Cell-based Biosensors Research Articles

Cell Patterning Technology on Polymethyl Methacrylate through Controlled Physicochemical and Biochemical Functionalization.

In recent years, innovative cell-based biosensing systems have been developed, showing impact in healthcare and life science research. Now, there is a need to design mass-production processes to enable their commercialization and reach society. However, current protocols for their fabrication employ materials that are not optimal for industrial production, and their preparation requires several chemical coating steps, resulting in cumbersome protocols. We have developed a simplified two-step method for generating controlled cell patterns on PMMA, a durable and transparent material frequently employed in the mass manufacturing of microfluidic devices. It involves air plasma and microcontact printing. This approach allows the formation of well-defined cell arrays on PMMA without the need for blocking agents to define the patterns. Patterns of various adherent cell types in dozens of individual cell cultures, allowing the regulation of cell-material and cell-cell interactions, were developed. These cell patterns were integrated into a microfluidic device, and their viability for more than 20 h under controlled flow conditions was demonstrated. This work demonstrated the potential to adapt polymeric cytophobic materials to simple fabrication protocols of cell-based microsystems, leveraging the possibilities for commercialization.

Stand-alone floating microbial fuel cell-based biosensor for tracking organic pollution influx

Organic wastewater discharge is an alarming issue with freshwater lakes and rivers. This research developed a self-powered stand-alone floating biosensor based on a microbial fuel cell (MFC) for early organic wastewater detection. The MFC case was fabricated by a 3D printer, and the electrodes were fabricated from low-cost carbon-based materials. Soil containing electrogenic bacteria was loaded on the anode to increase the sensitivity and stability of the biosensor. In this research, chemical oxygen demand (COD) was used to represent the organic content of water. Experimental data showed a linear relationship between the COD of water and the output voltage of the MFC. Moreover, an energy harvesting circuit equipped with a flashing light-emitting diode (LED) was powered by the MFC. The LED started to flash when the COD of water was about 60 mg/L, and the flashing pace increased as the COD increased. As a result, organic content in water could be detected by the device and visually represented through the flashing pace of the LED. This solution potentially enables a simple and low-cost measure for water quality control at the input of freshwater lakes and rivers.

(Invited) Development of Cell-Based Biosensor Platform for Monitoring the Effect of Functional Nanocarriers As Drug Delivery System on Breast Cancer Cells

With the rapid emerging research of nanotechnology and engineering in biomedical applications, scientists start to develop state-of-the-art diverse biosensing platforms. Here, in-vitro cell-based biosensor (CBB) was fabricated using nano/micro technologies to electrophysiologically observe the effects of drug treatment on human breast cancer cells. Indium tin oxide coated vertically aligned silicon nanowires (ITO-coated VA-SiNWs) were applied as a cell monitoring CBB platform to investigate the growth and adhesion of MCF-7 human breast cancer cells via impedimetric method. Monitoring was performed by measuring the non-Faradaic electrical impedance of the cell–APTMS-modified ITO-coated VA-SiNWs system using a precision LCR meter. Our APTMS-modified ITO-coated VA-SiNWs exhibited changes in impedance parameters during cell growth. It was observed that during MCF-7 cell growth, the impedance magnitude increased. By contrast, the cytolysis of the cells led to significant changes in impedance parameters. Impedimetric cell monitoring platform has the ability to observe MCF-7 cell growth and adhesion and investigate anomalous and non-electrogenic cell behavior in toxin and drug screenings. With the aid of CBB platform, the real-time electrical signals can be applied to monitor the therapeutic efficacy of the nanocarriers in drug delivery system and screening large libraries of potential drugs for cancer treatment. Moreover, our pilot study indicates that our CBB could be a feasible platform to reduce/replace the use of animals based on the “Three R principles” in animal-based research in the future. Figure 1

Organic Electrochemical Transistors (OECTs): Advancements and Exciting Prospects for Future Biosensing Applications

