Sensitive colorimetric detection of Listeria monocytogenes based on isothermal gene amplification and unmodified gold nanoparticles

Gold nanoparticles as colorimetric probes in food analysis: Progress and challenges

The rapid, sensitive and reliable food safety control is urgently needed due to the harmful effects of the food contaminants on human health. Colorimetric approach has exhibited promising potential for the detection of food contaminants due to their easy preparation, rapid detection, high sensitivity, and naked-eye sensing. In recent years, AuNPs-based colorimetric probes have been extensively explored for food analysis. The present article reviews the development of AuNPs-based colorimetric probes for colorimetric sensing and their applications in food analysis. It generally summarizes the properties of AuNPs and introduces the preparation and functionalization methods of AuNPs. An overview of the colorimetric sensing mechanisms of AuNPs-based probes and their applications in analysis of food contaminants are also provided. Although AuNPs-based colorimetric probes show many advantages in detection of food contaminants, challenges remain in terms of complexity of food matrices, multiple analytes detection in a single go, and testing conditions interference.

Recent advances in biological detection with rolling circle amplification: design strategy, biosensing mechanism, and practical applications

Rolling circle amplification (RCA) is a simple and isothermal DNA amplification technique that is used to generate thousands of repeating DNA sequences using circular templates under the catalysis of DNA polymerase.

The Modulatory Activity of Tryptophan Displaying Nanodevices on Macrophage Activation for Preventing Acute Lung Injury

Macrophages play an important role in the initiation, progression and resolution of inflammation in many human diseases. Effective regulation of their activation and immune responses could be a promising therapeutic strategy to manage various inflammatory conditions. Nanodevices that naturally target macrophages are ideal agents to regulate immune responses of macrophages. Here we described a special tryptophan (Trp)-containing hexapeptide-coated gold nanoparticle hybrid, PW, which had unique immunomodulatory activities on macrophages. The Trp residues enabled PW higher affinity to cell membranes, and contributed to inducing mild pro-inflammatory responses of NF-κB/AP-1 activation. However, in the presence of TLR stimuli, PW exhibited potent anti-inflammatory activities through inhibiting multiple TLR signaling pathways. Mechanistically, PW was internalized primarily through micropinocytosis pathway into macrophages and attenuated the endosomal acidification process, and hence preferentially affected the endosomal TLR signaling. Interestingly, PW could induce the expression of the TLR negative regulator IRAK-M, which may also contribute to the observed TLR inhibitory activities. In two acute lung injury (ALI) mouse models, PW could effectively ameliorate lung inflammation and protect lung from injuries. This work demonstrated that nanodevices with thoughtful design could serve as novel immunomodulatory agents to manage the dysregulated inflammatory responses for treating many chronic and acute inflammatory conditions, such as ALI.

Detection of ferrous ion by etching-based multi-colorimetric sensing of gold nanobipyramids

Colorimetric sensing methods based on non-spherically symmetric gold (Au) nanoparticles have become a powerful tool in the field of biomedical detection due to their intriguing plasmonic properties. In this study, Au nanobipyramids (Au NBPs) were used as colorimetric sensing probes to detect ferrous ions (Fe²⁺) through tip etching. The quick etching of Au NBPs along the longitudinal direction by superoxide radicals generated by the reaction of Fe²⁺ and H₂O₂ led local surface plasmon resonance (LSPR) to blue shift and produced vivid color change that could be used for visual inspection. Under the optimal reaction conditions, the peak shift of the Au NBPs and the logarithm of the concentrations of Fe²⁺ had a linear relationship in the range of 10 nM to 10 μM, with a very low detection limit of 1.29 nM. During the etching process, a different end shape of the Au nanoparticles results in a different process for the morphology transition, which makes the degree of spectral change and detection sensitivity significantly different. In the presence of trace amounts of Fe²⁺ (<1000 nM), the detection sensitivity of Au NBPs with sharp ends which rely on aspect ratio and truncation is nine times higher than that of gold nanorods with round ends which only rely on aspect ratio. Although the color change of larger-sized Au NBPs was not clear during detection, the LSPR peak shift was more severe. Therefore, the system provides different modes for detecting Fe²⁺ according to Au NBPs with different sizes and characteristics.

