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Staphylococcus aureus is a common foodborne pathogen that can cause a suppurative infection after eating contaminated food. Detection of S. aureus plays an important role in the food industry. In this study, a strategy for the detection of S. aureus using magnetic separation (MS) technology combined with rolling circle amplification (MS-RCA) was proposed. The strategy used antibiotics to capture bacteria and employed RCA products as signal output probes. Vancomycin (Van), as a commonly used antibiotic, can recognize peptidoglycan on the cell wall of Gram-positive bacteria and can effectively identify target bacteria. Therefore, we prepared BSAylated-Van functionalized magnetic beads (Van-MBs) for the pre-enrichment of S. aureus. To ensure the selectivity of this method, we used biotin-pig IgG to bind S. aureus. In addition, to amplify the output signal of the MS-RCA strategy, we introduced streptavidin (SA) and successfully obtained the Van-MBs@S. aureus@biotin-pig IgG@SA@biotin-RCA probe complex and used the biotin-avidin-system (BAS) by combining magnetic separation technology and RCA technology to realize the enrichment and specific detection of S. aureus. Furthermore, by optimizing the experimental conditions such as the magnetic separation time and the amount of Van-MBs, the detection performance of this method was improved. Under the optimal conditions, the detection limit of this method for S. aureus was 3.3 × 10 2  CFU/mL in fruit juice, and it was less affected by other bacteria., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

A lectin magnetic separation (LMS) method for Staphylococcus aureus (S. aureus) was developed with the aim to improve the efficiency of magnetic nanoparticles and to expand the scope of bacterial recognition. Poly(ethylene glycol) (PEG)-mediated magnetic nanoparticles modified with streptavidin (MNP-PEG-SA) were synthesized and then applied to a two-step LMS based on the use of wheat germ agglutinin (WGA). Three specific methods for S. aureus detection (suitable for different requirements including detection time and sensitivity) were designed. The new LMS has improved anchoring efficiency (compared to two-step LMS methods) and requires a reduced number of magnetic particles. The Baird-Parker (B-P) method can detect S. aureus with a detection limit of 3 × 10 0  CFU·mL -1 within 15 h; the polymerase chain reaction (PCR) method can be finished within 4 h, with the lowest detection limit (LOD) of 3 × 10 2  CFU·mL -1 . The LOD of HRP-pig IgG-based colorimetric method is 3 × 10 5  CFU·mL -1 , and the method only lasts for 2 h. If combined with specific detection methods, it meets different needs for rapid detection of S. aureus. Graphical abstractSchematic representation of lectin magnetic separation (LMS) based on biotin-wheat germ agglutinin (WGA) and poly (ethylene glycol) (PEG)-mediated streptavidin-modified magnetic nanoparticles (MNP-PEG-SA) and three different quantification strategies (including B-P culture assay, PCR assay, and colorimetric assay) for S. aureus.

A novel sandwich strategy was designed to detect Staphylococcus aureus. The strategy is based on an antibacterial agent that captures bacterial cells and a fluorescein-labeled antibody that acts as the signal-output probe. Vancomycin (Van), which exerts a strong antibacterial effect on Gram-positive bacteria, was utilized as a molecular recognition agent to detect pathogenic bacteria. To effectively concentrate S. aureus, we used bovine serum albumin (BSA) as the amplification carrier to modify magnetic beads (MBs), which were then functionalized with Van. To improve the specificity of the method for S. aureus detection, we adopted fluorescein isothiocyanate (FITC)-tagged pig immunoglobulin G (FITC-pig IgG) as the signal probe and the second recognition agent that bound between the Fc fragment of pig IgG and protein A in the surface of S. aureus. To quantify S. aureus, we measured the fluorescence signal by flow cytometry (FCM). The use of multivalent magnetic nanoprobes (Van-BSA-MBs) showed a high concentration efficiency (>98%) at bacterial concentrations of only 33 colony-forming units (CFU)/mL. Furthermore, the sandwich mode (FITC-pig IgG/SA/Van-BSA-MBs) also showed ideal specificity because Van and IgG bound with S. aureus at two distinct sites. The detection limit for S. aureus was 3.3 × 10 1 CFU/mL and the total detection process could be completed within 120 min. Other Gram-positive bacteria and Gram-negative bacteria, including Listeria monocytogenes, Bacillus cereus, Cronobacter sakazakii, Escherichia coli O157:H7, and Salmonella Enteritidis, negligibly interfered with S. aureus detection. The proposed detection strategy for S. aureus possesses attractive characteristics, such as high sensitivity, simple operation, short testing time, and low cost.

