ACS Central Science最新文献

Silk fibroin, recognized for its biocompatibility and modifiable properties, has significant potential in bioelectronics. Traditional silk bioelectronic devices, however, face rapid functional losses in aqueous or in vivo environments due to high water absorption of silk fibroin, which leads to expansion, structural damage, and conductive failure. In this study, we developed a novel approach by creating oriented crystallization (OC) silk fibroin through physical modification of the silk protein. This advancement enabled the fabrication of electronic interfaces for chronic biopotential recording. A pre-stretching treatment of the silk membrane allowed for tunable molecular orientation and crystallization, markedly enhancing its aqueous stability, biocompatibility, and electronic shielding capabilities. The OC devices demonstrated robust performance in sensitive detection and motion tracking of cutaneous electrical signals, long-term (over seven days) electromyographic signal acquisition in live mice with high signal-to-noise ratio (SNR >20), and accurate detection of high-frequency oscillations (HFO) in epileptic models (200-500 Hz). This work not only improves the structural and functional integrity of silk fibroin but also extends its application in durable bioelectronics and interfaces suited for long-term physiological environments.

This paper introduces the 'Spatially Focused Saline-based Pressure Sensor (SF-SaPS)', a novel soft microfluidic pressure sensor featuring a distinctive three-dimensional focusing structure. By critically reducing the cross-sectional area of the microchannel at the focused structure, the SF-SaPS achieves excellent sensitivity to pressure within the sensing region. With the spatially focused region, the SF-SaPS could detect a wide range of pressure from gentle touches to human weight, which is typically unachievable with low-conductivity sensing media such as saline, a medium inherently safe for human use. Beyond its sensitivity, the SF-SaPS exhibits sensing performance and stability comparable with conventional liquid metal-based pressure sensors. Our sensor demonstrated minimal signal drift, a rapid response time of 70 ms under cyclic loading, and 20-day long-term stability tests immersed in water. Additionally, the sensor possesses a transparency advantage unattainable by liquid metal sensors as we utilized transparent polymers and saline. A unique advantage of the SF-SaPS lies in its selective spatial and mechanical sensitivity; as the electrical resistance is highly dependent on changes in the cross-sectional area of the microchannels, the sensor has superior pressure sensitivity compared to bending and strain. Finally, various application examples highlight the SF-SaPS's advantages. By configuring the sensor in a two-axis array, the SF-SaPS facilitates pressure mapping across a plane. Additionally, it proves effective in healthcare monitoring, from radial pulse to finger movements. In conclusion, the SF-SaPS's combination of performance, stability, biocompatibility, and transparency positions this sensor as a versatile tool for applications extending beyond healthcare, as demonstrated in this study.

Screening and quantification of emerging contaminants in water is of enormous relevance due to its scarcity and harmful effects on aquatic life and human health. We present a simple and cost-effective electrochemical cell for determination of the antidepressant venlafaxine, an emerging contaminant included in the EU Watch list 2022. The cell consists of pencil leads used as electrodes and a microcentrifuge tube. Modification of the working electrode with carbon nanomaterials improved the signal. Cell-related (e.g., type of pencil leads or electroactive area) as well as experimental (e.g., pH, accumulation potential and time, and scan rate) parameters were thoroughly optimized. The adsorptive nature of venlafaxine process allowed the use of an adsorptive stripping square wave voltammetry methodology to increase the sensitivity. Under optimized variables, a linear range from 0.8 to 10 μmol L^-1 with a correlation coefficient of 0.996, a sensitivity of 1.48 μmol L^-1, a LOD of 0.4 μmol L^-1 and a RSD of 2.4 % were achieved. Selectivity was also studied, especially with respect to the main metabolite, o-desmethylvenlafaxine. The methodology distinguishes its signal from that of the main compound, allowing its determination. A similar linear range was obtained for the metabolite, with a LOD of 0.6 μmol L^-1. The platform developed was applied for venlafaxine quantification in spiked wastewaters from the Febros plant in Portugal, obtaining satisfactory recoveries. Furthermore, the versatility of pencil leads made it possible to combine them with modified paper for sampling and buffering in order to decentralize the determination, showing promising results.

Intracellular bacterial infections are a serious threat to human health due to their ability to escape immunity and develop drug resistance. Recent attention has been devoted to identifying and ablating intracellular bacteria with fluorescence probes. Aggregation-induced emission luminogens (AIEgens) photosensitizers as fluorescence probes possess excellent photostability and rapid response, which have emerged as powerful fluorescent tools for intracellular bacterial detection and antibacterial therapy. This review is intended to highlight the current advances in AIEgens on intracellular bacteria imaging and elimination, which covers topics from intracellular AIE mechanism, intracellular bacteria imaging of AIEgens to the elimination of intracellular bacteria with AIEgens. AIEgens utilized different interactions to detect intracellular bacteria, emitting bright light due to restricted intramolecular movement to visualize intracellular bacteria. Photosensitive AIEgens generate reactive oxygen species (ROS) in the aggregate state to elimate intracellular bacteria. Moreover, the prospects and application of AIEgens in intracellular bacteria imaging and elimination are also discussed, which provides insights for the development of AIE-based diagnostic and therapeutic materials and technologies.

