PhD student at the University of Manchester, Manchester Institute of Biotechnology, The University of Manchester


I formulate innovative bio-chemistry to rapidly detect the bacterial pathogens using light signal.

Bacterial pathogens are key targets for detection and identification in food safety, medicine, public health, and world security. Bacterial infection is a common factor of morbidity and mortality globally. Although there is availability of antibiotics, these infections are often misdiagnosed or there is an intolerable diagnostic delay. Recently, the threat from biological warfare (BW) agents has become a critical issue both on the battlefield and for general public safety. BW agent-based weapons are suited to use by terrorists because the threat is cost-effective, can potentially cause a mass casualty, easily to produces and difficult to detect. Bacteria and its pathogens are one of the most prevalent types of BW agents, whereby they are difficult to kill, easy​ to spread at fast rate and result in acute or delayed toxicity. Current methods of bacterial detection rely upon laboratory-based techniques such as cell culture, microscopic analysis, and biochemical assays which are time-consuming, costly and require specialist equipment and trained users. Therefore the technology to rapidly detect the bacteria at very low level is compulsory. Optical biosensors will be particularly useful technology by offering a fast detection, which provided almost immediate interactive information about the sample tested, thus enabling users to take corrective measures before consumption and help to prevent foodborne disease. My research aims are to create a better sensor to detect and monitor the presence of the bacteria and its viruses at rapid and low cost. In my work, I formulate an optical sensor to rapidly detect multi-species of pathogenic bacteria just using a single sample analysis. I used special bio-chemistry formula on the nanoscale sensing layer to generate the light signal so that the bacteria can be detected at the shortest time with very low concentration. The sensor offers almost 99% positive results to detect the right species of bacteria, thus avoiding the false result. This sensor will contribute to help the world to control the health and safety of the netizen, especially when dealing with a spectacularly portable virus such as in the airport or borderline area. Thus, the innovation will enable the government to control and stop the spreading viruses, especially from the infected and risky country. This research is really beneficial as we can use the sensor technology on the bio-chemistry formulas to design other sensors for other application as well.


SIP-Based Thermal Detection Platform for the Direct Detection of Bacteria Obtained from a Contaminated Surface

Abstract: Surface detection of bacteria has been proven difficult and time-consuming. Different recovery techniques yield varying numbers of bacteria. Subsequently, bacterial culturing, used for identification of these bacteria, will take several hours. In this article, the potential of a newly developed thermal biomimetic sensor for the detection of bacteria on surfaces is described. Previously this thermal biomimetic sensor has proven to be able to detect and quantify different bacteria in various liquid media such as buffer and spiked urine samples. In this article, laboratory surfaces are contaminated with increasing concentrations of Escherichia coli. Bacteria are recovered from the surfaces using commercially available swab rinse kits (SRK). A calibration curve is created by coating chips with surface-imprinted polymers (SIPs), serving as synthetic bacteria receptors, and exposing them to increasing concentrations of E. coli. Next, concentrations of E. coli in the SRK buffer are measured and quantified. The results show that it is possible to detect E. coli recovered from surfaces. Although quantification has been proven difficult as the dynamic range of the sensor is relatively narrow and the bacterial load obtained by using SRK is low, the sensor is able to give an indication about the concentration present on the surface. The results in this article illustrate that the thermal biomimetic sensor is a fast, low-cost, and label-free device useful in surface detection of E. coli, and seems a promising tool for future on-site bacterial detection.

Pub.: 15 Jan '18, Pinned: 16 Jan '18

Engineering nanostructured porous SiO2 surfaces for bacteria detection via "direct cell capture".

