Rapid and quantitative detection of tear MMP-9 for dry eye patients using a novel silicon nanowire-based biosensor

Aminated fullerene for comprehensive dry eye therapy: Promoting epithelial-barrier reconstruction and nerve regeneration by suppressing oxidation and inflammation

Dry eye disease (DED) affects up to 50 % of the global population, leading to serious discomforts that affect patients' quality of life. In the multifactorial etiology of DED, oxidative stress is at the core, initiating a sequence of inflammatory responses and surface damage via a vicious cycle. However, current therapies merely have a narrow focus on inflammation. In this study, we developed a novel antioxidative eye drop, ethylenediamine (EDA)-modified C70 fullerene derivatives (abbreviated as FN-EDA), to break this vicious cycle. FN-EDA was successfully synthesized by modifying C70 fullerene with multiple ethylenediamine (EDA) groups, resulting in enhanced water solubility and a positive charge. This modification significantly improved ocular surface retention time, cellular uptake, and lysosomal escape in vitro. Therapeutically, FN-EDA significantly alleviated dry eye disease (DED) in a mouse model. It reduced corneal epithelial damage by 3.8-fold compared to 0.05 % cyclosporine A (CsA) and restored tear secretion to approximately 65 % of the normal level. Mechanistically, both in vivo and in vitro results demonstrate that FN-EDA is endowed with superior biological activity in effectively scavenging excessive oxidative stress, down-regulating proinflammatory cytokines expression, and promoting epithelial barrier reconstruction, even recovering corneal innervation. Thus, our findings open an avenue to make this multi-functional eye drop a promising candidate for DED.

Transformative biomedical devices to overcome biomatrix effects

The emergence of high-performance biomedical devices and sensing technologies highlights the technological advancements in the field. Recently during COVID-19 pandemic, biosensors played an important role in medical diagnostics and disease monitoring. In the past few decades, biosensors have made impressive advances in terms of sensing capability, methodology, and applications, and modern biosensors show higher performance and functionality compared to traditional biosensing platforms. Currently, various biomedical devices are already in the market or on the verge of commercialization, such as disposable paper-based devices, lab-on-a-chip devices, wearable sensors, and artificial intelligence-assisted systems, all contributing to the evolution of digital health. Despite the promising features of detection methods for developing practical biosensors, there are substantial barriers to the commercialization of biomedical devices. An important challenge is the matrix effect in the detection of clinical samples. Although achieving low limit of detection values under controlled laboratory conditions is feasible, maintaining performance in real clinical samples is difficult. Matrix molecules present in these samples can interact with analytes, potentially affecting sensitivity, specificity, and sensor response. Approaches to reduce nonspecific adsorption and cross-reactivity are imperative for improving sensor performance. The detection of diagnostic biomarkers in complex biological matrices often requires laborious sample preparation, which may affect accuracy and precision. In this review, we highlight the recent efforts to detect analytes in real samples, both invasively and noninvasively, and underline technological advancements that mitigate the biomatrix effects. We also discuss commercially available biosensors and technologies promising commercial success, highlighting their potential effect on healthcare and diagnostics.

Electrochemically Active Materials for Tissue-Interfaced Soft Biochemical Sensing

Tissue-interfaced soft biochemical sensing represents a crucial approach to personalized healthcare by employing electrochemically active materials to monitor biochemical signals at the tissue interface in real time, either noninvasively or through implantation. These soft biochemical sensors can be integrated with various biological tissues, such as neural, gastrointestinal, ocular, cardiac, skin, muscle, and bone, adapting to their unique mechanical and biochemical environments. Sensors employing materials like conductive polymers, composites, metals, metal oxides, and carbon-based nanomaterials have demonstrated capabilities in applications, such as continuous glucose monitoring, neural activity mapping, and real-time metabolite detection, enhancing diagnostics and treatment monitoring across a range of medical fields. Next-generation tissue-interfaced biosensors that enable multimodal and multiplexed measurement of biochemical markers and physiological parameters could be transformative for personalized medicine, allowing for high-resolution, time-resolved historical monitoring of an individual's health status. In this review, we summarize current trends in the field to provide insights into the challenges and future trajectory of tissue-interfaced soft biochemical sensors, highlighting their potential to revolutionize personalized medicine and improve patient outcomes.

