Identification and Engineering of Aptamers for Theranostic Application in Human Health and Disorders

An aptamer is a short sequence of synthetic oligonucleotides which bind to their cognate target, specifically while maintaining similar or higher sensitivity compared to an antibody. The in-vitro selection of an aptamer, applying a conjoining approach of chemistry and molecular biology, is referred as Systematic Evolution of Ligands by Exponential enrichment (SELEX). These initial products of SELEX are further modified chemically in an attempt to make them stable in biofluid, avoiding nuclease digestion and renal clearance. While the modification is incorporated, enough care should be taken to maintain its sensitivity and specificity. These modifications and several improvisations have widened the window frame of aptamer applications that are currently not only restricted to in-vitro systems, but have also been used in molecular imaging for disease pathology and treatment. In the food industry, it has been used as sensor for detection of different diseases and fungal infections. In this review, we have discussed a brief history of its journey, along with applications where its role as a therapeutic plus diagnostic (theranostic) tool has been demonstrated. We have also highlighted the potential aptamer-mediated strategies for molecular targeting of COVID-19. Finally, the review focused on its future prospective in immunotherapy, as well as in identification of novel biomarkers in stem cells and also in single cell proteomics (scProteomics) to study intra or inter-tumor heterogeneity at the protein level. Small size, chemical synthesis, low batch variation, cost effectiveness, long shelf life and low immunogenicity provide advantages to the aptamer over the antibody. These physical and chemical properties of aptamers render them as a strong biomedical tool for theranostic purposes over the existing ones. The significance of aptamers in human health was the key finding of this review

Mutations in Spike Protein of SARS-CoV-2 Modulate Receptor Binding, Membrane Fusion and Immunogenicity: An Insight into Viral Tropism and Pathogenesis of COVID-19

SARS-CoV-2 uses RBD of Spike (S) protein to attach with human cell via ACE2 receptor, followed by protease priming at S1/S2 site resulted in host cell entry and pathogenesis. In this context, we focused our aim in studying natural mutations harboring in Spike protein of SARS-CoV-2. We have analyzed 420 COVID-19 cases. G476S and V483G mutation are observed which lies in the RBD region where as the prevalent D614G mutation is observed in the vicinity of S1/S2 site. Interestingly MD simulation supports strong favorable interaction of ACE2 with RBD region containing V483A mutation as compared to G476S and reference wild Wuhan S protein. Radius of gyration analysis also showed high degree of compactness in V483A. The landscape plot and Gibbs free energy also support our findings. Overall, our study indicates that V483G in the RBD region can enhance its binding with the human ACE2 receptor. Interestingly D614G mutation in vicinity of S1/S2 region introduced a new cleavage site specific for a serine protease elastase that is anticipated to broaden the virus host cell tropism. Hence, both V483A and D614G mutations led to enhanced and broaden the virus host cell entry and transmission of the disease. Further epitope mapping analysis revealed G476S and D614G mutations as antigenic determinants and thus these mutations are important while designing a therapeutics vaccine or chimeric antibody. This finding will help in further understanding the role of such arising mutations in modulating immunogenicity, viral tropism and pathogenesis of the disease, which in lieu will help in designing vaccine more precisely to mitigate pandemic COVID-19. </p

Therapeutic influence of simvastatin on MCF-7 and MDA-MB-231 breast cancer cells via mitochondrial depletion and improvement in chemosensitivity of cytotoxic drugs

Background: Breast cancer is the most commonly diagnosed cancer worldwide with 2.26 million cases in 2020. Cancer heterogeneity is the major challenge before existing therapeutic modalities due to metabolic variability of the cells as Warburg and anti-Warburg both type of metabolic phenotypes has been reported as a major contributing factors for cancer progression, invasion, metastasis and relapse. Also, this metabolic variability is associated with chemo and radio-resistance and poor therapeutic outcomes. Therefore, in present study we put an attempt to understand how simvastatin exert its effects on two metabolically different cell types and second how this drug can affect mitochondrial biomass, mt-DNA and glycolysis in both the cell types. Methods: We have observed effects of simvastatin on MCF-7 (dependent more on OXPHOS) and MDA-MB-231 (TNBC; more glycolytic with defected mitochondria) cells alone and after simvastatin pre-treatment followed by cytotoxic drugs including cisplatin, doxorubicin, gemcitabine, vincristine. We have conducted MTT assay for viability, cell death detection assay, apoptotic morphology study, scratch assay, transwell migration assay, lactate estimation in media (glycolysis parameter), mt-DNA to n-DNA ratio, mitotracker red (for mitochondrial membrane potential) and mitotracker green staining (for mitochondrial biomass) and qPCR to study expression of mitochondrial transcription factors and apoptotic genes including PGC-1α, NRF-1, NRF-2, TFAM, Bcl-2 and Bax. Results: We observed that 20 μM simvastatin (SIM) was most efficient dose for MCF-7, whereas 12.5 μM for MDA-MB-231 cells. Simvastatin itself caused a significant decrease in viability, increased cell death, and diminished wound closure in scratch assay as well as inhibited transwell migration. Also, the cells pre-treated with simvastatin for 72 h followed by treatment with cytotoxic drugs for 48 h increased chemo-sensitivity of cisplatin (CIS), doxorubicin (DOX), gemcitabine (GEM) and vincristine (VIN). SIM alone and in pre-treatment followed by cytotoxic drug treatment studies, there was a significant decrease in mitochondrial biomass and mitochondrial membrane potential (MMP), but also decreased glycolysis as evidenced by decrease in lactate levels in culture media. For inhibition of migratory potential, it was in the following order: CIS ˃ VIN ˃DOX˃ GEM, which was in the same order to diminish mitochondrial functionality (mt-DNA/n-DNA ratio, mitotracker green staining and a significant decrease in the expression of transcriptional factors of mitochondrial biogenesis). Contrastingly a decrease in the same order was observed in lactate concentration independent to the mitochondrial loss, but probably via inherent ability of the drugs to reduce lactate and glycolysis. However, for cell death, apoptotic phenotype, diminished expression of Bcl-2 along with increase in Bax and loss of viability, the efficiency of simvastatin alone and in pre-treatment studies was in the following order: VIN ˃ DOX˃GEM˃CIS, which was supported by loss of fluorescence of mitotracker red, suggested decrease in MMP; marker of cell death. Conclusion: We conclude that by using different doses simvastatin can target different metabolic phenotypes of breast cancer cells and can also increase the chemo-sensitivity of cytotoxic drugs, so that they can work efficiently at lower doses which will ultimately diminish the cost and toxicity issues