Abstract: An optical label-free biosensing platform for bacteria detection ( Escherichia coli K12 as a model system) based on nanostructured oxidized porous silicon (PSiO(2)) is introduced. The biosensor is designed to directly capture the target bacteria cells on its surface with no prior sample processing (such as cell lysis). The optical reflectivity spectrum of the PSiO(2) nanostructure displays Fabry-Pérot fringes characteristic of thin-film interference, enabling direct, real-time observation of bacteria attachment within minutes. The PSiO(2) optical nanostructure is synthesized and used as the optical transducer element. The porous surface is conjugated with specific monoclonal antibodies (immunoglobulin G's) to provide the active component of the biosensor. The immobilization of the antibodies onto the biosensor system is confirmed by attenuated total reflectance Fourier transform infrared spectroscopy, fluorescent labeling experiments, and refractive interferometric Fourier transform spectroscopy. We show that the immobilized antibodies maintain their immunoactivity and specificity when attached to the sensor surface. Exposure of these nanostructures to the target bacteria results in "direct cell capture" onto the biosensor surface. These specific binding events induce predictable changes in the thin-film optical interference spectrum of the biosensor. Our preliminary studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations. The current detection limit of E. coli K12 bacteria is 10(4) cells/mL within several minutes.

Pub.: 24 Mar '11, Pinned: 17 Nov '17

Rapid label-free identification of mixed bacterial infections by surface plasmon resonance.

Abstract: Early detection of mixed aerobic-anaerobic infection has been a challenge in clinical practice due to the phenotypic changes in complex environments. Surface plasmon resonance (SPR) biosensor is widely used to detect DNA-DNA interaction and offers a sensitive and label-free approach in DNA research.In this study, we developed a single-stranded DNA (ssDNA) amplification technique and modified the traditional SPR detection system for rapid and simultaneous detection of mixed infections of four pathogenic microorganisms (Pseudomonas aeruginosa, Staphylococcus aureus, Clostridium tetani and Clostridium perfringens).We constructed the circulation detection well to increase the sensitivity and the tandem probe arrays to reduce the non-specific hybridization. The use of 16S rDNA universal primers ensured the amplification of four target nucleic acid sequences simultaneously, and further electrophoresis and sequencing confirmed the high efficiency of this amplification method. No significant signals were detected during the single-base mismatch or non-specific probe hybridization (P < 0.05). The calibration curves of amplification products of four bacteria had good linearity from 0.1 nM to 100 nM, with all R(2) values of >0.99. The lowest detection limits were 0.03 nM for P. aeruginosa, 0.02 nM for S. aureus, 0.01 nM for C. tetani and 0.02 nM for C. perfringens. The SPR biosensor had the same detection rate as the traditional culture method (P < 0.05). In addition, the quantification of PCR products can be completed within 15 min, and excellent regeneration greatly reduces the cost for detection.Our method can rapidly and accurately identify the mixed aerobic-anaerobic infection, providing a reliable alternative to bacterial culture for rapid bacteria detection.

Pub.: 09 Jun '11, Pinned: 17 Nov '17

Advancing nanostructured porous si-based optical transducers for label free bacteria detection.

Abstract: Optical label-free porous Si-based biosensors for rapid bacteria detection are introduced. The biosensors are designed to directly capture the target bacteria cells onto their surface with no prior sample processing (such as cell lysis). Two types of nanostructured optical transducers based on oxidized porous Si (PSiO(2)) Fabry-Pérot thin films are synthesized and used to construct the biosensors. In the first system, we graft specific monoclonal antibodies (immunoglobulin G's) onto a neat electrochemically-machined PSiO(2) surface, based on well-established silanization chemistry. The second biosensor class consists of a PSiO(2)/hydrogel hybrid. The hydrogel, polyacrylamide, is synthesized in situ within the nanostructured PSiO(2) host and conjugated with specific monoclonal antibodies to provide the active component of the biosensor. Exposure of these modified-surfaces to the target bacteria results in "direct-cell-capture" onto the biosensor surface. These specific binding events induce predictable changes in the thin-film optical interference spectrum of the biosensor. Our studies demonstrate the applicability of these biosensors for the detection of low bacterial concentrations, in the range of 10(3)-10(5) cell/ml, within minutes. The sensing performance of the two different platforms, in terms of their stability in aqueous media and sensitivity, are compared and discussed. This preliminary study suggests that biosensors based on PSiO(2)/hydrogel hybrid outperform the neat PSiO(2) system.