Targeting α7 Nicotinic Acetylcholine Receptor for Modulating the Neuroinflammation of Dry Eye Disease Via Macrophages

Purpose

Patients with dry eye disease (DED) often exhibit neurological abnormalities and may even suffer from neuropathic pain and pain-related anxiety or depression. The α-7 nicotinic acetylcholine receptor (α7nAChR) is a pivotal regulator in the anti-inflammatory pathway connecting the nervous and immune systems, Here, we investigate the potential of α7nAChR agonist as a novel treatment for DED.

Methods

We induced DED model by unilateral excision of extraorbital lachrymal gland in C57/BL6 mice. After seven days of treatment, RNA sequencing was performed to identify differentially expressed genes in the cornea of lacrimal gland excision (LGE) mice. Quantitative polymerase chain reaction, Western blotting, and flow cytometry tests were carried out to elucidate neuroinflammation changes after α7nAChR activation. Corneal nerve abnormalities were assessed by corneal esthesiometry and immunofluorescence staining.

Results

The activation of α7nAChR stimulates genes involved in immune-mediated inflammatory progression and neuroregulation, inhibits the expression of transient receptor potential vanilloid-1, reinstates corneal nerve density, and alleviates anxiety-like behaviors associated with severe DED. Furthermore, we demonstrated that α7nAChR agonist restored corneal nerve abnormality and alleviated inflammation response by down-regulating the proportion of CD86+ M1 macrophages (proinflammatory phenotypes).

Conclusions

Our findings underscore the activation of α7nAChR as a pioneering therapeutic approach for preserving corneal nerves balance and controlling inflammation in DED.

Application of Nanomaterials in the Diagnosis and Treatment of Retinal Diseases

In recent years, nanomaterials have demonstrated broad prospects in the diagnosis and treatment of retinal diseases due to their unique physicochemical properties, such as small-size effects, high biocompatibility, and functional surfaces. Retinal diseases are often accompanied by complex pathological microenvironments, where conventional diagnostic and therapeutic approaches face challenges such as low drug delivery efficiency, risks associated with invasive procedures, and difficulties in real-time monitoring. Nanomaterials hold promise in addressing these limitations of traditional therapies, thereby improving treatment precision and efficacy. The applications of nanomaterials in diagnostics are summarized, where they enable high-resolution retinal imaging by carrying fluorescent probes or contrast agents or act as biosensors to sensitively detect disease-related biomarkers, facilitating early diagnosis and dynamic monitoring. In therapeutics, functionalized nanocarriers can precisely deliver drugs, genes, or antioxidant molecules to retinal target cells, significantly enhancing therapeutic outcomes while reducing systemic toxicity. Additionally, nanofiber materials possess unique properties that make them particularly suitable for retinal regeneration in tissue engineering. By loading neurotrophic factors into nanofiber scaffolds, their regenerative effects can be amplified, promoting the repair of retinal neurons. Despite their immense potential, clinical translation of nanomaterials still requires addressing challenges such as long-term biosafety, scalable manufacturing processes, and optimization of targeting efficiency.

Lab-in-a-Tip: a multiplex immunoassay platform based on a self-assembled barcoded protein array

High throughput immunoassay is increasingly crucial for both scientific and clinical applications. Here we propose a "Lab-in-a-Tip" (LIT) concept to fabricate a pipette tip containing a high-density protein array and other essential reagents. The protein array is made by self-assembling digitally encoded microparticles inside the modified tip. Mounted on a robotic workstation, it automates liquid-handling steps. Notably, compared with Luminex, the current gold standard in multiplex immunoassays, such a design enables LIT to demonstrate multiple advantages in terms of analytical sensitivity, speed, and throughput. It detects analyte concentrations as low as fg/ml, representing a sensitivity improvement of two orders of magnitude over Luminex. Incubation time is reduced to 15 minutes from Luminex's 210 minutes. Furthermore, LIT requires only 10 µl of sample, one-fifth of what Luminex needs. This makes LIT ideal for rapid diagnostics and studies with limited biological samples, greatly expanding its application scope.

A novel Schirmer strip-based tear matrix metalloproteinase measurement in dry eye evaluation

PURPOSE

The diagnosis and evaluation of dry eye require easy-to-use, precise, and consistent tools in clinical setting. Matrix metalloproteinase 9 (MMP-9) has been proven to be a reliable indicator of dry eye inflammation. The aim of this study is to establish an Eu-time resolved fluorescence immunochromatography (Eu-TRFICO) method for quantitative detection of MMP-9 in human tear based upon widely used Schirmer strips.

