Nano RNA aptamer wire for analysis of vitamin B₁₂

Application of Nanoparticles in Human Nutrition: A Review

Nanotechnology in human nutrition represents an innovative advance in increasing the bioavailability and efficiency of bioactive compounds. This work delves into the multifaceted dietary contributions of nanoparticles (NPs) and their utilization for improving nutrient absorption and ensuring food safety. NPs exhibit exceptional solubility, a significant surface-to-volume ratio, and diameters ranging from 1 to 100 nm, rendering them invaluable for applications such as tissue engineering and drug delivery, as well as elevating food quality. The encapsulation of vitamins, minerals, and antioxidants within NPs introduces an innovative approach to counteract nutritional instabilities and low solubility, promoting human health. Nanoencapsulation methods have included the production of nanocomposites, nanofibers, and nanoemulsions to benefit the delivery of bioactive food compounds. Nutrition-based nanotechnology and nanoceuticals are examined for their economic viability and potential to increase nutrient absorption. Although the advancement of nanotechnology in food demonstrates promising results, some limitations and concerns related to safety and regulation need to be widely discussed in future research. Thus, the potential of nanotechnology could open new paths for applications and significant advances in food, benefiting human nutrition.

Nanoparticle applications in food - a review

The use of nanotechnology in the food industry raises uncertainty in many respects. For years, achievements of nanotechnology have been applied mainly in biomedicine and computer science, but recently it has also been used in the food industry. Due to the extremely small (nano) scale, the properties and behavior of nanomaterials may differ from their macroscopic counterparts. They can be used as biosensors to detect reagents or microorganisms, monitor bacterial growth conditions, increase food durability e.g. when placed in food packaging, reducing the amount of certain ingredients without changing the consistency of the product (research on fat substitutes is underway), improve the taste of food, make some nutrients get better absorbed by the body, etc. There are companies on the market that are already introducing nanoparticles into the economy to improve their functionality, e.g. baby feeding bottles. This review focuses on the use of nanoparticles in the food industry, both organic (chitosan, cellulose, proteins) and inorganic (silver, iron, zinc oxide, titanium oxide, etc.). The use of nanomaterials in food production requires compliance with all legal requirements regarding the safety and quantity of nano-processed food products described in this review. In the future, new methods of testing nanoparticles should be developed that would ensure the effectiveness of compounds subjected to, for example, nano-encapsulation, i.e. whether the encapsulation process had a positive impact on the specific properties of these compounds. Nanotechnology has revolutionized our approach towards food engineering (from production to processing), food storage and the creation of new materials and products, and the search for new product applications.

LSPR-based colorimetric biosensing for food quality and safety

Ensuring consistently high quality and safety is paramount to food producers and consumers alike. Wet chemistry and microbiological methods provide accurate results, but those methods are not conducive to rapid, onsite testing needs. Hence, many efforts have focused on rapid testing for food quality and safety, including the development of various biosensors. Herein, we focus on a group of biosensors, which provide visually recognizable colorimetric signals within minutes and can be used onsite. Although there are different ways to achieve visual color-change signals, we restrict our focus on sensors that exploit the localized surface plasmon resonance (LSPR) phenomenon of metal nanoparticles, primarily gold and silver nanoparticles. The typical approach in the design of LSPR biosensors is to conjugate biorecognition ligands on the surface of metal nanoparticles and allow the ligands to specifically recognize and bind the target analyte. This ligand-target binding reaction leads to a change in color of the test sample and a concomitant shift in the ultraviolet-visual absorption peak. Various designs applying this and other signal generation schemes are reviewed with an emphasis on those applied for evaluating factors that compromise the quality and safety of food and agricultural products. The LSPR-based colorimetric biosensing platform is a promising technology for enhancing food quality and safety. Aided by the advances in nanotechnology, this sensing technique lends itself easily for further development on field-deployable platforms such as smartphones for onsite and end-user applications.

