Approaches towards molecular amplification for sensing

Abstract

Diagnostic assays that rely on molecular interactions have come a long way; from initial reversible detection systems towards irreversible reaction indicator-based methods. More recently, the emergence of innovative molecular amplification methodologies has revolutionised sensing, allowing diagnostic assays to achieve ultra-low limits of detection. There have been a significant number of molecular amplification approaches developed over recent years to accommodate the wide variety of analytes that require sensitive detection. To celebrate this achievement, this comprehensive critical review has been compiled to give a broad overview of the many different approaches used to attain amplification in sensing with an aim to inspire the next generation of diagnostic assays looking to achieve the ultimate detection limit. This review has been created with the focus on how each conceptually unique molecular amplification methodology achieves amplification, not just its sensitivity, while highlighting any key processes. Excluded are any references that were not found to contain an obvious molecular amplifier or amplification component, or that did not use an appropriate signal readout that could be incorporated into a sensing application. Additionally, methodologies where amplification is achieved through advances in instrumentation are also excluded. Depending upon the type of approach employed, amplification strategies are divided into four categories: target, label, signal or receptor amplification. More recent, more complex protocols combine a number of approaches and are therefore categorised by which amplification component described within was considered as the biggest advancement. The advantages and disadvantages of each methodology are discussed along with any limits of detection, if stated in the original article. Any subsequent use of the methodology within sensing or any other application is also mentioned to draw attention to its practicality. The importance of amplification within sensing is wholly emphasised while perspectives on the future direction of the field are also shared.

Exponential Molecular Amplification by H2O2‐Mediated Autocatalytic Deprotection of Boronic Ester Probes to Redox Cyclers

“…Molecular and biomolecular amplifications are of upmost importance in the transduction of (bio)chemical events into sensitive output signals, with many implications in areas ranging from cell signaling 1 to in vitro diagnostic. 2,3 Among the wide variety of molecular amplification schemes, those based on nonlinear signal-gain are undeniably the most powerful in terms of sensitivity and dynamic range. An emblematic example is the exponential molecular amplification of nucleic acids by PCR, a technique that was proven decisive in achieving the ultimate specific quantification of a few target nucleic acid sequences in a few tens of microliters.…”

An Auto‐Inductive Cascade for the Optical Sensing of Thiols in Aqueous Media: Application in the Detection of a VX Nerve Agent Mimic

“…[2] Many of these strategies utilize catalysts that are activated to generate fluorophores exponentially [3] or copies of the initial trigger,as in the polymerase chain reaction (PCR), allowing the trace detection of DNAt hrough rounds of exponential amplification. [3,4] Exponential signal amplification offers significant advantages to conventional detection, such as increased sensitivity and lower limits of detection (LOD), continually inspiring the development of new approaches.…”

“…[3,4] Exponential signal amplification offers significant advantages to conventional detection, such as increased sensitivity and lower limits of detection (LOD), continually inspiring the development of new approaches. [3,5] In 2009, an exponential amplification method was reported by Shabat for the detection of hydrogen peroxide based on ad endritic chain reaction (DCR). [6] Subsequently, aseries of auto-inductive cascades for signal amplification in response to fluoride or H 2 O 2 were developed by Shabat, [7] Phillips, [8] and others groups [9] including our own.…”

An Auto‐Inductive Cascade for the Optical Sensing of Thiols in Aqueous Media: Application in the Detection of a VX Nerve Agent Mimic

“…To increase the stoichiometric response of a receptor to a single analyte molecule by amplifying the signal, multiple strategies have been introduced . Many of these strategies utilize catalysts that are activated to generate fluorophores exponentially or copies of the initial trigger, as in the polymerase chain reaction (PCR), allowing the trace detection of DNA through rounds of exponential amplification . Exponential signal amplification offers significant advantages to conventional detection, such as increased sensitivity and lower limits of detection (LOD), continually inspiring the development of new approaches …”