Pub.: 22 Nov '11, Pinned: 17 Nov '17

RF MEMS-Based Biosensor for Pathogenic Bacteria Detection

Abstract: A biosensor which is used for determining the concentration of substances and other parameters of biological interest is an integral part of the public health systems. Micromachined sensors based on radio frequency–microelectromechanical systems are an emerging field of study for biosensing applications. In this work, we propose a novel detection method for pathogenic bacteria using a coplanar waveguide (CPW) as well as distributed microelectromechanical systems transmission line (DMTL). Escherichia coli has been chosen for the study due to the widespread food poisoning outbreaks caused by its infective strains. But, the model can be easily extended to other pathogenic bacteria as well. The E. coli bacterium was modeled as a three-shell structure based on the electrical properties of the E. coli cell. An initial study was done using a CPW. The scattering parameters and voltage standing wave ratio were analyzed and found to vary as the number of bacteria positioned on the CPW increased. Reflection parameters were found to have more deviation than the transmission parameters. DMTL was designed by introducing periodic structures in CPW, to allow increased interaction between the electromagnetic waves and the measurand. This improved the quality factor of the resonant peaks in reflection coefficient, thereby allowing us to correlate the number of bacteria to the shift in resonant frequency. Selectivity towards E. coli bacteria can be achieved by immobilizing a functionalization layer of anti E. coli antibody on the central conductor of CPW/DMTL. With sufficient calibration, this method can be used to detect and measure the concentration of other pathogenic bacteria as well.

Pub.: 20 Jun '13, Pinned: 17 Nov '17

Optical detection of E. coli bacteria by mesoporous silicon biosensors.

Abstract: A label-free optical biosensor based on a nanostructured porous Si is designed for rapid capture and detection of Escherichia coli K12 bacteria, as a model microorganism. The biosensor relies on direct binding of the target bacteria cells onto its surface, while no pretreatment (e.g. by cell lysis) of the studied sample is required. A mesoporous Si thin film is used as the optical transducer element of the biosensor. Under white light illumination, the porous layer displays well-resolved Fabry-Pérot fringe patterns in its reflectivity spectrum. Applying a fast Fourier transform (FFT) to reflectivity data results in a single peak. Changes in the intensity of the FFT peak are monitored. Thus, target bacteria capture onto the biosensor surface, through antibody-antigen interactions, induces measurable changes in the intensity of the FFT peaks, allowing for a 'real time' observation of bacteria attachment. The mesoporous Si film, fabricated by an electrochemical anodization process, is conjugated with monoclonal antibodies, specific to the target bacteria. The immobilization, immunoactivity and specificity of the antibodies are confirmed by fluorescent labeling experiments. Once the biosensor is exposed to the target bacteria, the cells are directly captured onto the antibody-modified porous Si surface. These specific capturing events result in intensity changes in the thin-film optical interference spectrum of the biosensor. We demonstrate that these biosensors can detect relatively low bacteria concentrations (detection limit of 10(4) cells/ml) in less than an hour.

Pub.: 05 Dec '13, Pinned: 17 Nov '17

Optical biosensors for bacteria detection by a peptidomimetic antimicrobial compound.

