Detection Of Target Analytes Research Articles

Fabrication of polydopamine functionalized AgNF SERS substrate: Applications for sensitive detection of nivalenol in food samples and cell biocompatibility

Surface-enhanced Raman spectroscopy (SERS) is a robust analytical tool applicable for the quick and accurate determination of mycotoxins. However, there hasn't been any attempt to use SERS for the quantitative detection of nivalenol (NIV) thus far. To improve the Raman signals of NIV, we fabricated a polydopamine-coated silver nanoflower (PDA-AgNFs) SERS substrate with strong “hot-spots”. The PDA-AgNFs substrates showed superior SERS enhancement activities in the target analyte detection and quantification. It produced good substrate uniformity (relative standard deviation of SERS signals, RSD = 4.1% for substrate-to-substrate test, and 3.24% for spot-to-spot test), an enhancement factor of 2.87 × 106 towards rhodamine 6B (R6G), and detection sensitivity as low as 1 femtomolar (10−15 M) against R6G probe molecule. Moreover, the PDA-AgNFs SERS substrates were successfully used, for the first time, to detect NIV in corn, horse beans, and mushroom samples. The calibration curve showed a satisfactory linear fit based on the SERS intensities of different NIV concentrations. The detection limit (LOD) for the suggested approach was 0.22 nM (S/N = 3). Interestingly, the MTT assay experiment demonstrated that PDA-AgNFs had no toxicity against mammalian NIH-3T3 cells. The biocompatible PDA-AgNFs substrates with intense plasmonic effects and binding sites demonstrated impressive Raman enhancement, and could serve as an effective, label-free, and fast SERS-based analysis of NIV in real samples.

Three-in-one polarization detector enabled by metasurface

In the field of biomedicine, the detection of target analytes imposes requirements on polarization information detection and sensitivity. It necessitates non-destructive analysis of proteins and DNA. The combination of dielectric geometric metasurface with terahertz (THz) vortex beams present new opportunities for biomedical sensing. In this work, we employ simulation to demonstrate a novel methodology that integrates off-axis dual-focus with vector vortex beams (VVB). Moreover, the metasurface-based method provides potential solutions for miniaturized polarization detection. The capability of polarization detection is evaluated using different polarization states at three different focal planes. Specifically, the ellipticity and handedness of incident THz waves can be determined by the electric field intensity ratio of the two off-axis focused spots. The major axis direction of linear polarization waves can be determined by extracting the azimuth of the VVB. It is worth mentioning that higher-order VVB, benefiting from its high angular resolution characteristics, exhibits enhanced sensitivity in determining the direction of major axes. Our proposed scheme offers potential applications for THz communications, medical imaging, security detection and remote sensing.

SERS aptasensor utilizing aptamer-conformation-mediated regulation of Au dumbbell dimers for the ultrasensitive detection of β-phenethylamine in foods

Surface-enhanced Raman spectroscopy (SERS) is a powerful tool for the detection of target analytes in foods, with the realization of “hot spots” between plasmonic metal nanoparticles (NPs) being critical for ultrasensitive detection. Herein, we proposed a new aptamer conformation-mediated SERS “hot spots” strategy. Au NPs were functionalized with strands of complementary DNA containing β-phenethylamine aptamers and the Raman reporter 4-mercaptobenzonitrile (4-MBN). This allowed DNA-driven self-assembly of an Au dumbbell dimer-based SERS aptasensor for the detection of the β-phenethylamine. After selective recognition of β-phenethylamine by the aptamer, the aptamer folded, bringing AuNPs in the dimers close together to create SERS “hot spots”. This produced an intense SERS signal in the “biologically silent” region for 4-MBN (2225 cm−1), the intensity of which increased linearly with the logarithm of the β-phenethylamine concentration. Under the optimized conditions, the linear range of SERS aptasensor was 10−6 to 10−2 mg L−1, with a low limit of detection of 3.8 × 10−7 mg L−1. Further, the developed SERS aptasensor was successfully employed to determine the β-phenethylamine in a range of food samples, with the results being identical to those obtained using a high-performance liquid chromatography method.

