Nanogold bioconjugates for direct and sensitive multiplexed immunosensing

Unraveling the Impact of Polyethylenimine-Coated Gold Nanoparticle Size on the Efficiency of Sandwich-Style Electrochemical Immunosensors

Sometimes, smaller size is not always better, and looking for nanomaterials that offer better device performance requires consideration of their properties at the first stage. In this study, the effects of the size of polyethylenimine-capped AuNPs (PEI-AuNPs) and proteins on the immunosensor performances, namely, sensitivity and limit of detection, are examined. The size-effect investigation of PEI-AuNPs involves their modification on the surface of disposable screen-printed carbon electrodes to support primary antibodies and their ability to load secondary antibodies and redox probes to perform amplification in the immunosensor. The correlation of the average size, electrochemical activities, protein size, and device property of PEI-AuNPs is investigated. The synthesized PEI-AuNPs with different average diameters ranging from 4.7 to 44.9 nm are employed for the investigation. When the sensor surface forms a sandwich architecture, the detection employs the current response of Ag+ ions on the PEI-AuNPs bioconjugate, which greatly increases by increasing the protein concentration. In addition, the best electrochemical signal of PEI-AuNPs or their antibody complexes with a unique AuNPs' average size allows superior signal amplification. The effect of using different sizes of target proteins on their devices is not significantly observed. Although in general small-sized nanomaterials offer high active surface areas, which can improve the electrode surface, reactivity, and device performance, we observe that the medium size of PEI-AuNPs (16.3 nm) gives the best sensitivity and detection limit of this sensor type. Therefore, the finding is useful for considering and optimizing their sizes for tunable voltammetric properties and acquiring a superior sensor.

Water-assisted synthesis of stable and multicolored CsPbX3@SiO2 core-shell nanoparticles as fluorescent probes for biosensing

Colloidal lead halide perovskite nanocrystals are highly luminescent materials with great promise as fluorescent probes in biosensing as long as their intrinsic instability in aqueous media is effectively addressed. In this study, we successfully prepared stable and multicolored CsPbX3@SiO2 (X = Cl/Br, Br and I) core-shell nanoparticles through a simple method based on the water-induced transformation of Cs4PbX6 into CsPbX3, combined with sol-gel procedures. We observed that the concentration of the Cs4PbX6 precursor plays a crucial role in the formation of isolated nanospheres with uniform silica coating and in controlling the number of core-free particles. Furthermore, our research expands this approach to other halide compositions, resulting in multicolored core-shell nanoparticles with emission wavelengths ranging from 490 to 700 nm, average sizes below 30 nm, and photoluminescence quantum yields close to 60%. Unlike in previous reports, the silica coating boosts the photoluminescence quantum yields compared to uncoated counterparts and provides increased structural stability for more than four days. Moreover, a controlled thermal treatment confers water stability to the as-synthesized nanoparticles. To establish the feasibility of the developed materials as fluorescent probes, we successfully demonstrated their specific recognition of a humanized antibody (omalizumab) used in treating patients with severe allergic asthma. This work paves the way to develop in vitro tests using CsPbX3@SiO2 core-shell nanoparticles as fluorogenic probes.

Monodispersed CsPb2Br5@SiO2 Core-Shell Nanoparticles as Luminescent Labels for Biosensing

Despite the rising advances in the field of metal halide perovskite nanocrystals (NCs), the exploitation of such nanoparticles as luminescent labels for ex vivo imaging and biosensing is still unclear and in the early stages of investigation. One of the major challenges toward the implementation of metal halide perovskite NCs in biosensing applications is to produce monodispersed nanoparticles with desired surface characteristics and compatible with aqueous environments. Here, we report the synthesis of monodispersed spherical CsPb₂Br₅@SiO₂ core-shell nanoparticles by post-synthetic chemical transformation of 3D CsPbBr₃ NCs in the presence of tetraethyl orthosilicate and a critical water/ammonia ratio. This method involves an ammonia-mediated and ammonia-induced "top-down" transformation of as-synthesized 3D CsPbBr₃ NCs to smaller CsPb2Br5 nanoclusters (ca. 2-3 nm), which trigger a seed-mediated silica growth, yielding monodispersed spherical blue luminescent (λ_emission = 432 nm) CsPb₂Br₅@SiO₂ perovskite nanoparticles. By adjusting the reaction conditions, core-shell nanoparticles of a 36.1 ± 4.5 nm diameter, which preserve their optical properties in water, were obtained. Besides that, the viability of the developed nanoparticles as a luminescent label for biosensing has been proven by specific biorecognition of the IgG protein in a direct immunoassay. Our work sheds light on the chemical processes and transformations involved in the silica nucleation mechanism in the presence of perovskite nanoparticles and opens the way for the future rational design of the next generation of semiconductor NC luminescent biological labels.