Staphylococcus aureus is a spherical, gram-positive, pathogenic bacterium commonly associated with bovine mastitis and clinical infections. It is also recognized as a pathogen that causes outbreaks of food poisoning. The objective of this study was to develop and evaluate a rapid and reliable technique that combines propidium monoazide (PMA) staining with real-time quantitative (q)PCR to detect and quantify viable cells of Staph. aureus in milk powder and meat products. The inclusivity and exclusivity of the assay were evaluated using 58 strains belonging to 14 species. Serial dilutions of Staph. aureus cells were used to establish a standard curve and to confirm the effect of PMA treatment. Milk powder and meat products were used as the spiked foods, and the ability of PMA-qPCR to eliminate nonviable cells was determined in milk powder. Furthermore, meat products were inoculated with different concentrations of Staph. aureus and 10(5) cfu/g of Bacillus cereus and Salmonella enterica to test the interference by nontarget microorganisms. When PMA treatment was applied before DNA extraction, we were able to eliminate false-positive results with little effect on viable cells. The PMA-qPCR assay was specific and more sensitive than conventional PCR, and the level of detection was 3.0×10(2) cfu/g in spiked milk powder. Additionally, we observed no significant interference for the detection of viable Staph. aureus from other nontarget bacteria. The PMA-qPCR protocol is an effective and rapid method to quantify viable cells of Staph. aureus in food samples. The PMA-qPCR assay is specific and reliable, offering a valuable diagnostic tool for routine analysis in food and clinical diagnostic research at a reasonable cost., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Staphylococcus aureus is one of the main pathogens in dairy and meat products; therefore, developing a highly sensitive and rapid method for its detection is necessary. In this study, a quantitative detection method for Staph. aureus was developed using silica-coated magnetic nanoparticles and thermophilic helicase-dependent isothermal amplification. First, genomic DNA was extracted from lysed bacteria using silica-coated magnetic nanoparticles and amplified using thermophilic helicase-dependent isothermal amplification. After adding the nucleic-acid dye SYBR Green I to the amplicons, the fluorescence intensity was observed using a UV lamp or recorded using a fluorescence spectrophotometer. This detection system had a detection limit of 5×10(0) cfu/mL in pure culture and milk-powder samples and 5×10(1) cfu/mL in pork samples using a UV light in less than 2h. In addition, a good linear relationship was obtained between fluorescence intensity and bacterial concentrations ranging from 10(2) to 10(4) cfu/mL under optimal conditions. Furthermore, the results from contaminated milk powder and pork samples suggested that the detection system could be used for the quantitative analysis of Staph. aureus and applied potentially to the food industry for the detection of this pathogen., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Staphylococcus aureus (S. aureus) is a common foodborne pathogen that causes fever, vomiting, and other intestinal symptoms, and seriously affects human health and social safety. As a result, a reliable and sensitive detection technique for S. aureus must be developed. In this work, we proposed a sandwich assay on vancomycin functionalized magnetic beads (Van-MNPs) for S. aureus detection based on the specific binding between IgG and targets. The Van-MNPs were used as a tool for the separation of target bacteria. The biotin-modified IgG mediates binding between DNA nanoflowers (DNFs) and the target bacteria via interacting with streptavidin. The DNFs prepared by rolling circle amplification (RCA) were employed as a nano-container to enhance the capacity of biotins, and the streptavidin-horseradish peroxidase (SA-HRP) was loaded onto DNFs to catalyze the color change of TMB. Therefore, a colorimetric biosensor based on magnetic separation and rolling circle amplification was developed. The proposed methods for S. aureus detection showed a limit of detection (LOD) of 3.3 × 103 CFU/mL and excellent specificity. The biosensor has a certain reference value for the detection of S. aureus in juice. [ABSTRACT FROM AUTHOR]