Future Perspectives of Therapeutic, Diagnostic and Prognostic Aptamers in Eye Pathological Angiogenesis

Aptamers are single-stranded DNA or RNA oligonucleotides that are currently used in clinical trials due to their selectivity and specificity to bind small molecules such as proteins, peptides, viral particles, vitamins, metal ions and even whole cells. Aptamers are highly specific to their targets, they are smaller than antibodies and fragment antibodies, they can be easily conjugated to multiple surfaces and ions and controllable post-production modifications can be performed. Aptamers have been therapeutically used for age-related macular degeneration, cancer, thrombosis and inflammatory diseases. The aim of this review is to highlight the therapeutic, diagnostic and prognostic possibilities associated with aptamers, focusing on eye pathological angiogenesis.

Enhanced sensitivity and detection range of FRET-based vitamin B12 nanosensor

Vitamin B₁₂ (cobalamin) is a cobalt-containing compound that acts as an essential co-factor for various enzymes involved in the metabolic processes of the living cells. The constructed FRET Sensor for Vitamin Anemia Linked (SenVitAL) displayed marginal FRET efficiency. Here, we report the development of a molecular SenVitAL containing enhanced cyan fluorescent protein (ECFP) and venus as FRET pair to improve the FRET efficiency for optical imaging and screening of already developed sensor by our group. The sensor is the improved version of previously reported SenVitAL and consists of ECFP/venus as FRET pair instead of the originally used pair CFP/YFP. To increase the physiological range of vitamin B₁₂ measurement, affinity mutants were created. Compared to the wild type, SenVitAL-5 with W44Q mutation has higher affinity and displayed large dynamic detection range (0.10-480 µM) in response to vitamin B₁₂ binding. For cell-based monitoring and dynamic measurement of vitamin B₁₂ flux rates_, SenVitAL-5 was successfully expressed in cytosol of yeast and mammalian cells. Changes in the emission intensities of the two fluorophores were detected using confocal microscopy in both cell types in response to vitamin B₁₂. With the addition of 50 µM extracellular vitamin B₁₂ to the cells, the emission intensity of venus increased and that of ECFP decreased over the time. Furthermore, the results show that the variant SenVitAL-5 measures the vitamin B₁₂ in a concentration-dependent manner, showing the resulting increase in the FRET ratio and thus confirming its utility as an ideal fluorescent indicator for the detection of vitamin B₁₂ in eukaryotic systems in real time.

Measurement of aflatoxin M1 in powder and pasteurized milk samples by using a label-free electrochemical aptasensor based on platinum nanoparticles loaded on Fe-based metal-organic frameworks

In the present study, a sensitive label-free electrochemical aptasensor is introduced to measure aflatoxin M1 (AFM1) by using platinum nanoparticles (PtNPs) decorated on a glassy carbon electrode (GCE) modified with Fe-based metal-organic frameworks, MIL-101(Fe). The MIL-101(Fe) and the PtNP/MIL-101(Fe) are synthesized and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, UV-Visible spectroscopy, and field-emission scanning electron microscopy. Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) are done to monitor the fabrication processes of the aptasensor. In optimum conditions, the linear calibration range of 1.0 × 10^-2 to 80.0 ng mL^-1 and the detection limit of 2.0 × 10^-3 ng mL^-1 are obtained to measure AFM1 concentration using the EIS method. Finally, the fabricated aptasensor is successfully applied to measure AFM1 concentration in powder and pasteurized milk samples.

Aptamers as potential recognition elements for detection of vitamins and minerals: a systematic and critical review

Background: Vitamin and mineral deficiencies are prevalent globally, and extensive efforts have been made to assess their status. Most traditional methods are expensive and time-consuming; therefore, developments of rapid, simple, specific, and sensitive methods for the assessment of vitamins and minerals in biological samples are of high importance in research. Aptamers are synthetic nucleic acid single-stranded DNA or RNA that can be synthesized in vitro. They can be engineered to be analyte-specific and have been suggested as a substitute for monoclonal antibodies, due to their high sensitivity and affinity. In addition, aptamers can be chemically synthesized and readily modified for use as biosensors. These features make aptamers a promising tool for the detection of biological analytes. In this review, we provide an overview of the potential use of aptamer-based biosensors.Methods: Search terms were conducted on several online databases, including Google Scholar, PubMed, Scopus, and Science Direct from January 2000 to August 2019. Eligibility criteria were used and quality evaluation was performed. Following the review of 4349 articles, 39 articles met the inclusion criteria.Results: Aptasensors have recently been developed for the detection of vitamins by using optical methods, with a detection range from 74 pM to 204 pM, and lower limit of detection of 2.4 pM. Both electrochemical and optical methods have been used for detection of minerals, however electrochemical methods show a wider linear range and lower detection limits compared to optical methods with a wide linear range from 0.2 fM to 1.0 mM and limit of detection of 14.7 fM.Conclusion: The current report reviews recent developments in aptamer-based biosensors for detection of vitamins and minerals. Studies have shown that aptasensors' properties are suitable for the quantification of vitamins and minerals with high sensitivity, affinity, and specificity. Nevertheless, the limitations and future directions of aptamers require further research and new technological innovation.

