Naked-eye Detection Research Articles

Simultaneous monitoring of humidity and temperature by polarization volume gratings utilizing responsive cholesteric liquid crystals

Optical sensing devices are utilized for noncontact operation in harsh environments due to their advantage of local separation between the measurement and detector systems. Cholesteric liquid crystals (CLCs) with vivid structural colors are integrated into optical sensors, attracting significant interest for naked-eye detection. To enable vision-based, real-time remote monitoring, we propose a cost-effective method to convert the stimuli-responsive reflection change of CLCs into recordable diffraction patterns using polarization volume gratings (PVGs). This enables real-time remote readout of environmental parameters. PVGs are constructed through holographic polarization interference and photoalignment technologies. The diffraction efficiency of PVGs varies with relative humidity (RH). To improve sensing accuracy and extend the monitoring range of RH, we employ two methods: an orthogonal grating structure and dual-wavelength detection optical path. In addition, we demonstrate the simultaneous measurement of humidity and temperature by cascading independently responding PVGs. We believe that this work will provide a broader perspective and expand the application of light dimensions in LC-based optical sensing.

Naked-eye detection of Fe3+ and photothermal applications of flexible and sustainable banana pith stabilized silver nanoparticle-rice starch composite

Naked-eye detection of Fe3+ and photothermal applications of flexible and sustainable banana pith stabilized silver nanoparticle-rice starch composite

Naked eye detection of anions: Dihydrazone receptor-based visual sensing

In this study, we designed and synthesized a novel colorimetric sensor for fluoride ions by integrating a thienodicarbohydrazide framework with salicylaldehyde, resulting in a unique bis-hydrazone-phenol receptor. This sensor exhibited exceptional selectivity for fluoride and acetate ions in nonaqueous environments, with detection visible to the naked eye. Upon interaction with fluoride ions, the receptor underwent a significant red shift in its UV–Visible absorption spectrum, moving from an absorption maximum at 332 nm–380 nm, signalling the recognition event. Acetate ions induced a similar shift. The binding interactions were thoroughly investigated, with a Jobs plot revealing a 1:1 receptor-anion complex formation with fluoride ions and a 1:2 complex with acetate ions. Further validation came from 1H NMR titration, which confirmed the presence of hydrogen bonding interactions between the receptor and the ions. The receptor demonstrated remarkable binding constants of 5.2 × 10⁴ M−2 for acetate and 1.6 × 10⁴ M−1 for fluoride ions, highlighting its strong and selective affinity. Fluorescence titrations further confirmed the receptor's potential as a chemo sensor, showing distinct emission changes in the presence of fluoride and acetate ions. This study not only underscores the receptor's capability for visual detection of fluoride ions in non-aqueous systems but also paves the way for its application in diverse analytical and environmental settings.

Au@Pt nanoparticles-based signal-enhanced lateral flow immunoassay for ultrasensitive naked-eye detection of SARS-CoV-2.

With SARS-CoV-2 N protein as a model target, a signal-enhanced LFIA based on Au@Pt nanoparticles (NPs) as labelsis proposed. This Au@Pt NPs combined the distinguished localized surface plasma resonance (LSPR) effect of Au NPs and the ultrahigh peroxidase-like catalytic activity of Pt NPs. Au@Pt NPs could trigger substrate chromogenic reaction, generating acolor signal orders of magnitude darker than their intrinsic color. In the detection, after the coloration of the strips, 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 were added, and adark blue chelate (OxTMB) was produced soon, enhancing the band color significantly. After the signal amplification, the naked-eye detection limit for N protein reached 40pg/mL. The detection sensitivity enhanced more than 1000 times than that without signal amplification. Compared with mainstream LFIA requiring complex readout instruments, theAu@Pt-based LFIA achieved a comparable sensitivity usingnaked eyesdetection. This point is crucial, especially for unprofessional users or low-resource areas. Hence, this signal-enhanced LFIA may serve as a sensitive, cost-effective, and user-friendly detection method. It can shorten the testing window period and help identify early infections.