METHODS

The Eu-TRFICO method for Schirmer strip-based tear MMP-9 measurements were optimized and assembled. The sensitivity, repeatability and homogeneity were evaluated using MMP-9 standard dilutions. The diagnostic and treatment monitoring performance were evaluated in both dry eye patients and normal subjects.

RESULTS

The standard curve equation was y = 0.0037 + 8.0692/[1+ (x/188.322)-0.8972] (R2 = 0.99998), and the sensitivity was 0.25 ng/mL. The Schirmer strip-based MMP-9 measurements showed acceptable repeatability and homogeneity with different saturation length in both low and high standard solutions. A total of 162 participants (162 eyes) were enrolled in this study, including 41 normal and 121 dry eye subjects. This method exhibited a sensitivity of 74.17 % and specificity of 77.5 % for dry eye diagnosis, with an AUC value of 0.8275, and cutoff value of 150.67 ng/mL, using normal subjects as negative control. The tear MMP-9 concentrations monitored with this method correlated well with the therapeutic response in dry eye patients.

CONCLUSIONS

This study developed Eu-TRFICO Schirmer strips with high sensitivity, specificity, precision, and satisfactory clinical testing performance, which provides a convenient and quantitative option for clinical testing of tear MMP-9 in dry eye patients.

Protein Detection Based on Field-Effect Transistor Biosensors for Diagnosing Diseases

Proteins have been one of the most important biomarkers for diagnosing diseases, and field-effect transistor (FET) biosensors possess high sensitivity; are label-free; and feature real-time detection, rapidity, and easy integration for protein detection. FET biosensors are mainly made up of FET parts, such as channel materials, and bio parts, such as receptors. This Tutorial provides an in-depth exploration of FET biosensors for protein detection from the composition perspective and discusses the commercialization of point-of-care diagnostics of proteins based on FET biosensors.

Sliding Microneedle - Lateral flow immunoassay strip device for highly sensitive biomarker detection in interstitial fluid

Diabetes is a chronic disease with significant complications, necessitating regular treatment and checkups, which can be costly and time-consuming for patients. To address this, we developed the Sliding Microneedle (MN)-Lateral flow immunoassay strip (LFIAs) device that combines the advantages of MNs and LFIAs to detect IL-6, an independent biomarker for diabetes complications. This device offers rapid and highly sensitive detection of IL-6 by extracting interstitial fluid (ISF) through MNs and transferring it to LFIAs. The stainless MN, embedded in the 3D-printed Sliding MN-LFIAs device, was inserted into the skin at a 20° angle, minimizing blood contamination risk. With a filter paper attached to the MN surface, the device collected 4.65 ± 0.05 μL of ISF containing IL-6 within 90 s. The ISF was then transferred to the LFIAs using a running buffer. After a 15-min reaction, silver enhancement (SE) treatment was applied, allowing for the highly sensitive and specific detection of IL-6 at 102 pg/mL concentrations. The Sliding MN-LFIAs device successfully distinguished between normal and diabetic rat models, demonstrating its potential as an effective tool for detecting diabetes complications quickly and affordably.

Exosomal membrane proteins analysis using a silicon nanowire field effect transistor biosensor

Exosomes are of great significance in clinical diagnosis, due to their high homology with parental generation, which can reflect the pathophysiological status. However, the quantitative and classification detection of exosomes is still faced with the challenges of low sensitivity and complex operation. In this study, we develop an electrical and label-free method to directly detect exosomes with high sensitivity based on a Silicon nanowire field effect transistor biosensor (Si-NW Bio-FET). First, the impact of Debye length on Si-NW Bio-FET detection was investigated through simulation. The simulation results demonstrated that as the Debye length increased, the electrical response to Si-NW produced by charged particle at a certain distance from the surface of Si-NW was greater. A Si-NW Bio-FET modified with specific antibody CD81 on the nanowire was fabricated then used for detection of cell line-derived exosomes, which achieved a low limit of detection (LOD) of 1078 particles/mL in 0.01 × PBS. Furthermore, the Si-NW Bio-FETs modified with specific antibody CD9, CD81 and CD63 respectively, were employed to distinguish exosomes derived from human promyelocytic leukemia (HL-60) cell line in three different states (control group, lipopolysaccharide (LPS) inflammation group, and LPS + Romidepsin (FK228) drug treatment group), which was consistent with nano-flow cytometry. This study provides a highly sensitive method of directly quantifying exosomes without labeling, indicating its potential as a tool for disease surveillance and medication instruction.

