Dual-Modal Biosensor for Staphylococcus aureus Detection Based on a Porphyrin-Based Porous Organic Polymer FePor-TPA with Excellent Peroxidase-like, Catalase-like, and Photoelectrochemical Properties

Dual-mode sensor innovation based on light-harvesting and nanozyme integrated Cu-MOF loaded Cu2O label

Integrating photoelectrochemical (PEC) and colorimetric dual-mode shed light on "all-in-one" sensing platform for high sensitivity, in situ visualization and self-validating measurement. Its attainment depends on the capabilities of light harvesting and colorimetric signal generation from bi-functional tags, which remains challenging. Herein, Cu-MOF loaded Cu2O (Cu2O@Cu-MOF) was deliberately prepared and employed as the PEC- colorimetric signal reporter with tail-made stable photo-current and peroxidase mimic activity. A thin layer of Zr-MOF was deliberately encapsulated onto Cu2O@Cu-MOF for the immobilization of aptamer (Apt) which can be captured by the magnetic AuNPs/Fe3O4 nanoparticles through duplex-specific hybrid. In the presence of target analyte, PEC- colorimetric signal reporter was quantitatively released from the magnetic AuNPs/Fe3O4 after one-step convenient magnetic separation, facilitating photocurrent response by the photo-induced excitation and colorimetric response by catalyzing the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). In a proof-of-concept experiment, a customized PEC- colorimetric dual-mode sensor platform based on Cu2O@Cu-MOF reporter has achieved an ultrasensitive response for bisphenol A (BPA), exhibiting sub-picomole (PEC signal) and sub-nanomole (colorimetric signal) detection limits, respectively. Our dual-mode sensor platform strategy aims to extend to high-sensitivity and visual analysis in fields of in vitro diagnosis, environmental monitoring, and food safety.

Starch-KI test strip and solution colorimetry for dual-mode point-of-care testing (POCT) of live Staphylococcus aureus based on the activity of lysed catalase

Staphylococcus aureus (S. aureus), a ubiquitous foodborne pathogenic bacterium, is prevalent in a wide array of food products and frequently implicated in food poisoning incidents, necessitating effective means for its real-time monitoring and rapid detection. In response to this need, this study introduces an innovative dual-mode point-of-care testing (POCT) approach for detecting live S. aureus, leveraging the catalase (CAT)-induced H2O2-mediated reaction. This method integrates a starch-KI paper test with solution colorimetry, offering a dual-modal detection system. The use of commercial starch-KI test strips stands out for its simplicity, cost-effectiveness, rapidness, and enhanced stability and repeatability in large-scale applications, as it requires no modifications or treatments. Furthermore, combining with the solution colorimetry, the dual signal outputs enable mutual correction, significantly boosting detection accuracy and minimizing both false positives and negatives. The starch-KI test strips provide swift visual results, allowing for immediate identification, while the enzyme cascade-based solution colorimetry offers quantitative analysis with impressive lower limits of detection (72 CFU mL-1 for solution colorimetry). These low detection thresholds demonstrate the system's high sensitivity and precision. This dual-modal platform enables real-time monitoring and early intervention in food systems, preventing food poisoning. Its practicality, low cost, and user-friendliness make it an appealing diagnostic tool for both industrial food processors and public health authorities, particularly in regions with limited resources. By addressing the critical need for accurate, rapid, and cost-effective S. aureus detection, this dual-modal platform could significantly contribute to enhancing food safety globally.

pH-Adaptable CuO2 photo-responsive oxidase with phage-lysed β-galactosidase based cascade reaction for colorimetric detection of Escherichia coli in drinking water with high specificity and sensitivity