Competitive adsorption on gold nanoparticles for human papillomavirus 16 L1 protein detection by LDI-MS

The detection of the HPV L1 protein provides information about the infection status of the virus, reflects the replication status of the HPV virus in cervical cells, and helps understand the regression and progress of cervical lesions. Herein, we report a novel laser desorption ionization mass spectrometry (LDI MS) method for the sensitive detection of the HPV 16 L1 protein, based on non-covalent competitive adsorption between the HPV 16 L1 aptamer and melamine on gold nanoparticles (AuNPs). The intensity of the MS signal corresponding to the mass tag shows a linear relationship with the HPV 16 L1 concentration in the range 2-80 ng mL^-1, with a limit of detection (LOD) of 58.8 pg mL^-1. Using this method, the HPV 16 L1 protein is quantitatively analyzed in both clinical and vaccine samples. The described method is simple and has high sensitivity and good reliability.

Squamous Cell Carcinoma Biomarker Sensing on a Strontium Oxide-Modified Interdigitated Electrode Surface for the Diagnosis of Cervical Cancer

Cervical cancer is a life-threatening complication, appearing as the uncontrolled growth of abnormal cells in the lining of the cervix. Every year, increasing numbers of cervical cancer cases are reported worldwide. Different identification strategies were proposed to detect cervical cancer at the earlier stages using various biomarkers. Squamous cell carcinoma antigen (SCC-Ag) is one of the potential biomarkers for this diagnosis. Nanomaterial-based detection systems were shown to be efficient with different clinical biomarkers. In this study, we have demonstrated strontium oxide-modified interdigitated electrode (IDE) fabrication by the sol-gel method and characterized by scanning electron microscopy and high-power microscopy. Analysis of the bare devices indicated the reproducibility with the fabrication, and further pH scouting on the device revealed that the reliability of the working pH ranges from 3 to 9. The sensing surface was tested to detect SCC-Ag against its specific antibody; the detection limit was found to be 10 pM, and the sensitivity was in the range between 1 and 10 pM as calculated by 3σ. The specificity experiment was carried out using major proteins from human serum, such as albumin and globulin. SCC-Ag was shown to be selectively detected on the strontium oxide-modified IDE surface.

Smartphone-based colorimetric chiral recognition of ibuprofen using aptamers-capped gold nanoparticles

Sensitive and fast detection of ibuprofen enantiomers is very critical for required routine monitoring and risk assessment of trace pollutants in water samples. Here a simple, rapid and highly sensitive android smartphone application for chiral recognition was developed. Aptamer-capped gold nanoparticles (AuNPs) was demonstrated as an efficient detection platform for (S)-(+)-ibuprofen (S-Ibu) and (R)-(-)-ibuprofen (R-Ibu). Detachment of an enantioselective aptamer from the AuNPs surface and binding with an enantiomer of Ibu lead to AuNPs aggregation, which allows a rapid enantiodiscrimination of Ibu by monitoring the absorbance changes of AuNPs solution in the UV-vis spectrum. Under optimal conditions, the limit of detection for S-Ibu and R-Ibu was 1.24 and 3.91 pg/mL, respectively. These probes showed good chiral recognition ability in mixed samples (i.e. S-Ibu + R-Ibu) and environmental samples. These advantages can be further developed by quantitative measurement with smartphone, which opens new opportunities for on-site detection of trace chiral pollutants in a simple and practical manner.