Abstract: In this work we present a label-free optical biosensor for rapid bacteria detection using a novel peptide-mimetic compound, as the recognition element. The biosensor design is based on an oxidized porous silicon (PSiO2) nanostructure used as the optical transducer, functionalized with the sequence K-[C12K]7 (referred to as K-7α12), which is a synthetic antimicrobial peptide. This compound is a member of a family of oligomers of acylated lysines (OAKs), mimicking the hydrophobicity and charge of natural antimicrobial peptides. The OAK is tethered to the PSiO2 film and the changes in the reflectivity spectrum are monitored upon exposure to Escherichia coli (E. coli) bacterial suspensions and their lysates. We show that capture of bacterial cell fragments induces predictable changes in the reflectivity spectrum, proportional to E. coli concentrations, thereby enabling rapid, sensitive and reproducible detection of E. coli at concentrations as low as 10(3) cells per mL. While for intact bacterial cells, the K-7α12-tethered PSiO2 shows a poor capturing ability, resulting in an insignificant optical response. The biosensor performance is also studied upon exposure to model Gram positive and negative bacterial lysates, suggesting preferential capture of E. coli cell fragments in the presented scheme. These OAK-based biosensors offer significant advantages in comparison with conventional antibody-based assays, in terms of their simple and cost-effective production, while providing numerous possible sequence combinations for designing new detection schemes.

Pub.: 13 Oct '15, Pinned: 17 Nov '17

Rapid and Visual Detection of Listeria monocytogenes Based on Nanoparticle Cluster Catalyzed Signal Amplification

Abstract: Foodborne pathogens pose a significant threat to human health worldwide. The identification of foodborne pathogens needs to be rapid, accurate and convenient. Here, we constructed a nanoparticle cluster (NPC) catalyzed signal amplification biosensor for foodborne pathogens visual detection. In this work, vancomycin (Van), a glycopeptide antibiotic for Gram-positive bacteria, was used as the first molecular recognition agent to capture Listeria monocytogenes (L. monocytogenes). Fe3O4 NPC modified aptamer, was used as the signal amplification nanoprobe, specifically recognize to the cell wall of L. monocytogenes. As vancomycin and aptamer recognize L. monocytogenes at different sites, the sandwich recognition showed satisfied specificity. Compared to individual Fe3O4 nanoparticle (NP), NPC exhibit collective effect-enhanced catalytic activity for the color reaction of chromogenic substrate. The change in absorbance or color could represent the concentration of target. Using the Fe3O4 NPC-based signal amplification method, L. monocytogenes whole cells could be directly assayed within a linear range of 5.4 × 103 − 108 cfu/mL and a visual limit of detection of 5.4 × 103 cfu/mL. Fe3O4 NPC-based method was more sensitive than the Fe3O4 NP-based method. All these attractive characteristics of highly sensitivity, visual and labor-saving, make the biosensor possess a potential application for foodborne pathogenic bacteria detection.

Pub.: 01 Jun '16, Pinned: 17 Nov '17

Whole-cell detection of live lactobacillus acidophilus on aptamer-decorated porous silicon biosensors

Abstract: This work describes the design of optical aptamer-based porous silicon (PSi) biosensors for the direct capture of Lactobacillus acidophilus. Aptamers are oligonucleotides (single-stranded DNA or RNA) that can bind their targets with high affinity and specificity, making them excellent recognition elements for biosensing applications. Herein, aptamer Hemag1P, which specifically targets the important probiotic L. acidophilus, was utilized for direct bacteria capture onto oxidized PSi Fabry–Pérot thin films. Monitoring changes in the reflectivity spectrum (using reflective interferometric Fourier transform spectroscopy) allows for bacteria detection in a label-free, simple and rapid manner. The performance of the biosensor was optimized by tuning the PSi nanostructure, its optical properties, as well as the immobilization density of the aptamer. We demonstrate the high selectivity and specificity of this simple “direct-capture” biosensing scheme and show its ability to distinguish between live and dead bacteria. The resulting biosensor presents a robust and rapid method for the specific detection of live L. acidophilus at concentrations relevant for probiotic products and as low as 106 cells per mL. Rapid monitoring of probiotic bacteria is crucial for quality, purity and safety control as the use of probiotics in functional foods and pharmaceuticals is becoming increasingly popular.