Escherichia coli (E. coli) is a primary cause of various waterborne diseases. However, detecting E. coli faces challenges in terms of speed, cost, sensitivity, and selectivity, especially in resource-limited regions. In this study, a smartphone-assisted CuO2 and β-galactosidase (β-gal)-mediated cascade colorimetric method for E. coli detection was developed. A pH-adaptable CuO2 acting as a photo-responsive oxidase was synthesized simply and combined with β-gal released from E. coli lysed by bacteriophages, enabling an enzyme-nanozyme cascade reaction. In this reaction, β-gal catalyzes the conversion of p-aminophenyl β-D-galactopyranoside (PAPG) to p-aminophenol (PAP), which subsequently inhibits the photo-responsive oxidase activity of CuO2. The photo-responsive oxidase CuO2, with its unique mechanism to generate holes for 3,3',5,5'-Tetramethylbenzidine (TMB) oxidation, overcomes the typical pH dependency of nanozymes, maintaining the optimal activity of both CuO2 oxidase and β-gal, enhancing sensitivity in the enzyme cascades. Bacteriophages, serving as specific bacterial identifiers, selectively recognize E. coli and promote the β-gal rapid release, further enhancing the detection sensitivity. This method achieves a detection limit of 15 CFU mL-1, accurately measured E. coli concentrations as low as 102 CFU mL-1, exhibited excellent recovery rates, ranging from 95.0 % to 104.1 %, with RSD between 1.3 % and 2.8 %, distinguishes the live and dead E. coli, reducing false positive and negative. Moreover, coupled with a smartphone, the sensor provides swift and accessible colorimetric data analysis, making it ideal for resource-constrained areas. In summary, this method is specific, sensitive, rapid, and cost-effective, requiring no pretreatment and offering broad potentials for bacterial detection in resource-limited areas.

In Situ Cascade Catalytic Polymerization of Dopamine Based on Pt NPs/CoSAs@NC Nanoenzyme for Constructing Highly Sensitive Photocurrent-Polarity-Switching PEC Biosensing Platform

Nanozymes open up new avenues for amplifying signals in photoelectrochemical (PEC) biosensing, which are yet limited by the generated small-molecule signal reporters. Herein, a multifunctional nanoenzyme of Pt NPs/CoSAs@NC consisting of Co single atoms on N-doped porous carbon decorated with Pt nanoparticles is successfully synthesized for cascade catalytic polymerization of dopamine for constructing a highly sensitive photocurrent-polarity-switching PEC biosensing platform. Taking protein tyrosine phosphatase 1B (PTP1B) as a target model, Pt NPs/CoSAs@NC nanoenzymes are linked to magnetic microspheres via phosphorylated peptides. Upon dephosphorylation of PTP1B, Pt NPs/CoSAs@NC nanoenzymes with multiple enzyme-like activities, including peroxidase (POD)-like, catalase (CAT)-like, and oxidase (OXD)-like activities, are released and collected to induce the in situ cascade catalytic polymerization of dopamine on ZnCdS photoelectrode in the presence of H2O2. The generated polymer-molecule of polydopamine served as efficient signal reporter for simultaneously amplifying signal and switching photocurrent polarity, which not only improved the sensitivity but also enhanced the reliability. This biosensing platform is capable of sensitively quantifying PTP1B with ultralow detection limit (0.04 fM), wide linear range (0.1 fm-0.1 µm), and good applicability in complex biological samples. This work pioneers the utilization of nanozyme-based cascade catalytic polymerization strategy for improving sensitivity and reliability in biosensing technologies.

Portable Self-Powered/Colorimetric Dual-Mode Sensing Platform Based on Multifunctional Bioconjugates for Precise On-Site Detection of Acetamiprid

Neonicotinoid insecticides have been widely applied in modern agriculture to improve crop productivity, but their residues have adverse impacts on the environment and human health. Hence, to address these issues, a portable self-powered/colorimetric dual-mode sensing platform was developed for the simple, rapid, precise, and sensitive on-site detection of acetamiprid (ATM) residues in vegetables. In this case, a multifunctional bioconjugate with specific recognition capability, excellent enzyme-like activity, and loading capacity is the key to the sensing design. Using an Eppendorf (EP) tube as a miniaturized laboratory, the bioconjugates and the colorimetric test strip were integrated into the EP tube, and combined with a nanozyme-based self-powered sensing platform (with an area of 1.5 × 1.5 cm2), accurate on-site detection of ATM was achieved, with detection limits as low as 2.9 fg·mL-1 (self-powered method) and 31.5 fg·mL-1 (colorimetry), respectively. Notably, we simulated the actual insecticidal situation based on the field application concentration and quantified the pesticide residues in vegetables. The relative errors of our method and the standard high-performance liquid chromatography method were 0.15% (the self-powered method) and 1.8% (colorimetry), respectively. The portable dual-mode sensing platform with high sensitivity and accuracy opened up a new avenue for the development of on-site pesticide residue analysis in the next generation of agricultural products.

