A photoelectrochemical biosensor using ruthenium complex-reduced graphene oxide hybrid as the photocurrent signal reporter assembled on rhombic TiO2 nanocrystals driven by visible light

Magnetic copper silicate and boronic acid-conjugated AuNCs@keratin-based electrochemical/fluorescent dual-sensing for carcinoembryonic antigen

Boronic Acid Sensitivity, selectivity, and reliability are of great importance for tumor diagnosis. Herein, we proposed a novel electrochemical and fluorescent dual-sensing strategy to detect carcinoembryonic antigens (CEA). To this end, monodisperse spindle-like magnetic copper silicate (FeOx@C@CS) was prepared with multiple active sites to immobilize the CEA antibody. Moreover, magnetic properties improved the anti-interference ability and sensitivity to endow the assay for complex samples. In addition, boronic acid-conjugated gold nanocluster (AuNCs@keratin-BA) was prepared as an electrochemical and fluorescent dual-signal indicator. Thus, the sandwich structure of FeOx@C@CS/CEA/AuNCs@keratin-BA was formed for electrochemical/fluorescent dual-modality assay. Under optimal conditions, the quantitation range of 12.5 fg mL-1-37.5 pg mL-1 and detection limit of 4.3 fg mL-1 were obtained for the electrochemical strategy. The fluorescence detection owned the linear range of 0.05 pg mL-1-7.5 pg mL-1 with a detection limit of 0.025 pg mL-1. Dual-modality assay improved the accuracy and efficiency of CEA detection to meet the requirement of tumor diagnosis, while chemical identification and signal transduction lay an important foundation for engineering advanced nanomaterials for clinical applications.

Self-powered biosensor using photoactive ternary nanocomposite: Testing the phospholipid content in rhodotorula glutinis oil

In the field of oil refining, the presence of excessive residual phosphorus in crude oil can significantly impact its quality, thereby emphasizing the necessity for compact and convenient testing equipment. This study primarily focuses on developing of self-powered biosensor (SPB) using immobilizing Choline Oxidase with a photoactive ternary nanocomposite complex (CHOx-BiOI-rGO-Fe3O4 NPs-ITO) as the anode and utilizing a Pt electrode as the cathode. The successful preparation of the ternary composite photoelectrode for the anode was confirmed through a range of characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), N2 absorption/desorption, Dynamic light scattering (DLS), and Ultraviolet-visible diffuse reflection spectrometer (UV-vis DRS). The electrochemical and photoelectrochemical properties were assessed using an electrochemical workstation, revealing a significant enhancement photoelectrical responsiveness attributed to the formation of heterojunction structures. The SPB exhibited a remarkable linear relationship between the instantaneous photocurrent and phosphatidylcholine (PC) concentration, with a regression equation of I (μA) = 39.62071C (mM) + 3.47271. The linear range covered a concentration range of 0.01-10 mM, and the detection limit (S/N = 3) was determined to be 0.008 mM. It demonstrated excellent reproducibility and storage stability, positioning it a promising alternative to High-performance liquid chromatography (HPLC) for accurate quantification of PC content in rhodotorula glutinis oil. The standard recovery PC content ranged from 98.48% to 103.53%, with a relative standard deviation (RSD) ranging from 1.4% to 2.4%. This research presents a convenient and precise detection device that has the potential to address the issue of lagging detection in the oil refining process.

A visible and near-infrared light dual responsive "signal-off" and "signal-on" photoelectrochemical aptasensor for prostate-specific antigen

A visible and near-infrared light dual responsive "signal-off" and "signal-on" photoelectrochemical aptasensor was constructed for determining prostate-specific antigen (PSA) based on MoS₂ nanoflowers and gold nanobipyramids. The dual responsive photoelectrochemical aptasensor can provide accurate results for PSA determination. For the photoelectrochemical aptasensor fabrication, amino-group functionalized aptamers were immobilized on a MoS₂ nanoflowers modified glassy carbon electrode surface for the specific recognition, and thus to achieve a "signal-off" aptasensor for PSA under visible light illumination. Subsequently, gold nanobipyramids integrated with thiol-functional aptamer were introduced to the "signal-off" aptasensing interface after PSA recognition. Under excitation with near-infrared light at 808 nm, the photocurrent response can be amplified significantly due to the excellent conductivity and local surface plasmon resonance effect of gold nanobipyramids, thus to producing a "signal-on" model for determining PSA. Under the optimized conditions, the dual-responsive photoelectrochemical aptasensor shows a linear response to the logarithm of PSA concentration in the range of 0.005-100 ng/mL. The detection limits for PSA determination with a "signal-off" or a "signal-on" mode are 1.75 pg mL^-1 and 0.39 pg mL^-1, respectively. The dual-responsive photoelectrochemical aptasensor was also employed for determining PSA in clinical serum samples with satisfactory selectivity and excellent accuracy.