Plasmonic immunosensors based on spoon-shaped waveguides for fast and on-site ultra-low detection of ochratoxin A in coffee samples

The high toxicity and occurrence of ochratoxin A (OTA) in grains and foods has been a growing concern due to the impacts on health and the economy in many countries. In this sense, simplified devices with high sensitivity and specificity for local monitoring are enthusiastically pursued. In this work, we report for the first time the detection of ochratoxin A in coffee samples using a spoon-shaped waveguide immunosensor. The biosensor was built with the surface of the spoon-shaped waveguide covered by a 60 nm layer of gold to enable the SPR phenomenon. The measurements indicated a linear relationship between the change in the SPR phenomenon values and the OTA concentration in the range from 0.2 ppt to 5 ppt. When analyzed in coffee samples, the biosensor was highly selective and did not suffer matrix interference. The developed biosensor represents a promising analytical device for coffee quality analyses, as it is portable, simple, and suitable for onsite detection of target analytes.

Fabrication of a graphite-paraffin carbon paste electrode and demonstration of its use in electrochemical detection strategies.

Electrochemical detection methods hold many advantages over their optical counterparts, such as operation in complex sample matrices, low-cost and high volume manufacture and possible equipment miniaturisation. Despite these advantages, the use of electrochemical detection is currently limited in the clinical setting. There is a wide range of potential electrode materials, selected for optimal signal-to-noise ratios and reproducibility when detecting target analytes. The use of carbon paste electrodes (CPEs) for electrochemical detection can be limited by their analytical performance, however they remain very attractive due to their low cost and biocompatibility. This paper presents the fabrication of an easy-to-make and use graphite powder/paraffin wax paste combined with a substrate produced via additive manufacturing and confirms its functionality for both direct and indirect electrochemical measurements. The produced CPEs enable the direct voltammetric detection of hexaammineruthenium(III) chloride and dopamine at an experimental limit of detection (ELoD) of 62.5 μM. The key inflammatory biomarker Interleukin-6 through an enzyme-linked immunosorbant assay (ELISA) was also quantified, yielding a clinically-relevant ELoD of 150 pg ml-1 in 10% human serum. The performance of low-cost and easy-to-use CPEs obtained in 0.5 hours is showcased in this study, demonstrating the platform's potential uses for point-of-need electroanalytical applications.

A Biosensing Platform Based on Metamaterials BioNEMS for Lab-on-Chip Systems.

An optical nanoelectromechanical platform relied on a SRR metamaterial system is presented in this paper as a label-free biosensor. This structure includes a flexible BioNEMS (Bio-Nano-Electro-Mechanical Systems) transducer and a proposed SRR metamaterials for detection of biological changes. Metamaterial cells consist of two parts which are coupled with an air gap distance. A functionalized BioNEMS beam supports one part of the proposed metamaterial cells. When patient samples including target analytes is exposed to the NEMS beam surface, the specific bio-interactions are happened and the energy (surface stress type) is released on the surface. This energy, which is induced only to the one side of the movable beam, causes a differential surface stress and thus displaces the nanomechanical beam. As a result, the air distance between two separated cells of the metamaterial unit is changed. This leads to varying the cell coupling effect which excites plasmon modes in a different wavelength. Therefore, biological quantities can be measured by detecting the resonance wavelength changes. Moreover, analyzing the device by various approaches results its functional characteristics as follows: detection sensitivity of 4251 nm/RIU, figure of merit (FOM) of 500.1 RIU -1 , mechanical sensitivity of [Formula: see text]/Nm -1 and resonant frequency of 17.1 kHz. Consequently, this mechanism is important for label-free biosensing due to its high potential for sensitive and quantitative detection of target analytes which leads to accurate diagnosis of diseases or identification of drugs.