Over the past few decades, the field of organic electronics has depicted proliferated growth, due to the advantageous characteristics of organic semiconductors, such as tunability through synthetic chemistry, simplicity in processing, cost-effectiveness, and low-voltage operation, to cite a few. Organic electrochemical transistors (OECTs) have recently emerged as a highly promising technology in the area of biosensing and flexible electronics. OECT-based biosensors are capable of sensing brain activities, tissues, monitoring cells, hormones, DNAs, and glucose. Sensitivity, selectivity, and detection limit are the key parameters adopted for measuring the performance of OECT-based biosensors. This article highlights the advancements and exciting prospects of OECTs for future biosensing applications, such as cell-based biosensing, chemical sensing, DNA/ribonucleic acid (RNA) sensing, glucose sensing, immune sensing, ion sensing, and pH sensing. OECT-based biosensors outperform other conventional biosensors because of their excellent biocompatibility, high transconductance, and mixed electronic–ionic conductivity. At present, OECTs are fabricated and characterized in millimeter and micrometer dimensions, and miniaturizing their dimensions to nanoscale is the key challenge for utilizing them in the field of nanobioelectronics, nanomedicine, and nanobiosensing.

Umami taste evaluation based on a novel mouse taste receptor cell-based biosensor

Umami, a taste sensation known for its savory and delicious properties, has garnered considerable attention from both consumers and the food industry. However, current understanding and evaluation of umami characteristics remain limited, presenting a long-standing issue. To address this challenge, we have developed a self-assembled biosensor based on matured taste receptor cells (TRCs), obtained through isolation and culture of taste stem cells. TRCs, as the recognition element, were mounted onto the surface of a glassy carbon electrode (GCE) treated with gold nanoparticles (AuNPs) and poly-L-lysine (PLL). Key parameters including the cell incubation time and concentration were optimized to ensure the optimal performance of the TRCs-based biosensor. AuNPs were deposited onto the GCE surface via 90 s electrochemical reduction. TRCs concentration of 106 cells/mL and incubation time of 12 h were chosen by electrochemical characterization. Using this novel, rapid, and sensitive TRCs-based biosensor, we successfully detected L-monosodium glutamate (MSG) and other umami substances, demonstrating a good linear relationship within the range of 10−9 – 10−5 M between response signals and concentration of MSG stimuli. Our results provide insights into taste signal transduction mechanisms and suggest the potential for biomimetic sensors in intelligent perception applications.

Microbial fuel cell-based biosensor for monitoring anaerobic biodegradation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

Poly-3-hydroxybutyrate-co-4-hydroxybutyrate (P34HB) polymer, which is a common type of polyhydroxyalkanoates (PHAs), may provide alternative solutions to the white pollution issues. In this study, its anaerobic biodegradation was investigated through the microbial fuel cell (MFC) system, by monitoring several parameters, including the time-dependent changes in the electrical signals, the concentration of the P34HB degradation products, biogas production, the weight loss of P34HB films, and the morphological and chemical structure of the test materials during the degradation. Notably, the electrical signal was selected as an indicator to online monitor the anaerobic biodegradation of P34HB films. After 40 days of degradation, the coulombic yield biodegradability (Q-biodegradability) of P34HB films reached 37.59%. A linear relationship among the weight loss biodegradability of P34HB films and Q-biodegradability with high correlation coefficient of R2 = 0.998 was established. The results suggested that the anaerobic biodegradability of P34HB films can be efficient measured by using the Q-biodegradability compared to conventional methods. Microbial community analysis also indicated that the genus Desulfovibrio and Enterobacter contributed to the biodegradation of P34HB films and the electrical signals production via the cooperation among other microorganisms. This study presented the online monitoring of the anaerobic biodegradation of P34HB films through MFC-based sensors, which provided an alternative approach to evaluate the anaerobic biodegradability of biodegradable plastics.