Ultrafast enzyme-responsive hydrogel for real-time assessment and treatment optimization in infected wounds

Monitoring wound infection and providing appropriate treatment are crucial for achieving favorable outcomes. However, the time-consuming nature of laboratory culture tests may delay timely intervention. To tackle this challenge, a simple yet effective HDG hydrogel, composed of hydrogen peroxide (H₂O₂), dopamine, and GelMA polymer, is developed for the ultrafast detection and treatment of Staphylococcus aureus (SA) infections. The HDG hydrogel detects SA by exploiting its secreted catalase to catalyze H₂O₂, producing oxygen, which in turn accelerates the polymerization of colorless dopamine into deep brown polydopamine (PDA). The bacterial detection process takes only 10 min with high sensitivity, and the results can be readily recognized by the naked eye or quantified using a cell phone-based digital analysis. Moreover, the HDG hydrogel provides a dual antibacterial mechanism through chemical and photothermal therapies via the generated PDA, significantly improving bacterial clearance. In animal experiments, the HDG hydrogel demonstrated promising capabilities in monitoring and eliminating bacteria, enhancing collagen deposition, reducing inflammation, and promoting the healing of infected wounds. This multifunctional design offers an enzyme-responsive strategy for the rapid assessment and management of infections, simplifying infection evaluation and facilitating the development of advanced wound dressings.

Dual-modal biosensor for mercuric ion detection based on Cu2O@Cu2S/D-TA COF heterojunction with excellent catalase-like, electrochemical and photoelectrochemical properties

In this study, a dual-mode biosensor based on the heterojunction of Cu2O@Cu2S/D-TA COF was constructed for ultra-sensitive detection of Hg2+ using both photoelectrochemical and electrochemical approaches. Briefly, a 2D ultra-thin covalent organic framework film (D-TA COF film) with excellent photoelectrochemical signals was prepared on ITO surfaces through an in situ growth method. Subsequently, the probe H1 was immobilized onto the biosensor via Au-S bonds. In the presence of Hg2+, the formation of T-Hg2+-T complexes triggered hybridization chain reactions (HCR), leading to the attachment of abundant Cu2O@Cu2S probes onto the biosensor. As a p-type semiconductor, Cu2O@Cu2S could form a heterojunction with the underlying D-TA COF films. Meanwhile, it exhibited catalase-like activity, and the O2 produced by its catalytic decomposition of H2O2 can interact with the D-TA COF films, thus achieving double amplification of the photocurrent signal. Benefiting from the excellent and inherent Cu2+/Cu+ redox pairs of Cu2O@Cu2S, satisfactory differential pulse voltammetry (DPV) signals were obtained. As expected, the dual-mode biosensor was realized with wider linear ranges and low detection limits. Additionally, the analytical performance for Hg2+ in real water samples was excellent. Briefly, this suggested approach offers a facile and highly efficient modality for monitoring heavy metal ions in aquatic environments.

Photoelectrochemical/Colorimetric Dual-Mode Specific Detection of Staphylococcus aureus Based on the Enzymatic Reaction Triggered by Catalase from Lysed Bacteria

Staphylococcus aureus (S. aureus) is abundant in nature and frequently leads to various health issues. Bacteriophages as obligate intracellular parasites of bacteria have the ability to specifically identify and infect S. aureus, causing bacterial lysis and the release of endogenous catalase (CAT). The released CAT triggers the conversion of H2O2 into O2 and H2O, resulting in a notable decrease in UV absorption at 570 nm and a concurrent surge in photocurrent. On the basis of this, a photoelectrochemical/colorimetric dual-mode biosensor for the detection of S. aureus was developed. In the photoelectric detection mode, the reactions involving endogenous enzymes occur directly in the solution, requiring only the simple drop-coating of TiO2@CdS onto the indium tin oxide (ITO) electrode surface. There was no need for immobilizing additional biomolecules, thereby significantly minimizing nonspecific adsorption and improving the biosensor's stability and reproducibility. For colorimetry, we utilized a cost-effective and operationally simple approach based on KI and starch. Remarkably, this photoelectrochemical/colorimetry exhibited a linear range of 102-109 CFU/mL for S. aureus, achieving detection limits of 7 and 10 CFU/mL, respectively. Herein, phage identification ensures the specific detection of live S. aureus, thereby effectively mitigating the potential for false signals. The dual-signal readout mode improves the detection accuracy and reliability. In conclusion, this present method offers numerous advantages, including simplicity, time-efficiency, cost-effectiveness, high specificity, and therefore excellent accuracy.

