Bacillus licheniformis prevents and reduces anxiety-like and depression-like behaviours.

As common mental disorders, depression and anxiety impact people all around the world. Recent studies have found that the gut microbiome plays an important role in mental health. It is becoming possible to treat mental disorders by regulating the composition of the gut microbiota. Bacillus licheniformis is a probiotic used to treat gut diseases through balancing the gut microbiome during lasting years. Considering the role of gut microbiota in the gut-brain axis, this study used chronic unpredictable mild stress (CUMS) model rats to explore whether Bacillus licheniformis can prevent and treat depression and anxiety. We found that B. licheniformis reduced the depressive-like and anxiety-like behaviours of the rats during the CUMS process. Meanwhile, B. licheniformis changed the gut microbiota composition; increased the short chain fatty acids (SCFAs) in the colon, decreased kynurenine, norepinephrine, and glutamate levels; and increased the tryptophan, dopamine, epinephrine, and γ-aminobutyric acid (GABA) in the brain. After correlation analysis, we found Parabacteroides, Anaerostipes, Ruminococcus-2, and Blautia showed significant correlation with neurotransmitters and SCFAs, indicating the gut microbiome plays an important role in B. licheniformis reducing depressive-like behaviours. Therefore, this study suggested B. licheniformis may prevent depressive-like and anxiety-like behaviours while regulating the gut microbiota composition and increasing the SCFA levels in the colon to alter the levels of the neurotransmitters in the brain. KEY POINTS: • B. licheniformis reduced depressive-like and anxiety-like behaviours induced by the chronic unpredictable mild stress. • GABA levels in the brain are assonated with B. licheniformis regulating depressive-like and anxiety-like behaviours. • Gut microbiota composition alteration followed by metabolic changes may play a role in the GABA levels increase.

A ratiometric molecular imprinted electrochemiluminescence sensor based on enhanced luminescence of CdSe@ZnS quantum dots by MXene@NaAsc for detecting uric acid.

An unlabeled ratiometric molecular imprinted electrochemiluminescence sensor was developed for the determination of trace uric acid, based on MXene@NaAsc nanocomposites, CdSe@ZnS quantum dots and molecularly imprinted polymer composites modified glass carbon electrode. MXene@NaAsc stably enhanced the electron transfer and improved electrochemiluminescence intensity by acting as a base platform and signal amplifier for CdSe@ZnS quantum dots. Specific molecular imprinting cavities based on electropolymerization with o-phenylenediamine were formed to specifically identify uric acid. Combining the good sensitivity of electrochemiluminescence and the excellent selectivity of molecularly imprinted polymer, the ratio of optical signal and electrical signal was used as a comprehensive signal to achieve the detection of uric acid. Based on this, uric acid was detected in the range from 1 × 10-10 to 1 × 10-4 mol/L with the LOD of 18.13 pmol/L (S/N = 3). The developed sensor with easy preparation, great selectivity and excellent sensitivity could successfully detect uric acid in human serum.

Dynamic simulation and experimental studies of molecularly imprinted label-free sensor for determination of milk quality marker.

Bovine serum albumin (BSA) has emerged as a biomarker for mammary gland health and cow quality, being recognized as a significant allergenic protein. In this study, a novel flexible molecular imprinted electrochemical sensor by surface electropolymerization using pyrrole (Py) as functional monomer, which can be better applied to the detection of milk quality marker BSA. Based on computational results, with regard to all polypyrrole (PPy) conformations and amino-acid positions within the protein, the BSA molecule remained firmly embedded into PPy polymers with no biological changes. The molecular imprinted electrochemical sensor displayed a broad linear detection range from 1.0 × 10-4 to 50 ng·mL-1 (R2 = 0.995) with a low detection limit (LOD) of 4.5 × 10-2 pg·mL-1. Additionally, the sensor was highly selective, reproducible, stable and recoverable, suggesting that it might be utilized for the evaluation of milk quality.

Advances in novel biosensors in biomedical applications.

Biosensors, devices capable of detecting biomolecules or bioactive substances, have recently become one of the important tools in the fields of bioanalysis and medical diagnostics. A biosensor is an analytical system composed of biosensitive elements and signal-processing elements used to detect various biological and chemical substances. Biomimetic elements are key to biosensor technology and are the components in a sensor that are responsible for identifying the target analyte. The construction methods and working principles of biosensors based on synthetic biomimetic elements, such as DNAzyme, molecular imprinted polymers and aptamers, and their updated applications in biomedical analysis are summarised. Finally, the technical bottlenecks and future development prospects for biomedical analysis are summarised and discussed.