Tuning the sensitivity of cell-based biosensors for the detection of biocides

The presence of biocides in wastewater can negatively impact the efficiency of wastewater treatment processes, particularly the process of nitrification. In this paper, we describe the development of cell-based biosensors (CBBs) with tunable levels of sensitivity for rapidly detecting the presence and predicting the type and concentration of biocides. The CBB assay developed is performed by first exposing a panel of bacterial strains (E. coli, B. subtilis, B. cereus) to the sample being tested and to the control sample without biocide, and then adding a fluorescent dye (LIVE/DEAD BacLight). We then compare the fluorescence signals generated by the two samples, and the differences in the signals indicate the presence of a biocide, as previously reported in the literature. We found that the sensitivity of the CBB assay can be improved by 'tuning' the type/salinity of the buffer used to suspend the cells, and by changing the number of cells used in the assay. These changes improved the level of detection (LOD) of the biocide Cetyltrimethylammonium bromide (CTAB) from 10 ppm to 0.625 ppm and the biocide Grotan® BK from 500 ppm to 7.8 ppm. With the optimized conditions for each strain, we also establish that the combined response from the panel of bacterial strains can be used to predict the type and concentration of biocide sample tested. Additionally, we provide evidence that the CBB assay can be performed using a compact, commercially available fluorometer. Overall, the significance of this work will improve point-of-use testing and enable the discrimination between biocide-containing samples of similar toxicity and detection of lower toxicity samples, thereby improving the accuracy of the CBB assay.

Nanozyme can substitute a natural Ogataea polymorpha catalase enzyme in vivo.

Nanomaterials possessing artificial, enzyme-like catalytic activity (nanozymes, NZs) have a great potential for application in research, immunological assays, biosensors, in vivo imaging, and as therapeutic agents. Despite the obvious advances in construction and understanding of functional properties of NZs, there is still no clear evidence of whether they can complement the loss of corresponding enzymatic activity in vivo. Herein, we report the first, to the best to our knowledge, example of successful substitution of natural enzyme activity by catalase-like platinum (nPt) and platinum-gold (nPtAu) nanoparticles transferred to the cells of methylotrophic yeast Ogataea polymorpha. The nPt NZs were synthesized by the chemical reduction method and used as a seed to produce the nPt(core)Au(shell) particles. The produced nPt NZs were 68.1 and 91.3 nm in size, while the hydrids were of 531.2 and 615.1 nm. Both nPt and nPtAu demonstrated catalase activity in vitro. The catalase-deficient strain Ogataea polymorpha C-105 was shown to be able to grow on methanol and a mixture of glucose and methanol in the presence although not in the absence of NZs, this correlating with the decrease in intracellular hydrogen peroxide production. The results provide the first example of complementation of the natural enzyme function by synthetic NZs, the phenomenon which can further be used in a screening for new catalase-like nanozymes and as a fruitful tool to modify living cells by nanoparticles possessing catalytic activity and to use such modified cells as sensitive elements in cell-based biosensors.

Nanofabrication Technologies to Control Cell and Tissue Function in Three-Dimension.

In the 2000s, advances in cellular micropatterning using microfabrication contributed to the development of cell-based biosensors for the functional evaluation of newly synthesized drugs, resulting in a revolutionary evolution in drug screening. To this end, it is essential to utilize cell patterning to control the morphology of adherent cells and to understand contact and paracrine-mediated interactions between heterogeneous cells. This suggests that the regulation of the cellular environment by means of microfabricated synthetic surfaces is not only a valuable endeavor for basic research in biology and histology, but is also highly useful to engineer artificial cell scaffolds for tissue regeneration. This review particularly focuses on surface engineering techniques for the cellular micropatterning of three-dimensional (3D) spheroids. To establish cell microarrays, composed of a cell adhesive region surrounded by a cell non-adherent surface, it is quite important to control a protein-repellent surface in the micro-scale. Thus, this review is focused on the surface chemistries of the biologically inspired micropatterning of two-dimensional non-fouling characters. As cells are formed into spheroids, their survival, functions, and engraftment in the transplanted site are significantly improved compared to single-cell transplantation. To improve the therapeutic effect of cell spheroids even further, various biomaterials (e.g., fibers and hydrogels) have been developed for spheroid engineering. These biomaterials not only can control the overall spheroid formation (e.g., size, shape, aggregation speed, and degree of compaction), but also can regulate cell-to-cell and cell-to-matrix interactions in spheroids. These important approaches to cell engineering result in their applications to tissue regeneration, where the cell-biomaterial composite is injected into diseased area. This approach allows the operating surgeon to implant the cell and polymer combinations with minimum invasiveness. The polymers utilized in hydrogels are structurally similar to components of the extracellular matrix in vivo, and are considered biocompatible. This review will provide an overview of the critical design to make hydrogels when used as cell scaffolds for tissue engineering. In addition, the new strategy of injectable hydrogel will be discussed as future directions.