Tunable Structured 2D Nanobiocatalysts: Synthesis, Catalytic Properties and New Horizons in Biomedical Applications

2D materials have offered essential contributions to boosting biocatalytic efficiency in diverse biomedical applications due to the intrinsic enzyme-mimetic activity and massive specific surface area for loading metal catalytic centers. Since the difficulty of high-quality synthesis, the varied structure, and the tough choice of efficient surface loading sites with catalytic properties, the artificial building of 2D nanobiocatalysts still faces great challenges. Here, in this review, a timely and comprehensive summarization of the latest progress and future trends in the design and biotherapeutic applications of 2D nanobiocatalysts is provided, which is essential for their development. First, an overview of the synthesis-structure-fundamentals and structure-property relationships of 2D nanobiocatalysts, both metal-free and metal-based is provided. After that, the effective design of the active sites of nanobiocatalysts is discussed. Then, the progress of their applied research in recent years, including biomedical analysis, biomedical therapeutics, pharmacokinetics, and toxicology is systematically highlighted. Finally, future research directions of 2D nanobiocatalysts are prospected. Overall, this review to provide cutting-edge and multidisciplinary guidance for accelerating future developments and biomedical applications of 2D nanobiocatalysts is expected.

A Piezoelectric Nanogenerator-Driven Dual-Mode Platform for Visualization and Impedance Sensing

Traditional visual biosensing platforms rely on color to display detection results, which can be influenced by individual visual abilities, equipment, parameters, and lighting conditions during photo capture. This limitation significantly impedes the advancement of next-generation portable electrochemical biosensors. Therefore, we propose a visual biosensing device that utilizes distance as an indicator, enabling the facile determination of the length of discoloration, which is inversely proportional to the concentration of the target analyte. The separation of the Signal Generation (SG) and Signal Output (SO) regions effectively mitigates potential interference from the sample color. Additionally, the SG region can be disassembled to facilitate electrochemical impedance spectroscopy (EIS) detection in laboratory settings, enabling dual-mode detection. Meanwhile, the utilization of piezoelectric nanogenerators (PENG) empowers the entire point-of-care testing (POCT) sensing device, effectively addressing the issue of a limited battery life. The biosensing device exhibited a satisfactory linear range (EIS mode, 5 pg/L to 5 mg/L; visual mode, 0.5 ng/L to 5 mg/L) and a low limit of detection (EIS mode, 2.3 pg/L; visual mode, 0.14 ng/L) with S/N = 3 for ochratoxin A (OTA) under optimized conditions. The self-powered and cost-effective dual-mode biosensing platform developed for OTA detection offers clear and easily interpretable results, demonstrating a high accuracy in laboratory settings.

Porous organic polymers assisted aptamer signal amplification for enhanced photoeletrochemical detection of MUC1

Mucin1 (MUC1) is an extensively glycosylated transmembrane protein that is widely distributed and overexpressed on the surface of cancer cells, playing an important role in tumor occurrence and metastasis. Therefore, highly sensitive detection of MUC1 is of great significance for early diagnosis, treatment monitoring, and prognosis of cancer. Here, an ultra-sensitive photoelectrochemical (PEC) sensing platform was developed based on an aptamer amplification strategy for highly selective and sensitive detection of MUC1 overexpressed in serum and on cancer cell surfaces. The sensing platform utilized copper phthalocyanine to fabricate porous organic polymers (CuPc POPs), and was effectively integrated with g-C3N4/MXene to form a ternary heterojunction material (g-C3N4/MXene/CuPc POPs). This material effectively improved electron transfer capability, significantly enhanced light utilization, and greatly enhanced photoelectric conversion efficiency, resulting in a dramatic increase in photocurrent response. MUC1 aptamer 1 was immobilized on a chitosan-modified photoelectrode for the selective capture of MUC1 or MCF-7 cancer cells. When the target substance was present, MUC1 aptamer 2 labeled with methylene blue (MB) was specifically adsorbed on the electrode surface, leading to enhanced photocurrent. The concentration of MUC1 directly correlated with the number of MB molecules attracted to the electrode surface, establishing a linear relationship between photocurrent intensity and MUC1 concentration. The PEC biosensor exhibited excellent sensitivity for MUC1 detection with a wide detection range from 1 × 10-7 to 10 ng/mL and a detection limit of 8.1 ag/mL. The detection range for MCF-7 cells was from 2 × 101 to 2 × 106 cells/mL, with the capability for detecting single MCF-7 cells. The aptamer amplification strategy significantly enhanced PEC performance, and open up a promising platform to establish high selectivity, stability, and ultrasensitive analytical techniques.