CRISPR/Cas12a antifouling nanocomposite electrochemical biosensors enable amplification-free detection of Monkeypox virus in complex biological fluids.

The escalating global threat of infectious diseases, including monkeypox virus (MPXV), necessitates advancements in point-of-care diagnostics, moving beyond the constraints of conventional methods tethered to centralized laboratories. Here, we introduce multiple CRISPR RNA (crRNA)-based biosensors that can directly detect MPXV within 35 minutes without pre-amplification, leveraging the enhanced sensitivity and antifouling attributes of the BSA-based nanocomposite. Multiple crRNAs, strategically targeting diverse regions of the F3L gene of MPXV, are designed and combined to amplify Cas12a activation and its collateral cleavage of reporter probes. Notably, our electrochemical sensors exhibit the detection limit of 669 fM F3L gene without amplification, which is approximately a 15-fold improvement compared to fluorescence detection. This sensor also shows negligible changes in peak current after exposure to complex biological fluids, such as whole blood and serum, maintaining its sensitivity at 682 fM. This sensitivity is nearly identical to the conditions when only the F3L gene was present in PBS. In summary, our CRISPR-based electrochemical biosensors can be utilized as a high-performance diagnostic tool in resource-limited settings, representing a transformative leap forward in point-of-care testing. Beyond infectious diseases, the implications of this technology extend to various molecular diagnostics, establishing itself as a rapid, accurate, and versatile platform for detection of target analytes.

Molecularly imprinted polymer-based electrochemical sensors for monitoring the persistent organic pollutants chlorophenols.

Because of the serious risks they pose to the environment and public health, chlorophenols (CPs), a typical class of the most persistent organic pollutants, have drawn increasing attention. Monitoring CPs effectively has become a pressing and difficult problem. The rapidly increasing need for onsite and real-time CP detection has led to the consideration of electrochemical sensing as a workable solution. Molecularly imprinted polymer (MIP)-based electrochemical sensing has emerged as a promising area for environmental monitoring in response to this analytical problem. MIPs, in conjunction with miniature electrochemical transducers, provide the opportunity to detect target analytes in situ. These devices have the advantages of great chemical and physical stability, cheap production costs, good selectivity, and quick response times. Most studies suggest that these sensors use nanoparticles to improve their analytical properties, especially sensitivity. Furthermore, these sensors have successfully used real water samples without the need for time-consuming pretreatment procedures. This article provides an overview of electrochemical MIP-based sensors reported to detect CPs in water samples. To obtain the highest sensitivity, special consideration is given to the fabrication of the sensors, which includes the use of various functional monomers, sensing platforms, and materials. Several other parameters are also discussed, including the linear concentration range, limit of detection, and the types of water samples that were examined.

Nanopore surface engineering of molecular imprinted mesoporous organosilica for rapid and selective detection of L-thyroxine

To develop a biosensing platform for precise diagnosis and management of thyroid-related diseases, the sensitive and selective recognition and identification of L-thyroxine (T4), a thyroid hormone, remains challenging. We herein introduce T4-imprinted mesoporous organosilica (T4-IMO) for sensitive and specific detection of T4 via the sophisticated engineering of pore surfaces using additives with different polarities. The pore surface of T4-IMO emitting a stable fluorescence signal is simply modified by fixed additives. Additives embedded in the pore surface promote the rebinding response of T4 into the recognized cavities, subsequently sensitizing T4 detection. Notably, T4-IMO containing abundant fluorine elements on the pore surface shows a high affinity toward T4, remarkably boosting the rebinding capacity. In addition to good selectivity to T4, the “turn-off” fluorescent signal exhibits a linear relationship with the logarithm of T4 concentration in a range of 0–500nM with a detection limit of 0.47nM in synthetic urine samples. Our findings can establish an insightful strategy for the rational design of molecular-recognition-based sensor systems for the selective and sensitive detection of target analytes.