A smartphone-assisted chromogenic and fluorogenic dual-channel sensor for specific determination of toxic Pb2+ ions with multifaceted applications

Heavy metal pollutants, such as Pb2+ ions, pose a substantial hazard to human health and ecosystems, and it was of great significance to develop cost-effective and portable techniques for online and visual detection of Pb2+. Herein, we fabricated a novel chromogenic and fluorogenic dual-channel sensor NQA through a Schiff base reaction involving a dicyanoisophorone derivative and isoniazid, enabling effective detection of Pb2+ ions. Upon complexation with Pb2+ ions at a 1:1 M ratio, the fluorescence intensity of NQA exhibited a remarkable enhancement. The naked-eye colorimetric detection utilizing NQA demonstrated a distinct color change to specific Pb2+ ions concentration from yellow to light pink. Based on this principle, a smartphone-assisted sensing platform was developed for visual and high-quality identification of Pb2+ in real samples. The UV binding constant for Pb2+ ions was determined to be 1.84 × 105 M−1, with a detection limit of 0.38 μM. Furthermore, the versatility of NQA extended to applications in naked-eye test paper experiments, the detection of Pb2+ ions in real water samples and living cells, showcasing its potential for environmental and biological monitoring.

A colorimetric sensor based on 2,3-bis(6-chloropyridin-2-yl)-6-fluoroquinoxaline for naked-eye detection of Iron (III) and its application in real sample analysis

Iron ions are crucial for numerous biological processes, and the levels of these ions have a significant impact on human well-being. Hence, it is essential to identify the level of Iron ions using a suitable technique. A new colorimetric sensor, namely “2,3-bis(6-chloropyridin-2-yl)-6-fluoroquinoxaline” (CF), has been introduced to detect Fe3+ through naked-eye observation. The sensor exhibits remarkable specificity towards Fe3+ compared to other metal ions in aqueous environments. Furthermore, it undergoes a substantial color change from colorless to yellow, which is visible without needing additional equipment. The complex formation was proposed to be in 1:1 ratio based on the Job’s plot and molar ratio plot. The maximum sensitivity of CF towards Fe3+ was found at pH 6 to 8. Minimal or negligible interference was noticed from different metal ions in the detection of Fe3+. The binding constant using Benesi-Hildebrand was estimated at 1.434 × 104 M−1. Gibbs free energy was determined –23.728 kJ/Mol. The LOD and LOQ were calculated at 0.378 and 1.26 µM, respectively. The probe CF was utilized to recover Fe3+ in tap water, resulting in recovery percentages ranging from 99.44 to 103.61. This indicates that the CF has the ability to identify Fe3+ in environmental samples

New phenanthridine-based multi-functional chemosensor for selective detection of Th4+ and Hg2+ ions in both aqueous and solid state

A new phenanthridine-based multifunctional chemosensor (L), was synthesised via a green synthetic route and characterised using FT-IR, NMR and HRMS analysis. The sensing application of L towards metal ions in both solution and solid-state was studied using UV–vis and fluorescence spectroscopy, which exhibits dual-sensing behaviour for Th4+ and Hg2+ ions with good recyclability. In aqueous acetonitrile, L showed rapid response for the detection of environmental toxic metal ions and has a very low analytical detection limit of 125.5 pM and 1.94 nM for Th4+ and Hg2+ions respectively, which is remarkably lower than the World Health Organization standard. The cation binding property of the L with Th4+ and Hg2+ions was investigated by Job plot, 1H NMR titration, HR-MS and DFT calculation. The in-situ formed ensemble L-Hg2+ was further applied in the naked-eye detection of Cys (Cystine) and His (Histidine) over other common amino acids. The utility of L for real-time detection of Hg2+ and Th4+ ions was explored in various sources of environmental water samples, test paper strips, fingerprint imaging, fluorescent ink and smartphone-assisted sensing techniques, demonstrating the promising on-site visualization of the probe in controlling the toxicity levels in wastewater sources without resorting to expensive instruments.

Development of sensitive napthaquinone-pyridine hydrazone based chemosensor for the colorimetric detection of Cu2+ ion in an aqueous solution

A novel naphthoquinone-pyridine hydrazone (NQPH) based chemosensor was synthesized through the condensation reaction of 2-hydroxynaphthoquinone aldehyde and 2-pyridine carboxylic acid hydrazide. The aqueous buffered solution of NQPH quickly changes color from orange to green upon addition of Cu²⁺ ions with appearance of new absorption band at 452 nm. The UV–vis titration indicated binding constant (K) of chemosensor NQPH with Cu²⁺ was determined to be 2.5 × 104 M⁻¹ (log K = 5.39), and the detection limit for Cu²⁺ ions was found to be 4.35 µM. Analysis using a Job plot based on UV–vis data, along with mass spectrometry, indicated a 1:1 stoichiometry between NQPH and Cu²⁺. Density Functional Theory (DFT) calculations were used to determine the minimum energy conformations, molecular properties and vibrational frequency analysis of NQPH and its Cu²⁺ complex. The DFT results showed the reduction in the HOMO-LUMO gap when NQPH interact with Cu²⁺, indicating intramolecular charge transfer (ICT). The practical application of NQPH was demonstrated by creating test strips for the naked-eye detection of Cu²⁺ and by measuring Cu²⁺ in real water samples.