Pub.: 28 Jun '16, Pinned: 17 Nov '17

Fast and Sensitive Detection of Foodborne Pathogen Using Electrochemical Impedance Analysis, Urease Catalysis and Microfluidics

Abstract: Early screening of pathogenic bacteria is a key to prevent and control of foodborne diseases. In this study, we developed a fast and sensitive bacteria detection method integrating electrochemical impedance analysis, urease catalysis with microfluidics and using Listeria as model. The Listeria cells, the anti-Listeria monoclonal antibodies modified magnetic nanoparticles (MNPs), and the anti-Listeria polyclonal antibodies and urease modified gold nanoparticles (AuNPs) were incubated in a fluidic separation chip with active mixing to form the MNP-Listeria-AuNP-urease sandwich complexes. The complexes were captured in the separation chip by applying a high gradient magnetic field, and the urea was injected to resuspend the complexes and hydrolyzed under the catalysis of the urease on the complexes into ammonium ions and carbonate ions, which were transported into a microfluidic detection chip with an interdigitated microelectrode for impedance measurement to determine the amount of the Listeria cells. The capture efficiency of the Listeria cells in the separation chip was ∼93% with a shorter time of 30 min due to the faster immuno-reaction using the active magnetic mixing. The changes on both impedance magnitude and phase angle were demonstrated to be able to detect the Listeria cells as low as 1.6 × 102 CFU/mL. The detection time was reduced from original ∼2 h to current ∼1 h. The recoveries of the spiked lettuce samples ranged from 82.1% to 89.6%, indicating the applicability of this proposed biosensor. This microfluidic impedance biosensor has shown the potential for online, automatic and sensitive bacteria separation and detection.

Pub.: 22 Jul '16, Pinned: 17 Nov '17

Graphene-interfaced electrical biosensor for label-free and sensitive detection of foodborne pathogenic E. coli O157:H7

Abstract: E. coli O157:H7 is an enterohemorrhagic bacteria responsible for serious foodborne outbreaks that causes diarrhoea, fever and vomiting in humans. Recent foodborne E. coli outbreaks has left a serious concern to public health. Therefore, there is an increasing demand for a simple, rapid and sensitive method for pathogen detection in contaminated foods. In this study, we developed a label-free electrical biosensor interfaced with graphene for sensitive detection of pathogenic bacteria. This biosensor was fabricated by interfacing graphene with interdigitated microelectrodes of capacitors that were biofunctionalized with E. coli O157:H7 specific antibodies for sensitive pathogenic bacteria detection. Here, graphene nanostructures on the sensor surface provided superior chemical properties such as high carrier mobility and biocompatibility with antibodies and bacteria. The sensors transduced the signal based on changes in dielectric properties (capacitance) through (i) polarization of captured cell-surface charges, (ii) cells’ internal bioactivity, (iii) cell-wall's electronegativity or dipole moment and their relaxation and (iv) charge carrier mobility of graphene that modulated the electrical properties once the pathogenic E. coli O157:H7 captured on the sensor surface. Sensitive capacitance changes thus observed with graphene based capacitors were specific to E. coli O157:H7 strain with a sensitivity as low as 10 to 100 cells/ml. The proposed graphene based electrical biosensor provided advantages of speed, sensitivity, specificity and in-situ bacterial detection with no chemical mediators, represents a versatile approach for detection of a wide variety of other pathogens.

Pub.: 16 Dec '16, Pinned: 17 Nov '17

Detection of parathyroid hormone-like hormone in cancer cell cultures by gold nanoparticle-based lateral flow immunoassays.

Abstract: Parathyroid hormone-like hormone (PTHLH) exerts relevant roles in progression and dissemination of several tumors. However, factors influencing its production and secretion have not been fully characterized. The main limitation is the lack of specific, sensitive and widely available techniques to detect and quantify PTHLH. We have developed a lateral flow immunoassay using gold nanoparticles label for the fast and easy detection of PTHLH in lysates and culture media of three human cell lines (HaCaT, LA-N-1, SK-N-AS). Levels in culture media and lysates ranged from 11 to 20ng/mL and 0.66 to 0.87μg/mL respectively. Results for HaCaT are in agreement to the previously reported, whereas LA-N-1 and SK-N-AS have been evaluated for the first time. The system also exhibits good performance in human serum samples. This methodology represents a helpful tool for future in vitro and in vivo studies of mechanisms involved in PTHLH production as well as for diagnostics.Parathyroid Hormone-like Hormone (PTHLH) is known to be secreted by some tumors. However, the detection of this peptide remains difficult. The authors here described their technique of using gold nanoparticles as label for the detection of PTHLH by Lateral-flow immunoassays (LFIAs). The positive results may also point a way to using the same technique for the rapid determination of other relevant cancer proteins.