Polydopamine nanospheres with multiple quenching effect on TiO2/CdS:Mn for highly sensitive photoelectrochemical assay of tumor markers

A photoelectrochemical (PEC) immunosensing strategy based on the multiple quenching of polydopamine nanoparticles (PDA NPs) to Mn²⁺-doped CdS-modified TiO₂ nanoparticles (TiO₂/CdS:Mn) was designed for the highly sensitive detection of carcinoembryonic antigen (CEA). The uniform PDA NPs possessed good dispersibility, good biocompatibility, and abundant functional groups for biomolecule assembly. They also had unique photophysical properties, with light absorption spanning the visible to infrared light range. When the immune-recognition brought the PDA NPs close to the TiO₂/CdS:Mn interface, the PDA NPs competed with TiO₂/CdS:Mn to absorb light, consumed photoelectrons generated in the TiO₂/CdS:Mn, and hindered the access of electron donors to photoactive materials. The contribution from these aspects thus led to a significant decrease in photocurrent. Benefiting from the multiple quenching mechanism, the PEC immunosensor showed high sensitivity for CEA detection. Under optimal conditions, a low detection limit of 0.02 pg/mL and a wide linear relationship from 0.1 pg/mL to 100 ng/mL were obtained. The immunoassay showed good reproducibility and stability, and good selectivity and high accuracy in serum sample analysis. In this regard, PEC immunosensors may have great application potential for screening tumor markers and the prevention and monitoring of serious diseases.

Detection signal amplification strategies at nanomaterial-based photoelectrochemical biosensors

This review focusses on unique material modification and signal amplification strategies reported in developing photoelectrochemical biosensors with utmost sensitivity and selectivity.

Recent advances in graphene-based nanomaterials: properties, toxicity and applications in chemistry, biology and medicine

This review (with 239 refs.) summarizes the progress that has been made in applications of graphene-based nanomaterials (such as plain graphene, graphene oxides, doped graphene oxides, graphene quantums dots) in biosensing, imaging, drug delivery and diagnosis. Following an introduction into the field, a first large section covers the toxicity of graphene and its derivatives (with subsections on bacterial toxicity and tissue toxicity). The use of graphene-based nanomaterials in sensors is reviewed next, with subsections on electrochemical, FET-based, fluorescent, chemiluminescent and colorimetric sensors and probes. The large field of imaging is treated next, with subchapters on optical, PET-based, and magnetic resonance based methods. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical Abstract Schematic presentation of the potential applications of graphene-based materials in life science and biomedicine, emphatically reflected in some vital areas such as DNA analysis, biological monitoring, drug delivery, in vitro labelling, in vivo imaging, tumor target, etc.

Biomarkers-based Biosensing and Bioimaging with Graphene for Cancer Diagnosis

At the onset of cancer, specific biomarkers get elevated or modified in body fluids or tissues. Early diagnosis of these biomarkers can greatly improve the survival rate or facilitate effective treatment with different modalities. Potential nanomaterial-based biosensing and bioimaging are the main techniques in nanodiagnostics because of their ultra-high selectivity and sensitivity. Emerging graphene, including two dimensional (2D) graphene films, three dimensional (3D) graphene architectures and graphene hybrids (GHs) nanostructures, are attracting increasing interests in the field of biosensing and bioimaging. Due to their remarkable optical, electronic, and thermal properties; chemical and mechanical stability; large surface area; and good biocompatibility, graphene-based nanomaterials are applicable alternatives as versatile platforms to detect biomarkers at the early stage of cancer. Moreover, currently, extensive applications of graphene-based biosensing and bioimaging has resulted in promising prospects in cancer diagnosis. We also hope this review will provide critical insights to inspire more exciting researches to address the current remaining problems in this field.

