•Novel carbon nanotube/gold nanoparticles nanocomposite probe based point-of-care diagnosis device.•Visual carcinoembryonic antigen detection.•The nanocomposite probe shows higher sensitivity comparing with carbon nanotubes or gold nanoparticles probe.This paper describes a low-cost, sensitive, visual and rapid immunochromatographic assay method on cotton thread for carcinoembryonic antigen (CEA) detection by using novel carbon nanotube/gold nanoparticles (CNT/GNPs) nanocomposite reporter probe. CEA, a lung cancer protein biomarker, was used as analyte to demonstrate the principle of the immunochromatographic assay on cotton thread biosensor. In the presence of target CEA, the decreasing aggregation amount of CNT/GNPs nanocomposite reporter probes on the test zone induced directly readout by naked eye. Meanwhile, quantitative detection could be performed conveniently with a commercial available scanner. The performance with respect to sensitivity of the method was greatly improved by 2–3 magnitudes comparing with traditional gold nanoparticles (GNPs) or carbon nanotubes (CNTs) as reporter probe. Under optimal conditions, the biosensor was capable of detecting 2.32 ng/mL CEA (S/N ≥ 3) which is sensitive enough for clinical diagnosis. These results indicated the novel CNT/GNPs nanocomposite reporter probe based immunochromatographic assay on cotton thread is particularly suitable for point-of-care (POC) diagnostics in resource-limited regions.Download high-res image (201KB)Download full-size image

•Novel gold nanoparticle trimer reporter probe.•Natural cotton thread dry-reagent device.•Simple preparation, low cost, rapid detection, easy to handle.We reported here for the first time on the use of cotton thread combined with novel gold nanoparticle trimer reporter probe for low-cost, sensitive and rapid detection of a lung cancer related biomarker, human ferritin. A model system comprising ferritin as an analyte and a pair of monoclonal antibodies was used to demonstrate the proof-of-concept on the dry-reagent natural cotton thread immunoassay device. Results indicated that the using of novel gold nanoparticle trimer reporter probe greatly improved the sensitivity comparing with traditional gold nanoparticle reporter probe on the cotton thread immunoassay device. The assay avoids multiple incubation and washing steps performed in most conventional protein analyses. Although qualitative tests are realized by observing the color change of the test zone, quantitative data are obtained by recording the optical responses of the test zone with a commercial scanner and corresponding analysis software. Under optimal conditions, the cotton thread immunoassay device was capable of measuring 10 ng/mL human ferritin under room temperature which is sensitive enough for clinical diagnosis. Moreover, the sample solution employed in the assays is just 8 μL, which is much less than traditional lateral flow strip based biosensors.

•Natural cotton thread-based point-of-care diagnosis devices.•A room temperature nucleic acid detection method.•A novel molecular beacon technique based on poly adenosine and coralyne interaction.•The test device is capable of discrimination single base mismatched sequences.•Simple preparation, low cost, rapid detection, easy to handle.We used cotton thread as substrate to develop a novel room temperature DNA detection device for low-cost, sensitive and rapid detection of a human genetic disease, hereditary tyrosinemia type I related DNA sequences. A novel adenosine based molecular beacon (ABMB) probe modified on gold nanoparticle was used as reporter probe. In the presence of coralyne, a small molecule which can react with adenosines, the ABMB would form a hairpin structure just like traditional molecular beacon used extensively. In the presence of target DNA sequences, the hairpin structure of ABMB modified on gold nanoparticles will be opened and the biotin group modified at one end of the DNA probes will be released and react with the streptavidin immobilized on the test zone of the cotton thread. The response of the thread based DNA test device is linear over the range of 2.5–100 nM complementary DNA. The ability of our developed device for discriminating the single base mismatched DNA related to a human genetic disease, hereditary tyrosinemia type I, was improved comparing with previous report. It is worth mentioning that the whole assay procedure for DNA test is performed under room temperature which simplified the assay procedures greatly.