Recent Advances in Electrochemiluminescence Sensors for Pathogenic Bacteria Detection

Pathogenic bacterial contamination greatly threats human health and safety. Rapidly biosensing pathogens in the early stage of infection would be helpful to choose the correct drug treatment, prevent transmission of pathogens, as well as decrease mortality and economic losses. Traditional techniques, such as polymerase chain reaction and enzyme-linked immunosorbent assay, are accurate and effective, but are greatly limited because they are complex and time-consuming. Electrochemiluminescence (ECL) biosensors combine the advantages of both electrochemical and photoluminescence analysis and are suitable for high sensitivity and simple pathogenic bacteria detection. In this review, we summarize recent advances in ECL sensors for pathogenic bacteria detection and highlight the development of paper-based ECL platforms in point of care diagnosis of pathogens.

Dual-Wavelength Ratiometric Electrochemiluminescence Immunosensor for Cardiac Troponin I Detection

Ratiometric electrochemiluminescence (ECL) has attracted special focus in the biological analysis field, because it could eliminate the environmental interference and allow for precise measurement. Herein, a dual-wavelength ratiometric ECL biosensor was designed for the detection of cardiac troponin I (cTnI), where (4,4'-dicarboxylic acid-2,2'-bipyridyl) ruthenium(II) (Ru(dcbpy)₃²⁺) and Au nanoparticle-loaded graphene oxide/polyethylenimine (GPRu-Au) nanomaterial acts as an acceptor, and Au nanoparticle-modified graphitic phase carbon nitride nanosheet composite (Au-CNN) acts as donor. Au-CNN shows a high and steady ECL signal centered at 455 nm, which is well-matched with the adsorption of GPRu-Au; thereby, a highly efficient electrochemiluminescent resonance energy transfer (ECL-RET) sensing platform is designed. AuNPs facilitate the immobilization of antibody on the nanomaterials through a Au-N bond. The high surface area of graphene oxide/polyethylenimine allows a large number of Ru(dcbpy)₃²⁺ to be loaded, immensely amplifying the ECL signal. This sensing platform exhibits outstanding analytical performance toward cTnI with a detection limit of 3.94 fg/mL (S/N = 3). The high reliability, selectivity, and sensitivity of this ratiometric ECL biosensor provides a versatile sensing platform for the bioanalysis.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Highly selective and sensitive detection of Staphylococcus aureus with gold nanoparticle-based core-shell nano biosensor

Staphylococcus aureus is a gram-positive and opportunistic pathogen that is one of the most common causes of nosocomial infections; therefore, its rapid diagnosis is important and valuable. Today, the use of nanoparticles is expanding due to their unique properties. The purpose of the present study is the determination of S. aureus by a colorimetric method based on gold nanoparticles (AuNPs). Firstly, S. aureus was cultured on both LB media (broth and agar) and their chromosomal DNA was extracted. Afterwards, primers and biosensor were designed based on Protein A sequence data in the gene bank. PCR assay was performed under optimal conditions and the PCR product was electrophoresed on 2-percent agarose gel. The synthesized biosensors were conjugated with AuNPs and, eventually, a single-stranded genome was added to the conjugated AuNPs and hybridization was performed. The results were evaluated based on color change detected by the naked eye, optical spectrophotometry, and transient electron microscopy. Finally, the sensitivity and specificity of the AuNP-biosensor were determined. The results of the present study showed a 390 bp band on the agarose electrophoresis gel, which confirmed the presence of Protein A genes on the chromosome of the bacteria. The PCR and colorimetric methods were compared with each other. The sensitivity of the PCR and colorimetric methods were 30 ng μL^-1 and 10 ng μL^-1, respectively. The limit of detection (LOD) equaling 8.73 ng μL^-1 was determined and the specificity of the method was confirmed by the DNA of other bacteria. According to the results, the present method is rapid and sensitive in detecting S. aureus.