In this work, a specific, sensitive, and accurate technique was presented for simultaneous detection of Salmonella spp., Shigella spp., and Staphylococcus aureus in food products, three of the more frequent foodborne pathogens that were usually reported in a variety of food matrices. An internal amplification control (IAC) was added in a multiplex PCR (mPCR) reaction system as an indicator of false negative result that can come from the presence of PCR inhibitors in food products. In the presence of inhibitor, no signal would result for the target genes as well as the IAC which results in a positive signal, thereby, eliminating false negative results. To ensure detection of only the viable cells, the effects of sodium deoxycholate (SD) in combination with propidium monoazide (PMA) treatment in the presence of dead cells and viable cells were investigated. Results showed that PMA treatment alone could not effectively inhibit the detection of 10 7 CFU/mL of dead Salmonella Typhimurium , Shigella sonnei , and S. aureus from PCR amplification. However, the SD in combination with PMA treatment gave negative results for PCR amplification of dead S. Typhimurium, S. sonnei, and S. aureus in pure culture and food products. When the developed SD-PMA-mPCR assay in combination with IAC was applied to detect the spiked food (milk, ground beef), the LOD of SD-PMA-mPCR assay for S. Typhimurium , S. sonnei, and S. aureus inoculated individually or inoculated simultaneously into milk or ground beef were 10 1 CFU/mL or 10 1 CFU/g after 15 h enrichment. The results suggested that the SD-PMA-mPCR assay in combination with IAC held promise for the detection of foodborne S. Typhimurium, S. sonnei, and S. aureus. [ABSTRACT FROM AUTHOR]

Rapid and credible detection of pathogens is essential to prevent and control outbreaks of foodborne diseases. In this study, a poly- l -lysine-functionalized magnetic beads (PLL-MB) strategy combined with a PCR assay was established to detect Staphylococcus aureus. We also detected Escherichia coli O157:H7 to further verify the strategy for gram-negative bacteria detection. Poly- l -lysine has strong positive charges because of its amino groups, which can conjugate with the carboxyl of carboxyl magnetic beads. Furthermore, it can be used to combine with bacteria through electrostatic adsorption. Under optimum conditions, the developed PLL-MB complexes showed 90% capture efficiency in phosphate-buffered saline and 85% capture efficiency in milk for S. aureus detection. The limit of detection of the PLL-MB-PCR assay was 102 cfu/mL (1.8 × 102 cfu/mL for S. aureus and 7 × 102 cfu/mL for E. coli O157:H7) in phosphate-buffered saline and milk samples. The whole assay can be performed within 4 h. The proposed strategy showed a lower limit of detection when compared with the conventional PCR assay without enrichment. In addition, this method exhibited the advantages of a high-efficient, cost-efficient, and simple operation, indicating its potential applications in foodborne pathogen detection. [ABSTRACT FROM AUTHOR]

Highlights • Wheat germ agglutinin lectin (WGA) was applied as a recognition agent for S. aureus enrichment. • The use of LMS method resulted in a high enrichment efficiency even at low concentrations (100–102 CFU/mL) of S. aureus. • A quantitative and specific detection strategy based on dsDNA stabilized AuNPs was developed for S. aureus detection. • The detection limit of this method was 3.5 × 100 CFU/mL. Abstract A novel 2-step lectin-magnetic separation (LMS) method combined with gold nanoparticle (AuNPs) -based colorimetric system for specifically and quantitatively detecting S. aureus in blood samples was established. In this study, wheat germ agglutinin lectin from Triticum vulgaris (wheat) (WGA) was applied for the first time as a recognition agent in a 2-step magnetic separation method using magnetic nanoparticles (MNPs) for effective and low-cost bacteria enrichment. A quantitative detection strategy based on the long dsDNA amplicons stabilized with AuNPs against salt-induced aggregation was investigated. The 2-step LMS method resulted in a high enrichment efficiency even at low concentrations (100–102 CFU/mL) of S. aureus in pure culture and blood samples. The AuNPs-based colorimetric system was applied for quantitative detection of S. aureus with a limit of detection (LOD) at 3.5 × 100 CFU/mL. The complete process starting with the blood samples treatment, 2-step LMS, and AuNPs-based colorimetric detection took only 7 h. The low cost and sensitive 2-step LMS combined with AuNPs-based colorimetric detection holds considerable potential for early sepsis diagnosis. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus was listed as the 2nd common food-borne pathogens, resulting in diseases such as pneumonia, pseudomembranous colitis, pericarditis and even sepsis. A rapid, simple and sensitive detection method is required to monitor food in cases of contamination by S. aureus. Hence, a novel immunochromatographic test strip (ICTS), based on the two-component reaction (i.e. digoxigenin and anti-digoxigenin, quantum dots-conjugated streptavidin and biotin) in test line with QDs as indicator, was developed for the rapid and sensitive detection of S. aureus. Genomic DNA from bacteria lysis by boiling was extracted easily and rapidly with silica-coated magnetic nanoparticles, and a species-specific gene was amplified by PCR using digoxigenin/biotin-labeled primers. The fluorescence of captured QD labels on the test line and control line served as signals was observed by UV light. The sensitivity and specificity of the ICTS were estimated using bacteria spiked food samples (artificially mixed with cell counts (108 CFU/mL for each bacterium) of Escherichia coli, Listeria monocytogenes and Lactobacillus plantarum). The limit of detection for S. aureus was 3 × 100 CFU/mL and 3 × 101 CFU/g in spiked milk powder and meat samples, respectively, which was not affected by those non-S. aureus strains. Our results showed that QDs-based ICTS was promising for rapid and sensitive detection of S. aureus within 2 h. Hence, this protocol might be useful for screening and monitoring the contamination of S. aureus in food products, and helpful for promoting the prevention and control of communicable disease caused by food-borne pathogen. [ABSTRACT FROM AUTHOR]