Multi-analyte fluorescence sensing based on a post-synthetically functionalized two-dimensional Zn-MOF nanosheets featuring excited-state proton transfer process

Covalent post-synthetic modification of metal–organic frameworks (MOFs) represents an underexplored but promising avenue for allowing the addition of specific fluorescent recognition elements to produce the novel MOF-based sensory materials with multiple-analyte detection capability. Here, an excited-state proton transfer (ESPT) active sensor 2D-Zn-NS-P was designed and constructed by covalent post-synthetic incorporation of the excited-state tautomeric 2-hydroxypyridine moiety into the ultrasonically exfoliated amino-tagged 2D Zn-MOF nanosheets (2D-Zn-NS). The water-mediated ESPT process facilitates the highly accessible active sites incorporated on the surface of 2D-Zn-NS-P to specifically respond to the presence of water in common organic solvents via fluorescence turn-on behavior, and accurate quantification of trace amount of water in acetonitrile, acetone and ethanol was established using the as-synthesized nanosheet sensor with the detection sensitivity (<0.01% v/v) superior to the conventional Karl Fischer titration. Upon exposure to Fe3+ or Cr2O72−, the intense blue emission of the aqueous colloidal dispersion of 2D-Zn-NS-P was selectively quenched even in the coexistence of common inorganic interferents. The prohibition of the water-mediated ESPT process and local emission, induced by the coordination of ESPT fluorophore with Fe3+ or by Cr2O72− competitively absorbs the excitation energy, was proposed to responsible for the fluorescence turn-off sensing of the respective analytes. The present study offers the attractive prospect to develop the ESPT-based fluorescent MOF nanosheets by covalent post-synthetic modification strategy as multi-functional sensors for detection of target analytes.

Easy-to-prepare graphene-based inkjet-printed electrodes for diclofenac electrochemical sensing

Inkjet-printed electrodes (IPEs) from flexible Kapton® as substrate and easy to prepare graphene oxide (GO)-based inks (K/GO) were prepared using a standard desktop printer. Subsequently, they were submitted to a post-processing thermal treatment (K/GO_TR400) and assessed as disposable working electrodes (WEs) for diclofenac (DCF) indirect electrochemical detection at pH 7.0 (close to physiological pH value). DCF monitoring is attracting much interest, due to its classification as contaminant of emerging concern in water sources. The performance of the printed active sensor material was compared to that of thermally reduced (at 400 °C) graphene oxide (TRGO-400, in a powder form), which has been successfully used as glassy carbon electrode (GCE) modifier for the detection of DCF. This electrode worked linearly within the concentration range between 5 and 25 μM with an LOD value of 2.25 μM. Moreover, the morphology and chemical composition of the obtained IPEs were characterized by means of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) and compared with GCE/TRGO-400. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) measurements using a miniaturized 3-electrode cell of the post-processed IPEs showed a promising electrochemical performance for DCF sensing. Thus, this study demonstrated the effective partial recovery of the valuable properties of graphene on the IPEs after the thermal treatment and the successful production of flexible and disposable electrodes for target analyte detection. Therefore, this is a promising alternative to conventional modified GCEs, as it offers a facile approach for the fabrication of cutting edge graphene-based electrodes and widens the available portfolio of electrochemical sensors towards detection of water contaminants of emerging concern.

M13 Bacteriophage-Assisted Recognition and Signal Spatiotemporal Separation Enabling Ultrasensitive Light Scattering Immunoassay.