Thiol-Capped Gold Nanoparticle Biosensors for Rapid and Sensitive Visual Colorimetric Detection of Klebsiella pneumoniae

In the last few years, gold nanoparticle biosensors have been developed for rapid, precise, easy and inexpensive with high specificity and sensitivity detection of human, plant and animal pathogens. Klebsiella pneumoniae serotype K2 is one of the common gram-negative pathogens with high prevalence. Therefore, it is essential to provide the effective and exclusive method to detect the bacteria. Klebsiella pneumoniae serotype K2 strain ATCC9997 genomic DNA was applied to establish the detection protocol either with thiol-capped oligonucleotide probes and gold nanoparticles or polymerase chain reaction based on K2A gene sequence. In the presence of the genomic DNA and oligonucleotide probes, a change in the color of gold nanoparticles and maximum changes in wavelength at 550-650 nm was achieved. In addition, the result showed specificity of 15 × 10⁵ CFU/mL and 9 pg/μL by gold nanoparticles probes. The lower limit of detection obtained by PCR method was 1 pg/μL. Moreover, results demonstrated a great specificity of the designed primers and probes for colorimetric detection assay and PCR. Colorimetric detection using gold nanoparticle probe with advantages such as the lower time required for detection and no need for expensive detection instrumentation compared to the biochemical and molecular methods could be introduced for rapid, accurate detection of the bacteria.

Spectrophotometric, colorimetric and visually detection of Pseudomonas aeruginosa ETA gene based gold nanoparticles DNA probe and endonuclease enzyme

Colorimetric DNA detection is preferred over other methods for clinical molecular diagnosis because it does not require expensive equipment. In the present study, the colorimetric method based on gold nanoparticles (GNPs) and endonuclease enzyme was used for the detection of P. aeruginosa ETA gene. Firstly, the primers and probe for P. aeruginosa exotoxin A (ETA) gene were designed and checked for specificity by the PCR method. Then, GNPs were synthesized using the citrate reduction method and conjugated with the prepared probe to develop the new nano-biosensor. Next, the extracted target DNA of the bacteria was added to GNP-probe complex to check its efficacy for P. aeruginosa ETA gene diagnosis. A decrease in absorbance was seen when GNP-probe-target DNA cleaved into the small fragments of BamHI endonuclease due to the weakened electrostatic interaction between GNPs and the shortened DNA. The right shift of the absorbance peak from 530 to 562nm occurred after adding the endonuclease. It was measured using a UV-VIS absorption spectroscopy that indicates the existence of the P. aeruginosa ETA gene. Sensitivity was determined in the presence of different concentrations of target DNA of P. aeruginosa. The results obtained from the optimized conditions showed that the absorbance value has linear correlation with concentration of target DNA (R: 0.9850) in the range of 10-50ngmL-1 with the limit detection of 9.899ngmL-1. Thus, the specificity of the new method for detection of P. aeruginosa was established in comparison with other bacteria. Additionally, the designed assay was quantitatively applied to detect the P. aeruginosa ETA gene from 103 to 108CFUmL-1 in real samples with a detection limit of 320CFUmL-1.

Green synthesis of bioactive polysaccharide-capped gold nanoparticles for lymph node CT imaging

The development of biologically targeted contrast agents for X-ray computed tomography (CT) imaging remains a major challenge. Here, we investigated a green chemistry-based synthesis of lymph node-targeted mannan-capped gold nanoparticles (M-GNPs) as a CT contrast agent. In this study, mannan was used as a reducing and stabilizing agent for gold nanoparticles (AuNPs). M-GNPs were readily internalized by antigen-presenting cells (APCs) through mannose receptors-mediated endocytosis. The M-GNPs, which had a spherical morphology, had an average diameter of 9.18±0.71nm and surface plasmon resonance (SPR) absorption spectra with maximal absorption at 522nm. The M-GNPs displayed a concentration-based X-ray attenuation property with a maximum Hounsfield unit (HU) value of 303.2±10.83. The local administration of M-GNPs led to significantly enhanced X-ray contrast for the imaging of popliteal lymph nodes. These findings demonstrated that M-GNPs can be used as biologically targeted contrast agents for CT imaging.

