers to generate the profuse amount of signal units of single-stranded DNA (SG) composed of a long single-stranded base tail and a base head: the tail can be adsorbed and enriched on the surface of GO; the head can form a G quadruplex structure to exert catalytic function towards 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid). Therefore, through the enrichment effect of GO, the signal units SG reflects different degrees of signal amplification on different substrates (such as aqueous solution or filter membrane). This strategy demonstrates a broad linear working range from 100 pM to 1.5 nM (solution) and 1 pM to 1 nM (filter membrane), with a low detection limit of 39.53 pM (solution) and 333 fM (filter membrane). Analytical performance in real samples suggests that this developed colorimetry is endowed with immense potential for clinical detection applications.

Nanomolar electrochemical detection of feed additive ractopamine in meat samples using spinel zinc ferrite decorated 3-dimensional graphene nanosheets to combat food fraud in livestock industries.

Accurate detection of feed additive is significant for food safety monitoring, warding off its illegal use in livestock production, safeguarding public health, and regulatory compliance. Hence, this paper presents a cost-effective and ultrasensitive electrochemical sensor for detecting commonly used animal feed additive, ractopamine to combat food frauds in meat samples. The sensor was created by embedding spinel zinc ferrite nanospheres (ZnFe2O4) on three-dimensional graphene (3DG) nanosheets using sonochemical method. ZnFe2O4 nanospheres were synthesized using solvothermal approach, and 3DG was prepared using hydrothermal method. Various characterization techniques were used for inspecting structural and morphological properties of materials, including XRD, SEM, TEM, elemental mapping, Raman spectroscopy, XPS, and EIS. The hybrid nanocomposite modified electrode showed excellent electrochemical performance, with high sensitivity of 16.97 µA µM-1 cm-2 and detection limit of 1 nM. The practicality of sensor was demonstrated by performing real sample analysis in pork, beef, and sausage which gave adequate recovery.

Application of surface nitrogen-doped graphene quantum dots in the sensing of ferric ions and glutathione: Spectroscopic investigations and DFT calculations.

Developing a sensing platform that can quickly and accurately measure glutathione (GSH) is crucial for the early detection of various human diseases. GQDs have shown great potential in many technological and biological applications. This study focused on synthesizing nitrogen-doped GQDs (NGQDs) with stable blue fluorescence using a simple and easy hydrothermal method in one step. The bamboo fiber was used as the green source for this synthesis. The NGQDs had a tiny particle size of 4.7 nm and emitted light at 405 nm when excited. They displayed a remarkable quantum yield of 40.36 % and were effectively used as fluorescent probe to specifically detect Fe3+. The energy transfer mechanism led to the NGQDs' fluorescence being deactivated by Fe3+ ions (turn- "off"). However, with the addition of GSH to the system, the fluorescence intensity of NGQDs was reactivated (turn- "on"). Thus, a fluorescence turn "off-on" system was developed for the sensitive detection of Fe3+ and GSH. Using density functional theory (DFT), it was theoretically calculated that the surface of the fabricated NGQDs possess lone pairs of electrons on oxygens and doped nitrogen causing a photo-induced electron transfer (PET) process to occur. This PET process was suppressed previously owing to complex formation between oxygen atoms of modeled structure and ferric ions. The sensing platform displayed a sensitive response to Fe3+ in the 1-1000 µM range with LOD of 34 nM and GSH in the range of 1-50 µM, with a detection limit of 45 nM. Furthermore, the NGQDs exhibited high selectivity towards Fe3+ and GSH over other electrolytes and biomolecules. Additionally, the probe exhibited non-cytotoxicity and was practically applicable for the detection of GSH in HeLa cells.

A novel sandwich-type electrochemical immunosensor for sensitive detection of zearalenone using NG/PDDA/HNTs and Ti-MOF-KB composites for signal amplification.

