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Cell-targeting aptamers act as intracellular delivery vehicles

Gopinath SC, Lakshmipriya T, Chen Y, Arshad MK, Kerishnan JP, Ruslinda AR, et al.

Appl Microbiol Biotechnol, 2016 Aug;100(16):6955-69.
PMID: 27350620 DOI: 10.1007/s00253-016-7686-2

Aptamers are single-stranded nucleic acids or peptides identified from a randomized combinatorial library through specific interaction with the target of interest. Targets can be of any size, from small molecules to whole cells, attesting to the versatility of aptamers for binding a wide range of targets. Aptamers show drug properties that are analogous to antibodies, with high specificity and affinity to their target molecules. Aptamers can penetrate disease-causing microbial and mammalian cells. Generated aptamers that target surface biomarkers act as cell-targeting agents and intracellular delivery vehicles. Within this context, the "cell-internalizing aptamers" are widely investigated via the process of cell uptake with selective binding during in vivo systematic evolution of ligands by exponential enrichment (SELEX) or by cell-internalization SELEX, which targets cell surface antigens to be receptors. These internalizing aptamers are highly preferable for the localization and functional analyses of multiple targets. In this overview, we discuss the ways by which internalizing aptamers are generated and their successful applications. Furthermore, theranostic approaches featuring cell-internalized aptamers are discussed with the purpose of analyzing and diagnosing disease-causing pathogens.
Graphene oxide-gold nanoparticle-aptamer complexed probe for detecting amyloid beta oligomer by ELISA-based immunoassay

Zhao J, Chang W, Liu L, Xing X, Zhang C, Meng H, et al.

J Immunol Methods, 2021 02;489:112942.
PMID: 33333060 DOI: 10.1016/j.jim.2020.112942

Highly sensitive and easy detection method for Alzheimer's disease (AD) with a suitable biomarker is mandatory for preventing the factors resulting from AD. This research reports a modified ELISA with graphene for the detection of AD biomarker amyloid beta (Aβ) oligomer. Gold nanoparticle (AuNP) conjugated aptamer was used as the capture probe and attached on ELISA-graphene oxide surface through the amine linker. Antibody was used as the detection molecule to reach the maximum detection of Aβ oligomer. Suitable level of APTMS (2%), size of AuNP (30 nm) and aptamer concentration (2 μM) were optimized. This sandwich pattern of aptamer-Aβ oligomer-antibody helps to reach the detection at 50 pM on the optimized ELISA surface and the control experiments in the absence of Aβ oligomer or anti-Aβ oligomer antibody did not show the significant optical detection at 492 nm, indicting the specific detection. Further, Aβ oligomer spiked artificial cerebrospinal fluid did not interfere the detection of Aβ oligomer, confirming the selective detection. This new and modified ELISA surface helps to reach the lower detection of Aβ oligomer and diagnose AD.
Fulltext Nanodetection of Head and Neck Cancer on Titanium Oxide Sensing Surface

Wang Y, Guo Y, Lu J, Sun Y, Yu X, Gopinath SCB, et al.

Nanoscale Res Lett, 2020 Feb 03;15(1):33.
PMID: 32016709 DOI: 10.1186/s11671-020-3262-x

Head and neck cancer is a heterogeneous disease, originating in the squamous cells lining the larynx (voice box), mouth, pharynx (throat), nasal cavity and salivary glands. Head and neck cancer diagnosis at the later stage is greatly influencing the survival rate of the patient. It makes a mandatory situation to identify this cancer at the earlier stages of development with a suitable biomarker. Squamous cell carcinoma antigen (SCC-Ag) is a circulating serum tumour biomarker, and the elevated level has been found in the head and neck cancer patients and highly correlated with the tumour volume. The present research was carried out to detect and quantify the level of SCC-Ag on titanium oxide (TiO2)-modified interdigitated electrode sensor (IDE) by SCC-Ag antibody. The detection of SCC-Ag was found at the level of 100 fM, while it was improved to 10 fM when the antibody was conjugated with gold nanostar, representing a 10-fold improvement. Interestingly, this enhancement in sensitivity is 1000-folds higher than other substrates. Moreover, the specificity analysis was carried out using two different control proteins and noticed that the antibody only recognised SCC-Ag, indicating the specific detection on IDE-TiO2 sensing surface.
Fulltext Alzheimer's Disease Determination by a Dual Probe on Gold Nanourchins and Nanohorn Hybrids

Qiu Z, Shen Q, Jiang C, Yao L, Sun X, Li J, et al.

Int J Nanomedicine, 2021;16:2311-2322.
PMID: 33776435 DOI: 10.2147/IJN.S302396

Background: Alzheimer's disease (AD) is a neurodegenerative chronic disorder that causes dementia and problems in thinking, cognitive impairment and behavioral changes. Amyloid-beta (Aβ) is a peptide involved in AD progression, and a high level of Aβ is highly correlated with severe AD. Identifying and quantifying Aβ levels helps in the early treatment of AD and reduces the factors associated with AD.
Materials and Methods: This research introduced a dual probe detection system involving aptamers and antibodies to identify Aβ. Aptamers and antibodies were attached to the gold (Au) urchin and hybrid on the carbon nanohorn-modified surface. The nanohorn was immobilized on the sensor surface by using an amine linker, and then a Au urchin dual probe was immobilized.
Results: This dual probe-modified surface enhanced the current flow during Aβ detection compared with the surface with antibody as the probe. This dual probe interacted with higher numbers of Aβ peptides and reached the detection limit at 10 fM with R2=0.992. Furthermore, control experiments with nonimmune antibodies, complementary aptamer sequences and control proteins did not display the current responses, indicating the specific detection of Aβ.
Conclusion: Aβ-spiked artificial cerebrospinal fluid showed a similar response to current changes, confirming the selective identification of Aβ.