Selection of Peptidoglycan-Specific Aptamers for Bacterial Cells Identification

Abstract

Peptidoglycan is a highly complex and essential macromolecule of bacterial outer cell wall; it is a heteropolymer made up of linear glycan strands cross-linked by peptides. Peptidoglycan has a particular composition which makes it a possible target for specific bacterial recognition. Aptamers are single-stranded DNA or RNA oligonucleotides that bind to target molecules with high affinity and specificity. Aptamers can be labeled with different radioisotopes and possess several properties that make them suitable for molecular imaging. The purpose of this study was to obtain aptamers for use as radiopharmaceutical in bacterial infection diagnosis. Two aptamers (Antibac1 and Antibac2) against peptidoglycan were selected through the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) methodology. The dissociation constant (K d ) for Antibac1 was 0.415+0.047 μM and for Antibac2 was 1.261+0.280 μM. These aptamers labeled with 32 P showed high affinity for Staphylococcus aureus cells. The binding to S. aureus and Escherichia coli in vitro were significantly higher than for Candida albicans and human fibroblasts, demonstrating their specificity for bacterial cells. These results point Antibac1 and Antibac2 as promising tools for bacterial infections identification.

The challenges of glycan recognition with natural and artificial receptors

“…Two peptidoglycan-targeting DNA aptamers have also been identified that displayed high affinities towards Staphylococcus aureus cells. 160 The dissociation constants of the two aptamers towards peptidoglycan were 0.415 mM and 1.261 mM. It was observed that the aptamers had similar binding to both Gram negative and Gram positive bacterial cells, despite the latter typically consisting of a higher content of and more exposed peptidoglycan.…”

An update on radiotracer development for molecular imaging of bacterial infections

“…The synthesis of macromolecular peptidoglycan, a cell wall component that is present in both Gram-positive and Gram-negative bacteria, is another target for the specific imaging of bacterial infections. A single-stranded oligonucleotide [117], able to bind peptidoglycans with high specificity and sensitivity [118], was labelled with different radioisotopes and as such can be used for imaging bacterial and fungal infections [119,120]. Imaging studies with the 99m Tc-aptamer were carried out in thigh muscles of mice either infected with S. aureus, C. albicans, or with a sterile inflammation.…”

Oligonucleotide aptamers: promising and powerful diagnostic and therapeutic tools for infectious diseases

“…Therefore, several ssDNA aptamers have been developed against staphylococcal enterotoxins (SEs). To develop potential diagnostic agents, aptamer APT SEB1 for staphylococcal enterotoxin B (SEB), 42 aptamer C10 for S. aureus enterotoxin C1 (SEC1), 43 aptamer R12.06 for α-toxin, 44 aptamer Antibac1 and Antibac2 for a peptidoglycan 45 and aptamer PA#2/8 for protein A 46 were generated for the detection of SEs. Among these aptamers, aptamer R12.06 for αtoxin was utilized in a modified sandwich ELISA and sensitive detection of 200 nM a-toxin in undiluted human serum samples was achieved.…”