Aptamers: A Cutting-Edge Approach for Gram-Negative Bacterial Pathogen Identification

Early and accurate diagnoses of pathogenic microorganisms is essential to correctly identify diseases, treating infections, and tracking disease outbreaks associated with microbial infections, to develop precautionary measures that allow a fast and effective response in epidemics and pandemics, thus improving public health. Aptamers are a class of synthetic nucleic acid molecules with the potential to be used for medical purposes, since they can be directed towards any target molecule. Currently, the use of aptamers has increased because they are a useful tool in the detection of specific targets. We present a brief review of the use of aptamers to detect and identify bacteria or even some toxins with clinical importance. This work describes the advances in the technology of aptamers, with the purpose of providing knowledge to develop new aptamers for diagnoses and treatment of different diseases caused by infectious microorganisms.

DNA-aptamer-nanographene oxide as a targeted bio-theragnostic system in antimicrobial photodynamic therapy against Porphyromonas gingivalis

The aim of this study was to design and evaluate the specificity of a targeted bio-theragnostic system based on DNA-aptamer-nanographene oxide (NGO) against Porphyromonas gingivalis during antimicrobial photodynamic therapy (aPDT). Following synthesis and confirmation of NGO, the binding of selected labeled DNA-aptamer to NGO was performed and its hemolytic activity, cytotoxic effect, and release times were evaluated. The specificity of DNA-aptamer-NGO to P. gingivalis was determined. The antimicrobial effect, anti-biofilm potency, and anti-metabolic activity of aPDT were then assessed after the determination of the bacteriostatic and bactericidal concentrations of DNA-aptamer-NGO against P. gingivalis. Eventually, the apoptotic effect and anti-virulence capacity of aPDT based on DNA-aptamer-NGO were investigated. The results showed that NGO with a flaky, scale-like, and layered structure in non-cytotoxic DNA-aptamer-NGO has a continuous release in the weak-acid environment within a period of 240 h. The binding specificity of DNA-aptamer-NGO to P. gingivalis was confirmed by flow cytometry. When irradiated, non-hemolytic DNA-aptamer-NGO were photoactivated, generated ROS, and led to a significant decrease in the cell viability of P. gingivalis (P < 0.05). Also, the data indicated that DNA-aptamer-NGO-mediated aPDT led to a remarkable reduction of biofilms and metabolic activity of P. gingivalis compared to the control group (P < 0.05). In addition, the number of apoptotic cells increased slightly (P > 0.05) and the expression level of genes involved in bacterial biofilm formation and response to oxidative stress changed significantly after exposure to aPDT. It is concluded that aPDT using DNA-aptamer-NGO as a targeted bio-theragnostic system is a promising approach to detect and eliminate P. gingivalis as one of the main bacteria involved in periodontitis in periopathogenic complex in real-time and in situ.

Recent Advances in Aptamer-Based Biosensors for Detection of Pseudomonas aeruginosa

Increasing concerns about nosocomial infection, food and environmental safety have prompted the development of rapid, accurate, specific and ultrasensitive methods for the early detection of critical pathogens. Pseudomonas aeruginosa is one of the most common pathogens that cause infection. It is ubiquitous in nature, being found in water, soil, and food, and poses a great threat to public health. The conventional detection technologies are either time consuming or readily produce false positive/negative results, which makes them unsuitable for early diagnosis and spot detection of P. aeruginosa. To circumvent these drawbacks, many efforts have been made to develop biosensors using aptamers as bio-recognition elements. Various aptamer-based biosensors for clinical diagnostics, food, and environmental monitoring of P. aeruginosa have been developed in recent years. In this review, we focus on the latest advances in aptamer-based biosensors for detection of P. aeruginosa. Representative biosensors are outlined according to their sensing mechanisms, which include optical, electrochemical and other signal transduction methods. Possible future trends in aptamer biosensors for pathogen detection are also outlined.