Nanomaterials for Fluorescent Detection of Hemoglobin

Hemoglobin plays a vital role in a series of biological activities. Abnormal levels of hemoglobin in blood are associated with many clinical diseases. Therefore, development of simple and accurate methods for sensing hemoglobin is of considerable significance. The blowout advancement in nanotechnology has urged the use of different types of fluorescent nanomaterials for hemoglobin assay. The past decades have witnessed the rapid progress of fluorescent nanosensors for hemoglobin assay. In the review, the sensing principles of fluorescent nanomaterials for sensing hemoglobin were briefly discussed. The advances of fluorescent nanosensors for detection of hemoglobin were further highlighted. And the sensing performance of fluorescent nanosensors versus traditional detection approaches was compared. Finally, the challenges and future directions of fluorescent nanomaterials for detection of hemoglobin are discussed. The review will arouse much more attention to the construction of hemoglobin sensors and facilitate rapid development of fluorescent nanosensors of hemoglobin.

Advances in Nanomaterial-Based Biosensors for Determination of Glycated Hemoglobin

Diabetes is a major public health burden whose prevalence has been steadily increasing over the past decades. Glycated hemoglobin (HbA1c) is currently the gold standard for diagnostics and monitoring glycemic control in diabetes patients. HbA1c biosensors are often considered to be cost-effective alternatives for smaller testing laboratories or clinics unable to access other reference methods. Many of these sensors deploy nanomaterials as recognition elements, detection labels, and/or transducers for achieving sensitive and selective detection of HbA1c. Nanomaterials have emerged as important sensor components due to their excellent optical and electrical properties, tunable morphologies, and easy integration into multiple sensing platforms. In this review, we discuss the advantages of using nanomaterials to construct HbA1c sensors and various sensing strategies for HbA1c measurements. Key gaps between the current technologies with what is needed moving forward are also summarized.

Direct and Label-Free Determination of Human Glycated Hemoglobin Levels Using Bacteriorhodopsin as the Biosensor Transducer

Glycated hemoglobin (HbA1c) levels are an important index for the diagnosis and long-term control of diabetes. This study is the first to use a direct and label-free photoelectric biosensor to determine HbA1c using bacteriorhodopsin-embedded purple membranes (PM) as a transducer. A biotinylated PM (b-PM) coated electrode that is layered with protein A-oriented antibodies against hemoglobin (Hb) readily captures non-glycated Hb (HbA0) and generates less photocurrent. The spectra of bacteriorhodopsin and Hb overlap so the photocurrent is reduced because of the partial absorption of the incident light by the captured Hb molecules. Two HbA0 and HbA1c aptasensors that are prepared by conjugating specific aptamers on b-PM coated electrodes single-step detect HbA0 and HbA1c in 15 min, without cross reactivity, with detection limits of ≤0.1 μg/mL and a dynamic range of 0.1–100 μg/mL. Both aptasensors exhibit high selectivity and long-term stability. For the clinical samples, HbA0 concentrations and HbA1c levels that are measured with aptasensors correlate well with total Hb concentrations and the HbA1c levels that are determined using standard methods (correlation gradient = 0.915 ± 0.004 and 0.981 ± 0.001, respectively). The use of these aptasensors for diabetes care is demonstrated.

Sensors/nanosensors based on upconversion materials for the determination of pharmaceuticals and biomolecules: An overview

Upconversion materials have been the focus of a large body of research in analytical and clinical fields in the last two decades owing to their ability to convert light between various spectral regions and their particular photophysical features. They emit efficient and sharp ultraviolet (UV) or visible luminescence after excitation with near-infrared (NIR) light. These features overcome some of the disadvantages reported for conventional fluorescent materials and provide opportunities for high sensitivity chemo-and bio-sensing. Here, we review studies that used upconversion materials as sensors for the determination of pharmaceuticals and biomolecules in the last two decades. The articles included in this review were retrieved from the SCOPUS database using the search phrases: "upconversion nanoparticles for determination of pharmaceutical compounds", and "upconversion nanoparticles for determination of biomolecules". Details of each developed upconversion nanoparticles based sensor along with their relevant analytical parameters are reported and carefully explained.

Surface chemistry modified upconversion nanoparticles as fluorescent sensor array for discrimination of foodborne pathogenic bacteria

BACKGROUND

The identification of foodborne pathogenic bacteria types plays a crucial role in food safety and public health. In consideration of long culturing times, tedious operations and the desired specific recognition elements in conventional methods, the alternative fluorescent sensor arrays can offer a high-effective approach in bacterial identification by using multiple cross-reactive receptors. Herein, we achieve this goal by constructing an upconversion fluorescent sensor array based on anti-stokes luminogens featuring a series of functional lanthanide-doped upconversion nanoparticles (UCNPs) with phenylboronic acid, phosphate groups, or imidazole ionic liquid. The prevalent spotlight effect of microorganism and the electrostatic interaction between UCNPs and bacteria endow such sensor array an excellent discrimination property.

RESULTS

Seven common foodborne pathogenic bacteria including two Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes) and five Gram-negative bacteria (Escherichia coli, Salmonella, Cronobacter sakazakii, Shigella flexneri and Vibrio parahaemolyticus) are precisely identified with 100% accuracy via linear discriminant analysis (LDA). Furthermore, blends of bacteria have been identified accurately. Bacteria in real samples (tap water, milk and beef) have been effectively discriminated with 92.1% accuracy.

CONCLUSIONS

Current fluorescence sensor array is a powerful tool for high-throughput bacteria identification, which overcomes the time-consuming bacteria culture and heavy dependence of specific recognition elements. The high efficiency of whole bacterial cell detection and the discrimination capability of life and death bacteria can brighten the application of fluorescence sensor array.

Different strategies for detection of HbA1c emphasizing on biosensors and point-of-care analyzers

Measurement of glycosylated hemoglobin (HbA1c) is a gold standard procedure for assessing long term glycemic control in individuals with diabetes mellitus as it gives the stable and reliable value of blood glucose levels for a period of 90-120 days. HbA1c is formed by the non-enzymatic glycation of terminal valine of hemoglobin. The analysis of HbA1c tends to be complicated because there are more than 300 different assay methods for measuring HbA1c which leads to variations in reported values from same samples. Therefore, standardization of detection methods is recommended. The review outlines the current research activities on developing assays including biosensors for the detection of HbA1c. The pros and cons of different techniques for measuring HbA1c are outlined. The performance of current point-of-care HbA1c analyzers available on the market are also compared and discussed. The future perspectives for HbA1c detection and diabetes management are proposed.