[Display omitted] • Broad-spectrum MNP-PEI was used to separate and enrich bacteria efficiently. • The entire detection procedure could be completed within 60 min. • The LOD was 2.9 × 102 CFU·mL−1 in spiked milk samples. Staphylococcus aureus (S. aureus) is a common foodborne pathogen, which could cause serious bacteremia and infective endocarditis. Establishing a rapid and low-cost method to capture and detect S. aureus in food samples is necessary. In this study, we have developed a method on the basis of polyethyleneimine-functionalized magnetic nanoparticles (MNP-PEI) and recombinase aided amplification (RAA) for rapid enrichment and analysis of S. aureus in milk. The capture efficiency of MNP-PEI on multiple strains of bacteria and influencing factors were studied. The limits of detection (LOD) of the MNP-PEI-RAA strategy were 2.9 × 101 CFU·mL−1 in phosphate-buffered saline (PBS) and 2.9 × 102 CFU·mL−1 in milk. The entire enrichment and detection processes could be completed within 60 min. The detection strategy based on MNP-PEI and RAA had low cost, short detection time, and high sensitivity. In addition, the broad-spectrum of bacteria captured by MNP-PEI was important for simultaneous analysis of a variety of bacteria, which provided an effective tool for evaluating the microbiological safety of food samples. [ABSTRACT FROM AUTHOR]

[Display omitted] • The APBA to replace expensive recognition molecules such as antibiotics. • The CE of APBA-PEG-MNs to 106 CFU/mL of S. aureus is higher than 92%. • This method can detect S. aureus within 80 min. • This strategy can realize the detection of S. aureus in different samples. Staphylococcus aureus (S. aureus) is one of the pathogens that seriously endanger human health and are widespread in nature. Food poisoning incidents caused by S. aureus frequently break out. Therefore, it is significant that a rapid and accurate method is established for S. aureus detection. In this study, a strategy using magnetic separation combine with fluorescence analysis was proposed for S. aureus detection. Boric acid can selectively enrich compounds with cis -diol groups through a reversible esterification reaction, and has been widely used in the identification of sugars and glycosylated molecules. As a boric acid derivative, 3-aminophenylboronic acid (APBA) has the advantages of stability, low cost, easy synthesis, etc. Therefore, using APBA as a recognition molecule to prepare magnetic nanomaterials can achieve the enrichment of S. aureus. In order to reduce steric hindrance and ensure the dominant orientation of APBA, thus improving the enrichment performance of target bacteria. The polyethylene glycol (PEG) was used as a mediator to prepare PEG-mediated APBA functionalized magnetic nanomaterials (APBA-PEG-MNs). In addition, this study used FITC-pig IgG to label S. aureus because the Fc fragment of IgG to bind protein A on the surface of S. aureus and realized the detection of S. aureus by detecting fluorescence. Under the optimal experimental conditions, the capture efficiency of APBA-PEG-MNs for S. aureus with the concentration of 2.7 × 106 CFU/mL in spinach, juice and pool water spiked samples was 92.6%, 91.6%, 91.6%. The limit of detection of the strategy in spiked samples was 2.7 × 102 CFU/mL within 80 min. [ABSTRACT FROM AUTHOR]