Aptasensors as the future of antibiotics test kits-a case study of the aptamer application in the chloramphenicol detection

Antibiotics are a type of antimicrobial drug with the ubiquitous presence in foodstuff that effectively applied to treat the diseases and promote the animal growth worldwide. Chloramphenicol as one of the antibiotics with the broad action spectrum against Gram-positive and Gram-negative bacteria is widely applied for the effective treatment of infectious diseases in humans and animals. Unfortunately, the serious side effects of chloramphenicol, such as aplastic anemia, kidney damage, nausea, and diarrhea restrict its application in foodstuff and biomedical fields. Development of the sufficiently sensitive methods to detect chloramphenicol residues in food and clinical diagnosis seems to be an essential demand. Biosensors have been introduced as the promising tools to overcome the requirement. As one of the newest types of the biosensors, aptamer-based biosensors (aptasensors) are the efficient sensing platforms for the chloramphenicol monitoring. In the present review, we summarize the recent achievements of the accessible aptasensors for qualitative detection and quantitative determination of chloramphenicol as a candidate of the antibiotics. The present chloramphenicol aptasensors can be classified in two main optical and electrochemical categories. Also, the other formats of the aptasensing assays like the high performance liquid chromatography (HPLC) and microchip electrophoresis (MCE) have been reviewed. The enormous interest in utilizing the diverse nanomaterials is also highlighted in the fabrication of the chloramphenicol aptasensors. Finally, some results are presented based on the advantages and disadvantages of the studied aptasensors to achieve a promising perspective for designing the novel antibiotics test kits.

ZnO flower-rod/g-C3N4-gold nanoparticle-based photoelectrochemical aptasensor for detection of carcinoembryonic antigen

A highly sensitive and selective photoelectrochemical (PEC) aptasensor was constructed for carcinoembryonic antigen (CEA) detection based on ZnO flower-rods (ZnO FRs) modified with g-C₃N₄-Au nanoparticle (AuNP) nanohybrids. The nanohybrids of g-C₃N₄-AuNPs can improve the visible light absorbance of ZnO FRs and enhance the PEC property. We designed a sandwichlike structure formed with DNA hybridization of NH₂-probe1, CEA aptamer, and CuS-NH₂-probe2 to detect CEA. The p-type semiconductor CuS nanocrystals (NCs) at the terminational part of sandwichlike structure work as electron traps to capture photogenerated electrons and consequently lead to a magnified photocurrent change. The results indicate that the photocurrent is increased when CEA antigen (Ag) is introduced. Since the sandwichlike structure is destroyed, CuS NCs are restricted to capture photogenerated electron. The PEC aptasensor for CEA determination is ranged from 0.01 ng·mL^-1 to 2.5 ng·mL^-1 with a detection of 1.9 pg·mL^-1. The proposed aptasensor exhibits satisfactory PEC performances with rapid detection, great sensitivity and specificity. Specially, this PEC aptasensor shows a reliable result for the determination of CEA in invalid human serum compared with the ELISA method. The designed aptasensor may provide a new idea for a versatile PEC platform to determine various molecules. Graphical abstract ᅟ.

Effects of TiO2 crystal structure on the luminescence quenching of [Ru(bpy)2(dppz)]2+-intercalated into DNA

The intercalation of [Ru(bpy)₂(dppz)]²⁺ labeled as Ru(II) (bpy=2,2'-bipyridine and dppz=dipyrido[3,2,-a:2',3'-c]phenazine) into herring sperm DNA leads to the formation of emissive Ru(II)-DNA dyads, which can be quenched by TiO₂ nanoparticles (NPs) and sol-gel silica matrices at heterogeneous interfaces. The calcinations temperature exhibits a remarkable influence on the luminescence quenching of the Ru(II)-DNA dyads by TiO₂ NPs. With increasing calcinations temperature in the range from 200 to 850°C, the anatase-to-rutile TiO₂ crystal structure transformation increases the average particle size and hydrodynamic diameter of TiO₂ and DNA@TiO₂. The anatase TiO₂ has the stronger ability to unbind the Ru(II)-DNA dyads than the rutile TiO₂ at room temperature. The TiO₂ NPs and sol-gel silica matrices can quench the luminescence of the Ru(II) complex intercalated into DNA by selectively capturing the negatively DNA and positively charged Ru(II) complex to unbind the dyads, respectively. This present results provide new insights into the luminescence quenching and competitive binding of dye-labeled DNA dyads by inorganic NPs.