•Natural cotton thread-based point-of-care diagnosis devices.•Simple preparation, low cost, rapid detection, and easy to handle.•An enhancement protocol was employed by using two kinds of gold nanoparticle labels for protein test.•The DNA test device has ability to visual discrimination of single base mismatched DNA sequence.We report here for the first time by using dry-reagent cotton thread-based point-of-care diagnosis devices for low-cost, sensitive and rapid detection of a lung cancer related biomarker, squamous cell carcinoma antigen (SCCA) and a human genetic disease, hereditary tyrosinemia type I related DNA sequences. A model system comprising SCCA as an analyte and a pair of monoclonal antibodies is used to demonstrate the proof-of-concept on the dry-reagent cotton thread based immunoassay device. An enhancement protocol was employed by using two kinds of gold nanoparticle labels for SCCA test which greatly improved the sensitivity of the device. The assay avoids the multiple incubation and washing steps performed in most conventional protein analyses, which is similar with the lateral flow strip technology. Under optimal conditions, the thread based immunoassay device was capable of measuring 1 ng/mL SCCA in 20 min which meet the requirement for clinical diagnosis. DNA detection was successfully realized by using a novel adenosine based molecular beacon probe as reporter probes in the cotton thread based device, the linear range is 75–3000 fmol which is suitable for quantitative test.

•A quantitative lateral flow nucleic acid biosensor based on blue dye doped latex bead labels.•The lateral flow strip biosensor is capable of detecting target DNA spiked in large quantity of plasma directly.•The strip biosensor shows promising for improving detection sensitivity comparing with natural dye based strip biosensors.In the manuscript, a quantitative lateral flow nucleic acid biosensor (Lateral flow nucleic acid biosensor, LFNB) based on blue dye doped latex beads was proposed and its feasibility for detecting deoxyribonucleic acid (DNA) in plasma was investigated. A 60-mer DNA sequence (T1) was selected as model to demonstrate the protocol. Blue dyes doped latex bead bearing DNA probe would be captured on the corresponding test line in the presence of target DNA, to form an evident blue band. Although qualitative tests are realized by observing the color change of the test zone, quantitative data are obtained by recording the optical responses of the test zone with a portable “Strip Reader” instrument conveniently. The strip has been applied for the detection of synthesized DNA sample in human plasma sample with a detection limit of 3.75 fmol. Interference was not evident even the target DNA was spiked with 50 μL plasma which indicated the well shielding of the latex bead reporters and quantified chromatographic separations of unwanted materials of the strip comparing with traditional gold nanoparticle based LFNB platforms.

A rapid quantitative immunochromatographic strip (IS) for simultaneous detection of multiple proteins was described. Rabbit IgG (R-IgG) and human IgM (H-IgM) were used as model protein targets for demonstration of the proof of concepts. Gold nanoparticles (Au-NP) were used as tags to label the anti-R-IgG and anti-H-IgM antibodies to form two kinds of gold nanoparticle-antibody conjugates, respectively. The mixture of above conjugates was dispensed on the conjugate pad of IS. Capture antibodies of IgG and IgM were dispensed in the different locations of nitrocellulose membrane of the IS to form two test zones. The multiplex immunoassay was performed by simply applying the sample solution on the IS, waiting for several minutes, two red bands at the test zones can be easily discriminated with eyes. For quantitative test, the captured Au-NP tags on the test zones were quantified with a portable strip reader by recording the intensities of the resulting red bands at the test zones. The detection limits were estimated to be 0.5 and 2.5 ng/ml for R-IgG and H-IgM, respectively, in association with a 7-min immunoassay time.

In this study, a natural cotton thread immunoassay device combined with gold nanorod (GNR) reporter probe is developed for the rapid, sensitive and quantitative electrochemical determination of human ferritin, a lung cancer related biomarker. Human ferritin as an analyte and a pair of monoclonal antibodies are used to demonstrate the proof-of-concept on the cotton thread immunoassay device. An enhancement of the sensitivity is achieved by using gold nanorod as an electroactive report probe compared with a traditional gold nanoparticle (GNP) report probe. The device was capable of measuring 1.58 ng/mL ferritin in 30 min by anodic stripping voltammetry (ASV) testing, which meet the requirement for clinical diagnosis.An electrochemical immunoassay strategy was developed using a natural cotton thread immunoassay device combined with gold nanorod reporter probe. Quantitative detection can be realized by anodic stripping voltammetry (ASV) testing of the dissolved gold ions (III) after oxidative treatment to release the pre-immobilized complex of the purple band test zone by the HBr-Br2 solution.