An electronic channel switching-based aptasensor for ultrasensitive protein detection

Biosensors for Detecting Lymphocytes and Immunoglobulins

Lymphocytes (B, T and natural killer cells) and immunoglobulins are essential for the adaptive immune response against external pathogens. Flow cytometry and enzyme-linked immunosorbent (ELISA) kits are the gold standards to detect immunoglobulins, B cells and T cells, whereas the impedance measurement is the most used technique for natural killer cells. For point-of-care, fast and low-cost devices, biosensors could be suitable for the reliable, stable and reproducible detection of immunoglobulins and lymphocytes. In the literature, such biosensors are commonly fabricated using antibodies, aptamers, proteins and nanomaterials, whereas electrochemical, optical and piezoelectric techniques are used for detection. This review describes how these measurement techniques and transducers can be used to fabricate biosensors for detecting lymphocytes and the total content of immunoglobulins. The various methods and configurations are reported, along with the advantages and current limitations.

Aptamers against Immunoglobulins: Design, Selection and Bioanalytical Applications

Nucleic acid aptamers show clear promise as diagnostic reagents, as highly specific strands were reported against a large variety of biomarkers. They have appealing benefits in terms of reproducible generation by chemical synthesis, controlled modification with labels and functionalities providing versatile means for detection and oriented immobilization, as along with high biochemical and temperature resistance. Aptamers against immunoglobulin targets-IgA, IgM, IgG and IgE-have a clear niche for diagnostic applications, therefore numerous aptamers have been selected and used in combination with a variety of detection techniques. The aim of this review is to overview and evaluate aptamers selected for the recognition of antibodies, in terms of their design, analytical properties and diagnostic applications. Aptamer candidates showed convincing performance among others to identify stress and upper respiratory tract infection through SIgA detection, for cancer cell recognition using membrane bound IgM, to detect and treat hemolytic transfusion reactions, autoimmune diseases with IgG and detection of IgE for allergy diseases. However, in general, their use still lags significantly behind what their claimed benefits and the plethora of application opportunities would forecast.

Aptamers Against Immunologic Targets: Diagnostic and Therapeutic Prospects

The concept of in vitro selection of nucleic acid aptamers emerged 25 years ago, and since then tremendous progress has been achieved in the development of different aptamers and their applications for various bioanalytical and therapeutic purposes. Among other protein targets of aptamers, immune system proteins are of particular interest both as diagnostic markers and therapeutic targets. The present review summarizes up-to-date articles concerning the selection and design of DNA and RNA aptamers against immunologic targets such as antibodies, cytokines, and T-cell and B-cell receptors. We also discuss the prospects of employing aptamers as recognizing modules of diagnostic aptasensors, potential therapeutic candidates for the treatment of autoimmune diseases and cancer, and specific tools for functional studies of immune system proteins.

Aptamer-based detection and quantitative analysis of human immunoglobulin E in capillary electrophoresis with chemiluminescence detection

A novel aptamer-based CE with chemiluminescence (CL) assay was developed for highly sensitive detection of human immunoglobulin E (IgE). The IgE aptamer was conjugated with gold nanoparticles (AuNPs) to form AuNPs-aptamer that could specifically recognize the IgE to produce an AuNPs-aptamer-IgE complex. The mixture of the AuNPs-aptamer-IgE complex and the unbounded AuNPs-aptamer could be effectively separated by CE and sensitively detected with luminol-H2 O2 CL system. By taking the advantage of the excellent catalytic behavior of AuNPs on luminol-H2 O2 CL system, the ultrasensitive detection of IgE was achieved. The detection limit of IgE is 7.6 fM (S/N = 3) with a linear range from 0.025 to 250 pM. Successful detection of IgE in human serum samples was demonstrated and the recoveries of 94.9-103.2% were obtained. The excellent assay features of the developed approach are its specificity, sensitivity, adaptability, and very small sample consumption. Our design provides a methodology model for determination of rare proteins in biological samples.

Aptamers: multifunctional molecules for biomedical research

Aptamers are single-stranded oligonucleotides that fold into well-defined three-dimensional shapes, allowing them to bind their targets with high affinity and specificity. They can be generated through an in vitro process called "Systemic Evolution of Ligands by Exponential Enrichment" and applied for specific detection, inhibition, and characterization of various targets like small organic and inorganic molecules, proteins, and whole cells. Aptamers have also been called chemical antibodies because of their synthetic origin and their similar modes of action to antibodies. They exhibit significant advantages over antibodies in terms of their small size, synthetic accessibility, and ability to be chemically modified and thus endowed with new properties. The first generation of aptamer drug "Macugen" was available for public use within 25 years of the discovery of aptamers. With others in the pipeline for clinical trials, this emerging field of medical biotechnology is raising significant interest. However, aptamers pose different problems for their development than for antibodies that need to be addressed to achieve practical applications. It is likely that current developments in aptamer engineering will be the basis for the evolution of improved future bioanalytical and biomedical applications. The present review discusses the development of aptamers for therapeutics, drug delivery, target validation and imaging, and reviews some of the challenges to fully realizing the promise of aptamers in biomedical applications.