The demand for the ultrasensitive and rapid quantitative analysis of trace target analytes has become increasingly urgent. However, the sensitivity of traditional immunoassay-based detection methods is limited due to the contradiction between molecular recognition and signal amplification caused by the size effect of nanoprobes. To address this dilemma, we describe versatile M13 phage-assisted immunorecognition and signal transduction spatiotemporal separation that enable ultrasensitive light-scattering immunoassay systems for the quantitative detection of low-abundance target analytes. The newly developed immunoassay strategy combines the M13 phage-assisted light scattering signal fluctuations of gold nanoparticles (AuNPs) with gold in situ growth (GISG) technology. Given the synergy of M13 phage-mediated leverage effect and GISG-amplified light scattering signal modulation, the practical detection capability of this strategy can achieve the ultrasensitive and rapid quantification of ochratoxin A and alpha-fetoprotein in real samples at the subfemtomolar level within 50 min, displaying about 4 orders of magnitude enhancement in sensitivity compared with traditional phage-based ELISA. To further improve the sensitivity of our immunoassay, the biotin-streptavidin amplification scheme is implemented to detect severe acute respiratory syndrome coronavirus 2 spike protein down to the attomolar range. Overall, this study offers a direction for ultrasensitive quantitative detection of target analytes by the synergistic combination of M13 phage-mediated leverage effect and GISG-amplified light scattering signal modulation.

Synthesis of rare-earth metal-organic frameworks to construct high-resolution sensing array for multiplex anions detection, cell imaging and blood phosphorus monitoring

Accurate detection and differentiation of multiple anions is still a difficult problem due to their wide variety, structural similarity, and mutual interference. Hence, four rare-earth metal-organic frameworks (RE-MOFs) including Dy-MOFs, Er-MOFs, Tb-MOFs and Y-MOFs are successfully prepared by using TCPP as the ligand and rare-earth ions as the metal center via coordination chelation. It is found that 7 anions can light up their fluorescence. Thus, a high-resolution sensing array based on RE-MOFs nanoprobes is employed to differentiate these anions from intricate analytes in real-time scenarios. The distinctive host-guest response promotes the RE-MOFs nanoprobes to selectively extract the target anions from the complex samples. By taking advantage of the cross-response between RE-MOFs nanoprobes and anions, it allows to create an array for detecting target analytes using pattern recognition. Additionally, RE-MOFs nanoprobes also facilitate the quantitative analysis of these anions (PO43−, H2PO4−, HPO42−, F−, S2−, CO32– and C2O42−). More importantly, the exceptional effectiveness of this method has been demonstrated through various successful applications, including quality monitoring of 8 toothpaste brands, intracellular phosphate imaging, and blood phosphorus detection in mice with vascular calcification. These findings provide robust evidence for the efficacy and reliability of the RE-MOFs nanoprobes array for anion recognition.

Achieving smartphone-based colorimetric assay for Hg2+ with a bimetallic site strategy based on Hg2+-triggered oxidase-like catalytic activity of NSC/Co6Ni3S8 nanocomposite

Modulation of the nanozyme's catalytic activity is crucial for its real applications in detecting target analytes. Herein, we fabricated the nanocomposite (NSC/Co6Ni3S8) of N, S co-doped carbon and Co6Ni3S8 by a facile sol-gel approach. Compared to NSC/Ni9S8, NSC/Co6Ni3S8 with bimetallic active sites displayed better enzyme-mimetic activity. This nanocomposite could catalyze O2 to form ·O2− and oxidize colorless 3, 3′, 5, 5′-tetramethylbenzidine (TMB) into blue oxTMB. The other two free radicals (h+ and ·OH) played minor roles during the catalytic reaction. Hg2+ could integrate with S2− to form HgS and the surface charges of O2 were transferred to Hg2+ to promote O2 adsorption. DFT theoretical calculations highlight that the main reasons for the enhancing effect of Hg2+ on color development results from electron transfer and increased adsorption energy of O2 molecules onto the surface of NSC/Co6Ni3S8. By employing the oxidase-like activity of NSC/Co6Ni3S8 and Hg2+-triggered promoting effect, a colorimetric sensing platform was established for Hg2+ assay with a linear range of 10–200 μg/L and detection limit of 3 μg/L. Through integration with a smartphone-based APP “Thing Identify” software, a visual colorimetric assay for Hg2+ was constructed with a detection limit of 5 μg/L. Compared to the data detected by the mercury vapor meter, the relative recoveries of 92.4–108.1% evidenced the higher accuracy of this smartphone-based visual detection. Overall, the NSC/Co6Ni3S8-based colorimetric assay is convenient, rapid, and visual, and can be applied for routine monitoring of Hg2+ in real-world waters under outdoor conditions.