Variations in Spontaneous Assembly and Disassembly of Molecules on Unmodified Gold Nanoparticles

Electrostatic attraction, covalent binding, and hydrophobic absorption are spontaneous processes to assemble and disassemble the molecules of gold nanoparticles (GNP). This dynamic change can be performed in the presence of ions, such as NaCl or charged molecules. Current research encompasses the GNP in mediating non-biofouling and investigating the molecular attachment and detachment. Experiments were performed with different sizes of GNP and polymers. As a proof of concept, poly(ethylene glycol)-b-poly(acrylic acid), called PEG-PAAc, attachment and binding events between factor IX and factor IX-bp from snake venom were demonstrated, and the variations with these molecular attachment on GNP were shown. Optimal concentration of NaCl for GNP aggregation was 250 mM, and the optimal size of GNP used was 30 nm. The polymer PEG-PAAc (1 mg/ml) has a strong affinity to the GNP as indicated by the dispersed GNP. The concentration of 5800 nM of factor IX was proved to be optimal for dispersion of GNP, and at least 100 nM of factor IX-bp was needed to remove factor IX from the surface of GNP. This study delineates the usage of unmodified GNP for molecular analysis and downstream applications.

An ultrasensitive aptasensor for hemin and hemoglobin based on signal amplification via electrocatalytic oxygen reduction

The present study aims at the fabrication of a novel electrochemical aptasensor, Ap-GA-AMSN-GCE, for the label-free determination of hemin and hemoglobin (Hb). Basically, the electrochemical reduction current of hemin or Hb incubated on Ap-GA-AMSN-GCE in the presence of oxygen serves as an excellent signal for quantitative determination of these analytes. By differential pulse voltammetry, the calibration plot was linear in the concentration range of 1.0 × 10^-19-1.0 × 10^-6 M of hemin and Hb. Also, the detection limits, DL, of hemin and Hb were found to be 7.5 × 10^-20 M and 6.5 × 10^-20 M respectively. According to the experimental results, using the proposed aptasensor in the absence of any oxygen molecule in the analytical solution, the DL value of hemin was 1.0 × 10^-12 M. The very low DL obtained in the presence of oxygen is due to the excellent electrocatalytic activity of hemin and Hb incubated on the aptasensor for oxygen reduction. This electrocatalytic activity has a key role in bringing about excellent low detection limits, DL, and wide linear concentration ranges of analytes. Finally, this aptasensor was satisfactorily used for the determination of Hb in human blood samples.

Selection and Biosensor Application of Aptamers for Small Molecules

Small molecules play a major role in the human body and as drugs, toxins, and chemicals. Tools to detect and quantify them are therefore in high demand. This review will give an overview about aptamers interacting with small molecules and their selection. We discuss the current state of the field, including advantages as well as problems associated with their use and possible solutions to tackle these. We then discuss different kinds of small molecule aptamer-based sensors described in literature and their applications, ranging from detecting drinking water contaminations to RNA imaging.

Evaluation of multi-target immunogenic reagents for the detection of latent and body fluid-contaminated fingermarks

Fingermark enhancement reagents capable of molecular recognition offer a highly selective and sensitive method of detection. Antibodies and aptamers provide a high degree of adaptability for visualisation, allowing for the selection of the most appropriate visualisation wavelength for a particular substrate without the need for specialist equipment or image processing. However, the major hurdle to overcome is the balance between sensitivity and selectivity. Single-target molecular recognition is highly specific, purported to have better detection limits than chemical reactions or stains, and can provide information about the donor or activity, but often results in incomplete ridge pattern development. Consequently, the development and evaluation of multi-target biomolecular reagents for fingermark enhancement was investigated, with the focus on endogenous eccrine secretions. To assess the suitability of the immunogenic reagents for potential operational use, a variety of parameters (i.e., processing time, fixing and working solution conditions) were optimised on a wide range of non-porous and semi-porous substrates. The relative performance of immunogenic reagents was compared to that of routine techniques applied to latent marks and marks in blood, semen and saliva. The incorporation of these novel reagents into routine technique sequences was also investigated. The experimental results indicated that the multi-target immunogenic reagents were not a suitable alternative to routine detection methods or sequences, but may have promise as a "last resort" method for difficult substrates or cases.