Engineering Modular and Highly Sensitive Cell-Based Biosensors for Aromatic Contaminant Monitoring and High-Throughput Enzyme Screening.

Although a variety of whole-cell-based biosensors have been developed for different applications in recent years, most cannot meet practical requirements due to insufficient sensing performance. Here, we constructed two sets of modular genetic circuits by serial and parallel modes capable of significantly amplifying the input/output signal in Escherichia coli. The biosensors are engineered using σ54-dependent phenol-responsive regulator DmpR as a sensor and enhanced green fluorescent protein as a reporter. Cells harboring serial and parallel genetic circuits displayed nearly 9- and 16-fold higher sensitivity than the general circuit. The genetic circuits enabled rapid detection of six phenolic contaminants in 12 h and showed the low limit of detection of 2.5 and 2.2 ppb for benzopyrene (BaP) and tetracycline (Tet), with a broad detection range of 0.01-1 and 0.005-5 μM, respectively. Furthermore, the positive rate was as high as 73% when the biosensor was applied to screen intracellular enzymes with ester-hydrolysis activity from soil metagenomic libraries using phenyl acetate as a phenolic substrate. Several novel enzymes were isolated, identified, and biochemically characterized, including serine peptidases and alkaline phosphatase family protein/metalloenzyme. Consequently, this study provides a new signal amplification method for cell-based biosensors that can be widely applied to environmental contaminant assessment and screening of intracellular enzymes.

A highly selective cell-based fluorescent biosensor for genistein detection

Genistein, an isoflavone found mainly in legumes, has been shown to have numerous health benefits for humans. Therefore, there is substantial interest in producing it using microbial cell factories. To aid in screening for high genistein producing microbial strains, a cell-based biosensor for genistein was developed by repurposing the Gal4DBD-ERα-VP16 (GEV) transcriptional activator in Saccharomyces cerevisiae. In the presence of genistein, the GEV sensor protein binds to the GAL1 promoter and activates transcription of a downstream GFP reporter. The performance of the biosensor, as measured by fold difference in GFP signal intensity after external genistein induction, was improved by engineering the sensor protein, its promoter and the reporter promoter. Biosensor performance increased when the weak promoter REV1p was used to drive GEV sensor gene expression and the VP16 transactivating domain on GEV was replaced with the tripartite VPR transactivator that had its NLS removed. The biosensor performance further improved when the binding sites for the inhibitor Mig1 were removed from and two additional Gal4p binding sites were added to the reporter promoter. After genistein induction, our improved biosensor output a GFP signal that was 20 times higher compared to the uninduced state. Out of the 8 flavonoids tested, the improved biosensor responded only to genistein and in a somewhat linear manner. The improved biosensor also responded to genistein produced in vivo, with the GFP reporter intensity directly proportional to intracellular genistein concentration. When combined with fluorescence-based cell sorting technology, this biosensor could facilitate high-throughput screening of a genistein-producing yeast cell factory.

Detecting physiological concentrations of Alzheimer's associated amyloid-β oligomers with a cell-based response.