Visual detection of Brucella in bovine biological samples using DNA-activated gold nanoparticles

Brucellosis is a bacterial disease, which, although affecting cattle primarily, has been associated with human infections, making its detection an important challenge. The existing gold standard diagnosis relies on the culture of bacteria which is a lengthy and costly process, taking up to 45 days. New technologies based on molecular diagnosis have been proposed, either through dip-stick, immunological assays, which have limited specificity, or using nucleic acid tests, which enable to identify the pathogen, but are impractical for use in the field, where most of the reservoir cases are located. Here we demonstrate a new test based on hybridization assays with metal nanoparticles, which, upon detection of a specific pathogen-derived DNA sequence, yield a visual colour change. We characterise the components used in the assay with a range of analytical techniques and show sensitivities down to 1000 cfu/ml for the detection of Brucella. Finally, we demonstrate that the assay works in a range of bovine samples including semen, milk and urine, opening up the potential for its use in the field, in low-resource settings.

Development of a gold nanoparticle-based universal oligonucleotide microarray for multiplex and low-cost detection of foodborne pathogens

Bacterial foodborne diseases remain major threats to food safety and public health, especially in developing countries. In this study a novel assay, combining gold nanoparticle (GNP)-based multiplex oligonucleotide ligation-PCR and universal oligonucleotide microarray technology, was developed for inexpensive, specific, sensitive, and multiplex detection of eight common foodborne pathogens, including Shigella spp., Campylobacter jejuni, Bacillus cereus, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica, Staphylococcus aureus, and Vibrio parahaemolyticus. The target fragments of the eight pathogens were enriched by multiplex PCR and subjected to multiplex ligase detection reaction. Ligation products were enriched and labeled with GNPs by universal asymmetric PCR, using excess GNP-conjugated primers. The labeled single-stranded amplicons containing complementary tag sequences were captured by the corresponding tag sequences immobilized on microarrays, followed by silver staining for signal enhancement. Black images of microarray spots were visualized by naked eyes or scanned on a simple flatbed scanner, and quantified. The results indicated that this assay could unambiguously discriminate all eight pathogens in single and multiple infections, with detection sensitivity of 3.3-85CFU/mL for pure cultures. Microarray results of ninety-five artificially contaminated and retail food samples were consistent with traditional culture, biochemical and real-time PCR findings. Therefore, the novel assay has the potential to be used for routine detection due to rapidity, low cost, and high specificity and sensitivity.

Gold Nanoparticles of Diameter 13 nm Induce Apoptosis in Rabbit Articular Chondrocytes

Gold nanoparticles (AuNPs) have been widely used in biomedical science including antiarthritic agents, drug loading, and photothermal therapy. In this report, we studied the effects of AuNPs with diameters of 3, 13, and 45 nm, respectively, on rabbit articular chondrocytes. AuNPs were capped with citrate and their diameter and zeta potential were measured by dynamic light scattering (DLS). Cell viability was evaluated by Cell Counting Kit-8 (CCK-8) assay after the rabbit articular chondrocytes were pre-incubated with 3, 13, and 45 nm AuNPs, respectively, for 24 h. Flow cytometry (FCM) analysis with annexin V/propidium iodide (PI) double staining and fluorescence imaging with Hoechst 33258 staining were used to determine the fashion of AuNPs-induced chondrocyte death. Further, 13 nm AuNPs (2 nM) significantly induced chondrocyte death accompanying apoptotic characteristics including mitochondrial damage, externalization of phosphatidylserine and nuclear concentration. However, 3 nm AuNPs (2 nM) and 45 nm (0.02 nM) AuNPs did not induce cytotoxicity in chondrocytes. Although 13 nm AuNPs (2 nM) increased the intracellular reactive oxygen species (ROS) level, pretreatment with Nacetyl cysteine (NAC), a ROS scavenger, did not prevent the cytotoxicity induced by 13 nm AuNPs, indicating that 13 nm AuNPs (2 nM) induced ROS-independent apoptosis in chondrocytes. These results demonstrate the size-dependent cytotoxicity of AuNPs in chondrocytes, which must be seriously considered when using AuNPs for treatment of osteoarthritis (OA).

Rolling circle amplification as isothermal gene amplification in molecular diagnostics

Rolling circle amplification (RCA) developed in the mid-1990s has been widely used as an efficient isothermal DNA amplification process for molecular diagnosis. This enzymatic process amplifies target DNA sequences with high fidelity and specificity by using the strand displacing DNA polymerases. The product of RCA is long single-stranded DNA that contains tandem repeat of target sequence. Isothermal reaction amplification condition of RCA has an advantage over conventional polymerase chain reaction, because no temperature cycling devices are needed for RCA. Thus, RCA is suitable tool for point-of-care detection of target nucleic acids as well as facile detection of target genes. Combined with various detection methods, RCA could amplify and detect femtomolar scale of target nucleic acids with a specificity of one or two base discrimination. Herein, RCA technology is reviewed with an emphasis on molecular diagnosis of microRNAs, infectious pathogens, and point mutations.