Succinimide-Functionalized Reduced Graphene Oxide Nanosheets: A High-throughput Resistive Sensing Platform for Age-Related Macular Degeneration Biomarker Determination Using Human Tears

Age-related macular degeneration (AMD) is a well-recognized affliction among the elderly, causing vision impairment ranging from blurred vision to complete blindness. This underscores the critical need for accurate, precise, and early detection methods. Herein, we developed a noninvasive, label-free electrical biosensor, constructed on an economical printed circuit board (PCB) substrate, designed specifically for the precise quantification of AMD biomarker: complement component III (C3). The hydrothermally reduced graphene oxide (rGO) was deposited between gold-interdigitated microelectrodes, forming a conductive channel. The fabricated C3 biosensor exhibits a low detection limit of 0.4342 ng/mL and an impressive sensitivity of 9.238 ((ΔR/R)/ng.mL-1)/cm2 with a regression coefficient of 0.9815 calibrated within the clinical C3 range of 10-30 ng/mL. This excellent performance is ascribed to the synergistic effects of 1-pyrenebutanoic acid succinimidyl ester (PBASE) linker and conducting properties of rGO as they generate large active sites for higher anti-C3 antibody immobilization, thereby enhancing sensitivity and specificity. Furthermore, the performance of this proposed C3 sensor chip was validated with enzyme-linked immunosorbent assay (ELISA) using five human tear samples exhibiting an outstanding correlation of a regression value of 0.9774. The unparalleled merits of this newly crafted C3 biosensor transcend those of preceding platforms, boasting superior accuracy and precision in quantifying C3 levels in human tears, accelerated operational speed with results attainable within a mere 15 min, cost-effectiveness, and excellent sensitivity.

A Calibration Strategy for Silicon Nanowire Field-Effect Transistor Biosensors and Its Application in Ultra-Sensitive, Label-Free Biosensing

The silicon nanowire field-effect transistor (SiNW FET) has been developed for over two decades as an ultrasensitive, label-free biosensor for biodetection. However, inconsistencies in manufacturing and surface functionalization at the nanoscale have led to poor sensor-to-sensor consistency in performance. Despite extensive efforts to address this issue through process improvements and calibration methods, the outcomes have not been satisfactory. Herein, based on the strong correlation between the saturation response of SiNW FET biosensors and both their feature size and surface functionalization, we propose a calibration strategy that combines the sensing principles of SiNW FET with the Langmuir-Freundlich model. By normalizing the response of the SiNW FET biosensors (ΔI/I0) with their saturation response (ΔI/I0)max, this strategy fundamentally overcomes the issues mentioned above. It has enabled label-free detection of nucleic acids, proteins, and exosomes within 5 min, achieving detection limits as low as attomoles and demonstrating a significant reduction in the coefficient of variation. Notably, the nucleic acid test results exhibit a strong correlation with the ultraviolet-visible (UV-vis) spectrophotometer measurements, with a correlation coefficient reaching 0.933. The proposed saturation response calibration strategy exhibits good universality and practicability in biological detection applications, providing theoretical and experimental support for the transition of mass-manufactured nanosensors from theoretical research to practical application.

Aversatile MOF as an electrochemical/fluorescence/colorimetric signal probe for the tri-modal detection of MMP-9 secretion in the extracellular matrix to identify the efficacy of chemotherapeutic drugs

BACKGROUND

MMP-9 plays a crucial role in regulating the degradation of proteins within the extracellular matrix (ECM). This process closely correlates with the occurrence, development, invasion, and metastasis of various tumors, each exhibiting diverse levels of MMP-9 expression. However, the accuracy of detection results using the single-mode method is compromised due to the coexistence of multiple biologically active substances in the ECM.

RESULTS

Therefore, in this study, a tri-modal detection system is proposed to obtain more accurate information by cross-verifying the results. Herein, we developed a tri-modal assay using the ZIF-8@Au NPs@S QDs composite as a multifunctional signal probe, decorated with DNA for the specific capture of MMP9. Notably, the probe demonstrated high conductivity, fluorescence response and mimicked enzyme catalytic activity. The capture segments of hybrid DNA specifically bind to MMP9 in the presence of MMP9, causing the signal probe to effortlessly detach the sensor interface onto the sample solution. Consequently, the sensor current performance is weakened, with the colorimetric and fluorescent signals becoming stronger with increasing MMP9 concentration. Notably, the detection range of the tri-modal sensor platform spans over 10 orders of magnitude, verifying notable observations of MMP-9 secretion in four tumor cell lines with chemotherapeutic drugs. Furthermore, the reliability of the detection results can be enhanced by employing pairwise comparative analysis.