In this work, a novel sandwich-type electrochemical immunosensor based on signal amplification was developed for the ultrasensitive detection of zearalenone (ZEA). The composite consisting of poly(diallyldimethylammonium chloride) functionalized nitrogen doped graphene, halloysite nanotubes and toluidine blue (Tb/NG/PDDA/HNTs), was synthesized for the first time. Then it was modified with gold nanoparticles (AuNPs) to bind the secondary antibody (Ab2, 10 µg mL-1) and form the tracer label. In addition, ketjen black (KB) was doped into titanium-based metal-organic framework (Ti-MOF), which provided large specific surface area and employed as the sensing platform to increase the immobilization of the primary antibody (Ab1, 10 µg mL-1). This immunosensor showed a wide linear range for ZEA from 10 fg mL-1 to 100 ng mL-1 with a limit of detection (LOD) as low as 0.57 fg mL-1, which was below the maximum tolerable levels (50∼100 µg kg-1) set by the United Nations Food and Agriculture Organization (FAO).

Better biocompatibility of nitrogen-doped graphene compared with graphene oxide by reducing cell autophagic flux blockage and cell apoptosis.

Nitrogen-doped graphene (C2 N), a novel graphene-based materials, has been proposed as a potential alternative to graphene oxide (GO) in biomedical applications. However, due to the challenges in synthesizing C2 N, reports in the biomedical field are currently rare. Here, we have modified the reported procedure and successfully synthesized C2 N nanoparticles at 120°C, which we refer to as C2 N-120. The toxicity and biocompatibility of GO and C2 N-120 were evaluated using a mouse model injected with GO/C2 N-120 via the tail vein, as well as cell models treated with GO/C2 N-120. In vivo studies revealed that GO/C2 N-120 showed similar distribution patterns after tail vein injection. The liver, spleen, and lung are the major nanoparticle uptake organs of GO and C2 N-120. However, GO deposition in the major nanoparticle uptake organs was more significant than that of C2 N-120. In addition, GO deposition caused structural abnormalities, increased apoptotic cells, and enhanced macrophage infiltration whereas C2 N-120 exhibited fewer adverse effects. In vitro experiments were conducted using different cell lines treated with GO/C2 N-120. Unlike GO which induced mitochondrial damage, oxidative stress, inflammatory response, autophagic flux blockage and cell apoptosis, C2 N-120 showed lower cytotoxicity in cell models. Our data demonstrated that C2 N-120 exhibits higher biocompatibility than GO, both in vivo and in vitro, suggesting its potential for biomedical application in the future.

Toward the early diagnosis of tuberculosis: A gold particle-decorated graphene-modified paper-based electrochemical biosensor for Hsp16.3 detection.

Tuberculosis (TB) currently remains a major life-threatening disease as it can be fatal if not treated properly or in a timely manner. Herein, we first describe a disposable and cost-effective paper-based electrochemical biosensor based on a gold particle-decorated carboxyl graphene (AuPs/GCOOH)-modified electrode for detecting heat shock protein (Hsp16.3), which is a specific biomarker indicating the onset of TB infection. The device pattern was first engineered to facilitate detection procedures and printed on low-cost filter paper to create hydrophobic and hydrophilic regions using a wax printing technique. Immunoassays proceeded in a half-sandwich format because it is a reagent-less approach and requires no labeling step. The fabrication of the immunosensor began with GCOOH drop casting, the electrochemical deposition of AuPs, and the establishment of a biorecognition layer against Hsp16.3 utilizing 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS)-sulfo standard chemistry. The appearance of Hsp16.3 resulted in a substantial decrease in the electrochemical signal response of the redox probe employed [Fe (CN)6]3-/4- due to the created immunocomplexes that possess insulation properties. GCOOH enables direct antibody immobilization, and AuPs enhance the electrochemical properties of the sensor. This proposed immunosensor, while requiring only a miniscule sample volume (5 µL), achieved superior performance in terms of the limit of detection, measuring at 0.01 ng/mL. Our platform was confirmed to be highly specific to Hsp16.3 and can rapidly detect TB-infected sera without necessitating any pre-enrichment (20 min), making it an alternative and particularly suitable for the early diagnosis of TB in resource-scarce countries.

Conductive PEDOT:PSS copolymer electrode coatings for selective detection of dopamine in ex vivo mouse brain slices.