CRISPR-Cas12a-mediated dual-enzyme cascade amplification for sensitive colorimetric detection of HPV-16 target and ATP

The establishment of sensitive and facile colorimetric platform based on the CRISPR (clustered regularly interspaced short palindromic repeats)-Cas (CRISPR-associated) system is of great significance for in vitro diagnosis. Herein, we develop a dual-enzyme cascade amplification strategy based on CRISPR-Cas12a and glucose oxidase (GOx) for instrument-free and sensitive detection of target analytes. HPV-16 DNA as the model nucleic acid target directly initiated CRISPR-Cas12a-based signal transduction, resulting in the enzymatic cleavage of ssDNA linker and the release of GOx from magnetic nanoparticles 1 (MNPs1). Following simple magnetic separation, the supernatant containing GOx was taken out and used to catalyze the substrate, resulting in a visually detectable color change. The detection limit (LOD) of HPV-16 DNA was as low as 1 pM, and the entire process could be completed within 70 min without the need for expensive equipment. Notably, the dual-enzyme cascade amplification strategy was successfully applied to the detection of non-nucleic acid targets, such as ATP, via a simple signal transduction process. The visual LOD for ATP detection reaches 2.5 μM. The approach provides a robust, sensitive and reliable point-of-care biosensing platform for the detection of target analytes.

A fast multi-residue analysis of twenty-four classes of pesticide in sesame (Sesamum indicum L.) and their migration into processed products

Sesame is widely used as a nutritional supplement or condiment because of its nutritious properties and palatable flavor. However, the extensive use of pesticides in sesame fields has paradoxically decreased the nutritional vantage. The current study used QuEChERS with a low-temperature freezing method to develop a multi-residue analytical approach to detect target analytes (pesticides) in sesame seed, sesame oil, sesame paste, and sesame meal. The migration ability of target pesticides during oil processing was investigated using HPLC-MS/MS and GC-MS: 35% of pesticides decreased, with processing factors (PFs) lower than 0.98, whereas 65% migrated from the seed to the oil during processing. The migration success of methoxyfenozide was the highest, while clothianidin and pymetrozine demonstrated a significantly lower rate of transfer. The results provide insight into the types of pesticides that should be used in farming practices of sesame to decrease the impact on human health.

Smart Multiplex Point-of-Care Platform for Simultaneous Drug Monitoring.

Recently, illicit drug use has become more widespread and is linked to problems with crime and public health. These drugs disrupt consciousness, affecting perceptions and feelings. Combining stimulants and depressants to suppress the effect of drugs has become the most common reason for drug overdose deaths. On-site platforms for illicit-drug detection have gained an important role in dealing, without any excess equipment, long process, and training, with drug abuse and drug trafficking. Consequently, the development of rapid, sensitive, noninvasive, and reliable multiplex drug-detecting platforms has become a major necessity. In this study, a multiplex laser-scribed graphene (LSG) sensing platform with one counter, one reference, and three working electrodes was developed for rapid and sensitive electrochemical detection of amphetamine (AMP), cocaine (COC), and benzodiazepine (BZD) simultaneously in saliva samples. The multidetection sensing system was combined with a custom-made potentiostat to achieve a complete point-of-care (POC) platform. Smartphone integration was achieved by a customized application to operate, display, and send data. To the best of our knowledge, this is the first multiplex LSG-based electrochemical platform designed for illicit-drug detection with a custom-made potentiostat device to build a complete POC platform. Each working electrode was optimized with standard solutions of AMP, COC, and BZD in the concentration range of 1.0 pg/mL-500 ng/mL. The detection limit of each illicit drug was calculated as 4.3 ng/mL for AMP, 9.7 ng/mL for BZD, and 9.0 ng/mL for COC. Healthy and MET (methamphetamine) patient saliva samples were used for the clinical study. The multiplex LSG sensor was able to detect target analytes in real saliva samples successfully. This multiplex detection device serves the role of a practical and affordable alternative to conventional drug-detection methods by combining multiple drug detections in one portable platform.