SIGNIFICANCE

This paper presents an effective strategy for detecting MMP9, which can be utilized for both the assessment of MMP-9 in cell lines and for analyzing the activity and mechanisms involved in various tumors.

Aurantio-obtusin Alleviates Dry Eye Disease by Targeting NF-κB/NLRP3 Signaling in Rodent Models

Dry eye disease (DED) is a common inflammatory ocular surface disorder, seriously affecting the quality of life of patients. Aurantio-obtusin (AO) is a bioactive anthraquinone compound isolated from Semen Cassiae which has multiple pharmacological activities. Nonetheless, the specific function of AO in DED is unclarified. In this study, a rodent DED model was established by benzalkonium chloride (BAC) induction, followed by topical administration of AO. The results showed that topical application of AO increased tear production, mitigated ocular surface disruption and maintained the number of goblet cells in BAC-induced DED rats (p˂0.05). ELISA revealed that AO treatment significantly (p˂0.001) reduced the production of proinflammatory cytokines and chemokines in the conjunctiva and cornea of BAC-induced DED rats. Immunohistochemical staining and western blotting showed that AO treatment suppressed the expression levels of NLR family pyrin domain containing 3 (NLRP3) inflammasome-related proteins, and inhibited activation of nuclear factor kappa B (NF-κB) signaling pathway in rat conjunctiva and cornea (p˂0.001). In conclusion, AO treatment alleviates BAC-induced DED in rats by inhibiting NF-κB/NLRP3 inflammasome signaling pathway.

Functionalized-Graphene Field Effect Transistor-Based Biosensor for Ultrasensitive and Label-Free Detection of β-Galactosidase Produced by Escherichia coli

The detection of β-galactosidase (β-gal) activity produced by Escherichia coli (E. coli) can quickly analyze the pollution degree of seawater bodies in bathing and fishing grounds to avoid large-scale outbreaks of water pollution. Here, a functionalized biosensor based on graphene-based field effect transistor (GFET) modified with heat-denatured casein was developed for the ultrasensitive and label-free detection of the β-gal produced by E. coli in real water samples. The heat-denatured casein coated on the graphene surface, as a probe linker and blocker, plays an important role in fabricating GEFT biosensor. The GFET biosensor response to the β-gal produced by E. coli has a wide concentration dynamic range spanning nine orders of magnitude, in a concentration range of 1 fg·mL-1-100 ng·mL-1, with a limit of detection (LOD) 0.187 fg·mL-1 (1.61 aM). In addition to its attomole sensitivity, the GFET biosensor selectively recognized the β-gal in the water sample and showed good selectivity. Importantly, the detection process of the β-gal produced by E. coli can be completed by a straightforward one-step specific immune recognition reaction. These results demonstrated the usefulness of the approach, meeting environmental monitoring requirements for future use.

Isolation and Identification of a Novel Anti-Dry Eye Peptide from Tilapia Skin Peptides Based on In Silico, In Vitro, and In Vivo Approaches

Tilapia skin is a great source of collagen. Here, we aimed to isolate and identify the peptides responsible for combating dry eye disease (DED) in tilapia skin peptides (TSP). In vitro cell DED model was used to screen anti-DED peptides from TSP via Sephadex G-25 chromatography, LC/MS/MS, and in silico methods. The anti-DED activity of the screened peptide was further verified in the mice DED model. TSP was divided into five fractions (TSP-I, TSP-II, TSP-III, TSP-IV, and TSP-V), and TSP-II exerted an effective effect for anti-DED. A total of 131 peptides were identified using LC/MS/MS in TSP-II, and NGGPSGPR (NGG) was screened as a potential anti-DED fragment in TSP-II via in silico methods. In vitro, NGG restored cell viability and inhibited the expression level of Cyclooxygenase-2 (COX-2) protein in Human corneal epithelial cells (HCECs) induced by NaCl. In vivo, NGG increased tear production, decreased tear ferning score, prevented corneal epithelial thinning, alleviated conjunctival goblet cell loss, and inhibited the apoptosis of corneal epithelial cells in DED mice. Overall, NGG, as an anti-DED peptide, was successfully identified from TSP, and it may be devoted to functional food ingredients or medicine for DED.