An enzyme-free colorimetric assay using hybridization chain reaction amplification and split aptamers

A novel unmodified gold nanoparticle (AuNP)-based colorimetric assay was demonstrated using split aptamers and the hybridization chain reaction (HCR) amplification strategy. Here, the aptamer was divided into a structure-switching hairpin probe (DNA probe H1 (or H1')) and a single-stranded probe (DNA probe H2 (or H2')). In the presence of the target, DNA probe H1 (or H1') could specifically capture the target with the assistance of DNA probe H2 (or H2') to form a stable complex. Subsequently, the hairpin structure of DNA probe H1 (or H1') was changed, and then a chain reaction of hybridization events between two other hairpin probes (H3 and H4) propagated, resulting in the formation of nicked double-helices. Since it was difficult for such nicked double-helices to inhibit salt-induced AuNP aggregation, a red-to-blue color change was observed. With the elegant amplification effect of HCR, this assay showed a low detection limit (15 nM for Hg(2+) and 1 μM for adenosine), which was lower than or at least comparable to previous AuNP-based methods. The novel strategy not only eliminated the requirements of enzymatic reactions, separation processes, chemical modifications, and sophisticated instruments, but also could be used for other targets only by simply changing the DNA probe sequences.

Phosphorylation-regulated crosslinking of gold nanoparticles: a new strategy for colorimetric detection of protein kinase activity

Accurate and rapid detection of protein kinase activities is of great significance because protein kinases play important regulatory roles in many vital biological processes. Herein, we wish to report a facile colorimetric protein kinase assay based on the phosphorylation-tuned crosslinking of gold nanoparticles (GNPs) by using protein kinase A (PKA) as a proof-of-concept target. In this new strategy, a biotinylated peptide (biotin-LRRASLG) is used as the PKA-specific substrate. When mixed with streptavidin-functionalized GNPs (STV-GNPs), the positively charged biotin-peptide will combine with different GNPs both through the specific STV-biotin binding and through electrostatic interactions, which will lead to the crosslinking and coagulation of GNPs. In contrast, under the catalysis of PKA, the biotin-peptide will be phosphorylated at the serine residue and its net charge will be obviously altered, which may significantly weaken the electrostatic interaction between the phosphopeptide and GNPs and thus effectively prevent the STV-GNPs from crosslinking and settlement. Therefore, by viewing the color changes of the GNPs, the PKA activity can be easily detected by the naked eye.

Magnetic Bead/Gold Nanoparticle Double-Labeled Primers for Electrochemical Detection of Isothermal Amplified Leishmania DNA

A novel methodology for the isothermal amplification of Leishmania DNA using labeled primers combined with the advantages of magnetic purification/preconcentration and the use of gold nanoparticle (AuNP) tags for the sensitive electrochemical detection of such amplified DNA is developed. Primers labeled with AuNPs and magnetic beads (MBs) are used for the first time for the isothermal amplification reaction, being the amplified product ready for the electrochemical detection. The electrocatalytic activity of the AuNP tags toward the hydrogen evolution reaction allows the rapid quantification of the DNA on screen-printed carbon electrodes. Amplified products from the blood of dogs with Leishmania (positive samples) are discriminated from those of healthy dogs (blank samples). Quantitative studies demonstrate that the optimized method allows us to detect less than one parasite per microliter of blood (8 × 10(-3) parasites in the isothermal amplification reaction). This pioneering approach is much more sensitive than traditional methods based on real-time polymerase chain reaction (PCR), and is also more rapid, cheap, and user-friendly.