An exonuclease-assisted amplification electrochemical aptasensor of thrombin coupling "signal on/off" strategy

In this work, a dual-signaling electrochemical aptasensor based on exonuclease-catalyzed target recycling was developed for thrombin detection. The proposed aptasensor coupled "signal-on" and "signal-off" strategies. As to the construction of the aptasensor, ferrocene (Fc) labeled thrombin binding aptamer (TBA) could perfectly hybridize with the methylene blue (MB) modified thiolated capture DNA to form double-stranded structure, hence emerged two different electrochemical signals. In the presence of thrombin, TBA could form a G-quadruplex structure with thrombin, leading to the dissociation of TBA from the duplex DNA and capture DNA formed hairpin structure. Exonuclease could selectively digest single-stranded TBA in G-quadruplex structure and released thrombin to realize target recycling. As a consequence, the electrochemical signal of MB enhanced significantly, which realized "signal on" strategy, meanwhile, the deoxidization peak current of Fc decreased distinctly, which realized "signal off" strategy. The employment of exonuclease and superposition of two signals significantly improved the sensitivity of the aptasensor. In this way, an aptasensor with high sensitivity, good stability and selectivity for quantitative detection of thrombin was constructed, which exhibited a good linear range from 5 pM to 50 nM with a detection limit of 0.9 pM (defined as S/N=3). In addition, this design strategy could be applied to the detection of other proteins and small molecules.

Colorimetric detection of controlled assembly and disassembly of aptamers on unmodified gold nanoparticles

Aptamers are nucleic acid ligands that are generated artificially by in vitro selection and behave similar to antibodies. The development of aptamer-based sensing systems or strategies has been in vogue for the past few decades, because aptamers are smaller in size, stable, cheaper and undergo easier modifications. Owing to these advantages, several facile aptamer-based colorimetric strategies have been created by controlling the assembly and disassembly of aptamers on unmodified gold nanoparticle probes. As these kinds of assay systems are rapid and can be visualized unaided by instruments, they have recently become an attractive method of choice. The formation of purple-colored aggregates (attraction) from the red dispersed (repulsion) state of GNPs in the presence of mono- or divalent ions is the key principle behind this assay. Due to its simplicity and versatility, this assay can be an alternative to existing diagnostic assays. Here, we have investigated the critical elements involved in colorimetric assays, and have screened different proteins and small ligands to evaluate biofouling on GNPs.

Peptide nucleic acids: a review on recent patents and technology transfer

INTRODUCTION

DNA/RNA-based drugs are considered of major interest in molecular diagnosis and nonviral gene therapy. In this field, peptide nucleic acids (PNAs, DNA analogs in which the sugar-phosphate backbone is replaced by N-(2-aminoethyl)glycine units or similar building blocks) have been demonstrated to be excellent candidates as diagnostic reagents and biodrugs.

AREAS COVERED

Recent (2002 - 2013) patents based on studies on development of PNA analogs, delivery systems for PNAs, applications of PNAs in molecular diagnosis, and use of PNA for innovative therapeutic protocols.

EXPERT OPINION

PNAs are unique reagents in molecular diagnosis and have been proven to be very active and specific for alteration of gene expression, despite the fact that solubility and uptake by target cells can be limiting factors. Accordingly, patents on PNAs have taken in great consideration delivery strategies. PNAs have been proven stable and effective in vivo, despite the fact that possible long-term toxicity should be considered. For possible clinical applications, the use of PNA molecules in combination with drugs already employed in therapy has been suggested. Considering the patents available and the results on in vivo testing on animal models, we expect in the near future relevant PNA-based clinical trials.