Weakly ionized gold nanoparticles amplify immunoassays for ultrasensitive point-of-care sensors.

Gold nanoparticle-based lateral flow immunoassays (AuNP LFIAs) are widely used point-of-care (POC) sensors for in vitro diagnostics. However, the sensitivity limitation of conventional AuNP LFIAs impedes the detection of trace biomarkers. Several studies have explored the size and shape factors of AuNPs and derivative nanohybrids, showing limited improvements or enhanced sensitivity at the cost of convenience and affordability. Here, we investigated surface chemistry on the sensitivity of AuNP LFIAs. By modifying surface ligands, a surface chemistry strategy involving weakly ionized AuNPs enables ultrasensitive naked-eye LFIAs (~100-fold enhanced sensitivity). We demonstrated how this surface chemistry-amplified immunoassay approach modulates nanointerfacial bindings to promote antibody adsorption and higher activity of adsorbed antibodies. This surface chemistry design eliminates complex nanosynthesis, auxiliary devices, or additional reagents while efficiently improving sensitivity with advantages: simplified fabrication process, excellent reproducibility and reliability, and ultrasensitivity toward various biomarkers. The surface chemistry using weakly ionized AuNPs represents a versatile approach for sensitizing POC sensors.

A novel real-time TMAO detection method based on microbial electrochemical technology.

Trimethylamine N-oxide (TMAO) is considered to be a novel biomarker of cardiovascular diseases. However, the traditional TMAO detection method has failed to meet the requirements of real-time and point-of-care tests. Herein, a novel TMAO detection method based on microbial electrochemical technology is established, which realizes the direct conversion of TMAO concentration into electrical signals. Attached Shewanella loihica PV-4 was first proven to be capable of simultaneous inward extracellular electron transfer and TMAO reduction. The TMAO detection method showed a wide linear range of 0 to 250 µM, a high sensitivity of 23.92 µA/mM, and a low limit of detection of 5.96 µM. In addition, the TMAO detection process was accomplished within 600 s, with an acceptable accuracy of 90% in the real serum, showing high feasibility in clinical applications.

A molecularly imprinted electrochemical sensor with tunable electrosynthesized Cu-MOFs modification for ultrasensitive detection of human IgG.

Human IgG is one of the most important immunoglobulins in the human body. The present study described the fabrication of four kinds of layer-by-layer structures of copper metal-organic frameworks (Cu-MOFs) on the working electrode by electrodeposition, which were then applied as an electrochemical sensor for the sensitive determination of IgG in serum. First, MOFs synthesized using different deposition potentials are expected to have varied morphology and properties. Herein, four copper MOFs (Cu-MOFs) were electrosynthesized by a simple and direct reduction approach. The as-synthesized Cu-MOFs exhibit varied morphology and electrocatalytic behavior. Then, IgG was employed as a template in the electropolymerization of pyrrole-imprinted films on the surface of glassy carbon electrodes. Finally, the template protein was removed to form a molecularly imprinted film with the capability to qualitatively and quantitatively signaling of IgG. Under optimized conditions, the sensor for IgG exhibits a wide detection range of 0.01-10 ng mL-1 with a limit of detection (LOD) of 3 pg mL-1 (S/N = 3). Besides, other parameters including the selectivity, reproducibility (RSD 3.6%), and recovery rate (95.2-102.0%) are all satisfactory. The practicability of the sensor was verified by detecting IgG in human serum samples, which indicated that the sensor was suitable for potential clinical applications.

[Preparation and application of melamine molecularly imprinted photonic crystal hydrogel sensor].

In this paper, molecularly imprinted photonic crystal hydrogels (MIPHs) were prepared by combining photonic crystals with molecular imprinting technology. The MIPHs were used as optical sensors for the rapid reorganization and detection of melamine in water samples. In this experiment, melamine was used as a template molecule, and the MIPHs were prepared by successive self-assembly, polymerization, and template removal. Morphological characterization by scanning electron microscopy (SEM) showed that the MIPHs possessed a highly ordered three-dimensional (3D) macroporous structure containing nanocavities. As optical sensors, the MIPHs were able to transform molecular recognition events into fluorescence signals for rapid and highly selective and sensitive recognition of the target molecule. Based on color changes of the MIPHs, the target analyte could be quickly identified by analysis with image software or even by observation with the naked eye. Under optimal conditions, the Bragg diffraction peak of the MIPHs shifted from 563 to 608 nm when exposed to melamine in mass concentrations of 10-11 to 10-6mol/L, whereas there were no obvious peak shifts when it was exposed to structural analogues of melamine.