Pub.: 24 Oct '15, Pinned: 17 Nov '17

The effects of size and synthesis methods of gold nanoparticle-conjugated MαHIgG4 for use in an immunochromatographic strip test to detect brugian filariasis.

Abstract: This study describes the properties of colloidal gold nanoparticles (AuNPs) with sizes of 20, 30 and 40 nm, which were synthesized using citrate reduction or seeding-growth methods. Likewise, the conjugation of these AuNPs to mouse anti-human IgG(4) (MαHIgG(4)) was evaluated for an immunochromatographic (ICG) strip test to detect brugian filariasis. The morphology of the AuNPs was studied based on the degree of ellipticity (G) of the transmission electron microscopy images. The AuNPs produced using the seeding-growth method showed lower ellipticity (G ≤ 1.11) as compared with the AuNPs synthesized using the citrate reduction method (G ≤ 1.18). Zetasizer analysis showed that the AuNPs that were synthesized using the seeding-growth method were almost monodispersed with a lower polydispersity index (PDI; PDI≤0.079), as compared with the AuNPs synthesized using the citrate reduction method (PDI≤0.177). UV-visible spectroscopic analysis showed a red-shift of the absorbance spectra after the reaction with MαHIgG(4), which indicated that the AuNPs were successfully conjugated. The optimum concentration of the BmR1 recombinant antigen that was immobilized on the surface of the ICG strip on the test line was 1.0 mg ml(-1). When used with the ICG test strip assay and brugian filariasis serum samples, the conjugated AuNPs-MαHIgG(4) synthesized using the seeding-growth method had faster detection times, as compared with the AuNPs synthesized using the citrate reduction method. The 30 nm AuNPs-MαHIgG(4), with an optical density of 4 from the seeding-growth method, demonstrated the best performance for labelling ICG strips because it displayed the best sensitivity and the highest specificity when tested with serum samples from brugian filariasis patients and controls.

Pub.: 21 Nov '12, Pinned: 12 Oct '17

Paper-Based Magnetic Nanoparticle-peptide probe for Rapid and Quantitative Colorimetric Detection of Escherichia coli O157:H7

Abstract: There is a critical and urgent demand for a simple, rapid and specific qualitative and quantitative colorimetric biosensor for the detection of the food contaminant Escherichia coli O157:H7 (E. coli O157:H7) in complex food products due to the recent outbreaks of food-borne diseases. Traditional detection techniques are time-consuming, require expensive instrumentation and are labour-intensive. To overcome these limitations, a novel, ultra-rapid visual biosensor was developed based on the ability of E. coli O157:H7 proteases to change the optical response of a surface-modified, magnetic nanoparticle-specific (MNP-specific) peptide probe. Upon proteolysis, a gradual increase in the golden color of the sensor surface was visually observed. The intensification of color was correlated with the E. coli O157:H7 concentration. The color change resulting from the dissociation of the self-assembled monolayer (SAM) was detected by the naked eye and analysed using an image analysis software (ImageJ) for the purpose of quantitative detection. This biosensor demonstrated high sensitivity and applicability, with lower limits of detection of 12 CFU mL−1 in broth samples and 30–300 CFU mL−1 in spiked complex food matrices. In conclusion, this approach permits the use of a disposable biosensor chip that can be mass-produced at low cost and can be used not only by food manufacturers but also by regulatory agencies for better control of potential health risks associated with the consumption of contaminated foods.

Pub.: 10 Oct '16, Pinned: 12 Oct '17