Foodborne pathogenic microorganism pose a serious threat to public health security; thus, constructing quick and sensitive methods for early screening foodborne pathogenic microorganism is necessary for human health. Teicoplanin (Teic) is a broad-spectrum biometric molecule, which can recognize Gram-positive (G+) bacteria. In this study, using bovine serum albumin (BSA) and PEG 2k as "carrier" and "linker", respectively. Teic was wired to magnetic beads (MBs) to form the biomimetic dandelion-like magnetic nanoparticles (MBs-PEG-BSA-Teic) to capture Staphylococcus aureus (S. aureus) and Listeria monocytogenes (L. monocytogenes). The MBs-PEG-BSA-Teic displayed excellent capture ability of S. aureus (> 93%) and L. monocytogenes (> 86%). After separation, the fluorescence probes were added, forming a "sandwich" structural compounds, namely, MBs-PEG-BSA-Teic~bacteria~fluorescence probes. The fluorescence intensity of the probes was measured by a multimode microplate reader. Consequently, this novel method showed high detection sensitivity to target model bacteria, and the detection limit of S. aureus and L. monocytogenes in PBS buffer solution and juice were achieved 101 CFU/mL, spinach and ground beef samples were achieved 102 CFU/g. The method has easy operation and high sensitivity, and it is less interfered by food matrix or negative bacteria; thus, this method is suitable for early screening G+ pathogen in suspected food samples. • BSA and PEG were used to mediate Teic with MBs, introducing multiple binding sites. • MBs-PEG-BSA-Teic with fluorescence method has low LOD and high specificity. • The method can be used for simultaneous detection of multiple G+ bacteria. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus (S. aureus) is a common pathogen that can cause severe foodborne diseases. Therefore, the detection of S. aureus in food has been the focus of attention. In this study, a strategy for the detection of S. aureus using magnetic separation technology combined with colorimetry was proposed. Phenylboronic acid, as a compound that had been widely used in the identification of sugars and sugar-based molecules, can selectively enrich compounds with cis -diol groups through a reversible esterification reaction. Hence, 3-aminophenylboronic acid (APBA) could be used as a recognition molecule to capture bacteria, because there were a large amount of peptidoglycan and lipopolysaccharide on the surface of Gram-positive bacteria and Gram-negative bacteria. At the same time, there are few studies on the use of APBA as magnetic separation recognition molecule to enrich pathogenic bacteria. Therefore, we prepared APBA-functionalized magnetic beads (APBA-MBs) for pre-enrichment of S. aureus and an APBA-MBs based untargeted magnetic separation was constructed to replace the traditional targeted magnetic separation. In order to realize the output signal and guarantee the specificity for detecting S. aureus , we used HRP-pig IgG because the Fc fragment of IgG could bind the protein A on the cell wall of S. aureus. Finally, the tetramethylbenzidine (TMB) color development solution was occurred the chromogenic reaction under the action of the HRP enzyme. Under the optimal experimental conditions, the limit of detection (LOD) of the APBA-MBs combined with color reaction was 3.0 × 102 CFU/mL in pure culture, fruit juice, pool water and spinach. • Using APBA to replace expensive recognition molecules such as antibiotics. • The CE of S. aureus can reach 90%–100% in the range of 106 to 101 CFU/mL. • The strategy has good performance in different matrixes. • The strategy can realize the detection of S. aureus within 2 h. [ABSTRACT FROM AUTHOR]