The development of high photoactive cathode materials combined with the formation of a stable interface are considered important factors for the selective and sensitive photoelectrochemical (PEC) detection of tetracycline (TC). Along these lines, in this work, a novel type II heterostructure composed of two-dimensional (2D) covalent organic frameworks confined to zero-dimensional (0D) carbon quantum dots (CDs/COFs) film was successfully synthesized using the rapid in-situ polymerization method at room temperature. The PEC signal of CDs/COFs was significantly amplified by improving the light absorption and electron transfer capabilities. Furthermore, a cathodic molecularly imprinted PEC sensor (MIP-PEC) for the detection of TC was constructed through fast in-situ Ultraviolet (UV) photopolymerization on the electrode. Finally, a "turn-off" PEC cathodic signal was achieved based on the selective recognition of the imprinted cavity and the mechanism of steric hindrance increase. Under optimal conditions, the proposed sensor demonstrated a wide linear relationship with TC in the concentration range of 5.00 × 10^-12-1.00 × 10^-5 M, with a detection limit as low as 6.00 × 10^-13 M. Meanwhile, excellent stability, selectivity, reproducibility, and applicability in real river samples was recorded. Our work provides an effective and rapid in situ construction method for fabricating highly photoactive cathode heterojunctions and uniform stable selective MIP-PEC sensing interfaces, yielding accurate antibiotics detection in the environment.

Reluctant reproducibility and accuracy make electrochemical immunosensors suffering from high possibility of false negative/positive results, and it is the main obstacle that hinders them into an eligible alternative technology to the gold-standard method. It has been demonstrated sporadically previously that ratiometry helps deal with this issue but to what extent this could be beneficial and why it could fulfill is yet to be explored. In this study, to the best of our knowledge, for the first time, we have attempted to answer these questions through comprehensive experiments. For this purpose, labeled and label-free electrochemical immunosensors for SARS-CoV-2 pseudovirus quantification are constructed as a model electrochemical immunosensor. Conventional and ratiometric immunosensors are prepared by using electrochemically synthesized graphene modified electrodes coupled with various electrochemical probe pairs. It was found that the electrocatalyst modification at the electrode interface makes the predominant contribution to immunosensor sensitivity, while appropriate ratiometry provided electrochemical immunosensors with significantly enhanced reproducibility, accuracy, as well as sensing stability. Further, the experiments confirmed that the improvement in sensor performance achieved by ratiometry is primarily through overcoming the inherent errors and dynamic variations of the base electrode. It is also demonstrated electrochemical immunosensors made thereof could easily rival the performances of the gold-standard PCR method, in the view of immunoassay diagnosis. Therefore, it is of great promise to evolve electrochemical immunosensors into an eligible substitute technique towards the prevalent nucleic acid detection method in point-of-care testing (POCT), with the aid of electrochemical ratiometry.

Defect engineering is a promising approach to construct high performance nanozymes due to its ability to regulate their physical and chemical properties. However, how to construct defects to improve the activity of nanozymes remains a challenge. Herein, for the first time, the Chan-Lam coupling reaction is used to construct the oxygen vacancy (O_V)-rich CuMn₂O₄/carbon dots (CDs) (O_V-CuMn₂O₄/CDs) dual-function nanozymes with fluorescent (FL) and oxidase-like properties, via regulating the low-valent metal ions (Cu⁺ and Mn²⁺) and O_v contents in the spinel CuMn₂O₄ and in-situ growth of β-cyclodextrin (β-CD)-derived CDs. Expectedly, relative to CuMn₂O₄, the O_V-CuMn₂O₄/CDs exhibited 35.8%, 8.5%, and 14.6% rise in the contents of Cu⁺, Mn²⁺ and O_v, respectively. Abundant O_v provides more O₂ adsorption/activation sites, and the charge transfer between O_v and metal atoms increases the charge density around metal atoms. This produces more low-valent metals (like Cu⁺ and Mn²⁺) to promote the electron transfer from metal to O atoms and O-O bond cleavage. Thus, the oxidase-like activity of O_V-CuMn₂O₄/CDs is 4.1 times that of CuMn₂O₄. Also, the in-situ growth of β-CD-derived carbon dots on CuMn₂O₄ endows O_V-CuMn₂O₄/CDs selective target recognition. Thus, a sensitive and selective colorimetric and fluorescence dual-mode method was established for determining D-penicillamine (D-PA), with the limit of detection of 0.25 and 0.048 μM, respectively. The method was applied to D-PA determination in real samples. This work demonstrates the Chan-Lam coupling reaction can be used to construct high performance nanozymes for developing dual-mode sensor for the detection of targets.

The functionalization of gold nanoparticle (AuNP) is the key procedure for the biochemical and biomedical application. The conventional salt-aging method requires the stepwise additions of NaCl and excessive thiolated DNA, mainly due to the poor tolerance of the DNA/AuNP mixture toward NaCl. Herein, we found that NaF is capable of improving the stability for the modification of AuNP with different bases of DNA sequences (poly A/T/C/G), and allows for adding up with a high concentration of 200 mM at one time, which greatly reduces the total modification time to 0.5-1 h. Intriguingly, the introduction of NaBr effectively increases the DNA loading capacity. Besides the advantages of NaF and NaBr, the modification performance is improved via the introduction of the oligo A/T spacer for the G-rich DNA sequences. Furthermore, this method shows the superiority to another two methods (pH 3-based and salt-aging) in terms of the loading capacity or sequence components.