A novel voltammetric sensor was developed to selectively determine dopamine (DA) concentration in the presence of ascorbic acid (AA) and 3,4-dihydroxyphenylacetic acid (DOPAC). This sensor utilizes a modified pencil graphite electrode (PGE) coated with a newly synthesized poly (3,4-ethylene dioxythiophene) (PEDOT):poly (styrene sulfonate-co-2-(3-(6-Methyl-4-oxo-1,4-dihydropyrimidin-2-yl) ureido) ethyl methacrylate) (P(SS-co-UPyMA)) composite. The PEDOT:P(SS-co-UPyMA) (PPU) composite was characterized using nuclear magnetic resonance, X-ray photoelectron, and Raman spectroscopies. The PPU-coated PGE was characterized using electrochemical techniques, including cyclic and differential pulse voltammetry. Compared to uncoated, PPU-coated PGE demonstrated improved sensitivity and selectivity for DA. The sensor exhibited a dynamic linear range of 0.1-300 µM for DA, with a detection limit of 44.4 nM (S/N = 3). Additionally, the PPU-coated PGE showed high reproducibility and storage stability for four weeks. To demonstrate its practical applicability, the PPU-coated PGE sensor was used for ex vivo brain slice samples from control and Parkinson's disease model mice.

Modification of bismuth film and poly(L-hydroxyproline) onto a screen-printed graphene electrode: A step towards a non-enzymatic platform for determining L-hydroxyproline in human urine samples.

A novel sensing material for L-hydroxyproline (Hyp) detection was developed by synthesizing a bismuth film (BiF) and poly(L-hydroxyproline) (Poly(Hyp)) on a screen-printed graphene electrode (SPGE). Initially, the BiF electrodeposition was produced on the SPGE surface, followed by the Poly(Hyp) electropolymerization, resulting in the obtained Poly(Hyp)/BiF/SPGE. The morphology of a sponge-like thin film of Poly(Hyp)/BiF on SPGE had uniform nanometer-sized cavities on the graphene surface, offering a large electroactive area for interaction with the target substance. Cyclic and differential pulse voltammetry was used to examine the sensing performance of the proposed sensor, which revealed that the Poly(Hyp)/BiF/SPGE had the highest response toward Hyp detection. This was attributed to BiF and Poly(Hyp) can facilitate the transfer of electrons at an electrode/solution interface, resulting in an effective sensor for the detection of Hyp. Under the optimal conditions, the quantification of the proposed sensor was found to be linearly related to Hyp concentrations in the range of 0.01-5.0 mM with a limit of detection of 9.2 µM. Moreover, the interference of other substances detected in biological fluids showed no effect based on the ±5% error, indicating good selectivity for Hyp detection. In real applications, the proposed assay successfully analyzed Hyp in human urine samples, yielding satisfactory results with recoveries in the acceptable range of 98%-102%. Therefore, this facilely synthesized approach could be a suitable candidate to obtain a material to fabricate a new sensor for the measurement of Hyp, an important biomarker in the human body.

Peptide-graphene logic sensing system for dual-mode detection of exosomes, molecular information processing and protection.

Peptides with highly sequence-dependent recognition, assembly, and encoding abilities can perform functions similar to DNA or even better, such as biosensing, molecular information processing, coding, or storage. However, the combination of versatile peptides and 2D materials are rarely used for multipurpose integrated applications, including biosensing, information processing and security. Herein, peptide-graphene sensing system was comprehensively used for dual-signal sensing of tumor-derived exosomes (TDEs), logic computing, and information protection. The system used fluorescent-labeled CD63-binding peptide CP05 and graphene oxide (GO) to selectively detect CD63 and TDEs by fluorescence and resonance light scattering. From three levels such as matter, energy, and information analysis, the matter and energy changes in GO-CP05 peptide sensing system were transformed into valuable information, which achieve the dual-mode quantitative detection of TDEs and its marker CD63, and the actual serum analysis. This matter-energy interaction network was also informationized, and utilized for parallel and batch logic computing, two kinds of molecular crypto-steganography (based on peptide sequence and Boolean logic relationships), which facilitates development of intelligent sensing and advanced information technology. This work not only provides a new method for sensitive detection of important disease markers, but also provides ideas for integrating molecular sensing and informatization to open molecular digitization.