Bacillus cereus (B. cereus) and Staphylococcus aureus (S. aureus) are two typical foodborne pathogens. In this study, we proposed a new strategy that combined antibiotic with magnetic beads (MBs) and multiplex PCR (mPCR) to detect B. cereus and S. aureus in juice sample with high sensitivity and specificity. Teicoplanin (TEI) is a glycopeptide antibiotic which can identify Gram-positive bacteria. The polyethylene glycol (PEG) and bovine serum albumin (BSA) double-mediated teicoplanin functionalized magnetic beads (TEI-BPBs) were prepared for separation of target bacteria, and the triplex PCR was used for specific detection by nuc , cesB and flic gene. Under optimal conditions, the TEI-BPBs showed a good ability to simultaneously capture S. aureus (>83%) and B. cereus (>81%). The TEI-BPBs-mPCR assay efficiently detected target bacteria even in the presence of 105 CFU/mL non-target bacteria. The results showed that the limit of detection (LOD) of B. cereus and S. aureus in PBS and juice sample could reach 100 CFU/mL within 4 h. Compared with conventional methods, this method has lower LOD and shorter detection time. The results demonstrate that the constructed TEI-BPBs capture probe and triplex PCR could be successfully applied to the rapid separation and detection of B. cereus and S. aureus or other Gram-positive pathogens in food samples. • The strategy of TEI-BPBs-mPCR was established successfully. • TEI-BPBs could identify and enrich Gram-positive pathogens. • The method could simultaneously detect B. cereus and S. aureus with high specificity. • Had lower LOD and shorter detection time than conventional PCR without MST. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus is a common foodborne pathogenic microorganism. A modified propidium monoazide (PMAxx) dye combined with recombinase aided amplification (RAA) was proposed for the rapid and real-time detection of viable S. aureus. PMAxx, a kind of nucleic acid dye is used to distinguish viable bacteria from dead bacteria. Additionally, RAA technique has the advantage of a short detection time (20 min) and uniform temperature (39 °C), which is of great significance for the efficient detection of S. aureus. The S. aureus nuc gene was used as primer and probe in a microplate assay. The effect of PMAxx treatment exhibited permeation of the dead cell membranes that was observed under confocal laser scanning microscope (CLSM). After the enrichment of viable target bacteria ranging from 5.4 × 101 to 5.4 × 103 CFU/mL, the LOD for viable S. aureus was 102 CFU/mL under 3 h enrichment and 101 CFU/mL under 6 h enrichment in artificially contaminated milk, respectively. In the presence of nontarget bacteria at 106 CFU/mL, the system could detect 107 CFU/mL S. aureus in milk sample. The proposed PMAxx-RAA assay exhibited potential for the accurate and rapid viable S. aureus detection in milk. • Real-time fluorescence detection reactions of Staphylococcus aureus were reported. • PMAxx was selected to more accurately eliminate the interference from dead cells. • Verify the effect of PMAxx through confocal laser scanning microscope (CLSM). • The assay could detect 101 CFU/mL viable cells in milk sample after 6 h enrichment. [ABSTRACT FROM AUTHOR]

• Developed tapered no-core fiber coupler for ultrahigh-sensitivity biosensing. • Provide "additional" stability due to the coupler structure. • Demonstrated limit of detection of Staphylococcus aureus as low as 3.1 CFU/mL, the best value reported so far. • The sensor structure has potential for other applications such as disease,medical diagnostics and food safety inspection. An ultra-high sensitivity label-free optical fiber biosensor for inactivated Staphylococcus aureus (S. aureus) detection is proposed and investigated in this study, with additional advantages of robust and stability compared to traditional tapered fiber structure. The proposed fiber biosensor is based on a tapered singlemode- no core-singlemode fiber coupler (SNSFC) structure, where the no core fiber was tapered to small diameter (taper-waist diameter of about 10 μm) and functionalized with the pig immunoglobulin G (IgG) antibody for detection of S. aureus. The measured maximum wavelength shift of the sensor for an S. aureus concentration of 7 × 101 CFU/mL (colony forming unit per milliliter) is 2.04 nm, which is equivalent to a limit of detection (LOD) of 3.1 CFU/mL (a highest LOD reported so far for optical fiber biosensors), considering the maximum wavelength variation of the sensor in phosphate buffered saline (PBS) is ±0.03 nm over 40 min, where 3 times of maximum wavelength variation (3 × 0.03 = 0.09 nm) is defined as measurement limit. The response time of the developed fiber sensor is less than 30 min. The ultra-sensitive biosensor has potential to be widely applied to various areas such as disease, medical diagnostics and food safety inspection. [ABSTRACT FROM AUTHOR]