Alzheimer's disease (AD) is characterized by blood-brain barrier (BBB) breakdown and neuronal cell death, associated with aggregated amyloid-β (Aβ) plaques deposited around brain vasculature and within the brain. Changes in the brain occur up to 20 years before symptoms arise; however, there is currently no pre-symptomatic detection method available for AD. An intact BBB requires tight junctions (TJ) that render relatively high transendothelial electrical resistance (TEER). AD-associated breakdown of the BBB correlates with vascular Aβ deposition, suggesting that aggregated, pathological Aβ can modulate TEER. We explore leveraging this cellular response for early disease diagnosis via detection of early Aβ aggregates. Primary human brain microvascular endothelial cells (HBMVECs) were cultured on a suspended membrane and supplemented to mimic the BBB. Once TEER values reflected TJ formation, HBMVEC monolayers were treated with oligomeric Ab at picomolar to nanomolar concentrations, and TEER was monitored. Oligomeric Aβ at picomolar and nanomolar concentrations, but not monomer, induced a reduction of TEER and disruption of TJs. These results demonstrate that pathogenic Aβ aggregates are uniquely responsible for inducing endothelial monolayer permeability and reducing monolayer electrical resistance, and this response can be detected at physiological concentrations. This work also validates that introduction of physiologically active Aβ oligomers can increase permeability of an endothelial monolayer, while non-pathogenetic monomer is inert. These results provide evidence that oligomers, the pathogenic form of Aβ, selectively break down the BBB. Future work will include establishing a threshold of Aβ oligomer concentrations that reduce TEER to establish cellular sensitivity, and sensitizing cells to obtain a more pronounced response. Translation of this experimental system to a cell-based biosensor platform will lay the groundwork for the development of cost-effective, early AD detection.

A Multiplex Molecular Cell-Based Sensor to Detect Ligands of PPARs: An Optimized Tool for Drug Discovery in Cyanobacteria.

Cyanobacteria produce a wealth of secondary metabolites. Since these organisms attach fatty acids into molecules in unprecedented ways, cyanobacteria can serve as a novel source for bioactive compounds acting as ligands for Peroxisome Proliferator-Activated Receptors (PPAR). PPARs (PPARα, PPARβ/δ and PPARγ) are ligand-activated nuclear receptors, involved in the regulation of various metabolic and cellular processes, thus serving as potential drug targets for a variety of pathologies. Yet, given that PPARs' agonists can have pan-, dual- or isoform-specific action, some controversy has been raised over currently approved drugs and their side effects, highlighting the need for novel molecules. Here, we expand and validate a cell-based PPAR transactivation activity biosensor, and test it in a screening campaign to guide drug discovery. Biosensor upgrades included the use of different reporter genes to increase signal intensity and stability, a different promoter to modulate reporter gene expression, and multiplexing to improve efficiency. Sensor's limit of detection (LOD) ranged from 0.36-0.89 nM in uniplex and 0.89-1.35 nM in multiplex mode. In triplex mode, the sensor's feature screening, a total of 848 fractions of 96 cyanobacteria extracts were screened. Hits were confirmed in multiplex mode and in uniplex mode, yielding one strain detected to have action on PPARα and three strains to have dual action on PPARα and -β.

Application of the Luminescent luxCDABE Gene for the Rapid Screening of Antibacterial Substances Targeting Pseudomonas aeruginosa.

Pseudomonas aeruginosa (P. aeruginosa) is a typical Gram-negative bacterium that can cause the spoilage of catered food products. Using a luminescent reporter gene (luxCDABE), this study sought to construct a cell-based biosensor (PAO1-CE) to rapidly screen antibacterial substances against P. aeruginosa. A total of six antibiotics belonging to five categories were used as the model test substances. The results of the bioluminescence detection method were verified using traditional antibacterial research assessments. The correlation coefficient of the regression equation fitting the data generated using this method was greater than 0.98, supporting the credibility of this approach. Additionally, the EC50 of each of the antibiotics assessed in this study was lower than the 1/2 MIC determined by conventional means. All six of the antibiotics caused varying degrees of damage to the cell membrane and cell wall of P. aeruginosa. Importantly, this novel method helped shorten the time necessary for active-compound detection and could be used for high-throughput detection, which would also help improve the detection efficiency. The application of this method towards the discovery of novel antibacterial compounds targeting P. aeruginosa holds substantial promise for greatly improving the efficiency of compound discovery.