Biosensors in food processing

Optical based sensing systems that measure luminescence, fluorescence, reflectance and absorbance, etc., are some of the areas of applications of optical immunosensors. Immunological methods rely on specific binding of an antibody (monoclonal, polyclonal or engineered) to an antigen. Detection of specific microorganisms and microbial toxins requires immobilization of specific antibodies onto a given transducer that can produce signal upon attachment of typical microbe/microbial toxins. Inherent features of immunosensors such as specificity, sensitivity, speed, ease and on-site analysis can be made use for various applications. Safety of food and environment has been a major concern of food technologists and health scientists in recent years. There exists a strong need for rapid and sensitive detection of different components of foods and beverages along with the food borne and water borne pathogens, toxins and pesticide residues with high specificity. Biosensors present attractive, efficient alternative techniques by providing quick and reliable performances. There is a very good potential for application of biosensors for monitoring food quality and safety in food and bioprocessing industries in India.

Aptamer--nanoparticle-based chemiluminescence for p53 protein

A simple colorimetric biosensing technique based on the interaction of gold nanoparticles (AuNPs) with the aptamer was developed for detection of p53, a tumor suppressor protein, in the current study. Aggregation of AuNPs was induced by desorption of the p53 binding RNA aptamer from the surface of AuNPs as a result of the aptamer target interaction leading to the color change of AuNPs from red to purple. The detection limit of p53 protein by the colorimetric approach was 0.1 ng/ml after successful optimization of the amount of aptamer, AuNPs, salts, and incubation time. Furthermore, the catalytic activity of the aggregated AuNPs was greatly enhanced by chemiluminescence (CL) reaction, where the detection limit was enhanced to 10 pg/ml with a regression coefficient of R2 = 0.9907. Here the sensitivity was increased by 10-fold compared with the AuNP-based colorimetric method. Hence, the sensitivity of detection was increased by employing CL, by using the catalytic activity of aggregated AuNPs, on the luminol-hydrogen peroxide reaction. Thus, the combination of colorimetric and CL-based aptasensor can be of great advantage in increasing the sensitivity of detection for any target analyte.

In vitro selection of a DNA aptamer targeted against Shigella dysenteriae

To identify DNA aptamers demonstrating binding specificity for Shigella dysenteriae, a whole-bacterium Systemic Evolution of Ligands by Exponential enrichment (SELEX) method was applied to a combinatorial library of single-stranded DNA (ssDNA) molecules. After several rounds of selection using S. dysenteriae as the target, the highly enriched oligonucleotide pool was sequenced and then grouped into different families based on primary sequence homologies and similarities in the secondary structures. Aptamer S 1, which showed particularly high binding affinity in preliminary studies, was chosen for further characterisation. This aptamer displayed a dissociation constant (Kd value) of 23.47 ± 2.48 nM. Binding assays to assess the specificity of aptamer S 1 showed high binding affinity for S. dysenteriae and low apparent binding affinity for other bacteria. The ssDNA aptamers generated may serve as a new type of molecular probe for microbial pathogens, as it has the potential to overcome the tedious isolation and purification requirements for complex targets.

Hydroxylamine amplified gold nanoparticle-based aptameric system for the highly selective and sensitive detection of platelet-derived growth factor

This study developed a sensitive and selective aptamer-based chemiluminescent (CL) method for the determination of platelet-derived growth factor (PDGF)-BB using hydroxylamine enlarged gold nanoparticles (Au NPs). Rabbit anti-human PDGF-BB polyclonal antibody was covalently coupled on the 96-well plate that offers reactive N-oxysuccinimide ester (referred to as NOS group) surface. In the presence of target protein, the biotinylated aptamer was captured on the 96-well plate forming an antibody/PDGF-BB/biotinylated aptamer sandwiched complex, which was followed by the assembly of streptavidin coated Au NPs (streptavidin-gold). Au NPs assembled on the surface of 96-well plate reacted with HAuCl(4) and NH(2)OH, which enabled the catalytic deposition of gold metal onto the Au NPs surfaces. A huge number of Au(3+) ions were released from the hydroxylamine enlarged Au NPs after oxidative gold metal dissolution, which was determined by a simple and sensitive luminol CL reaction. The results showed that the detection limit of the assay is 60 pM of PDGF-BB (corresponding to 6 fmol in a 100 μL volume), which compares favorably with those of other PDGF-BB detection techniques. In addition, this aptameric CL biosensor demonstrated extraordinary specificity. And PDGF-BB has been determined in diluted serum indicating the applicability of this assay.