Novel lateral flow assay to detect H2O2 by utilizing self-biotinylation of G-quadruplex

We herein describe a novel lateral flow assay (LFA) to detect H2O2 by utilizing self-biotinylation of G-quadruplex (G4). In this strategy, the G4 strand promotes the self-biotinylation of G4 itself in the presence of H2O2, which is then allowed to bind to the FAM-labeled complementary detector probe. The resulting biotin-labeled G4/FAM-detector probe complex is captured on the test line, producing a red-colored band during lateral flow readout. Based on this unique approach, we achieved the naked-eye detection of target H2O2 at concentrations as low as 1 μM, with reliable quantification down to 0.388 μM. This method also demonstrated exceptional specificity in distinguishing H2O2 from other non-target molecules. We further verified its versatile applicability by reliably identifying another biomolecule, choline, by coupling with choline oxidase, which generates H₂O₂ during oxidation. This novel LFA strategy holds great promise as a powerful point-of-care testing (POCT) platform for detecting a large spectrum of target biomolecules by employing their corresponding oxidases.

Synthesis of Multifunctional Chemosensors for Naked Eye Detection of Cu2+ and Hg2+; Application in Paper Strips, Water, and Food Sample

AbstractThree chemosensors ISA‐1, ISA‐2, and ISA‐3 were synthesized for the detection of Cu2+ and Hg2+ ions in a 50% H₂O‐DMF solution. ISA‐1 is specifically designed for the detection of Cu2+ ions, while ISA‐2 can detect both Cu2⁺ and Hg2⁺ ions. Upon interaction with Cu2⁺, ISA‐1 undergoes a naked‐eye colorimetric transition from pink to blue. ISA‐2 exhibits a similar pink‐to‐blue color change in the presence of Cu2+ ion, however, colorless when exposed to Hg2+ ion. The detection limits for Cu2+ using ISA‐1 and ISA‐2 are 0.574 ppm and 0.0074 ppm, respectively, both of which are significantly lower than the WHO guideline of ≤1.5 ppm for Cu2+ in drinking water. These chemosensors have also been successfully integrated into paper strips and logic gate systems and applied for the analysis of water and food samples.

Dual-mode iodine sensing: Colorimetric and electrochemical detection methods using functionalized gold nanoparticles

Iodine in natural and treated waters exists mainly as iodide, iodate, and molecular iodine (I2). I2 is a highly volatile and reactive species impacting biological and chemical systems. Iodine, a vital micronutrient, is essential for human and animal growth and metabolism. It also plays a crucial role in synthesising artificial adrenaline within the metabolic processes of humans and animals. It is also widely used as an antiseptic, disinfectant, and for emergency water disinfection. Moreover, iodine deficiency can result in various diseases, especially hypothyroidism and goitre. Given its critical functions, it is imperative to have a straightforward, dependable, and efficient method for monitoring iodine levels. This study introduces a simple and innovative I2 detection system based on its reactivity, toxicity, and role as an indicator of oxidative conditions in water. It operates in terms of based on optical and electrochemical signal changes, utilising the anti-aggregation mechanism of gold nanoparticles (AuNPs) and 6-mercaptohexanol (MHA) for sensitive and selective detection under mild conditions. I2 determination is achieved by observing the colour change in AuNPs, which is influenced by competitive interactions between MHA, I2, and AuNPs. The optical detection system, with its low detection limit (LOD=260 nM), is based on the straightforward observation of colour changes. On the other hand, the electrochemical detection method utilises changing redox peaks observed in anodic region, providing selective and sensitive I2 detection (LOD=100 nM). The probe effectively detects the presence of I2 in real water samples as a practical application. Moreover, the proposed method revolutionises I2 detection by incorporating a smartphone for signal reading, eliminating the need for specialised equipment and significantly reducing the detection cost. This cost-effective approach carries the potential to expedite on-site and naked-eye I2 detection, opening up new possibilities for research and application.