A High-Performance Hybrid Biofuel Cell with a Honeycomb-Like Ti3 C2 Tx /MWCNT/AuNP Bioanode and a ZnCo2 @NCNT Cathode for Self-Powered Biosensing.

This work focusses on developing a hybrid enzyme biofuel cell-based self-powered biosensor with appreciable stability and durability using murine leukemia fusion gene fragments (tDNA) as a model analyte. The cell consists of a Ti3 C2 Tx /multiwalled carbon nanotube/gold nanoparticle/glucose oxidase bioanode and a Zn/Co-modified carbon nanotube cathode. The bioanode uniquely exhibits strong electron transfer ability and a high surface area for the loading of 1.14×10-9 molcm-2 glucose oxidase to catalyze glucose oxidation. Meanwhile, the abiotic cathode with a high oxygen reduction reaction activity negates the use of conventional bioenzymes as catalysts, which aids in extending the stability and durability of the sensing system. The biosensor offers a 0.1 fm-1nm linear range and a detection limit of 0.022fm tDNA. Additionally, the biosensor demonstrates a reproducibility of ≈4.85% and retains ≈87.42% of the initial maximal power density after a 4-week storage at 4°C, verifying a significantly improved long-term stability.

Development of novel Escherichia coli cell-based biosensors to monitor Mn(II) in environmental systems.

Escherichia coli uses manganese [Mn(II)] as an essential trace element; thus, it has a genetic system that regulates cellular Mn(II) levels. Several genes in the mnt-operon of E. coli respond to intercellular Mn(II) levels, and transcription is regulated by a transcription factor (MntR) that interacts with Mn(II). This study aimed to develop Mn(II)-sensing biosensors based on mnt-operon genetic systems. Additionally, the properties of biosensors developed based on the promoter regions of mntS, mntH, and mntP were investigated. MntR represses the transcription of MntS and MntH after binding with Mn(II), while it induces MntP transcription. Thus, Mn(II) biosensors that decrease and increase signals could be obtained by fusing the promoter regions of mntS/mntH and mntP, with egfp encoding an enhanced green fluorescent protein. However, only the biosensor-based mntS:egfp responded to Mn(II) exposure. Further, E. coli harboring P mntS :egfp showed a concentration-dependent decrease in fluorescence signals. To enhance the sensitivity of the biosensor toward Mn(II), E. coli containing a deleted MntP gene that encodes Mn(II) exporter, was used as a host cell for biosensor development. The sensitivity toward Mn(II) increased by two times on using E. coli-mntP, and the biosensor could quantify 0.01-10 μM of Mn(II). Further, the applicability of Mn(II) in artificially contaminated water samples was quantified and showed >95% accuracy. The newly developed Mn(II) biosensors could detect and quantify the residual Mn(II) from mancozeb in soil samples, with the quantification accuracy being approximately 90%. To the best of our knowledge, this is the first Mn (II)-specific bacterial cell-based biosensor that serves as a valuable tool for monitoring and assessing the risks of Mn(II) in environmental systems.

BIOSENSOR FOR THIAMINE DETECTION USING YEAST SACCHAROMYCES CEREVISIAE

Nowadays, people's lifestyles have undergone significant changes, such as decreased physical activity and increased sedentary behavior, as well as an increase in nutritionally unbalanced diets, especially in vitamin B1 (thiamine) intake. Deficiency and excess of thiamine can cause various diseases. Based on this, it is important to know the level of thiamine intake in dietary supplements and medicines. This study used a biosensor with amperometric principles to determine the effect of thiamine on the yeast Saccharomyces cerevisiae as a cell model. Measurements were made by adding controlled vitamins to cell metabolic activity using an amperometric biosensor based on Pt/Ag electrodes. An amperometric biosensor will measure the current from a reduction and oxidation reaction with a constant potential. The effect of adding vitamins to yeast cells was observed in the form of cellular respiration, which was expressed as a parameter of dissolved oxygen level (DO). Vitamins used as samples were given various concentrations of 30 mM, 45 mM, and 60 mM. The addition of thiamine causes an increase in the potential value for each increase in concentration, indicating that DO levels in the cell environment have decreased due to yeast cells consuming O2 during the respiration process. The results of this study indicate that yeast cell-based biosensors can detect variations in the concentration of thiamine for further health applications.