Research on the Relationship Between Schizophrenia and Excitatory Amino Acid Transporter 1 Gene Based on Nanogold Amplification Technology

Schizophrenia is one of the most common central nervous system diseases, which is caused by abnormal discharge of neurons in the brain. Its occurrence and development are affected by both genetic and environmental factors. The variation of gene level can affect the development of schizophrenia and the treatment of prognosis by affecting the susceptibility, clinical phenotype and drug response. At present, the research results of susceptibility genes screened by candidate gene association research are not consistent. The method of gene recognition on DNA was studied by QCM and nano gold composite. By using this method, the enantioselective recognition of cysteine on cyclodextrin self-assembled membrane was studied. In this study, EAAT1 gene, which is highly expressed in astrocytes, was used as a candidate gene to analyze the relationship between polymorphism and schizophrenia. The experimental results show that the introduction of nano gold can significantly improve the sensing signal, detection sensitivity and gene differentiation. In addition, this study suggested that EAAT1 gene might be a susceptibility gene of schizophrenia in the population. The results showed that a common SNP allele rs1030239-g was the risk factor (83.8% vs. 79.2%, P = 0.00067, or = 1.35, 95% CI = 1.08-1.69). The results showed that A-T-G increased the risk of schizophrenia.

Label-Free Detection of Transferrin Receptor by a Designed Ligand-Protein Sensor

Advanced detection of biomarkers in biofluids plays an important role in disease diagnosis and prognosis. Current techniques with pre-labelling suffer from high cost and complicated operation, etc. Herein, we designed a label-free electrochemical biosensor for rapid detection of transferrin receptor with desirable linear range, sensitivity, specificity, reproducibility, and stability for practical applications.

Aptamer-functionalized AuNPs for the high-sensitivity colorimetric detection of melamine in milk samples

Although aptamer-functionalized AuNPs technology exhibits great potential in analytical and biological chemistry, direct analysis of molecules at a low concentration using colorimetric assay remains challenging. The development of intuitive methods has attracted interest for promising detection of melamine in milk samples due to a demand for stable and understandable process. In this study, we propose a rapid and facile colorimetric measurement method of melamine combined aptamer-functionalized AuNPs in contaminated milk samples. To realize the high stability and the lower limit of detection, the aptamer-functionalized surface of AuNPs via a coordinated bond was used in combination with ultra-sonication. The kinetics of this colorimetric assay based on aptamer-functionalized AuNPs was analyzed to illustrate that the higher the concentration of melamine, the faster the aggregation of AuNPs induced. The sensitivity, selectivity, limit of detection and recovery rate were sufficiently validated to understand the measurement principle of melamine using aptamer-functionalized AuNPs. The calibration curve established by the absorption peak ratio (A640 /A520) was linear in the concentration range of 0~1μM of melamine in aqueous solutions with the correlation coefficient (R²) of 0.986 and the limit of detection (LOD) of 22 nM, whereas, the correlation coefficient (R²) of 0.998 and the LOD of 14.9 nM were achieved at the concentration of melamine below 0.5 μM in milk samples. The optimized performance of this colorimetric assay of melamine using aptamer-functionalized AuNPs in milk samples was obtained with 100 μL of 13 nm AuNPs solution, 40 μL of 1 μM (100 dilutions) aptamers and the pre-reaction time of 30 min. This simple colorimetric measurement of melamine using aptamer-functionalized AuNPs provides a promising target for various applications of the sample source with complex sample matrices.