title: Optimisation and Characterisation of Anti-Fouling Ternary SAM Layers for Impedance-Based Aptasensors.
abstract: An aptasensor with enhanced anti-fouling properties has been developed. As a case study, the aptasensor was designed with specificity for human thrombin. The sensing platform was developed on screen printed electrodes and is composed of a self-assembled monolayer made from a ternary mixture of 15-base thiolated DNA aptamers specific for human thrombin co-immobilised with 1,6-hexanedithiol (HDT) and further passivated with 1-mercapto-6-hexanol (MCH). HDT binds to the surface by two of its thiol groups forming alkyl chain bridges and this architecture protects from non-specific attachment of molecules to the electrode surface. Using Electrochemical Impedance Spectroscopy (EIS), the aptasensor is able to detect human thrombin as variations in charge transfer resistance (Rct) upon protein binding. After exposure to a high concentration of non-specific Bovine Serum Albumin (BSA) solution, no changes in the Rct value were observed, highlighting the bio-fouling resistance of the surface generated. In this paper, we present the optimisation and characterisation of the aptasensor based on the ternary self-assembled monolayer (SAM) layer. We show that anti-fouling properties depend on the type of gold surface used for biosensor construction, which was also confirmed by contact angle measurements. We further studied the ratio between aptamers and HDT, which can determine the specificity and selectivity of the sensing layer. We also report the influence of buffer pH and temperature used for incubation of electrodes with proteins on detection and anti-fouling properties. Finally, the stability of the aptasensor was studied by storage of modified electrodes for up to 28 days in different buffers and atmospheric conditions. Aptasensors based on ternary SAM layers are highly promising for clinical applications for detection of a range of proteins in real biological samples.
authors.affiliation: Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK. a.miodek@bath.ac.uk.
authors.forename: Anna
authors.initials: A
authors.lastname: Miodek
authors.affiliation: Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK. ed_regan@hotmail.com.
authors.forename: Edward M
authors.initials: EM
authors.lastname: Regan
authors.affiliation: Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK. n.bhalla@bath.ac.uk.
authors.forename: Nikhil
authors.initials: N
authors.lastname: Bhalla
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, SP4 0JQ, UK. nahopkins@dstl.gov.uk.
authors.forename: Neal A E
authors.initials: NA
authors.lastname: Hopkins
authors.affiliation: Defence Science and Technology Laboratory, Porton Down, Salisbury, SP4 0JQ, UK. sagoodchild@dstl.gov.uk.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Goodchild
authors.affiliation: Department of Electronic and Electrical Engineering, University of Bath, Bath BA2 7AY, UK. p.estrela@bath.ac.uk.
authors.forename: Pedro
authors.initials: P
authors.lastname: Estrela
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry*; D057219:Biofouling / Q000517:prevention & control*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000592:standards; D017097:Electric Impedance; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods; D004566:Electrodes; D000441:Hexanols / Q000737:chemistry; D006801:Humans; D012710:Serum Albumin, Bovine / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013917:Thrombin / Q000032:analysis*
chemical_list: D052157:Aptamers, Nucleotide; D000441:Hexanols; D013438:Sulfhydryl Compounds; D012710:Serum Albumin, Bovine; C036260:1-hexanol; D013917:Thrombin; C501433:1,6-hexanedithiol
keywords: DNA aptamers; Thrombin; antifouling; biosensor; electrochemical detection; screen printed electrodes; self-assembled monolayers