An engineered (CAGA)12-EGFP cell-based biosensor for high-content and accurate detection of active TGF-β

Transforming growth factor-β (TGF-β) regulates multiple fundamental physiological processes and is closely related to severe diseases such as cancer, fibrosis, immune disorders and cardiovascular diseases. TGF-β is thus an important biomarker for clinical diagnosis and prognosis, and a crucial target for therapeutics development. Here we describe a high-content, serum-free, easy-to-use, and cost-effective (CAGA)12-EGFP cell-based biosensor for accurate measurements of active TGF-β. Together with non-destructive and continuous measurement protocol and data processing method established here, the biosensor is capable of detecting active TGF-β1 in the range of 0.024–6.25 ng/mL concentration with >91% accuracy and high repeatability. Overall, the engineered (CAGA)12-EGFP biosensor is a powerful tool for detection of active TGF-β and for mechanistic study of the TGF-β pathway. The greatly reduced cost and operating simplicity also makes it a highly potent in vitro platform for high-throughput screening of anti-TGF-β therapeutics.

An integrated 3D cell-based electrochemical biosensor for neurotoxicity assessment of organophosphorus pesticides

This work presents an integrated three-dimensional (3D) cell-based electrochemical biosensor to assess the neurotoxicity of organophosphorus pesticides (OPs). In this system, OPs inhibit the activity of intracellular acetylcholinesterase (AChE), and thus the enzymatic hydrolysate 1-naphthol (1-N) presents a declining trend. The fluctuation of the 1-N electrochemical response is proved to be a reliable indicator to evaluate the OPs neurotoxicity. Gelatin methacrylate hydrogel is introduced as a scaffold for the 3D culture of PC12 cells, providing an in vivo-like environment for toxicological evaluation. Meanwhile, zeolite imidazolate framework-67@CoAl layered double hydroxides/multi-walled carbon nanotube composites devolve the screen-printed carbon electrode with significant sensitivity. The cell culture and electrochemical detection processes are integrated into a 3D-printed platform, facilitating the portability and timeliness of testing. Under optimal experimental conditions, the detection limit and linear range of 1-N are found as 0.148 μM and 0.5–150 μM, respectively. The proposed sensor is applied to assess the neurotoxicity of three typical OPs (chlorpyrifos, dimethoate, and isocarbophos), and the results are further confirmed with the conventional Ellman's method. With the comparatively high sensitivity, reliability, and simplicity provided, the fabricated sensor exhibits broad prospects in the field of neurotoxicity evaluation.

Photofuel cell-based self-powered biosensor for HER2 detection by integration of plasmonic-metal/conjugated molecule hybrids and electrochemical sandwich structure

Human epidermal growth factor receptor 2 (HER2) has been regarded as the considerable biomarker of breast and gastric cancer. Thus, precise detection of HER2 is of significance for the early diagnosis and treatment. Here, a photofuel cell-based self-powered biosensor (PFC-SPB) was constructed for the ultrasensitive HER2 detection, which was composed of a plasmonic gold nanoparticles (Au NPs)/organic semiconductor hybrid photoanode and a cathode with biosensing strategy of electrochemical sandwich structure. The localized surface plasmon resonance effect of Au NPs can obviously enhance the separation efficiency of photo-generated electron/hole pair, which was beneficial to the sensitivity and stability of PFC-SPB. Meanwhile, the cathodic sandwich structure not only was used for the target recognition, but also can guarantee the enrichment of electroactive molecules (molybdophosphate). Consequently, with the open circuit voltage (EOCV) as the output signal, the PFC-SPB can achieve the HER2 detection in the range of 0.1–500 pg mL−1 with a low detection limit of 0.02 pg mL−1. Moreover, the as-proposed bioassay can be applied in cell lysate sample without any pretreatment, providing a promising and powerful tool early clinical diagnosis of cancer.