Application of Silicon Nanowire Field Effect Transistor (SiNW-FET) Biosensor with High Sensitivity

As a new type of one-dimensional semiconductor nanometer material, silicon nanowires (SiNWs) possess good application prospects in the field of biomedical sensing. SiNWs have excellent electronic properties for improving the detection sensitivity of biosensors. The combination of SiNWs and field effect transistors (FETs) formed one special biosensor with high sensitivity and target selectivity in real-time and label-free. Recently, SiNW-FETs have received more attention in fields of biomedical detection. Here, we give a critical review of the progress of SiNW-FETs, in particular, about the reversible surface modification methods. Moreover, we summarized the applications of SiNW-FETs in DNA, protein, and microbial detection. We also discuss the related working principle and technical approaches. Our review provides an extensive discussion for studying the challenges in the future development of SiNW-FETs.

A novel biosensor based on a bio-barcode for the detection of Mycobacterium tuberculosis

Tuberculosis (TB), the second (after COVID-19) deadliest infectious killer, is a chronic infectious disease caused by infection with Mycobacterium tuberculosis (M.T.), where early diagnosis and management are the key to containing the condition. Here, we report a novel biosensor for the detection of M.T. DNA based on magnetic separation, urease catalysis and silicon nanowire field effect transistor (SiNW FET) detection. M.T. DNA is sequence-specifically captured by magnetic nanoparticles and urease-labelled silica nanoparticles simultaneously to form a sandwich complex and urea is catalyzed into ammonium carbonate by urease modified on a sandwich complex. By using SiNW FET, the detection of M.T. DNA is realized indirectly by the detection of ammonium carbonate. The limit of detection (LOD) was determined to be 78.541 fM. The specificity of the biosensor was confirmed by detecting a panel of bacterial species. The utility of the biosensor was demonstrated in real-sample analysis and the recovery study of M.T. DNA was done in the genomic DNA extracted from cultured Mycobacterium tuberculosis. The biosensor holds promise to become a rapid, sensitive and accurate method for clinical diagnosis.

Tear-based MMP-9 detection: A rapid antigen test for ocular inflammatory disorders using vanadium disulfide nanowires assisted chemi-resistive biosensor

A sensitive, non-invasive, and biomarker detection in tear fluids for inflammation in potentially blinding eye diseases could be of great significance as a rapid diagnostic tool for quick clinical decisions. In this work, we propose a tear-based MMP-9 antigen testing platform using hydrothermally synthesized vanadium disulfide nanowires. Also, various factors contributing to baseline drifts of the chemiresistive sensor including nanowire coverage on the interdigitated microelectrode of the sensor, sensor response duration, and effect of MMP-9 protein in different matrix solutions were identified. The drifts on the sensor baseline due to nanowire coverage on the sensor were corrected using substrate thermal treatment providing a more uniform distribution of nanowires on the electrode which brought the baseline drift to 18% (coefficient of variations, CV = 18%). This biosensor exhibited sub-femto level limits of detection (LODs) of 0.1344 fg/mL (0.4933 fmoL/l) and 0.2746 fg/mL (1.008 fmoL/l) in 10 mM phosphate buffer saline (PBS) and artificial tear solution, respectively. For a practical tear MMP-9 detection, the proposed biosensor response was validated with multiplex ELISA using tear samples from five healthy controls which showed excellent precision. This label-free and non-invasive platform can serve as an efficient diagnostic tool for the early detection and monitoring of various ocular inflammatory diseases.

A highly sensitive and selective detection of 2,4,6-trinitrotoluene (TNT) using a peptide-functionalized silicon nanowire array sensor

A highly sensitive and specific detection of 2,4,6-trinitrotoluene (TNT), a typical nitrated aromatic explosive, was demonstrated by a silicon nanowire (SiNW) array sensor. The SiNW array devices were self-assembled and functionalized with the anti-TNT peptide to obtain unique sensitivity toward TNT. Also, the effect of the biointerfacing linker's chemistry and Debye screening with varied ionic strength of phosphate buffer solution (PBS) on TNT binding response signals were investigated. The optimization of the peptide-functionalized SiNW array sensor showed high sensitivity for TNT with a detection limit of 0.2 fM, the highest sensitivity reported to date. These initial promising results may help accelerate the development of portable sensors for femtomolar level TNT detection.