Dual colorimetric platforms for direct detection of glyphosate based on Os-Rh nanozyme with peroxidase-like activity

BackgroundTo minimize the impact of pesticide residues in food on human health, it is necessary to enhance their detection. Recently, many nanozyme-based colorimetric methods for pesticides detection have been developed, however, they often required the assistance of natural enzymes, which made the process and result of methods susceptible to the stability and activity of natural enzymes. To overcome these drawbacks, methods for direct detection of pesticides using nanozymes have been developed, and there are few studies in this field currently. Thus, it is of great research and practical significance to develop more nanozymes-based colorimetric methods for direct detection of pesticides. ResultsDual colorimetric platforms based on Os-Rh nanozyme with excellent peroxidase-like activity were constructed for directly detection of glyphosate in this work. Results showed that glyphosate was able to sensitively and selectively inhibit the peroxidase-like activity of Os-Rh nanozyme through hindering the decomposition of H2O2 by Os-Rh nanozyme to produce HO∙. Based on this, the dual colorimetric platforms achieved highly sensitive detection for glyphosate over a wide linear concentration range (50–1000 μg L−1 in solution platform and 200–1000 μg L−1 in paper platform), with the detection limits of 28.37 μg L−1 in solution platform and 400 μg L−1 (naked-eye detection limit)/123.25 μg L−1 (gray scale detection limit) in paper platform, respectively. Moreover, the dual colorimetric platforms possessed satisfactory reliability and accuracy for practical applications, and has been successfully applied to the detection of real samples with the spiked recoveries of 92.78–102.75 % and RSD of 1.17–3.88 %. SignificanceThe dual colorimetric platforms for glyphosate direct detection based on Os-Rh nanozyme developed in this work not only owned considerable practical application potential, but also could provide more inspirations and ideas for the rational design and development of colorimetric sensing methods for the rapid detection of pesticides based on nanozymes.

Alkali metal-doped C20 fullerene sensors for COVID-19 biomarker detection: DFT insights into naked-eye and infrared techniques

Prompt diagnosis and prevention from coronavirus disease (COVID-19), a highly contagious infection, are critically required. While PCR testing is effective, it is costly, painful, and time-consuming. Alternatively, breath analysis for detecting COVID-19 provides a cost-effective and instant diagnostic approach. COVID-19 infected patients exhale ethyl butyrate (EB) as a biomarker of the infection. This study explores the doping of C20 fullerene with alkali metals to enhance its ability to detect ethyl butyrate. EB was weakly adsorbed onto C20 and strong adsorbed on doped fullerenes (M@C20) with maximum adsorption energies of −27.66 kcal/mol for Li@C20. QTAIM and IRI analyses confirmed Van der Waals interactions between EB and M@C20. NBO and MEP analyses provided evidence of charge transfer from the biomarker towards the M@C20. This charge transfer decreased the carbonyl bond stretching frequency from 1838 cm−1 to 1772, 1782, and 1788 cm−1 in three complexes (EB−Li@C20, EB−Na@C20, and EB−K@C20), respectively. This IR analysis supports the potential application of doped fullerenes in infrared-based detectors. Absorption maxima (λmax) were calculated as 534 nm (green), 594 nm (yellowish orange), and 587 nm (yellow) for three complexes. These shifts indicate potential application of M@C20 in naked-eye detectors. The shortest recovery time was 2.9 × 10−11 s for K@C20, suggesting it a suitable reusable sensor. These findings enable the development of fullerene-based sensors for both naked-eye and infrared-based detection of COVID-19.

Highly selective optical and naked-eye recognition of L-cystine through spectroscopy and development of cellulose paper nano biosensor test strips for the early diagnosis of cystinuria