Recognition of chiral propranolol by fluorescent aptamerlight switch based on GO.

In this work, specific aptamers with affinity for S-propranolol were screened by SELEX technology based on the graphene oxide (GO) adsorption platform, and a GO-FAM labeled aptamer-propranolol fluorescent optical switch system was constructed for the recognition of chiral propranolol. It was found that the fluorescence quenching of FAM labeled aptamer could be caused by the adsorption of GO. However, when S-propranolol was introduced, S-propranolol could pull out the aptamer adsorbed by GO, and the fluorescence of the system could be restored. But, R-propranolol could not be realized. Therefore, a simple and sensitive fluorescent optical switch system was established to identify chiral propranolol and perform highly sensitive detection of S-propranolol.

A SERS substrate based on perovskite quantum dots and graphene for the determination of cardiac troponin I.

Noble metal has always been used as a preferred base for SERS substrate. However, the preparation cost of such materials is trully high. Therefore, many researchers have begun to search for succedanea which cost were lower. In this work, CsPbBr3@ZIF-8 was synthesized by in-situ reduction method and combined with graphene nanosheets to construct a SERS substrate. The SERS performance of this substrate could be further enhanced by the synergistic effect of perovskite quantum dots and graphene. Base on this material, a sensitive SERS strategy composed of CsPbBr3@ZIF-8@G, antibody, and Bradford method was developed for the quantitative determination of cardiac troponin I (cTnI) in human serum. It's worth noting that the sensitivity and accuracy of this method could approach the level of other SERS methods using noble metals. The "reverse"-SERS method could improve the uniformity and stability of detection platform obviously. The detection range of this method was 0.01-100 ng/mL, and the estimated detection of limit (LOD) was 4.7 pg/mL. The recovery rate of this method range was between 93.1 % and 104.8 %, and RSD range was between 4.47 % and 7.06 %.

sp-ICP-MS and HR-CS-GFAAS as useful available techniques for the size characterization and speciation of ionic and nanoparticular zinc in cosmetic and pharmaceutical samples.

The use of zinc oxide nanoparticles (ZnO NPs) in cosmetic and pharmaceutical industry has been increased in recent years due to their good properties as solar radiation filters and antibacterial agent. According to the literature, the potential toxicity of these NPs could be size-dependent and the amount of solubilized metal. This work investigates new reliable and straightforward methodologies that enables the determination of ZnO NPs, discriminating them from ionic zinc in cosmetic samples. Two different techniques of analysis have been applied in this study: high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS-GFAAS), and "single particle" inductively coupled plasma mass spectrometry (sp-ICP-MS). Triton X-100 has been used as a surfactant for the formation of homogeneous and stable slurries which allowed the determination of the concentration and sizes of ZnO NPs and Zn2+ in baby creams, eyeshadows, and lotions. A central composite design (CCD) was performed for the two techniques to optimize the concentration of Triton X-100 and sonication time. For validation purpose, the results of Zn2+ and ZnO NPs contents achieved by HR-CS-GFAAS were compared with the total Zn content obtained by acid digestion of the samples. A size comparison of the ZnO NPs was also carried out with the data obtained through the two methodologies and validated with transmission electron microscopy (TEM). In the case of TEM analysis, two different media were tried to study possible agglomerates and interactions between the particles and the matrix.

Nitrogen-enhanced carbon quantum dots mediated immunosensor for electrochemical detection of HER2 breast cancer biomarker.

Using nitrogen-enhanced carbon quantum dots (N-CQDs) on a coated graphite sheet (GS) substrate (N-CQDs/GS), a simple strategy for the electrochemical detection of human epidermal growth factor receptor 2 (HER2), a breast cancer biomarker, was investigated. The bovine serum albumin (BSA)-modified HER2 Antibody/N-CQDs/GS immunoelectrode enabled excellent activity preservation for the biosensor, while the GS electrode provided a highly stable and conducting substrate. With a linear response range of 0.1 ng/mL-1 ng/mL and a low detection limit of 4.8 pg/mL. Meanwhile, the methodology demonstrated optimal specificity, stability, and reproducibility for detecting HER-2 protein in breast cancer patients untreated blood samples.