Detection of an IL-6 Biomarker Using a GFET Platform Developed with a Facile Organic Solvent-Free Aptamer Immobilization Approach

Abstract

Aptamer-immobilized graphene field-effect transistors (GFETs) have become a well-known detection platform in the field of biosensing with various biomarkers such as proteins, bacteria, virus, as well as chemicals. A conventional aptamer immobilization technique on graphene involves a two-step crosslinking process. In the first step, a pyrene derivative is anchored onto the surface of graphene and, in the second step, an amine-terminated aptamer is crosslinked to the pyrene backbone with EDC/NHS (1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride/N-hydroxysuccinimide) chemistry. However, this process often requires the use of organic solvents such as dimethyl formamide (DMF) or dimethyl sulfoxide (DMSO) which are typically polar aprotic solvents and hence dissolves both polar and nonpolar compounds. The use of such solvents can be especially problematic in the fabrication of lab-on-a-chip or point-of-care diagnostic platforms as they can attack vulnerable materials such as polymers, passivation layers and microfluidic tubing leading to device damage and fluid leakage. To remedy such challenges, in this work, we demonstrate the use of pyrene-tagged DNA aptamers (PTDA) for performing a one-step aptamer immobilization technique to implement a GFET-based biosensor for the detection of Interleukin-6 (IL-6) protein biomarker. In this approach, the aptamer terminal is pre-tagged with a pyrene group which becomes soluble in aqueous solution. This obviates the need for using organic solvents, thereby enhancing the device integrity. In addition, an external electric field is applied during the functionalization step to increase the efficiency of aptamer immobilization and hence improved coverage and density. The results from this work could potentially open up new avenues for the use of GFET-based BioMEMS platforms by broadening the choice of materials used for device fabrication and integration.

The holy grail of pyrene-based surface ligands on the sensitivity of graphene-based field effect transistors

“…46 Usually, such electrostatic doping would shift V Dirac toward more positive gate voltage. 47 In fact, several groups have a similar reported negative V Dirac shift upon DNA aptamer immobilization on graphene, [48][49][50][51] which is attributed to a competitive n-doping effect induced through the interaction between the aptamer nucleoside groups and graphene. 52 The PMAL-aptamer functionalized GFET sensing principle is based on conformational changes of the aptamer loop upon cTnI target binding.…”

Wearable electronics for skin wound monitoring and healing

“…Considering the aptamer immobilization approach, Aptamers are DNA or RNA oligonucleotides designed to bind to various biomolecules with high specificity and sensitivity. Using this aptamer immobilization approach, an electrochemical aptasensor was developed with methylene blue(MB) as a redox label for detecting TNF-α [75] . It had a detection limit of 10 ng/ml and could sense up to 100 ng/ml in the linear range.…”

Determination of Drugs in Clinical Trials: Current Status and Outlook

“…As per experimental results, conductometric methods are fast, inexpensive, and repeatable; however, the main drawback is non-specific measurements. This means that the method cannot identify different types of ions; therefore, pre-knowledge prior to running the tests is essential [104][105][106].…”