Accurate sensing of small biomolecules from complex biofluid media remains a challenge due to adverse interaction of metallic salts and other biofluid components. L-cystine is the most important biomarker for the disease cystinuria. Recognition of L-cystine in urine is thus fundamental for the timely detection of cystinuria and related chronic kidney disease (CKD). Poor solubility of L-cystine offer limits to design suitable sensors. Herein, we report the synthesis of thioglycolated-β-CD (TG-β-CD) anchored silver nanoparticles (AgNP) as a potential receptor (TG-β-CD⊃AgNP) for the effective optical recognition and quantification of L-cystine through UV–Vis and SERS (surface enhanced Raman spectroscopy) spectroscopic fingerprinting and suitable colourimetric naked-eye detection of L-cystine by indicator displacement assay. Methyl orange (Met-O) indicator was precomplexed with the receptor to generate the probe solution (Met-O@TG-β-CD⊃AgNP). Indicator has been exchanged from Met-O@TG-β-CD⊃AgNP by the addition of L-cystine, with an instantaneous visible colour change from yellow to red. The method is tolerable to other interfering abundant ions and biomolecules. Based on the innovative sensing assay a cellulose paper-dye test strip is developed for point-of-care detection and quantification of the biomarker. Structures of TG-β-CD, TG-β-CD⊃AgNP and Met-O@TG-β-CD⊃AgNP were elucidated by UV–Vis, FT-IR, PXRD, 1H NMR, etc. spectroscopy. Scanning electron microscopy (SEM) was used to examine the morphology of TG-β-CD, AgNP and TG-β-CD⊃AgNP. The chemical changes during the assay were evaluated by conductance, UV–Vis and SERS. The competitive displacement of the indicator and UV turn-on at ppm level analyte concentration made the process compatible for day-to-day point-of-care units.

Versatile and efficient fabrication of signal “turn‐on” lateral flow assay for ultrasensitive naked eye detection of small molecules based on self‐assembled fluorescent gold nanoclusters‐antigen aggregates

Versatile and efficient fabrication of signal “turn‐on” lateral flow assay for ultrasensitive naked eye detection of small molecules based on self‐assembled fluorescent gold nanoclusters‐antigen aggregates

Selective Naked-Eye Detection of Lung Squamous Cell Carcinoma Mediated by lncRNA SOX2OT Targeted Nanoplasmonic Probe.

The application of nanobiotechnology in biomolecule detection can provide fast and accurate tests for diagnosing molecular changing-associated diseases. The use of AuNPs-thiolated probe conjugates has long been considered as an alternative method for the detection of specific DNA/RNA targets. Here, we present a colorimetric direct detection method for the SOX2OT transcript, long noncoding RNAs (lncRNAs), by using a poly guanine tail (G12) as a template for in situ synthesis of gold nanoparticles (AuNPs) without any chemical modification or DNA labeling. We have then developed this proposed detection system based on two complementary sequences of long noncoding RNA SOX2OT with an extra strand of poly G12. Using this method, we were able to differentiate lung squamous cell carcinoma from adenocarcinoma samples. Based on this disclosure, this invention provides a simple visual method to detect specific lncRNA sequences without the need for amplifying the target lncRNA and discriminate squamous cell carcinoma from adenocarcinoma samples. Our invention provides a diagnostic kit to detect RNA by means of direct detection (PCR-free) of the lncRNA by in situ synthesis of AuNPs based on two probes with an extra strand of poly G12.

Multicolorimetric Sensor Array Based on Silver Metallization of Gold Nanorods for Discriminating Dopaminergic Agents.

Dopaminergic agents are compounds that modulate dopamine-related activity in the brain and peripheral nerves within the pathways on both sides of the blood-brain barrier. Atypical levels of them can precipitate a multitude of neurological disorders, whose timely diagnosis signifies not only stopping the advancement of the illness but also surmounting it. A silver metallized gold nanorod (AuNRs) conditional sensor array, designed to detect dopaminergic agents for assessing nervous system disorders, yielded significant results in simultaneous detection and discrimination of Benserazide (Benz), Levodopa (L-DOPA), and Carbidopa (Carb). The array was composed of two different concentrations of silver ions as sensor elements (SEs), which generated unique signatures indicative of the presence of reductive target analytes, triggered by the incongruent formation of the Au@Ag core-shell, causing visual and fingerprint colorimetric patterns. Generating diverse responses is the key to the functionality of array-based sensing, which facilitated achieving spectral and color variation originating from the blue shift of AuNRs longitudinal localized surface plasmon resonance (LLSPR) in the extinction spectrum. Also, employing a smartphone camera enables clear visual discrimination across an extensive concentration span. Pattern recognition through linear discriminant analysis (LDA) underscored the robust discrimination accuracies of this sensor, along with quantification by means of partial least-squares regression (PLSR), affirming its potential for practical applications. Notably, the array demonstrated high sensitivity in detecting varied concentrations of target analytes, even in commercial drug samples. The sensor responses exhibited a linear correlation with the concentrations of Benz, L-DOPA, and Carb ranging from 1.59 to 100.0, 5.26 to 100.0, and 5.32 to 100.0 μmol L-1, respectively, and the minimum detectable concentrations for Benz, L-DOPA, and Carb were measured at 0.53, 1.75, and 1.77 μmol L-1, respectively. The implemented machine-learning-empowered array-based sensor represents advancements in dopaminergic agent tracing and naked eye detection.

