Abstract
Aptamers that bind live bacterial cells have been widely investigated, but their potential to inhibit Candida albicans biofilm formation needs to be further explored. The aims of this study were to evaluate the binding of C. albicans to RNA aptamers and to examine the potential of aptamers to inhibit C. albicans biofilm formation in vitro. In this study, RNA aptamers selected against yeast cells of C. albicans ATCC 10231 were developed using the systematic evolution of ligands by exponential enrichment (SELEX) technique. The binding affinity of the resulting aptamers was then determined by an aptamer‐linked immobilized sorbent assay (ALISA), and a colorimetric (MTT) assay was used to measure the metabolic activity of Candida biofilms. After 11 rounds of SELEX, two candidate aptamers, Ca‐apt‐1 and Ca‐apt‐12, were identified. The Ca‐apt‐1 aptamer also recognized C. albicans isolated from clinical specimens but did not recognize other oral microorganisms (i.e., Streptococcus mutans and Saccharomyces cerevisiae). The ALISA results showed that the binding affinity of these aptamers was comparable to that of an anti‐C. albicans monoclonal antibody. In addition, Ca‐apt‐1 could inhibit biofilm and hyphal formation of C. albicans in vitro, as demonstrated using biofilm assays. This study shows that RNA aptamers could potentially be used in diagnostic and therapeutic applications for C. albicans‐related disease in the future.
Highlights
Candida albicans is a component of normal human flora and an opportunistic pathogen (Akpan & Morgan, 2002; Soll, 2002)
The results showed that both Ca‐apt‐1 and Ca‐apt‐12 can detect C. albicans at concentra‐ tions ranging from 50 to 5,000 cells/ml, and the aptamer‐linked immobilized sorbent assay (ALISA) performance is comparable to that of the enzyme‐linked immunosorbent assays (ELISA) method using C. albicans‐specific antibodies (Figure 2c)
Whole yeast cells of C. albicans strain ATCC 10231 were used as the target of RNA aptamer selection, as this may generate multiple targets in parallel (Shangguan et al, 2008) toward C. albicans cell surface molecules
Summary
Candida albicans is a component of normal human flora and an opportunistic pathogen (Akpan & Morgan, 2002; Soll, 2002). Compared to other fungal pathogens that exist primarily in either yeast or hyphal forms, C. albicans shows phenotypic plasticity be‐ cause it has the ability to switch between different morphological forms in response to environmental cues (Whiteway & Bachewich, 2007). This morphogenic switching from yeast to hyphal form con‐ tributes to the overall virulence of C. albicans We used the SELEX technique to select RNA ap‐ tamers with high affinity and specificity for C. albicans yeast cells. We investigated the ability of the aptamers to inhibit C. albicans growth in vitro
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