China
Africa
Explore chapters and articles related to this topic
Biosensors for Disease Diagnosis
Published in Ayodeji Olalekan Salau, Shruti Jain, Meenakshi Sood, Computational Intelligence and Data Sciences, 2022
Ramneet Kaur, Dibita Mandal, Juveria Ansari, Prachi R. Londhe, Vedika Potdar, Vishakkha Dash
Bioreceptors are a component of the biosensor that takes part in the interaction between the biomarkers for disease detection and produce a signal by the biochemical reaction. The bioreceptors are very specific and exhibit high selectivity toward target detection. The most commonly used bioreceptors in the development of AD biosensors are aptamers and antibodies. Aptamers are also known as “chemical antibodies” as they resemble the functions of conventional antibodies and have an edge over the antibodies by having characteristics such as low molecular weight, good stability, low toxicity, reproducible in vitro synthesis, low immunogenicity and swift tissue penetration. Antibodies however, also have some beneficial properties such as reducing the amyloid plaques. The transducers are part of the biosensors that work in an optical or electrochemical fashion and are classified on the basis of the transducers used in it. They help in the interaction of the analyte with the detector element and subsequently convert it into measurable and quantified signals. The transducers used in the detection of AD are electrochemical and optical transducers, wherein the electrochemical bio-transducers transform chemical signals into a detectable signal and the optical bio-transducers use signal transduction, to collect information about the analyte [3].
Targeted Therapy for Cancer Stem Cells
Published in Surinder K. Batra, Moorthy P. Ponnusamy, Gene Regulation and Therapeutics for Cancer, 2021
Rama Krishna Nimmakayala, Saswati Karmakar, Garima Kaushik, Sanchita Rauth, Srikanth Barkeer, Saravanakumar Marimuthu, Moorthy P. Ponnusamy
Aptamers are small nucleic acid ligands, which can comprise RNA or single-stranded DNA, and possess high affinity and selectivity for their target molecules [123]. These strands of DNA or RNA fold into concrete 3-dimensional structures and recognize their targets based on this structure with a dissociation constant in pico to nanomolar range. Their low molecular weight (8-25 kDa) allows better, faster, and more efficient tissue penetration [123]. They are non-immunogenic since they are oligonucleotides and are thermally stable. They are also easily synthesized with low production cost and batch variation. They can also be modified with various functional moieties, making them ideal candidates for selective therapeutic approaches [123].
Nucleic Acids as Therapeutic Targets and Agents
Published in David E. Thurston, Ilona Pysz, Chemistry and Pharmacology of Anticancer Drugs, 2021
Aptamers offer advantages over antibodies in that they induce negligible or no immunogenicity in vivo, can be engineered in vitro, are readily produced by chemical synthesis, and generally have good stability and storage properties. However, although attempts have been made to produce aptamers toward transcription factors, one problem is that they do not always interact at the DNA-recognition site of the protein, and so can produce off-target effects.
Aptamer-based technology for radionuclide targeted imaging and therapy: a promising weapon against cancer
Published in Expert Review of Medical Devices, 2020
Luca Filippi, Oreste Bagni, Clara Nervi
Aptamer-based technology is very intriguing and promising for various applications in biomedicine, but several issues have still to be defined. In particular, it has to be underlined that the majority of pre-clinical researches have been performed with radionuclides suitable for gamma-camera and SPECT imaging, in spite of the more favorable characteristics of PET technology. It would be particularly welcome the development of aptamers radiolabeled with positron-emitters others than 18 F or 68 Ga, such as the radionuclide zirconium-89 (89Zr), which is becoming more and more popular in nuclear medicine due to its half-life of 78.41 h and high resolution for PET imaging [44]. In this regard, it is worth mentioning the research in the field of nanomedicine performed by Fletcher and colleagues. They synthesized hyperbranched polymers (HBP) that were firstly bound to 89Zr via the chelator deferoxamine (DFO) and then functionalized with a DNA aptamer directed toward VEGF-A. VEGF-A represents a potentially useful target for the management of triple negative breast cancer (TNBC), a highly aggressive malignancy with still limited therapeutic options. The synthesized nanoparticle, constituted by 89Zr-aptamer-HBP, was tested in mice bearing xenografts of TNBC: sequential microPET scans acquired at 1, 2, 3, 6, and 9 days post-NP injection demonstrated that the maximum signal in tumor is reached at day 3 [45].
Metabolism of bioconjugate therapeutics: why, when, and how?
Published in Drug Metabolism Reviews, 2020
Hanlan Liu, Jayaprakasam Bolleddula, Andrew Nichols, Lei Tang, Zhiyang Zhao, Chandra Prakash
Aptamers are single-stranded DNA or RNA molecules (usually containing 20–60 nucleotides) with specific three-dimensional structures that can bind with high specificity and affinity to molecular targets. Pegaptanib (MacQueen®) is a 28-base ribonucleic acid aptamer (Ruckman et al. 1998) developed to bind and block the activity of vascular endothelial growth factor for the treatment of neovascular (wet) age-related macular degeneration (AMD). Like other nucleotide drugs in development, the carbohydrate backbone of pegaptanib is modified to increase stability. In addition, it is covalently linked to two branched 20-kD PEG moieties to prolong the half-life of the drug in the vitreous (Gragoudas et al. 2004). In clinical studies, it was proven safe and demonstrated a statistically significant and clinically meaningful benefit for the treatment of AMD.
Targeted cancer drug delivery with aptamer-functionalized polymeric nanoparticles
Published in Journal of Drug Targeting, 2019
Sepideh Zununi Vahed, Nazanin Fathi, Mohammad Samiei, Solmaz Maleki Dizaj, Simin Sharifi
Although aptamers cannot be replaced antibodies, they are going to reach their own place of applications. Owing to their outstanding potentials, aptamers–nanoparticle conjugations display high ability for many medical applications such as drug delivery systems. Such combinations allow a screening with the ability to determine individual patient profiles. The rapid improvement of aptamer–NPs combination in treatment of cancer over the last two decades make it possible to speculate that this technology may become an interesting tool for clinicians in the following years. However, their administration in human encounters some challenges. Conjugation of aptamers on nanostructures may alter their 3D conformations that results in altered affinity and selectivity towards their ligands, the significant factors in targeted drug delivery. Moreover, even after conjugation with NPs, half-life of aptamers in human body fluids comprehensively depend on their resistance to nuclease enzymes. Although chemical changes in their structure can solve this issue, these alterations may also change aptamers’ 3D structural conformation. Moreover, transformed cells within progressing cancers can be heterogeneous and developing high specific aptamers would be a matter of attention. Accordingly, cancer biomarkers are highly unpredictable and may be express different between individuals; therefore, the affinity and selectivity of aptamer in cancer targeted therapy may not be expandable from one study to others.