Electronic Supplementary Material
Gold Nanoparticle Mediated Method for Spatially Resolved Deposition of DNA on Nano-gapped Interdigitated Electrodes, and its application to the detection of the Human Papillomavirus
Nor Azizah1, Uda Hashim1, 2, *, Subash C.B. Gopinath1, 3, Sharipah Nadzirah1
1Institute of Nano Electronic Engineering, Universiti Malaysia Perlis, Kangar, Perlis, Malaysia
2School of Microelectronic Engineering, Universiti Malaysia Perlis, Kangar, Perlis, Malaysia
3School of Bioprocess Engineering, Universiti Malaysia Perlis, Arau, Perlis, Malaysia
*Correspondence to Email:
Materials Methods
Optimization of silane layer
APTES concentration
The influence of different concentrations of silane reagent (APTES) and silanization time for producing a stable silane layer for biomolecular immobilization were investigated. To study the influence of APTES concentration on growth and stability of silane layer on silicon substrate, different concentrations of APTES solution were prepared. The solution of different concentrations of APTES was dropped on the IDE surface for 12 h of silanization incubation time. It was aimed to determine the time with the surface has to reach saturation for growing silane layer at room temperature. Silicon substrates were removed from the solution and washed using anhydrous toluene and dried (100◦C) for 1 h. All the above steps were carried out in nitrogen glove box to reduce the effect of moisture on the silanization process.
Silanization time
To study the effect of silanization time on growth and stability, 24 % of APTES were dropped on the IDE surface with different incubation time intervals. The samples were incubated for 120 min at room temperature. The experimental set-up and the conditions are remaining same as mentioned earlier.
Results and discussion
Silane layer optimization
The main objective of this work is to make a thin, stable layer of silane on silicon substrate using APTES solution. A reliable and sensitive DNA biosensor was developed to produce stable silane layer for biomolecular immobilization. Important parameters were explored in these experimental procedures were APTES concentrations and silanization time. The current (A) at 1V of the silane layer was measured for different APTES concentrations and silanization incubation times using current-voltage (I-V) characterization (KEITHLEY, 6487). The I-V measurement is plotted in supplementary fig. 1(a) and (b) for different times of APTES incubation while (c) for different concentrations of APTES kept for 30 min silanization time.
Optimized conditions for growing stable layer of silane using APTES on the silicon substrate were used for biomolecule immobilization. Since the current of APTES monolayer has been reported approximately to be around 5.66775E-9 A, supplementary fig. 2(a) suggests typical IDE working I-V curves after 24% APTES during incubation times. To get a homogeneous layer of silane formation on silicon, in this study, a thickness comparable to the monolayer of silane was achieved with 24% of APTES and silanization time of 30 min. The optimized study revealed that condition with APTES having 24% and 30 minutes incubation time captures more GNP.
Figure S1: Characterization of silane layer: (a) Typical IDE working I-V curves after 24 % APTES during incubation times; and (b) variation of current (A) at 1 V of the silane layer with the increase in silanization time. (c) Characterization of silane layer by variation of current (A) at 1 V of the silane layer with the change in APTES concentrations. Error bars represent the standard deviation of triplicate determinations of three independent repeated experiments (n=3).
1