Multimodal Biosensing of Foodborne Pathogens

Microbial foodborne pathogens present significant challenges to public health and the food industry, requiring rapid and accurate detection methods to prevent infections and ensure food safety. Conventional single biosensing techniques often exhibit limitations in terms of sensitivity, specificity, and rapidity. In response, there has been a growing interest in multimodal biosensing approaches that combine multiple sensing techniques to enhance the efficacy, accuracy, and precision in detecting these pathogens. This review investigates the current state of multimodal biosensing technologies and their potential applications within the food industry. Various multimodal biosensing platforms, such as opto-electrochemical, optical nanomaterial, multiple nanomaterial-based systems, hybrid biosensing microfluidics, and microfabrication techniques are discussed. The review provides an in-depth analysis of the advantages, challenges, and future prospects of multimodal biosensing for foodborne pathogens, emphasizing its transformative potential for food safety and public health. This comprehensive analysis aims to contribute to the development of innovative strategies for combating foodborne infections and ensuring the reliability of the global food supply chain.

Porphyrin-based covalent organic frameworks from design, synthesis to biological applications

Covalent organic frameworks (COFs) constitute a class of highly functional porous materials composed of lightweight elements interconnected by covalent bonds, characterized by structural order, high crystallinity, and large specific surface area. The integration of naturally occurring porphyrin molecules, renowned for their inherent rigidity and conjugate planarity, as building blocks in COFs has garnered significant attention. This strategic incorporation addresses the limitations associated with free-standing porphyrins, resulting in the creation of well-organized porous crystal structures with molecular-level directional arrangements. The unique optical, electrical, and biochemical properties inherent to porphyrin molecules endow these COFs with diversified applications, particularly in the realm of biology. This review comprehensively explores the synthesis and modulation strategies employed in the development of porphyrin-based COFs and delves into their multifaceted applications in biological contexts. A chronological depiction of the evolution from design to application is presented, accompanied by an analysis of the existing challenges. Furthermore, this review offers directional guidance for the structural design of porphyrin-based COFs and underscores their promising prospects in the field of biology.

Surface Bio-engineered Polymeric Nanoparticles

Surface bio-engineering of polymeric nanoparticles (PNPs) has emerged as a cornerstone in contemporary biomedical research, presenting a transformative avenue that can revolutionize diagnostics, therapies, and drug delivery systems. The approach involves integrating bioactive elements on the surfaces of PNPs, aiming to provide them with functionalities to enable precise, targeted, and favorable interactions with biological components within cellular environments. However, the full potential of surface bio-engineered PNPs in biomedicine is hampered by obstacles, including precise control over surface modifications, stability in biological environments, and lasting targeted interactions with cells or tissues. Concerns like scalability, reproducibility, and long-term safety also impede translation to clinical practice. In this review, these challenges in the context of recent breakthroughs in developing surface-biofunctionalized PNPs for various applications, from biosensing and bioimaging to targeted delivery of therapeutics are discussed. Particular attention is given to bonding mechanisms that underlie the attachment of bioactive moieties to PNP surfaces. The stability and efficacy of surface-bioengineered PNPs are critically reviewed in disease detection, diagnostics, and treatment, both in vitro and in vivo settings. Insights into existing challenges and limitations impeding progress are provided, and a forward-looking discussion on the field's future is presented. The paper concludes with recommendations to accelerate the clinical translation of surface bio-engineered PNPs.

Multi-modal nanoprobe-enabled biosensing platforms: a critical review

Nanomaterials show great potential for applications in biosensing due to their unique physical, chemical, and biological properties. However, the single-modal signal sensing mechanism greatly limits the development of single-modal nanoprobes and their related sensors. Multi-modal nanoprobes can realize the output of fluorescence, colorimetric, electrochemical, and magnetic signals through composite nanomaterials, which can effectively compensate for the defects of single-modal nanoprobes. Following the multi-modal nanoprobes, multi-modal biosensors break through the performance limitation of the current single-modal signal and realize multi-modal signal reading. Herein, the current status and classification of multi-modal nanoprobes are provided. Moreover, the multi-modal signal sensing mechanisms and the working principle of multi-modal biosensing platforms are discussed in detail. We also focus on the applications in pharmaceutical detection, food and environmental fields. Finally, we highlight this field's challenges and development prospects to create potential enlightenment.