Wearable microneedle-based colorimetric and fluorescence sensing for transdermal diagnostics

Interstitial fluid is a readily accessible source of biomarkers for various diseases, providing a less invasive and more convenient option than traditional blood or tissue sampling methods. Microneedle-based point-of-care testing devices have gained significant interest due to their potential for direct detection of target analytes in ISF, accomplished through minimally invasive penetration of the stratum corneum. Thus, microneedle-based devices can be considered as adhesive tools for diagnostic sensing and therapeutic drug administration. Microneedle-based colorimetric and fluorescence sensing has the potential to revolutionize disease diagnosis and monitoring, offering a rapid, highly sensitive, specific, and cost-effective alternative to traditional methods. These devices enable the detection of low levels of biomarkers in the collected fluid, which is particularly important in situations requiring prompt diagnosis and treatment. This review covers the types of microneedles and their fabrication methods, the detection principles of microneedle-based colorimetric and fluorescence sensing, as well as their key applications, advantages, and limitations. Additionally, the review explores ways to overcome current limitations and improve the performance, as well as future perspectives for the development of microneedle-based devices.

Rhodamine derivative–functionalized mesoporous silica–Al3+ hybrid material for fluorescence “turn–on” detection of tetracycline antibiotics in aqueous media

The organic–inorganic hybrid material was prepared by embedding 2-amino-3′,6′-bis(diethylamino)spiro[isoindoline-1,9′-xanthen]-3-one (RBH) onto mesoporous SBA–15 silica and coordinating it with Al3+ (RBH–SBA–15–Al3+). RBH–SBA–15–Al3+ was used for the selective and sensitive detection of tetracycline antibiotics (TAs) in aqueous media based on the binding site–signaling unit mechanism, in which Al3+ acted as the binding site and the fluorescence intensity at 586 nm as the response signal. The addition of TAs to RBH–SBA–15–Al3+ suspensions resulted in the formation of RBH–SBA–15–Al3+–TAs conjugates, which realized the electron transfer process and turned-on fluorescence signal at 586 nm. The detection limits for tetracycline (TC), oxytetracycline, and chlortetracycline were 0.06, 0.06, and 0.03 µM, respectively. Meanwhile, the detection of TC was feasible in real samples, such as tap water and honey. In addition, RBH–SBA–15 can operate as a TRANSFER logic gate by using Al3+ and TAs as input signals and the fluorescence intensity at 586 nm as output signal. This study proposes an efficient strategy for the selective detection of target analytes by introducing interaction sites (e.g. Al3+) with target analytes in the system.

Fundamentals of bio-electrochemical sensing

The utilization of bio-functionalities such as biorecognition or catalysis derived them their name biosensors. Bio-electrochemical sensing is a new discipline that combines the advantages of biological detection and electrochemical transduction. Bio-electrochemical sensors are devices that use biological materials such as enzymes, antibodies, DNA, or cells as receptors to detect target analytes in a variety of samples. Electrodes convert biological interactions into electrical impulses, which can be studied using various electrochemical techniques. Bio-electrochemical sensors have demonstrated significant promise for use in clinical diagnostics, environmental monitoring, food safety, and biotechnology. Biosensors have received numerous applications in recent years because they are fast, simple, and inexpensive for practical applications. In this article, we cover the basic principles, design strategies, immobilization and regeneration techniques, along with the advantages and applications of bio-electrochemical sensors. Finally, this article discusses the rationale for developing electrochemical biosensors in the context of the various bio-receptors that can be applied.