Nucleic acid amplification free biosensors for pathogen detection

Efficient and rapid detection of pathogens plays an important role in food safety, disease prevention, diagnosis and environmental monitoring. The traditional method for pathogen detection is plate culturing, consuming lots of time on separating, culturing and identifying pathogens by morphological characteristics, biochemical and serological reactions. It is a great advantage to take nucleic acids of pathogens as targets for detection because of higher specificity. The polymerase chain reaction (PCR) greatly shortens the time of pathogen detection but it is heavily dependent on temperature control instruments. Although isothermal amplification overcomes the defects of temperature control, it requires multiple enzymes or complex primers. Here, we summarize the recent advances in the amplification free methods for pathogen detection which are well developed for their simplicity, sensitivity and rapidity. Without nucleic acid amplification, we can directly detect the original nucleic acids of the samples rather than amplified nucleic acids. The amplification free methods for nucleic acid detection are mainly classified into electrochemical biosensors, optical biosensors and piezoelectric plate biosensors. This article describes the principles and compares the advantages and disadvantages of these methods. We further discuss the challenges and directions of this field, providing an overview for future researchers.