2-hydroxy-1- Naphthaldehyde Based Colorimetric Probe for the Simultaneous Detection of Bivalent Copper and Nickel with High Sensitivity and Selectivity.

A neoteric colorimetric probe based on 2-hydroxy-1-naphthaldehyde (PMB3) was designed and synthesized for the real-time as well as on-site naked-eye detection of Cu2+/Ni2+ ions. Various physicochemical methods were employed to characterize the probe, and its colorimetric response to different metal ions was meticulously investigated. The probe, PMB3, exhibited a sensitive colorimetric response to Cu2+/Ni2+ ions among other competing metal ions, culminating in a prominent colour change from colourless to yellow. The stoichiometry of the ligand metal complexes was ascertained to be in a 1:1 ratio using Job's plot analysis, which was further corroborated by ESI-MS data. With detection limits of 4.56µM for Cu2+ and 2.68µM for Ni2+, the method was effectively extended to real sample analysis, ensuring propitious results that closely aligned with the actual values.

Advancing paper microfluidics: A strategic approach for rapid fabrication of microfluidic paper-based analytical devices (µPADs) enabling in-vitro sensing of creatinine

Paper-based microfluidic sensors for point-of-care applications represent an exceptional strategy for facilitating rapid sensing within clinical settings. Despite their considerable promise, the ongoing research objective lies in efficiently printing hydrophobic microfluidic channels (µPADs) onto hydrophilic paper while minimizing expenditure. This research paper introduces an advanced, economic, and efficient method for the rapid fabrication of µPADs on paper substrates, enabling immediate colorimetric detection of creatinine in artificial urine using Jaffe’s reagent. The process involves a modified DIY RepRap 3D printer with an integrated technical drawing pen filled with the solution of Polydimethylsiloxane (PDMS) and hexane. This solution creates hydrophobic domain barriers on a flexible nylon-based paper substrate, effectively confining the aqueous medium within the microfluidic channels. We report visual detection of a broad spectrum of creatinine concentrations ranging from 5 mg/dL to 450 mg/dL through the vibrant Janovsky complex appearance on the microfluidic domains. The study identifies the limiting concentration on µPADs as 500 mg/dL. The innovative procedure demonstrates exceptional selectivity, exhibiting a maximum interference of only 0.97 % from potentially interfering substances. This rapid, naked-eye detection of creatinine on nylon 6,6 membranes offers a user-friendly and economical approach, enhancing the capabilities of colorimetric visualization in point-of-care applications.

Development of Aptamer-Functionalized Gold Nanoparticles as Probes in Point-of-Care Diagnostic Device for Rapid Detection of Multidrug-Resistant Bacteria in Bombyx mori L. .

The sericulture industry suffers severe crop losses due to various silkworm diseases, necessitating the development of further technologies for rapid pathogen detection. Here, we report an all-in-one portable biosensor that combines conjugated gold nanoparticles (Au NPs) with an aptamer-based lateral flow assay (LFA) platform for the real-time analysis of Mammaliicoccus sp. and Pseudomonas sp. Our platform enables sample-to-answer naked eye detection within 5 min without any cross-reactivity with other representatives of the silkworm pathogenic bacterial group. This assay was based on the sandwich-type format using a bacteria-specific primary aptamer (Apt1) conjugated with 23 nm ± 1.27 nm Au NPs as a signal probe and another bacteria-specific secondary aptamer (Apt2)-coated nitrocellulose membrane as a capture probe. The hybridization between the signal probe and the capture probe in the presence of bacteria develops a red band in the test line, whose intensity is directly proportional to the bacterial concentration. Under the optimal experimental conditions, the visual limit of detection of the strip for Mammaliicoccus sp. and Pseudomonas sp. was 1.5 × 104 CFU/mL and 1.5 × 103 CFU/mL, respectively. Additionally, the performance of the LFA device was validated by using a colorimetric assay, and the results from the colorimetric assay are consistent with those obtained from the LFA. Our findings indicate that the developed point-of-care diagnostic device has significant potential for providing a cost-effective, scalable alternative for the rapid detection of silkworm pathogens.