Scalable DNA-Based Magnetic Nanoparticle Agglutination Assay for Bacterial Detection in Patient Samples

We demonstrate a nanoparticle-based assay for the detection of bacteria causing urinary tract infections in patient samples with a total assay time of 4 h. This time is significantly shorter than the current gold standard, plate culture, which can take several days depending on the pathogen. The assay is based on padlock probe recognition followed by two cycles of rolling circle amplification (RCA) to form DNA coils corresponding to the target bacterial DNA. The readout of the RCA products is based on optomagnetic measurements of the specific agglutination of DNA-bound magnetic nanoparticles (MNPs) using low-cost optoelectronic components from Blu-ray drives. We implement a detection approach, which relies on the monomerization of the RCA products, the use of the monomers to link and agglutinate two populations of MNPs functionalized with universal nontarget specific detection probes and on the introduction of a magnetic incubation scheme. This enables multiplex detection of Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosa at clinically relevant concentrations, demonstrating a factor of 30 improvement in sensitivity compared to previous MNP-based detection schemes. Thanks to the universal probes, the same set of functionalized MNPs can be used to read out products from a multitude of RCA targets, making the approach truly scalable for parallel detection of multiple bacteria in a future integrated point of care molecular diagnostics system.

Multiplex detection and genotyping of pathogenic bacteria on paper-based biosensor with a novel universal primer mediated asymmetric PCR

Traditionary multiplex asymmetric polymerase chain reaction (PCR) can be applied to detect multiplex target organisms simultaneously, but complex optimizations of primer concentrations and staggered additions of primers are required to achieve equal amplification of multiplex genes. To overcome this shortcoming, we propose a novel method based on multiplex asymmetric PCR and paper-based nucleic acid diagnostics (PBNAD). In the asymmetric PCR, a universal primer was introduced to break the bottlenecks of low sensitivity and self-inhibition among different sets of primers. Amplification using the novel multiplex asymmetric PCR boosted the quantity of single-stranded amplicons, and the amplified products contained the same sequence at the 5' end. Therefore, only one gold nanoparticle-based signal probe was needed for the simultaneous detection of three genes using the PBNAD platform, and the detection signals could be observed with the naked eye. With this highly efficient, novel multiplex asymmetric PCR, as little as 1 pg/μL genomic DNA can be detected. This method can also be applied to genotyping for reliable epidemiological investigations. This proof-of-concept study highlights the potential of the PBNAD platform for cost- and labor-effective applications in the detection of pathogenic bacteria.

Moving forward in plant food safety and security through NanoBioSensors: Adopt or adapt biomedical technologies?

Plant-based foods are integral part of our day-to-day diet. Increasing world population has put forth an ever increasing demand for plant-based foods, and food security remains a major concern. Similarly, biological, chemical, and physical threats to our food and increasing regulatory demands to control the presence of foreign species in food products have made food safety a growing issue. Nanotechnology has already established its roots in diverse disciplines. However, the food industry is yet to harness the full potential of the unique capabilities offered by this next-generation technology. While there might be safety concerns in regards to integration of nanoproducts with our food products, an aspect of nanotechnology that can make remarkable contribution to different elements of the food chain is the use of nanobiosensors and diagnostic platforms for monitoring food traceability, quality, safety, and nutritional value. This brings us to an important question that whether existing diagnostic platforms that have already been well developed for biomedical and clinical application are suitable for food industry or whether the demands of the food industry are altogether different that may not allow adoption/adaptation of the existing technology. This review is an effort to raise this important "uncomfortable" yet "timely" question.

Direct detection of unamplified hepatoma upregulated protein RNA in urine using gold nanoparticles for bladder cancer diagnosis

OBJECTIVE

To develop a gold nanoparticle (AuNP) assay for direct detection of unamplified HURP RNA in urine.

DESIGN AND METHODS

HURP RNA was extracted from urine samples (50 bladder carcinoma patients, 25 benign bladder lesions, and 25 controls) and further purified using magnetic nanoparticles (MNPs), functionalized with HURP RNA-specific oligonucleotides, and then detected by RT-PCR or gold nanoparticles.

RESULTS

The developed HURP RNA AuNP assay has a sensitivity and a specificity of 88.5% and 94%, respectively, and a detection limit of 2.4 nmol/L. The concordance between the HURP AuNP assay with RT-PCR after RNA purification using functionalized MNPs was 97%.

CONCLUSIONS

The developed colorimetric HURP RNA AuNP assay is sensitive, simple, and can aid noninvasive diagnosis of bladder cancer.